Hybrid photocatalysts for decomposing synthetic chemicals and methods thereof

Abstract

A method of producing a hybrid photocatalyst and a composition of a hybrid photocatalyst are disclosed. The method comprises impregnating a carbon-containing biomass with a metal-containing compound. The impregnated biomass is subject to pyrolysis to yield the hybrid photocatalyst. The hybrid photocatalyst comprises metal oxide immobilized on a biomass-derived carbonaceous material. The metal oxide may comprise a crystalline structure. The biomass-derived carbonaceous material may comprise amorphorus carbons. An example use of the hybrid photocatalyst is in the decomposition of perfluoroalkyl and polyfluoroalkyl substances (PFAS).

Description

HYBRID PHOTOCATALYSTS FOR DECOMPOSING SYNTHETIC CHEMICALS AND METHODS THEREOFCross-Reference to Related Applications

[0001] This application claims priority from US application No. 63 / 539,152 filed 19 September 2023 and entitled IRON OXIDE / GRAPHENIC CARBON HYBRID PHOTOCATALYST FOR DECOMPOSITION OF PFAS which is hereby incorporated herein by reference for all purposes. For purposes of the United States of America, this application claims the benefit under 35 U.S.C. §119 of US application No. 63 / 539,152 filed 19 September 2023 and entitled IRON OXIDE / GRAPHENIC CARBON HYBRID PHOTOCATALYST FOR DECOMPOSITION OF PFAS which is hereby incorporated herein by reference for all purposes.Field

[0002] The invention pertains to methods of producing photocatalysts, and in particular, hybrid photocatalysts that may be used for decomposing synthetic chemicals.Background

[0003] Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluoride compounds that are known for their resistance to heat, water, and oil. PFAS are notorious for their environmental persistence and potential to bioaccumulate in living organisms, primarily due to the strong strength of their carbonfluorine bonds. Their exceedingly stable C-F bond, which has an enthalpy change AH0that is greater than about 500 kJ / mol, leads to serious environmental and health concerns, as PFAS can remain in the environment and in organisms for extended periods, raising alarms about their toxicological impacts. They have been found to bioaccumulate to toxic levels, and can persist in the environment for many years.

[0004] PFAS have gained attention due to its frequent detection at high concentrations in aquatic environments and human blood samples globally. They areone of the most frequently detected persistent organic pollutants, with a detection rate of 66% and a maximum concentration of 39 ng / L in European groundwater. Recently, rainwater has been found to contain detectable levels of four types of PFAS, including perfluorooctanoic acid (PFOA). Studies have reported that the levels of PFOA detected in rainwater samples exceed drinking water and environmental standards in several countries. PFOA has a half-life of about 2.3 years in humans and has been linked to liver damage, thyroid diseases, cancer, among others. The US Environmental Protection Agency (USEPA) has proposed a National Primary Drinking Water Regulation (NPDWR) which imposes a maximum concentration level (MCL) of 4.0 ng / L for PFOA. With growing concerns about PFAS in the environment and its health impacts, there is a need for efficient and low-cost methods for remediation.

[0005] Many PFAS compounds are resistant to conventional drinking water treatment methods, such as coagulation, flocculation, sedimentation, and filtration, due to the high-water solubilities and low vapor pressure of such compounds. Consequently, such conventional methods have proven to be inefficient in removing PFAS from contaminated water sources.

[0006] The inventors have recognised a general need for efficient and low-cost remediation methods of removing PFAS from environmental media. There is a particular need for a frugal (e.g., simple, easy, and low-cost) method of producing a photocatalyst that can decompose PFAS with high efficiency.Summary

[0007] This application has a number of aspects. These include, without limitation:• methods for producing a hybrid photocatalyst;• composition of a hybrid photocatalyst;• use of the hybrid photocatalyst to decompose synthetic chemicals such as PFAS, including any long- and short-chain PFAS such as but not limited to PFOA, TFA; and• method of decomposing synthetic chemicals.

[0008] One aspect of the invention provides a method for a producing hybridphotocatalyst. The method comprises impregnating a carbon-containing biomass feedstock with a metal-containing compound to form an impregnated biomass material, and pyrolyzing the impregnated biomass at a pyrolysis temperature to produce a hybrid photocatalyst. The hybrid photocatalyst comprises metal oxides immobilized on a biomass-derived carbonaceous material.

[0009] In some embodiments, the metal-containing compound comprises a metal ion selected from one or more transition metal ions. In some embodiments, the metalcontaining compound comprises the metal ion and a non-metallic element. The non- metallic element may for example be a halogen, sulfur, oxygen, and / or nitrogen. In some embodiments, the metal-containing compound comprises a metal complex formed by reacting the metal ion and a ligand. The ligand may for example be an organic ligand.

[0010] One aspect of the invention provides use of the hybrid photocatalyst in decomposing synthetic chemicals. In some embodiments, the synthetic chemicals comprises per- and poly-fluoroalkyl substances (PFAS). In some embodiments, the PFAS comprises perfluorooctanoic acid (PFOA) and / or perfluorooctane sulfonate (PFOS).

[0011] One aspect of the invention provides a hybrid photocatalyst comprising iron oxide immobilized on a biomass-derived carbonaceous material, wherein at least about 80wt% of the iron oxide in the hybrid photocatalyst is in the form of Fe2Oa, and in some embodiments, in the range of from about 30 wt.% to about 75 wt.%. In some embodiments, the form of Fe2Oa comprises a-Fe2C>3.

[0012] Further aspects and example embodiments are illustrated in the accompanying drawings and / or described in the following description.

[0013] It is emphasized that the invention relates to all combinations of the above features, even if these are recited in different claims.Brief Description of the Drawings

[0014] The accompanying drawings illustrate non-limiting example embodiments ofthe invention.

[0015] Figure 1 is a flow chart illustrating the steps of a method for producing hybrid photocatalysts according to an example embodiment of the invention.

[0016] Figure 2 are plots illustrating normalized decomposition efficacy (NDE) of PFOA grouped in three different PFOA initial concentrations. The error bars represent the range from the upper quartile (Q3) to the maximum value for the upper whisker and from the lower quartile (Q1 ) to the minimum value for the lower whisker.

[0017] Figure 3A is a Scanning electron microscopy (SEM) image of graphenic carbon (g-C). The scale bar is 50 pm.

[0018] Figure 3A is a SEM image of 32 wt% Fe / g-C. The scale bar is 50 pm.

[0019] Figure 3C is a magnified region showing iron oxide crystallite grown on g-C surface. The scale bar is 10 pm.

[0020] Figure 3D are powder X-ray diffraction (pXRD) patterns of pure carbon (g-C), and Fe / g-C hybrid doped with 1.6 wt% Fe, 3.2 wt% Fe, 4.8 wt% Fe, 6.4 wt% Fe, 16 wt% Fe, and 32 wt% Fe.

[0021] Figure 3E are Fourier transform infrared (FTIR) spectra of pure carbon (g-C), and Fe / g-C hybrid doped with 1.6 wt% Fe, 3.2 wt% Fe, 4.8 wt% Fe, 6.4 wt% Fe, 16 wt% Fe, and 32 wt% Fe.

[0022] Figure 3F are Raman spectra of pure carbon (g-C), and Fe / g-C hybrid doped with 1.6 wt% Fe, 3.2 wt% Fe, 4.8 wt% Fe, 6.4 wt% Fe, 16 wt% Fe, and 32 wt% Fe, showing the D (1373 cm-1) and G (1589 cm-1) bands.

[0023] Figure 4A is an X-ray Photoelectron Spectroscopy (XPS) survey scan measured of the g-C catalyst sample.

[0024] Figure 4B is a high resolution XPS spectra of C 1 s measured of the g-C catalyst sample.

[0025] Figure 4C is a high resolution XPS spectra of O 1s measured of the g-Ccatalyst sample.

[0026] Figure 5A is an XPS survey scan measured of the 1 ,6wt% Fe / g-C catalyst sample.

[0027] Figure 5B is a high resolution XPS spectra of C 1 s measured of the 1.6wt% Fe / g-C catalyst sample.

[0028] Figure 5C is a high resolution XPS spectra of O 1s measured of the 1.6wt% Fe / g-C catalyst sample.

[0029] Figure 5D is a high resolution XPS spectra of Fe 2p measured of the 1.6wt% Fe / g-C catalyst sample.

[0030] Figure 6A is an XPS survey scan measured of the 32wt% Fe / g-C catalyst sample.

[0031] Figure 6B is a high resolution XPS spectra of C 1 s measured of the 32wt% Fe / g-C catalyst sample.

[0032] Figure 6C is a high resolution XPS spectra of O 1s measured of the 32wt% Fe / g-C catalyst sample.

[0033] Figure 6D is a high resolution XPS spectra of Fe 2p measured of the 32wt% Fe / g-C catalyst sample.

[0034] Figure 7A illustrates a fitting of a Raman spectrum of sample 16wt% Fe / g-C to obtain the ID / IG ratios which are plotted in Figure 7B.

[0035] Figure 7B is plot of ID / IG ratios as a function of Fe content.

[0036] Figure 8A is a plot showing a detailed N2 physisorption isotherm of the graphenic carbon (g-C) sample.

[0037] Figure 8B is a plot showing a detailed N2 physisorption isotherm of the 1.6 wt% Fe / g-C sample.

[0038] Figure 8C is a plot showing a detailed N2 physisorption isotherm of the 3.2 wt% Fe / g-C sample.

[0039] Figure 8D is a plot showing a detailed N2 physisorption isotherm of the 4.8 wt% Fe / g-C sample.

[0040] Figure 8E is a plot showing a detailed N2 physisorption isotherm of the 6.4 wt% Fe / g-C sample.

[0041] Figure 8F is a plot showing a detailed N2 physisorption isotherm of the 16 wt% Fe / g-C sample.

[0042] Figure 8G is a plot showing a detailed N2 physisorption isotherm of the 32 wt% Fe / g-C sample.

[0043] Figure 9A is diffusive reflective spectra of the Fe / g-C photocatalyst hybrids.

[0044] Figure 9B is a Tauc representation for optical bandgap determination for the graphenic carbon (g-C) sample.

[0045] Figure 9C is a Tauc representation for optical bandgap determination for the 1 .6 wt% Fe / g-C sample.

[0046] Figure 9D is a Tauc representation for optical bandgap determination for the 3.2 wt% Fe / g-C sample.

[0047] Figure 9E is a Tauc representation for optical bandgap determination for the 4.8 wt% Fe / g-C sample.

[0048] Figure 9F is a Tauc representation for optical bandgap determination for the 6.4 wt% Fe / g-C sample.

[0049] Figure 9G is a Tauc representation for optical bandgap determination for the 16 wt% Fe / g-C sample.

[0050] Figure 9H is a Tauc representation for optical bandgap determination for the 32 wt% Fe / g-C sample.

[0051] Figure 10 is a perspective view of an example UV collimated beam photoreactor used to conduct the photocatalytic experiments in the Examples.

[0052] Figure 11A is a plot PFOA removal (C / Co) as a function of time (h), comparing PFOA removal using pure and Fe-doped g-C photocatalysts. Experimental conditions that were used include: [PFOA]o = 1 mg L’1, photocatalyst dosage = 1 g L’1, temperature = 22±2°C, and UV254 fluence rate = 1.42±0.05 mW cm-2

[0053] Figure 11 B is a plot of PFOA removal (C / Co) as a function of time (h), showing the effect of initial concentration of PFOA on its removal using 32 wt% Fe / g-C hybrid. Experimental conditions that were used include: photocatalyst dosage = 1 g L’1, temperature = 22±2°C, and UV254 fluence rate = 1.42±0.05 mW cm-2.

[0054] Figure 11C is a plot of PFOA removal (C / Co) as a function of time (h), showing removal efficiency of PFOA under dark conditions, UV radiation (254 nm), and simulated solar light (AM 1.5G), showing the enhanced removal capability under simulated solar light with [PFOA]o = 1 mg L’1.

[0055] Figure 12A is a plot illustrating the concentration profile of PFOA in UV / 32wt% Fe / g-C photocatalyst. Experimental conditions that were used include: [PFOA]o = 5 mg / L, catalyst dosage = 1 g / L, temperature = 22+2 °C, and UV254 fluence rate = 1.42±0.05 mW / cm2.

[0056] Figure 12B is a plot illustrating the concentration profile of the generated intermediates of PFOA degradation in UV / 32wt% Fe / g-C photocatalyst.

[0057] Figure 13A is a plot of PFOA removal efficiency (%) as a function of different initial concentrations of PFOA (0.1-5 mg / L) and in dark and UV processes.Experimental conditions that were used include: temperature = 22°2 °C, catalyst dosage = 1 g / L, and UV254 fluence rate in photochemical process = 1.42±0.05 mW / cm2.

[0058] Figure 13B is a plot of PFOA removal (C / Co) as a function of time (h), showing the kinetics of PFOA removal at different initial concentrations during UV / 32wt%Fe / g- C process. Experimental conditions that were used include: temperature = 22°2 °C,catalyst dosage = 1 g / L, and UV254 fluence rate in photochemical process = 1.42±0.05 mW / cm2.

[0059] Figure 13C is a plot of PFOA removal efficiency (%) as a function of time (h), illustrating PFOA removal within 6 h in dark and UV process with 64 wt% Fe / g-C photocatalyst. Experimental conditions that were used include: temperature = 22°2 °C, catalyst dosage = 1 g / L, and UV254 fluence rate in photochemical process = 1.42±0.05 mW / cm2.

[0060] Figure 14 is a plot of weight (%) as a function of temperature (°C), illustrating the results from a thermogravimetric analysis of g-C and 32 wt% Fe / g-C as compared with the starting material (e.g., pulp).

[0061] Figure 15A is a plot of PFOA removal efficiency (%) as a function of cycle number, showing PFOA removal in 5 consecutive cycles using 32 wt% Fe / g-C hybrids. Experimental conditions that were used include: [PFOA]o in each cycle = 1 mg L’1, photocatalyst dosage = 1 g L’1, temperature = 22 ± 2°C, and UV254 fluence rate = 1.42 ± 0.05 mW cm-2.

[0062] Figure 15B are SEM images of 32 wt% Fe / g-C hybrid after the 5thcycle.

[0063] Figure 15C are high resolution XPS spectra of F1s and O1 s measured for the 32 wt% Fe / g-C hybrid before and after PFOA decomposition.

[0064] Figure 16A is a plot of fluorine recovery (%) as a function of time (h), showing fluorine mass balance during PFOA degradation using a UV / 32wt% Fe / g-C photocatalyst. Experimental conditions that were used include: [PFOA]o = 5 mg / L, catalyst dosage = 1 g / L, temperature = 22+2 °C, and UV254 fluence rate = 1.42±0.05 mW / cm2.

[0065] Figure 16B is a plot of fluoride adsorbed (ppb) as a function of time (h), showing the adsorption of fluoride on catalyst surface in both dark and UV conditions. Experimental conditions that were used include: [fluoride]o = 3.5 mg / L, catalyst 32wt% Fe / g-C dosage = 1 g / L, temperature = 22+2 °C, and UV254 fluence rate in photochemical process = 1.42±0.05 mW / cm2.

[0066] Figure 17A is a SEM image of graphenic carbon (g-C).

[0067] Figure 17B is a SEM image of 1 ,6wt% Fe / g-C.

[0068] Figure 17C is a SEM image of 3.2 wt% Fe / g-C.

[0069] Figure 17D is a SEM image of 4.6 wt% Fe / g-C.

[0070] Figure 17E is a SEM image of 6.4wt% Fe / g-C.

[0071] Figure 17F is a SEM image of 16wt% Fe / g-C.

[0072] Figure 17G is a SEM image of 32wt% Fe / g-C.

[0073] Figure 18 are pXRD patterns of pulp and hybrid photocatalysts produced from using ferric acetate as the metal-containing compound.

[0074] Figure 19 are pXRD patterns of hybrid photocatalysts produced from using iron oxide (FeaO^ particles as the metal-containing compound and hybrid photocatalysts produced from using ferric chloride (FeCh) as the metal-containing compound.Detailed Description

[0075] Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive sense.Definitions

[0076] “Graphenic carbons” refers to a broad class of carbonaceous solids that include materials with two-dimensional and three-dimensional structures with graphene layers as the conceptual structural unit.

[0077] “Impregnation” refers to the process of dispersing a substance (e.g., metalcontaining compound such as a metal salt) on a solid porous structure (e.g., carbon- containing biomass), resulting in at least some of the substance being absorbed or diffused into the structure. Non-limiting examples of impregnation techniques include solid-state impregnation, aqueous impregnation, and / or gas impregnation

[0078] “Oxidative atmosphere” refers to an atmosphere which contains oxidizing gases such as one or more of oxygen, water vapor, carbon dioxide, nitrogen oxides, sulfur oxide, ozone peroxides, etc. An oxidative atmosphere may additionally contain inert gases, such as nitrogen, noble gases, etc. A “non-oxidative atmosphere” refers to an atmosphere which does not contain oxidizing gases.

[0079] “Pyrolysis” refers to the process of converting a material into one or more other compounds by heating the material in an oxidative or non-oxidative atmosphere. The pyrolysis reaction may be performed in a suitable pyrolysis reactor which can be heated to a desired pyrolysis temperature. A non-limiting example of a suitable pyrolysis reactor comprises a muffle furnace.

[0080] “Transition metal ion” refers to a metal ion in the d-block of the periodic table (groups 3 to 12).Example methods of producing hybrid photocatalysts

[0081] Aspects of the invention relate to methods of producing hybrid photocatalysts that are used to decompose synthetic chemicals. Embodiments of the present invention provides a frugal method of producing hybrid photocatalysts. The method may utilize readily available feedstock, and provides a few number of steps, and which such steps are simple, easy to adopt and cost effective.

[0082] Proof of concept demonstrations of the hybrid photocatalyst described herein have shown that greater than about 85% efficiency of decomposition of PFOA at a fluence rate of about 1 .42 mW / cm2within 6 hours of degradation time with an initial PFOA concentration (Co) of 1 mg / L can be achieved.

[0083] Figure 1 is a flow chart illustrating the steps of an example method 10 ofproducing hybrid photocatalysts. Referring to Figure 1 , in block 12, a carbon- containing biomass feedstock is impregnated with a metal-containing compound.

[0084] The carbon-containing biomass feedstock may comprise any organic material that is derived from a natural resource such as plants and animals. A suitable carbon- containing biomass feedstock may comprise carbon, hydrogen and / or oxygen. In some embodiments, the carbon-containing biomass feedstock comprises cellulose. In some embodiments, the carbon-containing biomass feedstock comprises lignocellulose materials, such as hardwood, softwood and / or agricultural residues such as wheat straw. The lignocellulose materials may comprise varying ratios of cellulose, lignin and hemicellulose. Non-limiting examples of organic materials that may be used as the carbon-containing biomass feedstock include wood (e.g., pine, oak, maple, eucalyptus, etc.), wood pulp which may be virgin and / or recycled, cotton, flax, hemp, sugarcane bagasse, bamboo, corn, spent grain, coffee grounds, and mixtures thereof. In some embodiments, the carbon-containing biomass feedstock is sourced from a waste stream. The waste stream may comprise one or more of agricultural waste, food waste, animal waste, municipal solid waste, paper mill sludge, etc.

[0085] The metal-containing compound comprises a metal ion or a combination of two or more metal ions. In some embodiments, the metal-containing compound comprises a metal alloy. The alloy may comprise a mixture of metallic and / or non- metallic elements. In some embodiments, the metal ion comprises one or more transition metal ions. In some embodiments, the metal ion comprises iron (Fe), gallium (Ga), and / or Indium (In). In some example embodiments, the metal ion comprises iron (Fe).

[0086] In some embodiments, the metal-containing compound is a compound formed by reacting the metal ion with a non-metallic element. The non-metallic element may for example be: a halogen (e.g., any one of more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I)), i.e., to form a metal salt; sulfur, i.e. , to form a metal sulfide; oxygen, i.e., to form a metal oxide; nitrogen, i.e., to form a metal nitride.

[0087] In some embodiments, the metal-containing compound comprises a metalcomplex formed by reacting the metal with a ligand. The ligand may comprise an organic ligand, such as but are not limited to acetyl ligands, alkyl ligands, cyclic alkyl ligands, alkenyl ligands, aryl ligands, etc.

[0088] In some embodiments, the metal-containing compound comprises a metal salt. In some example embodiments, the metal salt comprises ferric chloride (FeCh).

[0089] In some embodiments, the metal-containing compound is in a solid state. The metal-containing compound may for example, be in the form comprising a powder, nanoparticles and / or bulk materials. In some embodiments, the metal-containing compound is in a liquid or aqueous state. In such embodiments, the metal-containing compound may be contained in a solution or a suspension.

[0090] In some example embodiments, the impregnating of the carbon-containing biomass feedstock with the metal-containing compound comprises soaking and / or spraying the carbon-containing biomass feedstock with a solution or suspension containing the metal-containing compound. In some example embodiments, the impregnating of the carbon-containing biomass feedstock with the metal-containing compound comprises mixing nanoparticles comprising the metal-containing compound with the carbon-containing biomass feedstock.

[0091] The feedstock is optionally pre-treated by one or more suitable chemical and / or mechanical treatments prior to impregnation (block 16). The pre-treating of the feedstock may increase the absorption or diffusivity of the metal-containing compound into the feedstock. In some embodiments, the pre-treating of the feedstock comprises reducing the particle size of the feedstock. The reducing of the particle size of the feedstock may be performed by any one or more of grinding, milling, cutting, chopping, shearing, crushing, etc. (all of such particle size reducing methods are collectively referred to herein as “grinding”). The feedstock may be ground to a particle size that is suitable for impregnation. In some embodiments, the feedstock is ground to powders. In some embodiments, the feedstock is ground to particles. In some embodiments, the particle size of the feedstock is reduced to about 0.05 mm to about 50 cm, and in some embodiments, between about 0.05 mm and about 20 cm, and in some embodiments, between about 0.05 mm and about 10 cm, and in someexample embodiments, between about 0.05 mm to about 1 cm.

[0092] In some embodiments, the impregnation step is performed at room temperature, such as in the range of from about 20°C to about 30°C. The operating conditions of the impregnation step such as one or more of impregnation time and / or temperature and / or pressure may be adjusted to optimize the absorption or diffusivity and / or penetration depth of the metal-containing compound into the feedstock.

[0093] The impregnated biomass may optionally be dried (block 20). The impregnated biomass preferably comprises a moisture content that is suitable for pyrolysis and / or which allows for optimizing one or more of the rate of pyrolysis, and / or the quality and / or yield of the resulting products. For example, the impregnated biomass may comprise a moisture content of less than 50% wt., and in some embodiments, less than 40% wt., and in some embodiments, less than 30% wt., and in some embodiments, less than 20% wt. Any suitable drying methods may be used to dry the impregnated biomass to the desired moisture content, including but not limited to air drying, oven drying, vacuum drying, microwave drying, etc. In some example embodiments, the drying of the impregnated biomass is performed at room temperature.

[0094] The impregnated biomass is optionally pre-treated by one or more suitable chemical and / or mechanical treatments prior to pyrolysis (block 24). In some embodiments, the pre-treating of the impregnated biomass comprises reducing the particle size of the impregnated biomass by grinding the biomass. The impregnated biomass may be ground to a particle size that is suitable for pyrolysis. In some embodiments, the particle size of the feedstock is reduced to about 0.05 mm to about 50 cm, and in some embodiments, between about 0.05 mm and about 20 cm, and in some embodiments, between about 0.05 mm and about 10 cm, and in some embodiments, between about 0.05 mm to about 1 cm, and in some embodiments, about 0.5 millimeters or less.

[0095] In block 28, the impregnated biomass is pyrolyzed by being subjected to a pyrolysis temperature to produce the hybrid photocatalyst. Pyrolyzing the metalcontaining compound impregnated biomass forms a hybrid photocatalyst whichdesirably comprises metal oxides being immobilized on the biomass-derived carbonaceous material.

[0096] In some embodiments, the pyrolysis temperature is greater than about 500°C, and in some embodiments, less than about 1000°C. In some embodiments, the pyrolysis temperature is in the range of from about 550°C to about 950°C. In some example embodiments, the pyrolysis temperature is about 600°C. In some embodiments, the impregnated biomass is subjected to an increasing temperature before reaching the pyrolysis temperature. In some embodiments, the impregnated biomass is heated at a heating rate in the range of from about 1°C / min to about 100°C / min, and in some embodiments, from about 10°C / min to about 100°C / min, and in some embodiments, from about 20°C / min to about 80°C / min, and in some embodiments, from about 30°C / min to about 50°C / min, and in some example embodiments, about 40°C / min.

[0097] In some embodiments, the concentration of the metal-containing compound used in the impregnation of the biomass is selected so that the hybrid photocatalyst contain less than about 60 wt% of the metal oxide, and in some embodiments, about 0.1 to about 60 wt% of the metal oxide, and in some embodiments, about 0.1 to about 40 wt% of the metal oxide, and in some embodiments, about 10 wt% to about 40 wt%, and in some embodiments, about 20 wt% to about 40 wt%, and some example embodiments, about 32 wt% of the metal oxide.

[0098] In some embodiments, the pyrolysis is performed in an oxidative atmosphere, in the presence of one or more oxidizing gases such as oxygen. In some embodiments, the pyrolysis is performed in a non-oxidative atmosphere, in the absence of oxidizing gases.

[0099] The residence time during which the impregnated biomass is subjected to the pyrolysis temperature may be less than one hour, and in some embodiments, less than 45 minutes, and in some embodiments, less than 30 minutes, and in some embodiments, less than 15 minutes, and in some embodiments, less than 10 minutes, and in some embodiments, 5 minutes or less.

[0100] Method 10 may be tuned to optimize the photocatalytic efficiency of the hybrid photocatalyst by adjusting one or more of:- type and / or amount of carbon-containing biomass feedstock; and / or- particle size of the feedstock and / or the impregnated biomass; and / or- moisture content of the impregnated biomass that is being supplied for pyrolysis; and / or- operating conditions of the pyrolysis step, such as temperature and / or residence time and / or presence / absence of gas and / or amount of gas present;- type and / or concentration of the metal-containing compound used to impregnate the feedstock;- method and / or operating conditions used to impregnate the feedstock;- etc.Example hybrid photocatalysts

[0101] Aspects of the invention relate to a hybrid photocatalyst. The hybrid photocatalyst may be produced by method 10. The hybrid photocatalyst comprises metal oxide immobilized on a biomass-derived carbonaceous material. In some embodiments, the metal oxide comprises metal oxide nanoparticles. The metal oxide nanoparticles may comprise a crystalline structure, i.e. , highly ordered materials with a periodic pattern of atoms.

[0102] In some embodiments, the concentration of the metal oxide is less than about 60 wt%, and in some embodiments, less than about 50 wt%, and in some embodiments, less than about 40 wt%, and in some embodiments, in the range of from about 1 wt% to about 60 wt%, and in some embodiments, in the range of from about 20 wt% to about 40 wt%.

[0103] The pyrolysis of the metal-containing compound-impregnated biomass drives the formation of one or more magnetic forms or photoactive species of the metal oxide. The magnetic forms of the metal oxide have increased photocatalytic activities, as compared to non-magnetic forms of the metal oxide. For example, in embodimentsin which the metal oxide comprises iron oxide, the hybrid photocatalyst may comprise iron oxides in the forms of one or more Fe2Oa (e.g., of a-Fe2C>3 and g- Fe2Oa), FeaO4, and FeOOH (e.g., a-FeOOH). In such embodiments, the steps of the method 10 may be tuned to favor the formation of Fe2Oa, and more preferably the formation of a- Fe2C>3. In some embodiments, a greater amount of iron oxide in the hybrid photocatalyst is in the form of Fe2Os than in the form of FesO4. In some embodiments, at least about 80wt% of the iron oxide in the hybrid photocatalyst is in the form of Fe2C>3, and in some embodiments, at least about 75 wt%, and in some embodiments, in the range of from about 30 wt% to about 80 wt%, and in some embodiments, in the range of from about 50 wt% to about 75 wt%.

[0104] In some embodiments, the hybrid photocatalyst comprises oxygen-containing functional groups bonded to the biomass-derived carbonaceous material. The oxygen-containing functional groups comprise one or more of hydroxyl (O-H), carbonyl (C=O), carboxyl (O-C=O), carbon-oxygen (C-O), and metal oxide groups.

[0105] In some embodiments, the biomass-derived carbonaceous material comprises amorphous carbons. Amorphous carbons are free, reactive carbons that do not have a crystalline structure. In some embodiments, the biomass-derived carbonaceous material are graphenic. The graphenic biomass-derived carbonaceous material may be porous. The graphenic biomass-derived carbonaceous material may comprise micropores with pore sizes which are less than about 2 nm and / or mesopores with pore sizes which are in the range of from about 2 nm to about 50 nm. In some embodiments, the graphenic biomass-derived carbonaceous material comprises an average micropore volume (Vp, micro) that is greater than about 0.020 cm3 / g, and in some embodiments, greater than about 0.050 cm3 / g, and in some embodiments, greater than about 0.080 cm3 / g, and in some embodiments, between about 0.040 cm3 / g and about 0.150 cm3 / g. The micropore volume value may be obtained from measurements of a gas (e.g., N2) physisorption isotherm, and calculated by a t-plot equation for carbon-based materials (Carbon Black STSA thickness equation, t = 2.98 + 6.45 (p / p0) + 0.88 (p / p0)2.

[0106] In some embodiments, the specific surface area of the hybrid photocatalyst is between about 50 m2 / g and about 500 m2 / g, and in some embodiments, between about 100 m2 / g and about 450 m2 / g, and in some embodiments, greater than about 100 m2 / g, and in some embodiments, greater than about 200 m2 / g, and in some embodiments, about 400 m2 / g to 450 m2 / g. The specific surface area value may be obtained from measurements from a gas (e.g., N2) physisorption isotherm obtained when using the Branauer-Emmet-Teller (BET) technique.

[0107] In some embodiments, the hybrid photocatalyst has an average particle size in the range of from about 1 nm to about 1000 nm, and in some embodiments, from about 1 nm to about 500 nm, and in some embodiments, from about 10 nm to about 100 nm in diameter. The hybrid photocatalyst may comprise different morphologies including for example tube-like, fiber-like, sphere-like, particle-like, flake-like, and / or network-like morphologies.Example applications of hybrid photocatalyst

[0108] Aspects of the invention relate to use of the hybrid photocatalyst described herein to decompose synthetic chemicals. In some example applications, the synthetic chemicals comprise perfluoroalkyl and polyfluoroalkyl substances (PFAS). In some embodiments, the PFAS comprises perfluorooctanoic acid (PFOA) and / or perfluorooctane sulfonate (PFOS). The PFAS may be contained in an environmental medium, such as water, air, and / or soil.

[0109] The decomposing of the synthetic chemicals may comprise degrading the synthetic chemicals. The degradation of the synthetic chemicals may involve radical- induced depolymerization of the synthetic chemicals, thereby breaking one or more chemical bonds (e.g., C-C bonds, C-F bonds, etc.) which form the synthetic chemicals.

[0110] In some embodiments, the decomposing of the synthetic chemicals comprises contacting the hybrid photocatalyst with the synthetic chemicals. The synthetic chemicals may be adsorbed on the surface of the hybrid photocatalyst. The hybridphotocatalyst may be exposed to ultraviolet (UV) radiation. Exposure to UV radiation may cause the generation of positive holes on the surface or a transfer of electrons from the surface of the hybrid photocatalyst to the adsorbed synthetic chemicals, thereby depolymerizing the synthetic chemicals to its component parts (e.g., atoms and / or ions and / or molecules).

[0111] In some embodiments, the UV radiation comprises a wavelength from about 100 nm to about 400 nm. In some embodiments, the UV radiation comprises sunlight.

[0112] In embodiments in which the synthetic chemicals comprise PFAS, the decomposing of the PFAS molecules results in defluorinating PFAS, thereby releasing ions comprising fluoride.

[0113] The invention is further described with reference to the following specific examples, which are not meant to limit the invention, but rather to further illustrate it.EXAMPLESExample 1

[0114] A method 10 of the type illustrated in Figure 1 was used to produce hybrid photocatalysts. In an example embodiment, the metal-containing compound comprises the metal salt, iron chloride (Fe2Ch). The carbon-containing biomass feedstock comprises CTMP pulp. The carbon-containing biomass feedstock was pretreated by milling the feedstock into powders with a 40 OD mesh. The feedstock was impregnated by soaking the feedstock in a solution comprising iron chloride. The impregnated biomass was placed in a fume hood to air dry at room temperature. The impregnated biomass was milled using a 40 OD mesh. The impregnated biomass was pyrolyzed at 600°C for five minutes using a muffle furnace at a heating rate of 40°C / min under an oxidative temperature to yield hybrid photocatalysts. The resulting hybrid photocatalysts are referred to hereinafter as iron oxide / graphenic carbon (Fe / g- C) hybrid photocatalysts, or iron doped samples.1. Comparative analysis of Fe / g-C hybrid in relation to other photocatalysts

[0115] Figure 2 illustrates results from an analysis conducted to compare the effectiveness of the Fe / g-C hybrid in relation to other photocatalysts described in the literature. The assessment was based on the degradation of PFAS achieved, considering the degradation time, UV fluence, and the photocatalyst’s weight normalized to the initial PFAS concentration. The rectangular boxes correspond to decomposition efficiency of different heterogeneous photocatalysts reported in the literature. The data for Fe / g-C featured in this study are indicated in circles. The results showed that the Fe / g-C hybrid significantly outperformed other photocatalysts described in the literature.2. Morphological and structural characterization of Fe / g-C hybrid

[0116] Figures 3A-C showcase the morphological characteristics of graphenic carbon (g-C) and Fe / g-C samples. Figures 3A-C are scanning electron microscopy (SEM) images of pure graphenic carbon (g-C), 32 wt% Fe / g-C, and a magnified region showing iron oxide crystallite grown on g-C surface, respectively. The presence of tube-like structures suggests that certain features of the original cellulose materials are retained post-pyrolysis, see Figure 3A. These structures appear to be somewhat fragmented and overlapping, creating a dense and irregular texture. In Figure 3B, 32 wt% Fe / g-C, provides a more zoomed-out view, revealing a heterogeneous mixture of particles where again, tube-like morphologies are noticeable. This scale gives a sense of the overall distribution of particles within this sample. In Figure 3C magnifies an area of the iron-doped carbon, showing a dense agglomeration of particles with iron oxide crystallites. Unlike the more fibrous and elongated structures seen in Figures 3A and B, this image shows a rough, granular surface texture. The iron oxide nanoparticles appear to be well-dispersed across the carbon substrate, which the inventors believe it to be a desirable trait for enhancing photocatalytic activity due to improved charge separation.

[0117] The chemical structure of Fe / g-C hybrids was further confirmed by the powder X-ray diffraction (pXRD) pattern, Fourier transform infrared (FTIR) and Raman spectra, respectively (as shown in Figures 3D-F). X-ray Photoelectron Spectroscopy (XPS) was also applied to investigate the surface electronic structure of the iron oxide(Figures 4A-6D).

[0118] Powder samples were subjected to XRD to evaluate their crystalline structure in a medium and long-range order. According to Figure 3D, the XRD pattern of the pure carbon (g-C) did not exhibit the presence of a crystalline phase. However, as the iron concentration was increased, implying the increased crystallinity and the prevalence of hematite as an iron oxide phase. The diffraction peaks were consistent with the presence of a-Fe2C>3 (JCPDS#33-0664), g-Fe2Oa (JCPDS#39-1246), FeaO4 (JCPDS#19-0629), a-FeOOH (JCPDS#12-0412), graphite and amorphous carbon network as indicated in Figure 3D.

[0119] FTIR spectra of g-C and iron doped samples contain intensive bands for aromatic C=C stretching vibrations at about 1584 cm-1. The intensity of this peak remained relatively consistent, suggesting that the iron oxide doping did not substantially alter the sp2-hybridized carbon network. Carbonyl (C=O) stretching vibrations occur at 1705 cm-1, which decreased in intensity as a function of iron concentration. This suggests that the introduction of iron may influence the formation or exposure of carbonyl functionalities in the graphenic structure. The presence of band centered at 1192 cm-1indicate the presence of C-O groups. This peak’s intensity and shape could vary based on the interaction of these oxygen-containing groups with the iron oxide particles. Also, a broad band in the range from 3500 to 3200 cm-1is apparent and was attributed to O-H stretching vibrations. Additionally, an absorption band at 542 cm’1was observed in the samples which was assigned to Fe-O stretching. The trend that was observed is that as the iron content decreases, the peaks attributed to iron oxide (if the 542 cm’1peak indeed represents Fe-O) become less pronounced, while the organic functionalities of the graphenic carbon remain relatively constant. This aligned with the inventors’ expectations since the fundamental carbon lattice structure should remain largely intact, while dopant level varies.

[0120] Raman spectroscopy was conducted to clarify structural changes in the graphenic carbon structure as a function of iron content (Figure 3E). In contrast to pXRD, Raman measurements monitor structural properties at short-range orders. TheRaman spectra of pure g-C and Fe / g-C show a characteristic G band centered at 1589 cm-1and a D band centered at 1373 cm-1. The identified bands correspond to the vibrational modes of carbon sp2atoms. The ID / IG ratio, representing the intensity ratio of the D and G bands, is frequently used as a structural order indicator (see Table 1 ). Graphitic carbon materials with long-range order in graphitic layers have a higher ID / IG ratio than pure graphite when defects such as aromatic cluster borders appear. A carbon material composed of a few aromatic clusters of small size will have a higher D mode intensity depending on how many sixfold rings are in the cluster. An elevated ID / IG ratio indicates the order in this case. As iron content in hybrid photocatalyst increased, ID / IG ratios linearly increased (Figures 7A and B), indicating a higher degree of order. The enhanced structural order as a function of iron content may lead to improved charge transfer and reduced recombination of electron-hole pairs resulting in a faster photocatalytic degradation rate of PFAS.Table 1. Ratios of the D and G band intensities of the pure and iron oxide-loaded samples as function of iron contentSample / D / / G ratio g-C 1.121.6wt% Fe 1.273.2wt% Fe 1.354.8wt% Fe 1.496.4wt% Fe 1.6816wt% Fe 1.7232wt% Fe 1.86

[0121] The spectroscopic analyses confirmed the successful incorporation of iron oxide nanoparticles onto the carbon support, indicating strong interfacial coupling between the two components.

[0122] Figures 4A-C and Table 2 show the XPS data and fitting parameters for the g- C photocatalyst. The XPS spectra of C 1 s and O 1s show all the oxygen-containing functional groups being present on the carbon support. The main peaks in the C 1s spectrum correspond to carbon-carbon (C-C) bonds at approximately 284.6 eV, carbon-oxygen (C-O) bonds at around 286.3 eV, and carbonyl groups (C=O) at about288.3 eV. The O 1s peak in this spectrum also displays two main peaks assigned to oxygen in hydroxyl groups (O-H), and oxygen atoms in carbonyl or carboxyl groups (C=O or O-C=O). These oxygen-containing functional groups may play a crucial role in the surface chemistry of the material, influencing its reactivity and interactions with the metal oxide centers.Table 2. Fitting parameters of g-C XPS data.V Line shape % AreaC=C 284.30 1.30 LA(1 .2, 2.5, 5) 53.8C-C, C-H 284.80 1.30 GL(30) 22.0C-OH, C-O- 286.20 1.30 GL(30) 15.9CC=O 287.70 1.30 GL(30) 5.4O-C=O 288.80 1.30 GL(30) 2.9 p-p* 290.71 2.70 GL(30) 0O 1sBE / eV FWHM / eV Line shape % AreaC=O, O-C=O 531.48 2.23 GL(30) 44.4C-OH, C-O- 533.13 2.23 GL(30) 55.6C

[0123] XPS measurements of the 1.6wt% and 32 wt% Fe / g-C samples were also performed and displayed in Figures 5A-D and 6A-D, respectively. Tables 3 and 4 show the fitting parameters for the 1 ,6wt% and 32 wt% Fe / g-C samples respectively. The XPS spectra of C 1s and O 1 s core levels were acquired to investigate the chemical composition of the samples in more detail. The C 1s peak shows a decrease in carbon containing oxygen as the concentration of iron increases converting these groups into carbon-carbon network. The O 1 s peak in both samples also displays a range of binding energy shifts indicative of different oxygen species on the sample's surface. These shifts can be associated with oxygen atoms bound to metal ions (metal oxides), oxygen in hydroxyl groups (O-H), and oxygen atoms in carbonyl or carboxyl groups (C=O or O-C=O).

[0124] The high-resolution XPS of Fe 2p was also measured for both 1.6 wt% and 32 wt% Fe / g-C (Figure 5D and 6D) samples. The deconvolution of the Fe 2p spectra revealed detailed information about the oxidation states of iron on the sample surfaces and provided insights into its chemical environment and coordination. From the deconvolution it was possible to determined that 33% of iron present in the 1 ,6wt% Fe / g-C sample is in the form of Fe3O3and 67% in the form of Fe3O4.However, in the 32wt% Fe / g-C sample the concentration of iron photoactive specie (Fe3O3) increased with a total of 67% while 33% is in the form of Fe3O4. These results were in agreement with XRD data presented in Figures 3A-F.Table 3. Fitting parameters of 1.6wt% Fe / g-C XPS data.V Line shape % AreaC=C 284.30 1.30 LA(1 .2, 2.5, 5) 51.4C-C, C-H 284.80 1.30 GL(30) 26.0C-OH, C-O- 286.20 1.30 GL(30) 13.7CC=O 287.70 1.30 GL(30) 5.4O-C=O 288.80 1.30 GL(30) 3.5 p-p* 290.71 2.70 GL(30) 0BE / eV FWHM / eV Line shape % AreaFe3O4708.45 1.20 GL(30) 11.2Fe3O4709.25 1.20 GL(30) 9.9Fe2O3709.75 1.20 GL(30) 10.1Fe3O4710.25 1.40 GL(30) 15.9Fe2O3710.75 1.30 GL(30) 10.1Fe3O4711.25 1.40 GL(30) 11.9Fe2O3711.75 1.40 GL(30) 7.5Fe3O4712.35 1.40 GL(30) 8.2Fe2O3712.95 1.40 GL(30) 3.4Fe3O4713.45 1.40 GL(30) 3.8Fe2O3714.05 1.70 GL(30) 1.9Fe3O4714.55 3.30 GL(30) 6.1Table 4. Fitting parameters of 32wt% Fe / g-C XPS data.V Line shape % AreaC=C 284.30 1.27 LA(1 .2, 2.5, 5) 52.9C-C, C-H 284.80 1.25 GL(30) 31.1C-OH, C-O- 286.20 1.25 GL(30) 8.3CC=O 287.70 1.25 GL(30) 4.8O-C=O 288.80 1.25 GL(30) 2.9 p-p* 290.72 2.70 GL(30) 0Fe 2pBE / eV FWHM / eV Line shape % AreaFe3O4708.35 1.20 GL(30) 5.5Fe3O4709.18 1.20 GL(30) 4.9Fe2O3709.75 1.20 GL(30) 20.6Fe3O4710.18 1.40 GL(30) 7.8Fe2O3710.75 1.30 GL(30) 20.6Fe3O4711.18 1.40 GL(30) 5.8Fe2O3711.75 1.40 GL(30) 15.3Fe3O4712.28 1.40 GL(30) 4.0Fe2O3712.95 1.40 GL(30) 6.8Fe3O4713.38 1.40 GL(30) 1.9Fe2O3714.05 1.70 GL(30) 3.8Fe3O4714.48 3.30 GL(30) 3.03. Photocatalytic removal of PFOA using Fe / g-C hybrid

[0125] The textural properties of carbonized materials derived from renewable resources (e.g., cellulose) are key parameters affecting their functionality. Specific surface area, pore volume and size were assessed by N2physisorption isotherms and the results for pure g-C and 32 wt% Fe / g-C are listed in Table 5.Table 5. Textural analysis values (BET surface area and pores volumes) and optical properties of pure g-C and 32 wt% Fe / g-C.Photocatalyst BET surface area Pore diameter Band gap32 wt% Fe / g-C 427 13.4 1.19

[0126] The BET surface area of g-C and 32 wt% Fe / g-C were about 56 and about 427 m2g-1, respectively. The average absorption pore width was obtained by the automatic DFT system calculation. Results showed that the average absorption pore width increases as a function of iron content. The average absorption pore width was obtained by the automatic DFT system calculation. Results showed that the average absorption pore width increases as a function of iron content. The observed isotherms (Figures 8A-G) fall under Type IV, which was typical for mesoporous materials, with hysteresis loops indicative of capillary condensation within these pores. The evolution of hysteresis loops with increased iron doping suggests alterations in pore connectivity and shape, hinting at the complexity introduced by the iron oxide. The specific surface area, as revealed by the BET analysis and summarised in Table 6, increases with iron oxide doping. The increase in surface area suggests that the addition of iron oxide to the graphenic carbon matrix contributes positively to creating additional surface area. This may be attributed to the creation of additional pores or to the iron oxide nanoparticles which prevented the collapse of existing pores during the synthesis process, thus maintaining or enhancing the overall porosity of the material.Table 6. Textural analysis values (specific surface area and pores volumes) of the Fe / g-C photocatalyst hybrids.

[0127] From the UV-Vis diffuse reflectance spectroscopy and to evaluate the optical bandgap from the absorption spectra, the Kubelka-Munk theory was applied. Optical band gaps in a range of 1.19 to 1.49 eV were derived for the composites (Figures 9A- 9H and Table 7). These values are larger than those of pure graphene (2.5 eV) and FeaO4 (2.67 eV) but are comparable to those of TiO2 (2.9 eV). Furthermore, the high bandgap could result in reduced photocatalytic activity. However, the large surface area and porous size may facilitate its photoactivity.Table 7. Values of optical bandgap calculated using Tauc of Fe / g-C photocatalyst hybrids.Sample Optical bandgap (Eg) / eV g-c 1.281 ,6wt% Fe / g-C 1.433.2wt% Fe / g-C 1.494.8wt% Fe / g-C 1.396.4wt% Fe / g-C 1.3316wt% Fe / g-C 1.2632wt% Fe / g-C 1.19

[0128] The photoreactor illustrated in Figure 10 was used to decompose PFOA. The photoreactor comprises a LP lamp ballast 1 arranged inside a cuboid aluminum housing 2, and a collimation tube 3 projecting downwardly from a surface of the housing 2. A quartz cylindrical cell 4 is positioned on a stir plate 5. The stir plate 5 is being supported on a jack 6. The jack 6 is placed on a stand 7, and which the stand comprises a pair of spaced-apart posts arranged to connect a base of the stand 7 to the housing 2.

[0129] The photocatalytic decomposition of PFOA (Co = 1 mg L'1) was conducted with photocatalyst dosage of 1 g L'1doped with different iron content ranging from 1 .6 to 32 wt% Fe. Referring to Figure 11 A, owing to the low molar absorption coefficient of PFOA at 254 nm, £PFOA, 254 ™ of 3.5±0.9 M'1cm'1, the concentration of PFOA remained unchanged in UV alone experiments. Fe / g-C with doped concentrations of 1.6, 3.2, 4.8, and 6.4 wt% Fe resulted in only 3.7%, 5.8%, 7.2%, and 13.4% decrease in PFOA concentration within 6 h irradiation time (UV fluence of 30.7 J cm-2), respectively. In contrast, 16 wt% and 32 wt% Fe / g-C hybrids significantly enhanced PFOA removal efficiency to 66.4% and 89.7% within 6 h. In view of the insignificant role played by direct photolysis (without photocatalyst), the inventors hypothesized that the decomposition of PFOA comprises two consecutive steps. The first step is the adsorption of PFOA on the surface of the Fe / g-C hybrid photocatalyst, followed by a subsequent step of electron transfer from the surface of the hybrid photocatalyst to the adsorbed PFOA molecules, leading to the decomposition of PFOA to its component acids (see Figures 12A-B).

[0130] Due to the increased decomposition of PFOA in the presence of 32 wt% Fe / g- C, compared to the other tested catalysts, the inventors selected this photocatalyst composition to investigate the photodegradation of PFOA and effects of keyparameters (e.g., initial concentration of PFOA) on the degradation process. As shown in Figure 11 B, increasing the dosage of catalyst considerably enhanced the removal of PFOA which was believed to be due to the further availability of complexation sites for PFOA molecules. The results demonstrated that the catalyst shows promising PFOA removal even in low dosages of 0.1 g L’1, where approximately 79% of the PFOA was removed within 6 hours.

[0131] The initial concentration of PFOA may affect the ratio of available complexation sites on the catalyst surface relative to the amount of PFOA and consequently the extent of its removal. The reported values of initial PFAS concentrations in real aquatic environments vary in a wide range of ng L'1in natural waters (e.g., surface- and groundwater) to mg L'1in industrial wastewater or concentrated waste stream of physical separation techniques. As shown in Figure 13A, B and C, increasing the initial concentration of PFOA from 0.1 to 5 ppm decreased the removal efficiency from nearly complete removal of PFOA to 86%. Such observation implies that the catalyst could result in fast removal of PFOA in low concentrations commonly observed in natural waters and obtain significant removal (about 85%) at PFOA dosage representative of concentrated waste stream.Moreover, the results confirm that the Fe / g-C hybrid photocatalyst is a very promising tool for PFAS decomposition and offers a more efficient approach than other methods currently being used for this process.

[0132] Owing to the ability of iron to form a complex with PFOA, Fe / g-C hybrids may play a dual-role as both adsorbent and photo-catalyst to destroy the captured PFOA. Figures 13A and B compares PFOA removal using 32 wt% Fe / g-C under UV and a control experiment in the presence of the same dosage of catalyst but in dark (without UV irradiation) condition. The catalyst containing 64 wt% Fe / g-C did not demonstrate enhanced PFOA degradation (Figure 13C). 63.7% and 89.7% of PFOA were removed within 6 h in dark and UV conditions, respectively. Such observation confirms the dual role of employed catalyst where PFOA molecules were firstly adsorbed on the surface of photocatalyst and then degrade by UV irradiation and in turn faster removal of PFOA was observed in UV process. Thermogravimetric analysis (TGA) as shown in Figure 14 affirms the catalyst’s stability within theexperimental temperature range.

[0133] Scaling up a heterogeneous photocatalyst for PFAS decomposition requires not only the ability to manufacture the catalyst in large quantities but also to identify if the photocatalyst is stable over a longer period of time. This was investigated by performing five consecutive batch cycles (~30 hours) using 32 wt% Fe / g-C photocatalyst (Figure 15A). After 6 h in each cycle, upon taking 2 mL sample for analysis, an aliquot (0.1 mL) of PFOA stock solution (500 mg L'1) was added to the solution to increase the concentration of PFOA back to roughly 1 ppm and the solution was mixed for five minutes to ensure sufficient contact with the photocatalyst and then take a sample for initial concentration of next cycle. As shown, greater than 90% of PFOA was removed with the first 4 cycles and nearly 88.5% of PFOA was removed in the last cycle. Furthermore, the photocatalyst morphology did not exhibit any notable change after 30 hours of experiment, which indicates that the Fe / g-C maintains its structure during extended irradiation. The results support the stability and recyclability of the photocatalyst, which allows for repeated use without requiring chemical regeneration.

[0134] Fluoride is in the indicative byproduct of defluorination of PFOA. Figures 16A and B show the total recovery (mass balance) of fluoride, i.e., the molar ratio of total fluoride in the form of PFOA, its generated intermediates (shorter chain PFCAs), and fluoride (F-), versus time. The total fluoride recovery using 32 wt% Fe / g-C hybrid decreased to 42.2% within 1.5 hours and remained relatively constant afterward. In a control experiment using sodium fluoride (NaF) with the same concentration of fluoride in 5 ppm PFOA (3.45 ppm F’), the inventors observed that 47.0% of initial fluoride was adsorbed to the surface catalyst (32 wt% Fe / g-C). The inventors believed that it was mainly due to the presence of iron oxide on the catalyst surface since no adsorption of fluoride was observed using pure g-C catalyst (Figures 16A-B). The iron concentration resulting from ion leaching post-photodegradation was determined by ICPMS. The leached iron fell within the range of 69.948 to 70.210 ppm.

[0135] To provide insights into the adsorption process and photodegradation ofPFOA, high-resolution XPS analysis on the 32 wt% Fe / g-C hybrid was performedbefore and after the reaction (Figure 15C). After quenching the reaction, an additional peak assigned to F 1 s occurred at 648.5 eV, confirming the fluoride adsorption on the photocatalyst surface after cycle 1 . The O 1 s XPS spectra before and after the reaction (Figure 15C) were deconvoluted into three peaks, which were assigned to hydroxyl (OH) groups at 531.4 eV, lattice oxygen in a-Fe2O3at 530.2 eV, and at 533.2 eV oxygen of carbonyl groups. The binding energy and relative content of oxygen groups are shown in Table 8. These data revealed that the oxygen-related functional groups on the photocatalyst hybrids underwent a reduction following the photocatalytic reaction. This implies that, during this process, the photo-excited electrons within a-Fe2Oa may have spontaneously migrated towards the g-C network, resulting in the reduction of the oxygen-related functional groups present on the g-C support. The oxygen-containing functional groups on the g-C support may play the role as an electron acceptor, which serves to decelerate the recombination of charges. Consequently, this facilitates the direct transfer of holes, ultimately contributing to the efficient photocatalytic oxidation occurring on the Fe / g-C surface.Table 8. Fitting parameters of O 1 s high-resolution XPS spectra to monitor different oxygen species present on the photocatalyst surface during the cycles.Before reactionV Line shape % Area lattice oxygen 530.2 1.30 GL(30) 4.9OH groups 531.4 1.30 GL(30) 37.4 carbonyl groups 533.2 2.30 GL(30) 57.7After cycle 1 lattice oxygen 530.0 1.30 GL(30) 5.7OH groups 531.3 1.30 GL(30) 13.2 carbonyl groups 532.2 2.30 GL(30) 81.1After cycle 5 lattice oxygen 529.9 1.30 GL(30) 5.2OH groups 531.4 1.30 GL(30) 59.0 carbonyl groups 533.3 2.230 GL(30) 35.8

[0136] These findings provide strong evidence for an effective approach to PFAS degradation. The inventors have demonstrated that through a simple, economical synthesis, an abundant heterogeneous hybrid photocatalyst can rapidly decompose PFOA, achieving rates of >85% in just 3 hours with a UV fluence of 30.7 W cm-2. The inventors have demonstrated that high rates of PFOA degradation can be achieved without resorting to expensive and complex methods. Furthermore, the observed consistency in maintaining decomposition rates of >85% for 30 hours under a UV fluence of 1.42 ± 0.05 mW cm-2underscores the promise of this approach. These proof of concept demonstrates established that graphenic carbon-doped composites can effectively address persistent organic pollutants in water, with the added benefit of reducing the required UV fluence rates, thus making PFAS degradation more efficient and practical.4. Methods and materials used in the Examples1. Chemicals

[0137] Iron (III) chloride (FeCh, 99.5%), perfluorooctanoic acid (CF3(CF2)eCOO-, PFOA), potassium iodide (KI, >99%), potassium iodate (KIO3, 99.5%), sodium tetraborate (Na2B40y 10H20, >99.5%) were purchased from Sigma-Aldrich™. ChemiThermoMechanical (CTMP) pulp was donated by Canfor™. PFOA stock solution was prepared overnight and passed through 0.45 mm membrane filter (Millex-HV™ Syringe Filter Unit) and stored at 4°C in the dark. All the chemicals and reagents were used without further purification, and ultrapure water (Milli-Q water with resistivity of 18.2 MQ.cm) was used in all experiments.2. Synthesis of Fe / g-C hybrid Photocatalyst

[0138] Pure and Fe-doped graphenic carbon (g-C) were synthesized using CTMP pulp. First, the CTMP was milled into fine powders with 40 OD mesh and six doped Fe samples were prepared by soaking the fibers in 20 mL of different concentrations of FeCh. The doped fibers were then placed in a fume hood to dry at room temperature. To obtain a fine powder and to facilitate the pyrolysis process the soaked dry fibres were milled again using a 40 OD mesh. The doped fine powders were pyrolyzed at 600 °C for 5 minutes using a muffle furnace with a heating rate of 40 °C min-1under an oxidative atmosphere. Once the muffle furnace reached 600 °C, it was turned off to gradually bring the temperature of the samples down to room temperature.3. Characterization of Fe / g-C hybrid Photocatalyst3.1 Scanning Electron Microscopy (SEM)

[0139] SEM was used to examine the morphology and microstructure of the Fe / g-C hybrid photocatalyst. SEM images were obtained using a Quattro ESEM microscope operated at an acceleration voltage of 10 kV and magnification of 1200X (Figures 17A-G).3.2 Thermogravimetric analysis (TGA)

[0140] Thermogravimetric analysis (TGA) was conducted on pure g-C, 32 wt% Fe / g- C, and precursor material (e.g., pulp, CTMP). The experiments were carried out using a thermogravimetric analyzer TGA 5500, where samples weighing between 5 to 10 mg were heated under a nitrogen atmosphere from 25 to 850 °C at a heating rate of 20 °C per minute (Figure 14).3.2 Powder X-ray Diffraction (p-XRD)

[0141] Powder X-ray Diffraction (p-XRD) analysis was conducted to determine the crystalline structure and phase composition of the Fe / g-C hybrid photocatalyst using a Rigaku™ MiniFlex 6G system. p-XRD analysis revealed distinct diffraction peaks corresponding to the crystal lattice planes of both iron oxide and carbon, indicating the presence of well-defined crystalline domains in the Fe / g-C hybrid photocatalyst.These diffraction peaks were consistent with the presence of a-Fe2O3(JCPDS#33- 0664), g-Fe2O3(JCPDS#39-1246), Fe3O4(JCPDS#19-0629), a-FeOOH (JCPDS#12- 0412), graphite and amorphous carbon network as indicated in Figure 3D).3.3 Fourier Transformed Infrared (FT IR) and Raman Spectroscopy

[0142] Fourier transformed infrared (FTIR) spectroscopy analysis was performed using a Bruker Invenio spectrometer. Spectra were acquired in attenuated total reflection (ATR) mode in the wavenumber range from 4000 to 400 cm-1. All the spectra were acquired using a 4 cm-1resolution and collecting 128 scans.

[0143] Raman spectroscopy was carried out at room temperature with an inVia™ confocal Raman microscope. The excitation wavelength was 532 nm. Spectra were collected from three random positions on each specimen, on account of the possible structural non-homogeneity of the samples. Measurements were performed using a low laser power to prevent laser-induced damage. Spectra were analyzed using a commercially available OriginLab software. A Lorentzian line for D band and a Breit- Wigner-Fano (BWF) curve for the G peak, superimposed to a constant background were used (Figures 7A-B) to reproduce the spectral profile in the region of mix aromatic sp2and sp3carbons; a least-square fit chose the wavenumber position, width, and intensity of the bands.3.4 Specific Surface Area and Porosity

[0144] Textural characteristics of the photocatalyst hybrids were accessed by N2physisorption analysis at 77 K using a 3 Flex surface area analyzer (Micrometrics™, Norcross, GA, USA). Prior to analysis, the samples were degassed at 150 °C for 24 hours under vacuum. The specific surface area values (SBET) were determined using the Branauer-Emmet-Teller (BET) equation. The total pore volumes (Vp, total) were defined as the volume of liquid nitrogen corresponding to the amount of gas adsorbed at p / pO > 0.99. The micropores surface areas and pore volumes were calculated from the t-plot equation for carbon-based materials (Carbon Black STSA thickness equation, t = 2.98 +6.45(p / po) + O.88(p / po)2, pore size distribution curves were also calculated using Density Functional Theory (DFT). Figure 8 shows a detail of N2physisorption isotherms and Table 6 summarises the obtained values for specific surface area (SBET), micropores (Sm / cro, t-Piot), and mesopores surface area (Sextemai, t-Piot) values and pore volumes values.3.5 Diffusive Reflectance Spectroscopy (DRS)

[0145] The optical properties of the photocatalysts were evaluated using UV-vis diffuse reflectance spectroscopy, performed on an Agilent Cary™ 5000 spectrophotometer. Spectralon reflectance standard was used as a reference material. Measurements were taken in the range of 250 to 2500 nm, limited by the configuration of the instrument. The diffuse reflectance mode was employed (see Figures 9A-H), and the obtained data were converted to the extinction coefficient using the Kubelka-Munk function, specifically F(R~), to determine the energy bandgap. Spectra were recorded at 1 nm intervals with a spectral bandwidth of 2 nm. The powdered samples were then pressed into holders with a diameter of about 3 cm and a depth of 5 mm. Regarding the nature of electronic transitions, the process of light absorption in amorphous carbons occurs through indirect allowed transitions, denoted as n = 2. A smaller number of studies discuss direct transitions or employ an exponent of 1 / n = 0.5 in the Tauc representation, yet without providing clear elucidation of the transition type. The utility of the Tauc method in determining the optical bandgap in carbon materials has been verified across a range of amorphous carbons. Irrespective of the specific transition type under consideration, all plotted curves exhibit a noticeable gap, which is distinctly linked to the optical bandgap. This reaffirms that the Tauc transformation enables the identification of a bandgap in amorphous carbons. Taking this into account, the inventors have applied the Tauc representation with indirect transitions to fit our experimental data for the carbon samples (see Figures 9A-H). The resulting Egvalues for the Fe / g-C photocatalyst hybrids are summarized in Table 7.3.6 Photoelectron Spectroscopy (XPS)

[0146] The XPS analyses were carried out with a Kratos AXIS Nova™ X-ray photoelectron spectrometer using a monochromatic Al K(alpha) source (15mA, 15kV). The instrument work function was calibrated to give a binding energy (BE) of 83.96eV for the Au 4f7 / 2 line for metallic gold and the spectrometer dispersion was adjusted to give a BE of 932.62 eV for the Cu 2p3 / 2 line of metallic copper. The Kratos charge neutralizer system was used on all specimens. Survey scan analyses were carried out with an analysis area of 300 x 700 microns and a pass energy of 160 eV. High resolution analyses were carried out with an analysis area of 300 x 700 microns and a pass energy of 20 eV. Spectra have been charge-corrected to the main line of the carbon 1 s spectrum (C-C, C-H) set to 284.8 eV. Spectra were analysed using CasaXPS™ software (version 2.3.26) with Shirley background.4. Photocatalytic Tests4.1. Experimental Setup

[0147] The photocatalytic experiments were conducted with a collimated beam bench-scale photoreactor shown in Figure 10, for making fluence measurements. Prior studies investigating PFAS photocatalytic decomposition measured the extent of decomposition / defluorination based on time, not based on fluence or the actual irradiation energy received by the system. This makes the comparison of the results from different laboratories and scales difficult. Unless several operational parameters of the photolysis system are reported in these studies, given the different radiant characteristics of lamps available and the geometry of photochemical reactors, the time-based rate constants are difficult to reproduce in other laboratories and hence, would be difficult to translate into the real scenarios.

[0148] The photoreactor was equipped with a low-pressure (LP) amalgam lamp emitting UV at 254 nm (Light Sources Inc™, Orange CT USA). The lamps were mounted in a cuboid aluminum housing with an aperture for fitting of a collimation tube composed of black carbon-filled PTFE, measured 20 cm in length and 5 cm inner diameter, having an inside surface roughened to reduce reflection. An aluminum shutter was attached to the bottom of collimation tube and operated manually in coordination with a timer to measure exposure times. The sample cell (i.e., reaction vessel) has an interior diameter of 57 mm and a capacity of 75.0 mL and was placed on top of a small stir plate. A miniature Teflon™-coated magnetic stir bar was placed inside the cell to provide adequate mixing. The lamp was ignited and a period of atleast 30 min was allowed before the start of the experiments. This guaranteed a steady output from the lamp. For temperature control, a cuvette holder made of copper was used to quickly remove heat from the UV source and kept the temperature difference within 2 °C.4.2. Experimental Procedure

[0149] 50 mg of photocatalyst (different Fe / g-C samples) was dispersed to 50 mL of a 1 mg L'1PFOA solution (initial pH = 3.5; catalyst dosage of 1 g L'1). The mixed solution was stirred for 30 minutes under dark conditions to read an adsorptiondesorption equilibrium between PFOA and the photocatalyst surface. Meanwhile, the UV lamp was preheated for 30 min to stabilize its output power. The photocatalytic experiments were performed at room temperature (22+2 °C). During the photocatalytic reaction, 2 mL of the solution was taken at a set time interval.5. Analytical Methods5.1 Fluence Rate

[0150] The average UV 254 nm fluence rate, E’avg, 254 nm, was determined by a calibrated UV-Vis radiometer (Flame Ocean Optic™, USA). The radiometer was used to measure the irradiance at the center of the petri dish (Eo) where the detector head is at the same level as that of the top of the solution. A few corrections including Reflection Factor (RF), Petri Factor (PF), Water Factor (WF), and Divergence Factor (DF) were considered to obtain E’avg (Eq. 1).EaVg= Eox RF x PF x WF x DF (1)

[0151] The accuracy of radiometer was validated by a chemical actinometry, lodide / iodate actinometry is a traditional method used to determine incident irradiance at 254 nm. In this technique, a standard solution, consisting of 0.6 M KI, 0.1 M KIO3 and 0.01 M Na2B4O? H2O at pH 9.25, is prepared from 9.96 g of KI, 2.14 g KIO3 and 0.38 g of Na2B4O? H2O brought to 100 mL with distilled water. The reagents on exposure to UV form triiodide ( / 3“), the proposed reaction having the following stoichiometry:8KI + KIO3+ 3H2O + hv -> 3I7 + 60H~ + 9K+(2)

[0152] The absorbance of triiodide can be determined spectrophotometrically (using a UV-vis spectrophotometer (UV-Vis Cary™ 100, Agilent Technologies™, USA)) and used to calculate the UV irradiance:E = 23.373

[0153] Where A352(blank) is the initial absorbance at 352 nm of standard actinometry solution. A352(sample) is the absorbance at 352 nm of the standard solution after radiation. As described in the literature, the constant 23.373 is the result of dividing the energy of a mole of photons at 254 nm (4.716 x 105J Einstein-1) over the product of the of triiodide (0.73) at 254 nm and the molar absorption coefficient of triode at 352 nm (27600 M-1cm-1). The obtained E’ from chemical actinometry accounts for the PF and RF, which needs to be corrected only for the WF and the DF corresponding to the solution that is irradiated. In the UV collimated beam used in this study, the value for the incident fluence rate at 254 nm was determined using the KI-KIO3 actinometer to be:E’ = 1.77 + 0.05 mW cm~2

[0154] The correction factors WF and DF were calculated as following:1 - 10“alWF = — ,z, = 0.87 al ln(10)L DF = - = 0.92L + 1 where a is decadic absorption coefficient (0.0638 cm-1for 254 nm), I is the vertical path length of the solution in the Petri dish (19.6 mm), and L is the distance of solution from lamp (24 cm). So,Ea'vg= E' x WF x DF = 1.42 ± 0.05 mW cm~25.2. PFAS Analysis

[0155] An Agilent™ 1200 series ultra-high performance liquid chromatography / mass spectrometry (uHPLC / MS) system was employed to analyze the PFOA concentrations. A volume of 20 pL of sample was injected onto a Waters Xterra MS C18 column (100 x 2.1 mm, 3.5 pm particle size; Waters Corporation, Milford, MA), proceeded by a C18 guard column (30 x 2.1 mm, 3.5 pm particle size) from the same manufacturer. Both columns were maintained at 50 °C, and the mobile phase flow was set at 1 mL min-1. The mobile phase consisted of (A) water with 20 mM ammonium acetate and (B) acetonitrile (gradient of A:B as 50:50 (0 minutes), 10:90 (0-5 minutes), 50:50 (5-5.5 minutes), and remain at 50:50 until 8 minutes). Mass spectrometric analysis was performed using an Agilent™ mass spectrometer in negative electrospray ionization and MRM modes. The drying gas (N2) temperature was 325 °C, drying gas flow was 1 L min-1, nebulizer pressure was 344.7 kPa, and capillary voltage was 4000 V. PFOA was quantified using individual 10-point calibration in the working concentration range (0.5 pg L'1to 2 mg L'1).5.3. Post-photodegradation iron determination

[0156] The concentration of iron after the photodegradation of PFOA was determined using an Agilent™ 7700x Quad ICPMS instrument. Calibration standards were prepared by diluting IV71A mixed standard from Inorganic Ventures™ to achieve iron concentrations of 0.1 , 1 , 10, 25, and 100 ppb. The calibration standards were then analyzed using the ICPMS™ instrument following standard protocols. Notably, samples initially showed concentrations outside the instrument’s detection range, necessitating a 1000X dilution for rerun analysis. Reference materials TM25.3 and TM26.3 provided by Environment Canada were used for quality control.Example 2

[0157] A method 10 of the type illustrated in Figure 1 was used to produce hybrid photocatalysts. In these examples, the metal-containing compound comprises ferric acetate (FeAc). The carbon-containing biomass feedstock comprises pulp. The carbon-containing biomass feedstock was pre-treated by milling the feedstock intofine powder. The feedstock was impregnated by soaking the feedstock in a solution comprising ferric acetate for 5 hours. The impregnated biomass was dried. The dried impregnated biomass was pyrolyzed at 600°C for five minutes under an oxidative temperature to yield hybrid photocatalysts. In these examples, the concentration of the iron oxide in the hybrid photocatalysts is about 32 wt%.

[0158] The chemical structure of the hybrid photocatalysts formed by impregnating the biomass with ferric acetate as the metal-containing compound was confirmed by the powder X-ray diffraction (pXRD) pattern, as shown in Figure 18. The diffraction peaks were consistent with the presence of hematite.Example 3

[0159] A method 10 of the type illustrated in Figure 1 was used to produce hybrid photocatalysts. In these examples, the metal-containing compound comprises iron oxide (FesO4) particles having sizes in the range of from 50 to 100 nm or ferric chloride (FeCh). The carbon-containing biomass feedstock comprises pulp. The carbon-containing biomass feedstock was pre-treated by milling the feedstock into fine powder. The feedstock was impregnated with the (FesCh) particles or ferric chloride (FeCh). The impregnated biomass was dried. The dried impregnated biomass was pyrolyzed at 600°C for five minutes under an oxidative temperature to yield hybrid photocatalysts.

[0160] The chemical structure of the hybrid photocatalysts formed by impregnating the biomass with iron oxide (FeaO^ particles as the metal-containing compound was confirmed by the pXRD pattern, as shown in Figure 19. The diffraction peaks were consistent with the presence of hematite.Interpretation of Terms

[0161] Unless the context clearly requires otherwise, throughout the description and the claims:“comprise”, “comprising”, and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to”;• “connected”, “coupled”, or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof;• “herein”, “above”, “below”, and words of similar import, when used to describe this specification, shall refer to this specification as a whole, and not to any particular portions of this specification;• “or”, in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list;• the singular forms “a”, “an”, and “the” also include the meaning of any appropriate plural forms. These terms (“a”, “an”, and “the”) mean one or more unless stated otherwise;• “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes both (A and B) and (A or B);• “approximately” when applied to a numerical value means the numerical value ± 10%;• where a feature is described as being “optional” or “optionally” present or described as being present “in some embodiments” it is intended that the present disclosure encompasses embodiments where that feature is present and other embodiments where that feature is not necessarily present and other embodiments where that feature is excluded. Further, where any combination of features is described in this application this statement is intended to serve as antecedent basis for the use of exclusive terminology such as "solely," "only" and the like in relation to the combination of features as well as the use of "negative" limitation(s)” to exclude the presence of other features; and• “first” and “second” are used for descriptive purposes and cannot be understood as indicating or implying relative importance or indicating the number of indicated technical features.

[0162] Words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description and any accompanying claims (where present), depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0163] Where a range for a value is stated, the stated range includes all sub-ranges of the range. It is intended that the statement of a range supports the value being at an endpoint of the range as well as at any intervening value to the tenth of the unit of the lower limit of the range, as well as any subrange or sets of sub ranges of the range unless the context clearly dictates otherwise or any portion(s) of the stated range is specifically excluded. Where the stated range includes one or both endpoints of the range, ranges excluding either or both of those included endpoints are also included in the invention.

[0164] Certain numerical values described herein are preceded by "about". In this context, "about" provides literal support for the exact numerical value that it precedes, the exact numerical value ±5%, as well as all other numerical values that are near to or approximately equal to that numerical value. Unless otherwise indicated a particular numerical value is included in “about” a specifically recited numerical value where the particular numerical value provides the substantial equivalent of the specifically recited numerical value in the context in which the specifically recited numerical value is presented. For example, a statement that something has the numerical value of “about 10” is to be interpreted as: the set of statements:• in some embodiments the numerical value is 10; in some embodiments the numerical value is in the range of 9.5 to 10.5;and if from the context the person of ordinary skill in the art would understand that values within a certain range are substantially equivalent to 10 because the values with the range would be understood to provide substantially the same result as the value 10 then “about 10” also includes:• in some embodiments the numerical value is in the range of C to D where C and D are respectively lower and upper endpoints of the range that encompasses all of those values that provide a substantial equivalent to the value 10.

[0165] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and / or acts with equivalent features, elements and / or acts; mixing and matching of features, elements and / or acts from different embodiments; combining features, elements and / or acts from embodiments as described herein with features, elements and / or acts of other technology; and / or omitting combining features, elements and / or acts from described embodiments.

[0166] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any other described embodiment(s) without departing from the scope of the present invention.

[0167] Any aspects described above in reference to apparatus may also apply to methods and vice versa.

[0168] Any recited method can be carried out in the order of events recited or in any other order which is logically possible. For example, while processes or blocks are presented in a given order, alternative examples may perform routines having steps,or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified to provide alternative or subcombinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, simultaneously or at different times.

[0169] Various features are described herein as being present in “some embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or any combination of two or more of such features. All possible combinations of such features are contemplated by this disclosure even where such features are shown in different drawings and / or described in different sections or paragraphs. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible). This is the case even if features A and B are illustrated in different drawings and / or mentioned in different paragraphs, sections or sentences.

[0170] It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.REFERENCES1 . Buck, R. C. et al. Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and origins. IntegratedEnvironmental Assessment and Management 7, 513-541 (2011). Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management | Environmental Science & Technology. https: / / pubs.acs.org / doi / 10.1021 / acs.est.8b06648. Loos, R. et al. Pan-European survey on the occurrence of selected polar organic persistent pollutants in ground water. Water Research 44, 4115-4126 (2010). Cousins, I. T., Johansson, J. H., Salter, M. E., Sha, B. & Scheringer, M. Outside the Safe Operating Space of a New Planetary Boundary for Per- and Polyfluoroalkyl Substances (PFAS). Environ. Sci. Technol. 56, 11172-11179 (2022). Holzer, J. et al. One-year follow-up of perfluorinated compounds in plasma of German residents from Arnsberg formerly exposed to PFOA-contaminated drinking water. International Journal of Hygiene and Environmental Health 212, 499-504 (2009). Domingo, J. L. & Nadal, M. Per- and Polyfluoroalkyl Substances (PFASs) in Food and Human Dietary Intake: A Review of the Recent Scientific Literature.J. Agric. Food Chem. 65, 533-543 (2017). Zhang, M., Yamada, K., Bourguet, S., Guelfo, J. & Suuberg, E. M. Vapor Pressure of Nine Perfluoroalkyl Substances (PFASs) Determined Using the Knudsen Effusion Method. J. Chem. Eng. Data 65, 2332-2342 (2020). Rivero, M. J., Ribao, P., Gomez-Ruiz, B., Urtiaga, A. & Ortiz, I. Comparative performance of TiO2-rGO photocatalyst in the degradation of dichloroacetic and perfluorooctanoic acids. Separation and Purification Technology 240, 116637 (2020). Yang, Y. et al. Insights into the degradation mechanism of perfluorooctanoicacid under visible-light irradiation through fabricating flower-shaped Bi5O7l / ZnO n-n heterojunction microspheres. Chemical Engineering Journal 420, 129934 (2021). Tang, H., Zhang, W., Meng, Y. & Xia, S. A direct Z-scheme heterojunction with boosted transportation of photogenerated charge carriers for highly efficient photodegradation of PFOA: Reaction kinetics and mechanism. Applied Catalysis B: Environmental 285, 119851 (2021). Xu, T. et al. Enhanced photocatalytic degradation of perfluorooctanoic acid using carbonmodified bismuth phosphate composite: Effectiveness, material synergy and roles of carbon. Chemical Engineering Journal 395, 124991 (2020). Lotz, K. et al. Tuning the Properties of Iron-Doped Porous Graphitic Carbon Synthesized by Hydrothermal Carbonization of Cellulose and Subsequent Pyrolysis. ACS Omega 4, 4448-4460 (2019). Dreimol, C. H. et al. Sustainable wood electronics by iron-catalyzed laser- induced graphitization for large-scale applications. Nat Commun 13, 3680 (2022). Hunter, R. D., Ramirez-Rico, J. & Schnepp, Z. Iron-catalyzed graphitization for the synthesis of nanostructured graphitic carbons. J. Mater. Chem. A 10, 4489-4516 (2022). Dudder, H., Wutscher, A., Stoll, R. & Muhler, M. Synthesis and characterization of lignite-like fuels obtained by hydrothermal carbonization of cellulose. Fuel 171, 54-58 (2016). Liu, S., Yao, K., Fu, L.-H. & Ma, M.-G. Selective synthesis of Fe3O4, y-Fe2O3, and a-Fe2O3 using cellulose-based composites as precursors. RSC Adv. 6, 2135-2140 (2015). Mukherjee, A., Chakrabarty, S., Kumari, N., Su, W.-N. & Basu, S. Visible-Light-Mediated Electrocatalytic Activity in Reduced Graphene Oxide- Supported Bismuth Ferrite. ACS Omega 3, 5946-5957 (2018). Adolfsson, K. H., Yadav, N. & Hakkarainen, M. Cellulose-derived hydrothermally carbonized materials and their emerging applications. Current Opinion in Green and Sustainable Chemistry 23, 18-24 (2020). Kubelka, P. & Munk, F. Ein beitrag zur optik der farbanstriche. Z. Techn. Physik 'l , 593-601 (1931). Ke, F. et al. Large bandgap of pressurized trilayer graphene. Proceedings of the National Academy of Sciences 116, 9186-9190 (2019). Dette, C. et al. TiO2 Anatase with a Bandgap in the Visible Region. Nano Lett. 14, 6533-6538 (2014). Esfahani, E. B., Zeidabadi, F. A., Zhang, S. & Mohseni, M. Photo- chemical / catalytic oxidative / reductive decomposition of per- and polyfluoroalkyl substances (PFAS), decomposition mechanisms and effects of key factors: a review. Environ. Sci.: Water Res. Technol. 8, 698-728 (2022). Ross, I. et al. A review of emerging technologies for remediation of PFASs. Remediation Journal 28, 101-126 (2018). Wang, Y., Zhang, P., Pan, G. & Chen, H. Ferric ion mediated photochemical decomposition of perfluorooctanoic acid (PFOA) by 254nm UV light. Journal of Hazardous Materials 160, 181-186 (2008). Banayan Esfahani, E. & Mohseni, M. Fluence-based photo-reductive decomposition of PFAS using vacuum UV (VUV) irradiation: Effects of key parameters and decomposition mechanism. Journal of Environmental Chemical Engineering 10, (2022). Bhatnagar, A., Kumar, E. & Sillanpaa, M. Fluoride removal from water by adsorption - A review. Chemical Engineering Journal 171, 811-840 (2011).

Claims

WHAT IS CLAIMED IS:1 . A method of producing a hybrid photocatalyst, comprising the steps of: impregnating a carbon-containing biomass feedstock with a metalcontaining compound to form an impregnated biomass material; and pyrolyzing the impregnated biomass at a pyrolysis temperature to produce a hybrid photocatalyst, the hybrid photocatalyst comprising metal oxide immobilized on a biomass-derived carbonaceous material.

2. A method of producing a hybrid photocatalyst, consisting essentially of the steps: impregnating a carbon-containing biomass feedstock with a metalcontaining compound to form an impregnated biomass material; and pyrolyzing the impregnated biomass at a pyrolysis temperature to produce a hybrid photocatalyst, the hybrid photocatalyst comprising metal oxide immobilized on a biomass-derived carbonaceous material.

3. A method of producing a hybrid photocatalyst, consisting essentially of the steps: impregnating a carbon-containing biomass feedstock with a metalcontaining compound to form an impregnated biomass material; pyrolyzing the impregnated biomass at a pyrolysis temperature to produce a hybrid photocatalyst, the hybrid photocatalyst comprising metal oxide immobilized on a biomass-derived carbonaceous material; and pretreating the carbon-containing biomass and / or the impregnated biomass before the impregnating and pyrolyzing respectively.

4. The method as defined in claim 3, wherein the pretreating comprises grinding the carbon-containing biomass feedstock to reduce the particle size of the biomass before the impregnating step.

5. The method as defined in claim 3 or 4, wherein the pretreating comprises drying the impregnated biomass before the pyrolysis step.

6. The method as defined in any one of claims 3 to 5, wherein the pretreating comprises grinding the impregnated biomass material to reduce the particle size of the impregnated biomass before the pyrolysis step.

7. The method as defined in any one of the preceding claims, wherein the pyrolysis temperature is greater than about 500°C.

8. The method as defined in any one of the preceding claims, wherein the pyrolysis temperature is less than about 1000°C.

9. The method as defined in any one of the preceding claims, wherein the pyrolysis temperature is in the range of from about 550°C to about 950°C.

10. The method as defined in any one of the preceding claims, wherein the pyrolyzing of the impregnating biomass is performed in an oxidative atmosphere.11 . The method as defined in any one of the preceding claims, wherein the metalcontaining compound comprises a metal ion selected from one or more transition metals.

12. The method as defined in any one of the preceding claims, wherein the metalcontaining compound comprises a metal ion selected from the group consisting of iron (Fe), gallium (Ga), indium (In), and a combination thereof.

13. The method as defined in claim 11 or 12, wherein the metal-containing compound comprises the metal ion and a non-metallic element.

14. The method as defined in any one of claims 11 to 13, wherein the non-metallicelement comprises a halogen, sulfur, oxygen and / or nitrogen.

15. The method as defined in any one of the preceding claims, wherein the metalcontaining compound comprises a metal salt.

16. The method as defined in claim 11 or 12, wherein the metal-containing compound comprises a metal complex formed by reacting the metal ion with an organic ligand.

17. The method as defined in any one of the preceding claims, wherein the carbon-containing biomass feedstock comprises cellulose.

18. The method as defined in any one of the preceding claims, wherein the carbon-containing biomass feedstock comprises wood, wood pulp, cotton, flax, hemp, sugarcane bagasse, bamboo, and mixtures thereof.

19. The method as defined in any one of the preceding claims, wherein the carbon-containing biomass feedstock comprises feedstock sourced from one or more waste streams.

20. The method as defined in claim 19, wherein the one or more waste streams comprises one or more of municipal solid waste, paper mill sludge, food waste, and agricultural waste.21 . The method as defined in claim 1 , further comprising grinding the carbon- containing biomass feedstock to reduce the particle size of the biomass before the impregnating step.

22. The method as defined in claim 1 or 21 , further comprising grinding the impregnated biomass material to reduce the particle size of the impregnated biomass before the pyrolysis step.

23. The method as defined in any one of claims 1 , 21 or 22, further comprising drying the impregnated biomass before the pyrolysis step.

24. The method as defined in any one of the preceding claims, wherein the concentration of the metal-containing compound used in the impregnation of the carbon-containing biomass is selected such that the hybrid photocatalyst contains from about 0.1 wt.% to about 60 wt.% of the metal oxide.

25. A hybrid photocatalyst produced by a method as defined in any one of the preceding claims, wherein the concentration of the metal oxide in the hybrid photocatalyst is less than about 60 wt%.

26. A hybrid photocatalyst produced by a method as defined in any one of claims 1 to 24, wherein the concentration of the metal oxide in the hybrid photocatalyst is less than about 30 wt%.

27. A hybrid photocatalyst produced by a method as defined in any one of claims 1 to 24, wherein the concentration of the metal oxide in the hybrid photocatalyst is between about 1 wt% and about 50 wt%.

28. A hybrid photocatalyst produced by a method as defined in any one of claims 1 to 24, wherein the concentration of the metal oxide in the hybrid photocatalyst is between about 20 wt% and about 40 wt%.

29. A hybrid photocatalyst produced by a method as defined in any one of claims 1 to 24, wherein the metal oxide in the hybrid photocatalyst comprises iron oxide.

30. The hybrid photocatalyst as defined in claim 29, wherein at least about 30 wt% to about 80wt% of the iron oxide in the hybrid photocatalyst is in the form of Fe2Oa.31 . The hybrid photocatalyst as defined in claim 29 or 30, wherein a greater amount of the iron oxide in the hybrid photocatalyst is in the form of Fe2Oa than in the form of FeaO4.

32. The hybrid photocatalyst as defined in any one of claims 25 to 31 , wherein the biomass-derived carbonaceous material comprises a graphenic material.

33. The hybrid photocatalyst as defined in any one of claims 25 to 32, wherein the biomass-derived carbonaceous material comprises an amorphous structure.

34. The hybrid photocatalyst as defined in any one of claims 25 to 33, wherein the metal oxide in the hybrid photocatalyst comprises a crystalline form.

35. The hybrid photocatalyst as defined in any one of claims 25 to 34, wherein the specific surface area of the hybrid photocatalyst is between about 50 m2g-1and 450 m2g-1.

36. The hybrid photocatalyst as defined in any one of claims 25 to 35, wherein the surface area of the hybrid photocatalyst is greater than about 300 m2g-1.

37. Use of a hybrid photocatalyst produced by the method as defined in any one of claims 1 to 24 for decomposing synthetic chemicals.

38. The use as defined in claim 37, wherein the synthetic chemicals comprises per- and poly-fluoroalkyl substances (PFAS).

39. The use as defined in claim 38, wherein the PFAS comprises perfluorooctanoic acid (PFOA) and / or perfluorooctane sulfonate (PFOS).

40. The use as defined in claim 38 or 39, wherein the decomposing of the PFAS comprises: adsorbing the PFAS on a surface of the hybrid photocatalyst; and decomposing the PFAS in the presence of UV radiation by causing generation of positive holes on the surface or a transfer of electrons from the surface of the hybrid photocatalyst to the PFAS molecules, thereby defluorinating the PFAS andreleasing ions comprising fluoride.41 . The use as defined in any one of claims 37 to 40, wherein the decomposing of the synthetic chemicals comprises: contacting the synthetic chemicals with the hybrid photocatalyst; and exposing the hybrid photocatalyst to ultraviolet (UV) radiation.

42. The use as defined in claim 41 , wherein the UV radiation comprises a wavelength from about 100 nm to about 400 nm.

43. The use as defined in claim 41 or 42, wherein the decomposing of the synthetic chemicals comprises exposing the synthetic chemicals to sunlight.

44. The use as defined in any one of claims 37 to 43, wherein the synthetic chemicals are contaminants contained in an environmental medium.

45. The use as defined in claim 44, wherein the environmental medium comprises air, soil and / or water.

46. A hybrid photocatalyst comprising iron oxide immobilized on a biomass- derived carbonaceous material, wherein at least about 30 wt% to about 80 wt% of the iron oxide in the hybrid photocatalyst is in the form of Fe2Oa.

47. The hybrid photocatalyst as defined in claim 46, wherein at least about 50 wt% to about 75 wt% of the iron oxide in the hybrid photocatalyst is in the form of Fe2Oa.

48. The hybrid photocatalyst as defined in claim 46 or 47, wherein a greater amount of iron oxide in the hybrid photocatalyst is in the form of Fe2Oa than in the form of FeaO4.

49. The hybrid photocatalyst as defined in any one of claims 46 to 48, wherein the form of Fe2C>3 comprises a-Fe2C>3.

50. The hybrid photocatalyst as defined in any one of claims 46 to 49, wherein the biomass-derived carbonaceous material comprises a graphenic material.51 . The hybrid photocatalyst as defined in any one of claims 46 to 50, wherein the biomass-derived carbonaceous material comprises an amorphous structure.

52. The hybrid photocatalyst as defined in any one of claims 46 to 51 , wherein the iron oxide in the hybrid photocatalyst comprises a crystalline form.

53. The hybrid photocatalyst as defined in any one of claims 46 to 52, wherein the specific surface area of the hybrid photocatalyst is between about 50 m2g-1and 450 m2g-1.

54. The hybrid photocatalyst as defined in any one of claims 46 to 53, wherein the surface area of the hybrid photocatalyst is greater than about 300 m2g-1.

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