Standardised method for measurement of sorption efficacy of a sorbent

Abstract

The present disclosure relates to the remediation of contaminated materials. In a particular form, the present disclosure relates to a method that supports remediation processes which involve the use of sorbents. The method allows contaminant sorption efficacy to be determined for a variety of sorbent types across a variety of materials, such as those typically found at industrial sites, including soils, mining tailings and by-products, sludge wastes, industrial wastes, tunnelling and excavation spoils, rock and asphalt (or mixtures thereof).

Description

STANDARDISED METHOD FOR MEASUREMENT OF SORPTION EFFICACY OF A SORBENTTECHNICAL FIELD

[0001] The present disclosure relates to the remediation of contaminated materials. In a particular form, the present disclosure relates to a method that supports remediation processes which involve the use of sorbents.BACKGROUND

[0002] Soil and other materials at former industrial sites are often contaminated with a number of different organic and inorganic substances, including per- and polyfluoroalkyl substances (PFASs), which are of concern from a health and environmental perspective. Before such a site can be redeveloped for residential or other use, the materials must be remediated to remove or minimise the risk that such contaminants may otherwise pose. The remediation can be done on-site, or, in some cases, such as in infrastructure projects where contaminated material is excavated and transported to other sites for reuse or disposal, materials that have been removed from a site may also need to be treated to minimise the risk of contaminants leaching off-site.

[0003] A common method of remediating such materials involves the use of sorbents which absorb or adsorb the contaminants. The sorbents are applied to, for example, the soil and blended with the soil, resulting in the conversion of one or more contaminants to a less soluble, mobile and / or toxic form, and leading to a reduction in the hazard potential of the material. Where this stabilisation results in a less soluble or mobile contaminant, this leads to a reduced level of leachability of that contaminant from the material. In turn, this results in a reduced risk that the material could cause groundwater contamination and / or toxicity to humans or animals contacting the material.

[0004] Typically, sorbents are blended into contaminated materials at a known percentage (% w / w) to immobilize contaminants. However, contaminants are a structurally diverse group of compounds, and they therefore bind to sorbents by various binding mechanisms. There is presently no simple and effective method that allows one to assess the capacity of a sorbent to bind to the specific contaminant, or mixture of contaminants, present at a site. Current approaches to assessing sorbent performance include:• Measuring the iodine number (e.g., Standard Test for Determination of Iodine Number of Activated Carbon, ASTM D4607-14 2021);• Measuring the methylene blue value (e.g., European Council of Chemical Manufacturers’ Federation Test Methods for Activated Carbon 1986);Measuring the specific surface area (SSA) (e.g., ISO 9277:2010 Determination of the specificsurface area of solids by gas absorption - BET method 2010);• Applying a dye test for capacity (e.g., Sorengard, M. et al. (2020) J Env Chem Eng, vol. 8(3); 10374);• Sorption / desorption kinetics modelling (e.g., European Council of Chemical Manufacturers’ Federation, Test Methods for Activated Carbon 1986); and• Leaching procedure testing (e.g., Australian Standard Leaching Procedure (ASLP) tests, Australian Standard AS4439).

[0005] All the above-mentioned methods work well to describe the physical and chemical properties of powdered and granular activated carbon products. However, when these methods are applied to sorbents that are not wholly carbon based (such as anion exchange resins, mixed mineral products, organoclays and other novel sorbents), the limitations of these methods become evident. For example, the iodine number, SSA and dye tests do not provide a measure of contaminant sorption, cannot be calculated for a particular sorbent type and / or are not cross compatible with other test methods. This means that there is no way to make a comparison between carbon-based sorbents and other sorbents to compare contaminant sorption efficacy using these tests. Sorption / desorption kinetic modelling does offer a direct way to determine the sorption and desorption kinetics of a sorbent product for contaminants that is then comparable to other products. The disadvantage of this method, however, is that kinetics studies require multiple samples to be analysed over multiple time points. Therefore, it is not cost or time efficient to complete kinetics studies for standardizing the characterization of contaminant sorbent product efficacy. Further, for the results to be comparable, studies need to be completed in the same concentration range and experimental conditions, which is often not possible, particularly for on-site testing. Regarding the ASLP procedure, this measures contaminant leachability over a set period to simulate 100 years in a landfill. The method is only applied to soil or treated soil samples with no easily calculable kinetics information once testing is complete, and it only calculates the leachable fraction but does not account for sorption as a single measure. It also does not allow for the easy comparison of different sorbents.

[0006] There is thus a need to provide a method that allows contaminant sorption efficacy to be determined for a variety of sorbent types, and for the results to be directly comparable between sorbents, regardless of a sorbent’s composition. The method should also allow for a single, standardized test to be used, and be amenable to the presence of various matrix types (e.g., soil, sand, mining tailings and byproducts).SUMMARY

[0007] According to a first aspect, there is provided a method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution and a contaminant to determine an initial contaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate binding of the contaminant to the sorbent, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV :NR = PS - PD (Formula IV), and12) Calculating a Standardised Single Quality Method (SSQM) score using Formula V:SSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an SSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto, and an SSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto, and wherein Step 4) can be carried out after Step 5).

[0008] The method may include an additional step of adding a sample of a soil or other matrix to determine the efficacy of a sorbent for sorbing a contaminant thereto in the presence of the matrix. Therefore, in a second aspect, there is also provided a method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution, a contaminant and a matrix to determine an initialcontaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate sorption of the contaminant to the sorbent and / or the matrix, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent and / or the matrix into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV :NR = PS - PD (Formula IV), and12) Calculating a Matrix-Matched Standardised Single Quality Method (MSQM) score using Formula V:MSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an MSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto in the presence of the matrix, and an MSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto in the presence of the matrix, and wherein Step 4) can be carried out after Step 5).

[0009] The solution of the first mixture may be an aqueous solution. The aqueous solution may be water. The water may be purified water.

[0010] The contaminant may be added to the first mixture from a stock solution of the contaminant.The contaminant may be added to the first mixture to achieve a contaminant concentration of about 1 mg / L in the second mixture. The stock solution may be an alcohol solution. The alcohol may be methanol or ethanol.

[0011] Where the matrix is also present in the first mixture, the weight ratio of solution to matrix may be about 1:20.

[0012] In the second mixture, when no matrix is present (i.e., in the first aspect), the weight ratio of solution to sorbent may be about 2500:1. In the embodiment where matrix is present in the second mixture (i.e., in the second aspect), the weight ratio of solution to sorbent may be about 25:1.

[0013] The aqueous solution devoid of contaminant may be pure water. The pure water may be ultrapure water.

[0014] The contaminant may be an organic contaminant. The organic contaminant may be a per- and poly-fluorinated substance (PFAS).

[0015] The sorbent may be an alum-based sorbent, a carbon-based sorbent, a mineral-based sorbent, a resin-based sorbent, or a combination thereof.

[0016] The matrix may be soil, mining tailings and by-products, sludge waste, industrial waste, tunnelling and excavation spoils, rock, asphalt, compost, biosolids, or mixtures thereof.BRIEF DESCRIPTION OF DRAWINGS

[0017] Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

[0018] Figure 1 is a flow chart depicting the application of one embodiment of the method of the present invention - in sorbent application optioning;

[0019] Figure 2 is a flow chart depicting a summary of an embodiment of the method of the present invention;

[0020] Figure 3 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorohexanesulfonic acid (PFHxS);

[0021] Figure 4 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorooctane sulfonate (PFOS);

[0022] Figure 5 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorobutanesulfonic acid (PFBS);

[0023] Figure 6 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorobutanoic acid (PFBA);

[0024] Figure 7 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorohexanoic acid (PFHxA); and

[0025] Figure 8 is a graph showing the SSQM score of various sorbents in respect of the PFAS perfluorooctanoic acid (PFOA).DESCRIPTION OF EMBODIMENTS

[0026] The present inventors have surprisingly found that the efficacy with which a sorbent absorbs or adsorbs a contaminant from, for example, a site or material requiring remediation, can be assessed using well-understood experimental procedures, analytical methods, and simple calculations, in a way that also allows a variety of sorbent types to be compared with each other.

[0027] There is therefore provided a method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution and a contaminant to determine an initial contaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate binding of the contaminant to the sorbent, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV :NR = PS - PD (Formula IV), and12) Calculating a Standardised Single Quality Method (SSQM) score using Formula V:SSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an SSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto, and an SSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto, and wherein Step 4) can be carried out after Step 5).

[0028] The present inventors have also surprisingly found that the method is amenable to the assessment of sorbent efficacy in the presence of a matrix, such as a soil. Therefore, the method may include an additional step of adding a sample of a soil or other matrix to determine the efficacy of a sorbent for sorbing a contaminant thereto in the presence of the matrix. Therefore, there is also provided a method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution, a contaminant, and a matrix to determine an initial contaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate sorption of the contaminant to the sorbent and / or the matrix, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent and / or the matrix into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV :NR = PS - PD (Formula IV), and12) Calculating a Matrix-Matched Standardised Single Quality Method (MSQM) score using Formula V:MSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an MSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto in the presence of the matrix, and an MSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto in the presence of the matrix, and wherein Step 4) may be carried out after Step 5).

[0029] The methods defined above are designed to be quick, simple, cheap and effective. They can directly measure the contaminant sorption / desorption in an economical and effective way. A set of values is produced that allows one to compare sorbent product efficacy for use in contamination treatment in a standardized way. The methods provide a way to benchmark sorbent products of any composition for comparison between product types, and reduce the cost of testing and benchmarking contaminant sorption efficacy significantly compared to kinetics / isothermal modelling.

[0030] The contaminants that may be used in the methods will reflect those that are typically present at remediation sites, and include inorganic contaminants such as metals, metalloids, halogens and nutrients (particularly, one or more of antimony, arsenic, boron, cadmium, chromium, cobalt, copper, cyanide, fluoride, lead, manganese, mercury, molybdenum, nickel, phosphate, selenium, uranium, and zinc) and organic contaminants including, for example, polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH), "benzene, toluene, ethylbenzene and xylenes" (BTEX), benzo[a]pyrene (B(a)P), volatile organic compounds (VOCs), organic pesticides and herbicides, fertilisers, polychlorinated biphenyls (PCBs), per- and poly-fluorinated hydrocarbons (PFASs) such as perfluorooctanesulfonate (PFOS), dioxins, explosive residues, polybrominated diphenyl ethers (PBDEs), disinfection byproducts, and specific organic compounds such as naphthalene, carbon tetrachloride and trichloroethylene, N-(l,3- dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD), and combinations thereof. The contaminant may be an organic contaminant. The organic contaminant may be a per- or poly-fluorinated hydrocarbon (PFAS).

[0031] The sorbent may be any sorbent that is typically used for the stabilisation of inorganic contaminants, organic contaminants, or the simultaneous stabilisation of inorganic and organiccontaminants. The sorbent may be an alum-based sorbent, a carbon-based sorbent, a mineral-based sorbent, a resin-based sorbent, or a combination thereof. Examples of carbon-based sorbents are activated charcoal, and Biochar, which is a product of the slow pyrolysis of biomass. An example of a mineralbased sorbent is Fluoro-Sorb®, which is composed of bentonite and long-chain quaternary ammonium salts. An example of an alum-based sorbent is an alum sludge composition. A suitable alum sludge composition is described in WO 2011 / 038459. The sorbent may be an alum-based sorbent or a carbonbased sorbent, or a combination thereof. A combination of an alum-based sorbent and a carbon-based sorbent is also described in WO 2011 / 038459 and is sold under the trade name RemBind®.

[0032] The methods comprise the first step (Step 1) of testing a first mixture comprising a solution and a contaminant (and, in one method, a matrix) to determine an initial contaminant concentration (“IC”). The IC is the initial concentration of the contaminant in the solution of the first mixture and is intended to reflect the concentration of the contaminant before any, or before any substantial, sorption of the contaminant to the sorbent (and, in one method, the matrix) has occurred. Typically, the solution and contaminant will be combined and briefly mixed. The testing can be conducted by any means known to be suitable to a person skilled in the art. For example, an aliquot of the mixture may be removed, processed appropriately, and analysed by, for example, Eiquid Chromatography-Mass Spectrometry (LC- MS) to determine the IC.

[0033] The solution of the first mixture may be an aqueous solution. The aqueous solution may be water. The water may be purified water. The purified water may have been obtained through purification by, for example, distillation and / or filtration. The purified water may be ultrapure water.

[0034] The contaminant may be added to the first mixture from a stock solution of the contaminant. The concentration of the contaminant in the stock solution may be about 50 mg / E. The contaminant may be added to the first mixture to achieve a contaminant concentration of about 1 mg / L in the second mixture. Preferably, the contaminant concentration will be as close to 1 mg / L as possible, but when a matrix is also used in the method, there may be some variation in this as there may be some contaminant already present in the matrix. Further, a dilution of the first mixture may be carried out if, for example, a particular volume of the second mixture is required of to carry out Step 3) of the methods. The stock solution may be an alcohol solution. The alcohol may be methanol or ethanol. Reagent grade alcohol solutions may be used. Testing the first mixture, as discussed above, will confirm the concentration of the contaminant in the first mixture i.e., the IC.

[0035] Where a matrix is also used, it will be understood by a person skilled in the art that the matrix that may be used will reflect those materials that are typically present at remediation sites. Matrices that have already been contaminated (for example, matrices obtained from sites requiring remediation) or matrices that have not yet been contaminated can be used in the methods. The methods may be applied to any matrix type, however, the methods are particularly suitable for application to matrices such as soils,mining tailings and by-products, sludge wastes (e.g. effluent treatment sludges), industrial wastes, tunnelling and excavation spoils, rock, asphalt, compost and biosolids, or mixtures thereof. Preferably, the matrix is soil. The methods may be used in land management (i.e., where soil is treated with sorbent and reused on the same site), and may also be applied to contaminated matrix that has been taken from a site, such as stockpiled material, transient soil, and in treatment facilities.

[0036] Where the matrix is also present in the first mixture, the weight ratio of solution to matrix may be about 1:20. The term “about” in the context of this weight ratio is intended to refer to a variation of + / - 5%.

[0037] In Step 2), sorbent is added to the first mixture to produce a second mixture. In the second mixture, in the embodiment where no matrix is present (i.e., where the SSQM score is sought to be calculated), the weight ratio of solution to sorbent may be about 2500:1. In the second mixture, in the embodiment where matrix is present (i.e., where the MSQM score is sought to be calculated), the weight ratio of solution to sorbent may be about 25:1. The term “about” in the context of these weight ratios is intended to refer to a variation of + / - 5%.

[0038] Step 3) of the methods comprises subjecting the second mixture to conditions sufficient to facilitate sorption of the contaminant to the sorbent (and, when present, the matrix), thereby producing a third mixture. The phrase “conditions sufficient to facilitate sorption of the contaminant to the sorbent” refers to any conditions that the first mixture may be subjected to that induce, or allow, the contaminant to adsorb onto or absorb into the sorbent in such a way that the contaminant is retained on or by the sorbent. The phrase “conditions sufficient to facilitate sorption of the contaminant to the sorbent and / or the matrix” refers to any conditions that the first mixture may be subjected to that induce, or allow, the contaminant to adsorb onto or absorb into the sorbent and / or matrix in such a way that the contaminant is retained on or by the sorbent and / or the matrix. By including an appropriate matrix in the method, any potential effects that the matrix may have on the efficacy of the sorbent at sorbing the contaminant can be observed. In this way, the performance of a particular sorbent at sorbing a contaminant in a real setting e.g., in a remediation site, can be assessed. Accordingly, either the same matrix that is present at a site of interest, or a matrix that is composed of a very similar material as that present at a site of interest, may be used. The conditions may be achieved by agitating the first mixture in any suitable way known to a person skilled in the art. For example, the mixture may be shaken, centrifuged, or stirred. The first mixture may be shaken (e.g., tumbled) for about 24 hours at about 30 rpm. An example of a suitable apparatus is an end-over-end shaker. The agitation may be carried out at room temperature.

[0039] Step 4) of the methods comprises testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”). The SC is the concentration of the contaminant remaining in the solution after the second mixture has been subjected to conditions that facilitate sorption of the contaminant to the sorbent (and, in the case where matrix is also present, to the matrix) and is thereforeintended to reflect the amount of contaminant that has not been sorbed by the sorbent (and / or the matrix). The testing can be conducted by any means known to be suitable to a person skilled in the art. For example, an aliquot of the mixture may be removed, processed appropriately, and analysed by, for example, Liquid Chromatography-Mass Spectrometry (LC-MS) to determine the SC.

[0040] Step 5) of the methods comprises replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture. In this step, the solution present in the third mixture may be removed by, for example, carefully decanting the solution from the mixture. Ideally, in this step, as little as possible of the remaining components of the mixture are removed along with the liquid. Therefore, it may be preferable to allow the mixture to settle for a period of time after Step 3) and before removing the liquid. Once the liquid has been removed, an aqueous solution is added to the remaining components, thereby forming a fourth mixture. The aqueous solution should not contain any (or should contain only an undetectable amount) of the contaminant(s) that are being assessed using the methods. Accordingly, the aqueous solution of Step 5) should be devoid of the contaminant. The aqueous solution may be water. The water may be pure water i.e., purified water. The purified water may have been obtained through purification by, for example, distillation and / or filtration. The water may be ultrapure water (also commonly known as high purity water or highly purified water).

[0041] A person skilled in the art will understand that, rather than testing the third mixture after Step 3), the third mixture could be tested after the liquid has been removed from the second mixture (and replaced with an aqueous solution), as in Step 5). That is, the liquid that has been removed from the third mixture can be tested to determine the SC. Therefore, in the methods of the present invention, the order of Steps 4) and 5) can be reversed, such that Step 4) may be carried out after Step 5).

[0042] By replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant, the amount of contaminant that desorbs from the sorbent (and / or the matrix) may be determined.Accordingly, Step 6) comprises subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent (and / or the matrix) into the aqueous solution, thereby forming a fifth mixture. The phrase “conditions sufficient to facilitate desorption of the contaminant from the sorbent” refers to any conditions that the fourth mixture may be subjected to that induce, or allow, the contaminant that has so far remained sorbed onto or into the sorbent to detach or desorb from the sorbent in such a way that the contaminant leeches from the sorbent into the aqueous solution. The phrase “conditions sufficient to facilitate desorption of the contaminant from the sorbent and / or the matrix” refers to any conditions that the fourth mixture may be subjected to that induce, or allow, the contaminant that has so far remained sorbed onto or into the sorbent and / or the matrix to detach or desorb from the sorbent and / or the matrix in such a way that the contaminant leeches from the sorbent and / or the matrix into the aqueous solution. The conditions may be achieved by agitating the fourth mixture in any suitable way known to a person skilled in the art. For example, the mixture may be shaken, centrifuged, or stirred. The fourth mixture may be shaken (e.g., tumbled) for about 24 hours at about 30 rpm. An example of asuitable apparatus is an end-over-end shaker. The agitation may be carried out at room temperature.

[0043] Step 7) comprises testing the fifth mixture, formed by agitating the fourth mixture, to determine the concentration of the contaminant in the aqueous solution (“DC”). The DC is the concentration of the contaminant in the solution after the fourth mixture has been subjected to conditions that facilitate desorption of the contaminant from the sorbent (and, in the case where matrix is also present, from the matrix) and is therefore intended to reflect the amount of contaminant that was sorbed by the sorbent (and / or the matrix) in Step 3). The testing can be conducted by any means known to be suitable to a person skilled in the art. For example, an aliquot of the mixture may be removed, processed appropriately, and analysed by, for example, Liquid Chromatography-Mass Spectrometry (LC-MS) to determine the DC.

[0044] The IC, SC and DC obtained as described above can then be used to calculate SSQM and / or MSQM scores using Formulae I to V defined in Steps 8 to 12 above. The parameters referred to in Formulae I to V are described as follows.

[0045] The Percentage Sorbed (PS) measures the proportion of contaminant mass removed from the solution by the sorbent (and / or the matrix, in the method where a matrix is present in Step 1). This value can range from 1% to 100%. A high PS (i.e., >90 %) means that the sorbent has performed well at removing the contaminant under the standardized testing conditions.

[0046] The Percentage Desorbed (PD) measures the proportion of the contaminant that has been remobilized into the aqueous solution devoid of the contaminant, based on the IC. A low PD (e.g., of about 1 to about 5%) means that contaminant sorption to the sorbent (and / or the matrix) is not easily reversible.

[0047] The Performance Quotient (PQ) is a measure of the irreversible sorption / desorption of the contaminant and is heavily weighted towards desorption. A higher PQ is desirable, however, if a small amount of the contaminant is remobilized during the desorption testing (i.e., Step 6)) this will greatly decrease the PQ. Therefore, the PQ needs to be considered in the context of the PS and PD.

[0048] The Net Removal (NR) is the total percentage mass of the contaminant that has been removed from the first mixture irreversibly under the standardized conditions. As with PS, higher numbers show better performance of the sorbent, with values ranging from 0% to 100%.

[0049] The SSQM score is based on the PQ and the NR, with both weighted evenly. Higher performing sorbents will exhibit a higher SSQM score. An SSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto, and an SSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto.

[0050] The MSQM score is much like the SSQM score, except that it presents the outcomes for themethod including a matrix, where a control (containing no sorbent) is used to estimate the total contaminant sorbed by the matrix, and the difference between SSQM and MSQM (once corrected for the control) is the impact of the matrix on sorption / desorption of the contaminant to the sorbent.

[0051] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[0052] It will be understood that the terms “comprise” and “include” and any of their derivatives (e.g., comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features.

[0053] It will be appreciated by a person skilled in the art that a reference to “a” component (e.g., a contaminant, a sorbent, or a matrix), does not mean that the methods of the present invention are limited to the use of only one contaminant, one sorbent or one matrix, for example. The methods of the present invention only require that at least one contaminant, at least one sorbent and / or at least one matrix be present.

[0054] The invention is hereinafter described with reference to the following, non-limiting examples.EXAMPLES

[0055] Example 1

[0056] The flow chart in Figure 2 summarises the following exemplary method, where the contaminants of interest are PFASs. For Steps i and ii, a solution to solid weight ratio of 25:1 is used, with a total sorbent value of approximately 1% weight by weight. For Steps iii, iv and v, a solution to solid (matrix, or matrix plus sorbent) weight ratio of 1:20 is used with a 1% sorbent weight by weight value (i.e., the ratio of sorbent to solid has been standardized, such that the mass of sorbent is 1% of the matrix, even when a matrix is not used). i. A PFAS spiking stock solution containing all PFAS to be tested by SSQM is prepared at 50 mg / L in methanol (50 mg / L for each tested PFAS species in the combined stock). ii. 25 - 250 g of sorbent based on final test solution volume of 50 - 500 mL is weighed out into a PP or HDPE test vessel. iii. For MSQM only, 2.5 - 25 g of matrix sample is weighed into test the vessel. iv. 24 - 240 mL of ultrapure water is added to the test vessel. v. A 1 - 10 mL aliquot of spiking solution is added to test vessel.vi. The final 24 - 240 mL of ultrapure water is added to test vessel to make the final volume (50 - 500 mL) at a final concentration of 1 mg / L PFAS for each tested species in the test solution. A solution to solid ratio of 1:20 is used for final volume. vii. Test vessels are weighed and recorded. viii. Test vessels with sorbent, matrix (if MSQM), and PFAS solution are tumbled at 30 rotations per minute for 24 hours. ix. Glass fibre filters are pre-dried and weighed before end of tumbling period. x. Test solutions are left to settle for 30 minutes and a 5 mL aliquot is removed, centrifuged, diluted with methanol to 50:50 (MeOJLFLO), filtered using syringe filters, and prepared for analysis by LC-MS / MS. xi. Test solution is decanted from test vessels through dried glass fibre filters with care taken to avoid sorbent loss from solution. Glass fibre filters are then dried for 4 hours at 100 °C and weighed to determine sorbent mass loss. xii. The test vessel still containing sorbent, matrix, and some final test solution is weighed and recorded. xiii. For desorption, 50 - 500 mL of ultrapure water is added to these test vessels and weighed. xiv. Test vessels with sorbent, matrix (if MSQM), and PFAS test solution are tumbled at 30 rotations per minute for 24 hours. xv. Test solutions are left to settle for 30 minutes and a 5 mL aliquot is removed, centrifuged, diluted with methanol to 50:50 (MeOJLFLO), filtered using syringe filters, and prepared for analysis by LC-MS / MS. xvi. Calculation of percentage sorbed, percentage desorbed, performance quotient, net removal percentage, and SSQM / MSQM score are completed as per the following Tables.

[0057] The following Tables 1 to 6 demonstrate the results of following the SSQM method described in Steps i to xvi above. No matrix was added, and the following sorbents were used: S 1 to S7 are experimental carbonaceous sorbents derived from waste organics under different pyrolysis conditions (sold as Green Man Biochar and produced by pyrolyzing the trunk and limbs of invasive trees in an oxygen-limited environment, followed by quenching with water to develop pore microstructure) ; PAC is a high-performance lignite-derived activated carbon that has undergone an acid and / or steam activation process (also sold as ActiCarb); MM is a mixed mineral product (an alum and carbon blend). The higher the SSQM score, the more effective the sorbent is at binding the contaminant.TABLE 1SSQM perfluorooctane sulfonate (PFOS) results.TABLE 2SSQM perfluorooctanoic acid (PFOA) results.TABLE 3SSQM perfluorohexanesulfonic acid (PFHxS) results.

[0058] Example 2

[0059] The following Tables 7 to 12, and Figures 3 to 8, demonstrate further results of following the SSQM method described in Steps i to xvi in Example 1, using different sorbents. No matrix was added, and the following sorbents were used: F-100, F-200, F-300 and F-400, where F-100, -200, etc, is Fluorosorb- 100, etc; PS900 and PS1300, both of which are an activated carbon from lignite materials, and 900 and 1300 refer to the specific surface area; R100 is RemBind 100; SI to S7 are experimental carbonaceous sorbents derived from waste organics under different pyrolysis conditions (as described in Example 1); GMBF is Biochar; GMBUF is ultrafine Biochar; SAND is quartz sand.TAB EE 7PFBS SSQM results.TABLE 8PFBA SSQM results.TABLE 9PFHxS SSQM results.TABLE 11PFOS SSQM results.TABLE 12PFOA SSQM results.

[0060] A summary of the PFAS species’ SSQM scores is given in Table 13.

[0061] Example 3

[0062] The following Tables 14 to 19 demonstrate results of following an MSQM method as described in Steps i to xvi in Example 1 , using two different matrices (clay and quartz sand) and two sorbents (MM and PAC).TABLE 14PFBS MSQM results.TABLE 15PFBA MSQM results.TABLE 16PFHxS MSQM results.TABLE 17PFHxA MSQM results.TABLE 18PFOS MSQM results.TABLE 19PFOA MSQM results.TABLE 20SSQM, MSQM and Matrix Effect Results for MM and PAC sorbents for two matrices

[0063] It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present disclosure restricted in its preferred embodiment with regard to the particular elements and / or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims

CLAIMS1. A method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution and a contaminant to determine an initial contaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate binding of the contaminant to the sorbent, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV:NR = PS - PD (Formula IV), and12) Calculating a Standardised Single Quality Method (SSQM) score using Formula V:SSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an SSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto, and an SSQM score closer to 100 indicates that the sorbent has high efficacy at sorbing the contaminant thereto, and wherein Step 4) can be carried out after Step 5).

2. The method of claim 1, wherein the weight ratio of solution to sorbent is about 2500:1 in the second mixture.

3. A method of determining the efficacy of a sorbent at sorbing a contaminant thereto, the method comprising the following steps:1) Testing a first mixture comprising a solution, a contaminant and a matrix to determine an initial contaminant concentration (“IC”);2) Adding a sorbent to the first mixture to produce a second mixture;3) Subjecting the second mixture to conditions sufficient to facilitate sorption of the contaminant to the sorbent and / or the matrix, thereby producing a third mixture;4) Testing the third mixture to determine the concentration of the contaminant remaining in the solution (“SC”);5) Replacing the liquid in the third mixture with an aqueous solution devoid of the contaminant to give a fourth mixture;6) Subjecting the fourth mixture to conditions sufficient to facilitate the desorption of the contaminant from the sorbent and / or the matrix into the aqueous solution, thereby forming a fifth mixture;7) Testing the fifth mixture to determine the concentration of the contaminant in the aqueous solution (“DC”);8) Calculating a Percentage Sorbed (PS) using Formula I:PS = [1 - (SC / IC)] x 100 (Formula I)9) Calculating a Percentage Desorbed (PD) using Formula II:PD = (DC / IC) x 100 (Formula II)10) Calculating a Performance Quotient (PQ) using Formula III:PQ = PS / PD (Formula III)11) Calculating a Net Removal (NR) using Formula IV :NR = PS - PD (Formula IV), and12) Calculating a Matrix-Matched Standardised Single Quality Method (MSQM) score using Formula V:MSQM = [(PQ + NR) / 200] x 100 (Formula V), wherein an MSQM score closer to 1 indicates that the sorbent has low efficacy at sorbing the contaminant thereto in the presence of the matrix, and an MSQM score closer to 100 indicates thatthe sorbent has high efficacy at sorbing the contaminant thereto in the presence of the matrix, and wherein Step 4) can be carried out after Step 5).

4. The method of claim 3, wherein the weight ratio of solution to matrix in the first mixture is about 1:20.

5. The method of claim 3 or claim 4, wherein the weight ratio of solution to sorbent is about 25: 1 in the second mixture.

6. The method of any one of the preceding claims, wherein the solution of the first mixture is an aqueous solution.

7. The method of claim 6, wherein the aqueous solution is water.

8. The method of claim 7, wherein the water is purified water.

9. The method of any one of the preceding claims, wherein the contaminant is added to the first mixture from a stock solution of the contaminant.

10. The method of claim 9, wherein the stock solution is an alcohol solution.

11. The method of any one of the preceding claims, wherein the contaminant is added to the first mixture to achieve a contaminant concentration of about 1 mg / L in the second mixture.

12. The method of any one of the preceding claims, wherein the aqueous solution devoid of contaminant is pure water.

13. The method of claim 12, wherein the pure water is ultrapure water.

14. The method of any one of the preceding claims, wherein the contaminant is an organic contaminant.

15. The method of claim 14, wherein the organic contaminant is a per- and poly-fluorinated substance (PFAS).

16. The method of any one of the preceding claims, wherein the sorbent is an alum-based sorbent, a carbon-based sorbent, a mineral-based sorbent, a resin-based sorbent, or a combination thereof.

17. The method of any one of the preceding claims, wherein the matrix is soil, mining tailings and by-products, sludge waste, industrial waste, tunnelling and excavation spoils, rock, asphalt, compost, biosolids, or mixtures thereof.

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