Methodology for the treatment of soils / groundwaters / surface waters and other materials contaminated with perfluoroalkyl and polyfluoroalkyl substances [PFAS]

Abstract

The invention provides a methodology for treating perfluoroalkyl and polyfluoroalkyl substances, collectively referred to as PFAS, in soils, groundwater, surface water and within other materials. PFAS exhibit a broad range of chemical properties which necessitates the application of a versatile treatment technology. The invention utilises a modified inorgano-organoclay or modified inorgano-organoclays for the treatment of PFAS which provide(s) this essential capability and flexibility. The composition of the modified inorgano-organoclay / modified inorgano-organoclays can be varied accordingly enabling the clays to exhibit varying degrees of hydrophobicity / hydrophilicity. PFAS are sorbed into the modified inorganoclay / modified inorgano- organoclays and chemically immobilised. The clays can be used in combination with cementitious materials to provide an advanced stabilisation process for the treatment of PFAS contamination in soils / other materials or used in isolation for groundwater / surface water treatment. The objective is to reduce the environmental impact of PFAS pollutants.

Description

[0001] METHODOLOGY FOR THE TREATMENT OF SOILS / GROUNDWATERS / SURFACE WATERS AND OTHER MATERIALS CONTAMINATED WITH PERFLUOROALKYL AND POLYFLUOROALKYL SUBSTANCES [PFAS]

[0002] Background and Prior Art

[0003] This invention describes a process for treating soils, groundwaters / surface waters and other materials contaminated with perfluoroalkyl and polyfluoroalkyl substances. The methodology involves the sorption and immobilisation of perfluoroalkyl and polyfluoroalkyl substances within a modified inorgano-organoclay.

[0004] Perfluoroalkyl and polyfluoroalykyl substances, collectively referred to as PFAS, are a large group of chemicals commonly referred to as ‘forever chemicals’ due to their persistence within the environment and their resistance to natural degradation. This is primarily due to the extremely strong carbon - fluorine bonding within the PFAS structure. PFAS are divided into two primary classes, namely non-polymers and polymers. The non-polymer forms are most commonly detected in the environment and include perfluoroalkyl acids [PFAAs], perfluoroalkyl carboxyllic acids / carboxylates [PFCAs], perfluoroalkane sulfonic acids / sulfonates [PFSAs], perfluoroalkane sulfonamides [FASAs], perfluoroalkane sulfonamido substances, fluorotelomers and polyfluoro ether carboxylic acids.

[0005] PFCAs and PFSAs are the most commonly identified PFAS in contaminated soils, groundwaters / surface waters and other materials. An example of a commonly identified PFCA is perfluorooctanoic acid [PFOA] and an example of a commonly identified PFSA is perfluorooctane sulfonate [PFOS]. PFOA has the chemical formula C8HF15O2; PFOS has the chemical formula CsHFvOsS.

[0006] Both PFOA and PFOS have been used extensively as surfactants. The molecules exhibit both hydrophobic / lipophobic and hydrophilic properties enabling their effective use as surfactants and in the manufacture of inter alia textiles, carpets, fire-fighting foams, fire resistant materials, stain repellants and sealants. The hydrophobic / lipophilic properties are provided by the carbon chain; the hydrophilic properties are provided by the functional head (carboxylate for PFOA and sulfonate for PFOS).

[0007] PFAS are typically classified as long chain and short chain respectively. Long chain PFCAs have typically eight carbon atoms in the chain or more; short chain PFCAs have typically seven carbon atoms in the chain or less. Long chain PFSAs have typically six carbon atoms in the chain or more; short chain PFSAs have typically five carbon atoms in the chain or less. PFOA and PFOS are classified as long chain PFAS (both have eight carbon atoms in the chain). PFAAs and PFSAs are highly water soluble and exist as the dissociated anionic forms in the environment. PFOA has a water solubility of 9.5g / l; PFOS has a water solubility of 570mg / l. The sorptive properties of these chemicals onto soil particles has been researched and it has been concluded that there are multiple factors that need to be considered. These include the effects of carbon chain length / molecular weight and related hydrophobicity, molecular structure, effect of pH and the effect of the soil particles themselves.

[0008] Longer chain PFAS are typically more hydrophobic; shorter chain PFAS substances tend to exhibit greater hydrophilic properties (less hydrophobic). The sorption coefficients (Kd) of long chain PFAS tend to increase linearly with increasing molecular weight reflecting the longer perfluoroalkyl chain and also through likely increased physical adherence of PFAS to soil surfaces (multiple contact points). There does not appear to be any significant relationship between Kd and molecular weight for short chain PFAS. The properties of the differing PFAS also vary with molecular structure - PFAS can exist in different isotopic forms (linear or branched) and some PFAS are zwitterions with both positive and negative charges (electroneutral).

[0009] The Kd values of PFCAs and PFSAs decrease with increasing pH. This is primarily due to electrostatic repulsion between the dissociated anionic forms and soil particles, which become more negatively charged as pH increases. This effect can be significant, particularly for PFAS with high pKa values. It is a very important consideration when treating PFAS contaminated soils and other materials with stabilisation media containing cementitious materials. There is an increase in pH using cementitious materials as a consequence of the cement hydration process (increasing alkalinity).

[0010] Soil properties will vary in terms of electrical charge which will determine the Kdvalues on a sitespecific basis - this relates to the cation exchange capacities of clay minerals in the soil and the presence of cations such as aluminium which will increase Kdvalues.

[0011] It is the wide-ranging properties of PFAS and other factors such as soil properties that presents the greatest challenge for an effective treatment solution. The methodology described in this disclosure utilises a modified inorgano-organoclay with the required versatility to effectively treat both short-chain and long-chain PFAS with wide ranging properties.

[0012] Conventional treatment technologies for PFAS contaminated soils (or for certain PFCAs or PFSAs contaminated soils) are very limited due to the extremely recalcitrant properties of PFAS. Treatment technologies are under development which could theoretically be applied to the treatment of PFAS contaminated soils however these have limited commercial and practical applicability and have a strong dependence on high energy consumption. These include destructive technologies such as plasma treatment and photolysis I photochemical oxidation. There is a need, therefore, for improved methods of treating PFAS which can be commercially I practically applied and can also effectively treat a broad range of PFAS with widely varying chemical properties.

[0013] The application of conventional organoclay technology for the treatment of PFAS contaminated soils is an established technology which can be applied cost effectively and in a practical manner. The use of stabilisation processes including organoclays or waste materials such as alum sludge (providing a source of reactive aluminium) is also an established technology for the treatment of soils contaminated with PFAS.

[0014] US 8,940,958 B2 describes a method for the stabilisation and immobilisation of contaminants utilising an alum sludge composition (typically waste alum sludges from water treatment facilities), comprising one or more aluminium compound(s) and / or complex(es) together with a reactive carbon material (for example, activated carbon which is commonly found in waste alum sludges). The treatment of PFAS using this method is referenced within the disclosure. The aluminium compound is referred to as amorphous aluminium hydroxide in Claim 8 of the US 8,940,958 B2 invention.

[0015] It is claimed within the patent that the aluminium compound(s) and / or complex(es) enable the stabilisation of inorganic contaminants whilst the reactive carbon material enables the stabilisation of organic compounds. It is a further embodiment of this invention that a solidifier is used to generate a solid mass of treated material, the solidifier being selected from binding materials used in the building and construction materials (for example a pozzolanic or cementitious material).

[0016] Conventional organoclay technology is however limited to the removal of more hydrophobic forms of PFAS / longer chain forms. This is clearly related to the hydrophobicity of a conventional organoclay which has a greater affinity for the more hydrophobic forms of PFAS and a lesser affinity for the more hydrophilic shorter chain forms in particular. It is feasible to adapt a conventional organoclay to vary the hydrophobic / hydrophilic properties enabling the sorption of shorter chain PFAS in addition to longer chain PFAS.

[0017] US 11 ,000,822 B2 describes a method of sorbing PFAS using an organoclay and in particular, sorbing PFAS using an organoclay produced by intercalation of one or more di-functional quaternary amine compounds and one or more mono-quaternary ammonium compounds, wherein the di-quaternary ammonium compound is present in % mole concentrations ranging from 25% - 95%. It is a further embodiment of the invention that the organoclay sorbent may comprise of two organoclays, one produced by the intercalation of one or more mono-quaternary ammonium compounds and the other produced by the intercalation of one or more di-quaternary ammonium compounds, the latter being present within the sorbent in % mole concentrations ranging from 25% - 95%. It is claimed that the combination of both types of quaternary ammonium compounds improves the sorption of both the long chain and short chain forms of PFAS by the introduction of an electrostatic force between the clay platelets enabling better access to the interior of the organoclay sorbent. Furthermore, it is claimed that the presence of di-quatemary amine compound improves the sorption of short chain / shorter chain PFAS due to the more hydrophilic properties imparted into the clay structure by intercalation of the di-quaternary amine. Example 3, Table 1 in US 11 ,000.822 B2 documents the results obtained with varying mono and diquaternary compositions and with varying degrees of intercalation. As an example, it is stated that a 50 / 50 mix of both quaternary amines with 100% intercalation based on the cation exchange capacity of the organoclay resulted in 94.3% long chain removal, 98.7% USA regulated PFAS removal (i.e. PFNA, PFOA, PFOS, PHxS, and PHpA) and 20% short chain removal.

[0018] There are also established technologies for the treatment of PFAS contaminated groundwater and surface waters utilising granular activated carbon [GAC] as a sorbent or the use of both cation and anion exchange resins. GAC is effective for long chain PFCAs and PFSAs but is not as effective for the sorption of shorter chain forms. Ion-exchange resins have a high removal capacity for many forms of PFAS but can be expensive. Both of these techniques will involve either regeneration of the material and / or disposal of the accumulated concentrated PFAS / treatment material necessitating additional and substantial destructive costs, typically by incineration. Conventional organoclay technology can also be applied to the treatment of PFAS contaminated groundwater and surface waters by sorption of PFAS forms which are hydrophobic / predominantly hydrophobic. Permeable reactive barrier technology can also be applied to the treatment of PFAS contaminated groundwater.

[0019] The method described in this disclosure is a modified inorgano-organoclay which enables the treatment of a broad range of PFAS by a combination of sorption and chemical immobilisation of the anionic forms of PFAS by chemical bonding with the aluminium pillars intercalated within the clay structure. The method provides the added benefit of multi-reactivity within the clay structure and the capability to vary the hydrophobicity / hydrophilic properties of the clay structure to achieve the optimum removal of both long chain and short chain PFAS.

[0020] Detailed Description of the Invention

[0021] Conventional organoclays are produced by the intercalation of quaternary ammonium cations into the internal structure of smectite clay minerals (for example, montmorillonite) or a zeolite type clay replacing the natural occurring cations within the clay structure (typically either Na+or Ca2+) by cation exchange. The cations are present within the clay to maintain electroneutrality with the aluminosilicate clay structure of the clay which is negatively charged. This cation exchange process imparts organophilic / hydrophobic properties into the clay matrix producing the organoclay.

[0022] The organophilic / hydrophobic properties of the clay facilitate the attraction and sorption of hydrocarbon pollutants including PFAS into the clay structure. The platelets of the conventional organoclay can separate / expand enabling the sorption of hydrocarbon pollutants in both soils and groundwater.

[0023] However conventional organoclays do not provide the capability to treat a wide range of PFAS with varying chemical properties (in particular varying hydrophobicity, polarity and solubility). It is acknowledged that conventional organoclays have limited capability in the sorption of shorter chain PFAS which exhibit less hydrophobic / more hydrophilic properties. This limitation equally applies to the use of granular activated carbon for the same purpose.

[0024] In addition other factors such as pH and soil properties can influence the efficacy of organoclays in the sorption of PFAS / PFCAs / PFSAs which readily dissociate into the anionic form in the natural environment (for example carboxylates and sulfonates).

[0025] The method disclosed in this invention provides the dual capability to effectively sorb a wide range of PFAS and to chemically immobilise the PFAS molecules within the clay structure. This is achieved by combining the intercalation of quaternary ammonium cations with the intercalation of polynuclear aluminium cations which produce a modified inorgano-organoclay with reactive / chemical bonding capabilities. The polynuclear aluminium cation has the chemical formula Ali3O4(OH)24(H2O)i27+which is strongly bound to the clay with a valency of 7+. This polymer is referred to as a ‘Keggin ion’. Once intercalated, the polymer provides an effective source of aluminium cations which provide a bonding mechanism with the anionic PFAS forms through Lewis acid-base bonding with the functional ‘head’ group on the PFAS molecule (carboxylate for PCFAs and sulfonate group for PFSAs).

[0026] It is a further embodiment of this invention that the intercalation of both the quaternary ammonium cations and the polynuclear aluminium cations can be varied to reflect the project specific requirements for the sorption of PFAS and in particular the sorption of the PFCAs and PFSAs, both short chain and long chain. The combined intercalatants can be added in the required percentages to impart the necessary properties and reactivity into the clay structure. The combined intercalation will be no greater than 100% of the stoichiometric cation exchange capacity of the clay and in most cases will be less than 100% retaining a residual cation exchange capacity within the clay. It is a further embodiment of the invention that the modified inorgano-organoclay can retain a capability for the intercalation of other reactive species by retaining a residual cation exchange capacity (Na+or Ca2+cations) and / or can provide a residual cation exchange capacity for the sorption of heavy metal pollutants by cation exchange. This imparts a multi-capability into the clay structure.

[0027] In addition, the intercalated polynuclear aluminium provides a reactive capability for the treatment of metallic ions in anionic form (for example, chromates and arsenates - the reactivity of aluminium with arsenic / arsenates is cited in US 8,940.958 B2). This imparts an additional multicapability into the clay structure.

[0028] It is a further embodiment of this invention that the modified inorgano-organoclay can be prepared at the site of use, either as a component of a chemical stabilisation process to treat PFAS (and where required, other pollutants in the soil / other materials) or as a treatment medium for PFAS contamination within surface waters or groundwaters. The modified inorgano-organoclay can be used as treatment medium for contaminated groundwater within a permeable reactive barrier system.

[0029] It is this inherent flexibility which can enable a project-specific treatment medium to be prepared as required, with the capability to vary the composition and addition rate of the modified inorgano- organoclay as a project progresses (if and when required).

[0030] The modified inorgano-organoclay can be prepared by producing a slurry of a powdered smectite clay (typically sodium or calcium bentonite) added to water and thoroughly mixed, typically at a concentration of circa 13 - 14% weight by volume. The mixing process will enable the smectite clay to become fully hydrated resulting in expansion of the clay particles. The polynuclear aluminium can then be added in solution form (as aluminium chlorohydrate solution) in the required quantity to achieve the desired cation exchange / use of the available cation exchange capacity. The quaternary ammonium compound can then be added in solution form in the required quantity to achieve the desired cation exchange / use of the available cation exchange capacity to produce either a fully cation exchanged modified inorgano-organoclay (by fully utilising the remaining available cation exchange of the clay) or a partially cation exchanged modified inorgano-organoclay (by partially utilising the remaining available cation exchange capacity of the clay) leaving a residual cation exchange capacity within the clay for use as required.

[0031] Examples

[0032] Example 1

[0033] The following example demonstrates the capability of the invention to effectively treat both short chain and long chain PFAS. Treatability trials were undertaken by representatives of the chemical department of KTH Royal Institute of Technology in Stockholm. It was decided to focus on eleven PFAS chemicals, namely PFBS (Perfluorobutane sulfonic acid), PFHxS (Perfluorohexane sulfonic acid), PFOS (Perfluorooctane sulfonic acid), PFBA (Perfluorobutanoic acid), PFPeA (Perfluoropentanoic acid), PFHxA (Perfluorohexanoic acid), PFHpA (Perfluoroheptanoic acid), PFOA (Perfluorooctanoic acid), PFNA (Perfluorononanoic acid), PFDA (Perfluorodecanoic acid) and FTS (Fluorotelomer sulfonate).

[0034] PFHxS, PFOS, PFOA, PFNA and PFDA are classified as long chain PFSAs I PFCAs.

[0035] PFBS, PFBA, PFPeA. PFHxA and PFHpA are classified as short chain PFSAs / PFCAs.

[0036] FTS is an example of a polyfluoroalkyl form of PFAS.

[0037] A solution containing a modified inorgano-organoclay was prepared by slurrying 200 grams of a smectite clay (sodium bentonite) in 1.6 litres of water, equivalent to a 12.5% weight by volume slurry of sodium bentonite. The available cation exchange capacity was circa 85 milliequivalents / 100 grammes, which equated to 1360 milliequivalents for the 1 .6 litre slurried material. A 30% weight by weight solution of aluminium chlorohydrate containing the polynuclear Ali37+cation (equivalent weight 148) was added at 5% volume by volume (80 millilitres; 108 milligrams of aluminium chlorohydrate solution based on the stated specific gravity of 1 .35). This equated to 32.5 milligrams of the polynuclear cation (0.22 equivalents / 220 milliequivalents). The remaining available cation exchange capacity was 1 ,140 milliequivalents. The modified inorganoclay was then further modified by the addition of 10% volume by volume of a 50% mono-quaternary ammonium solution (176 millilitres; 172.5 milligrams of the mono-quaternary ammonium solution based on the stated specific gravity of 0.98 which contained 86.25 milligrams of the monoquaternary cation based on the 50% concentration). The 50% benzalkonium chloride solution contained 70% benzylalkyldimethyl chloride (the alkyl group being C12) and 30% benzylalkyldimethyl chloride (the alkyl group being Cu). The equivalent weights of the monovalent cations are 306 and 334 respectively, equating to an effective equivalent weight of 314 based on the stated composition). The addition of 86.25 milligrams of the mono-quaternary cation equated to 0.27 equivalents I 270 milliequivalents leaving a residual cation exchange capacity of 870 milliequivalents.

[0038] The combined intercalation of the polynuclear cation and the mono-quaternary cations produced a modified inorgano-organoclay with available residual cation exchange capacity for the further intercalation of additional reactive intercalatants as required and / or for the sorption of metallic / cationic species. It is a key embodiment of this invention that the intercalatants and their respective percentage compositions can be varied on a case-by-case basis to reflect the varying properties of PFAS. The formulation of the modified inorgano-organoclay is inherently variable within 0 - 100 per cent of the stochiometric cation exchange capacity of the smectite or zeolite clay.

[0039] It is a further embodiment that the any mono-quaternary ammonium salt can be used to produce the modified inorgano-organoclay.

[0040] The modified inorgano-organoclay prepared for this treatability study was used to treat PFAS contaminated leachate taken from the Hagby Dfeponi landfill site located near Stockholm. The samples were treated with the modified inorgano-organoclay in slurry form. The treatability study was carried out using 300 millilitres of the leachate. 100 millilitres of the slurry containing the modified inorgano-organoclay was added to the leachate sample. The resulting solution was thoroughly mixed over a period of 24 hours. The treated samples were filtered and sent for analysis along with samples of untreated water for comparison.

[0041] The treatability results are shown in Tables 1 - 3 below. The analytical limit of detection was 0.3ng / l.

[0042] Table 1 - Leachate Results - Long Chain PFAS The results demonstrated a very high percentage leachate reduction for long chain PFSAs and a high / very high percentage leachate reduction for long chain PFCAs. The results for PFHxS and PFNA reflect the level of detection constraint (i.e. the percentage reductions should be viewed as equal to or greater than the stated figure).

[0043] The results demonstrated a high / very high percentage leachate reduction for the short chain PFSA and a high I very high percentage leachate reduction for the longer short chain PFCAs. The percentage reduction for the shortest chain PFCA (PFBA) was less than the other longer short chain PFCAs. This result demonstrated that the modified inorgano-organoclay formulation for this application was primarily focused on long chain / longer short chain PFAS and that a more hydrophilic modified inorgano-organoclay should be formulated for increased percentage leachate reduction of PFAS with higher solubilities (shorter forms of short chain PFAS) - this would be achieved by decreasing the intercalation of the mono-quaternary ammonium compound, producing a different formulation for the modified inorgano-organoclay. The capability of the invention to provide this inherent flexibility is a key embodiment.

[0044] It is a further embodiment of this invention that two / multiple formulations of modified inorgano- organoclays are used in sequence and / or in parallel to achieve the most desirable and optimum solution for treating a broad range of PFAS in one operation. This was also advocated by KTH.

[0045] The results demonstrated a very high percentage leachate reduction for FTS (an example of a polyfluoroalkyl form of PFAS).

[0046] Example 2

[0047] The following example demonstrates the capability of the invention to effectively treat PFAS contamination in soils. The soil treatment process involved sorption and chemical stabilisation (immobilisation) of PFAS contaminated soil using a combination of a modified inorgano- organoclay and cementitious materials. This example also demonstrates the need to effectively control the addition of cementitious materials in the stabilisation process. PFCAs and PFSAs are present in anionic forms which are increasingly more soluble with increasing pH, which results from cement hydration processes.

[0048] The treatability trial was carried out on a sample of PFAS contaminated soil containing 42ug / kg (42,000ng / kg) PFOS. The sample was sieved to remove large stones etc (12mm sieve) and a 1 kg sub-sample was produced which was then sub-divided into four 250g sub-samples (labelled T1 - T4). A blank was also prepared for comparison purposes (TO).

[0049] The treatment mixes for this project were designed to primarily focus on PFOS.

[0050] The prime treatment medium was the designated modified inorgano-organoclay formulation (two variations with slight formulation differences to assess the effect of varying the additives, if any). Cementitious materials were also added to provide a degree of physical stabilisation - in this respect the cementitious additions were varied slightly to assess whether there were any beneficial or adverse effects (or no effects at all).

[0051] Two modified inorgano-organoclay formulations were prepared in slurry form and were formulated to treat 1kg of PFOS contaminated soil. In both cases 25g of modified inorgano- organoclay slurry was prepared (equating to an addition rate of 2.5% w / w). The two modified inorgano-organoclay formulations were described as moderately hydrophobic and more hydrophilic (less hydrophobic). The moderately hydrophobic formulation was based on the intercalation of the polynuclear cation calculated to utilise 7.5 percent of the cation exchange capacity followed by the intercalation of a mono-quaternary ammonium cation calculated to further utilise 12.5% of the cation exchange capacity (formulation A). The less hydrophobic formulation was based on the intercalation of the polynuclear cation calculated to utilise 7.5 percent of the cation exchange capacity followed by the intercalation of a mono-quaternary ammonium cation calculated to further utilise 7.5% of the cation exchange capacity (formulation B).

[0052] Four treatment mixes were formulated as follows (one for the treatment of each 250g soil sample) - these were labelled Mix T1 - Mix T4:

[0053] Mix T1 : Moderately organophilic clay (formulation A). 6.25g of slurry to be added (equivalent to 2.5% weight / weight addition). Cementitious addition 8.75g (equivalent to 3.5% weight / weight addition)

[0054] Mix T2: Moderately organophilic clay (formulation A). 6.25g of slurry to be added (equivalent to 2.5% weight I weight addition). Cementitious addition 5g (equivalent to 2% weight / weight addition)

[0055] Mix T3: More hydrophilic / less hydrophobic clay (formulation B). 6.25g of slurry to be added (equivalent to 2.5% weight / weight addition). Cementitious addition 8.75g (equivalent to 3.5% weight / weight addition)

[0056] Mix T4: More hydrophilic / less hydrophobic clay (formulation B). 6.25g of slurry to be added (equivalent to 2.5% weight / weight addition). Cementitious addition 5g (equivalent to 2% weight / weight addition)

[0057] The treatment slurries containing the modified inorgano-organoclay formulations (mix formulations T1 - T4) were thoroughly mixed into the respective 250g sub-samples of PFAS contaminated soil. Cementitious materials were added in dry form. The treated materials were then left to cure for 48 hours before testing. The untreated blank sample and the four treated samples were tested for PFOS concentrations at an accredited laboratory. Samples were leached using the CEN 10:1 Method and the leachates were analysed.

[0058] The reported total PFOS leachate concentrations are shown in Table 4 below. Total PFOS is the combined leachate concentration for the linear and branched forms of PFOS.

[0059] Table 4 - Total PFOS Leachate Concentrations (ng / l)

[0060] The treatability trial using different mix formulations results confirmed effective sorption and chemical stabilisation (immobilisation) of total PFOS within the treated soil samples. The optimum mix formulation was Mix T4 with a 99% reduction in total PFOS leachate concentration. This mix formulation provided significantly greater PFAS immobilisation than for Mix T3. This was seemingly due to the reduced cement addition (and resulting lower pH following the cement hydration curing process).

Claims

CLAIMS1 A process for treating soils, groundwater, surface water and other materials contaminated with perfluoroalkyl and polyfluoroalkyl substances [PFAS] which utilises a modified inorgano-organoclay, so as to reduce the environmental impact of PFAS.2 A modified inorgano-organoclay produced by the intercalation of a polynuclear aluminium cation and the subsequent intercalation of a mono-quaternary ammonium cation into a smectite type clay or a zeolite type clay.3 A modified inorgano-organoclay according to claim 2 where the combined intercalation of a polynuclear aluminium cation and a mono-quaternary ammonium cation is a maximum of 100% of the stoichiometric cation exchange capacity of the smectite type or zeolite type clay.4 A modified inorgano-organoclay according to claim 3 where the proportions of the intercalated polynuclear aluminium cation and mono-quaternary ammonium cation can each be varied accordingly.5 A modified inorgano-organoclay according to claim 2 where the combined intercalation of a polynuclear nuclear cation and a mono-quaternary ammonium salt is less than 100% of the stoichiometric cation exchange capacity of the smectite type clay or zeolite type clay, leaving a residual proportion of the naturally occurring cations within the clay structure.6 A modified inorgano-organoclay according to claim 5 where the proportions of the intercalated polynuclear aluminium cation and mono-quaternary ammonium cation can each be varied accordingly.7 Modified inorgano-organoclays of differing formulations in accordance with claims 2 to 6 exhibiting a broad range of hydrophopic and hydrophilic properties.8 A methodology for the treatment of PFAS contaminated soils and other PFAS contaminated materials by sorption and chemical stabilisation (immobilisation) of PFAS utilising a modified inorgano-organoclay or modified inorgano-organoclays according to claims 1 to 7.9 A methodology for the treatment of PFAS contaminated soils and other PFAS contaminated materials by sorption and chemical stabilisation (immobilisation) of PFAS utilising a modified inorgano-organoclay or modified inorgano-organoclays according to claims 1 to 8 and a cementitious additive.A methodology for the treatment of PFAS contaminated soils and other PFAS contaminated materials in accordance with claim 9 where the addition of cementitious materials is fully controlled to mitigate the potential adverse effects on the chemical stabilisation (immobilisation) of PFAS within contaminated soils and other materials as a consequence of increasing pH / alkalinity. A methodology for the treatment of PFAS contaminated groundwater by sorption and chemical immobilisation of PFAS utilising a modified inorgano-organoclay or modified inorgano-organoclays in accordance with claims 1 to 7. A methodology for the treatment of PFAS contaminated groundwater in accordance with claim 11 utilising a modified inorgano-organoclay or modified inorgano-organoclays in accordance with claims 1 to 7 as a treatment medium or treatment media within a permeable reactive barrier system. A methodology for the combined treatment of PFOS contaminated soils and groundwaters utilising a modified inorgano-organoclay or modified inorgano-organoclays in accordance with claims 1 to 12. A methodology for the treatment of PFAS contaminated surface water utilising a modified inorgano-organoclay or modified inorgano-organoclays in accordance with claims 1 to 7. A methodology for the treatment of PFAS contaminated groundwater in sequence or in parallel utilising different formulations of a modified inorgano-organoclay in accordance with claims 1 to 7. A methodology for the treatment of PFAS contaminated surface water in sequence or in parallel utilising different formulations of a modified inorgano-organoclay in accordance with claims 1 to 7. A methodology which enables a modified inorganoclay or modified inorganoclays to be formulated on a project-specific basis so as to provide the required flexibility. A methodology for the treatment of other materials contaminated with PFAS in accordance with claims 1 to 17.

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