Material adsorbent of perfluoroalkyl and polyfluoroalkyl substances

Abstract

The present invention relates to an adsorbent material comprising a support made of activated carbon or non-woven nanofibers, said support being impregnated with metal oxide nanoparticles, and said nanoparticles being functionalized by covalent bonding with polyfluorinated and / or polyalkylated phosphonic ligands.

Description

Title of the invention: Adsorbent material for perfluoroalkyl and polyfluoroalkyl substances FIELD OF INVENTION

[0001] The general field of the invention is that of materials adsorbing perfluoroalkyl and polyfluoroalkyl substances (PFAS), and their use for the purification of water and gases contaminated by said substances. STATE OF THE ART

[0002] Perfluoroalkyl and polyfluoroalkyl substances (designated by their acronym PFAS) are a group of synthetic organofluorine compounds comprising one or more per- or poly-fluoroalkyl functional groups. This group of compounds includes a large number of substances, among them perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

[0003] These fluorinated compounds have been widely used in various industrial applications and consumer products: textiles, food packaging, firefighting foams, refrigerants, non-stick coatings, cosmetics, medical devices, plant protection products, etc. These compounds have achieved widespread success due to their excellent surfactant properties, their key role as precursors of fluorinated polymers, and their chemical durability, due to the strength of the carbon-fluorine bonds they contain.

[0004] Unfortunately, these same properties make PFAS resistant to degradation in the environment, hence their designation as "forever pollutants." It is estimated that today most water intended for human consumption contains PFAS.

[0005] However, studies have established a link between the accumulation of PFAS in human organisms and various adverse effects on human health, including high cholesterol levels, a high risk of developing kidney or testicular cancer, and the onset of thyroid diseases.

[0006] Thus, the elimination of PFAS substances has become a public health priority. To date, no industrially scalable technology exists that allows for their complete destruction and elimination. Current development efforts are focused on techniques for isolating them in order to decontaminate water and gas.

[0007] Several technologies have been developed to remove PFAS compounds from the environment and drinking water. These include reverse osmosis as well as Nanofiltration. Other technologies use adsorbent materials such as activated carbon and ion exchange resins.

[0008] Activated carbon is known for its effectiveness in adsorbing per- and polyfluoroalkyl substances (PFAS). The adsorption mechanism of activated carbon relies primarily on physicochemical interactions, such as Van der Waals forces and hydrophobic forces, as well as on weaker chemical interactions. The adsorption performance of PFAS by activated carbon is influenced by several parameters, including the molecular weight and hydrophobicity of the target molecules.

[0009] In general, low molecular weight PFAS, such as perfluoropentanic acid (PFPEA), are less well adsorbed compared to higher molecular weight PFAS, such as perfluorooctanoic acid (PFOA).

[0010] The hydrophobicity of PFAS molecules also plays a crucial role in their adsorption. More hydrophobic molecules, characterized by longer fluorinated chains, exhibit an increased affinity for the hydrophobic surfaces of activated carbon, thus promoting better adsorption.

[0011] In conclusion, activated carbon allows for the efficient adsorption of PFAS with long carbon chains (comprising more than 8 carbons) and low polarity functional groups.

[0012] This is why other adsorbent materials must be developed to allow the adsorption of PFAS having short carbon chains and / or hydrophilic / polar functional groups.

[0013] The design of new adsorbent materials, based on porous supports functionalized by specific ligands, is currently under study.

[0014] The article (STEBEL, 2019) describes adsorbent materials composed of a porous silica resin (SOMS) functionalized by the bonding of fluorophilic or fluoroalkyl amide groups (F-SOMS) or cationic quaternary groups (QA-SOMS), or in combination with a cationic polymer (Poly-SOMS).

[0015] The article (GAGLIANO, 2020) compares the effects of different adsorbent supports: carbon, ion exchange resins, or metal oxide nanoparticles, which can be functionalized with fluorinated groups.

[0016] International application WO 2020 / 206317 describes adsorbent supports treated with metal oxides, intended to capture perfluoroalkyl substances (PFAS) contained in liquids or gases.

[0017] International application WO 2022 / 109392 describes an apparatus for trapping PFAS. Said apparatus contains adsorbent particles containing at least one compound selected from activated carbon and metal oxides, or a combination of the two.

[0018] International application WO 2023 / 107629 describes an adsorbent material for binding PFAS. This material consists of ceramic particles, functionalized by covalent bonding of a functional group to their surface, and also containing a metal selected from silicon (Si), aluminum (Al), titanium (Ti) or zinc (Zn).

[0019] The present application relates to new adsorbent materials, which have improved PFAS adsorption efficiency compared to activated carbon, and also better selectivity for the adsorption of low molecular weight PFAS and / or PFAS with hydrophilic groups. Description of the invention

[0020] The present invention relates to an adsorbent material comprising a support made of activated carbon or non-woven nanofibers, said support being impregnated with metal oxide nanoparticles, and said nanoparticles being functionalized by covalent bonding with polyfluorinated and / or polyalkylated phosphonic ligands.

[0021] The invention also relates to methods for preparing said adsorbent material.

[0022] According to a first aspect, the process for preparing the adsorbent material according to the invention comprises the following steps:

[0023] a) immersion of the support in a suspension comprising metal oxide nanoparticles in a solvent, preferably ethanol, to obtain a "charged support";

[0024] b) drying of the loaded support in two sub-steps, first at a temperature between 100°C and 120°C, then at a temperature between 200°C and 240°C;

[0025] c) immersion of the loaded and dried support in a suspension containing polyfluorinated or polyalkylated phosphonic ligands;

[0026] d) drying of the support obtained in step (c) at a temperature between 50 and 110°C, which allows the functionalization of the metal oxide nanoparticles;

[0027] e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

[0028] According to a second aspect, the process for preparing the adsorbent material according to the invention comprises the following steps:

[0029] a) preparation of a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated phosphonic ligands in a solvent;

[0030] b) optionally, vacuum drying at 40°C under rotation for solvent evaporation;

[0031] c) immersion of a support in a suspension containing the metal oxide nanoparticles functionalized with said ligands, then continuous homogenization by rotation;

[0032] d) drying of the loaded support obtained in step (c), preferably at a temperature between 50 and 110°C;

[0033] e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

[0034] According to a third aspect, in the case where the support is made of non-woven polymer nanofibers, the process for preparing the adsorbent material according to the invention comprises the following steps:

[0035] a) preparation of a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated ligands in a solvent;

[0036] b) optionally, vacuum drying at 40°C under rotation, for solvent evaporation;

[0037] c) homogenization of the polymer in solution using a mixer, and addition of metal oxide nanoparticles functionalized by polyfluorinated and / or polyalkylated phosphonic ligands;

[0038] d) electrospinning of the polymer loaded with functionalized nanoparticles obtained in step (c) to obtain nanofibers;

[0039] e) drying the nanofibers obtained in step (d), preferably at a temperature between 120 and 170°C, to obtain the crosslinking of the polymer;

[0040] f) washing the adsorbent material obtained with a suitable solvent, in particular deionized water.

[0041] The invention also relates to a method for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS) comprising bringing a liquid or gas likely to contain PFAS into contact with the adsorbent material as defined above, or as obtained by any of the methods described above.

[0042] Finally, the invention relates to the use of the adsorbent material according to the invention, or as obtained by one of the processes according to the invention, for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS) present in a liquid or a gas. DESCRIPTION OF FIGURES

[0043] [Fig. 1] [Fig. 1] shows the quantification of the zirconium dioxide (ZrO2) content of the charged activated carbon support (after step (b)), by thermogravimetric analysis. The support was charged with two quantities of ZrO2: 20% by weight (CA-ZrO2-01, dashed line) and 2% by weight (CA-ZrO2-03, solid line), relative to the total weight of the charged support. For this concentration, the results reveal a residual content of 2.6% by weight, very close to the theoretical value. target of 2%. This closeness between the measured and theoretical values ​​confirms an effective and controlled fixation of zirconium dioxide in activated carbon.

[0044] [Fig. 2] Figure 2 represents the specific surface area of ​​activated carbon loaded with 20% by weight of ZrO2 (point at 20%) and with 2% by weight of ZrO2 (point at 2%). The graph also shows the initial specific surface area (before loading) at 0%.

[0045] [Fig.3] Fig.3 illustrates the adsorption rate (%) of the PFOA compound by functionalized ZrO2 metal oxide (left, 96%) and by uncharged activated carbon (right, 75%).

[0046] [Fig.4] Fig.4 illustrates the performance tests carried out with the functionalized ZrO2 metal oxide used for the adsorption of PFOA. 1) Percentage of PFOA adsorption as a function of the initial concentration of PFOA (54, 140 and 300 ppm = mgL-1) simulating different pollution conditions; 2) Recovery rate (%) as a function of the initial concentration of PFAS (Co, in ppm).

[0047] [Fig.5] Measurement of the adsorption isotherm Qmax (mmol / g) of the functionalized metal oxide (grey squares) in parallel with the Langmiur model (black triangles).

[0048] [Fig. 6] Figure 6 illustrates the adsorption selectivity of virgin (uncharged) activated carbon for 14 different PFAS: PFBA, PFPeA, PFHxA, PFBS, PFHpA, PFPeS, PFOA, PFNA, PFHxS, PFHpS, PFDA, PFOS, PFUnDA, and PFUnDS. The breakthrough percentage represents the percentage of PFAS compound released as a function of the number of washes (volume of water added / volume of activated carbon). The breakthrough percentage must be less than 10% for PFAS adsorption to be considered satisfactory. This figure illustrates that uncharged activated carbon only effectively adsorbs high molecular weight PFAS (C8 to Cl1).

[0049] [Fig.7] Fig.7 illustrates the adsorption selectivity of the functionalized metal oxide. It represents the adsorption rate of PFOA (at C8), PFPeA (at C5) and an organic pollutant (bisphenol A) by virgin activated carbon (left) and by the functionalized metal oxide ZrO2 (right). DETAILED DESCRIPTION OF THE INVENTION

[0050] The adsorbent material according to the invention is innovative in that it contains specific ligands, in particular fluorinated phosphonic acids such as fluoroalkyl(ClO)phosphonic acid and pentafluorobenzylphosphonic acid, or hydrophobic fatty-chain ligands, or even fluorinated ionic liquids. These ligands were chosen for their unique chemical properties which increase the affinity of the adsorbent supports for PFAS.

[0051] The method adopted to functionalize the surface of the adsorbents involves grafting a metal oxide (MOX), preferably zirconium dioxide (ZrO2), in the form of nanoparticles or microparticles, with the ligands polyfluoro and / or polyalkylated phosphonics. This grafting process creates new adsorption sites, thereby increasing the selectivity and performance of the adsorbents.

[0052] Functionalizing these metal oxides with specific ligands improves the affinity of adsorbent materials for PFAS by multiplying the active sites and modifying the chemical surface of the material to promote interaction with these contaminants. This approach allows for better capture and removal of PFAS in water treatment applications.

[0053] More specifically, the present invention relates to an adsorbent material comprising a support made of activated carbon or non-woven nanofibers, said support being impregnated with metal oxide nanoparticles, and said nanoparticles being functionalized by covalent bonding with polyfluorinated and / or polyalkylated phosphonic ligands.

[0054] This material is intended to adsorb per- and polyfluoroalkyl substances (PFAS), present in a liquid or gas, in order to purify said liquid or gas of these undesirable substances.

[0055] For the purposes of this invention, "perfluoroalkyl and polyfluoroalkyl substances," also sometimes referred to as perfluorinated compounds, are understood to mean synthetic organofluorinated substances. According to the OECD / UNEP (Organisation for Economic Co-operation and Development / United Nations Environment Programme) definition, PFAS are molecules formed from a more or less long chain of carbon atoms, linear, branched, or cyclic, and containing at least one saturated and fully fluorinated fluorinated group, either methyl or methylene. Various functional groups may be added to this fluorocarbon skeleton, giving these molecules distinct physical, chemical, and toxicological properties.

[0056] PFAS are toxic to humans and the environment. They are highly persistent pollutants, which are widely present in water, air, soil, rain and ecosystems, as well as in human and animal organisms.

[0057] PFAS are distinguished according to their molecular mass.

[0058] Among the high molecular weight PFAS, that is to say with a molecular weight greater than 400 g / mol, the following PFAS may be mentioned: perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), perfluorooundecanoic acid (PFUnA or PFUnDA), perfluorononanesulfonic acid (PFNS), perfluorooctanesulfonate (PFOS or SPFO), perfluorooctanesulfonamide (PFOSA), perfluorodecanoic acid (PFDA), perfluoroheptanesulfonic acid (PFHpS) and perfluorooundecanesulfonic acid (PFUnDS).

[0059] Among the low molecular weight PFAS, that is to say with a molecular weight of less than 400 g / mol, the following PFAS may be mentioned: heptafluorobutyric acid (HFBA or PFBA); perfluoroheptanoic acid (PFHpA); perfluoropentanoic acid (PFPeA); undecafluorohexanoic acid (PFHxA), perfluoro-n-heptanoic acid (PFHpA), perfluorobutane sulfonic acid (PFBS) and perfluoropentane sulfonic acid (PFPeS).

[0060] For the purposes of this invention, "support" means an adsorbent material serving as a support for other elements or functional groups that can be grafted onto said support by covalent bonds.

[0061] The choice of adsorbent support may vary depending on the desired configuration and application requirements, with options ranging from electrospun membranes or nanofibers to ceramic membranes, textile adsorbents and different formats of activated carbon (granulated, extruded or powdered).

[0062] Granulated activated carbon (GAC) has established itself as a leading solution, but there is a continuing need for performance improvement so that GAC is even more effective at removing PFAS compounds from the environment and drinking water.

[0063] Ceramic membranes are also known to those skilled in the art as a support of choice for fixing functional elements and thus increasing the adsorption capacities of this adsorbent support.

[0064] A third support envisaged within the meaning of the invention consists of nonwoven nanofibers, that is to say, an assembly of nanofibers forming a surface and whose cohesion is ensured by physical and / or chemical methods, excluding weaving and knitting. Within this surface, the nanofibers can be oriented directionally (anisotropically) or randomly (isotropically); in the context of the present invention, they will preferably be oriented randomly. These nonwoven nanofibers are made of a polymeric material, composed of a single polymer or a mixture of several polymers.

[0065] These polymers are of synthetic or bio-based origin.

[0066] Among the synthetic polymers, we can mention polyacrylic acid (PAA) and polyvinyl alcohol (PVA).

[0067] Among bio-based polymers, chitosan is preferred.

[0068] Preferably, said nanofibers are made up of a mixture of several polymers.

[0069] Preferably, said nanofibers are made up of a mixture of polyacrylic acid, polyvinyl alcohol and chitosan.

[0070] Nonwoven nanofibers are an advantageous support because their random structure offers high porosity, increased specific surface area and distribution The homogeneous fiber structure allows for better interaction with pollutants or target molecules. This configuration also promotes increased filtration and adsorption performance, while reducing the constraints associated with the complex manufacturing of woven materials.

[0071] For the purposes of this invention, "impregnated support" or "loaded support" means an adsorbent support as defined above, onto which chemical elements have been fixed. In particular, these will be metallic nanoparticles.

[0072] By "metallic nanoparticles", for the purposes of the invention, we mean particles of nanometric size, that is to say having a diameter between 1 and 1000 nanometers, preferably between 1 and 100 nanometers, and more preferably between 1 and 10 nanometers, made up of one or more metallic oxides.

[0073] The metallic nanoparticles will be selected from zirconium dioxide (ZrO2), zinc oxide (ZnO), titanium dioxide (TiO2), aluminium oxide (Al2O3), iron oxide (Fe2O3, Fe3O4), cerium dioxide (CeO2), magnesium oxide (MgO) and manganese dioxide (MnO2) nanoparticles.

[0074] According to a preferred embodiment of the invention, the metal oxide nanoparticles are zirconium dioxide (ZrO2) nanoparticles.

[0075] This nanometric or micrometric metal oxide serves as an interface between the ligand and the adsorbent support, facilitating grafting onto the latter.

[0076] Zirconium dioxide (ZrO2) is used not only for its ability to form strong bonds with phosphonic acid groups, but also for its remarkable stability under extreme pH conditions and even under irradiation.

[0077] According to one embodiment of the invention, the ZrO2 nanoparticles are in the form of nanoparticles with an average size of 6 nm, dispersed in an aqueous suspension, preferably at 20% by weight. This concentration allows for a homogeneous distribution of the nanoparticles, ensuring their efficient integration within the adsorbent support.

[0078] By "functionalized nanoparticles" we mean, in the sense of the invention, nanoparticles on which functional chemical groups, also referred to as "ligands" because they have a binding affinity with ligand / receptor type PFAS, have been grafted by covalent bonding.

[0079] Said ligands are herein polyfluorinated and / or polyalkylated phosphonic ligands, also referred to in this application as "polyfluorinated and / or polyalkylated groups," that is to say, they contain at least one chemical group comprising at least two fluorine (F) atoms and / or at least one alkyl group, of general formula: CnH2n+l with n > 3. These ligands also contain a phosphonic acid function. The integration of a phosphonic acid function within The structure of the ligand ensures stable grafting to the surface of metal oxides. Phosphonic acid forms strong and stable bonds with zirconium dioxide (ZrO2).

[0080] In the present application, the terms "polyfluorinated and / or polyalkylated phosphonic ligands" and "polyfluorinated and / or polyalkylated ligands" are used interchangeably and refer to the same chemical groups.

[0081] Polyfluorinated ligands are notably selected from:

[0082] - phosphonic fluoroalkyl groups, in other words phosphonic acid fluorinated with general formula R-(CH2)nP(O)(OH)2, where R represents a polyfluorinated alkyl chain, and n is an integer corresponding to the number of CH2 groups (preferably between 0 and 10);

[0083] - phosphonic fluoroaryl groups, in other words phosphonic acid fluorinated with general formula R-(CH2)nP(O)(OH)2, where R represents a polyfluorinated aromatic substituent, and n is an integer corresponding to the number of CH2 groups (n >0).

[0084] Polyalkylated groups are in particular chosen from among phosphonic groups of general formula CnH2n+lP(O)(OH)2, where CnH2n+l corresponds to a linear or branched chain comprising at least 6 carbon atoms, such as the hexyl group (CeHis), the dodecyl group (C12H25), or other long-chain alkyls, used for their hydrophobicity and their ability to form organized structures on surfaces.

[0085] According to one embodiment of the invention, the nanoparticles are functionalized by covalent bonding with phosphonic polyalkyl groups, phosphonic fluoroaryls or phosphonic fluoroalkyls.

[0086] Preferably, the ligands of the adsorbent material of the invention are phosphonic polyfluorinated ligands, and more particularly are phosphonic fluoroalkyl groups.

[0087] Polyfluorinated ligands are in particular selected from phosphonic fluoroalkyl acid (CIO) and pentafluorobenzylphosphonic acid.

[0088] According to a preferred embodiment, the fluoroalkyl phosphonic groups are derived from fluoroalkyl phosphonic acid.

[0089] Preferably, the phosphonic polyfluorinated ligands are derived from phosphonic fluoroalkyl acid (CIO) of CAS number 252237-39-1, which is commercially available, and in particular distributed by the company SPECIFIC POLYMERS.

[0090] The adsorbent material is thus a composite material, consisting of at least three components: a support, metal oxide nanoparticles and polyfluorinated and / or polyalkylated ligands / phosphonic groups.

[0091] According to a preferred embodiment, the adsorbent material comprises, or consists of, activated carbon as a support, zirconium dioxide nanoparticles and, as polyfluorinated ligands, ligands derived from phosphonic fluoroalkyl acid (CIO).

[0092] According to another embodiment, the adsorbent material comprises, or consists of, non-woven nanofibers made of a mixture of polymers as a support, zirconium dioxide nanoparticles and, as polyfluorinated ligands, ligands derived from phosphonic fluoroalkyl acid (CIO).

[0093] Ligands are chemical entities of low weight compared to the total weight of the composite material (support + nanoparticles + ligands); the structural characterization of the adsorbent material presented below is therefore based on two relative quantities: that of the support and that of the functionalized metal oxide nanoparticles.

[0094] According to a preferred embodiment of the invention, the adsorbent material comprises between 90% and 99% by weight of adsorbent support made of activated carbon and between 1% and 10% by weight of functionalized metal oxide nanoparticles, relative to the total weight of the adsorbent material.

[0095] According to another preferred embodiment of the invention, the adsorbent material comprises between 60% and 99% by weight of adsorbent support made of non-woven nanofibers, and between 1% and 40% by weight of functionalized metal oxide nanoparticles, relative to the total weight of the adsorbent material.

[0096] Preferably, the adsorbent material of the invention is characterized in that the metal oxide nanoparticles represent between 1% and 5% by weight relative to the total weight of the adsorbent material, and more preferably represent 2% by weight relative to the total weight of the adsorbent material. Processes for preparing the adsorbent material

[0097] The fixation conditions and the concentration of zirconium dioxide (ZrO2) in the activated carbon have been carefully optimized to ensure homogeneous and stable integration of the nanoparticles within the activated carbon matrix.

[0098] This optimization relies on precise adjustments of several critical parameters, including pH, reaction time, and the mass / volume ratios of the metal oxide relative to the support. These parameters were adjusted to prevent any release of ZrO2 nanoparticles during their use, thus ensuring consistent and reliable performance of the adsorbent material while preserving the integrity of the activated carbon's active surface.

[0099] According to a first embodiment, the process for preparing an adsorbent material according to the invention comprises the following steps:

[0100] a) immersion of the support in a suspension comprising metal oxide nanoparticles in a solvent, preferably ethanol, to obtain a "charged support";

[0101] b) drying of the loaded support in two sub-steps, first at a temperature between 100°C and 120°C, then at a temperature between 200°C and 240°C;

[0102] c) immersion of the loaded and dried support in a suspension containing polyfluorinated and / or polyalkylated phosphonic ligands;

[0103] d) drying of the "functionalized" support obtained in step (c), preferably at a temperature between 50 and 110°C;

[0104] e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

[0105] Preferably, step (b) of drying the loaded support lasts between 6 and 15 hours, preferably between 8 and 12 hours.

[0106] Preferably, step (d) of drying the functionalized support lasts between 4 and 12 hours, preferably between 6 and 10 hours.

[0107] According to a second embodiment, the process for preparing an adsorbent material according to the invention comprises the following steps:

[0108] a) preparation of a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated phosphonic ligands in a solvent;

[0109] b) optionally, vacuum drying at 40°C under rotation;

[0110] c) immersion of a support in a suspension containing metal oxide nanoparticles functionalized with polyfluorinated and / or polyalkylated ligands, then continuous homogenization by rotation;

[0111] d) drying of the support obtained in step (c), preferably at a temperature between 50 and 110°C;

[0112] e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

[0113] The solvent used in step (a) shall be chosen by the person skilled in the art according to the solubility of the ligand(s). In particular, it may be chosen from ethanol, water, or a mixture of the two.

[0114] The optional step (b) optimizes and accelerates the binding of the ligand(s) to the metal oxide nanoparticles. Indeed, the polyfluorinated and / or polyalkylated ligands used inherently exhibit a high affinity for metal oxides, particularly ZrO2. The functionalization of the metal oxides can therefore be carried out at room temperature. However, to ensure more homogeneous binding of the ligands, step (b) accelerates and homogenizes the binding of the ligand(s) to the metal oxide nanoparticles.

[0115] Step (b) consists of heating the mixture from step (a) to evaporate the solvent. This drying / heating step preferably lasts between 1 and 6 hours, and more preferably between 2 and 4 hours.

[0116] The functionalized metallic nanoparticles obtained at the end of steps (a) or (b) are then resuspended before step (c).

[0117] Steps (d) and (e) are identical to those presented previously.

[0118] In the case where the support is made of non-woven polymer nanofibers, a specific process for preparing the adsorbent material according to the invention is implemented.

[0119] Said method for preparing an adsorbent material according to the invention from a non-woven nanofiber support comprises the following steps:

[0120] a) preparation of a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated phosphonic ligands in a solvent;

[0121] b) optionally, vacuum drying at 40°C under rotation;

[0122] c) homogenization of the polymer in solution using a mixer, and addition of metal oxide nanoparticles functionalized by said polyfluorinated and / or polyalkylated ligands;

[0123] d) electrospinning of the polymer loaded with functionalized nanoparticles obtained in step (c) to obtain nanofibers;

[0124] e) drying the nanofibers obtained in step (d), preferably at a temperature between 120 and 170°C, to obtain the crosslinking of the polymer;

[0125] f) washing the adsorbent material obtained with a suitable solvent, in particular deionized water.

[0126] The solvent used in step (a) shall be chosen by the person skilled in the art according to the solubility of the ligand(s). In particular, it may be chosen from ethanol, water, or a mixture of the two.

[0127] The optional step (b) optimizes and accelerates the binding of the ligand(s) to the metal oxide nanoparticles. Indeed, the polyfluorinated and / or polyalkylated phosphonic ligands used inherently exhibit a high affinity for metal oxides, particularly ZrO2. The functionalization of the metal oxides can therefore be carried out at room temperature. However, to ensure more homogeneous binding of the ligands, step (b) accelerates and homogenizes the binding of the ligand(s) to the metal oxide nanoparticles.

[0128] Step (b) consists of heating the suspension from step (a) to evaporate the solvent. This drying / heating step preferably lasts between 1 and 6 hours, and more preferably between 2 and 4 hours.

[0129] The functionalized metallic nanoparticles obtained at the end of steps (a) or (b) are then added in step (c) to the polymer, in the form of dried powder or after resuspension.

[0130] Step (d) of electrospinning the polymer is carried out under the classic conditions, well known to the person skilled in the art, to obtain nanofibers.

[0131] The polymer crosslinking is then obtained by drying in step (e), for a period of between 10 and 30 minutes.

[0132] Preferably, and as shown in the examples, the processes described above are carried out using a specific molar ratio (ligands: metal oxide).

[0133] Thus, according to a preferred embodiment of the invention, the process for preparing the adsorbent material is characterized in that the molar ratio ligands: metal oxide used is between 1:20 and 1:80, said molar ratio being preferably 1:50.

[0134] Process for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS)

[0135] The present invention also relates to a method for capturing per- and poly-fluoroalkyl substances (PFAS) comprising bringing a liquid or gas capable of containing PFAS into contact with the adsorbent material according to the invention, or as obtained by one of the methods according to the invention.

[0136] By capture or adsorption, we mean in the sense of the invention the attachment of PFAS to the material according to the invention, by physico-chemical interactions of the type of non-covalent bonds; said non-covalent bonds being nevertheless sufficiently strong to resist the flow of the liquid or gas.

[0137] The capture rate (or adsorption capacity) is evaluated by means of "breakthrough rate or percentage" measurements. For these measurements, a bed of adsorbent material is pressurized and purged with a gas or liquid. Once the system is in equilibrium, substances to be adsorbed (called "adsorbates") are added to the inlet liquid or gas. The change in the concentration of these substances in the effluent at the outlet of the fixed-bed adsorber is monitored as a function of the effluent volume.

[0138] A satisfactory capture rate is considered to correspond to a breakthrough percentage at the system outlet of less than 10%.

[0139] According to one embodiment of the process of the invention, the PFAS captured by the material of the invention are of low molecular weight, high molecular weight, or a mixture of both.

[0140] For the purposes of the invention, "high molecular weight PFAS" means PFAS with a molecular weight greater than 400 g / mol, for example the following PFAS: PFOA, PFNA, PFHxS, PFUnDA and PFNS.

[0141] For the purposes of this invention, "low molecular weight PFAS" means PFAS with a molecular weight of less than 400 g / mol. Examples of PFAS belonging to this category include: PFBA, PFPeA, PFHxA, PFHpA, PFBS, and PFPeS.

[0142] Advantageously, the process of the invention is adapted to capture low molecular weight PFAS.

[0143] Finally, the present application relates to the use of the adsorbent material as defined above, or as obtained by one of the processes defined above, to capture per- and poly-fluoroalkyl substances (PFAS) present in a liquid or a gas.

[0144] Among the liquids likely to contain PFAS, particular mention should be made of water polluted and / or contaminated by PFAS, including polluted and / or contaminated groundwater and surface water located near industrial sites, landfills, or fire training areas where fluorinated firefighting foams have been used. Water intended for human consumption (so-called drinking water) may also contain PFAS, particularly if it comes from contaminated sources or if the treatment processes used do not allow for their effective removal. In addition, domestic or industrial wastewater represents a major source of contamination, particularly wastewater from manufacturing activities such as the production of waterproof textiles, non-stick coatings, or fluorinated foams.Leachate from landfills and industrial effluents containing PFAS, generated during processes such as electroplating or semiconductor manufacturing, also constitute contaminated liquids. Finally, some commercial or household liquids, such as cleaning products, waterproofing sprays, and specialized chemical solutions, may contain PFAS, thus increasing their dispersion in the aquatic environment.

[0145] Among the gases likely to contain PFAS, industrial emissions, particularly those from the manufacturing processes of fluorinated materials such as non-stick coatings, waterproof textiles, and fire-fighting foams, are of primary importance. Gases emitted by the incomplete incineration of waste containing PFAS, such as food packaging or used chemicals, can also release these compounds as vapors or volatile particles. Emissions from wastewater treatment plants, especially vapors from contaminated sludge, represent another significant source of air pollution. Furthermore, certain fluorinated gases used as refrigerants, solvents, or propellants may contain PFAS or Their precursors. Aerosols containing fluorinated substances, such as stain-resistant or water-repellent sprays, also contribute to the dispersion of PFAS in the air. Finally, accidental emissions, for example during the storage or transport of fluorinated chemicals, as well as gases produced by the thermal degradation of fluorinated materials, are potential sources to monitor in order to limit the spread of these persistent contaminants in the atmosphere. EXAMPLES

[0146] The effectiveness of the adsorbent materials according to the invention is demonstrated in the examples below. A significant increase in the adsorption capacity of PFAS is observed after the functionalization of the adsorbent support, via the attachment of functionalized metal oxide nanoparticles.

[0147] In these examples, the chosen support is granular activated carbon with a specific surface area of ​​approximately 1100 m² / g, obtained from the manufacturer BIJIN. The metal oxide nanoparticles consist of zirconium dioxide (ZrO2).

[0148] Example 1. Fixation of zirconium dioxide onto activated carbon

[0149] The fixation conditions and the concentration of zirconium dioxide (ZrO2) in the activated carbon have been carefully optimized to ensure homogeneous and stable integration of the nanoparticles within the activated carbon matrix.

[0150] This optimization relies on precise adjustments of several critical parameters, including pH, reaction time, and the mass / volume ratios of the metal oxide relative to the support. These parameters were adjusted to prevent any release of ZrO2 nanoparticles during their use, thus ensuring consistent and reliable performance of the adsorbent material while preserving the integrity of the activated carbon's active surface.

[0151] The quantification of the ZrO2 content was carried out by thermogravimetric analysis (TGA), allowing the proportion of incorporated ZrO2 to be measured.

[0152] The results presented in [Fig. 1] reveal a residual content of 2.6% by weight, very close to the theoretical target value of 2%. This proximity between the measured and theoretical values ​​confirms an effective and controlled fixation of zirconium dioxide in activated carbon, thus demonstrating the reliability of the optimized fixation conditions.

[0153] Furthermore, the textural analysis of the modified activated carbon ([Fig.2]) indicates a slight reduction in specific surface area after incorporation of ZrO2. This decrease demonstrates the successful fixation of the nanoparticles in the matrix, without compromising the overall adsorption capacity of the activated carbon at a content of 2 wt%. Indeed, despite this slight decrease in active surface area, the material retains a substantial number of adsorption sites available for processing applications. water, thus ensuring that modified ZrO2 continues to meet performance requirements for PFAS decontamination.

[0154] When the ZrO2 content is maintained at 2 wt%, nanoparticle fixation is optimally achieved under moderately acidic pH conditions, around 6, and at room temperature. These conditions promote a stable interaction between the ZrO2 nanoparticles and the activated carbon surface, contributing to a homogeneous and stable particle distribution within the matrix and ensuring increased efficiency in water treatment applications.

[0155] Example 2. Process for functionalizing metal oxide nanoparticles

[0156] The functionalization was carried out while maintaining a ligand / ZrO2 molar ratio of 1 / 50, optimized to maximize surface coverage without excessive saturation.

[0157] The functionalization process began with step (a): dissolving the ligand in absolute ethanol, followed by the gradual, drop-by-drop addition of this solution to the aqueous suspension of ZrO2. This controlled process ensures homogeneous dispersion of the ligand around the suspended nanoparticles. Once the addition was complete, the mixture was subjected to constant stirring for 6 hours, ensuring complete interaction between the ligand and the surface of the ZrO2 nanoparticles.

[0158] In the next step (b), the ethanol was removed by vacuum evaporation at 40°C using a rotary evaporator, which made it possible to obtain a dry powder of functionalized nanoparticles, ready for incorporation into adsorbent supports.

[0159] It is important to note that this functionalization was initially carried out on ZrO2 nanoparticles in suspension. However, this process can also be applied to ZrO2 nanoparticles after their incorporation into the adsorbent support. Example 3. PFOA Adsorption Test

[0160] To evaluate the adsorption performance of functionalized zirconium dioxide (functionalized ZrO2) compared to that of virgin activated carbon, two adsorption experiments were carried out using the same perfluorooctanoic acid (PFOA) solution at a concentration of 54 mgL-1 (ppm).

[0161] For each test, the concentration of the adsorbent was fixed at 1 gL-1, whether for functionalized ZrO2 or virgin activated carbon, in order to maintain comparable experimental conditions.

[0162] The mixtures were agitated for 4 hours, allowing sufficient contact time for the establishment of adsorption equilibrium between the adsorbent and the suspended PFOA. Subsequently, each mixture was subjected to centrifugation to efficiently separate the adsorbent from the liquid phase. The resulting supernatant has was carefully collected and analyzed to determine the residual concentration of PFOA.

[0163] Analyses of the PFOA solution before and after adsorption were carried out by gas chromatography coupled to tandem mass spectrometry (GC-MS-MS), a highly sensitive and specific detection method, allowing precise measurement of the reduction in PFOA concentration in each case.

[0164] The results, presented in [Fig. 3], show a higher adsorption efficiency for functionalized ZrO2 compared with virgin activated carbon. The adsorption efficiency of non-functionalized ZrO2 nanoparticles is zero and is therefore not shown in [Fig. 3].

[0165] These results suggest that functionalizing ZrO2 significantly improves its affinity for PFOA, probably due to specific interactions between the fluorinated groups of the ligand and the perfluorinated chains of PFOA. This observation supports the potential of functionalized ZrO2 as an advanced adsorbent material for treating perfluorinated contaminants in water. Example 4. Study of adsorption isotherms

[0166] The study of adsorption isotherms is crucial for understanding the performance of an adsorbent material in contaminant treatment. Isotherms allow us to analyze the relationship between the amount of solute adsorbed by the adsorbent and the concentration of the solute remaining in solution at a constant temperature. These experimental curves provide essential information on the adsorption capacity, interaction mechanisms, and surface characteristics of the adsorbent.

[0167] Among the isotherms frequently used in adsorption chemistry, the Langmuir isotherm is one of the most common, particularly because of its relevance to homogeneous adsorbent surfaces.

[0168] The Langmuir isotherm is based on several simplifying assumptions. It assumes that adsorption is a unimolecular process, that is, that each solute molecule is adsorbed onto a single active site. This model also considers that: • The surface of the adsorbent is homogeneous, with energetically equivalent adsorption sites. • Once a site is occupied by a molecule, no other adsorbate can attach to it. • Adsorption and desorption are in dynamic equilibrium.

[0169] The equation of the Langmuir isotherm is written as follows: ■ A;; - <7

[0170] where: • qe is the quantity of adsorbate adsorbed per unit of adsorbent mass at equilibrium (mg / g), • Qmax represents the maximum adsorption capacity (mg / g), • KL is the Langmuir constant (L / mg), which reflects the affinity of the adsorbent for the adsorbate, • This is the concentration of the adsorbate in solution at equilibrium (mg / L).

[0171] The Langmuir isotherm allows for a precise measurement of the adsorption capacity of a material for a given solute.

[0172] By fixing the concentration of the solute, it is possible to determine the maximum amount that the adsorbent can adsorb before saturation, thus providing critical information for industrial applications where adsorption performance is essential. The Langmuir model is particularly useful for homogeneous adsorbents and applications where monolayer is possible.

[0173] The Langmuir isotherm is a fundamental tool for characterizing the performance of adsorbents, particularly for materials with a homogeneous surface where unimolecular adsorption is observed. By providing detailed information on the adsorption capacity and affinity of the material for the solute, the Langmuir isotherm helps to optimize the selection and conditions of use of adsorbents, thus contributing to the efficiency of treatment processes in various fields such as water and industrial effluent treatment.

[0174] Batch adsorption tests were conducted to evaluate the capture performance of PFOA by functionalized zirconium dioxide (ZrO2), under standardized test conditions to ensure reproducibility of results.

[0175] The experiments were carried out at a stirring speed of 300 revolutions per minute (rpm) for 30 minutes, ensuring homogeneous contact between the adsorbent and the PFOA solution.

[0176] The concentration of the adsorbent was fixed at 1 gL-1, while the initial concentrations of PFOA were 54, 140, and 300 mgL-1, simulating different pollution conditions to evaluate the adsorption efficiency as a function of concentration: see [Fig.4](l).

[0177] The results obtained made it possible to model the adsorption according to the Langmuir model, showing that the adsorption initially takes place in a homogeneous manner, with a strong affinity between the functionalized ZrO2 and the PFOA molecules, until the formation of a complete monolayer corresponding to a 100% coverage.

[0178] Beyond this saturation of the monolayer, a multilayer adsorption begins to form, allowing the material to continue adsorbing molecules of PFOA, although effectiveness gradually decreases due to congestion of active sites.

[0179] As illustrated in [Fig.4](l), experimental data show an adsorption efficiency of PFOA of more than 95% for an initial concentration less than or equal to 54 mg L-1, which underlines the high affinity of functionalized ZrO2 for PFOA under low contamination conditions.

[0180] Figure 4(2) illustrates the evolution of the recovery rate (%) as a function of the initial concentration (Co) of PFOA, expressed in ppm (mg.L⁻¹). The results reveal a progressive and marked increase in the recovery rate with increasing initial concentration, suggesting a positive correlation between Co and the efficiency of the adsorption process. At an initial concentration of 54 ppm, the recovery rate is relatively low, reaching only 40%. Despite this moderate value, the result indirectly indicates a high adsorption capacity, suggesting that only a fraction of the available surface area is initially used. At Co = 140 ppm, the recovery rate rises to 89%, reflecting near-saturation of the adsorbent surface, probably due to the almost complete occupation of the available adsorption sites. Finally, at Co = 300 ppm, the recovery rate reaches 147%, thus exceeding 100%.This result indicates the formation of a multilayer of adsorbates, confirming that, following the saturation of the sites in the first monolayer, interactions between adsorbed molecules promote the deposition of additional layers. This trend highlights amplified adsorption phenomena, potentially associated with intermolecular interactions.

[0181] Figure 5 illustrates the adsorption isotherm of PFOA on functionalized ZrO2, compared to the theoretical Langmuir model. The x-axis (Ce in mmol.L⁻¹) represents the equilibrium concentration of the compound in solution, while the y-axis (Qe in mmol.g⁻¹) indicates the amount adsorbed per unit mass of the adsorbent. Experimental data (represented by the gray curve) show a rapid increase in Qe at low concentrations of Ce, suggesting a strong initial affinity between the adsorbent and the adsorbate. However, at high concentrations, the curve tends to stabilize, indicating a progressive saturation of the available adsorption sites on ZrO2.

[0182] In comparison, the Langmuir model (black dotted curve) reproduces the experimental data well at low concentrations, but diverges at high Ce values. This divergence could reflect the presence of additional adsorption mechanisms, such as multilayer adsorption or intermolecular interactions not taken into account in the Langmuir model, which assumes monolayer adsorption on a homogeneous surface.

[0183] The maximum adsorption capacity, reaching 129 mg of PFOA per gram of functionalized ZrO2, confirms the high performance of this material, with monolayer saturation at this maximum capacity.

[0184] Based on these results, it is estimated that one gram of functionalized zirconium dioxide can retain approximately 2 x 10²⁰ molecules of PFOA. This is significantly higher than the estimated retention of one gram of activated carbon, which can retain approximately 6 x 10¹⁸ molecules of PFOA.

[0185] These observations show the robustness of the adsorption capacity of functionalized ZrO2, not only in conditions of low to medium contamination, but also in highly contaminated environments where the formation of multilayers becomes possible.

[0186] Example 5. Selectivity of PFAS adsorption by the material according to the invention

[0187] Figure 6 illustrates the adsorption selectivity of virgin activated carbon towards 14 different PFAS. It is clear that only PFAS with long chains (11 carbons) have a breakthrough rate of less than 10% after washing the adsorbent material.

[0188] To evaluate the selectivity of zirconium dioxide (ZrO2) after its functionalization, a comparative study was carried out with virgin activated carbon as a control.

[0189] A mixture of PFAS was prepared containing: - Perfluoropentanoic acid (PFPa) as a model of low molecular weight (5 carbons) PFAS, - perfluorooctanoic acid (PFOA) as a model high molecular weight molecule (8 carbons), and - bisphenol A as a model of an organic pollutant.

[0190] The initial concentrations of these compounds in the mixture were respectively 1600 ppb for PFPeA, 1020 ppb for PFOA, and 540 ppb for bisphenol A.

[0191] For each experiment, the concentration of the adsorbent was standardized to 1 gL-1, both for functionalized ZrO2 and for virgin activated carbon, thus ensuring comparable experimental conditions.

[0192] The mixtures were stirred for 4 hours, providing sufficient contact time for the establishment of adsorption equilibrium. Following this phase, each mixture was subjected to centrifugation to efficiently separate the adsorbent from the liquid phase. The supernatant was carefully collected and analyzed to determine the residual concentrations of the adsorbed compounds.

[0193] The analyses were carried out using gas chromatography coupled with tandem mass spectrometry (GC-MS-MS), a detection method renowned for its high sensitivity and specificity, allowing for the precise measurement of the reduction in the concentration of the different pollutants after adsorption.

[0194] The results, presented in [Fig.7], indicate a significantly higher adsorption efficiency for functionalized ZrO2 compared to virgin activated carbon, regardless of the PFAS.

[0195] Advantageously, low molecular weight PFPeA is adsorbed much better by functionalized ZrO2 than by activated carbon.

[0196] LIST OF BIBLIOGRAPHICAL REFERENCES

[0197] Stebel, EK, Pike, KA, Nguyen, H., Hartmann, HA, Klonowski, MJ, Lawrence, MG,... & Edmiston, PL (2019). Absorption of short-chain to long-chain perfluoroalkyl substances using swellable organically modified silica. Environmental Science: Water Research & Technology, 5(11), 1854-1866.

[0198] Gagliano, E., Sgroi, M., Falciglia, PP, Vagliasindi, FG, & Roccaro, P. (2020). Removal of poly-and perfluoroalkyl substances (PFAS) from water by adsorption: Role of PFAS chain length, effect of organic matter and challenges in adsorbent regeneration. Water research, 171, 115381.

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[0201] WO 2020 / 206317 WO 2022 / 109392 WO 2023 / 107629

Claims

Demands

1. Adsorbent material comprising a support made of activated carbon or non-woven nanofibers, said support being impregnated with metal oxide nanoparticles, and said nanoparticles being functionalized by covalent bonding with polyfluorinated and / or polyalkylated phosphonic ligands.

2. Adsorbent material according to claim 1, characterized in that the metal oxide nanoparticles are zirconium dioxide (ZrO2) nanoparticles.

3. Adsorbent material according to any one of claims 1 or 2, characterized in that the nanoparticles are functionalized by covalent bonding with phosphonic polyalkyl, phosphonic fluoroalkyl or phosphonic fluoroaryl groups.

4. Adsorbent material according to claim 3, characterized in that the fluoroalkyl phosphonic groups are derived from fluoroalkyl phosphonic acid.

5. Adsorbent material according to any one of claims 1 to 4, characterized in that the metal oxide nanoparticles represent between 1% and 5% by weight relative to the total weight of the adsorbent material, and preferably represent 2% by weight relative to the total weight of the adsorbent material.

6. A process for preparing an adsorbent material according to any one of claims 1 to 5, comprising the following steps: a) immersing the support in a suspension comprising metal oxide nanoparticles in a solvent, preferably ethanol, to obtain a charged support; b) drying the charged support in two sub-steps, first at a temperature between 100°C and 120°C, then at a temperature between 200°C and 240°C; c) immersing the charged and dried support in a suspension containing polyfluorinated and / or polyalkylated phosphonic ligands; d) drying the functionalized support obtained in step (c), preferably at a temperature between 50 and 110°C; e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

7. A method for preparing an adsorbent material according to any one of claims 1 to 5 comprising the following steps: a) preparing a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated phosphonic ligands in a solvent; b) optionally, drying under vacuum at 40°C under rotation for evaporation of said solvent; c) immersing a support in a suspension containing the metal oxide nanoparticles functionalized with said ligands, then continuous homogenization by rotation; d) drying the loaded support obtained in step (c), preferably at a temperature between 50 and 110°C; e) washing the adsorbent material obtained with a suitable solvent, in particular with deionized water.

8. A method for preparing an adsorbent material according to any one of claims 1 to 5, characterized in that the support consists of non-woven polymer nanofibers, comprising the following steps: a) preparation of a suspension comprising metal oxide nanoparticles and polyfluorinated and / or polyalkylated phosphonic ligands in a solvent; b) optionally, vacuum drying at 40°C under rotation for evaporation of said solvent; c) homogenization of the polymer in solution using a mixer, and addition of the metal oxide nanoparticles functionalized with polyfluorinated and / or polyalkylated ligands; d) electrospinning of the polymer loaded with the functionalized nanoparticles obtained in step (c) to obtain nanofibers; e) drying of the nanofibers obtained in step (d), preferably at a temperature between 120 and 170°C;f) washing the resulting adsorbent material with a suitable solvent, in particular deionized water.;

9. A preparation method according to any one of claims 6 to 8, characterized in that the molar ratio ligands: metal oxide used is between 1:20 and 1:80, said molar ratio preferably being 1:

50.

10. A method for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS) comprising bringing a liquid or gas capable of containing PFAS into contact with the adsorbent material according to any one of claims 1 to 5, or as obtained by the method according to any one of claims 6 to 9.

11. A method for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS) according to claim 10, characterized in that the PFAS are of low or high molecular weight, and are in particular selected from perfluorooctanoic acid (PFOA) and perfluoropentanoic acid (PFPEA).

12. Use of the adsorbent material according to any one of claims 1 to 5, or as obtained by the process according to any one of claims 6 to 9, for capturing perfluoroalkyl and polyfluoroalkyl substances (PFAS) present in a liquid or gas.

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