Composite particle and related methods of manufacture and methods of use

Abstract

There is provided a particle comprising a core and an outer layer, wherein: the outer layer comprises or consists of carbon; the core comprises at least one compound comprising: a transition metal, oxygen, and an alkali metal or an alkaline earth metal; and the composite particle has a surface area of at least 200 metres squared per gram. There is also provided a related material, a related method of making particles, and a related method of using particles.

Description

[0001] P / 91661

[0002] COMPOSITE PARTICLE AND RELATED METHODS OF MANUFACTURE AND METHODS OF USE TECHNICAL FIELD

[0003] The present disclosure relates to a particle, a method of making particles, and a method of using particles.

[0004] BACKGROUND

[0005] An aim of the present disclosure is to provide a new particle, for example a particle for one or both of: adsorbing at least one target component, for example at least one pollutant, from a solution; and acting as a catalyst in the degradation of at least one target component, for example at least one pollutant, in a solution. Another aim of the present disclosure is to provide a method for producing such a particle, the method ideally being cost-effective, scalable, and environmentally friendly. Another aim of the present disclosure is to provide a new method for creating oxide phases with oxygen vacancies. The background of this disclosure and the various aspects of this disclosure are described in the following paragraphs.

[0006] Plastics have been industrially manufactured for many decades and are used in a wide variety of products, some of which are challenging to replace with alternative materials. While plastics have proven to be highly influential in enhancing human life’s comfort, plastic waste poses an increasing challenge due to the nondegradability of the majority of plastics in nature, including predominantly single-use plastic drink bottles. Therefore, upcycling plastic waste into advanced materials with specific applications that outperform available alternatives is a valuable task, offering both economic and environmental benefits.

[0007] This disclosure relates to green, fast, and low-cost methods for upcycling waste plastics, particularly polyethylene terephthalate, into advanced materials that are efficient in the removal of inorganic and organic contaminants from the environment.

[0008] The efficient, fast, and low-cost methods of this disclosure utilise widely available resources, such as TiO2, Fe20s and NaCI, in addition to waste plastics. The resulting products exhibit excellent properties compared to certain other agents, including enhanced adsorption and catalytic degradation performance.

[0009] Aspects of the present disclosure relate to effective adsorbents or catalysts suitable for various applications, including but not limited to selectively separating at least one target component from a solution, and to purification, particularly involving separation processes. In certain embodiments, the separation process comprises the removal of organic or inorganic matter from a liquid, such as water.

[0010] Water pollution is a common issue arising from industrial activities including the textile industry, where the widespread use of synthetic dyes in wastewater poses a significant threat to both the environment and human health, necessitating appropriate treatment. At present, numerous methods are being considered to remove dyes from aqueous environment, including the adsorption, photocatalysis, biological treatment and the chemical

[0011] 1P / 91661

[0012] oxidation. The latter includes the Fenton reaction process, in which the oxidation of ferrous ions (Fe2+) by hydrogen peroxide (H2O2) in an acidic environment is utilized to produce ferric ions (Fe3+) and hydroxyl radicals (■OH), capable of degrading a wide range of organic contaminants:

[0013] Fe2++ H2O2 — > Fe3++ 'OH +OH- (1)

[0014] However, the application of the traditional Fenton process is limited by the necessity of providing a pH value in the narrow range of typically around 3, and the generation of iron-containing sludge that leads to the accumulation of secondary contamination.

[0015] In contrast with traditional Fenton catalysts, Fenton-like catalysts may utilize alternative transition metals such as Cu and Co for activating H2O2 thus degrading organic compounds over a broader pH range. An alternative, low cost and environmentally friendly alternative transitional metal for the Fenton-like degradation of organic contaminants can be titanium, which has not received considerable attention in the literature, due the wide spread application of TO2 in photocatalysis.

[0016] In this context, the current disclosure, for the first time, demonstrates the possibility of converting the commercially available TiO2 into efficient Fenton-like catalysts using green processing methods, and the application of the prepared agent for efficient degradation of organic pollutants.

[0017] It should be considered that in advanced Fenton and Fenton-like oxidation processes, the free radicals obtained by the decomposition of H2O2 typically have a very short lifetime in order of 106-109seconds, limiting their functions to effectively tackle organic contaminants. Moreover, while catalysts with small particles provide benefits in providing an enhanced catalytic kinetics, however, nanostructured particles are susceptible to aggregate to reduce their surface energy, thus reducing their performance and stability in aqueous environment. An effective strategy to mitigate these issues can be based on the involvement of a catalyst carrier that facilitate the electron transfer, improving the catalytic performance of the catalyst. Carbon materials have received a specific attention as efficient catalyst carriers because of their appropriate electronic conductivity, high chemical stability, and environmental friendliness. This interest has led to the development of new oxide / carbon catalyst systems such as Co3O4@CNT, in which the introduction of oxygen vacancies (OVs) into the oxide phase is considered an additional tool for altering the electronic structure of the catalyst, providing active sites to promote the generation of radicals. Such OVs can be formed by various methods including ion doping. The precursor materials and methods used for the preparation of these agents are generally expensive and environmentally challenging, which limits their applications on a large scale.

[0018] TiO2 has widely been used in wastewater treatment because of its special photoinductive properties, chemical and optical stability, non-toxicity and low cost. However, as an adsorbent, TiO2 exhibits low affinity for organic

[0019] 2P / 91661

[0020] pollutants, especially hydrophobic organic substances, resulting in limited potential of TiO2 in removal of organic contaminants in dark condition. Doping can be employed to improve the adsorption capability of TiO2. For instance TO2 nanoparticles can be co-doped with nitrogen and sulphur via calcination, promoting the active sites of TiO2to enhance its dye adsorption capability. However, the adsorption capacity of doped TiC>2 was still limited at 0.054 mg / g for MB.

[0021] While pure TiC>2 has also a poor catalytic activity, the presence of defects may improve its Fenton-like catalytic performance. For example, defect-engineered TiCh-x catalysts can be synthesised by thermal treating of TiCh under hydrogen. This process could introduce OVs and surface Ti3+reaction sites, enabling the activation of H2O2 to produce hydroxyl radicals, in order to degrade RhB at a wide pH working window of 2-9.

[0022] In previous works, the inventor has explored the potential of upcycling waste polyethylene terephthalate (PET) in order to prepare core / shell nanostructures. In these engineered nanostructures, the PET-derived carbon shell is utilized as an efficient adsorbent for the removal of organic dyes from their solutions, while the core part such as CoFe2O4 / Co3Fe7 and Nio 4Fe2 eO4 / (Fe,Ni) can provide the agent with various functionality such as magnetic properties, enabling the facile separation of the exhausted adsorbent from the purified water. This approach provides an economic opportunity for an efficient waste treatment strategy. It should be mentioned that PET, with an annual production of 30 million tons, is mainly used for single-time use, like waste bottles, before being considered as waste. Therefore, the green and low-cost upcycling of such waste is of environmental and economic importance.

[0023] Some aspects of this disclosure, relates to the utilization of commercially available TiO2 material and waste PET to prepare Na4Ti50i2 / Nao23Ti02@carbon (NTC), a bifunctional absorbent and Fenton-like catalyst. This is achieved through a simple and environmentally friendly molten salt treatment method that avoids the use of hazardous chemical reagents.

[0024] In some embodiments, the novel method presented in this disclosure is referred to as "reactive molten salt" method, wherein the molten salt chemically reacts with the oxide reactant to incorporate a metal from the salt into the oxide phase, forming new phases with distinct properties, such as enhanced catalytic performance, compared to the original reactants.

[0025] In some embodiments, the prepared NTC can be used to remove various organic compounds from their solutions in dark, both with and without the presence of H2O2, demonstrating its bifunctional adsorption and Fenton-like catalytic performance. Without being restricted by mechanism, the enhanced catalytic activity of NTC is attributed to a combination of factors, including titanium's ability to alternate between the +3 and +4 oxidation states, the presence of oxygen vacancy sites, and the carbon phase, which collectively promote

[0026] 3P / 91661

[0027] electron transfer and improve catalytic performance. The effects of various parameters such as the dosage of catalyst, concentration of H2O2, pH of the solution, the type of dye species and their concentrations, as well as the temperature were systematically studied. In some embodiments, the application of radical scavengers combined with other characterization techniques such as XPS and EPR indicates that102 radicals are the main reactive oxidative species involved in the Fenton-like catalytic performance of NTC. The inventor proposes NTC as a green dual functional agent for the adsorption of organic and inorganic pollutants, and degradation of organic pollutants.

[0028] Certain aspects of the disclosure suggest that doping NTC with a transition metal enhances the performance of the sample compared to specific other materials.

[0029] In this disclosure, the term "dark" refers to conditions absent of external light irradiation, including ultraviolet (UV), visible, or solar light. This definition is particularly relevant to photocatalysis and adsorption studies, where experiments conducted in the dark serve to isolate non-photochemical processes. The term "dark" is used herein to demonstrate the capability of the disclosed agents to function effectively without reliance on photocatalysis. Accordingly, the ability to operate under dark conditions is an advantageous feature of the agents described, while not precluding their adsorption and catalytic activity under light irradiation.

[0030] In further aspects, the present disclosure relates to core— shell / outer layer particles in which the core comprises a silicon-containing and / or silicon and aluminium-containing material, and the shell, or outer layer, comprises carbon. In some embodiments, the silicon -containing material comprises a silicon oxide, such as SiO or Si02, and in some embodiments, the silicon and aluminium-containing material is an aluminosilicate compound. The shell or outer layer may be derived from the upcycling of waste plastics, including polyethylene terephthalate (PET), using green and scalable processing routes. Such core-shell architectures combine the structural and chemical stability of the inorganic core with the high surface area and surface functionality of the carbon shell, providing effective adsorption performance for the selective removal of target components from liquid media.

[0031] In some aspects, the core-shell particles described herein are suitable for the selective separation of metallic ions in any oxidation state from liquid solutions via adsorption, including metal ions derived from elemental metals or metal-containing compounds. In certain embodiments, such separation may involve the removal of heavy metal ions for purification purposes, or the selective recovery of valuable metal ions, such as rubidium ions (Rb+), in extractive metallurgy applications. Such core-shell architectures combine the structural and chemical stability of the inorganic core with the high surface area and surface functionality of the carbon shell, providing effective adsorption performance for the selective removal of target components from liquid media.

[0032] 4P / 91661

[0033] SUMMARY OF INVENTION

[0034] According to a first aspect of this disclosure, there is provided a particle comprising a core and an outer layer. The outer layer comprises or consists of carbon. The core comprises at least one compound. The at least one compound comprises: (A) a transition metal, (B) oxygen, and (C) one or both of an alkali metal and an alkaline earth metal.

[0035] According to an alternative first aspect of this disclosure, there is provided a particle comprising a core and an outerlayer. The outer layer comprises or consists of carbon. The core comprises atleastone compound. The at least one compound comprises: (A) a semi-metal and (B) oxygen.

[0036] Comments and features below may apply to both the first and alternative first aspect unless stated otherwise.

[0037] Advantageously, the core or at least one compound in the core may exhibit catalytic activity for degrading pollutants, for example through Fenton-like or photocatalytic mechanisms. Advantageously, the outer layer may contribute to this catalytic activity of the core by facilitating electron transfer. Advantageously, the outer layer may provide adsorption capacity for capturing pollutants, for example for capturing pollutants suspended in a suspension.

[0038] Optionally, the particle comprises a plurality of cores, the plurality of cores including the core. Each of the plurality of cores may comprise the at least one compound. References below to “the core” or similar should therefore be taken to be references to “the or each core” wherever possible. Thus, according to the first and alternative first aspect, the particle may comprise at least one core and the outer layer. And the or each core comprises the at least one compound.

[0039] Optionally, the particle is a nanoparticle. Optionally, the particle is a composite particle. Thus, the particle may be referred to as a composite nanoparticle.

[0040] The outer layer may be porous. The outer layer may be more porous than the or each core. The outer layer, for example the outer layer around the or each core, may have a thickness of one or both of: at least 1 nanometre and no more than 10 nanometres. The particle may have a surface area of at least 200 metres squared per gram. Advantageously, this may allow the particle or outer layer to effectively adsorb pollutants.

[0041] Optionally, the particle, for example the or each core or the at least one compound, has multiple, preferably an abundance, of oxygen vacancies. Advantageously, this may allow the particle to effectively adsorb pollutants and to effectively act as a catalyst in the degradation pollutants. In this context, an oxygen vacancy in an oxygen-containing compound, such as the at least one compound, refers to a defect where an oxygen atom is missing from a position where an oxygen atom would be expected based on an atomic or crystal

[0042] 5P / 91661

[0043] structure of the oxygen-containing compound. The defect may be a point defect. The position may be a lattice position such as a regular lattice position. The atomic or crystal structure may be an overall atomic or crystal structure. The atomic or crystal structure may be substantially crystalline. Thus, an oxygen vacancy in an oxygen-containing compound, such as the at least one compound, may refer to a point defect where an oxygen atom is missing from a regular lattice position where an oxygen atom would be expected based on an overall, substantially crystalline, atomic or crystal structure of the oxygen-containing compound. Oxygen vacancies can be detected via electron paramagnetic resonance (EPR) analysis, for example using a Bruker EM-Xnano system (Germany), optionally at a microwave frequency of 9.618865 GHz and optionally at a power of 3.162 mW. The oxygen vacancies may be created by the method according to the third aspect set out below.

[0044] Optionally, the particle is for use as one or both of: an adsorbent to adsorb at least one target component, for example at least one pollutant, from a solution; and a catalyst, such as one or both of a photocatalyst and a Fenton-like catalyst, in the degradation of at least one target component, for example at least one pollutant, in a solution.

[0045] Optionally, the particle has a rod-like shape. Optionally, the particle has a length, a width, and a thickness, wherein the length, the width and the thickness are mutually perpendicular, and wherein one or both of: the length is at least 2, 5 or 10 times the width; and the length is at least 2, 5 or 10 times the thickness. Such relative dimensions may be particularly applicable where the particle has a rod-like shape. Alternatively, the particle may have a substantially semi-spherical or hemispherical shape.

[0046] Optionally, the length is one or both of: at least 2, 5 or 10 microns; and no more than 100 or 50 microns. Optionally, the width is one or both of: at least 10 nanometres; and no more than 1 micron. Optionally, the thickness is one or both of: at least 10 nanometres; and no more than 1 micron. These dimensions may be particularly applicable where the particle has a rod-like shape.

[0047] Optionally, the particle has a surface area of at least 300 or 500 metres squared per gram. Advantageously, this may allow the particle, or specifically the outer layer, to effectively adsorb pollutants. Optionally, the particle has a surface area of no more than 1 ,200, 1 ,000 or 800 metres squared per gram.

[0048] Optionally, the particle has a pore volume of at least 0.2, 0.25 or 0.3 centimetres cubed per gram. Advantageously, this may allow the particle, or specifically the outer layer, to effectively adsorb pollutants.

[0049] Optionally, the particle has a pore volume of no more than 1 or 0.5 centimetres cubed per gram. As mentioned before, according to the first aspect, the at least one compound may comprise one or both of an alkali metal and an alkaline earth metal. It may be preferable that the at least one compound

[0050] 6P / 91661

[0051] comprises the alkali metal regardless of whether the alkaline earth metal is present or not in the at least one compound.

[0052] Preferably, according to the first aspect, the alkali metal is one of: sodium, potassium and lithium. It may be particularly preferable for the alkali metal to be sodium.

[0053] Preferably, according to the first aspect, the alkaline earth metal is one of: calcium, magnesium, barium or strontium.

[0054] Preferably, according to the first aspect, the transition metal is one of: titanium, aluminium, manganate, vanadium or cobalt. It may be particularly preferable for the transition metal to be titanium (Ti).

[0055] Optionally, according to the first aspect, the at least one compound comprises a titanate such as an alkali metal-tantalate, for example sodium titanate, potassium titanate or lithium titanate. Sodium titanate may be preferred. Optionally, the at least one compound comprises at least one sodium titanate of the form NaxTiyOz, where x, y, and z are within the range of 0.1 to 20. Optionally, the at least one compound comprises at least two sodium titanates of different chemical formula. Optionally, the at least one compound comprises one or both of Na4TisOi2 and Nao23Ti02. Optionally, the at least one compound comprises sodium titanate and a most abundant form of the sodium titanate by mass is Na4TisOi2 or Nao 23Ti02. Optionally, the at least one compound is carbon-free. Advantageously, as explored in more detail later, such a core or at least one compound may exhibit catalytic activity for degrading pollutants, for example through Fenton-like or photocatalytic mechanisms.

[0056] Optionally, according to the first aspect, the at least one compound comprises sodium aluminate. Optionally, the at least one compound comprises NaxAlyOzwhere x, y, and z are within the range of 0.1 to 20, for example NaAIO2.

[0057] Optionally, according to the alternative first aspect, the semi-metal is silicon. Advantageously, this may allow manufacture of the particle using silicon dioxide, an abundant resource.

[0058] Optionally, according to the alternative first aspect, the core comprises aluminium, for example wherein the at least one compound comprises aluminium. Optionally, according to the alternative first aspect, the core comprises at least one aluminosilicate, for example wherein the at least one compound comprises the at least one aluminosilicate. Optionally, according to the alternative first aspect, the core is an aluminosilicate core.

[0059] As used herein, the term “aluminosilicate” may refer to a compound comprising a silicon-oxygen and aluminium-oxygen framework. In this framework, aluminium atoms may substitute for silicon atoms within a tetrahedral structure. This may result in a negatively charged framework that is charge-balanced by one or more cations. The at least one aluminosilicate may be represented by the general formula XnAlmSi(m+n)O2(m+n), where “X” represents one or more charge-balancing cations, “m” represents the number of aluminium atoms

[0060] 7P / 91661

[0061] incorporated into the framework, and “n” represents the number of charge-balancing cations. In some embodiments, “m” and “n” are independently integers greater than or equal to 1 and less than or equal to 6. The cation “X” may comprise one or more metal ions, including alkali metals, alkaline earth metals, transition metals, post-transition metals, rare earth metals or combinations thereof. The term “comprises” is used herein in an open-ended sense, such that aluminosilicates may include additional elements, substitutions, defects or impurities, for example those naturally present in or introduced into the structure, without departing from the scope of the disclosure.

[0062] The at least one aluminosilicate may include naturally occurring minerals such as feldspars. In certain embodiments, the at least one aluminosilicate exhibits a nanostructured morphology, with particle sizes in the sub-micrometre or nanometre range, including less than 500 nm, less than 200 nm, or less than 100 nm.

[0063] Optionally, according to the alternative first aspect, the core comprises silicon and at least one additional element. Optionally, according to the alternative first aspect, the core comprises silicon, aluminium and at least one additional element. Optionally, according to the alternative first aspect, the core comprises at least one aluminosilicate and at least one additional element. The at least one additional element mentioned in this paragraph may comprise any one or more of: iron, potassium, and rubidium. Advantageously, such additional elements may naturally be present, and thus no additional step of removing these elements may be required. Also advantageously, such particles may provide desirable adsorption and / or catalytic properties.

[0064] Optionally, according to the alternative first aspect, the at least one compound is substantially free of transition metals, for example wherein the core is substantially free of transition metals.

[0065] Optionally, according to the alternative first aspect, the core is in the form of nanoparticles. Optionally, the outer layer covers at least 50, 80, 90, or 99 percent, or substantially all, surfaces of the or each core. Optionally, the or each core is embedded in the outer layer. Optionally, the or each core is surrounded by the outer layer. The outer layer may be a shell around the or each core. Advantageously, making the outer layer mostly or entirely cover the or each core may improve the ability of the outer layer to effectively adsorb pollutants and contribute to the catalytic activity of the or each core by facilitating electron transfer.

[0066] Optionally, the outer layer comprises nanocrystalline hexagonally oriented carbon domains. Optionally, the outer layer comprises one or both of graphite and graphene. Advantageously, this may allow the outer layer to effectively adsorb pollutants and contribute to the catalytic activity of the or each core by facilitating electron transfer.

[0067] Optionally, the outer layer comprises at least 20, 50, 65 or 80 atomic percent carbon. Optionally, the outer layer comprises no more than 10 or 5 atomic percent of the alkali metal or the alkaline earth metal.

[0068] 8P / 91661

[0069] Optionally, the outer layer comprises no more than 10 or 5 atomic percent of the transition metal. Optionally, the outer layer comprises no more than 30 or 20 atomic percent oxygen. Advantageously, making the outer layer mostly or entirely carbon may allow the outer layer to effectively adsorb pollutants and contribute to the catalytic activity of the or each core by facilitating electron transfer.

[0070] Optionally, the outer layer comprises more carbon per gram than the or each core. Optionally, the outer layer comprises less of the at least one compound per gram than the or each core.

[0071] The particle may be a bifunctional adsorbent and catalyst, for example a bifunctional adsorbent and one or both of a photocatalyst and a Fenton-like catalyst. The particle may be a bifunctional adsorbent and catalyst for adsorbing, and / or acting as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution.

[0072] According to a particularly preferred example of a particle according to the first aspect, the at least one compound comprises or consists of at least one sodium titanate, for example the at least one compound comprises one or both of Na4TisOi2 or Nao 23Ti02. Where the at least one compound comprises or consists of at least one sodium titanate, the particle may be referred to as NTC.

[0073] The particle may be doped. The or each core may be doped. The particle may comprise a dopant. The or each core may comprise a dopant. The dopant may be or comprise a second transition metal. The second transition metal may be different to the transition metal. The second transition metal may be any of: iron (Fe), titanium (Ti), manganese (Mn), zirconium (Zr), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), vanadium (V), cobalt (Co), yttrium (Y), molybdenum (Mo), tungsten (W), niobium (Nb), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), and tantalum (Ta). It may be particularly preferred for the second transition metal to be tungsten (W). The dopant may improve properties of the particles, as explained in more detail later.

[0074] Optionally, according to the first aspect, the transition metal is or comprises iron. Optionally, the core comprises one or more iron-containing compounds selected from iron titanate, iron carbide, and iron oxide. Optionally, according to the first aspect, the core comprises a compound comprising or consisting of Iron (Fe), Titanium (Ti) and Oxygen (0), preferably wherein the at least one compound has magnetic properties. Optionally, according to the first aspect, the core comprises maghemite titanian or titanomagnetite. Advantageously, a particle with a core comprising iron may be relatively low-cost to manufacture and have desirable adsorption and / or catalytic properties. As used herein, maghemite titanian or titanomagnetite refer to compounds comprising or consisting of Iron (Fe), Titanium (Ti) and Oxygen (0), the compounds having

[0075] 9P / 91661

[0076] magnetic properties. Maghemite titanian is used in the XRD card of (Fe2.1sTio.42O4) (01-084-1595) as shown in Fig. 21(a).

[0077] Optionally, the core comprises a carbide phase. Optionally, the carbide phase comprises iron carbide. Advantageously, a particle with a core comprising such a carbide phase may be relatively low-cost to manufacture and have desirable adsorption and / or catalytic properties

[0078] Optionally, the particle exhibits magnetic or magnetically responsive properties. Optionally, the particle exhibits ferromagnetic behaviour, for example soft ferromagnetic behaviour. Advantageously, this may allow easy separation of the particles from a solution after use of the particles to adsorb or degrade the at least one target component or pollutant in the solution. As used herein, materials or particles exhibiting “soft magnetic behaviour” and “soft ferromagnetic behaviour” are those exhibiting a coercivity of below 500 oersted (Oe) and a value of Remanent Magnetization divided by Saturation Magnetization (Mr / Ms) of below 0.3. This may be determined by magnetic hysteresis measurements using a vibrating sample magnetometer (VSM) at 20 °C, and may indicate facile and reversible magnetisation reversal.

[0079] Optionally, according to the first aspect, the alkaline earth metal is calcium or magnesium. Optionally, according to the first aspect, the at least one compound comprises calcium titanate, for example where the alkaline earth metal is calcium and the at least one compound comprises calcium titanate. Optionally, according to the first aspect, the at least one compound comprises magnesium titanate, for example where the alkaline earth metal is magnesium and the at least one compound comprises calcium titanate. Advantageously, such particles may be particularly preferable examples of particles with a core comprising iron as they may be relatively low-cost to manufacture and have desirable adsorption and / or catalytic properties.

[0080] Optionally, the particle has a particle size in the range of 1 to 500 nanometres. Optionally, the particle has a particle size in the range of 2 to 200 nanometres. Optionally, the outer layer has an average thickness of less than 10 nanometres. Optionally, the outer layer has an average thickness of between 2 and 8 nanometres. Advantageously, such sizes and thicknesses may be relatively easy to manufacture whilst providing particles with a suitably high surface area for good adsorption and / or catalytic properties.

[0081] As used herein, the term particle size may refer to a largest particle diameter. The term largest particle diameter may refer to a largest measurement of the particle measured in a direction perpendicular to a largest dimension of the particle. Thus, to obtain the largest particle diameter, one first identifies the largest dimension of the particle. Then, the largest particle diameter is the largest measurement in a direction perpendicular to the largest dimension of the particle. Thus, as an example, for a spherical particle, the largest particle diameter would be equal to the diameter of the particle. As another example, where the particle is substantially rod- 10P / 91661

[0082] shaped with a circular cross-section and a length around 10 times the diameter of the circular cross-section, the largest particle diameter would be the diameter of the circular cross-section. As a final example, where the particle is substantially rod-shaped with a rectangular cross-section and a length more than 10 times any side length of the rectangular cross-section, the largest particle diameter would be the diagonal dimension through the centroid of the rectangular cross-section. The particle size may be determined using microscopic techniques, and is preferably determined by transmission electron microscopy (TEM) or scanning electron microscopy (SEM).

[0083] Optionally, the particle has a BET surface area of at least 500 metres squared per gram. Optionally, the particle has a BET surface area of at least 600 metres squared per gram. Optionally, the particle has an average pore diameter of less than 5 nanometres. Optionally, the average pore diameter is between 2 and 4 nanometres. Optionally, the surface area of the particle is at least two times greater than an average surface area of the reactants used to form the particle, preferably at least two times greater than a greatest surface area of any reactant used to form the particle. Optionally, the surface area of the particle is at least two times and at most ten times greater than an average surface area of the reactants used to form the particle, preferably at least two times and at most ten times greater than a greatest surface area of any reactant used to form the particle. Optionally, the surface area is measured using the Brunauer-Emmett-Teller (BET) method. Advantageously, features of this paragraph may give the particles improved properties for adsorbing, or acting as a catalyst in the degradation of, pollutants in solutions.

[0084] Optionally, the particle exhibits an adsorption capacity of at least 150 milligrams per gram for an organic dye. Optionally, the adsorption capacity is at least 1000 milligrams per gram at alkaline pH.

[0085] According to a second aspect of this disclosure, there is provided a material, for example a composite material, comprising multiple particles according to the first aspect and / or multiple particles according to the alternative first aspect. Features described in relation to the first aspect or the alternative first aspect may be applicable to the second aspect.

[0086] According to an alternative second aspect of this disclosure, there is provided a filtration system, for example a water filtration system, comprising multiple particles according to the first aspect and / or multiple particles according to the alternative first aspect. Features described in relation to the first aspect or the alternative first aspect may be applicable to the alternative second aspect. The water filtration system may be a water filter. The water filtration system may comprise multiple particles according to the first aspect and / or multiple particles according to the alternative first aspect agglomerated, or compacted, or agglomerated and compacted, together.

[0087] 11P / 91661

[0088] According to a third aspect of this disclosure, there is provided a method of making a plurality of particles. The method comprises mixing, to form a mixture, at least: an oxide of a transition metal; a carbon-containing material; and an alkali metal-compound and / or an alkali earth metal-compound. The method then comprises heating the mixture to a first temperature greater than a melting temperature of the carbon-containing material. The first temperature may be greater than a melting temperature of the alkali metal-compound. The first temperature may be greater than a melting temperature of the alkali earth metal-compound.

[0089] According to an alternative third aspect of this disclosure, there is provided a method of making a plurality of particles. The method comprises mixing, to form a mixture, at least: a semi-metal or an oxide of a semi-metal; a carbon-containing material; and an alkali metal-compound and / or an alkali earth metalcompound. The method then comprises heating the mixture to a first temperature greater than a melting temperature of the carbon-containing material. The first temperature may be greater than a melting temperature of the alkali metal-compound. The first temperature may be greater than a melting temperature of the alkali earth metal-compound.

[0090] Comments and features below may apply to both the third and alternative third aspect unless stated otherwise.

[0091] Advantageously, the method may provide a straightforward, scalable, cost-effective, and environmentally friendly way to make the particles. As the skilled person would understand after reading this disclosure, the term “alkali earth metal” and “alkaline earth metal” are used interchangeably herein.

[0092] Where the method is according to the third aspect, each of the plurality of particles may be a particle according to the first aspect. Features described in relation to the first aspect may be applicable to the third aspect. Where the method is according to the alternative third aspect, each of the plurality of particles may be a particle according to the alternative first aspect. Features described in relation to the alternative first aspect may be applicable to the alternative third aspect.

[0093] The method may be a method of making a composite material according to the second aspect. Features described in relation to the second aspect may be applicable to the third aspect or alternative third aspect.

[0094] It may be preferable that the mixture comprises the alkali metal-compound regardless of whether the alkaline earth metal-compound is present or not in the mixture.

[0095] Preferably, the alkali metal of the alkali metal-compound is one of: sodium, potassium and lithium. It may be particularly preferable for the alkali metal to be sodium.

[0096] Preferably, the alkaline earth metal of the alkaline earth metal-compound is one of: calcium, magnesium, barium or strontium.

[0097] 12P / 91661

[0098] Optionally, according to the third aspect, the transition metal of the oxide of the transition metal is titanium, aluminium, manganate, vanadium, zirconium, or cobalt. It may be particularly preferable according to the third aspect that the transition metal is titanium. Optionally, according to the third aspect, the oxide of the transition metal is titanium dioxide.

[0099] Optionally, according to the third aspect, in the step of mixing to form the mixture, the oxide of the transition metal is in the form of a plurality of particles. Advantageously, this may improve yield of particles.

[0100] Optionally, according to the third aspect, the step of mixing to form the mixture is or comprises mixing at least: the oxide of the transition metal; the carbon-containing material; the alkali metal-compound or the alkali earth metal-compound; and a dopant-containing material.

[0101] Optionally, according to the third aspect, in the mixture, a total mass of (A) the oxide of the transition metal, divided by a total combined mass of (B) the carbon-containing material and (C) the alkali-metal compound or the alkaline earth metal-compound, is one or both of: at least 0.005 or 0.01; and no more than 0.25 or 0.15.

[0102] Optionally, according to the third aspect, in the mixture, a total combined mass of (A) the oxide of the transition metal and (D) the dopant-containing material, divided by a total combined mass of (B) the carbon-containing material and (C) the alkali-metal compound or the alkaline earth metal-compound, is one or both of: at least 0.005 or 0.01; and no more than 0.25 or 0.15.

[0103] Optionally, according to the third aspect, a mass of the oxide of the transition metal in the mixture is no more than 3 or 2 times a mass of the dopant-containing material in the mixture. Optionally, a mass of the dopantcontaining material in the mixture is no more than 3 or 2 times a mass of the oxide of the transition metal in the mixture. Optionally, a mass of the oxide of the transition metal in the mixture is no more than 3 or 2 times, and no less than a third or a half of, a mass of the dopant-containing material in the mixture.

[0104] The dopant-containing material may comprise a dopant, for example the dopant described above in relation to the first aspect. All features described above in relation to the dopant of the first aspect may be applicable to the dopant of the dopant-containing material. The dopant-containing material may comprise oxygen. The dopant-containing material may be an oxide, for example an oxide of the dopant. The dopantcontaining material may comprise a second transition metal, for example the second transition metal described above in relation to the first aspect. The dopant may be or comprise the second transition metal. The dopantcontaining material may be or comprise an oxide of the second transition metal. Since the dopant may be the dopant described in relation to the first aspect, the second transition metal may be any of the transition metals listed before in relation to the first aspect, and may preferably be tungsten (W). Also as described before, the

[0105] 13P / 91661

[0106] second transition metal may be different to the transition metal. The dopant may improve properties of the particles, as explained in more detail later.

[0107] Optionally, the carbon-containing material comprises oxygen. Optionally, the carbon-containing material comprises hydrogen.

[0108] Optionally, the carbon-containing material is or comprises a thermoplastic. Advantageously, a thermoplastic may melt when heated and then naturally coat the other ingredients in the mixture.

[0109] Optionally, the carbon-containing material is or comprises polyethylene terephthalate (PET). Advantageously, waste PET is abundant. The method may be considered method of upcycling waste PET, for example into a useful product. Advantageously, the method may thus be environmentally friendly.

[0110] The alkali metal of the first aspect may be the alkali metal of the alkali metal-compound of the third or alternative third aspect. So features described in relation to the alkali metal of the first aspect may be applicable to the alkali metal of the alkali metal-compound of the third or alternative third aspect. The alkaline earth metal of the first aspect may be the alkaline earth metal of the alkaline earth metal-compound of the third or alternative third aspect. So features described in relation to the alkaline earth metal of the first aspect may be applicable to the alkaline earth metal of the alkaline earth metal-compound of the third or alternative third aspect. The transition metal of the first aspect may be the transition metal of the oxide of the transition metal of the third aspect. So features described in relation to the transition metal of the first aspect may be applicable to the transition metal of the oxide of the transition metal of the third aspect.

[0111] Optionally, the alkali metal-compound is an alkali metal-salt. Optionally, the alkaline earth metalcompound is an alkaline earth metal salt. Optionally, the alkali metal-compound is an alkali metal-halide, or the alkaline earth metal-compound is an alkaline earth metal-halide. Optionally, the alkali metal-compound is an alkali metal-chloride, or the alkaline earth metal-compound is an alkaline earth metal-chloride. Optionally, the alkali metal is sodium. Optionally, the alkali metal-compound is sodium chloride.

[0112] Advantageously, such alkali metal-compounds and alkaline earth metal-compounds may be suitable for the method of the third aspect because they can react with the oxide of the transition metal to form at least one compound comprising the transition metal, oxygen, and one or both of the alkali metal and the alkaline earth metal. This at least one compound may form, or be comprised in, each of the plurality of particles made by the method. Carbon, formed for example by carbonisation of the carbon-containing material during the step of heating, may form or be comprised in the outer layer of each of the plurality of particles made by the method.

[0113] Optionally, the mixture may comprise a first alkali metal-compound and a second alkali metal-compound different to the first alkali metal-compound. Features described herein in relation to the alkali metal-compound

[0114] 14P / 91661

[0115] may be applicable to the first alkali metal-compound and the second alkali metal-compound. Optionally, the mixture may comprise a first alkaline earth metal-compound and a second alkaline earth metal-compound different to the first alkaline earth metal-compound. Features described herein in relation to the alkaline earth metal-compound may be applicable to the first alkaline earth metal-compound and the second alkaline earth metal-compound.

[0116] Optionally, according to the third aspect, heating the mixture to the first temperature causes a reaction between: the oxide of the transition metal; the carbon-containing material; and the alkali metal-compound or the alkaline earth metal-compound. This reaction may form at least one compound comprising the transition metal, oxygen, and one or both of the alkali metal and the alkaline earth metal.

[0117] Optionally, the first temperature is at least 250, 500, 650 or 800 degrees Celsius. Advantageously, increasing the first temperature may improve yield of the particles from the method. Optionally, the first temperature is no more than 3000, 2000, 1500, 1200, or 1000 degrees Celsius. Advantageously, ensuring the temperature is not overly high may reduce an energy requirement of the method.

[0118] Optionally, the first temperature is between 250 and 2000 degrees Celsius. Preferably, the first temperature is between 500 and 1500 degrees Celsius. More preferably, the first temperature is between 650 and 1500 degrees Celsius. Even more preferably, the first temperature is between 650 and 1200 degrees Celsius. Even more preferably still, the first temperature is between 800 and 1200 degrees Celsius or between 650 and 1000 degrees Celsius. Most preferably, the first temperature is between 800 and 1000 degrees Celsius.

[0119] The first temperature may be no more than 50 or 30 degrees Celsius above the melting point of the alkali metal-compound or the alkaline earth metal-compound. For example, where the alkali metal-compound is present and is sodium chloride with a melting point of around 801 degrees Celsius, the first temperature may be no more than 851 or 831 degrees Celsius, for example around 820 degrees Celsius. This may result in substantially semi-spherical or hemispherical particles being made.

[0120] The first temperature may be at least 50 or 80 degrees Celsius above the melting point of the alkali metal-compound or the alkaline earth metal-compound. For example, where the alkali metal-compound is present and is sodium chloride with a melting point of around 801 degrees Celsius, the first temperature may be at least 851 or 881 degrees Celsius, for example around 900 degrees Celsius. This may result in substantially rod-like particles being made.

[0121] During the method, the mixture may not exceed the first temperature, or at least may not significantly exceed the first temperature. For example, during the method, the mixture may not exceed 50, 30 or 10 degrees Celsius above the first temperature.

[0122] 15P / 91661

[0123] The first temperature is greater than a melting point of the carbon-containing material. Advantageously, according to the third aspect, this may allow the carbon-containing material to coat the at least one compound formed by the reaction or the precursors to forming the at least one compound by the reaction, as discussed above. The coating may have a thickness of one or both of at least 1 nanometre and no more than 10 nanometres. The melting of the carbon-containing material may therefore result in the or each core being incorporated into, or embedded within, or surrounded by, the carbon-containing material.

[0124] Optionally, the first temperature is greater than a melting point of the alkali metal-compound. Optionally, the first temperature is greater than a melting point of the alkali earth metal-compound. Advantageously, according to the third aspect, this may improve the reaction rate between the oxide of the transition metal and the alkali metal-compound or the alkali earth metal-compound. This may improve yield of the plurality of particles.

[0125] Optionally, the first temperature is less than a melting point of the alkali metal-compound. Optionally, the first temperature is less than a melting point of the alkali earth metal-compound. Advantageously, this may reduce an energy requirement of the method.

[0126] Optionally, according to the third aspect, the first temperature is greater than a melting point of the oxide of the transition metal. Advantageously, this may improve the reaction rate between the oxide of the transition metal and the alkali metal-compound or the alkali earth metal-compound. This may improve yield of the plurality of particles.

[0127] Optionally, according to the third aspect, the first temperature is less than a melting point of the oxide of the transition metal. Advantageously, this may reduce an energy requirement of the method.

[0128] Optionally, the step of heating the mixture to the first temperature is performed at an average heating rate of one or both of: at least 1, 2, 3 degrees C per second; and no more than 50, 20, 10 or 6 degrees C per second. Optionally, the step of heating the mixture to the first temperature is performed at a heating rate of one or both of: at least 1 , 2, 3 degrees C per second; and no more than 50, 20, 10 or 6 degrees C per second.

[0129] Optionally, the step of heating the mixture to the first temperature is performed in an atmosphere comprising oxygen. Optionally, the step of heating the mixture to the first temperature is performed in air, or in an atmosphere comprising air. Advantageously, the presence of oxygen or air would not add significant cost, if any, to the method and the presence of oxygen may help balance the oxygen required to produce a thermodynamically stable compound.

[0130] Optionally, the step of heating the mixture to the first temperature is performed in an atmosphere comprising water, optionally in the form of water vapour. Advantageously, the presence of water would not add

[0131] 161

[0132] P / 91661

[0133] significant cost, if any, to the method and the presence of water may help balance the oxygen required to produce a thermodynamically stable compound.

[0134] It may be particularly preferable for the step of heating the mixture to the first temperature to be performed in an atmosphere comprising both oxygen and moisture for the above reasons.

[0135] Optionally, the step of heating the mixture to the first temperature is performed in an inert atmosphere, for example an inert atmosphere comprising or consisting of at least one inert gas such as argon. Advantageously, this may prevent undesired reactions taking place.

[0136] Optionally, the step of heating the mixture to the first temperature is performed in a reducing atmosphere, for example an atmosphere comprising hydrogen. Advantageously, a reducing atmosphere may prevent oxidation of the carbon phase into gas species and potentially increasing the product yield. Advantageously, a reducing atmosphere may reduce the oxygen level of the carbon phase, by reacting such oxygen with reducing gas, for example to form steam.

[0137] Optionally, after the step of heating the mixture to the first temperature, the method comprises holding the mixture at the first temperature, or within 50 degrees Celsius of the first temperature, for a predetermined period of time, for example one or both of: at least 20 or 40 minutes; and no more than 200 or 100 minutes.

[0138] Optionally, after the step of heating the mixture to the first temperature, the method comprises cooling the mixture, for example to less than 50 degrees Celsius, for example to form cooled products. The cooling may be performed at a cooling rate of one or both of: at least 1 , 2, 3 degrees C per second; and no more than 50, 20, 10 or 6 degrees C per second.

[0139] The method may comprise washing products formed during or following the step of heating the mixture to the first temperature, for example with water or distilled water, for example to form washed products. The washing may take place after cooling.

[0140] The method may comprise vacuum filtration of products formed during or following the step of heating the mixture to the first temperature, for example to form filtered products. The vacuum filtration may take place after one or ideally both of cooling and washing.

[0141] The method may comprise drying products formed during or following the step of heating the mixture to the first temperature, for example to form dried products. The drying may take place after any one, two or ideally all of cooling, washing and vacuum filtration.

[0142] Optionally, the alkali metal-compound or alkaline earth metal-compound comprises a chloride salt. Optionally, the chloride salt is selected from sodium chloride, calcium chloride, and magnesium chloride.

[0143] 1P / 91661

[0144] Advantageously, such salts have been found to be cost-effective in preparing particles with good adsorption and / or catalytic properties.

[0145] Optionally, the method further comprises washing the particles with an aqueous solution, for example to remove residual salt. Optionally, the aqueous solution comprises a dilute acid to remove residual oxide or carbonate species. Optionally, the at least one pollutant comprises an organic dye. Optionally, the organic dye comprises a cationic dye. Optionally, the cationic dye comprises crystal violet. Advantageously, this may be a cost-effective way to remove residual salt.Optionally, according to the alternative third aspect, the semi-metal is silicon. Optionally, according to the alternative third aspect, the oxide of the semi-metal is silicon dioxide.

[0146] Optionally, according to the alternative third aspect, the oxide of the semi-metal comprises aluminium. Optionally, according to the alternative third aspect, the oxide of the semi-metal is an aluminosilicate. Advantageously, such particles have been found to have advantageous properties in adsorbing or acting as a catalyst in the degradation of pollutants in solution.

[0147] Optionally, according to the alternative third aspect, the mixture is substantially free of transition metals. Advantageously, this may help avoid any undesired reactions.

[0148] Optionally, according to the alternative third aspect, the semi-metal or the oxide of the semi-metal is in the form of nanoparticles. Advantageously, this may help to create particles of the desired size.

[0149] Optionally, according to the alternative third aspect, the each of the plurality of particles is a particle according to the alternative first aspect.

[0150] According to a fourth aspect of this disclosure, there is provided a method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution. Each of the particles comprises a core and an outer layer. The outer layer comprises or consists of carbon. The core comprises at least one compound comprising: a transition metal, oxygen, and one or both of an alkali metal and an alkaline earth metal.

[0151] According to an alternative fourth aspect of this disclosure, there is provided a method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution. Each of the particles comprises a core and an outer layer. The outer layer comprises or consists of carbon. The core comprises at least one compound comprising: a semi-metal and oxygen.

[0152] Comments and features below may apply to both the fourth and alternative fourth aspect unless stated otherwise.

[0153] The method of using particles is preferably a method of using particles to adsorb at least one target component, for example at least one pollutant, in a solution. The method of using particles is even more

[0154] 18P / 91661

[0155] preferably a method of using particles to adsorb, and act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution. The particles may act as the catalyst as mentioned under certain conditions, such as the presence of H202, peroxymonosulfate, peroxydisulfate, or other Fentonlike activators that induce Fenton-like catalytic activity, or the presence of light which may induce photocatalysis.

[0156] Where the method of use is according to the fourth aspect, each of the particles may be a particle according to the first aspect. Features described in relation to the first aspect may be applicable to the fourth aspect. The method may be a method of using a composite material according to the second aspect. Features described in relation to the second aspect may be applicable to the fourth aspect. The particles for use in the method according to the fourth aspect may be made by the method according to the third aspect. Features described in relation to the third aspect may be applicable to the fourth aspect.

[0157] Where the method of use is according to the alternative fourth aspect, each of the particles may be a particle according to the alternative first aspect. Features described in relation to the alternative first aspect may be applicable to the alternative fourth aspect. The method may be a method of using a composite material according to the second aspect. Features described in relation to the second aspect may be applicable to the alternative fourth aspect. The particles for use in the method according to the alternative fourth aspect may be made by the method according to the alternative third aspect. Features described in relation to the alternative third aspect may be applicable to the alternative fourth aspect.

[0158] Optionally, the at least one pollutant is or comprises a dye. Optionally, the at least one pollutant is or comprises an organic dye. Optionally, the at least one pollutant is or comprises a cationic dye. Optionally, the at least one pollutant is or comprises an organic, cationic dye such as CV or MG. Optionally, the at least one pollutant is or comprises one or both of CV and MG. The particles may be particularly effective at adsorbing and / or degrading such pollutants.

[0159] Optionally, the solution is an aqueous solution, such as wastewater.

[0160] Optionally, H2O2 is present in the solution. Advantageously, this may increase pollutant degradation efficiency.

[0161] Optionally, the method comprises using the particles as a Fenton-like catalyst in the degradation of at least one target component, for example at least one pollutant, in the solution. Optionally, the method comprises using the particles as a photocatalytic catalyst in the degradation of at least one target component, for example at least one pollutant, in the solution. Optionally, the degradation process involves -OH, -02’, and102 radicals, with102 identified as the dominant oxidative species.

[0162] 19P / 91661

[0163] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a dosage of the particles in the solution is at least 100, 200, 400, 600 or 800 milligrams per litre. Advantageously, this may increase pollutant degradation efficiency.

[0164] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a dosage of the particles in the solution is no more than 5000, 2000, or 1000 milligrams per litre. Such high dosages may be unnecessary.

[0165] Optionally, the method of use comprises combining the plurality of particles, the solution and H2O2. Advantageously, this may increase pollutant degradation efficiency.

[0166] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a dosage of H2O2 in the solution is one or both of: at least 5, 20, 50, 100, 200 or 300 milligrams per litre; and no more than 18300, 14600, 11000, 7300, or 3700 milligrams per litre. Advantageously, this may increase pollutant degradation efficiency.

[0167] Optionally, the method of use comprises combining the plurality of particles and the solution such that a dosage of the at least one target component, for example at least one pollutant, in the solution is no more than 300, 200 or 100 milligrams per litre. Advantageously, this may increase pollutant degradation efficiency.

[0168] Optionally, the particles are stable within a pH range of at least 4 to 9, preferably at least 2 to 13. One advantage of the particles is their ability to function in solutions across a wide pH range. This stability may be attributed to the outer layer, which is thought to be resistant to dissolution and corrosion across a broad pH range, effectively protecting the or each core.

[0169] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a pH of the solution is at least 2, 3, 4, 4.7, or 5.4. Advantageously, this may increase pollutant degradation efficiency.

[0170] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a pH of the solution is no more than 13, 11, 9 or 8. Such a high pH may be unnecessary as it may not significantly further increase pollutant degradation efficiency.

[0171] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, the solution is at a temperature of at least 0, 10, 20, 25, 30, 35 or 40 degrees Celsius. Optionally, during the method of using particles to adsorb,

[0172] 20P / 91661

[0173] and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, the solution is heated, for example to increase a temperature of the solution by at least 5, 10 or 20 degrees Celsius. Advantageously, this may increase pollutant degradation efficiency.

[0174] Optionally, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, the solution is at a temperature of no more than 80, 60 or 50 degrees Celsius. Such high temperatures may require significant energy input without a significant increase in pollutant degradation efficiency.

[0175] Optionally, after using the particles to adsorb the at least one target component, for example at least one pollutant, from the solution, the method comprises separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution.

[0176] Separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution may comprise filtering the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution. Separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution may comprise magnetically separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution. Separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution may comprise a process based on a difference in density between the particles with the adsorbed at least one target component, for example at least one pollutant, and the solution. Separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution may comprise a flotation-based process. Advantageously, such separating steps may be relatively quick, reliable, and cost-effective.

[0177] Optionally, the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution further comprises applying a magnetic field to the solution, or applying a magnetic field to separate the particles from the solution, for example applying a magnetic field to the solution to separate the particles from the solution, preferably wherein the magnetic field is applied after the particles have adsorbed and / or acted as a catalyst in the degradation of the at least one target component, for example at least one pollutant, in the solution. Advantageously, this may be a quick and easy way to separate the particles from the solution.

[0178] Optionally, after using the particles to adsorb the at least one target component, for example at least one pollutant, from the solution, for example after separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution, the method comprises separating the adsorbed

[0179] 21P / 91661

[0180] at least one target component, for example at least one pollutant, from the particles. Separating the adsorbed at least one target component, for example at least one pollutant, from the particles may comprise: desorbing the adsorbed at least one target component, for example at least one pollutant, from the particles; or decomposing the adsorbed at least one target component, for example at least one pollutant.

[0181] Desorbing the adsorbed at least one target component, for example at least one pollutant, from the particles may comprise one or more of: solvent elution; pH adjustment to weaken adsorption interactions; heating the particles and adsorbed at least one target component; competitive desorption using one or more higher-affinity agents; and electrochemical desorption. Advantageously, such desorption may enable efficient recovery of the particles and the at least one target component. Advantageously, this may allow recovery of the adsorbed component, which could be valuable.

[0182] Decomposing the adsorbed at least one target component, for example at least one pollutant, may comprise one or more of: chemical, photocatalytic or electrochemical processes; and heating the particles and adsorbed at least one target component, for example to at least 300 °C, such as to between 300 and 800 °C or between 300 and 600 °C. This heating may take place in air, or in an atmosphere comprising air, in which case it may be preferable that the particles are heated to between 300 and 600 °C. Alternatively, the heating may take place in an inert or reducing atmosphere, in which case it may be preferable that the particles are heated to between 300 and 800 °C. Advantageously, such decomposing may enable efficient recovery of the particles.

[0183] Optionally, after separating the adsorbed at least one target component, for example at least one pollutant, from the particles, the method may comprise re-using the particles in one or more subsequent adsorption processes, for example in the method according to the fourth aspect or alternative fourth aspect. Advantageously, this may minimise waste from the method and may allow an efficient, circular process.

[0184] The invention is defined in the claims. However, below there is provided a non-exhaustive list of nonlimiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0185] Example Ei. A particle comprising a core and an outer layer, wherein:

[0186] the outer layer comprises or consists of carbon;

[0187] the core comprises at least one compound comprising:

[0188] (A) a transition metal, oxygen, and one or both of an alkali metal or an alkaline earth metal; or (B) a semi-metal and oxygen; and

[0189] the particle has a surface area of at least 200 metres squared per gram.

[0190] 22P / 91661

[0191] Example E1. A particle comprising a core and an outer layer, wherein:

[0192] the outer layer comprises or consists of carbon;

[0193] the core comprises at least one compound comprising: a transition metal, oxygen, and one or both of an alkali metal and an alkaline earth metal; and

[0194] the particle has a surface area of at least 200 metres squared per gram.

[0195] Example E2. The particle of Example E1 , wherein the at least one compound has an abundance of surface oxygen vacancies.

[0196] Example E3. The particle according to any preceding Example, wherein the particle is for use as one or both of: an adsorbent to adsorb at least one target component, for example at least one pollutant, from a solution; and a catalyst, such as a photocatalyst or a Fenton-like catalyst, in the degradation of at least one target component, for example at least one pollutant, in a solution.

[0197] Example E4. The particle according to any preceding Example, wherein the particle has a rod-like shape. Example E5. The particle according to any preceding Example, wherein the particle has a length, a width, and a thickness, wherein the length, the width and the thickness are mutually perpendicular, and wherein one or both of: the length is at least 2, 5 or 10 times the width; and the length is at least 2, 5 or 10 times the thickness.

[0198] Example E6. The particle according to Example E5, wherein the length is one or both of: at least 2, 5 or 10 microns; and no more than 100 or 50 microns.

[0199] Example E7. The particle according to Example E5, wherein the length is no more than 100 or 50 microns. Example E8. The particle according to Example E5, wherein the length is both of: at least 2, 5 or 10 microns;

[0200] and no more than 100 or 50 microns.

[0201] Example E9. The particle according to any preceding Example, wherein the particle is a nanoparticle. Example E10. The particle according to any preceding Example, wherein the particle has a surface area per gram of one or both of: at least 300 or 500 metres squared per gram; and

[0202] no more than 1,200, 1,000 or 800 metres squared per gram.

[0203] Example E11. The particle according to any preceding Example, wherein the particle has a pore volume per gram of one or both of: at least 0.2, 0.25 or 0.3 centimetres cubed per gram; and no more than 1 or 0.5 centimetres cubed per gram.

[0204] Example E12. The particle according to any preceding Example, wherein the alkali metal is potassium, lithium or sodium, and / or wherein the alkaline earth metal is calcium, magnesium, barium and strontium.

[0205] 23P / 91661

[0206] Example E13. The particle according to any preceding Example, wherein the transition metal is titanium, aluminium, manganate, vanadium, zirconium or cobalt.

[0207] Example E14. The particle according to any preceding Example, wherein the at least one compound comprises sodium titanate or sodium aluminate.

[0208] Example E15. The particle according to Example E14, wherein the at least one compound comprises one or both of Na4TisOi2 and Nao 23Ti02.

[0209] Example E16. The particle according to any preceding Example, wherein the at least one compound comprises sodium titanate and a most abundant form of the sodium titanate by mass is Na4TisOi2 or Nao23Ti02.

[0210] Example E17. The particle according to any preceding Example, wherein the at least one compound is carbon-free.

[0211] Example E18. The particle according to any preceding Example, wherein the outer layer covers at least 50, 80, 90, or 99 percent, or substantially all, surfaces of the core.

[0212] Example E19. The particle according to any preceding Example, wherein the outer layer comprises nanocrystalline hexagonally oriented carbon domains.

[0213] Example E20. The particle according to any preceding Example, wherein the outer layer comprises one or both of graphite and graphene.

[0214] Example E21. The particle according to any preceding Example, wherein the outer layer comprises at least 20, 50, 65 or 80 atomic percent carbon.

[0215] Example E22. The particle according to any preceding Example, wherein the outer layer comprises no more than 10 or 5 atomic percent of the alkali metal or the alkaline earth metal.

[0216] Example E23. The particle according to any preceding Example, wherein the outer layer comprises no more than 10 or 5 atomic percent of the transition metal.

[0217] Example E24. The particle according to any preceding Example, wherein the outer layer comprises no more than 30 or 20 atomic percent oxygen.

[0218] Example E25. The particle according to any preceding Example, wherein the outer layer comprises more carbon per gram than the core.

[0219] Example E26. The particle according to any preceding Example, wherein the transition metal is or comprises iron.

[0220] Example E27. The particle according to Example E26, wherein the core comprises one or more iron- containing compounds selected from iron titanate, iron carbide, and iron oxide.

[0221] 24P / 91661

[0222] Example E28. The particle according to any of Examples E26 or E27, wherein the at least one compound comprises or consists of Iron (Fe), Titanium (Ti) and Oxygen (0), preferably wherein the at least one compound has magnetic properties, for example wherein the core comprises maghemite titanian or titanomagnetite.

[0223] Example E29. The particle according to any preceding Example, wherein the core comprises a carbide phase.

[0224] Example E30. The particle according to Example E29, wherein the carbide phase comprises iron carbide. Example E31. The particle according to any preceding Example, wherein the particle exhibits magnetic or magnetically responsive properties.

[0225] Example E32. The particle according to Example E31 , wherein the particle exhibits ferromagnetic behaviour, for example soft ferromagnetic behaviour.

[0226] Example E33. The particle according to any preceding Example, wherein the alkaline earth metal is calcium or magnesium.

[0227] Example E34. The particle according to Example E33, wherein the at least one compound comprises calcium titanate, for example where the alkaline earth metal is calcium and the at least one compound comprises calcium titanate.

[0228] Example E35. The particle according to Example E33, wherein the at least one compound comprises magnesium titanate, for example where the alkaline earth metal is magnesium and the at least one compound comprises calcium titanate.

[0229] Example E36. The particle according to any preceding claim, wherein the particle has a particle size of 1 to 500 nanometres.

[0230] Example E37. The particle according to Example E36, wherein the particle has a particle size of 2 to 200 nanometres.

[0231] Example E38. The particle according to any preceding Example, wherein the outer layer has an average thickness of less than 10 nanometres.

[0232] Example E39. The particle according to Example E38, wherein the outer layer has an average thickness of between 2 and 8 nanometres.

[0233] Example E40. The particle according to any preceding Example, wherein the particle has a BET surface area of at least 500 metres squared per gram.

[0234] Example E41. The particle according to any preceding Example, wherein the particle has a surface area of at least 600 metres squared per gram.

[0235] 25P / 91661

[0236] Example E42. The particle according to any preceding Example, wherein the particle has an average pore diameter of less than 5 nanometres.

[0237] Example E43. The particle according to Example E42, wherein the average pore diameter is less than 4 nanometres.

[0238] Example E44. The particle according to any preceding example, wherein the particle has an average pore diameter of at least 1 or 2 nanometres.

[0239] Example E45. The particle according to Example E42, wherein the average pore diameter is between 2 and 4 nanometres.

[0240] Example E46. The particle according to any preceding Example, wherein the surface area of the particle is at least two times greater than an average surface area of the reactants used to form the particle.

[0241] Example E47. The particle according to any preceding Example, wherein the surface area of the particle is at least two times greater than a greatest surface area of any reactant used to form the particle.

[0242] Example E48. The particle according to Example E44, wherein the surface area of the particle is at least two times and at most ten times greater than an average surface area of the reactants used to form the particle. Example E49. The particle according to Example E44, wherein the surface area of the particle is at least two times and at most ten times greater than a greatest surface area of any reactant used to form the particle. Example E50. The particle according to any of Examples E44 to E47, wherein the surface area is measured using the Brunauer-Emmett-Teller (BET) method.

[0243] Example E51. The particle according to Example E3 or any preceding Example when dependent on Example E3, wherein the at least one pollutant comprises an organic dye.

[0244] Example E52. The particle according to Example E51 , wherein the organic dye comprises a cationic dye. Example E53. The particle according to Example E52, wherein the cationic dye comprises crystal violet. Example E54. The particle according to any preceding Example, wherein the particle exhibits an adsorption capacity of at least 150 milligrams per gram for an organic dye.

[0245] Example E55. The particle according to Example E54, wherein the combined adsorption and catalytic dye degradation capacity within 40 min of exposure is at least 400 or 1000 milligrams per gram at alkaline pH. Example E56. The particle according to any preceding Example, wherein the outer layer comprises less of the at least one compound per gram than the core.

[0246] Example E57. The particle according to Example Ei or any preceding example when dependent on Example Ei, wherein the at least one compound comprises the semi-metal and oxygen, preferably wherein the semimetal is silicon.

[0247] 26P / 91661

[0248] Example E58. The particle according to Example E57, wherein the core comprises aluminium, for example wherein the at least one compound comprises aluminium.

[0249] Example E59. The particle according to claim Example E58, wherein the core comprises at least one aluminosilicate, for example wherein the at least one compound comprises the at least one aluminosilicate. Example E60. The particle according to any of Examples E57 to E59, wherein the at least one compound is substantially free of transition metals, for example wherein the core is substantially free of transition metals. Example E61. The particle according to any of Examples E57 to E60, wherein the core is in the form of nanoparticles.

[0250] Example E62. The particle according to any of Examples E57 to E61 , wherein the core is an aluminosilicate core.

[0251] Example E62i. The particle according to any of Examples E57 to E61, wherein the core comprises at least one additional element.

[0252] Example E62ii. The particle according to Example E62i, wherein the at least one additional element comprises any one or more of: iron, potassium, and rubidium.

[0253] Example E63. A composite material comprising a plurality of particles according to any preceding Example. Example E64. A method of producing a plurality of particles, the method comprising:

[0254] mixing, to form a mixture, at least:

[0255] (A) an oxide of a transition metal,

[0256] a carbon-containing material, and

[0257] one or both of an alkali metal-compound or an alkali earth metal-compound; or

[0258] (B) a semi-metal or an oxide of a semi-metal,

[0259] a carbon-containing material, and

[0260] one or both of an alkali metal-compound or an alkali earth metal-compound;

[0261] and then

[0262] heating the mixture to a first temperature, the first temperature being above a melting temperature of the carbon-containing material and above a melting temperature of the alkali metal-compound or the alkali earth metal-compound.

[0263] Example E65. A method of producing a plurality of particles, the method comprising:

[0264] mixing, to form a mixture, at least:

[0265] an oxide of a transition metal;

[0266] a carbon-containing material; and

[0267] 27P / 91661

[0268] an alkali metal-compound or an alkali earth metal-compound, and then

[0269] heating the mixture to a first temperature, the first temperature being above a melting temperature of the carbon-containing material and above a melting temperature of the alkali metal-compound or the alkali earth metal-compound.

[0270] Example E66. A method according to Example E64 or E65, wherein the transition metal is titanium.

[0271] Example E67. A method according to any of Examples E64 to E66, wherein, in the step of mixing to form the mixture, the oxide of the transition metal is in the form of a plurality of particles.

[0272] Example E68. A method according to any of Examples E64 to E67, wherein the carbon-containing material is or comprises a thermoplastic.

[0273] Example E69. A method according to any of Examples E64 to E68, wherein the carbon-containing material is or comprises polyethylene terephthalate (PET).

[0274] Example E70. A method according to any of Examples E64 to E69, wherein the alkali metal-compound is an alkali metal-salt, or the alkaline earth metal-compound is an alkaline earth metal salt.

[0275] Example E71. A method according to any of Examples E64 to E70, wherein the alkali metal-compound is an alkali metal-halide, or the alkaline earth metal-compound is an alkaline earth metal-hal ide.

[0276] Example E72. A method according to any of Examples E64 to E71 , wherein the alkali metal-compound is an alkali metal-chloride such as sodium chloride, or the alkaline earth metal-compound is an alkaline earth metal-chloride such as calcium chloride or magnesium chloride.

[0277] Example E73. A method according to any of Examples E64 to E72, wherein the alkali metal is potassium, lithium or sodium, and / or wherein the alkaline earth metal is calcium, magnesium, barium or strontium, and / or wherein the transition metal is titanium, aluminium, manganate, vanadium, zirconium, or cobalt. Example E74. A method according to any of Examples E64 to E73, wherein the alkali metal-compound is sodium chloride.

[0278] Example E75. A method according to any of Examples E64 to E74, wherein heating the mixture to the first temperature causes a reaction between:

[0279] the oxide of the transition metal; and

[0280] the alkali metal-compound or the alkali earth metal-compound.

[0281] Example E76. A method according to any of Examples E64 to E75, wherein heating the mixture to the first temperature causes a reaction, the reaction being between the oxide of the transition metal and the alkali metal-compound or the alkali earth metal-compound, to form at least one compound, the at least one compound comprising the transition metal, oxygen, and the alkali metal or the alkaline earth metal,.

[0282] 28P / 91661

[0283] Example E77. A method according to any of Examples E64 to E76, wherein the first temperature is less than a melting point of the oxide of the transition metal.

[0284] Example E78. A method according to any of Examples E64 to E77, wherein the first temperature is one or both of: at least 250, 500, 650 or 800 degrees Celsius; and no more than 3000, 2000, 1500, 1200, or 1000 degrees Celsius.

[0285] Example E79. A method according to any of Examples E64 to E78, wherein the first temperature is between 500 and 1500 degrees Celsius.

[0286] Example E80. A method according to any of Examples E64 to E79, wherein the first temperature is between 650 and 1200 degrees Celsius.

[0287] Example E81. A method according to any of Examples E64 to E80, wherein the first temperature is between 800 and 1000 degrees Celsius.

[0288] Example E82. A method according to any of Examples E64 to E81, wherein the step of heating the mixture to the first temperature is performed at an average heating rate of one or both of: at least 1 , 2, 3 degrees C per second; and no more than 50, 20, 10 or 6 degrees C per second.

[0289] Example E83. A method according to any of Examples E64 to E82, wherein after the step of heating the mixture to the first temperature, the method comprises holding the mixture at the first temperature, or within 50 degrees Celsius of the first temperature, for one or both of: at least 20 or 40 minutes; and no more than 200 or 100 minutes.

[0290] Example E84. A method according to any of Examples E64 to E83, wherein after the step of heating the mixture to the first temperature, the method comprises cooling the mixture, for example to less than 50 degrees Celsius, to form a cooled mixture, optionally wherein the cooling is performed at a cooling rate of one or both of: at least 1 , 2, 3 degrees C per second; and no more than 50, 20, 10 or 6 degrees C per second.

[0291] Example E85. The method according to any of Examples E64 to E84, wherein the method further comprises washing the particles with an aqueous solution, for example to remove residual salt, optionally, wherein the aqueous solution comprises an acid such as a dilute acid, for example to remove residual oxide or carbonate species.

[0292] Example E86. A method according to any of Examples E64 to E85, wherein each of the plurality of particles is a particle according to any of Examples E1 to E62.

[0293] Example E87. A method according to example E64, or any of examples E68-74 or E78-86 when dependent on Example E64, wherein the method comprises:

[0294] 29P / 91661

[0295] mixing, to form the mixture, at least:

[0296] the semi-metal or the oxide of the semi-metal,

[0297] the carbon-containing material, and

[0298] one or both of the alkali metal-compound or the alkali earth metal-compound, and then heating the mixture to the first temperature, the first temperature being above the melting temperature of the carbon-containing material and above the melting temperature of the alkali metal-compound or the alkali earth metal-compound.

[0299] Example E88. A method according to example E87, wherein semi-metal is silicon.

[0300] Example E89. The method according to Example E88, wherein the oxide of the semi-metal is silicon dioxide. Example E90. The method according to Example E88, wherein the oxide of the semi-metal comprises aluminium.

[0301] Example E91. The method according to Example E90, wherein the oxide of the semi-metal is aluminosilicate. Example E92. The method according to any of Examples E87 to E91, wherein the mixture is substantially free of transition metals.

[0302] Example E93. The method according to any of Examples E87 to E92, wherein the semi-metal or the oxide of the semi-metal is in the form of nanoparticles.

[0303] Example E94. The method according to any of Examples E87 to E92, wherein each of the plurality of particles is a particle according to any of Examples E57 to E62.

[0304] Example E95. A method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution, each of the particles comprising a core and an outer layer, wherein:

[0305] the outer layer comprises or consists of carbon; and

[0306] the core comprises at least one compound comprising:

[0307] (A) a transition metal, oxygen, and one or both of an alkali metal and an alkaline earth metal;

[0308] or

[0309] (B) a semi-metal and oxygen.

[0310] Example E96. A method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in a solution, each of the particles comprising a core and an outer layer, wherein:

[0311] the outer layer comprises or consists of carbon; and

[0312] 30P / 91661

[0313] the core comprises at least one compound comprising: one or both of an alkali metal and an alkaline earth metal, a transition metal, and oxygen.

[0314] Example E97. A method according to Example E95 or E96, wherein the at least one pollutant is or comprises a dye, preferably an organic dye, more preferably a cationic dye, even more preferably an organic, cationic dye such as CV or MG.

[0315] Example E98. A method according to any of Examples E95 to E97, wherein the solution is an aqueous solution.

[0316] Example E99. A method according to any of Examples E95 to E98, wherein H2O2 is present in the solution. Example E100. A method according to any of Examples E95 to E99, wherein the method comprises using the particle to act as a photocatalyst or a Fenton-like catalyst in the degradation of at least one target component, for example at least one pollutant, in the solution.

[0317] Example E101. A method according to any of Examples E95 to E100, wherein, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a dosage of the particles in the solution is one or both of: at least 100, 200, 400, 600 or 800 milligrams per litre; and no more than 5000, 2000, or 1000 milligrams per litre. Example E102. A method according to any of Examples E95 to E101, wherein the method of use comprises combining the plurality of particles, the solution and H2O2.

[0318] Example E103. A method according to any of Examples E95 to E102, wherein, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, H2O2 is present in the solution, for example a dosage of H2O2 in the solution is one or both of: at least 5, 20, 50, 100, 200 or 300 milligrams per litre; and no more than 18300, 14600, 11000, 7300, or 3700 milligrams per litre.

[0319] Example E104. A method according to any of Examples E95 to E103, wherein the method of use comprises combining the plurality of particles and the solution such that a dosage of the at least one target component, for example at least one pollutant, in the solution is no more than 300, 200 or 100 milligrams per litre. Example E105. A method according to any of Examples E95 to E104, wherein, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, a pH of the solution is one or both of: at least 2, 3, 4, 4.7, or 5.4; and no more than 13, 11, 9 or 8.

[0320] Example E106. A method according to any of Examples E95 to E105, wherein, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example

[0321] 31P / 91661

[0322] at least one pollutant, in the solution, the solution is at a temperature of at least 20, 25, 30, 35 or 40 degrees Celsius.

[0323] Example E107. A method according to any of Examples E95 to E106, wherein, during the method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component, for example at least one pollutant, in the solution, the solution is heated, for example to increase a temperature of the solution by at least 5, 10 or 20 degrees Celsius.

[0324] Example E108. A method according to any of Examples E95 to E107, wherein the method further comprises, after using the particles to adsorb the at least one target component, for example at least one pollutant, from the solution, separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution.

[0325] Example E109. A method according to any of Example E108, wherein separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution comprises one or both of: filtering the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution; and magnetically separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution.

[0326] Example E110. A method according to any of Examples E95 to E107, wherein the method further comprises applying a magnetic field to separate the particles from the solution, for example after the particles have adsorbed and / or acted as a catalyst in the degradation of the at least one target component, for example at least one pollutant, in the solution.

[0327] Example E111. A method according to any of Examples E95 to E107, wherein the method further comprises, after using the particles to adsorb the at least one target component, for example at least one pollutant, from the solution, separating the adsorbed at least one target component, for example at least one pollutant, from the particles, for example by desorbing the adsorbed at least one target component, for example at least one pollutant, from the particles or by decomposing the at least one target component, for example at least one pollutant.

[0328] Example E112. A method according to any of Examples E108 to E109, wherein the method further comprises, after separating the particles with the adsorbed at least one target component, for example at least one pollutant, from the solution, separating the adsorbed at least one target component, for example at least one pollutant, from the particles, for example by desorbing the adsorbed at least one target component, for example at least one pollutant, from the particles or by decomposing the at least one target component, for example at least one pollutant.

[0329] 32P / 91661

[0330] Example E113. A method according to any of Examples E111 to E112, wherein the method further comprises, after desorbing the adsorbed at least one target component, for example at least one pollutant, from the particles, re-using the desorbed particles in one or more subsequent adsorption processes.

[0331] Example E114. A method according to any of Examples E95 to E113, wherein each of the particles is a particle according to any of Examples Ei or E1 to E62.

[0332] Example E115. A method according to any of Examples E95 to E113, wherein the particles are made by a method according to any of Examples E64 to E94.

[0333] Example E116. A method according to Example E95, or any of Examples E97 to E113 when dependent on example E95, wherein:

[0334] the outer layer comprises or consists of carbon; and

[0335] the core comprises at least one compound comprising the semi-metal and oxygen.

[0336] Example E117. A method according to any of Example E116, wherein each of the particles is a particle according to any of Examples E57 to E62.

[0337] Example E118. A method according to any of Examples E116 or E117, wherein the particles are made by a method according to any of Examples E87 to E94.

[0338] Below there is provided a second non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0339] Example Ex 1. A method of preparing a bifunctional adsorbent and Fenton-like catalyst comprising a carbon coating and an inorganic material core, wherein the reactants of the method comprise: a component 1, consisting of a plastic material.

[0340] Example Ex 2. The method of Example Ex 1 , wherein the plastic material is a thermoplastic polymer.

[0341] Example Ex 3. The method of Example Ex 1 or 2, wherein the thermoplastic polymer is polyethylene terephthalate (PET).

[0342] Example Ex 4. The method of any of Examples Ex 1-3, wherein the reactants further comprise: a component 2, consisting of an oxide of a transition metal.

[0343] Example Ex 5. The method of any of Examples Ex 1-4, wherein the reactants comprise: a component 3, consisting of a metallic material comprising a transition metal.

[0344] Example Ex 6. The method of any of Examples Ex 1-5, wherein the reactants further comprise an inorganic salt.

[0345] 33P / 91661

[0346] Example Ex 7. The method of any of Examples Ex 1-6, wherein the reactants are mixed and thermally treated at a temperature in the range of 250 °C to 2000 °C.

[0347] Example Ex 8. The method of any of Examples Ex 1-7, wherein the product of the thermal treatment is washed to prepare the bifunctional adsorbent and Fenton-like catalyst.

[0348] Example Ex 9. The method of any of Examples Ex 1-8, wherein the reactants comprise PET, Ti02, and NaCI, and the bifunctional adsorbent and Fenton-like catalyst comprises a sodium titanate core and a carbon layer. Example Ex 10. The method of any of Examples Ex 1-9, wherein the sodium titanate comprises NaxTiyOz, where x, y, and z are within the range of 0.1 to 20.

[0349] Example Ex 11. The method of any of Examples Ex 1-10, wherein the sodium titanate comprises Na4TisOi2 and Nao23Ti02.

[0350] Example Ex 12. The method of Example Ex 11 , wherein the bifunctional adsorbent and Fenton-like catalyst has a surface area in the range of 10 m2 / g to 1200 m2 / g.

[0351] Example Ex 13. The method of Example 12, wherein the bifunctional adsorbent and Fenton-like catalyst has a surface area in the range of 500 m2 / g to 800 m2 / g.

[0352] Example Ex 14. The method of Example 12, wherein the bifunctional adsorbent and Fenton-like catalyst has a surface area of 621.0 m2 / g.

[0353] Example Ex 15. The method of any of Examples Ex 12-14, wherein the Ti O2 reactant has a surface area in the range of 5 m2 / g to 50 m2 / g.

[0354] Example Ex 16. The method of any of Examples Ex 12-15, wherein the TiC>2 reactant has a surface area of 31.5 m2 / g.

[0355] Example Ex 17. The method of any of Examples Ex 1-16, wherein the bifunctional adsorbent and Fenton-like catalyst surface exhibits abundant oxygen vacancies and nanocrystalline graphene layers derived from waste PET.

[0356] Example Ex 18. The method of any of Examples Ex 1-17, wherein the bifunctional adsorbent and Fenton-like catalyst exhibits adsorption and catalytic activity for removing pollutants from aqueous solutions.

[0357] Example Ex 19. The method of Example Ex 18, wherein the pollutant comprises an organic compound.

[0358] Example Ex 20. A bifunctional adsorbent and Fenton-like catalyst comprising a carbon layer and a core comprising a transition metal.

[0359] Example Ex 21. A bifunctional adsorbent and Fenton-like catalyst comprising a carbon layer and a core comprising a transition metal oxide.

[0360] 34P / 91661

[0361] Example Ex 22. A bifunctional adsorbent and Fenton-like catalyst comprising sodium titanate, which comprises NaxTiy0z, where x, y, and z are within the range of 0.1 to 20.

[0362] Example Ex 23.The bifunctional adsorbent and Fenton-like catalyst of Example Ex 22, comprising: Na4TisOi2 and Nao.23Ti02 as the primary active phases; A carbon phase providing enhanced electron transfer and adsorption capacity; and Oxygen vacancies facilitating H2O2 activation for producing reactive oxidative species. Example Ex 24. A catalyst of any of Examples Ex 1-23, wherein the bifunctional adsorbent exhibits: Fentonlike catalytic activity for degrading organic dyes in the presence of H2O2, achieving degradation efficiency exceeding 99% within 60 minutes; and Effective dye removal across a pH range of 2.0-9.0, overcoming the limitations of traditional Fenton reactions.

[0363] Example Ex 25. A catalyst of any of Examples Ex 1-24, wherein the presence of H2O2 at concentrations as low as 0.01, 0.1, or 0.3 g / L: Increases the reaction rate constant sixfold when the temperature rises from 20 °C to 40 °C; and Enhances combined adsorption and catalytic performance, achieving a degradation rate 3.0 to 6.0 times faster than adsorption alone.

[0364] Example Ex 26. The catalyst of any of Examples Ex 1-25, wherein: It adsorbs and degrades cationic dyes, including crystal violet (CV) and malachite green (MG), with degradation efficiencies exceeding 98%; and The degradation process involves -OH, -O2_, and1O2 radicals, with1O2 identified as the dominant oxidative species. Example Ex 27. A process for upcycling waste PET to produce a carbon-containing bifunctional catalyst, wherein the PET-derived carbon contributes to: Structural stability of the catalyst in aqueous environments; Enhanced adsorption capacity for organic pollutants; and Facilitated electron transfer during Fenton-like catalytic reactions.

[0365] Example Ex 28. The method of any of Examples Ex 1-27, wherein no hazardous chemical reagents are involved, providing a low-cost and environmentally friendly approach for producing advanced materials for pollutant removal.

[0366] Example Ex 29. A method of treating wastewater containing organic dyes using the catalyst of any of Examples Ex 1-28, comprising: Introducing the catalyst into the wastewater; Optionally adding H202to enhance Fentonlike catalytic degradation; and Maintaining the reaction at a temperature between 20 °C and 40 °C, achieving over 99% dye degradation efficiency within 60 minutes.

[0367] Example Ex 30. The catalyst of any of Examples Ex 1-29, wherein its design is optimized based on the presence of oxygen vacancies and PET-derived graphene layers to: Maximize the generation of reactive oxygen species; and Enhance catalytic efficiency under dark conditions without reliance on photonic activation.

[0368] Some Specific Aspects

[0369] 35P / 91661

[0370] Utilizing waste to develop advanced materials for pollutant removal is an innovative and promising strategy for effective environmental management. According to some aspects of the disclosure, a novel bifunctional adsorbent / Fenton-like catalyst, Na4Ti50i2 / Nao23Ti02@carbon (NTC), is prepared using waste polyethylene terephthalate (PET) and commercially available TiC>2 through a simple and low-cost molten salt treatment method. This agent exhibits excellent adsorption and catalytic activity for the removal of organic dyes from aqueous solutions across a wide pH range, due to its high surface area (for example, 621.0 m2 / g) and total pore volume (for example, 0.32 cm3 / g), as well as the presence of abundant oxygen vacancies and graphene layers derived from waste PET. The NTC material is an effective agent for the adsorption and catalytic degradation of organic compounds. For example, the presence of H2O2 at concentrations as low as 0.3 g / L, the degradation efficiency of CV exceeds 99% within 60 minutes. Without being restricted by the mechanism, the enhanced performance of NTC is due to factors, comprising the formation of -OH, -O2- and1O2 radicals as the key reactive species, with1O2 as the major oxidative radical. In some specific embodiments disclosure, through the utilization of NTC, the dye removal reaction rate constant increases by a factor of six to 9.48 x 102min1upon increasing temperature from 20 to 40 °C. In some embodiments, in the absence of H2O2, NTC exhibits a high adsorption performance for organic and inorganic mattery greater than certain other materials, including the initial TiO2. In one embodiment, the CV adsorption capacity of NTC is 165.8 mg / g, greater than that of TiO2 (13.2 mg / g). In some embodiments, in the presence of low concentrations of H2O2, the rate of combined adsorption and Fenton-like reaction of NTC is greater than the adsorption alone of NTC. In one embodiment, the combined adsorption and Fenton-like catalytic performance of NTC is 3.5 to 6.6 times faster than adsorption alone, with total activation energies of 38.3 and 51.0 kJ mol-1, respectively. In some embodiment’s, NTC effectively removes organic and inorganic pollutes from water resources. In one specific embodiments, the NTC effectively removes cationic dyes from water resources, leveraging its negatively charged surface to preferentially adsorb such dye species.

[0371] Some Other Aspects

[0372] The combination of adsorption and Fenton-like reactions provides a feasible method for removing hazardous inorganic and organic compounds from water. Certain embodiments of the disclosure pertain to the preparation of bifunctional adsorbents and Fenton-like catalysts, such as NTC, wherein the NTC contains a doping agent. In some embodiments, the doping agent is a transition metal, which may include iron (Fe), titanium (Ti), manganese (Mn), zirconium (Zr), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), vanadium (V), cobalt (Co), yttrium (Y), molybdenum (Mo), tungsten (W), niobium (Nb), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), and tantalum (Ta).

[0373] 36P / 91661

[0374] In certain specific embodiments, the doping agent is tungsten, and the W-doped-Na4Ti50i2 / Nao23Ti02-carbon (W-doped-NTC) comprises tungsten doped sodium titanates incorporated into or encapsulated by carbon. The W-doped-NTC exhibits high surface area values, greater than certain other materials, in the range of 400 m2 / g to 1000 m2 / g, and contains abundant oxygen vacancies.

[0375] In some embodiments, a compound (A) is formed comprising a transition metal (B) doped in a compound (C). In some embodiments, the compound (C) comprises a transition metal (D), an alkali or alkali-earth metal (E), and oxygen, encapsulated or incorporated in carbon (F).

[0376] In some embodiments, the compound (A) is formed by thermally treating mechanically treated oxide (F) of the doping transition metal (B) and oxide (G) of the transition metal (D) in the presence of compound (H), which is an alkali or alkali-earth metal (E) compound, and precursor (I) of carbon (F).

[0377] In some specific embodiments, the thermal treatment is performed at a temperature sufficiently above the melting point of carbon precursor (I) and compound (H). During this process, compound (H) reacts with transition metal oxide (G) to form compound (C). In some embodiments, the transition metal (B) is doped into the compound (C) to make the compound (A).

[0378] In some embodiments, the thermal treatment is preferably conducted within a temperature range of 250°C to 2000°C. In some specific embodiments, the thermal treatment is preferentially performed in air, although alternative atmospheres, such as inert atmosphere, nitrogen, or reducing atmospheres, can also be used. In a specific embodiment, the W-doped-NTC is synthesized by thermally treating mechanically treated TiCh and WO3 in the presence of NaCI at various temperatures, such as 820 °C and 900 °C. The sodium titanates involved in the NTC primarily comprise semi-spherical sodium titanate phases in the sample prepared at 820 °C and rod-like sodium titanate phases in the sample prepared at 900 °C. The resulting W-doped-NTC demonstrates enhanced adsorption and Fenton-like performance compared to certain other materials. In some embodiments doping of NTC with a transition metal, such as tungsten enhances the adsorption properties and Fenton-like oxidation capabilities of the NTC for the removal of organic compounds from their solutions.

[0379] In some embodiments, NTC samples and doped-NTC samples exhibit enhanced adsorption and Fenton-like degradation performance for organic molecules across a wide pH range, such as pH 1-14, pH 2-12, pH 2-10, pH 2-9, or pH 4-9, demonstrating their excellent performance under harsh environmental conditions.

[0380] Organic Matter

[0381] Aspects of the present disclosure relate to effective adsorbents or catalysts suitable for various applications, including but not limited to purification, particularly involving separation processes. In certain embodiments, the

[0382] 37P / 91661

[0383] separation process comprises the removal of at least one target component, for example at least one pollutant,, as mentioned previously, such as organic or inorganic matter, from a solution or a liquid such as water.

[0384] In certain embodiments of the disclosure, the organic matter comprises natural organic matter such as humic and fulvic acids derived from decaying plant and microbial material, as well as proteins, lipids, and carbohydrates released from biological activity in water bodies.

[0385] In certain embodiments of the disclosure, the organic matter comprises industrial organic pollutants such as petroleum hydrocarbons (including oil spills, fuel residues, and benzene, toluene, ethylbenzene and xylene), and volatile organic compounds such as chloroform, trichloroethylene, and perchloroethylene.

[0386] In some embodiments, organic dyes are organic synthetic or natural compounds that can absorb light in the visible spectrum and impart colour to a substrate, such as textiles, paper, plastics, or biological tissues. These dyes typically contain chromophores (light-absorbing groups) and auxochromes (functional groups that enhance solubility and dyeing properties).

[0387] In some embodiments, the organic matter comprises cationic organic dyes, also known as basic dyes, which are positively charged colorants commonly used in textile dyeing, biological staining, and wastewater treatment studies. Examples include Methylene Blue (MB), Crystal Violet (CV), Rhodamine B (RhB), Safranin 0, Malachite Green (MG), Basic Fuchsin, Diazahemicyanine, Triarylmethine, Toluidine Blue (TB), Gentian Violet (GV), Neutral Red (NR), Basic Red, and Nile Blue. These cationic dyes are widely used in applications such as textile dyeing, particularly for dyeing acrylic fibres, where they form ionic bonds with the anionic sites in the fibres, resulting in brilliant shades. Other applications include printing for packaging and advertising materials, owing to their high colour strength and transparency.

[0388] In some embodiments, the organic matter comprises anionic dyes, such as C.l. Direct Yellow 86, C.l. Direct Red 254, C.l. Direct Blue 199, Indigo Carmine (IC), Methyl Orange (MO), Coriacide Bordeaux 3B, Derma Blue R67, Coriacide Brown 3J, Acid Green 25, Acid Red 1, Acid Blue 324, C.l. Direct Red 224 (DR 224), C.l. Acid Black 172 (AB 172), Congo Red, Reactive Red 120, Reactive Red 141 (RR141), Acid Yellow 99.

[0389] In certain embodiments of the disclosure, the organic matter comprises polycyclic aromatic hydrocarbons produced from fossil fuel combustion and industrial runoff, along with agricultural contaminants such as pesticides and herbicides, including glyphosate, atrazine, and organochlorines, entering water through agricultural runoff, along with fertilizer residues containing nitrogenous organic compounds that contribute to eutrophication.

[0390] In certain embodiments of the disclosure, the organic matter comprises pharmaceutical and personal care products, including antibiotics, hormones, and painkillers such as ibuprofen, acetaminophen, and estrogenic

[0391] 38P / 91661

[0392] compounds, as well as cosmetics and surfactants found in detergents and personal care products, including parabens and phthalates.

[0393] In certain embodiments of the disclosure, the organic matter comprises microbial and biological contaminants, such as bacterial and viral metabolites, including endotoxins and mycotoxins, and algal toxins from cyanobacteria blooms, such as microcystins and anatoxins.

[0394] In certain embodiments of the disclosure, the organic matter comprises emerging organic pollutants such as microplastics, nanoplastics, and contaminants from plastic degradation, along with endocrine-disrupting compounds affecting hormone functions, including bisphenol A and phthalates.

[0395] In specific embodiments, the organic matter comprises of organic pollutants which are often removed from water using advanced treatment methods such as Fenton-like catalysis, adsorption, photocatalysis, and membrane filtration to ensure the water is clean and safe.

[0396] In specific embodiments, the inorganic matter comprises of heavy metal ions including ions of lead, for instance originated from pipes, batteries, and industrial waste; mercury, released from mining, coal combustion, and industrial processes; bioaccumulates in aquatic life; cadmium from batteries, fertilizers, and industrial wastewater; arsenic, which can be naturally occurring in groundwater; also from mining and pesticides; chromium, for example from electroplating, tanning, and industrial waste.

[0397] Inorganic Matter

[0398] Aspects of the present disclosure relate to effective adsorbents or catalysts suitable for various applications, including but not limited to purification, particularly involving separation processes. In certain embodiments, the separation process comprises the removal of at least one target component, for example at least one pollutant,, as mentioned previously, such as organic or inorganic matter from a liquid, such as water. In specific embodiments, the inorganic matter comprises of nitrate and nitrite (N03_, N02”) from agricultural fertilizers, livestock waste, and wastewater discharge.

[0399] In specific embodiments, the inorganic matter comprises of phosphates (P043-), originating, for example, from fertilizers, detergents, and sewage.

[0400] In specific embodiments, the inorganic matter comprises of ammonia (NH3) and ammonium (NH4+), originating from agricultural runoff, sewage, and industrial waste.

[0401] In specific embodiments, the inorganic matter comprises of fluoride (F"), for example naturally occurring or from industrial sources (e.g., aluminium processing).

[0402] In specific embodiments, the inorganic matter comprises of sulfates (S042-) and sulfides (S2-), originating, for example from mining, industrial discharges, and natural sources.

[0403] 39P / 91661

[0404] In specific embodiments, the inorganic matter comprises of chlorides (Cl-) and salinity, originating, for example, from seawater intrusion, road salts, and industrial discharge.

[0405] In specific embodiments, the inorganic matter comprises of radioactive elements, comprising uranium, radium and radon.

[0406] In specific embodiments, the inorganic matter comprises of suspended and dissolved solids or cyanide (CN“).

[0407] Some specific methods

[0408] In some embodiments of the disclosure, the method for preparing the adsorbent / catalyst comprises the following steps:

[0409] Step (1): A mixture is prepared by combining a salt or a blend of salts, a carbon precursor, and a mineral. As used herein, in this context or similar contexts, the salt may refer to the alkali metal-compound or the alkaline earth metal-compound of the second aspect described earlier. As used herein, in this context or similar contexts, the carbon precursor may refer to the carbon-containing material of the second aspect described earlier. As used herein, in this context or similar contexts, the mineral may refer to the oxide of the transition metal of the second aspect described earlier. In some embodiments, the salt is an alkali or alkali-metal halide, with a melting temperature in the range of 250°C to 1500°C. In some embodiments, the carbon precursor is an organic material, which can be a polymer. In some embodiments, the carbon precursor is a thermoplastic polymer, such as polyethylene terephthalate (PET). In some embodiments, the mineral comprises an oxide phase.

[0410] Step (2): The system, comprising the aforementioned components, is heated above the melting temperature of both the polymer and the salt. During this process, at least one metal and alkali metal from the salt is incorporated into the mineral, forming a new compound with oxygen vacancies, while the carbon precursor is converted into carbon that covers the new compound.

[0411] Step (3): The product obtained from Step (2) is washed to remove excess salt, resulting in the preparation of the adsorbent / catalyst.

[0412] The final product exhibits catalytic activity for the decomposition of organic pollutants through Fenton-like and / or photocatalytic mechanisms, while the carbon phase provides adsorption capacity for capturing organic and / or inorganic pollutants from their suspensions in a liquid. Additionally, the carbon phase contributes to the catalytic activity of the core by facilitating electron transfer.

[0413] Some Other Specific Methods

[0414] Specific embodiments of the present disclosure relate to the preparation of NaxTiyOz, wherein x, y and z are each independently within the range of 0.1 to 20. In certain embodiments, the NaxTiyOzis a thermodynamically stable Na-Ti-0 ternary phase. In other embodiments, the NaxTiyOzmay have specific formulas, such as

[0415] 40P / 91661

[0416] Na2TinO2n+i or Na2O(TiO2)n. In further embodiments, the NaxTiyOzmay have alternative specific formulas, including Na4TinO2n+2 or (Na2O)2(TiO2)n.

[0417] Examples of such compounds include Na2Ti3O?, Na2TieOi3, Na4TisOi2, Na2Ti20s, and Na2Ti70is. In specific embodiments, the NaxTiyOzmay be used as an electrode material in a battery, such as an anode in a sodium-ion battery.

[0418] In certain embodiments, the NaxTiyOzis formed by reacting a titanium-containing phase with a sodium-containing phase. In some embodiments, the titanium-containing phase comprises titanium oxide, such as TiC>2. In other embodiments, the sodium-containing phase comprises a sodium salt, such as NaCI.

[0419] In particular embodiments, the preparation of NaxTiyOzinvolves mixing the titanium-containing phase with the sodium-containing phase, followed by heating the mixture to a temperature sufficient to cause the reaction of these phases to form NaxTiyOz. In some embodiments, this heating step is performed in air.

[0420] In some embodiments, heating may be conducted using a resistance furnace, an induction furnace, or a microwave furnace. In specific embodiments, the mixture is heated to a temperature of at least 300°C, at least 500°C, at least 700°C, at least 820°C, and up to 1500°C, or alternatively, 1300°C or 1000°C. The heating rate to the maximum temperature can range from 1°C / min to 100°C / min. The dwell time at the maximum temperature can range from 1 second to one week, and preferably from 1 second to one hour.

[0421] In certain embodiments, the presence of oxygen or moisture is preferred to facilitate the formation of NaxTiyOz. Without being bound by theory, one possible reaction mechanism for the formation of a specific compound is outlined as follows:

[0422] 3TiO2+ 2NaCI + H20 (g) = Na2Ti3O7+ 2HCI (g) (1 a)

[0423] 6TiO2+ 4NaCI + 02(g) = 2Na2Ti3O7+ 2CI2(g) (1 b)

[0424] In some embodiments, this reaction pathway may be utilized by a skilled person to determine the appropriate amounts of reactants for the fabrication of various NaxTiyOzcompounds. In some embodiments, the fabrication process is rapid and efficient, with minimal energy consumption.

[0425] Novel Properties and Advantages of the Disclosed Water Treatment Materials

[0426] Certain materials prepared in accordance with the methods disclosed herein exhibit practical advantages over certain other materials utilized in water treatment applications. These advantages include, but are not limited to, the following:

[0427] (a) Certain materials prepared according to the disclosed methods are capable of removing organic and / or inorganic substances from the environment across a broad pH range of approximately 2 to 13. Without being bound by theory, this advantage is attributed to the presence of a stable and corrosion-resistant carbon phase

[0428] 41P / 91661

[0429] that protects the core catalyst. This feature expands the applicability of certain Fenton-like catalysts, which are conventionally believed to exhibit activity at an environmental pH of approximately 3.0.

[0430] (b) Certain materials disclosed herein are preferably free from metals, or contain only minimal amounts (e.g., less than 1%) of metals, with densities exceeding 5 g / cm3, such as Fe, Ni, Co, and Cu, which are commonly used in certain other Fenton-like catalysts. As a result, certain disclosed materials are advantageously lighter and more cost-effective than such catalysts, allowing them to remain suspended in the reaction medium rather than sink due to higher density. This ability to stay suspended in the medium is practically advantageous, as it enhances both catalytic and adsorption performance. Furthermore, since metals such as Fe, Ni, Co, and Cu are widely used in various industrial applications, utilizing catalysts free from these elements helps reduce the demand for their extraction, processing and / or recycling.

[0431] (c) Certain materials prepared in accordance with the present disclosure exhibit minimal agglomeration in liquid media due to the presence of a stable and corrosion-resistant carbon coating on the core catalyst. This characteristic renders the disclosed materials superior to certain other catalysts that tend to agglomerate, thereby diminishing their effectiveness.

[0432] (d) In certain embodiments, the catalyst of the disclosed materials is encapsulated or surrounded by carbon, wherein the carbon also serves as a catalyst carrier. This configuration enhances catalyst performance by facilitating electron transfer.

[0433] (e) In some embodiments, the catalyst core of the disclosed materials is engineered to contain oxygen vacancies during the production process, wherein the presence of oxygen vacancies enhances the catalytic performance of the material.

[0434] (f) The disclosed materials are capable of adsorbing organic and / or inorganic pollutants from the environment and decomposing organic pollutants under both light irradiation and, advantageously, in dark conditions (i.e., in the absence of or under minimal light irradiation). The catalytic activity of these materials can be activated with a minimal concentration of a supporting agent, such as H2O2, in concentrations as low as 0.1, 0.2, or 0.3 g / L. (g) Certain materials prepared in accordance with the present disclosure are produced without the use of acids, bases, or other potentially hazardous substances. Additionally, the disclosed methods utilize waste materials, such as waste plastics, thereby contributing to waste valorization and supporting environmental efforts to reduce the plastic waste burden.

[0435] The combination of the aforementioned advantages positions certain materials prepared in accordance with this disclosure as green and environmentally friendly agents for the removal of pollutants from various environments under both light and dark conditions, with high efficiency. In certain embodiments, the disclosed

[0436] 42P / 91661

[0437] materials exhibit a removal performance of approximately 245.9 mg of a pollutant, such as crystal violet (CV) dye, per gram of material within an exposure duration of 180 minutes.

[0438] BRIEF LIST OF FIGURES

[0439] Examples of the invention or helpful for understanding the invention will now be further described with reference to the figures briefly explained below.

[0440] Figure 1 shows: A schematic illustration of the method employed for preparation of bi-functional absorbent / Fenton-like catalyst called NTC.

[0441] Figure 2 shows: X-ray diffraction patterns of (a) initial TiC>2 and (b) Na4TisOi2 / Nao 23TiO2@C. The standard ICDD patterns are also shown for comparison. Raman spectrum of (c) the initial TiO2 and (d) NTC. N2 adsorption-desorption isotherms of (e) Na4TisOi2 / Nao 23TiO2@C and (f) TiC>2. Pore size distribution of (g) Na4Ti50i2 / Nao 23TiO2@C and (f) TiC>2. (i) EPR spectra of the initial TiC>2 and NTC. (I) Values of Zeta potential of NTC at various pH of 4.0, 7.0 and 9.0.

[0442] Figure S1 shows: SEM micrographs of (a) TO2 initial materials, and (b and c) Na4Ti50i2 / Nao23Ti02@carbon product, (d) EDS elemental analysis recorded on SEM micrograph of (c). (e) EDS map analysis of Na4Ti50i2 / Nao23Ti02@carbon.

[0443] Figure 3 shows: (a and b) SEM and (c and f) TEM micrographs of Na4Ti50i2 / Nao23Ti02@carbon. (d-g) FFT patterns recorded on areas highlighted in the micrographs, (h) High-magnification section of the edge area in (f) showing the presence of a carbon layer with the interlayer spacing of 0.33 nm corresponding to (002) crystalline planes of graphitic carbon.

[0444] Figure S2 shows: TEM micrograph of NTC: (a and b) Low magnification micrograph, (c) HRTEM micrograph recorded on rod-like particles (d) show the FFT analysis recorded on the area indicated by yellow rectangles in the corresponding TEM micrographs.

[0445] Figure 4shows: XPS spectra of TiO2: (a) survey, (b) O 1s and (c)Ti 2p. XPS spectra of NTC: (d) survey, I C 1s, (f) O 1s, (g) Na 1s and (h) Ti 2p.

[0446] Figure 5 shows: (a) CV removal in the presence of various materials in dark, (b) The corresponding first-order reaction kinetic model (NTC: 400 mg / L; CV concentration: 100 mg / L; 7.3 g / L H2O2

[0447] Figure 6 shows: the effect of various parameters on the Fenton-like degradation of CV by NTC. (a) Effect of Catalyst dosage (CV concentration: 100 mg / L, H2O2 concentration: 7.3 g / L). (b) Effect of H2O2 dosage (NTC: 800 mg / L, CV concentration: 100 mg / L). (c) Effect of initial CV concentration (NTC: 800 mg / L, H2O2 concentration: 0.3 g / L). (d) Effect of initial pH (NTC: 800 mg / L, CV concentration: 100 mg / L; H2O2 concentration: 0.3 g / L). (e) Effect of solution temperature (NTC: 600 mg / L; CV concentration: 100 mg / L; H2O2 concentration:

[0448] 43P / 91661

[0449] 7.3 g / L). (f): Effect of radical trapping (NTC: 800 mg / L; CV concentration: 100 mg / L; H2O2 concentration: 0.3 g / L).

[0450] Figure 7 shows: (a) The first-order reaction kinetic model and (b) the activation energy of the CV-NTC system in absence of H2O2 considering the adsorption as the sole mechanism involved in the dye removal, (c) The first-order reaction kinetic model and (d) the activation energy of the CV-NTC system in presence of H2O2 considering the adsorption / Fenton-like degradation as the mixed mechanism involved in the dye removal.

[0451] Figure 8 shows: Proposed mechanism involved in CV removal using NTC.

[0452] Figure 9 shows: The Ct / Co vs time for various dyes (a) without and (b) with the presence of H2O2 (0.3 mg / L). NTC dosage: 800 mg / L; CV:100 mg / L; MO: 100 mg / L; MG: 100 mg / L.

[0453] Figure 10 shows: Schematic illustration of the method employed for preparation of W-doped NTC samples.

[0454] Figure 11 shows: XRD patterns of the equal-mass mixture of TiO2+WOs and the samples obtained after 5 h, 10 h, 15 h and 20 h ball milling.

[0455] Figure 12 shows: (a) XRD patterns, and (b) Raman spectra of the W-doped-NTC820-3.2 and W-doped-NTC900-3.2. The standard ICDD patterns are also shown in (a).

[0456] Figure 13 shows: (a,b) SEM micrograph and (c) the elemental EDS map analysis of W-doped-NTC820-3.2. (d) SEM micrograph of W-doped-NTC900-3.2. (i, ii) EDS elemental analysis recorded on SEM micrograph of (d).

[0457] Figure 14 shows: (a,b) TEM and (c-d) HRTEM micrographs of W-doped-NTC820-3.2. (e) N2 adsorptiondesorption isotherms and (f) the pore size distribution of W-doped-NTC820-3.2 and W-doped-NTC900-3.2.

[0458] Figure 15 shows: (a) XPS survey, and the Ti 2p and 01s high-resolution spectra of O2 (b) XPS survey, and the Ti 2p, O 1s, C 1s, W 4f and Na 1s high resolution spectra of W-doped-NTC820-3.2. (c) XPS survey, and the Ti 2p, O 1s, C 1s, W 4f and Na 1s high resolution spectra of W-doped-NTC900-3.2.

[0459] Figure 16 shows: (a) Adsorption and Fenton-like performance of NTC820 and W-doped-NTC-3.2 samples and (b) the corresponding first-order reaction kinetic model (Adsorption assay condition: 40 mg adsorbent, 100 mL CV with 100 mg / L concentration, Fenton-like assay: 40 mg / L catalyst, 100 mL CV with 100 mg / L concentration, H2O2 dosage: 7.3 g / L). (c-f) Influences of various parameters on adsorption performance of W-doped-NTC820-3.2: (c) the W-doped-NTC820-3.2 dosage of 40, 50, 60, 70 and 80 mg / L; CV concentration: 100 mg / L); (d) initial concentration of CV in the solution at the W-doped-NTC820-3.2 dosage of 70 mg / L; CV concentration: 100, 125 and 150 mg / L; (e) the value of pH at W-doped-NTC820-3.2 dosage of 70 mg / L, CV concentration of 125 mg / L, and pH value of 4.0, 5.37.0 and 9.0; (f) the effect of solution temperature

[0460] 44P / 91661

[0461] at W-doped-NTC820-3.2 dosage of 70 mg / L, CV concentration of 125 mg / L, and temperature of 23, 30, 35, 40 and 45 °C. (g) The natural logarithm of Co / Ct values shown in (f). (h) ln(K vs. 1 / T analysing the temperature dependence of the adsorption kinetics, (i) EPR spectra of W-doped-NTC820-3.2 and W-doped-NTC900-3.2.

[0462] Figure 17 shows: (a) XRD patterns of various W-doped-NTC820 samples obtained using varying amounts TO2 and WO3 (0.5 to 4 g) in combination of 30 g PET. (b) The CV removal performances of the samples at various exposure time using various adsorbent / catalyst samples with dosage of 50 mg, at the CV concentration of 100 mg / L, and the H2O2 dosage of 3.7 g / L.

[0463] Figure 18 shows: Effects of various parameters on the CV removal performance of W-doped-NTC820-3.2. (a) Effect of agent dosage; CV concentration: 100 mg / L, H2O2 dosage: 7.3 g / L. (b) Effect of H2O2 dosage; agent dosage: 70 mg / L, CV concentration: 100 mg / L. (c) Effect of initial CV concentration; agent dosage: 70 mg / L, H202dosage: 0.3 g / L. (d) Effect of initial pH; agent dosage: 70 mg / L, CV concentration: 100 mg / L, H202dosage: 0.3 g / L. (e) Effect of solution temperature; agent concentration: 40 mg / L, CV concentration: 100 mg / L, H202dosage: 7.3 g / L. (f) Radical trapping experiments; agent dosage: 70 mg / L, CV concentration: 100 mg / L, H202dosage: 0.3 g / L. (g) First-order reaction kinetic model, (h) Variations of In (K (reaction rate constant) with 1 / T (1 / K), used to determine the activation energy of the agent / H202system for dye removal, (i) Zeta potential values of the agent at different pH levels.

[0464] Figure 19 shows: EPR analyses exhibiting the g-values and peak intensities for (a) W-doped-NTC820 and (b) W-doped-NTC900.

[0465] Figure 20 shows: EPR analysis exhibiting the g-values and peak intensities for NTC.

[0466] Figure 21 shows: Characterisation of NFTC: (a) XRD, (b and c) VSM, and (d and e) TEM micrographs. Figure 22 shows: (a) XRD and (b) Raman spectra of SiO2 nanoparticles, and SiO2-C.

[0467] Figure 23 shows: XRD pattern of CaTiOa-C core-shell nanostructure.

[0468] Figure 24 shows: XRD pattern of MgTiOa-C core-shell nanostructure.

[0469] SPECIFIC DESCRIPTION RMM Method

[0470] Certain embodiments of the present disclosure relate to the preparation of Fenton-like catalysts using a reactive molten salt method (RMM). The RMM involves the reaction of a molten salt with the reactants during processing, thereby influencing the phase composition and catalytic performance of the final product. In one specific embodiment, as illustrated in Figure 1 , waste polyethylene terephthalate (PET), commercially available titanium dioxide (Ti02), and sodium chloride (NaCI) are utilized as raw materials. The molten salt-assisted thermal processing of these materials, followed by washing, results in the formation of a composite material comprising

[0471] 45P / 91661

[0472] Na4Ti5Oi2 / Nao.23TiO2and carbon (NTC). The NTC material exhibits enhanced properties compared to certain conventional materials, making it an effective adsorbent and catalyst for the removal of inorganic and organic contaminants from water, including the removal of dye species.

[0473] Detailed Description of Examples

[0474] Examples are provided merely for illustrative purposes and do not limit the scope of the invention. The following experimental procedures, materials, and methods are provided to illustrate certain embodiments of the disclosure and should not be construed as limiting its scope. Variations in the described methods and materials may be made without departing from the spirit and scope of the invention, as will be understood by those skilled in the art.

[0475] Materials and Reagents: Discarded bottles of mineral water were collected and employed as the carbon source in the preparation of NTC. Ti O2 (rutile, 99.8%, 25 nm, Aladdin, 13463-67-7, AR), tungsten trioxide (W03, Aladdin, 1314-35-8, 99.8% metals basis) and NaCI (99.5%, Aladdin, 7647-14-5) were purchased from Aladdin Reagent (Shanghai). Crystal violet (CV), methyl orange (MO) and malachite green (MG) were purchased from Shenyang Dongxing Reagent, Tianjin Zhiyuan Chemical Reagent and Macklin, respectively. These dye species were used as the target pollutants in the dye removal assays.

[0476] Characterization: X-ray diffraction was conducted using a Bruker diffractometer (D8 ADVANCE) utilizing Cu-Karadiation (A = 0.1542 nm) at 40 kV within 20 range 10° - 80° under the scanning speed of 6° / min. An Ultra Plus ZEISS scanning electron microscope (SEM) at 15 kV, and a Tecnai G2 F20 transmission electron microscope (TEM) at 200 kV were used for morphological characterizations. Raman spectroscopy was performed using a He-Ne laser Raman spectrometer (HR800) with an excitation wavelength of 633 nm to analyze the vibrational properties of the samples. The surface area and pore size distribution were characterized through nitrogen adsorption-desorption isotherms at 77 K, utilizing a physisorption analyser (Micromeritics ASAP 2460). To investigate the surface chemical composition and the valence states of elements present in the samples, X-ray photoelectron spectroscopy (XPS) was carried out using a Thermo Scientific K-Alpha spectrometer. Oxygen vacancies on the surface of the NTC were detected via electron paramagnetic resonance (EPR) analysis, conducted on a Bruker EM-Xnano system (Germany) at the Microwave frequency of 9.618865 GHz and power of 3.162 mW. A Nano ZS (ZEN3600, Malvern, UK) device was used to measure Zeta potential of NTC at various pH levels. Additionally, ultraviolet-visible (UV-Vis) absorption spectra of the samples were recorded using a Thermo Scientific Evolution 220 spectrometer, with wavelength measurements spanning from 200 to 750 nm.

[0477] 46Adsorption and catalysis assays: This study explores the adsorption and catalytic performances of Na4Ti50i2 / Nao23Ti02@carbon (NTC) for the removal of cationic dyes comprising crystal violet (CV) and malachite green (MG), and also the methyl orange (MO) anionic dye from aqueous solutions. UV-Vis spectra were recorded on dye solutions to determine the intensity of the absorption peak at 580, 616 and 464 nm for CV, MG and MO, respectively, based on which the values of dye concentration during the degradation process could be quantified. To understand the adsorption and catalytic capability of samples, the effect of various parameters on the dye removal performance of materials were taken into account. These parameters include the catalyst dosage (400, 500, 600, 700 and 800 mg / L), H2O2 dosage (333, 3663, 7326, 10989, 14652 and 18315 mg / L), CV concentration (100, 125, 150, 175 and 200 mg / L), the solution temperature (20, 25, 30, 35 and 40 °C) and the pH value (4.0, 7.0 and 9.0). Isopropyl alcohol, p-benzoquinone and furfuryl alcohol were used as radical scavengers to remove -OH, -O and1O2, respectively.

[0478] The dye removal rate and the adsorption capacity of the agent were evaluated according to the equations (1) and (2), respectively:

[0479] Co ~ Ct

[0480] %Removal rate = — - - x 100 (1)

[0481] Co

[0482]

[0483] Here, Coand Ctrepresent the concentration of dye at various stages, namely at the initial solutions and a given time (t), respectively. qt(mg / g) is the amount of dye adsorbed on adsorbent at the certain time (t), while m (g) and V (L) are the mass of adsorbent and the volume of the dye solution, respectively.

[0484] The first-order reaction kinetic model was used to investigate the removal of CV using NTC, employing the Eq. (3)

[0039] :

[0485] In— = krt (3)

[0486] Here, CQand Ctare dye concentration in the solution at the reaction time = 0 and t min, respectively; k (min-1) is the pseudo-first-order reaction rate constant, and t is reaction time (min). For this, a concentration of 400 mg / L NTC was used for the degradation of CV (100 mg / L) in the presence of H2O2 of various concentrations.

[0487] Example 1. Preparation of NTC

[0488] Na4Ti50i2 / Nao 23Ti02-carbon (NTC) was prepared using a clean and scalable molten salt treatment approach using waste PET and commercially available TO2. For this, PET plastic bottles were converted into rectangular pieces and cleaned with ethanol in an ultrasonic cleansing bath and dried in an oven over night. Quantities of 30 g PET, 100 g NaCI and 1 g TiO2 were mixed thoroughly in a beaker. Then, the mixture obtained was placed into a ceramic crucible (alumina) with the diameter and height of around 10 cm, and the loaded crucible was

[0489] 47P / 91661

[0490] covered with an alumina cap, and heated in a vertical resistance furnace to the target temperature of 900 °C (4 °C / min) in air. After heating for 1 h at the target temperature, the furnace was cooled down to room temperature under the same rate, and the sample obtained was washed with sufficient quantities of distilled water to remove the salt content, followed by vacuum filtration and drying overnight to obtain NTC.

[0491] Structural Characterization: The XRD examination (Figures 2a and b) provided detailed information on crystalline structure of the initial TiO2 and NTC product fabricated by the method exhibited in Figure 1. As can be seen in Figure 2a, the TiCh material has a rutile-tetragonal structure. In contrast, the diffraction pattern of the NTC product (Figure 2b) is characterized by the presence of crystalline phases comprising Na4TisOi2 and Nao23Ti02. In particular, diffraction peaks at 21.38°, 33.65°, 34.17°, 38.70°, 44.33°, 51.34°, 53.41°, 60.48°, 61.53°, 70.73° and 72.02° corresponds to the (011), (110), (013), (2-12), (113), (114), (211), (213), (106), (220) and (107) crystal planes of hexagonal-Na4Ti5Oi2 (ICCD 00-052-1814), respectively, with lattice parameters of a=b= 5.324 A, c= 9.565 A, y=120°.

[0492] Moreover, the peaks observed at the two-theta values of 24.36°, 28.87°, 29.55°, 47.25° and 66.98° correspond to the (110), (002), (111), (020) and (711) plans of monoclinic-Nao23Ti02 (ICCD#00-022-1404), respectively, with lattice parameters of a= 12.159 A, b= 3.844 A, c= 6.464 A, 0=106.99°. Also, there is no diffraction peak related to carbon in the pattern, indicating that carbon present in the material is nanocrystalline.

[0493] Overall, the XRD pattern of Figure 2a, confirms the presence of Na4TisOi2 and Nao.23Ti02 phase. The carbon component of the NTC product could be analysed by Raman spectroscopy, which is powerful technique to characterize both titanium oxide

[0040] and carbon materials

[0041] , The Raman spectra of the TO2 initial material and the NTC product are shown in Figures 2c and d, respectively. The Raman spectrum of the rutile TO2 (Fig.

[0494] 2c) exhibits a peak at 237 cm1corresponding to multi-photon processes, and peaks at 143 and 445 cm1to the Eg mode in the tetragonal lattice of oxide. The peak at 608 cm1is assigned to the Aigmode [42-43].

[0495] Raman spectrum of the Na4TisOi 2 / Nao 23TiO2@carbon composite (Figure 2d) show several characteristic peaks belonging to Na4Tis012 and Nao 23 O2. Accordingly, the Raman peak at around 192 and 911 cm1are attributed to the Ti-0 stretching vibration, and the peak at 239 cm1to the Ti-O-Ti stretching vibration

[0044] , Also, the peaks at 283, 401 and 631 cm1corresponds to the Ti-O-Na vibrations. The Raman results confirm the XRD examination of Figure 2a, confirming the incorporation of Na in the titanium oxide leading to the formation of Na4TisOi2 and Nao.23Ti02 phases.

[0496] The Raman spectrum of NTC (Figure 2d) also exhibits distinct peaks at around 1333 cm1corresponding to the D band in carbon materials, which mainly represents the degree of structural disorder and crystal defects. Moreover, there is another peak at round 1594 cm1, called the G band, often arises from the Raman active E2g

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[0498] vibration mode generated from sp2stretching in graphitic carbon. The relative band intensity ID / IG can be used to describe the degree of graphitization. This value was measured to be relatively large at 1.18 in NTC representing the presence of nanocrystalline hexagonally oriented carbon domains, as also confirmed by the XRD pattern of Figure 2a. The presence of carbon can lead to the formation of surface defects and vacancies in NTC, as will be discussed in this article.

[0499] Example 2. Morphological characteristics of NTC

[0500] In this example, the morphological characteristics of the TiO2 initial material, and the NTC fabricated based on the method of example 1 are presented. The morphology and microstructure of the TiO2 and NTC were characterized using scanning and transmission electron microscopy. Figure. S1 a shows the SEM morphology TO2, in which the presence of nanospherical particles with dimensions typically less than 100 nm, and rather agglomerated, is evident. The SEM micrograph of NTC (Figure 3a) is entirely different from that of TO2, dominating by presence of rod-like particles with the length of typically greater than 10 pm, and the remaining carbon particles obtained by the molten salt carbonization of PET. Figure 3b shows the high-yield presence of such rod-like particles in NTC. EDS analysis recorded on a rod-like particle shown in Figure S1c is exhibited in Figure. S1d, confirming the presence of carbon (24.78 wt%), oxygen (31.34 wt%), sodium (5.46 wt%) and titanium (38.42% wt%). The corresponding EDS elemental map analysis (Figure S1e) shows the rather uniform distribution of C, 0, Na and Ti in Na4Ti50i2 / Nao23Ti02@carbon hybrid structure. According to these observations, in Na4Ti50i2 / Nao23Ti02@carbon, the sodium titanate phases are incorporated into the caron phase. Particularly, the sodium titanate phases can be coated with the carbon phase. This morphological integrity enhances the catalytic performance of the NTC.

[0501] The TEM micrographs of NTC (Figure S2) show the presence of carbon and Na4Ti50i2-Nao 23TiO2 phase. High resolution TEM micrographs of Figures S2c and d exhibit the crystalline lattice spacing of 0.129 nm, corresponding to the (034) crystalline planes of Na4TisOi2. Figure 3c shows the high-resolution micrograph recorded on NTC, in which the presence of Nao 23TO2 and N4TisOi 2 is evident, as confirmed by the FFT patterns of Figures 3d and e, respectively. Figure 3f exhibits a No 2sTiO2 crystal, with FFT pattern demonstrating the crystalline planes in the monoclinic structure of the crystal (Figure 3g). A layer of graphene-like carbon on the crystal can be characterized, as highlighted in Figure 3h.

[0502] Without being bound by theory, these observations can be explained based on literature reports, which indicate that the carbonization of PET in air, in the absence of Ti02and NaCI, leads to the formation of amorphous carbon exhibiting exceptional thermal oxidation resistance at temperatures up to 900 °C. This remarkable resistance can be attributed to the carbon's high purity and low density of surface defects. At 900 °C, the

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[0504] presence of NaCI (with a melting point of «800 °C) further protects the carbon material from oxidation while also promoting partial graphitization, leading to the formation of nanocrystalline carbon, as shown in Figures 3f and 3h. Although this nanocrystalline carbon does not produce a distinct XRD peak, as evident in Figure 2b, it does exhibit a characteristic Raman signature, as shown in Figure 2d.

[0505] Example 3. Surface characteristics of NTC

[0506] In this example, the surface characteristics of the TiO2 initial material, and the NTC fabricated based on the method of example 1 are presented. Surface characteristics of the initial TiC>2 and the NTC were further characterized by N2 adsorption and desorption examination, followed by the evaluation of BET surface area and porosity characterization based on the BJH model. The results obtained are exhibited in Figures 2e-h. The isotherm curves of TiO2 (Figure 2f) shows type IV isotherms with a type-Hs hysteresis loop, implying the presence of mesoporous nanostructures in TiO2. The surface area of the TO2 material could be obtained to be 31.5 m2 / g. Likewise, the isotherm curves of NTC (Figure 2e) show the same isotherms and hysteresis loop, implying the presence of mesoporous nanostructures in the NTC. However, the surface area of the NTC could be obtained to be 621.0 m2 / g, substantially greater than that of TiO2. Moreover, the total pore volume of NTC (0.3184 cm3 / g) is almost three times greater than that of TiO2 (0.1133 cm3 / g). Figures 2g and 2h show the pore volume distribution for NTC and TO2, with peaks at 4.1 nm and 3.2 nm, respectively, suggesting the presence of mesopores and possibly some micropores in both samples. However, the rutile phase (TO2) exhibits a lower pore volume in comparison with NTC, as indicated by a flatter profile, suggesting its lower porosity.

[0507] The XPS characterization could provide further insights onto the surface chemistry and the elemental chemical states in TO2 and NTC, and the results obtained are presented in Figure 4. From the full survey XPS spectra of the TiO2 (Figure 4a), the surface elements consist of 0 and Ti. For the case of NTC (Figure 5d), the presence of C, Na, 0 and Ti is evident, consistent with the EDX result shown in Figure S1d. The surface chemical composition of the bifunctional adsorbent / catalyst could be characterized based on the XPS analysis to be C = 82.57 at%, Na = 2.15 at %, 0 = 13.75 at % and Ti = 1.53 at %.

[0508] The high-resolution Ti 2p peaks of the TiO2 and Na4Ti50i2 / Nao 23Ti02@carbon are shown in Figures. 4c and h, respectively. The binding energy values in TiO2 are at 458.31 and 464.03 eV, respectively, indicating that Ti element are comprised of Ti4+ions. Compare with the TO2, a positive shift of 1.47 and 1.35 eV was observed in the binding energy values of Ti 2p3 / 2 and Ti 2p1 / 2, respectively, after Na doping in NTC (Figure. 4h). The shift is attributed to the electron transfer between Ti and the alkali metal, Na, resulting in the reduction of the valence of Ti element.

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[0510] The absence of any discernible Ti3+signal in the XPS spectra of samples indicates that no significant reduction of Ti4+to Ti3+has occurred. Consequently, this suggests that the oxygen vacancies either do not exist in substantial quantities, or passivated, e.g., by adsorbed hydroxyl or oxygen species. Electron paramagnetic resonance spectroscopy was used to characterize the oxygen vacancies in NTC, as will be discussed.

[0511] As can be seen in Figure 4e, the C 1s XPS spectrum of the NTC can be divided into four peaks at 284.8, 285.89, 286.78 and 288.69 eV, corresponding to the -C=C-, -C-C-, C-0 and C=0

[0059] , respectively.

[0512] The 0 1s peaks of Ti02and NTC are shown in Figures. 4b and 4f, respectively. In the 0 1s spectrum of Ti02(Figure 4b), the peak at 529.52 eV is attributed to the crystal lattice oxygen, indicating the presence of 02’ corresponding to the oxygen-titanium bond. Additionally, the small peak at 531.33 eV is assigned to surface hydroxyl groups (OH), which are commonly formed due to exposure to ambient conditions. On the other hand, in the 0 1s XPS spectrum of NTC (Fig. 4f), the peak at 531.18 eV is also attributed to surface hydroxyl groups. The peaks at 532.48 eV and 534.98 eV are likely associated with adsorbed species, such as water or carbonates, formed during exposure to air, rather than intrinsic non-lattice oxygen or defective oxides. Finally, the peak observed at 1071.68 eV is attributed to the sodium cation present in the titanate structure (Na-O) of NTC.

[0513] Example 4. Electron paramagnetic resonance spectroscopy

[0514] In this example, the electron paramagnetic resonance (EPR) spectroscopy results recorded on the TO2 initial material, and the NTC fabricated based on the method of example 1 are presented. EPR is a very sensitive and powerful technique to characterize the oxygen vacancies in materials, including titanium oxides. As shown in Figure 2i, no EPR signals can be observed in the raw TO2 sample. In contrast, the signals for the oxygen vacancies could be detected in the NTC sample at a g value of g=2.003, indicating the presence of oxygen vacancies in NTC.

[0515] Without being bound by mechanism, such oxygen vacancies are induced by the introducing of sodium ions into TiO2 and also possible surface reduction of oxide by the PET-derived carbon. Oxygen vacancies can regulate the electronic structure of the catalyst and form more active sites, thus improving the performance of the catalyst. The XPS and EPR characterizations mentioned above confirm the presence of oxygen vacancies in the NTC catalyst, suggesting the desirable catalytic performance of the sample.

[0516] Without being bound by theory, the influence of the process of producing NTC on its characteristics can be discussed. It should be mentioned that graphite and graphitic carbon nanostructures oxidise in air at temperatures greater than 600 °C, while the presence of molten salt can protect such materials from extensive oxidation. In contrast, carbon materials derived from PET was found to have substantially greater resistance for

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[0518] oxidation due to their semi-amorphous structure. During the preparation of NTC (Figure 1), the carbonization of PET leads to the formation of carbon, while the presence of molten salt prevents the excessive oxidation of the carbon material at elevated temperatures. Therefore, the availability of the PET derived cardon can lead to the surface reduction of TiO2 to form TiO2 x. Moreover, the incorporation of Na from molten salt into TiCh can provide further structural defects that provide the driving force for the rapid growth of TiO2 nanoparticles (Figure S1a) into one-directional Na4TisOi2 / Nao 2aTiO2. As shown in Figure 3f, the surfaces of these crystals are likely to be covered by layers of graphene-like carbon, which can improve both the adsorption and catalytic performances and the material in various environments. The high surface carbon content of NTC (C = 82.57 at%), calculated based on the XPS analysis of Figure 4 is due to the presence of the PET-derived carbon, covering the surfaces of Na4Ti50i2 / Nao23Ti02, providing additional dye adsorption capacity, and also promoting the catalytic performance of the sodium titanates.

[0519] Therefore, without being bound by the mechanism, the formation of rod-like particles observed in Figure 3 can be explained to be driven by solid phase crystal growth of sodium-titanium oxide crystals, under the influence of carbon material derived from the carbonization of PET. It was reported elsewhere that heat-treatment of SnO2 single crystals attached with graphitic flakes can form nanostructures including nanowires and nanosheets, where graphite could function as a surface reducing agent, facilitating the conversion of SnO2 into oxygen-deficient oxides. This reduction process provides a driving force for surface diffusion, promoting the crystalline growth of tin oxide into one- and two-dimensional nanostructures.

[0520] In fact, introducing oxygen vacancies and Ti3+defects into crystalline lattice of titanium oxide have received attention in the literature, since such oxygen vacancies and defects play an important role in photocatalysis. On one hand, such defects increase the light absorption, and on the other hand, provide more reactive sites for photocatalytic reactions. In addition to this, oxygen vacancy is considered an electron donor, and therefore, improves the separation of photogenerated electrons and holes, increasing the carrier concentration of the material and its photocatalysis performance. Also, density functional theory calculations (DFT) has revealed that the presence of oxygen vacancies on the catalyst surface can increase the exposure of active sites, promoting the electron transfer which accelerate the rate of *0H generation, crucial for overcoming the limitations of the low reactivity of heterogeneous Fenton catalysts.

[0521] Without being bound by any particular mechanism, the findings of this disclosure disclose that (a) the partial reduction of TiO2 by carbon derived from PET generates oxygen vacancies, (b) the incorporation of Na from the molten salt induces structural defects, and (c) the incorporation of carbon into NTC facilitates electron transfer pathways, with these factors collectively enhancing the catalytic performance of the resulting NTC.

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[0523] Example 5A. Adsorption and Fenton-like catalytic performances

[0524] In this example, the adsorption and the Fenton-like catalytic performances of the initial TO2, and the NTC prepared based on the Example 1 are discussed. The example evaluates the removal of organic dyes from their aqueous solution using NTC.

[0525] For this, the CV solution was exposed to various materials including NTC, TiO2, H2O2, NTC+H2O2, TO2-+I2O2 in dark. The CV removal performances are shown in Figure 5. As can be seen, in the presence of TiO2 and NTC, the removal rate of CV was recorded at 5.41% and 66.4% after 180 min of adsorption, providing a CV adsorption capacity of 13.63 and 165.8 mg / g respectively. The greater adsorption capacity of NTC can be related to the presence of PET-derived carbon in the sample.

[0526] In order to evaluate the Fenton-like catalytic performance of samples, the performances of H2O2 alone, and in combination with TiO2 and NTC were evaluated, as can be seen in Figure 5a. H2O2 alone and in its combination with TO2 did not show a noticeable activity in removing CV from the solution, suggesting that the degradation of CV by H2O2 is challenging and that TiO2 does not provide a considerable Fenton-like catalytic performance. On the other hand, a noticeable CV degradation can be observed by the NTC in the presence of H2O2, indicating the effective Fenton-like activity of the agent (Figure 5a). As observed, almost 100% of CV was removed within 180 min at a degradation rate of 0.0085 min1. Based on these observations, NTC can be considered as a bifunctional adsorbe nt / Fenton-l ike catalyst for the efficient removal of organic dyes such as CV.

[0527] According to Figure 5b, the pseudo-first-order kinetics can explain the CV removal performance of TO2 and NTC, with and without the presence of H2O2, with the removal constants measured to be -3.12 x 10 min1(TiO2), -6.56 x 10-4min-1(TiO2+H2O2), 26 x 104min1(NTC) and 85 x 104min1(NTC+H2O2).

[0528] The results show that NTC has a substantially higher CV adsorption performance in comparison with that of TiO2, and that these performances are influenced considerably by the presence of H2O2 only for the case of NTC. Therefore, the results suggest the effective Fenton-like catalytic activity of NTC towards decomposition of organic pollutants. Considering the simple and green method of preparing the material, this agent has the capability of being used as bifunctional adsorbent / catalyst for the treatment wastewater at large scales. In order to better evaluate the Fenton-like catalytic performance of NTC, alteration of various parameters was considered including the catalyst dosage, H2O2 dosage, CV concentration, solution pH, temperature and the effect of radical trapping agents. The results obtained are shown in Figure 6, and discussed in the next section.

[0529] Effect of catalyst dosage on the CV degradation performance

[0530] The effect of NTC dosage (400-800 mg / L) on CV degradation in the presence H2O2 is shown in Figure 6a. As observed, the dye degradation is positively correlated to the dosage of NTC. At the NTC dosage of 400, 500,

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[0532] and 600 mg / L, the CV degradation efficiency could be recorded at 87.1%, 90.7%, and 96.7%, respectively, within 180 min exposure in dark. Further, when the amount of NTC was increased to 800 mg / L, the CV degradation efficiency was improved to 99.9% achieved within 90 min. This trend may be due to the fact that the higher the amount of bifunctional adsorbent / catalyst can provide more active sites, enhancing the effective contact between the agent, FhChand dye molecules. Such enhanced exposed surface can promote both the dye adsorption and also dye degradation through the formation of radicals at a greater rate.

[0533] Effect of H2O2 dosage on CV degradation

[0534] In Fenton-like processes, H2O2 serves as an efficient electron acceptor, enabling the efficient generation of hydroxyl radicals. The effect of H2O2 dosage on CV degradation performance of NTC was evaluated using various H2O2 dosages, using 800 mg / L NTC and 100 mg / L CV (Figure 6b). As can be seen, by increasing the H2O2 dosage from 0 to 300 mg / L, the dye removal performance of NTC sharply increases due to the Fentonlike catalytic effect of the agent. However, increasing the amount of H2O2 to higher amounts of 3700, 7300, 11000, 14600 and 18300 mg / L has a negative effect on the CV degradation performance of NTC. When the amount of H2O2 is further increased to 14600 mg / L, the CV removal efficiency of the agent (82.8%) reduces to a value lower than the adsorption performance of NTC for CV (85.4%) after 75 min.

[0535] The reasons behind the inhibition of Fenton-like reaction by increasing the amount of hydrogen peroxide can be suggested to be based on the self-sensitivity of the system at higher concentrations of hydrogen peroxide. In other words, the generated hydroxyl radicals may react with hydrogen peroxide to generate alternative species (-O2H and O2) with low oxidation capacity, thereby reducing the efficiency of Fenton oxidation.

[0536] Effect of the initial CV concentration of degradation performance

[0537] The effect of initial CV concentration on its removal performance by NTC is shown in Figure 6c. As can be observed, the CV degradation efficiency decreases with an increase in the CV concentration. It is obvious that as the solution concentration elevates from 100 to 200 mg / L, a noticeable decline in the removal rate was observed, plummeting from an initial value of 99.1% to 60.4% after 60 min Fenton-like reaction. This reduction in removal efficiency can be attributed to the fact that at higher concentrations, the available active sites on the adsorbent / catalyst surfaces are more extensively occupied by CV dye molecules, resulting in the production of fewer hydroxyl radicals, resulting in less efficient removal of the target contaminant. On the other hand, the higher CV concentrations could reduce the turbulence and cavitation of the solution, thus reducing the production of reactive radicals as well as the mass transfer rate between the solid-liquid system.

[0538] Effect of pH on CV degradation

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[0540] In the Fenton and Fenton-like process, pH is one of the key factors affecting the performance of the catalyst, due to its effect on the surface potential of the catalyst, and its interaction with H2O2. Generally, the traditional Fenton process is limited by a narrow applicable pH range of 2.5 to 3.5. However, the NTC material produced in this study, exhibits a considerable catalytic activity over a wide pH range as shown in Figure 6d. Accordingly, the CV degradation efficiency of NTC increases by increasing the pH from 4.0 to 5.4, recording vales of 80.9% and 99.1%, respectively, within 1 h. The main reason behind this observation can be the competition between CV molecules as a cationic dye and H+ions at lower pH values that reduce the adsorption of dye on the catalyst under acidic conditions, resulting in reduction in adsorption performance of the sample. Under this condition, the Fenton-like degradation can be the main mechanism involved in the CV removal performance of NTC, which is also limited due the lower attraction between the CV and NTC.

[0541] As can be seen in Figure 6d, further increasing the value of pH to 7.0 and 9.0 provides a limited impact on the CV degradation efficiency of NTC, with values of 99.2% and 98.9%, respectively, which is due to competitive activity of adsorption and Fenton-like degradation reaction at greater pH values.

[0542] The zeta potential of NTC was measured at various pH levels of 4.0, 7.0 and 9.0, and the results are shown in Figure. 2I. The zeta potentials of NTC were recorded at -4.9 mV (pH=4.0), -18.6 mV (pH=7.0) and -21.8 mV (pH=9.0). Since the surfaces of the bifunctional adsorbent / catalyst is negatively charged at a wide pH value of 4.0-9.0, the electrostatic attraction of cationic (positively charged) dyes are favourable, especially under alkaline conditions. As can be observed, the catalyst exhibits an excellent performance within 60 min of exposure at a wide range of initial pH (4.0-9.0), which overcame the shortcut of narrow pH value in the conventional Fenton reaction process. These characteristics make NTC an effective bifunctional adsorbent / catalyst for the decomposition of organic compounds.

[0543] Effect of temperature on dye removal performance of NTC

[0544] Figure 6e displays the effect of solution temperature in the range 20 - 40 °C on CV degradation performance of NTC. As can be depicted, a nearly complete degradation of CV can be realized within 35 minutes at 40 °C, attributed to a markedly elevated reaction rate constant of 9.48 xio2min1, six times greater than that observed at 20 °C with the reaction rate constant of 1.58 x 102min-1. This suggests that increasing temperature within the range of our trials particularly facilitates the adsorption on CV onto the NTC, thus improving the Fenton-like degradation of the dye species.

[0545] It should be considered that evaluating the individual contributions from the chemical degradation of dye species via Fenton-like reaction and the physical adsorption of dye onto surfaces of the agent is challenging due to the dual nature of the processes involved. However, under certain conditions and with appropriate assumptions, a

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[0547] first-order kinetic model can provide useful insights. These assumptions are based on the catalyst and hydrogen peroxide is in excess, and dye molecules adhere to the surface of the solid adsorbent, while both the chemical and physical processes contribute to the overall rate of dye removal from solution.

[0548] The kinetics parameters were evaluated based the adsorption mechanism, where the process is conducted in the absence of H2O2, and also based on mixed mechanism, where H2O2 is involved. According to latter, and the dye species are removed by both adsorption and Fenton-like degradation. Figure 7 a present the first-order reaction kinetics model

[0039] evaluating the adsorption of CV in the absence of H2O2, where the slope of curves indicate the rate constant involved the adsorption process. Figure 7c presents the same in the presence of H2O2, exhibiting mixed adsorption and Fenton-like degradation process. The related parameters are presented in Table 1 , from which it’s evident that the removal rate constant rises with the increase of temperature in both cases. This phenomenon is due to the fact that higher temperatures promote collisions between molecules, so that more molecules gain energy beyond the activation barrier contributing to the adsorption and Fenton-like reaction. Furthermore, at the same temperature, the rate constant of the mixed adsorption and Fenton-like reaction is 3.5 to 6.6 times greater than that of the adsorption process, indicating that the mixed adsorption and Fenton-like reaction proceeds at a significantly faster rate than adsorption process.

[0549] The total activation energy (Ea) required to promote the dye removal by adsorption mechanism and mixed adsorption and Fenton-like degradation mechanism can be calculated to be 38.3 and 51.0 kJ mol1, respectively, according to the Arrhenius equation (Eq. (4)), and the results are presented in Figs. 7b and d:

[0550] E

[0551] lnK 1 = InA -a

[0552] RT(4) J

[0553] Here, Ki is the reaction rate constant of the first-order reaction kinetic model, R is the gas constant (8.314 J mol1K1), A represents a constant, Eais the activation energy (kJ mol1) and T is the reaction temperature (K). According to the results obtained, the adsorption mechanism requires less energy to proceed than the mixed mechanism, suggesting that the adsorption process alone is likely to occur more readily and quickly compared to the mixed process. The higher activation energy of the mixed mechanism reflects the added complexity and energy requirement of the Fenton-like degradation process, which involves chemical reactions (such as the generation of hydroxyl radicals) in addition to simple adsorption. While the adsorption mechanism is quicker due to lower activation energy, the mixed mechanism is potentially more effective for complete dye degradation. This information can help optimize the process to make the most of the bifunctional agent for cost-effective and efficient wastewater treatment.

[0554] Table 1 The reaction rate constant (Ki, min1) of the first-order reaction kinetic model and activation energy (Ea, KJ / mol) in the adsorption process and mixed adsorption and Fenton-like degradation process.

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[0556] Adsorption Adsorption-fenton-like

[0557] Temoerature (°C)

[0558] K1 Ea K1 Ea

[0559] 25 6.89X10-33.85x10-2

[0560] 30 9.96x10-3 3.75x10-2

[0561] 38.3 51.0

[0562] 35 12.86x10-3 6.76x10-2

[0563] 40 14.36x10-3 9.48x10-2

[0564] Example 5B. Fenton-like degradation mechanism

[0565] The bifunctional NTC was prepared according to the Example 1 and used as an efficient adsorbent / catalyst for the removal of crystal violet (CV) from its solution. In this example, the Fenton-like process involved in the CV removal performance of NTC is studied in more details. It is well known that the formation of various radicals such as -OH, -O and1O2 play important role in the oxidative degradation of organic pollutants in catalytic systems

[0076] . In order to understand the role of such radicals in our case, the radical trapping experiments were carried out using isopropyl alcohol (IPA), p-benzoquinone (BQ) and furfuryl alcohol (FA) as radical scavengers to quench -OH, -O and1O2, respectively. For this, 80 mg NTC, 0.3 mg / L H2O2 and radical trapping reagent (Isopropyl alcohol (IPA): 5 mL, p-benzoquinone (BQ): 1.3 mg, and furfuryl alcohol (FA): 5 mL) were added into 100 mL CV solution with a concentration of 100 mg / L, and the dye removal rates were studied.

[0566] According to the results obtained (Figure 6f), in the presence of IPA, BQ and FA, the CV removal rates obtained increases by increasing the processing time, which is partly due to the adsorption performance of the bifunctional agent. However, the CV removal rate of NTC (without the presence of H2O2) and that of Fentonlike degradation / adsorption (with the presence of H2O2) is 73.8% and 99.1%, respectively. On the other hand, in the presence of IPA and BQ, the CV degradation efficiency of NTC+H2O2 could be detected to be 95.3% and 94.8% within 60 min, respectively, slightly lower than that of NTC+H2O2 without the presence of any radical scavenger (99.1%). These results indicate that -OH and -Q are not dominant reactive oxygen species (ROS) involved in the Fenton-like reaction.

[0567] On the other hand, as can be seen in Figure 6f, the introduction of the FA remarkably limits the degradation of CV. In this case, the CV removal rate was recorded at only 68.2% after 60 min treatment, which is even lower than the adsorption performance of NTC (73.8%). This is because in addition to the activity of FA in trapping1O2 radicals, it also competes with CV to adsorb on the surfaces of NTC, reducing the CV adsorption performance of NTC. The results of radical trapping experiments show that -OH, -Q and1O2 can affect the CV degradation efficiency of catalyst, while1O2 radicals are likely to be the key reactive oxidative species involved in the Fenton-like catalytic process.

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[0569] The generation of102 has been reported in various Fenton-like systems, including titanium oxides to be based on the Haber-Weiss mechanism:

[0570] Ti+3+ H2O2Ti+4+■ OH + 0H“ (5)

[0571] Ti+4+ H2O2Ti+3+■ OOH + H+(6)

[0572] ■ OH + H2O202+ H20 + H+(7)

[0573] • 02+• HOO -x02+ HOO- (8)

[0574] • HOO +• HOO -x02+ H202(9)

[0575] 70s + H202OH + OH” (10)

[0576] CV +• OH / - 02 / x02-> intermediate -> C02+ H20 (11) Accordingly, Ti3+can be utilized as an inorganic reducing agent due to its remarkable electron-donating properties, enabling swift single-electron redox reactions with H2O2, thus promoting the Fenton reaction mentioned above. For the case of NTC, the abundant oxygen vacancies detected on rod structure of sodium titanates, based on XPS analysis of Figures 4 and 2i, can function as an effective oxygen ion conductor to activate H2O2 by boosting the charge transfer and lowering the reaction energy barrier. Therefore, the rapid restoration of titanium ions’ oxidation state occurs through the diffusion of oxygen ions and electrons from the oxide, resulting in the generation of numerous reactive radicals, as shown in reactions (7)-(9).

[0577] As discussed, such structural defects are likely to form due to the surface reduction of titanium oxides by PET-derived carbon and also introduction of Na from molten salt toward the formation of Na4TisOi2 / Nao 23 O2. Without being bound by mechanism, the formation of oxygen vacancies induces alterations in the electronic structure and chemical characteristics of the catalyst, thereby creating additional active sites, as shown in the reaction (10). This modification enhances the efficiency of electron transfer, ultimately facilitating the catalyst’s heightened activity in the activation of H2O2. At the same time, the presence of PET-derived carbon, characterized based on Raman spectroscopy (Figure 2c) and microscopy (Figure 3) provides a desirable electronic conductor interface to promote the Fenton-like reaction.

[0578] Based on the results obtained and the above discussion, a possible reaction mechanism for CV removal by NTC / H2O2 system can be proposed, as illustrated in Figure 8, and reactions (5)-(11 ). Accordingly, at the first step of this mechanism, H2O2 is adsorbed on the surface of NTC along with CV, facilitated by the large surface area and the carbon layers present in the agent. In the second step of the process, the adsorbed H2O2 is activated, primarily due to the presence of Na4TisOi2 / Nao 23TiO2, leading to the generation of radicals such as ■OH, '02-, and102, with102being the predominant species. At the last step of this mechanism, the generated radicals efficiently degrade the CV dye adsorbed on the surface of NTC. Finally, the active radicals readily attack

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[0580] the adsorbed CV nearby, indicated by the reaction (11). The high surface area, the presence of abundant active sites and PET-derived carbon provide the NTC the possibility of acting as dual functional adsorbent / Fenton-like catalyst for the efficient removal of dye species. The experiments mentioned above were conducted using CV, but a large number of other organic dyes can be removed from their solution, as presented in the following section.

[0581] Example 6. Performance of NTC in removing alternative organic compounds

[0582] The adsorption performance of NTC, in the absence of H2O2, for the removal of crystal violet (CV), methylene orange (MO) and malachite green (MG) are compared in Figure 9a. For this, same qualities of dye species (CV: 100 mg, MO: 100 mg, MG: 100 mg) were added into 100 mL water. According to Figure 9a, the NTC's adsorption rate for the three dyes within the same time period (180 min) are MG (98.1%) > CV (92.9%) > MO (25.2%). These observations can be explained by considering that MG and CV are cationic dye, and MO is an anionic dye. As can be seen from Figure 2I, the zeta potential value of NTC pH 4.0-9.0 is negatively charged, providing the material with greater potential to adsorb cationic dye molecules due to electrostatic adsorption, which is consistent with the observation of Fig. 7a.

[0583] Furthermore, the dye removal performance of NTC for MG, CV and MO was studied with the presence of H2O2, and the results are shown in Figure 8b. For these experiments, 80 mg NTC was added into 100 mL solutions containing 100 mg / L dye species in the presence of 0.3 g / L H2O2. According to Figure 7b, the dye degradation efficiency of NTC for three dyes after 60 min treatment follows the order of CV (99.1%) > MG (98.8%) > MO (23.5%). Therefore, the dye removal efficiency of the bifunctional NTC can directly be correlated with the adsorption performance of the agent, highlighting the importance of adsorption in overall dye removal performance of the sample.

[0584] As can be seen from Figure 9b, the Fenton-like degradation of cationic dyes are similar, same as their adsorption performance, significantly higher than that of MO. The other observation is that the Fenton-like dye degradation performance of NTC for the anionic dye (MO) after 60 min (23.5%) is even lower than the adsorption capacity of the agent, without the presence of H2O2, after the same duration of time (25.2%). This behaviour can be attributed to the electrostatic repulsion between the negative potential on the Fenton-like catalyst surface and the negatively charged anionic dye molecules. This repulsion results in a decreased number of dye molecules adsorbed on the catalyst surface, leading to a reduction in degradation efficiency.

[0585] Example 7. Comparison of the NTC performance with certain alternative materials

[0586] NTC material was prepared according to Example 1, and its dye removal performance was compared with certain alternative materials. Table 2 summarizes the dye removal performances of selected agents, extracted

[0587] 59P / 91661

[0588] from the literature, containing the type of organic pollutants and their concentrations, H2O2 dosage, and the properties of the agents. The role of oxygen vacancy in the overall performance of the agent catalyst is also highlighted.

[0589] For instance, defect-engineered TiCh-x single crystals (Ti02-x SCs) have been fabricated by a simple hydrothermal method using tetrabutyl titanate and HF, followed by calcinating at 400 °C for 5 h in H2 atmosphere, and the agent was used for the removal of MO. The highest MO removal efficiency of more than 95% was obtained within 4 h using this agent (MO concentration: 10 mg / L; pH=4.0; catalyst dosage: 0.1 g / L; H2O2 concentration: 5 mM). These results show that oxygen vacancy can be considered as an active site in the Fenton reaction. Tetrabutyl titanate and tetraethyl orthosilicate have been employed to prepare defective amorphous TO2 enriched with Ti3+and oxygen vacancies (Ov) by a sol-gel method combined with calcination, leading to the formation of a catalyst with the surface area of 308 m2 / g.

[0590] As shown in Table 2, NTC requires a low concentration of H2O2 (0.3 g / L) to achieve optimal performance, which is significantly lower than the concentrations used with alternative Ti-based catalysts, such as 1.7 g / L or even 10.2 g / L, offering additional economic and safety benefits.

[0591] Table 2. Comparison of the dye removal efficiencies of various Fenton-like catalyst system. Dye systems include crystal violet (CV), methyl orange (MO), Rhodamine B (RhB).

[0592] >

[0593]

[0594] The Fenton-like Rh B degradation performance of the agent was based on the generation of hydroxyl radical (•OH), produced through the activation of hydrogen peroxide at the active site of Ti3+. Such radicals effectively interact with oxygen vacancies and hydroxyl groups present on the surface of TiO2, leading to the formation of singlet oxygen (1O2), accelerating the dye degradation. They added 0.2 g / L catalyst into 50 ml Rh B solution with a concentration of 20 mg / L at pH=7 and H2O2 concentration is 0.015 M. The material showed Rh Ba degradation efficiency of approximately 100% after 50 minutes of exposure. Wang et al. synthesized chitosan- 60P / 91661

[0595] derived maillard reaction productions coated CuFeCh (0v-CuFe02@MRPs) with a large number of oxygen vacancies for the degradation of RhB via a hydrothermal method using Cu(NO3)2*3H2O, FeSOTFkO and chitosan as raw material. In this work, the role of oxygen vacancy in the catalyst was studied by DFT calculation, indicating that the introduction of oxygen vacancy provides active sites to increase the adsorption of H2O2, increasing the performance of the catalyst, thus promoting the activation of FkC^to form *0H. The degradation efficiency of RhB can reach to 100% within 90 minutes of exposure utilizing 50 mM H2O2, 10 mg / L RhB, 1.0 g / L catalyst and pH=6.8.

[0596] Compare with the literature, the approach employed in this disclosure uses waste PET, NaCI and TO2 as raw materials to fabricate Na4TisOi 2 / Nao 23TiO2@carbon with abundant surface oxygen vacancies and high specific area of 621.0 m2 / g by a simple molten salt treatment method. The synthesized Na4TisOi 2 / Nao 23TiO2@carbon was applied as a bifunctional adsorbent and Fenton-like catalyst for the adsorption / degradation of various cationic and anionic dye species, including CV. For the latter a dye removal efficiency of «100% was obtained at the CV concentration: 100 mg / L, pH=7.0 and the agent dosage of 800 mg / L, in the presence of H2O2 (0.3 g / L). The outstanding dye removal efficiency of NTC, coupled with its environmentally friendly production method make the material attractive as an efficient candidate for environmental remediation.

[0597] Based on Examples 1-7, the disclosure discloses the successful synthesis of bifunctional Na4Ti50i2 / Nao23Ti02@carbon (NTC) using a simple reactive molten salt treatment employing waste PET, commercially available TiO2, and NaCI. This material was used as an adsorption-Fenton-like catalyst for the removal of dye species from wastewater. The porous structure, abundant oxygen vacancies, and PET-derived carbon in NTC provide numerous active sites, enhancing both adsorption and Fenton-like capabilities for removing dye species from aqueous solutions. The influences of various parameters were studied on the Fenton-like degradation performance of crystal violet (CV) by NTC, including catalyst dosage, solution concentration, temperature, and initial pH level of the dye solution. The catalyst demonstrated excellent performance across a wide pH range (4.0-9.0), overcoming the narrow pH limitations of conventional Fenton reactions. The degradation efficiency of CV exceeded 99% after 60 minutes with 800 mg / L NTC, 100 mg / L CV, and 0.3 g / L H2O2. As the solution temperature increased from 20°C to 40°C, the reaction rate constant increased sixfold (from 1.58 x102min1to 9.48 x102min1), indicating a significant temperature effect. NTC achieved a dye degradation efficiency of 99.1 % and 98.8% within 60 minutes for cationic dyes, namely CV and MG, respectively, which was significantly higher than for the anionic dye MO at 23.5%. This difference was attributed to the surface charge of NTC at various pH levels. Scavenging experiments demonstrated that reactive species such as -OH, -O2-, and1O2 influence the decomposition process, with the latter identified as

[0598] 61the major reactive radical for degrading CV dyes. Additionally, oxygen vacancies are suggested to provide extra active sites that promote H2O2 activation. Furthermore, the inventor proposed possible mechanisms for the dye removal performance of NTC. The prepared NTC can be considered a promising, environmentally friendly bifunctional agent for the effective removal of organic compounds from wastewater.

[0599] Example 8. Preparation of W-doped-NTC

[0600] PET plastic bottles were cut into 1 x 1 cm2pieces, washed in an ultrasonic bath with ethanol, and dried overnight in an oven. A mixture consisting of 100 g NaCI, 30 g PET pieces, and various amounts of TiC>2 and WO3 ball-milled for 10 h were mixed and transferred into an alumina crucible with an alumina lid (diameter: 100 mm, height: 100 mm). The crucible was then placed in a vertical resistance furnace and heated to 820°C and 900°C at a controlled heating rate of 4°C / min, with a holding time of 1 h at the maximum temperature under an air atmosphere. The temperatures were selected to be above the melting point of NaCI (=800 °C). After the heat treatment, the crucible was cooled down to room temperature at the same heating rate, and the materials obtained were rinsed with sufficient quantities of deionized water to dissolve and remove the salt. The samples were then filtered using a vacuum filtration system and dried overnight in an oven. Finally, the samples were collected and labelled as W-doped-NTC820 or W-doped-NTC900 based on the synthesis temperature.

[0601] In order to confirm the role of tungsten in the fabricated samples, experiments were conducted using 100 g NaCI, 30 g PET, and 0.5 g TiO2 without the presence of WO3, and the process was conducted as described above to obtain NTC820. The synthesis parameters are presented in Table 3. Figure 10 illustrates the process used for the preparation of W-doped NTC samples.

[0602] Table 3. Parameters involved in the synthesis of samples.

[0603]

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[0605]

[0606] Mechano-thermo-chemical preparation

[0607] Mechanical ball milling treatment was employed on TiO2 and WO3 powders with equal mass ratios using a high-energy planetary ball mill machine. Figure 11 shows the XRD pattern of the ball-milled sample, where Ti02+ WO3constitutes 3.2% of the total precursor mass. The broadening of the XRD peaks for both oxides, caused by the ball milling process, is clearly evident. Additionally, some weak diffraction peaks of the original oxides have even disappeared. These results indicate that the crystal lattice structure of the oxides become partially disordered through the mechano-chemical process applied. The ball-milled oxide was used as the precursor in the molten salt treatment process at 820 and 900 °C, as shown in Figure 10. The XRD patterns of W-doped-NTC820-3.2 and W-doped-NTC900-3.2 obtained after the molten sat treatment are shown in Figure 12a, from which the presence of sodium titanate phases, namely Na4TisOi2 and Nao 23 O2, are evident. The diffraction peaks of W-doped-NTC820-3.2 can be observed at 20 values of 21.38°, 33.65°, 34.17°, 38.70°, 48.72°, 51.34°, 53.41°, 60.48°, 61.53°, and 70.73° assigned to the (011), (110), (013), (2-12), (023), (114), (211), (213), (106), (220) crystal planes of hexagonal-Na4Ti5Oi2 (ICCD#00-052-1814), respectively. Moreover, the peak observed at 20 = 44.71° corresponding to the (60-1) plans of monoclinic -Nao.23Ti02 (ICCD#00-022-1404). In the XRD pattern of W-doped NTC900-3.2 (Figure 12a), the peaks related to Nao.23Ti02 can be seen at 20 = 24.36°, 28.87° and 47.25°, corresponding to the (110), (002) and (020) planes of Nao.23Ti02 (ICCD#00-022-1404), respectively. In comparison with W-doped NTC820, only very weak diffractions peaks associated with Nao.23Ti02 can be found W-doped NTC900. Also, there is no obvious diffraction peak related to carbon in the W-doped-NTC820 (TiO2 / WO3=3.2 wt%) and W-doped-NTC900 diffraction patterns, indicating that the carbon is present in the material has a rather disordered structure. Raman spectra of samples (Figure 12b) exhibit the Raman D peak at around 1333 cm1and the Raman G peak at around 1594 cm1, confirming the presence of carbon. The ID / IG values of 1.09 and 1.18 could be obtained for the W-doped-NTC820-3.2 and W-doped-NTC900-3.2, respectively. This indicate slightly higher level of defects in the carbon phase present in the latter. The Raman spectrum of the W-doped-NTC820-3.2 shows peaks belonging to Ti-0 stretching vibration at 141 and 194 cm1, and Ti-O-Na vibration at 282 cm1. Likewise, W-doped-NTC900-3.2 exhibits characteristic peaks belonging to Ti-0 stretching vibration at 893 cm1and Ti-O-Na vibration at 277, 437 and 638 cm1). The XRD and Raman analyses indicate that both samples exhibit identical phases, namely Na4TisOi2, Nao.23Ti02 and carbon. However, the quantity of phases is different in the two samples, with lower quantity of Nao 23 O2 in W- 63P / 91661

[0608] doped NTC900. Furthermore, the carbon phase is more defective in this sample.

[0609] Example 9. Morphological characterization of W-doped-NTC samples

[0610] W-doped-NTC820-3.2 and W-doped-NTC900-3.2 prepared according to the Example 8 were subjected to SEM, and the results are exhibited in Figure 13. According to Figures 13a-c, W-doped-NTC820-3.2 has a textured surface comprising lamellar structures, containing carbon, oxygen, sodium and titanium. The EDS map analysis of Figure 13c suggests that the sample comprises sodium titanates decorated on carbon substrate. Figure 3d illustrates the SEM micrograph of W-doped-NTC900-3.2, exhibiting the presence of sheet-like and rod-like structures. EDS elemental analysis recorded on atypical sheet-like and rod-like particles are shown in Figure 3i and ii, demonstrating the presence of 0 (13.99 at%), Na (2.15 at%) and Ti (3.37 at%) in sheet-like particle, and C (79.86 at%), 0 (14.51 at%), Na (2.71 at%), and Ti (3.45 at%) in the rod-like particle. These results suggest the similarity between the chemical composition of both structures, with the presence of carbon only in the rod-like particles.

[0611] This observation suggests that the presence of carbon could lead to the surface reduction of sodium titanate particles, providing the driving force for the solid-state growth of the crystals.

[0612] The dye removal experiments, discussed in the next example showed the superior performance of W-doped-NTC820-3.2. TEM micrographs of this sample are shown in Figure 14. These micrographs suggest the presence of sodium titanates as semi-spherical particles, with various sizes in the range of 10 nm to 150 nm located on the surface of the carbon phase. As shown in Figure 4d, the semi-spherical particles could be characterized by the presence of lattice fringes with an interlayer spacing with value of 0.46 nm corresponding to the (110) crystalline planes of Na is012. Figure 14b, exhibits a high resolution TEM micrograph of the carbon phase, according to which the semi-crystalline nature of the material and the presence of pores with various sizes, for instance 3 nm to 10 nm can be observed. The nitrogen adsorption and desorption isotherms and the pore size structure of samples are shown in Figures 4e and 4f, respectively. The isotherms show a type IV isotherms with a type-Hs hysteresis loop, implying the presence of mesoporous nanostructures. The specific surface area, average pore diameter and the maximum pore volume of W-doped-NTC820-3.2 were obtained to be 713.6 m2 / g, 3.96 nm and 0.144 cm3 / g, respectively. These values for W-doped-NTC900-3.2 were found to be 749.8 m2g1, 4.14 nm and 0.083 cm3g1, respectively. These results suggest the high specific surface area and the presence of well-developed pore structure in both samples, with higher pore volume recorded on W-doped-NTC820-3.2. It is worth noting that large specific surface area can provide abundant active sites for adsorption process and Fenton-like reactions, and developed pore structures can also enhance mass transfer within nanostructures of nanocomposites.

[0613] 64P / 91661

[0614] Example 10. Surface characterization of W-doped-NTC samples

[0615] XPS spectra of the initial TiC>2 and W-doped-NTC samples prepared according to the Example 8 are shown in Figure 15. As depicted in the full survey XPS spectra (Figures15b and c), in addition to the main peaks of C 1s, 0 1s, Ti 2p and Na 1s, a weak peak could also be detected near 37.0 eV, which can be assigned to W 4f, indicating that the tungsten was successfully doped into both samples.

[0616] The surface chemical composition of the W-doped-NTC820-3.2 and W-doped-NTC900-3.2 are shown in Table 4.

[0617] Table 4. The surface chemical composition of the W-doped-NTC820-3.2 and W-doped-NTC900-3.2 (at.%).

[0618]

[0619] As can be seen, the elemental composition in both samples is similar. The high-resolution Ti 2p peaks in W-doped-NTC820-3.2 and W-doped-NTC900-3.2 are shown in Figures 15b-1 and 15c-1 , respectively. As shown in Figure 5a- 1 , two peaks cold be fitted at 458.31 and 464.03 eV, corresponding to Ti 2ps / 2 and Ti 2pi / 2 of TiCh, indicating that Ti element is comprised of Ti4+ions. Compared to TO2, both W-doped-NTC820-3.2 and W-doped-NTC900-3.2 exhibit a positive shift of 1.37 eV and 1.07 eV at Ti 2p3 / 2, as well as 1.35 eV and 0.95 eV at Ti 2pi / 2, respectively. This shift is attributed to the electron transfer from the Ti and O to the alkali metal, leading to a reduction in the valence state of the Ti element. The W 4f peak of W-doped-NTC820-3.2 at 38.20 and 36.39 eV are attributed to W6+4fs / 2 and 4f? / 2, respectively. Another peak was fitted at 31.08 eV, which is related to metallic W, suggesting the surface reduction oxides into metallic state, which can contribute to enhancing the conductivity of the samples. The 0 1s peaks of the TiCh, W-doped-NTC820-3.2 and W-doped-NTC900-3.2 are presented in Figures 5a-2, b-2 and c-2, respectively. The peak at 529.52 eV is ascribed to the crystal lattice oxygen, indicative of O2- in oxygen-titanium bonds within the TO2, while the minor peak at 531.33 eV can be associated with surface hydroxyl groups. The peak at 530.08, 531.18, 532.18 and 534.18 eV recorded on the W-doped-NTC820-3.2 are attributed to the oxygen of metallic oxides, OH present in the surface hydroxyl groups, C=O and H2O adsorbed on the surfaces of the agent, respectively. These oxygen functional groups can increase the active site to promote the H2O2 activation forming *OH, thereby improving the hydrophilicity of the catalyst, and the electron and mass transfer process.

[0620] 65P / 91661

[0621] As can be seen in Figures 15b-3, the C 1s XPS spectrum of the W-doped-NTC820-3.2 catalyst can be divided into three peaks at 284.8, 285.98 and 289.68 eV, corresponding to the -C=C, -C-C- and -C=0, respectively. The 0 1s and C 1s peaks recorded on the W-doped-NTC900-3.2 are similar to those of the W-doped-NTC820-3.2. Finally, the sodium peak at 1071.78 eV in both samples can be related to the sodium cation of the titanate structure (Na-0).

[0622] Example 11. Characterization of oxygen vacancies of W-doped-NTC samples

[0623] The presence of oxygen vacancy (OV) in a catalyst is known to be able to regulate the electronic structure of the material, forming active sites which can improve the catalytic performance. Therefore, a higher number of Ovs can be beneficial to improve the adsorption and catalytic performance of catalysts. The successful introduction of OVs in W-doped-NTC samples prepared in this study was confirmed using EPR. As presented in Figure 16i. As shown, the signals associated with OVs could be detected in both samples at g = 2.005, indicating that presence of OVs in these materials. Moreover, the signal related to OVs is more intense in W-doped-NTC820-3.2. The greater level of OVs in this this sample can contribute to its greater adsorption and catalytic performance.

[0624] Example 12. Adsorption-coupled Fenton-like catalytic performance of W-doped-NTC samples Bifunctional adsorbent and Fenton-like catalysts prepared based on the Example 8 (W-doped-Na4TisOi2 / Nao 23TiO2@carbon) were evaluated by the removal of crystal violet from its solution in the absence and presence of H2O2. The results obtained are summarized in Figure 16a, where Ct / Co represents the normalized concentration of the dye in solution over time. Co is the initial dye concentration before treatment, and Ct is the dye concentration at time t during the adsorption or catalytic degradation process.

[0625] As can be seen, H2O2 (7.3 g / L) cannot directly oxidize CV (100 mg / L), exhibiting no significant change in the CV concentration in the solution even after 180 min of exposure. Furthermore, in the absence of hydrogen peroxide and relying solely on adsorption, the NTC820, W-doped-NTC820-3.2 and W-doped-NTC900-3.2 show CV removal rates of 31.5%, 112 and 61.6% within 180 min, respectively. As can be seen in Figure 16a, the crystal violet degradation efficiency was recorded at 36.7%, 98.4% and 84.9% for the NTC82O / H2O2, W-doped-NTC82O-3.2 / H2O2 and W-doped-NTC900-3.2 / H202 within 180 min, respectively. This demonstrate that the introduction of tungsten can extensively elevate the ability of the NTC820 / H2O2 system to oxidize CV.

[0626] Combining the results of EPR (Figure 16i) and BET (Figure 14f), it is evident that the W-doped NTC820-3.2 possesses abundant adsorption sites and oxygen vacancies, which not only contribute to its outstanding adsorption performance but also enhance its catalytic activity.

[0627] Additionally, in the presence of H2O2, the removal of CV by the NTC820, W-doped NTC820-3.2 and W-doped

[0628] 66P / 91661

[0629] NTC900-3.2 follows the pseudo-first-order reaction kinetics, with reaction rate constants of 0.00088, 0.02105 and 0.00839 min1respectively, as exhibited in Fig. 16b. This observation demonstrates that the dye removal rate of CV by W-doped NTC820-3.2 is 2.5 times that of W-doped NTC900-3.2, indicating that the former exhibits a highly efficient combination of adsorption and Fenton-like catalytic performance.

[0630] The considerably lower reaction rate constant of NTC82O / H2O2 (0.00088 min1) than that of W-doped NTC820-3.2 (0.02105 min1) is evident, suggesting that the presence of tungsten could boost both adsorption and Fenton-like ability of sample. As can be seen, the adsorption and Fenton-like / adsorption CV removal performances of NTC820 are 29.8% (71.6 mg / g) and 36.7% (89.1 mg / g) within 180 min, respectively, indicating that limited Fenton-like catalytic performance could be achieved without tungsten doping at NTC sample prepared at 820°C. Therefore, these observations confirm the synergistic effects of tungsten doping in terms of enhanced adsorption and Fenton-like catalytic properties observed in W-doped NTC820-3.2. comparing to NTC820.

[0631] Example 13. EPR spectroscopy of W-doped-NTC samples

[0632] As can be seen in Fig. 16a, the adsorption (180.5 mg / g) and Fenton like catalytic / adsorption (245.9 mg / g) performances of W-doped NTC820-3.2 are greater than those of W-doped NTC8900 recorded at 153.9 mg / g and 212.2 mg / g, respectively. To shed light on the reason behind this observation, EPR spectroscopy was conducted on samples, and the results are shown in Figure 16i. As can be observed, the EPR signal related to the oxygen vacancy in the W-doped-NTC820-3.2 at g=2.005 is stronger than that of W-doped-NTC900-3.2, suggesting a higher concentration of oxygen vacancies in the former. These oxygen vacancies play a crucial role in Fenton reactions, enhancing the activation of H202and subsequently increasing the efficiency of hydroxyl radical (-OH) generation, thereby improving dye degradation efficiency. Additionally, although the BET surface area of W-doped NTC820-3.2 (713.6 m2 / g) is close to that of W-doped NTC900-3.2 (749.8 m2 / g), but the pore volume of W-doped NTC820-3.2 (0.144 cm3 / g) is significantly higher than that of W-doped NTC900-3.2 (0.083 cm3 / g). This implies that W-doped-NTC820-3.2 possesses more active sites available for interaction with pollutants. Experimental results obtained confirm that, in addition to adsorption (180.5 mg / g), the agent also exhibits an enhanced combined Fenton-like degradation / adsorption activity (245.9 mg / g) within the 180 min of exposure at 40 mg / L catalyst dosage. The synergistic effects of adsorption and Fenton-like degradation significantly enhanced the dye removal efficiency of the agent (245.9 mg / g).

[0633] Example 14. Adsorption performance of W-doped-NTC820-3.2 under various parameters

[0634] The adsorption performances of W-doped-NTC820-3.2, prepared based on the Example 8 under various parameters were studied. As shown in Figure 16c, increasing the dosage of W-doped-NTC820-3.2 from 40

[0635] 67P / 91661

[0636] mg / L to 80 mg / L significantly enhanced the CV removal performance, reaching to 98.7% (123.3 mg / g) within 150 min. This is because more adsorption sites can be provided at greater concentrations of adsorbent, resulting in an increased dye removal rate. It is evident from Figure 9d that an increase in dye concentration from 100 to 150 mg / L leads to a decrease in removal rate from 96.9% (138.5 mg / g) to 74.0% (105.8 mg / g) within 240 min exposure.

[0637] Further, the adsorption experiments were conducted using W-doped-NTC820-3.2 across different pH values, and the result is show in Figure 16e, demonstrating a slight improvement in the CV adsorption performance of the agent as pH increases from 4.0 to 9.0, with the removal efficiency rising from 85.5% (122.2 mg / g) to 92.9% (162.9 mg / g) within 240 min of adsorption in the absence of H2O2. The primary reason for this observation is that under acidic conditions, the solution contains a high concentration of H+ions, competing with the cationic dye (CV) for adsorption sites, thereby reducing the adsorption capacity of the material.

[0638] Furthermore, the values of surface potential of W-doped-NTC820-3.2 were detected by zeta potential under different pH values, and found to be negative within the pH range of 4.0-9.0. Given that crystal violet is a cationic dye, this negative charge promotes stronger adsorption interactions.

[0639] Temperature also can also play a critical role in influencing adsorption efficiency. Figure 16f shows the influence of solution temperature on the adsorption process. As can be seen, the adsorption efficiency of W-doped-NTC820-3.2 increases from 84.3% (120.6 mg / g) to 96.3% (137.5 mg / g) with the temperature increasing from 23 to 45 °C within 90 min. The enhancement in adsorption of CV onto W-doped-NTC820-3.2 at elevated temperatures suggests that the process is endothermic favoured at higher temperatures. The CV adsorption performances of W-doped-NTC820-3.2 under various conditions shown in Figures 16c-6f are shown in Table 2. These findings highlight the practical significance of using W-doped-NTC820-3.2 for the removal of dyes in complex environmental wastewater applications.

[0640] Table 5. Adsorption performance of W-doped-NTC820-3.2 under various adsorption assay conditions (including adsorbent dosage, CV concentration, solution pH and temperature)

[0641]

[0642] 68P / 91661

[0643]

[0644] Example 15. Preparation and dye removal performances of alternative W-doped-NTC820 samples As explained in pervious examples, two factors contribute to the CV removal performance of W-doped-NTC820-3.2, namely adsorption, and the oxidative decomposition facilitated by Fenton-like catalytic activity of the agent. In this example, the performances of alternative W-doped-NTC820 samples, namely W-doped-NTC820-1.6, W-doped-NTC820-6.3, W-doped-NTC820-9.1 and W-doped-NTC820-11.8 (Table 3) are disclosed. In these samples, the mass fraction of (TiCh + WO3) relative to the mass of TO2+WO3+PET precursor were 1.6%, 6.3%, 9.1% and 11.8%, respectively (see Table 3). The XRD patterns of the samples obtained are shown in Figure 17a. Accordingly, when the mass fraction of (TiC>2 +WO3) relative to the mass of TO2+WO3+PET precursor used for the preparation of W-doped-NTC820 sample is increased from 6.3% to 11.8% and beyond, the TiC>2 (rutile) becomes stable as the main phase, and these samples do not exhibit a considerable Fenton-like catalytic properties in the presence of H2O2, as shown in Figure 17b. Without being restricted by mechanism, titanium dioxide phase does not exhibit and noticeable Fenton-like catalytic performance and it is difficult to catalyse H2O2 to produce oxidation free radicals

[0645] As shown in Figure 17b, increasing the TO2+WO3 loading amount from 1.6% to 3.2 wt% significantly improved the dye removal efficiency from 78.6% (157.2 mg / g) to 98.8% (197.4 mg / g) within 120 min of exposure. Without being restricted by a specific reasoning, this suggests that a higher sodium titanate concentration in the NTC enhances the dye removal performance of the sample. However, further increasing the loading amount beyond the optimal value of 3.2 wt% led to a decrease in efficiency due to the stabilization of TiO2. The dye removal efficiency dropped to 55.8% (111.5 mg / g) as the loading amount increased from 3.2 wt% to 11.9 wt%.

[0646] It is believed that by significantly varying the proportion of raw materials beyond the values reported in Table 3 and carefully controlling the processing conditions, including temperature, heating rate, heating duration, heating atmosphere, type of carbon precursor, type and composition of salt, and type and composition of

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[0648] transition metal oxide, various samples with different adsorbent and catalytic activities can be produced, all of which fall within the scope of this disclosure.

[0649] Example 16. Effect of agent dosage on CV removal

[0650] As depicted in Figure 18a, the effect of catalyst dosage (30-70 mg) on CV dye degradation was investigated. It was observed that CV dye degradation positively correlated with the dosage of W-doped-NTC820-3.2. When the catalyst dosage was 30, 40, and 50 mg, the degradation efficiencies of CV were 87.1 %, 90.7%, and 96.7% after 180 min, respectively. Furthermore, increasing the catalyst dosage to 80 mg enhanced the degradation efficiency to 99.9% within 90 min. This improvement can be attributed to the higher amount of catalyst providing more active sites and enhancing the effective contact between the W-doped-NTC and H202, thus producing more hydroxyl radicals. Figure 18a illustrates the impact of varying catalyst dosages, ranging from 30 to 70 mg, on the degradation efficiency of CV dye. The data shows a clear correlation between increased dosages of W-doped-NTC820-3.2 and its enhanced degradation efficiency. Specifically, catalyst dosages of 30 mg and 40 mg resulted in degradation efficiencies of 73.5% and 88.3%, respectively, after 180 min. Increasing the catalyst dosage to 50 mg significantly boosted the degradation efficiency to 99.2% within just 150 min. Moreover, further increments in catalyst dosage to 60 mg and 70 mg achieved nearly complete degradation of crystal violet in even shorter times of 90 and 60 min, respectively, both reaching degradation efficiencies of 99.2%.

[0651] Example 17. Effect of H202Dosage

[0652] In some embodiments of this disclosure, H202acts as the driving force in Fenton / Fenton-like reactions and serves as the source of hydroxyl radicals generated through the Fenton reaction. The effect of different H202dosages on the degradation efficiency of CV was studied to determine the optimal conditions for maximizing degradation effectiveness.

[0653] For this, 80 mg W-doped-NTC820-3.2 and different H2O2 dosage were added into 100 mL CV solution with a concentration of 100 mg / L, and the dye removal results are depicted in Figure 8b. It was found that the H2O2 volume of 0.30 g / L achieved the highest performance, resulting in approximately 99.0% dye removal within 40 min. Increasing the addition of H2O2 to 3.7 g / L mL did not significantly change the efficiency, suggesting a saturation point where further H2O2 does not enhance free radical formation or dye removal.

[0654] Notably, increasing the H202volume to 5.5 mL resulted in a degradation efficiency of 97.0% after 120 minutes, which was slightly lower than the adsorption performance of W-doped NTC820-3.2 for CV. This suggests that the reaction environment may become oversaturated, causing H202to act as a free radical scavenger.

[0655] Without being restricted to a specific mechanism, this phenomenon likely occurs due to the excessive breakdown of hydrogen peroxide into water and oxygen, which limits the availability of hydroxyl radicals

[0656] 70P / 91661

[0657] necessary for effective dye degradation. Another possible explanation is that the high concentration of hydrogen peroxide is rapidly consumed at the beginning of the reaction, reducing its effective concentration overtime and thereby impacting the overall reaction efficiency.

[0658] It is anticipated that the catalytic performance of W-doped NTC820-3.2 can be activated at various H202dosages, including but not limited to a maximum of 5.0 g / L, 4.5 g / L, 4.0 g / L, 3.7 g / L, 3.5 g / L, 3.2 g / L, 3.0 g / L, 2.8 g / L, 2.5 g / L, 2.2 g / L, 2.0 g / L, 1.5 g / L, and a minimum of 1.0 g / L, 0.5 g / L, and 0.01 g / L.

[0659] Example 18. Effect of initial dye concentration

[0660] Figure 18c illustrates the effect of the initial CV concentration (100, 125, 150, 175, and 200 mg / L) on the Fentonlike catalytic performance of W-doped NTC820-3.2, with a catalyst dosage of 70 mg / L and an H202dosage of 0.30 g / L. As shown, the degradation efficiency significantly decreased as the CV concentration increased. Specifically, when the CV concentration increased from 100 mg / L to 200 mg / L, the removal rate declined from 99.1% (141.5 mg / g) within 40 minutes to 81.5% (91.8 mg / g) within 120 minutes. This reduction in removal efficiency is attributed to the saturation of the catalyst's active sites by CV dye molecules at higher concentrations, which limits the production of hydroxyl radicals. Additionally, a higher CV concentration may reduce turbulence and cavitation within the solution, thereby decreasing the generation of reactive radicals and lowering the mass transfer rate between the solid and liquid phases.

[0661] Example 19. Effect of pH

[0662] Without being restricted to any specific mechanism, it is known that in Fenton and Fenton-like processes, pH is a critical factor influencing catalyst performance, as it affects both the surface potential of the catalyst and its interaction with H2O2. While the conventional Fenton process is limited to a narrow pH range (pH 2.5— 3.5), the W-doped-NTC catalyst demonstrates exceptional catalytic activity across a broader pH range (4.0-9.0), as shown in Figure 18d.

[0663] As depicted, the CV degradation efficiency of the catalyst at a low pH of 4.0 is 71.8% (103.2 mg / g) within 40 minutes. However, increasing the pH to 9.0 enhances the degradation efficiency to 99.1% (141.5 mg / g) within the same duration. Without being restricted to any specific mechanism, this improvement is believed to result from the competitive adsorption between CV (a cationic dye) and H+ions under acidic conditions, which reduces dye adsorption on the catalyst surface and thereby lowers catalytic efficiency.

[0664] Furthermore, the zeta potential of W-doped NTC-3.2 was measured at different pH levels of 4.0, 7.0, and 9.0, and found to be -7.4 mV, -14.3 mV, and -17.7 mV, respectively. The negative surface potential of the catalyst over a wide pH range (4.0-9.0) facilitates electrostatic attraction between the negatively charged catalyst surface and positively charged dye molecules, particularly under alkaline conditions. This property enables the

[0665] 71P / 91661

[0666] catalyst to maintain high efficiency across a broad initial pH range, overcoming the limitations of the conventional Fenton reaction’s narrow pH window and establishing it as an effective catalyst for the decomposition of organic compounds.

[0667] Example 20. Effect of Temperature

[0668] Figure 18e illustrates the effect of CV solution temperature on the dye removal performance of W-doped NTC-3.2, with efficiency evaluated over a temperature range of 20°C to 40°C. As depicted, elevated temperatures promote the Fenton-like reaction process, primarily by increasing molecular collisions, thereby enabling more molecules to acquire the necessary energy to overcome the activation barrier. This enhancement in reaction kinetics facilitates the Fenton-like reaction, leading to improved dye degradation efficiency.

[0669] A significant improvement in degradation efficiency is observed with rising solution temperature. Specifically, as the temperature increases from 20°C to 40°C, the dye removal rate substantially improves from 46.9% (117.5 mg / g) to 94.0% (235.1 mg / g) within 30 minutes. This marked increase in the reaction rate results in a dramatic reduction in overall reaction time, decreasing from 180 minutes to just 40 minutes, highlighting the strong temperature dependence of the degradation process.

[0670] Furthermore, the total activation energy (Ea) for the adsorption and Fenton-like degradation of the dye using W-doped-NTC820 (TiO2 / WO3=3.2 wt%) could calculated to be 29.14 and 86.13 kJ mol1, respectively, according to the Arrhenius equation:

[0671]

[0672] Where, Ki is the reaction rate constant of the first-order reaction kinetic model; R is the gas constant (8.314 J mol1K1); A represents a constant; Eais the activation energy (kJ mol1) and T is the reaction temperature (K). The results are presented in Figures 16h and 18h. As shown, the data indicate that the Fenton-like reactions are more sensitive to temperature variations than the adsorption processes.

[0673] In Example 12, it was demonstrated that the effect of temperature on the CV adsorption process results in a reaction rate constant that is 2.5 times higher at 40°C (0.1662 x 102min1) than at 20°C (0.00659 x 102min-1). Furthermore, as illustrated in Figure 18g, at 40°C, the reaction rate constant (9.57 x 102min1) is approximately 11 times greater than at 20°C (0.84 x 102min-1), highlighting the significant impact of temperature on the reaction kinetics.

[0674] These results are significant not only in the realm of water treatment but also offer sustainable and efficient solutions for environmental pollution management.

[0675] Example 21. Cycling performance of W-doped-NTC820-3.2

[0676] 72P / 91661

[0677] Without being bound by mechanism, the physicochemical stability of adsorbents is crucial for their potential industrial applications, as these properties enable the regeneration of the agents after use in contamination removal processes. NTC and W-doped-NTC samples are bifunctional adsorbent and Fenton-like catalyst capable of continuously adsorbing and degrading pollutants from the environment in the presence of H2O2 In the absence of H2O2, the agent still functions effectively; however, the exhausted samples require regeneration before they can be reused.

[0678] A regeneration assay was conducted on the used W-doped-NTC820-3.2 after it had been saturated with dye molecules. For regeneration, the adsorbent was separated from the solution by vacuum filtration following saturation, and then dried in an oven for 6 hours. The exhausted adsorbent was subsequently heated in air at a rate of 5 °C / min to 400 °C, with a dwell time at the maximum temperature of one second, before being cooled to room temperature in an air atmosphere. The regenerated material was designated as R1.

[0679] Without being restricted to a specific thermal treatment temperature, such as 400 °C, heating the adsorbent to a sufficiently high temperature promotes the decomposition of organic molecules adsorbed on the surface of the adsorbent, thereby regenerating it. For an efficient regeneration process, the atmosphere can be air; however, it may also be conducted in an inert atmosphere (e.g. argon), nitrogen or a reducing atmosphere, although such atmospheres would incur higher costs compared to the use of freely available air.

[0680] The optimal heating temperature depends on the type of organic pollutants but is generally believed that heating at 400 °C effectively decomposes most organic components. In other embodiments of the disclosure, the thermal treatment can be conducted at temperatures ranging from 150 °C to 700 °C, with a dwell time at the maximum temperature ranging from 1 second to 10 hours. However, to optimize cost-effectiveness, it is preferable to limit the dwell time to between 1 second and 1 hour, or even between 1 second and 30 minutes. The heating rate can range from 1 °C / min to 200 °C / min.

[0681] A cycling test was performed on W-doped-NTC820-3.2 under the same conditions, using 70 mg / L of adsorbent and the CV solution of 100 mg / L. After the first thermal regeneration, the degradation efficiency of R1 towards CV was recorded at 85.8% (122.6 mg / g) within 120 minutes of Fenton-like degradation, showing a slight decrease compared to the initial W-doped-NTC820-3.3, which achieved 99.1% (141.5 mg / g). R1 was then subjected to another cycle of recovery and regeneration to produce R2. The degradation performance of R2 was assessed under identical conditions. The results indicated that the degradation efficiency of R2 towards CV further decreased to 65.96% (94.1 mg / g) within 120 minutes. Without being bound by mechanism, this decline in degradation efficiency can be primarily attributed to the occupation of adsorbent pores by inorganic residues produced by the decomposition of dye molecules during the regeneration process. Nevertheless, the

[0682] 73P / 91661

[0683] agent demonstrated excellent regeneration performance, supporting its potential for a circular economy. To evaluate the role of reactive oxygen species (ROS) in the Fenton-like performance of W-doped-NTC820-3.3, a series of ROS scavenging experiments were conducted. Isopropanol (IPA), benzophenone (BQ), and furfuryl alcohol (FA) were used as radical quenching agents for -OH, -02-, and102active radicals, respectively, to define their roles in the degradation of CV. The free radical capture experiments involved adding 70 mg / L of the agent, 0.3 g / L of H2O2, and various radical scavengers (IPA: 5 mg / L, BQ: 1.3 mg / L, and FA: 5 mL / L) to a 100 mg / L CV solution, and the results are shown in Figure 18f. The results indicate that IPA and BQ slightly reduced CV degradation efficiency to 88.4% (126.3 mg / g) and 96.5% (137.8 mg / g), respectively, suggesting that -OH and -02-are not the dominant ROS. However, FA significantly lowered the CV degradation efficiency to 52.9% (75.6 mg / g), implying that102plays a crucial role in the Fenton-like reaction process. Additionally, FA likely competes with CV for adsorption on the catalyst surface, further reducing the agent's adsorption performance. In particular, in the presence of FA and H2O2, the degradation efficiency of CV was 52.9% (75.6 mg / g), which was lower than that without radical scavengers; agent + H2O2: 99.1 % (141.5 mg / g) and adsorption performance (69.56 mg / g) after 40 min. Thus, FA not only captures free radicals but also competitively adsorbs onto the agent surface along with CV, reducing the CV adsorption performance of the agent. The scavenger experiments clearly indicate that -OH, -02-, and102influence the degradation efficiency, with102playing a particularly significant role in the Fenton-like reaction process.

[0684] Example 22. Quantification of Oxygen Vacancy Level

[0685] Since oxygen vacancies in oxides often trap electrons or induce paramagnetic centres, their presence enhances the EPR response. As such, the appearance of a rhombic EPR signal in oxides with g-values in the range of around 2.000-2.010 (with an average around 2.005) often corresponds to oxygen vacancies. The signals within this range can be attributed to peak signals of g and gzz. The gwcomponent can also be associated with the point where the first derivative of the absorption signal crosses zero intensity (i.e., the zerocrossing point). Higher EPR signal intensities at gxxand gzz(i.e., stronger peaks at g or gzz) indicate a greater number of unpaired electrons, which correlates with an increased presence of oxygen vacancies in the sample. In particular, gzzis often associated with the most stable direction of the paramagnetic defect and is particularly sensitive to oxygen vacancies.

[0686] TO exemplify the presence of oxygen vacancy and their dependence to the thermal treatment used during their preparation, the W-doped-NTC820 and W-doped-NTC900 prepared in the Example 8 were subjected to EPR examination, and the results obtained are shown in Figures 19a and 19b, respectively. The values of g and

[0687] 74intensity corresponding to the signal indicative of oxygen vacancy in the g-value range of 2.000-2.010 are shown in Table 5.

[0688] Table 5. The values of g and intensity corresponding to the signal indicative of oxygen vacancy.

[0689] < < < <

[0690]

[0691] These observations indicate that the oxide compounds prepared using the methods of this invention contain oxygen vacancies, as evidenced by the presence of two signals in their EPR spectra within the g-value range of 2.000-2.010, corresponding to two peaks (gzzand gxx). The gzzpeak has a g-value between 2.005 and 2.007, preferably around 2.006, while the gxxpeak falls within the range of 2.002 to 2.005. The gyyvalue is between 2.004 and 2.009.

[0692] As can be observed from Figure 19, the samples have gzz intensities in the range 0.08 and 0.13 (a.u.) Also, the samples have gxx intensities in the range -0.17 and -0.10 (a.u.).

[0693] As observed from Figure 19, in the sample prepared at 820 °C, the gzzand gxx peaks exhibit higher intensities compared to those of the samples prepared at 900°C, indicating that the former has higher levels of oxygen vacancies. According to Figure 14a, the sample prepared at 820 °C contains semi-spherical sodium titanate nanoparticles embedded in the carbon phase. Without being restricted by a specific mechanism, the higher level of oxygen vacancies in this sample corresponds to the effective partial reduction of the oxide by carbon layers tightly attached to or surrounding the nanoparticles. These oxygen vacancies, without being confined to a particular mechanism, act as the driving force for the one-directional growth of sodium titanates at higher temperatures, such as 900°C, in order to reduce the level of oxygen vacancy in the sample. As a result, rodlike sodium titanate particles coated with carbon layers are formed, exhibiting a lower level of oxygen vacancies compared to the sample prepared at lower temperatures.

[0694] Example 23. Quantification of Oxygen Vacancy Level in NTC

[0695] To exemplify the presence of oxygen vacancy in the NTC sample prepared in Example 1, the sample was subjected to EPR examination, and the result obtained is shown in Figure 20. The values of g and intensity corresponding to the signal indicative of oxygen vacancy in the g-value range 2.000-2.010 are shown in Table 6.

[0696] Table 6. The values of g and intensity corresponding to the EPR signal indicative of oxygen vacancy in NTC.

[0697] 75

[0698] < <

[0699]

[0700] These observations indicate that NTC contains oxygen vacancies, as evidenced by the presence of two signals in its EPR spectrum within the g-value range 2.000-2.010, corresponding to two peaks (gzzand gxx). The EPR spectrum shows a gzzpeak value and intensity of around 2.006 and 0.15 (a.u.), respectfully; and a gxxpeak value and intensity of 2.004 and -0.15, respectively.

[0701] Example 24: Preparation of Fe2.1sTio.42O4 / Na4Ti5O12 / Fe3C-carbon core shell nanostructure

[0702] An equimolar mixture of Ti02(rutile phase, Aladdin, CAS: 13463-67-7, 99.8%) and Fe203(Aladdin, CAS: 1309-37-1, 2399.7%) was ball-milled for 20 h using a powder-to-ball mass ratio of 1 :20. Steel balls with diameters of 5, 8 and 10 mm were employed in a mass ratio of 5:3:2 within a 100 mL steel jar. The milling process was carried out at 300 rpm in cycles of 60 min milling followed by 10 min rest.

[0703] The resulting ball-milled powder (1 g) was subsequently mixed with 30 g of waste PET bottle pieces and 100 g of NaCI (Aladdin, CAS: 7647-14-5, 99.5%). The mixture was loaded into an alumina crucible covered with an alumina lid and thermally treated in a resistance furnace at 900 °C with a heating rate of 4 °C min-1. The samples were maintained at the target temperature for 1 h in air and then furnace-cooled to approximately 25 °C. After thermal treatment, the obtained material was rinsed with deionized water to dissolve the salt, followed by vacuum filtration. The collected solids were dried at 100 °C, after which the final product was collected and denoted as NFTC.

[0704] Figure 21(a) presents the XRD pattern of NFTC, revealing the presence of Fe2.1sTio.42O4, Na4Ti50i2, Fe3C and PET-derived carbon, with the carbon phase coating the external surfaces of the inorganic components. Maghemite titanian (Fe2.1sTio.42O4) and Fe3C (cementite) are ferromagnetic; therefore, the composite exhibits soft magnetic properties. VSM measurements conducted at room temperature, as shown in Figures 21(b) and 21 (c), confirm that the particles display soft ferromagnetic behaviour. The relatively low saturation magnetisation (Ms = 6.0 emu g-1) indicates significant surface spin disorder and finite-size effects, which are characteristic of particulate or nanoscale systems. In addition, the low remanence ratio (Mr / Ms~ 0.2) and moderate coercivity (Hc= 283.2 Oe) suggest easy magnetisation reversal, confirming the soft magnetic behaviour of the material. Figure 21(d) shows a TEM micrograph of NFTC, revealing the presence of nanoparticles mainly composed of Na4Ti50i2, Fe2.1sTio.42O4, and Fe3C, with particle sizes ranging from 2 to 200 nm, embedded within a carbon

[0705] 76P / 91661

[0706] matrix. The presence of PET-derived carbon coating a nanoparticle, with an average thickness of 5.3 nm, is shown in Figure 21(e). N2adsorption-desorption analysis revealed a BET specific surface area of 248.6 m2g-1, a single-point desorption total pore volume of 0.19 cm3g-1, and an average pore diameter of 3.1 nm, calculated using the 4V / A BET method.

[0707] At pH 5.68, with an H202concentration of 0.333 g L"1, a temperature of 15 °C, and an exposure time of 40 min in the dark, the combined adsorption and Fenton-like degradation of crystal violet dye by NFTC resulted in a removal capacity of 154 mg g-1. At a solution pH of 11, a temperature of 15 °C, and an exposure time of 15 min, a CV adsorption capacity of 1566 mg g-1was achieved. In the presence of H202(0.333 g L’1), the adsorption— Fenton-like removal performance further increased to 1600 mg g-1at pH 11.

[0708] The significantly higher CV removal at pH 11.0 compared with pH 5.7 is attributed to a shift from mixed adsorption-oxidation mechanisms to adsorption-dominated removal. At alkaline pH, the negatively charged NFTC surface strongly enhances electrostatic attraction and TT-TT interactions with cationic CV molecules, resulting in a substantially increased removal capacity.

[0709] Example 25: Preparation of SiO2-C core-shell nanostructure

[0710] In one embodiment, 0.4 g of silicon dioxide (Si02) nanoparticles having an average particle size of approximately 30 nm, 12 g of PET pieces obtained from water bottles, and 40 g of NaCI were combined to form a mixture. The mixture was heated to 900 °C at a heating rate of 4 °C min-1and maintained at said temperature for a dwelling time of 1 h. Following the heat treatment, the mixture was allowed to cool to room temperature. The resulting solid product, having a mass of approximately 40.43 g, was washed with deionised water to remove sodium chloride. After washing, 0.56 g of a solid material was obtained, comprising carbon-coated silicon dioxide nanoparticles. The washed material was dried yielding a final product, hereinafter referred to as Si02-C. The XRD patterns (Figure 22(a)) exhibited broad diffraction peaks, indicative of nanostructured materials. Raman spectroscopy was performed on the samples, and the resulting spectra (Figure 22(b)) showed the presence of D and G bands in SiO2-C sample characteristic of a carbon coating on the silicon dioxide nanoparticles. The intensity ratio of the D band to the G band (ID / IG) was determined to be approximately 1.06.

[0711] Nitrogen adsorption-desorption analysis demonstrates that coating Si02nanoparticles with carbon produces a material having substantially modified textural properties. The uncoated Si02nanoparticles exhibit a BET surface area of 159.6 m2g-1, a total pore volume of 0.5780 cm3g-1, and an average pore diameter of 14.49 nm. Following carbon coating, the resulting Si02-C material exhibits an increased BET surface area of 627.1

[0712] 77P / 91661

[0713] m2g-1, while the total pore volume is reduced to 0.3396 cm3g-1and the average pore diameter is reduced to 2.17 nm.

[0714] The increase in surface area in combination with the reduction in pore volume and pore size indicates that the carbon coating forms a porous carbon layer on the surface of the Si02nanoparticles. This carbon layer reduces the effective size and volume of pre-existing mesopores associated with the Si02nanoparticles and introduces a high density of smaller pores within the carbon phase. The formation of smaller pores increases the internal surface area available for adsorption or interfacial interactions while maintaining structural continuity of the composite material. Accordingly, the carbon-coated Si02nanoparticles exhibit a refined pore structure characterized by increased surface area and reduced pore size relative to uncoated Si02nanoparticles. SiO2-C exhibited a CV adsorption performance of 210.34 mg / g at pH=5.4 after corresponding to 97.8% of CV dye removal from CV solution, after 180 min of exposure.

[0715] Example 26: Preparation of aluminosilicate— c core-shell nanostructure

[0716] Example 25 was repeated, with the only difference that the silicon dioxide nanoparticles were replaced with aluminosilicate particles. Following the same mixing, thermal treatment, washing, and drying procedures described in Example 25, a solid product was obtained comprising aluminosilicate particles forming a core that is coated with a carbon shell. The resulting material comprises aluminosilicate-carbon ore-shell nanostructures, wherein the aluminosilicate core comprises aluminium silicon, and oxygen, and the carbon shell forms a continuous coating on the external surface of the aluminosilicate particles.

[0717] Example 27: Preparation of CaTiOa-C core-shell nanostructure

[0718] In one embodiment, PET pieces (30 g), calcium chloride (CaCI2, 100 g), and Ti02(1 g) were combined to form a homogeneous mixture. The mixture was transferred into an alumina crucible equipped with a lid and heated in an air atmosphere to a temperature of 900 °C at a heating rate of 4 °C / min. The temperature was maintained at 900 °C for 1 hour, after which the furnace was allowed to cool to room temperature at the same rate. The resulting solid material was washed with a sufficient amount of distilled water, followed by vacuum filtration and drying to obtain the final product. X-ray diffraction pattern of the product, as shown in Figure 23, confirms the formation of calcium titanate (CaTiO3) coated with a carbon shell. Diffraction peaks corresponding to the carbon phase are not observed in the XRD pattern, which is attributed to the nanostructured nature of the carbon phase.

[0719] In further embodiments, residual calcium carbonate present in the CaTiO3-carbon core-shell structure may be removed by washing the product with a dilute acid solution.

[0720] Example 28: Preparation of MgTiC -C core-shell nanostructure

[0721] 78P / 91661

[0722] In one embodiment, the procedure described in Example 25 is repeated, with the exception that magnesium chloride (MgCI2) is used in place of calcium chloride. All other processing conditions was maintained substantially the same. Following thermal treatment and post-processing, the resulting product comprises a magnesium titanate-carbon (MgTiO3-C) core-shell nanostructure. X-ray diffraction pattern of the product, as shown in Figure 24, confirms the formation of MgTiO3. Diffraction features attributable to the carbon shell are not readily observable in the XRD pattern, which is attributed to the nanoscale and / or partially amorphous nature of the carbon material. In further embodiments, residual magnesium oxide (MgO) present in or associated with the MgTiO3-carbon core-shell nanostructure can be partially or substantially removed by contacting the product with an acidic solution, such as a dilute inorganic acid, followed by washing and drying.

[0723] 79

Claims

1. P / 91661Claims1. A particle comprising a core and an outer layer, wherein:the outer layer comprises or consists of carbon;the core comprises at least one compound comprising: a transition metal, oxygen, and one or both of an alkali metal and an alkaline earth metal; andthe particle has a surface area of at least 200 metres squared per gram.

2. The particle according to any preceding claim, wherein the particle is for use as one or both of: an adsorbent to adsorb at least one target component such as at least one pollutant from a solution; and a catalyst in the degradation of at least one target component in a solution.

3. The particle according to any preceding claim, wherein the particle has a length, a width, and a thickness, wherein the length, the width and the thickness are mutually perpendicular, and wherein one or both of: the length is at least 2, 5 or 10 times the width; and the length is at least 2, 5 or 10 times the thickness.

4. The particle according to any preceding claim, wherein the particle has a surface area of at least 300 or 500 metres squared per gram.

5. The particle according to any preceding claim, wherein the particle has a pore volume of at least 0.2, 0.25 or 0.3 centimetres cubed per gram.

6. The particle according to any preceding claim, wherein the alkali metal is sodium.

7. The particle according to any preceding claim, wherein the transition metal is titanium.

8. The particle according to any preceding claim, wherein the at least one compound comprises sodium titanate.

9. The particle according to claim 8, wherein the at least one compound comprises one or both of Na^isOi 2 and Nao23Ti02.

10. The particle according to any preceding claim, wherein the core comprises a dopant.

11. The particle according to claim 10, wherein the dopant is or comprises a second transition metal different to the transition metal.

12. The particle according to claim 11 , wherein the second transition metal is tungsten.

13. The particle according to any preceding claim, wherein the outer layer comprises one or both of graphite and graphene.

14. A method of producing a plurality of particles, the method comprising:mixing, to form a mixture, at least:an oxide of a transition metal;80P / 91661a carbon-containing material; andone or both of an alkali metal-compound and an alkali earth metal-compound, and then heating the mixture to a first temperature, the first temperature being above a melting temperature of the carbon-containing material and above a melting temperature of the alkali metal-compound or the alkali earth metal-compound.

15. A method according to claim 14, wherein the transition metal is titanium.

16. A method according to any of claims 14 to 15, wherein the carbon-containing material is or comprises a thermoplastic.

17. A method according to any of claims 14 to 16, wherein the carbon-containing material is or comprises polyethylene terephthalate (PET).

18. A method according to any of claims 14 to 17, wherein heating the mixture to the first temperature causes a reaction, the reaction being between the oxide of the transition metal and the alkali metal-compound or the alkali earth metal-compound, to form at least one compound, the at least one compound comprising the transition metal, oxygen, and the alkali metal or the alkaline earth metal.

19. A method according to any of claims 14 to 18, wherein the first temperature is between 500 and 1500 degrees Celsius.

20. A method according to any of claims 14 to 19, wherein the step of mixing to form the mixture comprises mixing, to form the mixture, at least: the oxide of the transition metal; the carbon-containing material; the alkali metal-compound or the alkali earth metal-compound; and a dopant-containing material.

21. A method according to claim 20, wherein the dopant-containing material is an oxide of a second transition metal, the second transition metal being different to the transition metal.

22. A method according to claim 21, wherein the second transition metal is tungsten.

23. A method according to any of claims 14 to 22, wherein each of the plurality of particles is a particle according to any of claims 1 to 13.

24. A method of using particles to adsorb, and / or act as a catalyst in the degradation of, at least one target component such as at least one pollutant in a solution, each of the particles comprising a core and an outer layer, wherein:the outer layer comprises or consists of carbon; andthe core comprises at least one compound, the at least one compound comprising:a transition metal,oxygen, and81P / 91661one or both of an alkali metal and an alkaline earth metal.

25. A method according to claim 24, wherein each of the particles is a particle according to any of claims 1 to 13.82

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