Functionalised adsorbent materials for removal of fluorinated contaminants from water

Abstract

A composition is provided for removal of a target substance from a fluid stream. The composition may be used to remove polyfluorinated alkyl substances (PFAS) from water. The composition comprises a support material comprising iron oxide and / or iron oxide-hydroxide and / or iron hydroxide; and a sorbent molecule that comprises a core polymer; wherein the core polymer is covalently linked to the support material; and wherein the sorbent molecule further comprises one or more covalently linked sorbent groups. Processes for removal of target substances such as PFAS are also provided.

Description

[0001] FUNCTIONALISED ADSORBENT MATERIALS FOR REMOVAL OF FLUORINATED CONTAMINANTS FROM WATER FIELD OF THE INVENTION

[0002] The invention is concerned with the removal of target substances from liquids, such as water, using iron oxide and / or iron oxide-hydroxide and / or iron hydroxide substrate materials chemically modified with polyamines, as well as methods to produce such materials. The present invention further relates to materials for water treatment, sorbent media, amine surface functionalisation, hydrophobic interactions, perfluoroalkyl and polyfluoroalkyl substances (PFAS), water contaminants and filtration devices.

[0003] BACKGROUND OF THE INVENTION

[0004] Global environmental protection regulations, such as those aligned with US EPA Safe Drinking Water Act standards, are aimed at safeguarding public health by ensuring that water supplies potentially threatened by industrial contamination meet rigorous quality benchmarks. As an example of such standards, the NSF-53, developed by NSF International, specifically addresses the performance criteria for water filtration systems that reduce a range of contaminants, including heavy metals and organic chemicals, through adsorption or filtration. Adsorption in this context refers to the process where dissolved or suspended contaminants adhere to the surface of an adsorbent material, while filtration physically separates particulates from the fluid stream. These systems must demonstrate effectiveness in consistently removing harmful substances, even at trace levels, to comply with regulatory limits, providing an essential layer of protection for both consumers and the environment.

[0005] There exists an on-going need for the remediation and recycling of contaminated supplies of key fluid solvents, such as water. It is necessary to re-use and replenish existing resources rather than simply dispose of them. Conventionally, powdered or granular activated carbon (GAC) filters, have been the predominant type of media that has been used in water filtration products that conform to NSF-53.

[0006] There are diverse sources of environmentally damaging pollutants, including wastewater from industrial plants and chemical process facilities which has been improperly disposed of; surface runoff containing fertilisers and pesticides used on agricultural areas; and cleaning detergents as well as flame retardants used in fire-fighting foams. Many industrial chemical contaminants can persist in nature for decades before degrading, and can cause great harm to plants, animals and humans, even at very low concentrations. The impact on ecological systems is also profound, with persistent pollutants often concentrating in the bodies of organisms higher up the food chain.

[0007] One particular class of persistent environmental pollutants includes halogenated organic compounds such as poly- and perfluorinated alkyl substances (PFAS). PFAS are organofluorine compounds that are considered to be chemically inert. They are persistent in the environment and their use is controlledin many countries by the United Nations Framework Convention on Climate, the “Kyoto Protocol” and REACH. Perfluorooctane sulfonic acid (PFOS) and its derivatives have been included in the UN Stockholm Convention and are restricted within the EU under the Persistent Organic Pollutant (POP) regulation. PFOS and perfluorooctanoic acid (PFOA) are toxic PFAS compounds that are used extensively as surfactants and in flame retardants for fire-fighting foams and metal plating processes. Both PFOS and PFOA persist in the environment for very long periods of time and are recognised contaminants in most ofthe world’s fresh water supplies. In April 2024, the US Environmental Protection Agency concluded that the available evidence indicates that PFOA exposure is likely to cause hepatic, immunological, cardiovascular, and developmental effects in humans, given sufficient exposure conditions - e.g., at measured levels in humans as low as 1.1 to 5.2 ng / mL and at administered doses in animals as low as 0.3 to 1.0 mg / kg / day (see EPA Document No. 815R24006, April 2024).

[0008] Adsorption of PFAS compounds such as PFOS and PFOA, onto granular or powdered activated carbon represents a standard solution for their removal from contaminated water. However, the process is slow and inefficient. In particular, the shorter chain PFAS pollutants quickly “break-through” beds of activated carbon, meaning large quantities of activated carbon are required, which must be frequently replaced once saturated with PFAS. This is particularly the case when the threshold concentration of PFAS moves to ever lower levels, as exemplified by the April 2024 US EPA regulations. Currently, adsorbed PFAS cannot be sufficiently washed off activated carbon for regeneration “in situ” without concern of PFAS fragments re-entering the environment through airways. In addition, a significant proportion of activated carbon manufactured globally is derived from fossil fuels, such as bituminous coal, or carbonaceous biomass which is activated via physical processes that release substantial amounts of carbon dioxide. Hence, activated carbon represents an expensive, non-sustainable and single use solution to the problem of removing PFAS from contaminated fluid streams. Ion exchange approaches are also commonly used, but such methods also have a large carbon footprint due to being wholly petroleum-derived, and reliability is again an issue due to breakthrough. Operational longevity and costeffectiveness are also problematic for ion exchange-based resins.

[0009] Previous efforts to remove PFAS contaminants from water include, for example, the use of cellulosic-based supported materials functionalised with high molecular weight polyamines such as polyethylenimine (PEI, typically 25 kDa), combined with hydrophobic groups (see WO2017 / 203281). Such approaches rely predominantly on the sorbent activity of the functional group via, for example, direct electrostatic and / or hydrophobic interactions with the target substance, rather than any particular contribution from the supporting substrate material.

[0010] Further efforts to remove PFAS contaminant from water include the use of alumina-based support materials functionalised with high molecular weight polyamines such as polyethylenimine (PEI, typically 25 kDa), combined with hydrophobic groups (see WO 2023 / 156572 A1). Such approaches rely on careful tuning ofthe alumina pore sizes to the hydrophobic group-functionalised polyamines to generate a functional synergy between the specific alumina-based substrate and the functionalising molecules.Alumina based filtration membranes for the removal of perfluoroalkyl species from water have also been contemplated using alumina functionalised with linear fluorinated silanes containing 13-17 fluorine atoms (Johnson et al. ACS Omega, 2019, 4, 8001). Whilst such membranes showed high levels of specificity for removing PFAS from contaminated water, the amphiphilic silane molecule used as the sorbent molecule has to be synthesised. This creates its own problems as the perfluorinated waste generated in the synthesis of these sorbent filtration membranes is greater than the actual mass of PFAS removed by the membrane when in use. Hence, the improvement in performance is offset by the environmental cost and subsequent commercial non-viability of the approach.

[0011] WO 2019 / 186166 provides compositions and processes for the removal of a target substance from a fluid stream, the composition comprising a polyamine; and a covalently linked hydrophobic group, wherein the polyamine is covalently linked to a support material. The support material may comprise cellulose or silica.

[0012] US 10836654 relates to a method for the removal of organic contaminates from wastewater comprising contacting wastewater comprising an organic contaminate with a basic immobilized amine sorbent, where the basic immobilized amine sorbent comprises a polyamine bound to an inorganic support via a linker, such that contacting the wastewater causes at a least a portion of the organic contaminate to bind to the basic immobilized amine sorbent. The support may be silica, alumina, zeolites or biochar.

[0013] WO 2004 / 041428 relates to a sorbent material having a solid support substantially modified with a fluorinated polymer coating covalently attached to the support. The fluorinated polymer coating contains at least one functional group. Methods of obtaining the sorbent material, the use of these materials for separation of substances, a chromatographic column or cartridge at least partially filled with the sorbent material of the invention, a membrane-like device comprising the sorbent material of the invention, a device comprising the sorbent material of the invention in loose form as well as a miniaturized device comprising the sorbent material are disclosed.

[0014] US 2022 / 0126270 describes a method of capturing a fluorinated carbon compound located within a liquid. The method comprises contacting the fluorinated carbon compound with a block copolymer having a backbone comprising a hydrophilic block and a fluoropolyether block, wherein the fluorinated carbon compound binds to and is captured by the block copolymer.

[0015] WO 2024 / 258720 provides an adsorbent for removing perfluoroalkyl and polyfluoroalkyl substances from an aqueous solution, including perfluoro-octanoic acid (PFOA), perfluoro-octane sulfonate (PFOS), shorter-chained perfluoroalkyl and polyfluoroalkyl substances. The adsorbent includes iron oxide nanocrystals, wherein the absorbent has an adsorption capacity for PFOA of at least 5000 mg / g or an adsorption capacity for PFOS of at least 25,000 mg / g. Also provided are methods of removing contaminants from an aqueous solution, wherein the contaminants include perfluoroalkyl and polyfluoroalkyl substances.US 2021 / 0023533 discloses a polymer / activated carbon composite made up of a branched polyethylenimine and magnetic cores involving FesC disposed activated carbon. The magnetic cores have activated carbonyl groups on the surface. A process for removing organic dyes, such as methyl red, as well as heavy metal ions from a polluted aqueous solution or an industrial wastewater utilizing the composite is disclsoed. A method of synthesizing the polymer / activated carbon composites is also discussed.

[0016] US 2023 / 0264170 discusses a compositions and processes for removal of a target substance from a fluid stream such as PFAS from water. The composition comprises a support material comprising an alumina; and a sorbent molecule that comprises a core polymer. The core polymer is covalently linked to the support material and the sorbent molecule further comprises one or more covalently linked sorbent groups.

[0017] There exists a need to provide economical and re-usable compositions and processes that enable the removal of low concentrations (<1 ppm) of target substances, in particular polluting contaminants, such as PFAS, from fluid streams, such as wastewater, drinking water or within the wider environment. The present invention seeks to overcome the present challenges, including reducing the impact of industrial activity on the aquatic environment, particularly by providing cost effective and more affordable, highly efficient alternatives to meet these objectives.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention provides further surprising development of present technology, in particular regarding the novel functionalisation of iron oxide and / or iron oxide-hydroxide and / or iron hydroxide, their optimisation and fine tuning to improve adsorption thereon of a wide range of poly- and perfluorinated alkyl substances (PFAS), indicating the presently demonstrated surface functionalisation may be widely applicable for remediation of PFAS contamination in water supplies.

[0020] A first aspect of the invention provides a composition for removal of a target substance from a fluid stream, the composition comprising:

[0021] a porous, solid and particulate support material comprising at least an iron oxide, or an iron oxide-hydroxide, or an iron hydroxide, or combination thereof; and

[0022] a sorbent molecule that comprises a core polymer;

[0023] wherein the core polymer is covalently linked to the porous, solid and particulate support material; and wherein the sorbent molecule further comprises one or more covalently linked sorbent groups.

[0024] Suitably, the iron oxide, iron oxide-hydroxide, iron hydroxide or combination thereof comprises at least partially amorphous or further comprises at least one X-ray diffraction (XRD) phase selected from the group consisting of: magnetite; maghemite; hematite; goethite, lepidocrocite, and akageneite.Suitably, the core polymer is a linear or branched polymer.

[0025] A second aspect of the invention provides for a composition for removal of a poly- and perfluorinated alkyl substance (PFAS) from an aqueous liquid, the composition comprising:

[0026] a porous, solid and particulate support material comprising at least an iron oxide, or an iron oxide-hydroxide, or an iron hydroxide or combination thereof having a mesoporous content,

[0027] (i) wherein a majority of the pores are within the mesoporous range and have an average pore size between 2 nm and 50 nm; and

[0028] (ii) wherein the porous, solid and particulate support material has a BET pore volume within the mesoporous range of not less than around 0.20 cm3 / g; and

[0029] a sorbent molecule that comprises a linear or branched core polymer selected from one or more of: poly(ethylenimine); poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); poly(vinylchloride); poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4-vinylpyridine);

[0030] wherein the core polymer is covalently linked to the porous, solid and particulate support material; and

[0031] wherein the sorbent molecule further comprises one or more covalently linked sorbent groups.

[0032] A third aspect provides A composition for use in the removal of a contaminant from an aqueous fluid stream, wherein the composition comprises:

[0033] a) a porous, solid and particulate support material comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof; and

[0034] b) a sorbent molecule comprising:

[0035] i) a branched polyamine covalently linked to the porous, solid and particulate support material; and

[0036] ii) a hydrophobic group covalently linked to the branched polyamine.

[0037] A fourth aspect provides a process for removal of a target substance from a fluid stream comprising contacting the fluid stream with a composition of the first or second aspect and wherein the target substance comprises one or more poly- and perfluorinted alkyl substances (PFAS)..

[0038] Suitably, the fluid stream comprises water.

[0039] A fourth aspect of the invention provides process for removal of a target substance from a fluid stream comprising contacting the fluid stream with a composition comprising a porous, solid and particulate support material comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof and a sorbent molecule that comprises a core polymer; wherein the core polymer is covalently linked to the porous, solid and particulate support material; and wherein the sorbent molecule further comprises one or more covalently linked sorbent groups selected from one or more groups selected from: a substituted or unsubstituted C1-C12 alkyl group; a substituted or unsubstitutedC2-C12 alkenyl group; a substituted or unsubstituted C2-C12 alkynyl group; a substituted or unsubstituted C1-C12 alkoxy group; a substituted or unsubstituted C1-C12 acyl group; a substituted or unsubstituted aromatic hydrocarbon group; a substituted or unsubstituted aromatic group; a heterocyclic group; and a hydrogen atom.

[0040] In a fifth aspect the invention provides filter for the adsorption of one or more PFASfrom a contaminated water source, wherein the filter comprises a composition of the first or second aspect

[0041] Suitably, the filter is for the adsorption of one or more PFAS from a contaminated water source. The filter may be used within a point-of-use (POU) or point-of-entry (POE) water filtration system.

[0042] Within the scope of this disclosure it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0043] BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 shows a graph of a batch test data for the functionalised iron oxide, iron oxide-hydroxide, and iron hydroxide materials compared to competitor materials (Amberlite PSR2+ and GAC Filtrasorb F400) and benchmarked against an alumina-based adsorbent (Reference Functionalised Alumina) for removal of seven different PFAS contaminants from water samples.

[0045] Figure 2 shows a graph of a batch test data for raw iron oxide and iron oxide-hydroxide materials for removal of seven different PFAS contaminants from water samples.

[0046] Figure 3 shows a graph of a batch test data for raw Substrate 3, Substrate 3 intermediate material after Step 2 functionalisation and the fully functionalised Substrate 3 material for removal of seven different PFAS contaminants from water samples.

[0047] Figure 4 shows a graph of mercury (Hg) porosimetry data for six different iron oxide, iron oxidehydroxide and iron hydroxide materials prior to functionalisation with the sorbent molecule.

[0048] Figure 5 shows a graph of X-ray diffraction (XRD) data for six raw iron oxide, iron oxide-hydroxide, and iron hydroxide materials prior to functionalisation with the sorbent molecule.

[0049] Figure 6 shows a graph of particle size distribution (PSD) plots of the raw iron oxide, iron oxidehydroxide, and iron hydroxide materials prior to functionalisation with the sorbent molecule.Figure 7 shows a graph of inductively coupled plasma optical emission spectroscopy (ICP-OES) data for six of the raw iron oxide, iron oxide-hydroxide, and iron hydroxide materials prior to functionalisation with the sorbent molecule.

[0050] DETAILED DESCRIPTION OF THE INVENTION

[0051] Unless otherwise indicated, the practice of the present invention employs conventional techniques of chemistry, materials science and process engineering, which are within the capabilities of a person of ordinary skill in the art.

[0052] Prior to setting forth the invention, a number of definitions are provided that will assist in the understanding of the invention. All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0053] As used herein, the term ‘comprising’ means any of the recited elements are necessarily included and other elements may optionally be included as well. ‘Consisting essentially of’ means any recited elements are necessarily included, elements that would materially affect the basic and novel characteristics of the listed elements are excluded, and other elements may optionally be included. ‘Consisting of’ means that all elements other than those listed are excluded. Embodiments defined by each of these terms are within the scope of this invention.

[0054] The term ‘target’ or ‘target substance’ refers herein to a substance or compound which it is desired to remove or isolate from a fluid. Target substances can be dissolved (i.e. a solute), suspended, emulsified, dispersed, or otherwise carried in the fluid, and as such may be soluble, partially soluble or insoluble in the fluid. As discussed below, target substances can comprise contaminant substances and / or valuable substances which it is desired to remove, and in some cases recover, from the target fluid.

[0055] Target substances as contemplated herein can include ‘contaminants’ or ‘contaminant substances’. In the context of the present invention, ‘contaminants’ are intended to encompass substances which may be harmful to the health of humans or animals, or to the environment. Consequently, derivative terms are defined accordingly, for example, a contaminated fluid is a fluid comprising a contaminant substance. Typically, the contaminant comprises one or more per- and polyfluoroalkyl substances (PFAS), typically one or more perfluorocarbons, optionally selected from a perfluorinated anionic surfactant compound, including one or more selected from the group consisting of: perflourobutanoic acid (FPBA); perfluoropentanoic acid (PFPeA); perfluorooctanoic acid (PFOA); perfluorobutanesulfonic acid (PFBS); perfluorohexanesulfonic acid (PFHS or PFHxS); perfluorohexanoic acid (PFHA); perfluorooctanesulfonic acid (PFOS); perfluorononanoic acid (PFNA); perfluorodecanoic acid (PFDA); 6:2 fluorotelomer sulfonic acid (6:2 FTSA); and hexafluoropropylene oxide dimer acid (HFPO-DA, alsoknown as a GenX chemical, with chemical name 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoic acid). In some embodiments, the contaminant comprises an organic compound, optionally a pharmaceutical or pesticide molecule including one or more selected from the group consisting of: diclofenac, erythromycin, oestrogens, oxadiazon and thiamethoxam. The contaminant may in some embodiments be a metal or metalloid ion, optionally selected from copper, iron, lead, mercury, chromate or arsenate.

[0056] The term ‘fluid stream’ or feedstream’ refers to a flowable substance, suitably a liquid, including an aqueous liquid, in which the target substance is dissolved, suspended, emulsified, dispersed, or otherwise carried. Typically, the liquid contains water, or is predominantly water based, and may be in the form of: contaminated water; waste water; drinking water; seawater; and / or industrial or agricultural runoff.

[0057] The term ‘sorption’, ‘sorb’, ‘sorbent’ and derivatives as used herein refer to the removal of target substances such as contaminants from the fluid stream by the association of said target substances with the modified support material described. Sorption by the material may happen by any means, for example by adsorption to the surface of the material, which may be by the creation of chemical interactions between the target substance and the support material, including electrostatic attraction, hydrophobic interactions, the formation of covalent bonds, ligation, chelation, van der Waals forces, hydrogen bonds, or otherwise. ‘Sorption’ may also refer to absorption of the target substance into the material. The target substance may become physically trapped inside intermolecular space, pores or other voids within the material. In particular, sorption may be adsorption occurring by the formation of chemical interactions between the target substance molecule and the sorbent molecules as defined herein with which the sorbent material has been modified. Such chemical interactions lead to the sequestration of the target substance within the sorbent material and out of the fluid stream. Use herein of the term ‘adsorption’ or derivatives thereof is not intended to be bound by any theoretical limitation, but rather is intended to include sorption by other means, as defined above, except where otherwise specified.

[0058] The term ‘sorbent material’ as defined herein refers to a material comprising a support or substrate material, which further comprises a sorbent molecule attached or bonded thereto. The sorbent material is suitable for contacting a fluid stream that comprises a target substance, such as a contaminant, which may be a PFAS, such that the target substance is adsorbed onto or otherwise taken up from the fluid stream and sequestered by the sorbent material. Suitably the sorbent material is deployed within a filter / purifier and / or a bed or a packed column (e.g. including a plurality of stacked filters) and the fluid stream is passed through or across the filter, bed or packed-column. The sorbent material may be deployed within a mixed bed combined with another adsorbent material such as granular activated carbon or an ion-exchange resin. In one embodiment the sorbent material is comprised within a prepared component such as a filter cartridge, so that used sorbent material can be conveniently contained, and similarly replaced or replenished with fresh or regenerated sorbent material asnecessary. Alternatively, the sorbent material may be added to the fluid as a dispersion. The sorbent material may be particulate, that is to say in the form of granules; flakes; beads; pellets; or pastilles. The sorbent material may be a powder which can advantageously provide higher accessible surface area. The sorbent material may be incorporated into a membrane, or membrane-like filter. Membranes comprised of the substrate material can also be functionalised as described herein directly. In particular, a membrane or membrane-like product, can be used to make filters. An advantage of filters of this kind is that they can be made with specific thickness, and with a large surface area, while also ensuring that fluid passes through when appropriately installed in a fluid flow path with minimum reduction in flow rate. Further, filters can combine the functionality of the invention with particulate (size exclusion) removal capabilities. The filtration bed or column may be occasionally backflushed, to clear build-up of occlusions, such as organic matter or lime scale, that reduce flow rate.

[0059] In one embodiment, the sorbent material is particulate, suitably granular in form, with an average diameter size of the particles or granules, (as measured by DLS) is greater than about 0.01 mm, suitably greater than about 0.1 mm, and typically less than about 5 mm, less than around 3mm, and optionally less than about 1 mm, or even less than around 700 pm. In one embodiment of the invention the granules have a d50 average particle size of around 600 pm in diameter.

[0060] In a further embodiment, the sorbent material is particulate, suitably powder in form, with an average diameter size of the particles (as measured by DLS) greater than about 0.1 pm, suitably greater than about 1 pm, optionally greater than 50 pm and typically less than about 300 pm. Typically, powdered iron oxide or iron oxide-hydroxide or iron hydroxide containing materials suitable for use in embodiments of the present invention have a d50 average particle size of around 100 pm, optionally a majority of particles within the powder are over around 70 pm in diameter but less than around 300 pm. Powdered iron oxides or iron oxide-hydroxides or iron hydroxides may include powders having spherical particles.

[0061] In a further embodiment, the sorbent material is a particulate composition, suitably spheroidal or spherical in form, with an average diameter size of the spheroids (as measured by DLS) greater than about 0.5 mm, suitably greater than about 1 mm and up to around 5 mm in size.

[0062] In one embodiment of the present invention there is provided a composition for removal of target substances and / or contaminants from a fluid stream. The composition comprises a sorbent material comprising a support material covalently linked to a target substance sorbent molecule. The support materials have high surface area to volume ratio and therefore provide an efficient support for molecules which are able to act as sorbents for target substances. The granular sorbent particles are designed to be deployed as a sorbent media for wastewater treatment in a standard packed bed and may also be suitable for treatment of other fluid streams, including drinking water. The granules have some porosity but are hard, durable and resistant to degradation. Larger granular sorbent media are also suitable for large scale engineered applications (e.g. purification of water at industrial or municipal sites). Whereas,smaller particle sizes provide faster capture kinetics allowing for creation of broad-spectrum target substance removal products for the point-of-use (POU) and / or point-of-entry (POE) markets.

[0063] According to embodiments ofthe invention, the sorbent material may be able to be incorporated directly into a POU device, such as a cartridge-type filter, or made compatible with third party technology so as to be encapsulated within a sandwich membrane (e.g. a functionalised iron oxide and / or iron oxidehydroxide and / or iron hydroxide bed between porous metal foil membranes), which then can be configured into a POU device. The design of a typical POU device should be suitable for connection to a typical household tap / faucet or supply pipe under the sink. The POU device and its components must withstand an inlet pressure of up to 6 bar (87 psi) without leakage or structural damage. This pressure is representative of the upper range of pressures found in most domestic settings. Since taps / faucets have varying supply pressure, the POU device must also function at the lower range of inlet pressures, as low as 1.4 bar (20 psi). Typical devices specify a range of inlet pressures from 1.4 bar to 5.5 bar (80 psi), with some rated up to 6.8 bar (99 psi). The minimum acceptable flow rate for most consumers is around 2 L / min, however some devices can treat at rates of up to 3 to 4 L / min. Almost all currently available products operate with a lifetime of 6 months (i.e. twice per year replacement). Given the unexpectedly high PFAS capacity ofthe compositions ofthe present invention, it is expected a product lifetime of 6 to 12 months is readily achievable. To last 12 months, around 4400 L of water (approximately 1200 US gallons) should be treated, which requires the device to demonstrate adequate treatment of 5280 L (20% greater capacity) of water before PFAS breakthrough in accordance with the NSF-53 certification test. In a specific embodiment ofthe invention, a POU device may be connected between an existing conventional water purification cartridge (which is not intended to remove PFAS) and the tap / faucet. In this configuration the POU device may provide an indication when replacement is required - e.g. based upon time or volume of flow through the device, or both. At this point the user may replace a cartridge that comprises the compositions ofthe invention without need to remove any piping connections. Spent cartridges may be regenerated according to methods described herein.

[0064] For POE applications, where water enters a building and the system continuously treats the water for the entire water supply to the building, the sorbent material may be comprised within a fiberglass reinforced plastic (FRP) cylindrical tank or cylinder. The amount of sorbent material may be designed to be used within an off-the-shelf FRP cylinder configuration which will, typically, allow for a capacity of around 10 to 20 litres of material to be held and which could have an operational life of one or more years of normal domestic use before the sorbent material needs to be replaced or regenerated. Atypical POE system may comprise a plurality of water treatment cylinders, the sorbent material may be comprised within all cylinders as a sub-component, or within one of the plurality of cylinders as a specialised component.

[0065] As used herein, the term “iron oxide” refers to the various mineral forms comprising iron ions (particularly Fe3+and Fe2+) and oxide ions (O2). The term iron oxide includes, for example, Hematite (a-Fe2O3), Maghemite (y-Fe2O3), and Magnetite (Fe3O4), Wustite (FeO), and combinations thereof. The term ironoxide-hydroxide refers to the various mineral forms comprising iron ions (particularly Fe3+and Fe2+), oxide ions (O2) and hydroxide ions (OH ), or combinations thereof. The term, iron oxide-hydroxide includes, for example, Goethite (a-FeO(OH)), Lepidocrocite (y-FeO(OH)), Akageneite (p-FeO(OH), (Akageneite also typically includes a small amount of chloride or fluoride ions) Feroxyhyte (6-FeO(OH)), and Ferrihydrite (Fe2O3.nH2O), or combinations thereof. Iron hydroxide is commonly found in the form, Fe(OH)2, and adopts a brucite structure. Fe(OH)2 may also be oxidised to its Fe3+form. The monohydrated form of iron oxide-hydroxide, FeO(OH).H2O, may also be referred to as iron (III) hydroxide. Iron oxide, iron oxide-hydroxide and iron hydroxide may be represented by the general formula FexOy(OH)z.n(H2O) where x is generally 1 or 2 or 3, is y is generally 0 or 1 or 2 or 3 or 4, z is generally 0 or 1 or 2 or 3, and n represents the number of water molecules associated with the iron complex which may be 0 or a positive real number and may be variable.

[0066] The sorbent compositions of the invention comprise a solid iron oxide or iron oxide-hydroxide or iron hydroxide support, or combination thereof, having a plurality of pores - i.e. cavities, channels or interstices which are deeper than they are wide. The pores are defined by a pore width / size / diameter which is typically considered to represent the distance between two opposite walls of the pore (e.g. diameter of cylindrical pores or a width of slit-shaped pores). Iron oxide and iron oxide-hydroxide and iron hydroxide, like most porous materials, may be divided into having micro-, meso- or macropores. Mesoporous materials are characterised by IUPAC as having predominance of pores with widths in the range of between 2 and 50 nm (Roquerol et al. (1994) Pure & Appl. Chem. 66(8): 1739-1758).

[0067] In embodiments of the invention, the iron oxide or iron oxide-hydroxide or iron hydroxide support material, or combination thereof, is comprised of a mesoporous iron oxide or iron oxide-hydroxide or iron hydroxide in which a majority of pores are greater than 2 nm in diameter, suitably greater than 3 nm in diameter, typically greater than 4 nm in diameter, optionally greater than 10 nm. By ‘majority’ it is meant that greater than 50% of the porous volume of the material is comprised within the mesoporous range as defined, typically greater than 60%, 70%, 80% and optionally greater than 90%.

[0068] In specific embodiments of the present invention the iron oxide or iron oxide-hydroxide or iron hydroxide support material, or combination thereof, has a granular particle size range of around 300 to 3000 pm for so called larger particles, and a particle size range of from around 0.1 to 300 pm for so called smaller particles, e.g. powders. As described previously, smaller particles show utility as components within the design and manufacture of POU filtration devices, whereas the larger particles may be utilised in packed beds for POE, industrial or municipal scale purification plants. In specific embodiments of the invention, a filtration device may comprise a combination of any one of the sorbent materials. Surface areas and porosities can be determined by gas adsorption-desorption methods such as the Brunauer-Emmett-Teller (BET) technique and mercury intrusion porosimetry, or typically a combination of such techniques. BET is a theory relating to gas adsorption onto a solid surface and essentially expands on Langmuir theory to include multi-layer formation. Mercury (Hg) intrusion is a physical technique which assesses pore size / volume through the interpenetration of the material with liquid Hg.The support material is linked to a sorbent molecule that is comprised of a polymer core, suitably a linear or branched polymer. The core polymer may be selected from one or more of the group consisting of: poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); poly(vinylchloride); poly(ethylenimine); poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4-vinylpyridine).

[0069] In specific embodiments of the invention the core polymer comprises a linear or branched polyamine that functions as the structural core of the sorbent molecule. Polyamines are compounds comprising more than two amino groups. In embodiments of the present invention, the sorbent molecules comprise a polyamine core with a molecular weight greater than 500 Daltons (Da). In specific embodiments of the invention, the polyamine core is comprised of a polymer having a weight average molecular weight of greater than: 1 kDa, 2 kDa, 3 kDa, 5 kDa, 8 kDa, 10 kDa, 12 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 40 kDa, 50 kDa, 75 kDa, 100 kDa, 250 kDa, 500 kDa, 750 kDa, 1000 kDa or more. In a specific embodiment the polyamine core has a weight average molecular weight of around 25 kDa or more. Highly branched polyamine polymers, sometimes termed ‘dendrimers’, comprise a plurality of primary amino groups on each polymer molecule and may be utilised in specific embodiments. The polyamines utilised in the sorbent molecules of the invention comprise at least one terminal amine.

[0070] In one embodiment of the invention the polyamine core comprises polyethylenimine (PEI), also known as polyazaridine or poly(iminoethylene). Suitably the PEI is a linear or branched PEI. Optionally, the core polymer comprises a poly(ethyleneimine) having a weight average molecular weight of around 25 kDa.

[0071] Scheme 1 below shows an initial synthetic procedure, according to an embodiment of the invention, employed to surface functionalise the FexOy(OH)z.n(H2O) substrate to allow for binding of a core polymer. A first step is the functionalisation of the FexOy(OH)z.n(H2O) support surface. The initial functionalisation of the FexOy(OH)z.n(H2O) surface is not limited to use of an organosilane. People skilled in the art will appreciate that oxide surfaces readily react with carbonyl containing compounds (aldehydes, carboxylic acids) and phosphorus containing compounds (e.g. phosphonic acids, esters etc).

[0072] Scheme 1: Synthesis of the functionalised iron oxide or iron oxide-hydroxide or iron hydroxide substrate (FexOy(OH)z.nH2O), or combination thereof (any counter ions omitted for clarity).SteP1

[0073]

[0074]

[0075] R1 and R2 and R3 may be the same or different. Suitably, R1 , R2 and R3 may be one or more groups selected from: a substituted or unsubstituted C1-C20 alkyl group, optionally a substituted or unsubstituted C1-C12 alkyl group; a substituted or unsubstituted C2-C20 alkenyl group, optionally a substituted or unsubstituted C2-C12 alkenyl group; a substituted or unsubstituted C2-C20 alkynyl group, optionally a substituted or unsubstituted C2-C12 alkynyl group; a substituted or unsubstituted C1-C20 alkoxy group, optionally a substituted or unsubstituted C1-C12 alkoxy group; a substituted or unsubstituted C1-C20 acyl group, optionally a substituted or unsubstituted C1-C12 acyl group; a substituted or unsubstituted aromatic hydrocarbon group; a substituted or unsubstituted aromatic group; a heterocyclic group; and a hydrogen atom. In a specific embodiment, R1 is an C1-C12 acyl group, R2 is an alkyl group or a hydrogen atom and R3 is not present. In another specific embodiment, R1 , R2 and R3 are all C1-C12 alkyl groups. As the polymer will vary in size, the above scheme shows as an approximation as defined within the square bracket. It will also be appreciated that the above scheme, whilst depicting branched polymer, is applicable also to use with linear polymers, e.g. linear PEI.

[0076] Step 1: Organosilanes are suitable reagents for functionalisation of the FexOy(OH)z.n(H2O) surface as they are diverse in structure and readily available at scale. A functionalised organosilane is typically chosen so that once it is attached to the inorganic oxide surface the appended functional group serves as a point for further synthetic modification (described in Step 2 below). Reactive functional groups can be chosen from, but are not limited to: chloride; bromide; iodide; protected alcohol group; ester; epoxide; acrylamide; alkene; and alkyne. It will be appreciated that alternative chemistries for functionalisation of the substrate surface may also be adopted and are known to the skilled person.The reactive functional group, in this example chloride, can be subsequently substituted by a wide range of nucleophiles. Nucleophiles, such as amines, or alcohols readily react with alkyl chlorides to form a carbon-nitrogen or a carbon-oxygen bond through a SN2-type nucleophilic substitution. It will be appreciated that it is possible to select organosilanes with other reactive functional groups (see the list above). In one embodiment, 2-propanol is the chosen solvent for the reaction, but the reaction may be performed in other alcohol containing solvents, or hexane, toluene or even in water.

[0077] Step 2: The silane functionalised FexOy(OH)z.n(H2O) substrate is suitably reacted with a core polymer (e.g. as defined within square brackets in the scheme shown above) that contains one or more functional groups that can be derivatised further by addition of at least one sorbent group. Such core polymers can be selected from the group: poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); poly(vinylchloride); poly(ethyleneimine); poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4-vinylpyridine). Core polymers containing nitrogen atoms are particularly suitable as these can be derivatised further once linked to the silane functionalised FexOy(OH)z.n(H2O) materials. Suitable weight average molecular weight ranges of the polymers are: PEI (0.8-1000 kDa); and PVP (around 60-160 kDa).

[0078] Step 3: The FexOy(OH)z.n(H2O) intermediate containing the attached core polymer can be derivatised further to introduce sorbent groups to improve specificity of binding to particular target substances present in a fluid feedstream. If the core polymer chosen in Step 2 is a polyamine, the polyamine-FexOy(OH)z.n(H2O) intermediate can be reacted with compounds such as acid chlorides (including, but not limited to, alkanoyl chlorides) to install amide functional groups, or by reaction with organohalides, hydrocarbon groups (e.g. alkyl, alkenyl, alkynyl, cycloalkyl or aryl groups) of various length or size can be introduced. The amine nitrogen atoms are versatile in that they can be derivatised by a wide range of reagents. Hence it is possible to derivatise the amine nitrogen centres through reaction with other reagents, such as: reductive amination with aldehydes to install alkyl chains; condensation with carboxylic acids to yield amides; Michael addition with double-bond containing compounds; addition to alkynes or alkenes; amidation reaction with esters (or other carbonyl containing compounds); reaction with strained cyclic systems; e.g. epoxides; aziridines; or reaction with organohalides: e.g. alkyl; benzyl; aryl etc. Hence, addition of different sorbent groups can be tailored to the particular target substances that are to be removed from the fluid stream.

[0079] It is a considerable advantage that sorbent compositions of the invention possess unique properties of sorbency that may be tuned to the specific requirements of the sorbent material. Hence, it is an advantage of the present invention that the sorbent material may be readily optimised to target specific substances and / or contaminants within a fluid stream by modifying the chemistry of the sorbent molecule. For example, sorbency properties can be optimised toward particular target substances via the combined selection of FexOy(OH)z.n(H2O) properties (e.g. pore size), core polymer and / or sorbent group. In this way the physical properties of the support material synergise with the chemical properties of the sorbent molecule in order to provide unexpected properties in terms of target specific sorbency.These are most evident in embodiments of the invention described in detail below, where certain compositions show improved performance in the removal of a range of PFAS from water when compared to industry standard activated carbon compositions. According to specific embodiments of the present invention the primary targets for treatment in water supplies are poly or perfluorinated surfactants such as one or more PFOA, PFOS, PFPeA, PFHA, PFHS, PFBA, and PFBS. According to further embodiments, the primary targets for treatment in water supplies are poly or perfluorinated surfactants such as, 6:2 FTSA and HFPO-DA.

[0080] It is also envisioned that treatment of runoff, wastewater or other water supplies to remove other target substances, contaminants or valuable substances (including precious or rare earth metals, for example present in wastewater from mining, purification or manufacturing processes), ortreatment of otherfluids such as biological media, organic solvents and oils or removal of impurities from liquid product streams, is possible. In addition, sorbent material according to the present invention could be used as a sorbent to remove target substances from a gaseous feedstream, such as carbon dioxide in direct air capture (DAC) apparatus.

[0081] Unlike other sorbents deployed in this way for organic pollutants, the sorbent material can be effectively regenerated in situ with a solvent wash step. The solvent wash can comprise an aqueous salt wash, an acid wash, a basic wash, or a combination, such as a salt and acid wash. The regeneration solution may further, or alternatively, comprise a non-aqueous polar solvent, such as acetone or an alcohol, such as ethanol, methanol or iso-propanol may be used. Suitably, where an aqueous wash is used the wash can comprise a liquid having a pH greater than 9, or alternatively a pH of less than 5. Optionally the wash solution comprises an aqueous ammonium hydroxide, ammonium acetate, ammonium chloride, ammonium sulphate potassium hydroxide, sodium bicarbonate or sodium hydroxide solution. In some embodiments, the wash liquid has a pH greater than 8, suitably greater than 9, or greater than 10. Where an acid wash is used it is suitably selected from an inorganic acid including hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid or alternatively an organic acid suitably selected from acetic acid, hexanoic acid, ethanedioic acid or citric acid. The salt is suitably selected from a sodium, potassium or magnesium salt with a chloride, sulphate or phosphate counter ion. The possibility of regeneration is particularly advantageous, in that it allows for the removal of target substances for recycling, recovery or safe disposal, as well as allowing the reuse of the sorbent material. In this way the proposed method for removing target substances is further reduced in cost, and in production of waste in the form of spent sorbent material.

[0082] The regeneration process suitably includes removing the sorbent material from the fluid stream and contacting it with a washing solvent as described. In an alternative embodiment, the regeneration process involves replacing the fluid stream with a solvent wash for a period of time to effect regeneration.Without wishing to be bound by theory, the adsorption of target substances to compositions as described herein appears to be the result, primarily, of non-covalent interactions, such as electrostatic interactions, with the polyamine core combined with hydrophobic-hydrophobic interactions with the covalently linked hydrophobic group. In the regenerating solvent wash step, interactions with polar groups such as anions in the wash substitute for the electrostatic interactions with anionic target substances, releasing the target substances in the wash. Raising or lowering the pH changes the protonation state of the polyamine core, which may further reduce the electrostatic binding interactions with the adsorbed target compounds. The presence of other ions such as ammonium, can improve the solubility of adsorbed target compounds, further increasing their removal in the regenerating solvent wash step.

[0083] Another salient advantage of the present system is its low cost and ease of production. Production of granules or other forms of sorbent material with a relatively low-cost core polymer and very low-cost support material (e.g. FexOy(OH)z.nH2O, which are lower in comparison to other materials, including alumina whose production is energy-intensive) allows cost effective production of the material at large scale (~1000 kg per batch) allowing deployment in large volume wastewater applications (megalitres / day flow rate). Therefore, the carbon footprint of iron-based materials is relatively low, particularly compared to alumina-based materials. The carbon footprint of iron oxides principally lies in mining processes or chemical synthetic processes. Iron oxide may also be isolated as a by-product of steel manufacture. Iron oxide-hydroxides occur naturally or may be produced synthetically and isolated using precipitation. Iron hydroxides may be synthesised more straightforwardly from iron salts without need for high temperatures. In addition, the reactions involved with linking the sorbent substrate with the target substance-sorbent molecules may be carried out in large scale and, economically, often at relatively low temperatures (e.g. less than 100°C) and at atmospheric pressures.

[0084] Additional benefits of the present invention which employs FexOy(OH)z.nH2O resides in the magnetic properties of the support material, which may range from weak to strong depending on its composition and solid state structure and Fe oxidation states. In certain embodiments and applications, such magnetic properties may be useful in water treatment as they may simplify the separation and recovery of materials, enhancing operational efficiency. The inherent, strong affinity of iron-based materials for arsenic and phosphates provides an additional benefit of the invention for water treatment.

[0085] The invention is further illustrated by the following non-limiting examples.

[0086] EXAMPLES

[0087] Physical characterisation of iron oxide or iron oxide-hydroxide or iron hydroxide support materialThe physical properties of the raw FexOy(OH)z.nH2O substrates sourced and selected for functionalisation are shown below in Table 1.

[0088] Table 1 Properties of support materials

[0089]

[0090] [1] BJH and BET analyses were performed using a Micromeritics Gemini VII surface area analyser using nitrogen as the adsorbate at liquid nitrogen temperature. All samples were degassed at 60 °C under vacuum until a constant weight was achieved prior to analysis.

[0091] [2] Mercury Intrusion Porosimetry measurements were carried out using MicroActive AutoPore V 9600 Version 2.03.00.

[0092] Surface areas and porosities can be determined by gas adsorption-desorption methods such as the Brunauer-Emmett-Teller (BET) technique and mercury intrusion porosimetry, or typically a combination of such techniques. BET is a theory relating to gas adsorption onto a solid surface and essentially expands on Langmuir theory to include multi-layer formation. Mercury (Hg) intrusion is a physical technique which assesses pore size / volume through the interpenetration of the material with liquid Hg (see Figure 4).

[0093] The BET method is applicable to adsorption isotherms of type II (disperse, nonporous or macroporous solids) and type IV (mesoporous solids, pore diameter between 2 nm and 50 nm). BET and full adsorption isotherms are routinely used to measure surface area, total pore volume, mesopore volume, area and distribution, and micropore distribution. Pores with widths exceeding about 50 nm (0.05 pm) are called macropores; pores of widths between 2 nm and 50 nm are called mesopores; pores with widths not exceeding about 2 nm are called micropores.

[0094] For materials having larger pore sizes, mercury intrusion porosimetry is recommended and covers the approximate range 3 nm to 600 pm (mesoporous to macroporous materials) - the larger size being dependent on the nature of the sample. Results provide porosity, pore size, pore area and pore volume. An alternative method for the determination of the total pore volume of a sample is by the combinationof mercury pycnometry (bulk density measurement) and helium pycnometry (absolute density measurement).

[0095] Materials with a high proportion of mesopores (2-50 nm) are desired. The pores should be of sufficient size to accommodate the sorbent molecules used in the functionalisation derivatisation steps and remain sufficiently large post-functionalisation to capture the target contaminant molecules (e.g. PFAS molecules) with high capacity.

[0096] The class of large FexOy(OH)z.nH2O particles can be broadly classified as having surface areas of 160 -240 m2 / g, with pore volumes 0.24-0.42 cm3 / g BET analysis shows that Substrate 5 has the smallest mesopores (average size = 11.34 nm), Substrate 6 has an average mesopore size of 24.89 nm, whereas the Supplier 1 iron hydroxides have average pore sizes of 16-47 nm.

[0097] FexOy(OH)z.nH2O materials are best described as either being predominantly mesoporous (Substrate 2, Substrate 5 and Substrate 6) or containing a mixture of meso and macropores (Substrate 1 , Substrate 3 and Substrate 4). The alumina material is different in that it contains smaller mesopores (peak at ca.

[0098] 5 nm), but larger macropores (1-10 micron) compared to the FexOy(OH)z.n(H2O) raw materials.

[0099] X-ray diffraction (XRD) experiments, as shown in Figure 5, confirm the crystallographic phases present in the various FexOy(OH)z.nH2O samples. Table 1 , below, demonstrates which phases are present in each sample. Some of the content of the FexOy(OH)z.nH2O support material of the invention may also contain at least some or entirely comprise amorphous content.

[0100] Table 2: Crystal phases present in FexOy(OH)z.n(H2O) raw materials111

[0101]

[0102] [1] XRD measurements were carried out using a Bruker D8 ECO XRD machine using copper X-rays at 40 kV 25 mA and a solid state Si detector.

[0103] Materials with a particle size of approximately 1000 - 50 pm, optionally 500 - 100 pm, is desired. The granules should be small enough to provide a large surface area for effective functionalisation of sorbent molecules and adsorption of the contaminant molecules, yet large enough not to cause a pressure drop when in use. Most of the FexOy(OH)z.nH2O materials are larger than 1000 pm, except for Substrate 4 that has significantly smaller particles and resembles a coarse powder. Substrate 6 contains multiple particle sizes, ranging from approximately 100 pm to >1000 pm. It is likely that the differences in particlesize between iron-containing raw materials will results in varied performance. Figure 6 contains particle size distribution plots of the various samples of FexOy(OH)z.n(H2O).

[0104] All of the Supplier 1 materials contain a high concentration of metal impurities, mostly calcium, magnesium manganese and silicon. Substrate 3 has the highest concentration of metal impurities overall, while Substrate 6 iron oxide is very pure. Figure 7 contains ICP-OES plots demonstrating the metal impurities of the various FexOy(OH)z.n(H2O) samples.

[0105] Example 1 - Functionalisation and derivatisation of large granular FexOy(OH)z.nH2O particles

[0106] Scheme 2: Synthesis of the hexyl-PEI-functionalised iron oxide or iron oxide-hydroxide or iron hydroxide substrate (FexOy(OH)z.nH2O), or combination thereof (any counter ions omitted for clarity).

[0107] Step

[0108]

[0109]

[0110] Family 1 testing (large granular FexOy(OH)z.n(H2O)):

[0111] Batch test data for a family of materials is shown in Figure 1. FexOy(OH)z.nH2O substrate characterisation data is displayed in Table 1 (above) and the characterisation data for functionalised materials is displayed in Table 2 (below). As shown in Figure 2 the raw FexOy(OH)z.nH2O materials are unable to remove PFAS from water, so cannot be used successfully without being functionalised for PFAS removal applications. Figure 3 shows that for one iron oxide-based material, intermediate Step 2 functionalisation results in a similar inability to remove PFAS from water. The batch test data in Figure 1 and Figure 3 demonstrate that functionalisation of the FexOy(OH)z.nH2O substrates result in improvedPFAS removal properties versus the raw unfunctionalised FexOy(OH)z.nH2O substrates and intermediate materials (PEI-FexOy(OH)z.n(H2O)).

[0112] The materials in Figure 1 were prepared using 3-chloropropyltrimethoxysilane activation of FexOy(OH)z.nH2O (Step 1, Scheme 2), 25 kDa PEI (Step 2, Scheme 2) and functionalised with 1-bromohexane (Step 3, Scheme 2).

[0113] Different FexOy(OH)z.nH2O substrates were trialled to demonstrate that the chemistry is applicable to several different FexOy(OH)z.nH2Osubstrates. The batch test data is shown in Figure 1. Characterisation of the unfunctionalised FexOy(OH)z.nH2O substrates is given in Table 1 (above) and characterisation of the products are shown in Table 2 (below).

[0114] All functionalised FexOy(OH)z.nH2O materials successfully removed PFAS from water, however the performance of the materials under static conditions varied significantly. Using Alumina Reference Supplier, an inhouse-prepared material (as in WO 2023 / 156572 A1) as a benchmark, Functionalised Substrate 3, Functionalised Substrate 4 and Functionalised Substrate 6 performed well in comparison. This cannot be attributed purely to particle size or porosity, as this differs for the Substrate 3, Substrate 4 and Substrate 6. All other functionalised materials performed less well in comparison.

[0115] Table 2 Characterisation of representative materials

[0116]

[0117]

[0118] The elemental analysis shows that all FexOy(OH)z.nH2O materials have been successfully functionalised. It is possible to determine the degree of functionalisation by considering the carbon content of the sample. By using the Alumina Reference Supplier material as a benchmark, we observe that the Supplier 1 based materials contain higher levels of carbon for all three steps, with the carbon content after step 3 being approximately a third higher than for the alumina material. Functionalised Substrate 6 was not functionalised to the degree of the Supplier 1 materials, but it is most similar to Reference Functionalised alumina.

[0119] By subtracting the wt% C content of Step 2 from each hexylated material, we can determine the wt% C added during hexylation. Functionalised Substrate 3 has the largest increase of 7.17% (compared to 5.83% for Alumina Reference Substrate), whereas Functionalised Substrate 5 had only a 2.20% increase. Therefore, the Substrate 3 material has been functionalised most successfully and the Substrate 5 material has been functionalised less well. The differences in performance of functionalised materials across the tested substrates could be attributed to factors such as the degree of functionalisation, substrate’s particle sizes and porosities, or a combination of them.

[0120] Materials and Methods

[0121] Silanisation reactions (Step 1 , Schemes 1 and 2). In this step the raw iron oxide / iron hydroxide is surface modified with 0.15 mmol / g (3-chloropropyl)trimethoxysilane (CPTMS), endowing the solid with an alkyl halide which will be reacted in the subsequent step.

[0122] A quantity of FexOy(OH)z.nH2O is weighed into a 2-neck round bottomed flask of appropriate size. The flask is placed in a heating block on a hotplate and attached to an overhead stirrer. A solution of the silane in IPA is prepared with a typical ratio of 2:1 of solvent to solids, e.g. for 100 g of FexOy(OH)z.nH2O, 200 mL of IPA is used. The mixture is heated at 65 °C, with stirring at 100 rpm for 18 hours. Once the reaction completes, the solid is retained and the solution is discarded. The solid is filtered and dried in an oven overnight.

[0123] PEI reactions (Step 2, Schemes 1 and 2) In this step the silanised FexOy(OH)z.nH2O is reacted with 24 pmol / g PEI (Mn = ca. 10000 Da, Mw = ca. 25000 Da) through the reaction of the chloropropyl group with an amine from the PEI. This endows the FexOy(OH)z.nH2O with a polymer coating which will later be further functionalised.An amount of PEI is weighed and put into a duran bottle to which DI water is also added (2:1 ratio by volume of water to the mass of FexOy(OH)z.nH2O). The duran bottle is placed into a heated sonicator bath to dissolve the polymer. Once the PEI is fully dissolved, a quantity of silanised FexOy(OH)z.nH2O from step 1 is weighed out and placed into a 2-neck round bottomed flask and the PEI solution is added. The reaction is heated at 70 °C, with agitation set to ~100 rpm for 18 hours. Once the reaction completes, the solid is retained and the solution is discarded. The solid is washed with DI water. After the washing process, the solids are collected by filtration and allowed to air dry before further drying them in an oven overnight.

[0124] Alkylation reactions (Step 3, Schemes 1 and 2) In this final step the PEI-modified FexOy(OH)z.nH2O is reacted with 12 mmol / g 1 -bromohexane thereby endowing the final product with hexyl chains rendering the material to have hydrophobic characterthat is tuned towards PFAS interactions. It is these alkyl chains and the subsequent hydrophobic and electrostatic interactions with PFAS which enable the material to capture PFAS from water at very low concentrations.

[0125] The PEI-functionalised FexOy(OH)z.nH2O is weighed out in an appropriate reaction container such as 3-neck round bottomed flask of appropriate size. Potassium carbonate (0.2 eq. with respect to bromohexane) is weighed out and added to the same flask. The flask is then placed on a heating block on a hotplate and equipped with a condenser and an overhead stirrer. A solution of bromohexane in acetonitrile (a ratio of 2:1 by volume of solvent to the mass of functionalised FexOy(OH)z.nH2O) is added to the solids, the temperature is set to 90 °C and the agitation is set to ~100 rpm. The reaction is allowed to proceed for 18 hours at 90 °C. Once the reaction completes, the solids are retained and the solution is discarded. The solids are washed four times using IPA with approximately 20 mins of agitation per wash cycle followed by eight wash cycles using DI water. The solids are finally collected by filtration and allowed to air dry before placing them into the drying oven overnight.

[0126] Batch testing The tests referred to as batch tests herein provide an indication of an adsorbent’s capacity for uptake of PFAS in a static environment. Briefly, 20 mg of the adsorbent, such as that prepared as described above, is weighed out and combined with 45 mL of an aqueous solution of PFAS of known concentration (typically a cocktail of 7 PFAS species). The solution also contains ions and total organic carbon (TOC) to mimic real-world conditions. The suspension is agitated on an orbital shaker for 24 hours and an aliquot of the liquid is taken for liquid chromatography mass spectrometry (LCMS) measurement of PFAS concentration. The percentage removal of PFAS is calculated by comparison with a sample of the same PFAS stock solution treated identically but with no adsorbent present.

[0127] Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. It iscontemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.

Claims

Claims:

1. A composition for removal of a target substance from a fluid stream, the composition comprising:a porous, solid and particulate support material comprising at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof; anda sorbent molecule that comprises a core polymer;wherein the core polymer is covalently linked to the porous, solid and particulate support material; andwherein the sorbent molecule further comprises one or more covalently linked sorbent groups.

2. The composition of claim 1 , wherein the porous, solid and particulate support material further comprises at least one crystal phase selected from the group consisting of: magnetite; maghemite; hematite; goethite, lepidocrocite, and akageneite.

3. The composition of claim 1 , wherein the porous solid and particulate support material is amorphous or at least partially amorphous.

4. The composition of any one of claims 1 and / or 2 and / or 3, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxidehydroxide, or combination thereof having a mesoporous content, in which a majority of pores within the mesoporous range are greater than 2 nm in diameter, suitably greater than 3 nm, typically greater than 4 nm in diameter, optionally greater than 8 nm in diameter.

5. The composition of any preceding claim, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof in which a majority of pores within the mesoporous range are less than 50 nm in diameter, suitably less than 40 nm in diameter, typically less than 30 nm in diameter, more typically less than 10 nm in diameter.

6. The composition of any one of claims 4 or 5, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof in which the average pore size, as determined by mercury intrusion, within the mesoporous range is between about 3 nm and about 10 nm, optionally between about 4 and about 9 nm.

7. The composition of claim 6, wherein the porous, solid and particulate support material has a Brunauer-Emmett-Teller (BET) pore volume of not less than around 0.20, suitably not less than around 0.30 and optionally not less than around 0.40 cm3 / g.

8. The composition of any one of claims 1 to 7, wherein the core polymer is selected from one or more of the group consisting of: poly(ethylenimine); poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); poly(vinylchloride); poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4-vinylpyridine).

9. The composition of claim 8, wherein the core polymer comprises a poly(ethylenimine) having a weight average molecular weight of not less than around 25 kDa.

10. The composition of any preceding claim, wherein the core polymer is selected from a linear or a branched polymer.

11. The composition of any preceding claim, wherein the covalently linked sorbent groups comprise one or more groups selected from: a substituted or unsubstituted C1-C12 alkyl group; a substituted or unsubstituted C2-C12 alkenyl group; a substituted or unsubstituted C2-C12 alkynyl group; a substituted or unsubstituted C1-C12 alkoxy group; a substituted or unsubstituted C1-C12 acyl group; a substituted or unsubstituted aromatic hydrocarbon group; a substituted or unsubstituted aromatic group; a heterocyclic group; and a hydrogen atom.

12. The composition of claim 11 , wherein the C1-C12 alkyl group is selected from a branched or straight chain C1-C12 alkyl group, optionally a branched or straight chain C1-C8 alkyl group.

13. The composition of claim 11 , wherein the acyl containing group is selected from a saturated or unsaturated branched or straight chain C1-C12 acyl group, optionally a branched or straight chain C1-C8 acyl group.

14. The composition of any preceding claim, wherein the core polymer comprises at least one tertiary amino group, and optionally wherein the at least one tertiary amino group is converted to a quaternary nitrogen.

15. The composition of claim 12, wherein the core polymer comprises C1-C10 alkyl substituted linear poly(ethylenimine).

16. The composition of claim 12, wherein the core polymer comprises C1-C6 alkyl substituted branched poly(ethylenimine).

17. The composition of claim 15 or 16, wherein the linear or branched PEI has weight average molecular weight of not less than around 1 kDa, optionally not less than around 25 kDa.

18. The composition of any one of claims 1 to 17, wherein porous, solid and particulate support material is in granular form.

19. The composition of any one of claims 1 to 17, wherein porous, solid and particulate support material is in powder form.

20. The composition of any one of claims 1 to 17, wherein porous, solid and particulate support material is comprised of spheroidal particles.

21. A composition for removal of a poly- and perfluorinated alkyl substance (PFAS) from an aqueous liquid, the composition comprising:a porous, solid and particulate support material comprising at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof having a mesoporous content, (i) wherein a majority of the pores are within the mesoporous range and have an average pore size between 2 nm and 50 nm; and(ii) wherein the porous, solid and particulate support material has a BET pore volume within the mesoporous range of not less than around 0.20 cm3 / g; and a sorbent molecule that comprises a linear or branched core polymer selected from one or more of: poly(ethylenimine); poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); polyvinylchloride);; poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4- vinylpyridine);wherein the core polymer is covalently linked to the porous, solid and particulate support material; andwherein the sorbent molecule further comprises one or more covalently linked sorbent groups.

22. The composition of claim 21 wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof having a mesoporous content in which a majority of pores within the mesoporous range are greater than 2 nm in diameter, suitably greater than 3 nm, typically greater than 4 nm in diameter, optionally greater than 10 nm in diameter.

23. The composition of claims 21 or 22, wherein the porous, solid and particulate support material is characterised by a majority of pores that are within the mesoporous range being less than 50 nm in diameter, and typically less than 20 nm in diameter, more typically less than 10 nm in diameter.

24. The composition of any one of claims 21 to 23, wherein the porous, solid and particulate support material has an average pore size within the mesoporous range, as determined by mercury intrusion, of between about 2 about 20 nm, suitably between about 3 and about 10 nm, optionally between about 4 and about 9 nm.

25. The composition of any one of claims 21 to 24, wherein the core polymer comprises a poly(ethylenimine) having a weight average molecular weight of at least around 25 kDa26. The composition of any one of claims 21 to 25, wherein the covalently linked sorbent groups comprise one or more groups selected from: a substituted or unsubstituted C1-C12 alkyl group; a substituted or unsubstituted C2-C12 alkenyl group; a substituted or unsubstituted C2-C12 alkynyl group; a substituted or unsubstituted C1-C12 alkoxy group; a substituted or unsubstituted C1-C12 acyl group; a substituted or unsubstituted aromatic hydrocarbon group; a substituted or unsubstituted aromatic group; a heterocyclic group; and a hydrogen atom.

27. The composition of any one of claims 21 to 26, wherein the core polymer comprises at least one tertiary amino group and wherein the at least one tertiary amino group is converted to a quaternary nitrogen.

28. The composition of claim 21 , wherein the core polymer comprises C1-C10 alkyl substituted linear poly(ethylenimine).

29. The composition of claim 21 , wherein the core polymer comprises C1-C6 alkyl substituted branched poly(ethylenimine).

30. The composition of claim 28 or 29, wherein the linear or branched PEI has weight average molecular weight of not less than around 1 kDa, optionally not less than around 25 kDa.

31. The composition of any one of claims 21 to 30, wherein the porous, solid and particulate support material is in granular form.

32. The composition of any one of claims 21 to 30, wherein the porous, solid and particulate support material is in powder form.

33. The composition of any one of claims 21 to 30, wherein the porous, solid and particulate support material is comprised of spheroidal particles.

34. A composition for use in the removal of a contaminant from an aqueous fluid stream, wherein the composition comprises:a) a porous, solid and particulate support material comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof; and b) a sorbent molecule comprising:i) a branched polyamine covalently linked to the porous, solid and particulate support material; andii) a hydrophobic group covalently linked to the branched polyamine.

35. A process for removal of a target substance from a fluid stream comprising contacting the fluid stream with a composition as defined in any one of claims 1 to 34, and wherein the target substance comprises one or more poly- and perfluorinated alkyl substances (PFAS).

36. The process of claim 35, wherein the fluid stream comprises water.

37. The process of any one of claims 35 or 36, wherein the PFAS is selected from a perfluorinated anionic surfactant compound, including one or more selected from the group consisting of: perfluorobutane sulfonate (PFBS); perfluorobutanoic acid (PFBA); perfluoropentanoic acid (PFPeA); perfluorohexanesulfonate (PFHS); perfluorohexanoic acid (PFHA); perfluorooctanoic acid (PFOA); perfluorooctane sulfonate (PFOS); perfluorononanoic acid (PFNA); and perfluorodecanoic acid (PFDA); 6:2 fluorotelomer sulfonic acid (6:2 FTSA); and hexafluoropropylene oxide dimer acid (HFPO-DA).

38. A process for removal of a target substance from a fluid stream comprising contacting the fluid stream with a composition comprising a porous, solid and particulate support material comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof and a sorbent molecule that comprises a core polymer; wherein the core polymer is covalently linked to the porous, solid and particulate support material; and wherein the sorbent molecule further comprises one or more covalently linked sorbent groups selected from one or more groups selected from: a substituted or unsubstituted C1-C12 alkyl group; a substituted or unsubstituted C2-C12 alkenyl group; a substituted or unsubstituted C2-C12 alkynyl group; a substituted or unsubstituted C1-C12 alkoxy group; a substituted or unsubstituted C1-C12 acyl group; a substituted or unsubstituted aromatic hydrocarbon group; a substituted or unsubstituted aromatic group; a heterocyclic group; and a hydrogen atom.

39. The process of claim 38, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof having a mesoporous content, in which a majority of pores within the mesoporous range are greater than 2 nm in diameter, suitably greater than 3 nm, typically greater than 4 nm in diameter, optionally greater than 8 nm in diameter.

40. The process of claims 38 or 39, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof in which a majority of pores within the mesoporous range are less than 50 nm in diameter, suitably less than 20 nm in diameter, typically less than 10 nm in diameter.

41. The process of any one of claims 38 or 39, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof in which the average pore size within the mesoporous range is between about 3 nm and about 10 nm, optionally between about 4 and about 9 nm.

42. The process of claim 41 , wherein the porous, solid and particulate support material has a BET pore volume of not less than around 0.20, suitably not less than around 0.30 and optionally not less than around 0.40 cm3 / g.

43. The process of any one of claims 39 to 42, wherein the porous, solid and particulate support material is comprised of at least an iron oxide, or an iron hydroxide or an iron oxide-hydroxide, or combination thereof in which the average pore size within the mesoporous range is between about 4 and about 9 nm.

44. The process of claim 43, wherein the porous, solid and particulate support material has a BET pore volume of not less than around 0.30, suitably not less than around 0.40 and optionally not less than around 0.50 cm3 / g.

45. The process of any one of claims 38 to 44, wherein the core polymer is selected from one or more of the group consisting of: poly(allylamine); poly(methylmethacrylate); poly(vinylalcohol); poly(vinylamine); poly(vinylchloride); poly(ethylenimine); poly(2-vinylpyridine); poly(3-vinylpyridine); and poly(4-vinylpyridine).

46. The process of claim 45, wherein the core polymer comprises a poly(ethylenimine) having a weight average molecular weight of not less than around 25 kDa.

47. The process of any one of claims 38 to 46, wherein the polymer is selected from a linear or a branched polymer.

48. The process of any one of claims 38 to 47, wherein the C1-C12 alkyl group is selected from a branched or straight chain C1-C12 alkyl group, optionally a branched or straight chain C1-C8 alkyl group.

49. The process of any one of claims 38 to 47, wherein the acyl containing group is selected from a branched or straight chain C1-C8 acyl group.

50. The process of any one of claims 38 to 49, wherein the core polymer comprises at least one tertiary amino group, and optionally wherein the at least one tertiary amino group is converted to a quaternary nitrogen.

51. The process of any one of claims 38 to 50, wherein the core polymer comprises C1-C10 alkyl substituted linear poly(ethylenimine).

52. The process of any one of claims 38 to 50, wherein the core polymer comprises C1-C6 alkyl substituted branched poly(ethylenimine).

53. The process of any one of claims 51 or 52, wherein the linear or branched PEI has weight average molecular weight of not less than around 1 kDa, optionally not less than around 25 kDa.

54. The process of any one of claims 38 to 53, wherein the porous, solid and particulate support material is in granular form.

55. The process of any one of claims 38 to 53, wherein the porous, solid and particulate support material is in powder form.

56. The process of any one of claims 38 to 53, wherein the porous, solid and particulate support material is comprised of spheroidal particles.

57. The process of any one of claims 38 to 56, wherein the fluid comprises water.

58. The process of any one of claims 38 to 57, wherein the target substance comprises one or more poly- and perfluorinated alkyl substances (PFAS).

59. The process of claim 58, wherein the PFAS is selected from a perfluorinated anionic surfactant compound, including one or more selected from the group consisting of: perfluorobutane sulfonate (PFBS); perfluorobutanoic acid (PFBA); perfluoropentanoic acid (PFPeA); perfluorohexanesulfonate (PFHS); perfluorohexanoic acid (PFHA); perfluorooctanoic acid (PFOA); perfluorooctane sulfonate (PFOS); perfluorononanoic acid (PFNA); and perfluorodecanoic acid (PFDA); 6:2 fluorotelomer sulfonic acid (6:2 FTSA); and hexafluoropropylene oxide dimer acid (HFPO-DA).

60. The process of any one of claims 38 to 59, wherein the porous, solid and particulate support material is comprised within a packed bed.

61. The process of any one of claims 38 to 60, wherein the porous, solid and particulate support material is comprised within a filter unit.

62. A filter for the adsorption of one or more PFAS from a contaminated water source, wherein the filter comprises a composition as described in any one of claims 1 to 44.

63. The filter of claim 62 wherein the filter is configured as a point-of-use (POU) filter.

64. The filter of claim 63, wherein the filter is comprised within a replaceable cartridge.

65. The filter of claim 64, wherein the filter is configured to be incorporated into a point-of-entry (POE) system.

66. The filter of any one of claims 62 to 65, wherein the filter comprises a combination of granular porous, solid and particulate support material and powdered porous, solid and particulate support material.

67. The filter of any one of claims 62 to 66, wherein the composition is comprised within a packed bed that is configured to permit a minimum water flow rate there-through of at least 2 litres / min.

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