Multi-functional filtration systems for metal and oxyanion removal

Abstract

The disclosure provides for compositions comprising multifunctional molybdenum disulfide materials, methods for making the compositions, and uses thereof.

Description

Attorney docket No.00012-087WO1 MULTI-FUNCTIONAL FILTRATION SYSTEMS FOR METAL AND OXYANION REMOVAL CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Serial No. 63 / 543,226, filed October 9, 2023, the disclosures of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The disclosure relates to membranes and membranes systems for the separation of trace components in a fluid mixture. The disclosure provides for membranes that are comprised of multifunctional molybdenum disulfide materials and uses thereof. BACKGROUND

[0003] The coexistence of water scarcity and a widespread metal and oxyanion contamination of water resources necessitates the development of innovative technologies for the treatment of alternative water resources, such as groundwater and brackish water. For example, the groundwater contamination by oxyanions such as hexavalent chromium (Cr(VI)) and selenium (Se(VI)) has been widely reported in California. The ubiquitous Cr(VI) contamination of groundwater resources in California is a result of industrial activities, natural geology, and land use. Because those oxyanions are often carcinogenic and highly toxic at a low concentration, in March 2022, California announced a Maximum Contaminant Level (MCL) of 10 ppb for Cr(VI) in drinking water that all water utilities need to comply. A recent survey reported that with an MCL of 10 ppb Cr(VI), operators of nearly 800 groundwater supply wells would be in violation, and over 1,300 monitoring wells would likely require additional review and potential regulatory oversight. Reverse osmosis (RO), nanofiltration (NF), adsorption, ion exchange, and coagulation precipitation are the state-of-the-art water treatment technologies for metal / oxyanion removal. However, these technologies are often energy intensive, non-selective, or not suitable for recovery. Therefore, advances in oxyanion removal technologies could significantly improve the potential of safely using groundwater asAttorney docket No.00012-087WO1 an alternative drinking water resource, as well as treating other oxyanion-rich water sources around the world. SUMMARY

[0004] This disclosure exploits the high removal efficiency of toxic metal ions and oxyanions by creating a multifunctional water filter using two-dimensional (2D) molybdenum disulfide (MoS) nanosheets. Particularly, MoS exhibits multiple removal pathways towards oxyanions such as Cr (VI) and Se (VI), including adsorption, reduction, and physical filtration. The multifunctionality of the MoS filters allows in situ detoxification of the oxyanions, which could greatly reduce the pressure on waste / waste stream treatment. Moreover, MoS filters can be integrated to existing water treatment processes (e.g., low-pressure micro / ultrafiltration and adsorption), which not only allows the treatment of a wide selection of non- traditional water resources (e.g., ground water and industrial wastewater), but also reduces the costs of additional steps that is required for the traditional water treatment processes to remove toxic metals

[0005] The disclosure provides a multifunctional molybdenum disulfide (MoS)-based material that can selectively remove and recover oxyanions. It was found that MoS-based materials exhibit exceptionally high selectivity toward metal ions (e.g., lead (Pb ), cadmium (Cd ), copper (Cu ) and the like), as well as effective recovery with inexpensive competitive ligand like EDTA. MoS has also demonstrated both adsorption and reduction mechanisms when removing oxyanions (e.g., Cr(IV)), allowing in situ detoxication of the oxyanion. When synthesized provided for water filtration the MoS nanosheet delivers fast water transport with water flux of 145 L / m / h / bar that is much higher than typical NF / RO membranes. Therefore, the MoS-based platform integrates reduction adsorption- filtration processes, which is highly efficient for selective removal of metal and oxyanions. This multifunctional filter can also be engineered and used under, but not limited to, membrane filtration settings and adsorption-based processes. For example, when used in membrane filtration settings the filter of the disclosure can offer the advantages of low-pressure ultrafiltration (UF) or microfiltration (MF) membranes (i.e., lower energyAttorney docket No.00012-087WO1 consumption and higher water production rate than RO and NF), yet achieving high selectivity towards targeted oxyanion species that cannot be traditionally removed by UF membranes. This allows the treatment of various water resources with reduced operational costs, addressing both water scarcity and metal contamination problems in one setting.

[0006] In a particular embodiment, the disclosure provides a composition comprising multifunctional MoS-based materials, the multifunctional MoS-based materials having a mixed hexagonal 2H phase and octahedral 1T phase (1T / 2H phase), and a morphology of interconnected multi-layer sheets, with curled, exposed edges. In a further embodiment, the multifunctional MoS-based materials have an irregular shape. In yet a further embodiment, the composition has a binding affinity for Cr(VI) in a fluid of at least 1000 mg / g. In another embodiment, a substrate comprises a plurality of layers of the MoS-based materials and polycations. In yet another embodiment, a substrate comprises one or more layers of deposited multifunctional MoS-based materials. In a further embodiment, the substrate is a solid, porous material. In yet a further embodiment, the substrate is a membrane or filter. In a certain embodiment, the membrane is an ultrafiltration or nanofiltration membrane. In a further embodiment, the substrate is an adsorption media.

[0007] In a certain embodiment, the disclosure also provides an adsorption column having adsorption media comprising multifunctional MoS-based materials disclosed herein.

[0008] In a particular embodiment, the disclosure further provides a method to synthesize the multifunctional MoS-based materials of the disclosure, comprising the step of: hydrothermally reacting MoO, urea, and thioacetamide precursors in an aqueous solvent system at an elevated temperature to form the multifunctional MoS-based materials. In a further embodiment, the elevated temperature is a temperature greater than 150 ^C.

[0009] In a certain embodiment, the disclosure also provides a method for making a membrane or filter comprising multifunctional MoS-based materials of the disclosure, the method comprising the step of: depositing the multifunctional MoS-based materials onto the surface of a membrane.Attorney docket No.00012-087WO1

[0010] In a particular embodiment, the disclosure provides a method for making a membrane or filter comprising multifunctional MoS-based materials of the disclosure, the method comprising the steps of: (i) depositing a layer of the multifunctional MoS-based materials onto a membrane or filter; (ii) adding a polyelectrolyte to the deposited layer of MoS-based materials; optionally, repeating steps (i) and (ii) until a desired amount of the multifunctional MoS-based materials are layered onto the membrane or filter.

[0011] In a certain embodiment, the disclosure also provides a method for making a mixed-matrix membrane comprising multifunctional MoS-based materials of the disclosure, comprising the step of: mixing the multifunctional MoS-based materials with a membrane casting solution to create mixed-matrix membrane.

[0012] In a particular embodiment, the disclosure further provides a method to filter a fluid stream to remove contaminants, comprising the step of: contacting the fluid stream with the composition comprising multifunctional MoS-based materials of the disclosure. In another embodiment, the contaminants are chromium ions, heavy metals and / or oxyanions. In yet another embodiment, the chromium ions are Cr(VI). In a particular embodiment, the fluid stream has a pH less than 7.0. In a further embodiment, the fluid stream is selected from groundwater, well water, drinking water, seawater, brine, wastewater, and industrial wastewater. In yet a further embodiment, the industrial wastewater is wastewater selected from mining operations, car washing, food processing, power production, agriculture, and manufacturing. DESCRIPTION OF DRAWINGS

[0013] Figure 1 provides an illustration of heavy metal and oxyanion removal from water using a multifunctional MoS membrane or filter of the disclosure.

[0014] Figure 2A-C demonstrates that MoS-based multifunctional membranes can potentially reduce the cost for treating Cr(VI) to the MCL (A) A photo of MoS-based UF membrane. (B) Levelized cost of water for SBA and MoS-based UF membrane. (C) Cost breakdown for MoS-based UF membrane.Attorney docket No.00012-087WO1

[0015] Figure 3A-F shows the chemical state and electron microscope images for the nanoparticles. (A) XPS, (B) SEM and (C)TEM images for MoS nanoparticles. (D) XPS, (E) AFM, and (F) TEM of MoS nanosheets.

[0016] Figure 4A-F demonstrates the layer-by-layer assembly approach to deposit MoS with the aid of polyelectrolyte. (A) MoS nanoparticles directly filtered onto polymer substrate (B) The stir cell used for filtration. (C) MoS nanosheets synthesized though layer-by-layer technique. (D) Illustration of the layer-by-layer technique. (E) Image and illustration of membranes prepared by spray-coating technique. (F) Image and illustration of membranes prepared by pour-and-dry technique.

[0017] Figure 5A-C shows that the MoS nanoparticles prepared by hydrothermal synthesis have excellent Cr(VI) removal performance. (A) Cr(VI) removal capacity of various MoS suspensions. (B) Cr(VI) removal in synthetic groundwater and real groundwater. (C) Cr(VI) removal with MoS-based UF membrane.

[0018] Figure 6 shows removal kinetics in membrane (main figure) and in batch reactors (inset figure).

[0019] Figure 7A-B shows (A) Normalized removal (columns) and flux (dots) of MoS membranes with the presence of various background ions. (B) Flux and Cr(VI) concentration change during 24 hours of tests.

[0020] Figure 8 shows permeability and removal rate during 96 hours of tests. 30 min membrane cleaning was performed every 18 hours. Hydrogen peroxide and citric acid were used as cleaning solution.

[0021] Figure 9A-C demonstrates that the MoS-based water membranes can be used to treat water sources with complex water chemistry. (A) Cr(VI) removal rate and (B) removal capacity under various high concentration background ions and NOM. (C) Cr(VI) removal rate under different pH.

[0022] Figure 10A-B shows (A) Selectivity of various ions. (B) Removal and recovery of Pb using MoS nanosheet-based membrane using EDTA cleaning.Attorney docket No.00012-087WO1

[0023] Figure 11 shows a comparison of reduction potentials of MoS with other pairs common in heavy metal remediation and antioxidation. DETAILED DESCRIPTION

[0024] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "an anion" includes a plurality of such anions and reference to "the fragment" includes reference to one or more fragments and equivalents thereof known to those skilled in the art, and so forth.

[0025] Also, the use of “or” means “and / or” unless stated otherwise. Similarly, “comprise,” “comprises,” “comprising” “include,” “includes,” and “including” are interchangeable and not intended to be limiting.

[0026] It is to be further understood that where descriptions of various embodiments use the term “comprising,” those skilled in the art would understand that in some specific instances, an embodiment can be alternatively described using language “consisting essentially of” or “consisting of.”

[0027] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although many methods and reagents are similar or equivalent to those described herein, the exemplary methods and materials are disclosed herein.

[0028] All publications mentioned herein are incorporated herein by reference in full for the purpose of describing and disclosing the methodologies, which might be used in connection with the description herein. Moreover, with respect to any term that is presented in one or more publications that is similar to, or identical with, a term that has been expressly defined in this disclosure, the definition of the term as expressly provided in this disclosure will control in all respects.

[0029] It should be understood that this disclosure is not limited to the particular methodology, protocols, and reagents, etc., described herein and as such may vary. The terminology used herein is for the purpose of describing particular embodiments orAttorney docket No.00012-087WO1 aspects only and is not intended to limit the scope of the present disclosure.

[0030] The term “about,” as used herein can mean within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which can depend in part on how the value is measured or determined, e.g., the limitations of the measurement system. Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood as modified in all instances by the term "about." The term "about" when used to described the present invention, in connection with percentages means ±1%. Alternatively, “about” can mean a range of plus or minus 20%, plus or minus 10%, plus or minus 5%, or plus or minus 1% of a given value. Alternatively, particularly with respect to biological systems or processes, the term can mean within an order of magnitude, within 5-fold, or within 2-fold, of a value. Where particular values are described in the application and claims, unless otherwise stated the term “about” meaning within an acceptable error range for the particular value can be assumed. Also, where ranges and / or subranges of values are provided, the ranges and / or subranges can include the endpoints of the ranges and / or subranges. In some cases, variations can include an amount or concentration of 20%, 10%, 5%, 1 %, 0.5%, or even 0.1 % of the specified amount.

[0031] For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.

[0032] As used herein a “fluid” refers to a liquid or gas. The fluid can be a multicomponent fluid containing a plurality of molecular entities.

[0033] As used herein a “membrane” refers to a permeable, selectively permeable or non-permeable film that can be used to divide or separate a first fluid from a second fluid or filter a fluid such that fluid can pass through the membrane.Attorney docket No.00012-087WO1

[0034] Porous membranes of the disclosure comprise a layer of a membrane of sheet or stacked layers of a membrane or sheets (e.g., nanosheets). In one embodiment, the nanosheets include one to ten (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) atomic layers of a 2D material comprising or consisting of MoS particles (e.g., nanoparticles) and optionally pores having diameters in the range from about 10 nm to about 60 nm. The membrane comprises a network of water permeation pathways that include through-pathways formed by, in one embodiment, the pores, and in another embodiment, the horizontal pathways formed by gaps between the layers, and vertical pathways formed by gaps between adjacent nanosheets and stacking defects between the layers. The thickness of each membranes in a stack is in the range of 2 nm to 900nm, e.g., from 5 nm to about 1 μm. The MoS particles may be uniformly distributed in the membrane or may be non-uniformly distributed. The membranes may have a uniform pore size or a non-uniform pore size. By “uniform pore size” is meant that the pore size between two pores does not differ by more than 0.1%, 0.5% or 1%.

[0035] The disclosure also provides a composite comprising a MoS nanosheet layered upon a second membrane that can be impermeable or that has a selectivity to a desired molecular entity to be captured or separated.

[0036] Exemplary polymers that may be used to construct the composite membranes include, but are not limited to: polyolefins such as polyethylene, polypropylene, polybutene-1, and poly(4-methyl pentene-1), including polyvinyls and fluoropolymer variants thereof, for example polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl ester (e.g., polyvinyl acetate and polyvinyl propionate), polyvinyl pyridine, polyvinyl pyrrolidone, polyvinyl ether, polyvinyl ketone, polyvinyl aldehyde (e.g., polyvinyl formal and polyvinyl butyral), polyvinyl amide, polyvinyl amine, polyvinyl urethane, polyvinyl urea, polyvinyl phosphate, and polyvinyl sulfate; polystyrene (e.g., isotactic polystyrene and syndiotactic polystyrene), including styrene-containing copolymers such as acrylonitrilestyrene copolymers, styrene-butadiene copolymers and styrene-Attorney docket No.00012-087WO1 vinylbenzylhalide copolymers; thermoplastic elastomers (TPE); silicones such as polydimethylsiloxane (PDMS) and polymethylphenylsilicone (PMPS); polyacetylenes such as polytrimethylsilylpropyne; polysulfones including polyethersulfones (PESs) as well as sulfonated PESs, with specific mention being made to poly(1,4-phenylene ether-ether-sulfone), poly(l-hexadecene- sulfone), poly(l-tetradecene-sulfone), poly(oxy- 1,4phenylenesulfonyl-1,4-phenylene), poly(oxy-1,4-phenylenesulfonyl- 1,4-phenylene), poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), polyphenylsulfone, and ULTRASON S 6010 from BASF; polysulfonamides such as poly[1-[4- (3-carboxy-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl]- ); polyacetals; polyethers; polyethylenimines; polycarbonates; cellulosic polymers such as cellulose acetate, cellulose triacetate, cellulose acetate-butyrate, cellulose propionate, ethyl cellulose, methyl cellulose, and nitrocellulose; polyamides including aromatic polyamides and aliphatic polyamides, such as Nylon 6 and polyphthalamide; polyimides with specific mention being made to KAPTON (poly (4,4'-oxydiphenylene-pyromellitimide) by DuPont, MATRIMID® by Huntsman Advanced Materials, P84 by HP Polymers GmbH, poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-pyromellitic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline) (or poly(BTDA-PMDA-TMMDA)), poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-pyromellitic dianhydride-4,4'-oxydiphthalic anhydride- 3,3',5,5'-tetramethyl-4,4'-methylene dianiline) (or poly(BTDA-PMDA- ODPA-TMMDA)), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline) (or poly(DSDA-TMMDA)), poly(3,3',4,4'-benzophenone tetracarboxylic dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline) (or poly(BTDA-TMMDA)), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-pyromellitic dianhydride-3,3',5,5'-tetramethyl-4,4'- methylene dianiline) (or poly(DSDA-PMDA-TMMDA)), and poly[2,2'-bis- (3,4-dicarboxyphenyl) hexafluoropropane dianhydride-2,2-bis(3-amino- 4-hydroxyphenyl)-hexafluoropropane] (or poly(6FDA-APAF)), poly[2,2'- bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-2,4,6- trimethyl-1,3-phenylenediamine] (or poly(6FDA-DAM), poly[3,3',4,4'- benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-Attorney docket No.00012-087WO1 hydroxyphenyl)-hexafluoropropane] (or poly(BTDA-APAF)), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-3,3'- dihydroxy-4,4'-diamino-biphenyl) (or poly(BTDA-HAB)), poly[4,4'- oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)- hexafluoropropane] (or poly(ODPA-APAF)), poly[3,3',4,4'- diphenylsulfone tetracarboxylic dianhydride-2,2-bis(3-amino-4- hydroxyphenyl)-hexafluoropropane] (or poly(DSDA-APAF)), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-3,3'- dihydroxy-4,4'-diamino-biphenyl) (or poly(DSDA-HAB)), poly[2,2'-bis- (3,4-dicarboxyphenyl) hexafluoropropane dianhydride-3,3',4,4'- benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4- hydroxyphenyl)-hexafluoropropane] (or poly(6FDA-BTDA-APAF)), poly[4,4'-oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)- hexafluoropropane-3,3'-dihydro- xy-4,4'-diamino-biphenyl] (or poly(ODPA-APAF-HAB)), poly[3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane-3,3'- dihyd- roxy-4,4'-diamino-biphenyl] (or poly(BTDA-APAF-HAB)), poly[2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride- 3,3'-dihydroxy-4,4'-diamino-biphenyl] (or poly(6FDA-HAB)), and poly(4,4'-bisphenol A dianhydride-3,3',4,4'- benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4- hydroxyphenyl)-hexafluoropropane) (or poly(BPADA-BTDA-APAF)); polyetherimides such as ULTEM products manufactured by Sabic Innovative Plastics; polyamide imides; polyketones; polyether ketones such as polyether ether ketone, sulfonated polyether ether ketone and the like; polyarylene oxides such as polyphenylene oxide, polyxylene oxide, sulfonated polyxylene oxide and brominated polyxylene oxide; polyurethanes; polyureas; polyazomethines; polyesters including polyarylates such as polyethylene terephthalate and polyphenylene terephthalate; acrylates such as polyalkyl (meth)acrylate, polyacrylate, polyacrylate-polyacrylamide copolymers; polysulfides; heterocyclic thermoplastics such as polybenzimidazoles, polyoxadiazoles, polytriazoles, polybenzoxazole, and polybenzimidazole; polycarbodiimides; polyphosphazines; polyhydrazides; and copolymers thereof, including block copolymers, grafts, and blends thereof.Attorney docket No.00012-087WO1

[0037] “Hexavalent chromium” or “Cr(VI)” is a known carcinogenic compound that has high solubility and mobility in natural waters. The most acute cases of environmental Cr(VI) contamination are anthropogenic activities such as plating and leather tanning industry, while natural dissolution of minerals (e.g., mafic and ultramafic rock) is also suspected to have significant impacts on drinking water supplies, especially groundwater sources. Studies have revealed that in many regions such as in California, North Carolina, Greece, and Mexico, there can be a high impact from Cr(VI) contamination associated with ultramafic aquifers. In United States, the current federal drinking water standard for total chromium is 100 ^g / L, while Cr(VI) was not regulated. In 2011, the Office of Environmental Health Hazard Assessment suggested a public health goal (PHG) of 0.02 ^g / L Cr(VI) based on the studies by the National Toxicology Program. While limited data can be found for the prevalence of Cr(VI) across US, according to the groundwater information system of the California Water Board, around 2454 drinking water wells and 1903 monitoring wells have Cr(VI) concentration higher than the PHG in the past 3 years. In respond to the concern of long term effect of having Cr(VI) in drinking water, the CA Water Boards proposed a maximum contamination level (MCL) of 10 ^g / L in 2022, resulting in around 2.8 million population potentially supplied with drinking water violating this regulation.

[0038] Conventional water treatment processes include coagulation and flocculation, adsorption and filtration. These processes often require extensive chemical input and face challenges in removing trace heavy metals. While membrane filters like Reverse Osmosis / Nanofiltration (RO / NF) provide high-quality water treatment through physical separation, their feasibility is limited by their high energy and maintenance requirements.

[0039] The current state of the art for Cr(VI) removal includes reduction-coagulation-filtration (RCF), strong and weak base anion exchange (SBA / WBA), and membrane filtration. While all were shown to be able to reduce Cr(VI) to below 10 ppb (the maximum contamination level (MCL)), some limitations apply. For example, RCF may not be economically feasible to be applied to small treatment systems due to its high infrastructure costs; the efficiency of ion exchangeAttorney docket No.00012-087WO1 resins can be greatly reduced under high sulfate and nitrate environment, which will increase the operational cost for brine disposal; reverse Osmosis or nanofiltration grade membranes have excellent performance but can also be expensive for small scale treatment due to its extensive energy requirement. According to the cost analysis by the California Water Board, the total annual cost is around $179 million to reach the MCL using the aforementioned technologies.

[0040] Furthermore, contaminants that remain in the waste stream require additional treatment, resulting in high disposal cost or secondary pollution. Therefore, multifunctional water filters capable of removing or detoxifying metals and oxyanions while also providing separation are useful.

[0041] Molybdenum disulfide (MoS) is a type of transition-metal dichalcogenides that has great capability of removing toxic metal ions such as lead, silver and mercury. It can effectively remove hexavalent chromium (Cr(VI)) by first reducing it to trivalent chromium (Cr(III)), followed by direct adsorption and precipitation as chromium molybdate onto an MoS surface. MoS can be synthesized into various shapes (single-layer nanosheets vs. multi-layer nanoparticles) and phases (1T vs. 2H) depending upon the desired applications. With the nano-micron scale size and robust mechanical strength, MoS can be integrated with existing water treatment platforms as multifunctional adsorption columns and ultrafiltration membranes.

[0042] MoS-based materials have notable advantages in oxyanion removal, including, but not limited to: (1) reduced sludge production compared to coagulation or precipitation-based technologies; (2) consistent high-level performance with reduced impacts from other competitive ions that are often found in ground waters that decrease the performance of ion exchange / adsorption technologies; (3) higher adsorption capacity that can be easily regenerated in comparison to traditional adsorbents (e.g., iron oxide and activated carbon), such that the lifetime and / or backwashing cycles are much longer; and (4) adaptable to various settings, such as membranes or adsorptive columns, depending on the needs. Moreover, when used as membrane filters, it will have muchAttorney docket No.00012-087WO1 higher flux or lower operational pressure than RO / NF, reduced capital and operational cost, and offers high recovery and reduce concentrate volume. Therefore, the multifunctional filter disclosed herein reduces the operational costs, simplifies maintenance, and minimizes the impacts of environmental factors compared to other oxyanion treatment technologies.

[0043] The use of MoS-based multifunctional filters has high potential to reduce the cost for Cr(VI) removal to the MCL. FIG. 2A shows an example of MoS-based ultrafiltration (UF) membrane, prepared by directing MoS containing filtrate onto an ultrafiltration (UF) substrate. The levelized cost of water (LCOW) for implementing the MoS-UF membrane can be as low as $0.32 / m, whereas for SBA technology with the same water treatment capacity, has a cost around $0.48 / m (see FIG. 2B-C). Additionally, given the fact that UF membranes are commonly used in water treatment systems, the capital cost may further reduce if the MoS-UF membrane is used as an add-on to the existing UF modules.

[0044] The compositions and methods of the disclosure offer flexibility, simple operation, cost-effectiveness, high compatibility, and adaptability for efficient removal of oxyanions such as Cr (VI) and Se (VI). This is achieved by the multifunctional MoS-based materials that integrates oxyanion reduction, adsorption, and membrane filtration in a one-step treatment process. The method and compositions of the disclosure enable a platform technology for efficient removal of oxyanions from a variety of water resources. The multifunctional MoS-based materials disclosed herein provides for Cr and Se removal from a fluid at operating conditions that are not typically feasible for MF / UF membranes. With the high-flux and low-pressure features of MF / UF settings, the compositions of the disclosure significantly lower the operational costs for treating oxyanion contamination. With Cr and Se widely detected at a concentration above their MCLs in California groundwater and waterbodies around the world, the compositions and methods of the disclosure will help broaden water resources, improve water quality and reliability, and reduce the cost of water supplies. Moreover, the methods and compositions can provide a compact system for treating non-traditional water resources. It will have applicationsAttorney docket No.00012-087WO1 in various water sectors, including chromium and selenium removal from industrial wastewater and ground water, heavy metal (e.g., cadmium) removal in agricultural applications, as well as point-of- entry or point-of-use household treatment systems for lead removal from drinking water.

[0045] In one embodiment, the disclosure provides a multifunctional filter using two-dimensional (2D) molybdenum disulfide (MoS) nanosheets that have high removal efficiency of toxic metal ions and oxyanions. In another embodiment, the disclosure provides a multifunctional filter using molybdenum disulfide (MoS) particles on or embedded in a polymer filter substrate. Particularly, MoS exhibits multiple removal pathways towards oxyanions such as Cr (VI) and Se (VI), including adsorption, reduction, and physical filtration. The multifunctionality of the MoS-based materials allows in situ detoxification of the oxyanions, which could greatly reduce the pressure on waste water stream treatment. Moreover, MoS filters can be integrated to existing water treatment processes (e.g., low-pressure micro / ultrafiltration and adsorption), which not only allows the treatment of a wide selection of non-traditional water resources (e.g., ground water and industrial wastewater), but also reduces the costs of additional steps that are required for traditional water treatment processes to remove toxic metals. In a particular embodiment, a water purification system comprises a multifunctional MoS-based material disclosed herein. In yet a further embodiment, the water purification system can be linked to a commercial or municipal potable water source.

[0046] In a particular embodiment, the disclosure provides a composition comprising multifunctional MoS-based materials, the multifunctional MoS-based materials having a mixed hexagonal 2H phase and octahedral 1T phase (1T / 2H phase), and a morphology of interconnected multi-layer sheets, optionally with curled, exposed edges. In a further embodiment, the multifunctional MoS-based materials have an irregular shape (e.g., a cauliflower shape). In yet a further embodiment, the composition has a binding affinity for Cr(VI) in a fluid of at least 500 mg / g, 550 mg / g, 600 mg / g, 650 mg / g, 700 mg / g, 750 mg / g, 800 mg / g, 850 mg / g, 900 mg / g, 950 mg / g,Attorney docket No.00012-087WO1 1000 mg / g, 1100 mg / g, 1200 mg / g, 1300 mg / g, 1400 mg / g, 1500 mg / g, 1600 mg / g, 1700 mg / g, 1800 mg / g, 1900 mg / g, 2000 mg / g, or a range that includes or is between any two of the foregoing values. In another embodiment, a substrate comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 50 layers, or a range of layers that includes or is between any two of the foregoing values, of the multifunctional MoS-based materials and polycations. In yet another embodiment, a substrate comprises one or more layers of deposited multifunctional MoS-based materials. In a further embodiment, the substrate is a solid, porous material. In yet a further embodiment, the substrate is a membrane or filter. In a certain embodiment, the membrane is an ultrafiltration or nanofiltration membrane. In a further embodiment, the substrate is an adsorption media.

[0047] In a certain embodiment, the disclosure also provides an adsorption column having adsorption media comprising multifunctional MoS-based materials disclosed herein. In one embodiment, nanoparticles of MoS are dispersed in the adsorption column.

[0048] In a particular embodiment, the disclosure further provides a method to synthesize the multifunctional MoS-based materials of the disclosure, comprising the step of: hydrothermally reacting MoO, urea, and thioacetamide precursors in an aqueous solvent system at an elevated temperature to form the multifunctional MoS-based materials. In a further embodiment, the elevated temperature is a temperature of 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, 155 °C, 160 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, or a range that includes or is between any two of the foregoing temperatures. In yet further embodiment, the hydrothermal reaction is carried out in a pressure regulating device, such as a pressure reactor or pressure vessel.

[0049] In a certain embodiment, the disclosure also provides a method for making a membrane or filter comprising multifunctional MoS-based materials of the disclosure, the method comprising the step of: depositing the multifunctional MoS-based materials onto the surface of a membrane.

[0050] In a particular embodiment, the disclosure provides a method for making a membrane or filter comprising multifunctionalAttorney docket No.00012-087WO1 MoS-based materials of the disclosure, the method comprising the steps of: (i) depositing a layer of the multifunctional MoS-based materials onto a membrane or filter; (ii) adding a polyelectrolyte to the deposited layer of multifunctional MoS-based materials; optionally, repeating steps (i) and (ii) until a desired amount of the multifunctional MoS-based materials are layered onto the membrane or filter.

[0051] In a certain embodiment, the disclosure also provides a method for making a mixed-matrix membrane comprising multifunctional MoS-based materials of the disclosure, comprising the step of: mixing the multifunctional MoS-based materials with a membrane casting solution to create mixed-matrix membrane.

[0052] The MoS-based membrane can be used as a multifunctional membrane for many other applications to remove heavy metal and oxyanion contaminants in addition to Cr(VI). As the MoS-based membrane can absorb and reduce other heavy metals, such as Pb, Hg, Cd, Se, As, Zn, and Ag, it can also be used for resource recovery. In a particular embodiment, the disclosure provides a method of using a multifunctional MoS-based material of the disclosure, comprising: separating unwanted ion species (e.g., oxyanions) and / or heavy metals from a fluid by contacting the fluid with a multifunctional MoS-based material disclosed herein under low- pressure (e.g., microfiltration and ultrafiltration membrane). In a further embodiment, the fluid includes, but is not limited to, groundwater, seawater, industrial wastewater, brine, and agricultural water treatment.

[0053] In a particular embodiment, the disclosure further provides a method to filter a fluid stream to remove contaminants, comprising the step of: contacting the fluid stream with the composition comprising multifunctional MoS-based materials of the disclosure. In another embodiment, the contaminants are chromium ions, heavy metals and / or oxyanions. In yet another embodiment, the chromium ions are Cr(VI). In a particular embodiment, the fluid stream has a pH of 6.8, 6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, or a range of pHs that is between or includes any two of the foregoing pHs. In a further embodiment, the fluid stream is selected from groundwater, well water, drinking water, seawater,Attorney docket No.00012-087WO1 brine, wastewater, and industrial wastewater. In yet a further embodiment, the industrial wastewater is wastewater from mining operations, car washing, food processing, power production, agriculture, or manufacturing.

[0054] In a particular embodiment, a multifunctional MoS-based material disclosed herein is an article of manufacture configured for power plants, wastewater treatment plants, and for industry. In another embodiment, a multifunctional MoS-based material disclosed herein is an article of manufacture configured for point-of-use (POU) small water treatment systems to be used in individual households. For example, US has long-standing issue with lead contamination of drinking water from lead-containing water pipes. A POU multifunctional MoS-based material will be able to help mitigate this issue by effectively removing lead from tap water.

[0055] In another embodiment, the disclosure provides for applying a multifunctional MoS-based material disclosed herein onto adsorption media that is then packed into an adsorption column. The configuration and operation conditions of the adsorption column are different from that of membrane filtration, but the same removal mechanisms would still apply. EXAMPLES

[0056] Material and filter preparation. MoS with various morphology and crystalline phases can be prepared to better align with the needs for the treatment of traditional / non-traditional water sources. MoS nanoparticles (NP-MoS) were prepared using a hydrothermal process with MoO, urea and thioacetamide precursors. FIG. 3A-C shows the chemical state and electron microscope images for the nanoparticles. These nanoparticles have a mixed 1T / 2H phase, and a cauliflower morphology that has numerous interconnected multi- layer sheets, with edges curled and exposed. Single-layer MoS nanosheets (NS-MoS) were also prepared through chemical exfoliation, where n-butyllithium was used as the intercalation agent. Figure 3D-F shows the chemical state and electron microscope images for the nanosheets. These nanosheets also have a mixed 1T / 2H phase, with around 1.3 nm thin layer thickness.

[0057] Regardless of its phases and morphologies, MoS can be made into a membrane filters though several strategies. Pressure-Attorney docket No.00012-087WO1 assisted deposition of MoS nanosheets onto a polymeric membrane substrate can be used. This method is simple and fast which potentially allows in situ deposition of MoS within membrane modules. A similar approach can be used to deposit the hydrothermally synthesized MoS, as shown in FIG. 4A-B. A different layer-by-layer assembly approach to synthesize the membrane was also used. FIG. 4C-D shows the layer-by-layer assembly approach to deposit MoS with the aid of a polyelectrolyte. This method can add additional charge properties to the MoS membrane. Figure 4E-F shows alternative deposition techniques (spray-coating and pour-and-dry) that is applicable for large-scale membrane synthesis. Depending on the size and shape of MoS, as well as the amount of material added, the MoS membranes can be made into ultrafiltration or nanofiltration membranes through the above strategies. Other methods such as mixing MoS into membrane casting solutions to create mixed matrix membranes or making free-standing membranes that do not have polymer substrates can also be used.

[0058] The MoS nanoparticles prepared by hydrothermal synthesis that are high in 1T phase exhibited excellent Cr(VI) removal performance. When a MoS suspension was directly used to treat Cr(VI) contaminated water, Cr(VI) removal was high as 1600 mg Cr(VI) / g-MoS (see FIG. 5A). The removal was proven to be effective in a groundwater matrix, as shown in FIG. 5B. FIG. 5C demonstrates the filtration performance using MoS-based UF membranes made by pressure-assisted deposition. The membrane permeability and removal rate showed a thickness-dependency. At operation pressure of 15 psi (1 bar), the membrane flux ranged from 50 liter per square meter per hour (LMH) to 17 LMH. Membranes with an MoS layer thicker than 1 micrometer showed removal of Cr(VI) below the 10 ppb MCL in the treated water (permeate). Membranes with a 2.5 micrometer MoS layer were able to remove Cr(VI) to a concentration as lows as 1ppb.

[0059] When MoS was made into water filters (e.g., ultrafiltration membranes, as shown in FIG. 4A), the removal kinetics were significantly enhanced. Figure 6A shows that the removal kinetic in membrane is 48.8 s , 5 magnitudes higher than in batch reactors (2.3*10 s ). As a result, the MoS membrane was ableAttorney docket No.00012-087WO1 to reduce the Cr(VI) concentration to below the MCL in less than 0.1 s.

[0060] The removal performance of the MoS membrane was not affected by common water constituent. As shown in FIG. 7A, the flux and removal rate did not vary with the presence of various types of ions and natural organic matters NOM. Figure 7B shows flux and removal of 24-hour filtration test. No significant change of flux and the Cr(VI) concentration in the permeate was observed.

[0061] The MoS membrane can be periodically cleaned using typical UF membrane cleaning reagents (e.g., citric acid and HO solutions) to recover the membrane’s filtration performance. For examples, as shown in FIG. 8, although the flux and removal rate gradually declined during test, cleaning using citric acid and HO solutions had effectively recovered the membrane’s performance.

[0062] Applications for MoS-based water filters. MoS-based water filters can be used to treat water sources with complex water chemistry, including conventional drinking water resources and industrial wastewater. As can be seen from FIG. 9A-B the removal rate and capacity for Cr(VI) did not change with a high concentration of background ions that are commonly seen in water resources. Particularly, the presence of high concentrations of sulfate, which can greatly increase the cost for SBA technology, did not affect the performance. This makes it possible to use MoS-based filters to treat most of the conventional water sources without compromising performance. FIG. 9C shows that the removal rate was much faster in lower pHs. Wastewater such as acid mine drainage, leather tanning waste, and metal plating waste that contains high level of Cr(VI) and low pH therefore can therefore be efficiently treated by MoS-based membranes. Currently, industrial wastewaters are mainly treated through RCF technology. The use of MoS membranes modules can greatly reduce the capital cost, for it can be made into stackable modules, and reduce waste disposal cost, as the reduced Cr(VI) can be precipitated and adsorbed onto MoS surface during treatment.

[0063] The MoS-based water filters can also be used for resource recovery. Based on the previous study MoS can selectively remove various heavy metals such as lead (740 mg / g removalAttorney docket No.00012-087WO1 capacity), copper, and silver (980 mg / g removal capacity). For example, FIG. 10A-B shows the removal and recovery of Pb using MoS nanosheet-based membranes. The MoS nanosheet showed a highly selective removal of lead and copper, and 91% of the Pb removed by MoS membrane can be recovered using Ethylenediaminetetraacetic acid (EDTA).

[0064] Additionally, the MoS-based water filters can recover critical minerals for energy that are widely found in industrial wastewaters and geological water source. For example, according to the National Energy Water Treatment and Speciation (NEWTS) database, industrial wastewater including produced water, acid mine drainage and ash pond effluent contains cobalt (Co), manganese (Mn) and nickel (Ni) that are critical minerals and likely to face supply risk within 10 years. Based on the study of the redox potential of MoS (FIG. 11), MoS-based water filters has high potential to isolate the aforementioned critical minerals through either adsorption (Ni, Co) or combined redox-adsorption (Mn) from resource- rich water source.

[0065] It will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims.

Claims

Attorney docket No.00012-087WO1 WHAT IS CLAIMED IS:

1. A composition comprising multifunctional MoS-based materials, the multifunctional MoS-based materials having a mixed hexagonal 2H phase and octahedral 1T phase (1T / 2H phase), and a morphology of interconnected multi-layer sheets.

2. The composition of claim 1, wherein the multifunctional MoS- based materials have an irregular shape.

3. The composition of claim 1 or claim 2, wherein the composition has a binding affinity for Cr(VI) in a fluid of at least 1000 mg Cr(VI) / g MoS.

4. The composition of claim 1 or 2, wherein a substrate comprises a plurality of layers of the multifunctional MoS-based materials and polycations.

5. The composition of claim 1 or 2, wherein a substrate comprises multifunctional MoS-basedmaterials.

6. The composition of claim 5, wherein the substrate is a solid,7. The composition of claim 5, wherein the substrate is a8. The composition of claim 7, wherein the membrane is an ultrafiltrationnanofiltration membrane.

9. The composition of claim 5, wherein the substrate is an10. An adsorption column comprising the adsorption media of claimAttorney docket No.00012-087WO1 11. A method to synthesize the multifunctional MoS-based materials of claim 1 or 2, comprising the step of: hydrothermally reacting MoO, urea, and thioacetamide precursors in an aqueous solvent system at an elevated temperature to form the multifunctional MoS-based materials.

12. The method of claim 11, wherein the elevated temperature is a temperature greater than 150 ^C.

13. The method of claim 11, wherein the method further comprises making a membrane or filter comprising the multifunctional MoS- based materials, the method comprising the step of: depositing the multifunctional MoS-based materials onto the surface of a membrane.

14. The method of claim 11, wherein the method further comprises making a membrane or filter comprising the multifunctional MoS- based materials, the method comprising: (i) depositing a layer of the multifunctional MoS-based materials onto a membrane or filter; (ii) adding a polyelectrolyte to the deposited layer of the MoS-based materials; optionally, repeating steps (i) and (ii) until a desired amount of the multifunctional MoS-based materials are layered onto the membrane or filter.

15. The method of claim 11, wherein the method further comprises making a mixed-matrix membrane, comprising the step of: mixing the multifunctional MoS-based materials with a membrane casting solution to create mixed-matrix membrane.

16. A method to filter a fluid stream to remove contaminants, comprising the step of: contacting the fluid stream with the composition of any one of claims 1 to 9.Attorney docket No.00012-087WO1 17. The method of claim 16, wherein the contaminants are chromium ions, heavy metals and / or oxyanions.

18. The method of claim 17, wherein the chromium ions are Cr(VI).

19. The method of claim 16, wherein the fluid stream has a pH less than 7.

0.

20. The method of claim 16, wherein the fluid stream is selected from groundwater, well water, drinking water, seawater, brine, wastewater, and industrial wastewater.

21. The method of claim 20, wherein the industrial wastewater is wastewater selected from mining operations, car washing, food processing, power production, agriculture, and manufacturing.

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