WO2025101687A1 - Molécules à auto-assemblage sur des couches actives atomiquement minces - Google Patents

Molécules à auto-assemblage sur des couches actives atomiquement minces Download PDF

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WO2025101687A1
WO2025101687A1 PCT/US2024/054838 US2024054838W WO2025101687A1 WO 2025101687 A1 WO2025101687 A1 WO 2025101687A1 US 2024054838 W US2024054838 W US 2024054838W WO 2025101687 A1 WO2025101687 A1 WO 2025101687A1
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charged polymer
selective
atomically thin
layer
polymer layer
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Simar Kaur MATTEWAL
Rohit N. Karnik
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Massachusetts Institute of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/1214—Chemically bonded layers, e.g. cross-linking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/1216—Three or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/14—Membrane materials having negatively charged functional groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/16—Membrane materials having positively charged functional groups

Definitions

  • Ionic separations are used in myriad different applications. The most common application is removal of salts from water, and treatment of wastewater. Beyond that they have also found use in applications such as energy storage, with ion transfer being part of many redox flow battery systems. These separations are also used in recovery of minerals, like rare earth elements, lithium, cobalt, etc., which are relevant to the clean energy infrastructure. Recovery of such minerals is often done from acidic leachates downstream of many mining processes or through recycling of electronics. These separations are hard using size-selective membranes as their ionic sizes (hydrated diameters in aqueous media) are very similar.
  • Nanoporous atomically thin membranes like nanoporous graphene membranes allow for high permeance that enables rapid and energy -efficient separations.
  • the active layer may be made of derivatives of these materials, e.g., hydrogenated graphene, oxygenated graphene, fluorinated graphene, etc.
  • the active selective layer is typically supported on another porous material support, such as inorganic supports like alumina, titanium, zinc oxide; organic supports like polyacrylonitrile (PAN), polyethersulfone (PES), polysulfones (PSf), poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polyetherimide (PEI), polyimide (PI), polyamide (PA), cellulose acetate (CA) and polyethylene (PE).
  • PAN polyacrylonitrile
  • PES polyethersulfone
  • PSf poly(vinylidene fluoride)
  • PVDF polytetrafluoroethylene
  • PEI polyetherimide
  • PI polyimide
  • PA cellulose acetate
  • CA cellulose acetate
  • PE polyethylene
  • the subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of one or more systems and/or articles.
  • a selective membrane comprises an atomically thin active layer with a plurality of selective pores.
  • the selective membrane may have a first surface opposite from a second surface.
  • the selective membrane comprises a first charged polymer layer.
  • the first charged polymer layer is disposed on the first surface of the atomically thin active layer.
  • the selective membrane includes a second charged polymer layer having an opposite charge to a charge of the first charged polymer layer.
  • the second charged polymer layer is disposed on the second surface of the atomically thin active layer.
  • at least a portion of the first charged polymer layer and the second charged polymer layer are bonded through the plurality of selective pores of the atomically thin active layer.
  • the first surface and/or second surface are functionalized to covalently and/or non-covalently bond to the first charged polymer layer and/or the second charged polymer layer.
  • a method of fabricating a selective membrane includes functionalizing a first surface of an atomically thin active layer and/or a second surface of the atomically thin active layer opposite from the first surface.
  • the atomically thin active layer includes a plurality of selective pores.
  • the method includes bonding a first charged polymer layer disposed on the first surface of the atomically thin active layer to a second charged polymer layer disposed on the second surface of the atomically thin active layer through the plurality of selective pores.
  • the method includes covalently and/or non- covalently bonding the first charged polymer layer to the first surface and/or the second charged polymer layer to the second surface.
  • a selective membrane comprises an atomically thin active layer comprising a plurality of selective pores and a first surface opposite from a second surface.
  • the selective membrane includes a plurality of alternating charged polymer layers disposed on the first surface of the atomically thin active layer.
  • the plurality of alternating charged polymer layers includes a first charged polymer layer disposed directly against the first surface of the atomically thin active layer.
  • the selective membrane includes a second charged polymer layer having an opposite charge to a charge of the first charged polymer layer and disposed on the second surface of the atomically thin active layer.
  • at least a portion of the first polymer and the second polymer are bonded through the plurality of selective pores of the atomically thin active layer.
  • a method of separating ions is included.
  • the method may include exposing the selective membrane of any one of the preceding embodiments to a liquid containing ions.
  • the method may include transporting the ions across the selective membrane.
  • Fig. 1 A is an atomically thin active layer with a plurality of selective pores according to some embodiments
  • Fig IB is an atomically thin active layer with a plurality of selective pores and charged polymer layers with opposite charges disposed on opposite surfaces of the atomically thin active layer according to some embodiments;
  • Fig. 2A is an atomically thin active layer with functional groups configured to bond charged polymer layers on opposite surfaces of the atomically thin active layer according to some embodiments;
  • Fig. 2B is charged polymer layers disposed on an atomically thin active layer, where the charged polymer layers have selective functional groups according to some embodiments;
  • Fig. 2C is a selective pore of a plurality of selective pores of an atomically thin active layer with charged polymer layers having selective functional groups according to some embodiments;
  • Fig. 3 A is a configuration for assembling a first charged polymer layer and a second charged polymer layer on an atomically thin active layer according to some embodiments;
  • Fig. 3B is a configuration for assembling one or more alternating layers of a first charged polymer layer and a second charged polymer layer on an atomically thin active layer according to some embodiments;
  • Fig. 4A is a schematic diagram for fabricating membranes with a first charged polymer layer and a second charged polymer layer according to some embodiments
  • Fig. 4B is a schematic diagram for fabricating membranes with one or more alternating layers of a first charged polymer layer and a second charged polymer layer according to some embodiments;
  • Fig. 5 shows a flow diagram for a method of fabricating membranes according to some embodiments
  • Fig. 6A shows permeance of membranes with and without charged polymer layers according to some embodiments
  • Fig. 6B shows selectivity of membranes with and without charged polymer layers according to some embodiments
  • Fig. 7A shows permeance of membranes with and without atomically thin active layers according to some embodiments
  • Fig. 7B shows selectivity of membranes with and without atomically thin active layers according to some embodiments
  • Fig. 8A shows permeance of membranes with different methods of fabricating selective pores according to some embodiments
  • Fig. 8B shows selectivity of membranes with different methods of fabricating selective pores according to some embodiments
  • Fig. 9A shows the effect of pH on permeance of membranes according to some embodiments.
  • Fig. 9B shows the effect of pH on selectivity of membranes according to some embodiments.
  • Fig. 10A shows permeance of membranes with different types of charged polymer layers according to some embodiments
  • Fig. 10B shows selectivity of membranes with different types of charged polymer layers according to some embodiments.
  • Fig. 11 shows selectivity of ions in a membrane according to some embodiments.
  • the present disclosure describes systems and methods for tuning the performance of membranes.
  • Membranes are used for any of a variety of applications, including ionic separations, micropollutant removal, gas separations, recycling of industrial elements, among others.
  • Previously developments to improve the functionality of membranes have focused on blocking flow through defects, such that flow of species is primarily constrained through the selective pores of membranes and selective transport can be achieved.
  • One limitation for attaining high selectivity in membranes is the variability in pore size of the selective pores formed in the atomically thin active layers, which is generally a result of the membrane growth process.
  • the Inventors have recognized that membranes with selective pores may benefit from being modified to enhance their selectivity to one or more desired species (e.g., ions, small molecules).
  • Atomically thin active layers are generally a component of some membranes.
  • Some atomically thin active layers have high chemical resistance, which makes it amenable to processing of acidic leachate solutions to recover critical minerals.
  • Atomically thin active layers e.g., graphene
  • Atomically thin active layers rely on rigid size-selective pores, promising improved separation efficiency.
  • Non-selective pores e.g., defects
  • the Inventors have recognized that the use of charged polymer layers with opposite charges disposed on opposing sides of an atomically thin active layer may improve a selectivity and uniformity of a plurality of selective pores formed in the atomically thin active layer.
  • these same polymers have resulted in blocking transport through defects and selective pores the charged polymer layers are applied to.
  • the Inventors have also recognized that by increasing a bond strength between the charged polymer layers and the atomically thin active layers, it is possible to mediate the interaction of the charged polymer layers with the plurality of selective pores to still permit passage of one or more desired species of through the plurality of selective pores.
  • a first charged polymer layer and a second charged polymer layer are disposed on an atomically thin active layer of a membrane such that the atomically thin active layer is between the charged polymer layers.
  • a plurality of selective pores extends through the atomically thin active layers between opposing surfaces of the atomically thin active layer. These selective pores may be used to control the transport of one or more desired species across the membrane.
  • the surfaces of the atomically thin active layer, and optionally the charged polymer layers may be functionalized to increase a bonding strength between the polymer layers and the atomically thin active layer as compared to the atomically thin active layer and the charged polymer layers without functionalization.
  • the charged polymer layers disposed on the opposing sides of the atomically thin active layer may bond to one another through the plurality of selective pores.
  • Such bonded portion may contribute to an increased selectivity of the membrane, as at least a portion of the plurality of selective pore may have a bonded portion of the charged polymer layers disposed therein with certain enhanced selective properties (e.g., ability to bond certain ions selectively, a decreased pore size, etc.) .
  • the presence of the first charged polymer layer and/or second charged polymer layer on any of the surfaces of the atomically thin active material may be evaluated and/or confirmed by spectroscopic techniques, such as X-ray photoelectron spectroscopy (XPS).
  • XPS X-ray photoelectron spectroscopy
  • the atomically thin active layer may have functional groups that are configured to covalently and/or non-covalently bond with the adjacent charged polymer layers. This enhanced bonding between the layers may lead to membrane with enhanced permeability, selectivity, and performance for the desired one or more target species. In certain aspects, the presence of these functional groups on the atomically thin active layer may facilitate the selfassembly of charged polymer layers onto the atomically thin active layer.
  • the charged polymer layers may be positioned, disposed on, or otherwise deposited on the atomically thin active layer in certain configurations.
  • a first charged polymer layer may be disposed on a first surface of an atomically thin active layer.
  • a second charged polymer layer may be disposed on a second surface of the atomically thin active layer.
  • the first surface and the second surface can be opposite sides of the atomically thin active layer such that a charged polymer layer of a different type is disposed on opposing sides of the atomically thin active layer.
  • the first charged polymer layer and the second charged polymer layer may substantially cover an entirety of the opposing surfaces of the atomically thin active layer.
  • each of the charged polymer layers (e.g., first charged polymer layer and second charged polymer layer) form a single layer on each side of the atomically thin active layer.
  • one or more additional layers may be present on either side of the atomically thin active layer where the additional layers may be formed by charged polymer layers with alternating charges.
  • the atomically thin active layer can be functionalized.
  • the atomically thin active layer may comprise functional groups that can bond with charged polymer layers, such the charged polymers layers can be assembled (e.g., self-assembled) on one or more surfaces of the atomically thin active layer.
  • the presence of certain functional groups on the atomically thin active layer can bond the charged polymers.
  • Some types of bonding include non-covalent bonding (e.g., ionic bonding, hydrogen bonding, electrostatic interactions) and covalent bonding (e.g., polar covalent bonding, non-polar covalent bonding). Additionally, some types of bonding between the charged polymer layers and the atomically thin active layer are hydrophilic or hydrophobic interactions. For example, surfactants, hydrophobic polymers, block copolymers with hydrophobic and hydrophilic blocks, alkane-based self-assembled monolayers, among others. Some examples of functional groups include carboxylic groups, hydroxyl groups, epoxy groups, amine groups, and/or any other appropriate functional groups configured to enhance bonding between the atomically thin active layer and the first and second charged polymer layers.
  • the above-mentioned first and second surfaces of the atomically thin active layer can be functionalized to bond, attach, and/or otherwise be configured to facilitate the assembly and/or bonding of the charged polymer layers thereon.
  • the functional groups may be selected to covalently and/or non-covalently bond the functionalized surfaces of the atomically thin active layer to the adjacent charged polymer layers.
  • selective functional groups of the charged polymer layers can facilitate bonding with the atomically thin active layer and thus promote self-assembly.
  • certain moi eties e.g., charged polymer backbone
  • present in charged polymer layers are configured to facilitate bonding with the atomically thin active layer.
  • the bonding is may be at least partially directed by functional groups of the atomically thin active layer, although selective functional groups on the charged polymer layers may be present.
  • enhanced bonding between the charged polymer layers and the atomically thin active layer may be provided by functional groups present on both the charged polymer layers and the surfaces of the atomically thin active layer.
  • the charged polymer layers can have selective functional groups that may provide enhanced selectivity to the membrane by enhancing affinity to certain ions or molecules.
  • the selective functional groups may be present in a polyelectrolyte or other charged polymer as disclosed herein, for example.
  • Some examples of selective functional groups that can provide some selectivity include chelating agents, amides, diamides, amino acids, azomethines, oximes, crown ethers, phenanthroline derivatives, calixarenes, phenolic oximes, phosphonic acid, hydroxyquinolines (e.g., 8-hydroxyquinoline), P-diketones, and thioglycolamides.
  • the charge of the first charged polymer layer and the second charged polymer layer may be different from each other.
  • a second charged polymer layer can have an opposite charge (e.g., positive) to a charge of the first charged polymer layer (e.g., negative).
  • the functional groups may be characterized by methods such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X- ray photoelectron spectroscopy (XPS), or other suitable methods.
  • FTIR Fourier transform infrared spectroscopy
  • NMR nuclear magnetic resonance
  • XPS X- ray photoelectron spectroscopy
  • the polymers may be characterized by methods such as gel permeation chromatography (GPC), rheology, or other suitable methods in addition to the previously listed methods.
  • any of the one or more surfaces of the atomically thin active layer may be functionalized to enhance bonding with the charged polymer layers.
  • anchors may be present in the atomically thin active layer such that bonding with charged polymer layers is facilitated. Accordingly, these anchors may interact with the charged polymer layer, and, in some cases, may enhance the bonding between a charged polymer layer and an atomically thin active layer, such that disassembly or delamination of the charged polymer layer is prevented.
  • Some examples of anchors include metal oxides, metal halides, among others.
  • the above noted charged polymer layers may be formed in a number of ways depending on the specific embodiment. For example, in some embodiments, the charged polymer layers may be formed using interfacial polymerization.
  • some of the disclosure relates to fabricating atomically thin active layers with charged polymer layers, where such process may occur at different interfaces (e.g., liquid-solid, gas-liquid, liquid-liquid, among others).
  • Another aspect of the present disclosure relates atomically thin active layers having multilayered assemblies formed in a membrane, which may be also referred to as a layer-by-layer membrane where the separate polymer layers may be formed by the sequential exposure to different materials. Combinations of the above and other methods for forming the desired polymer layers may be used as the disclosure is not so limited.
  • each of the layers for the first polymer charged layer and the second polymer charged layer can have a thickness.
  • an average thickness of the first charged polymer layer and the second charged polymer is greater than or equal to 1 nm, greater than or equal to 5 nm, greater than or equal to 10 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 500 nm, or greater than or equal to 1 pm.
  • an average thickness of the first charged polymer layer and the second charged polymer is less than or equal to 1 pm, less than or equal to 500 nm, less than or equal to 100 nm, less than or equal to 50 nm, less than or equal to 10 nm, less than or equal to 5 nm, or less than or equal to 1 nm. Combinations of above-mentioned thickness ranges are possible. For example, an average thickness of the various separate charged polymer layers may be between or equal to 1 nm and 1 pm.
  • the charged polymers layers can be permeable to one or more desired species.
  • permeable used to describe a material, layer, or region where permeation of species may occur and may not interrupt the functionality of the membrane (e.g., completely inhibit transport by blocking selective pores).
  • the charged polymer layers are permeable.
  • the first charged polymer layer, the second charged polymer layer, and/or the bonded portion of the first charged polymer layer and the second charged polymer layer can be permeable to a desired target species while excluding other undesired . Permeability may allow the infiltration of species such as ions or small molecules through the layers.
  • the first charged polymer layer and/or the second charged polymer layer may comprise a polyelectrolyte layer.
  • Polyelectrolytes e.g., polycations, polyanions
  • moieties e.g., selective functional groups, polymer backbone
  • polyelectrolyte may include, but are not limited to polyallylamine hydrochloride, polydiallyldimethylammonium chloride, poly(methacryloyloxyethyltrimethylammonium chloride), polyethylenimine, chondroitin sulfate, poly(N-ethyl-4-vinylpyridinium), poly(4-vinylpyridine), polystyrene sulfonate, dextran sodium sulfate, sodium carboxymethyl cellulose, and/or poly(styrene-alt-maleic acid). Additional variations of similar polyelectrolytes are possible.
  • any of the charged polymer layers may not be a polyelectrolyte layer, in which case the polymer forming the layer may be polymer having a radical, a polymer having a polaron, an oxidized polymer, a reduced polymer, or other variations of charged polymers.
  • a charged polymer such as a charged polyelectrolyte, used in the various polymer layers disclosed herein may have a suitable molecular weight.
  • the polyelectrolyte can have a molecular weight that is greater than or equal to 500 Da, greater than or equal to 1,000 Da, greater than or equal to 5,000 Da, greater than or equal to 10,000 Da, greater than or equal to 50,000 Da, greater than or equal to 100,000 Da, greater than or equal to 150,000 Da, greater than or equal to 200,000 Da, greater than or equal to 250,000 Da, greater than or equal to 300,000 Da, greater than or equal to 350,000 Da, greater than or equal to 400,000 Da, greater than or equal to 450,000 Da, or greater than or equal to 500,000 Da.
  • the polyelectrolyte can have a molecular weight that is less than or equal to 500,000 Da, less than or equal to 450,000 Da, less than or equal to 400,000 Da, less than or equal to 350,000 Da, less than or equal to 300,000 Da, less than or equal to 250,000 Da, less than or equal to 200,000 Da, less than or equal to 150,000 Da, less than or equal to 100,000 Da, less than or equal to 50,000 Da, less than or equal to 10,000 Da, less than or equal to 5,000 Da, less than or equal to 1,000 Da, or less than or equal to 500 Da. Combinations of the values are possible (e.g., greater than or equal to 500 Da and less than or equal to 500,000 Da).
  • the molecular weight of the polyelectrolyte is greater than or equal to 1,000 Da and less than or equal to 100,000 Da.
  • a molecular weight may be measured using multi-angle light scattering (MALS) measurements.
  • MALS multi-angle light scattering
  • the charged polymer layers may also be functionalized to facilitate transport of one or more target species.
  • different functional groups with different selectivity relative to different ions may be present on the polymers of one or more of the charged polymer layers.
  • This may include, for example, chelating agents of other functional groups that have a higher selectivity towards certain species.
  • phenolic oximes are selective towards Cu 2+ but not to Fe 3+ ions.
  • selectivity may allow the development of membranes capable of separating species with distinguishing parameters.
  • Other properties such as size and charge may still play a role in the selectivity.
  • more than one property, including a selective affinity may be used to achieve selective separations.
  • a first charged polymer e.g., a polycation
  • a second charged polymer e.g., a polyanion
  • the size of the charged polymers may be larger than the pore size of selective polymers, such that any of the charged polymers may not completely diffuse to the other side prior to the formation of a charged polymer layer.
  • at least a portion of each charged polymer layer formed may bond the other through the inside of the selective pore.
  • the assembly of the charged polymer layers on the atomically thin active layers may be facilitated by electrostatic forces.
  • the polyelectrolyte layers may be electrostatically drawn towards the atomically thin active layer, which, as already discussed, may covalently or non- covalently bonded to the charged polymer layers.
  • this electrostatic-driven assembly may provide a quick assembly process (e.g., less than or equal to 30 minutes of exposure). It is to be understood that the present disclosure generally focuses enhancing the selectivity of membrane components, including a plurality of selective pores.
  • the first charged polymer layer (e.g., polycation) and the second charged polymer layer (e.g., polyanion) disposed or positioned on at least a portion of the atomically thin active layer (e.g., first surface, second surface) can form a membrane (e.g., defect-sealed membrane) where selective transport primarily occurs through selective pores.
  • a membrane e.g., defect-sealed membrane
  • a potential use of the membranes described in this disclosure involves a solvent that facilitates transport across the membrane.
  • the method may first comprise exposing the atomically thin active layer with the first charged polymer layer and the second charged polymer layer to a solvent that facilitates transport across the membrane.
  • the solvent may be, according to certain embodiments, an acid extractant or neutral extractant.
  • extractants include acid extractants such as Bis(2-ethylhexyl)phosphoric acid (D2EHPA), bis(2,4,4- trimethylpentyl)phosphinic acid (Cyanex 272), and Versatic Acid 10 (a mixture of CIO carboxylic acids) and neutral extractants such as Tri-n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (TOPO), and Cyanex 923 (a mixture of trialkyl phosphine oxides).
  • D2EHPA Bis(2-ethylhexyl)phosphoric acid
  • Cyanex 272 bis(2,4,4- trimethylpentyl)phosphinic acid
  • Versatic Acid 10 a mixture of CIO carboxylic acids
  • neutral extractants such as Tri-n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (TOPO), and Cyanex 923 (a mixture of trialkyl phosphine oxide
  • membranes with enhanced selectivity may be fabricated.
  • a method of separating ions with any of the membranes disclosed herein are possible. Some examples of ions that can be separated, including how selectivity is achieved, are described in more detail earlier herein.
  • the disclosed methods of manufacture, and the resulting membranes may be applied to any number of different applications.
  • some commercial applications of the described membranes include: separation of different ionic systems (e.g., recycling of metals from electronic items, recovering of metal ions from process leachates), water treatment and desalination (e.g., brackish water and seawater desalination, treatment of industrial water, removal of micropollutants, aqueous food processing); biomolecular separation (e.g., sterilization of API, hemodialysis); gas separation (CO2 capture from industrial sources, H2 separation from syn-gas, O2 concentration for medical applications).
  • separation of different ionic systems e.g., recycling of metals from electronic items, recovering of metal ions from process leachates
  • water treatment and desalination e.g., brackish water and seawater desalination, treatment of industrial water, removal of micropollutants, aqueous food processing
  • biomolecular separation e.g., steriliz
  • Some advantages of the disclosed membranes include: high permeance, the system retains the major advantage of using 2D materials as membranes and allows for high permeances; tunability, the self-assembled molecules can be optimized to tune pore size distributions to enable size-selective separations; selectivity, the self-assembled molecules can be functionalized to preferentially interact with one of the components being separated and allow for selective separation.
  • An atomically thin active layer can, for example, be a layer of graphene, which may be typically described as a one atom thick allotrope of carbon.
  • an atomically thin active layer may include multiple atomically thin active layers (e.g., 2, 5, 10 layers, etc.), while nonetheless having a thickness comparable to that of an atomically thin active layer.
  • an atomically thin active layer may have a thickness between 0.1 nm and 10 nm, or between 0.3 nm and 5 nm, or between 0.345 nm and 2 nm.
  • an atomically thin active layer comprising a single layer of graphene would be expected to have a thickness of approximately 0.345 nm.
  • layers may be stacked on one another and/or layers may be bonded to adjacent layers. In some cases, when multiple atomically thin active layers are grown, they may be bonded to one another as a result of the formation process.
  • an “atomically thin active layer” refers to a structure formed from one or more planar atomic layers of materials.
  • Atomically thin active layers also known as two- dimensional monolayers or two-dimensional topological materials, are crystalline materials composed of a single layer of atoms.
  • a layer of graphene is typically a one atom thick allotrope of carbon, though multiple layers may also be present.
  • atomically thin materials typically have strong chemical bonds within a plane or layer, but have relatively weaker bonds out of the plane with neighboring planes or layers. Therefore, atomically thin materials typically form sheets of material that may be a single atom thick, i.e.
  • an atomically thin active layer and/or material may be considered to be a sheet or layer of material including one or more adjacent crystal planes extending parallel to a face of the sheet or layer.
  • An atomically thin material may have a thickness corresponding to any appropriate number of crystal planes including sheets with a thickness corresponding to 1 atomic layer, or in some instances, a thickness that is less than or equal to 2, 3, 4, 5, or 10 atomic layers, or any other appropriate number of atomic layers.
  • an atomically thin active layer may have a thickness between 0.1 nm and 10 nm, between 0.3 nm and 5 nm, or between 0.345 nm and 2 nm.
  • the theoretical thickness of a sheet of graphene is 0.345 nm, and so an atomically thin active layer comprising a single layer of graphene would be expected to have a thickness of approximately 0.345 nm.
  • Atomically thin materials may also be referred to as ultra- strength materials and/or two-dimensional materials as well.
  • appropriate atomically thin materials that may be used to form an atomically thin active layer include, but are not limited to, graphene, hexagonal boron nitride, molybdenum sulfide, vanadium pentoxide, silicon, doped graphene, graphene oxide, hydrogenated graphene, fluorinated graphene, graphyne, MXenes, covalent organic frameworks, layered transition metal dichalcogenides (e.g., M0S2, TiS2, etc.), two dimensional oxides (e.g.
  • the methods described herein may be applied to the production of thicker non-atomically thin membrane materials such as graphene containing larger numbers of atomic layers, graphene oxide containing larger numbers of atomic layers, metal organic frameworks, thin-layer atomic layer deposition of metal oxides (AIO2, HfCh, etc.), zeolites, and other appropriate materials as well.
  • an atomically thin active layer may be disposed upon a porous substrate or other supporting porous structure that maintains the structural integrity of the membrane during use.
  • the porous substrate may be sufficiently porous so that molecules diffusing through the atomically thin active layer may then diffuse through the selective pores of the substrate.
  • a composite membrane may include an atomically thin active layer disposed on a corresponding substrate either directly or indirectly depending on the particular application.
  • Appropriate porous substrates may include track etched membranes. Nonetheless, the combined effective thickness of such a composite membrane may still be several times smaller than that of conventional membranes.
  • porous substrates include inorganic supports such as alumina, titanium, and zinc oxide and organic supports such as polyacrylonitrile (PAN), polyethersulfone (PES), polysulfones (PSf), poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polyetherimide (PEI), polyimide (PI), polyamide (PA), cellulose acetate (CA), and polyethylene (PE), and/or any other appropriate porous substrate capable of supporting an atomically thin active layer disposed thereon.
  • PAN polyacrylonitrile
  • PES polyethersulfone
  • PSf poly(vinylidene fluoride)
  • PVDF polytetrafluoroethylene
  • PEI polyetherimide
  • PI polyimide
  • PA polyamide
  • CA cellulose acetate
  • PE polyethylene
  • selective pores may be formed in an atomically thin active layer either prior to, or after, bonding the atomically thin active layer to a substrate.
  • various techniques may be applied to form pores in one or more atomically thin active layers, and these techniques may be applied before said one or more layers are disposed upon a substrate or after the layers are disposed upon a substrate.
  • pores may be formed in the layers as a group (e.g., when the layers are bonded to one another) and/or pores may be formed in the layers individually prior to stacking or bonding the layers together.
  • the plurality of selective pores may be formed in the atomically thin active layer either prior to, or after, transferring the atomically thin active layer to a porous substrate.
  • a substrate e.g., copper substrate
  • an atomically thin active layer e.g., graphene
  • gases such as ammonia or nitrogen may be added during synthesis to create pores during the chemical vapor deposition process.
  • the amorphous regions in the atomically thin active layer may contain a higher number of selective pores, which can also be used for filtration. Regardless of the manner in which the selective pores are created, after forming the selective pores in the one or more atomically thin active layers, the selective pores may be selectively etched to a preselected size. Examples of appropriate etchants for these materials include, but are not limited to, concentrated nitric acid, mixtures of potassium permanganate and sulfuric acid, hydrogen plasmas, and hydrogen peroxide.
  • Each selective pore of the plurality of the selective pores may have an initial average pore size.
  • the initial average pore size is herein referred to as the average pore size before depositing charged polymer layers.
  • the selective pores of the plurality of selective pores have an initial average pore size of greater than or equal to 0.1 nm, greater than or equal to 0.2 nm, greater than or equal to 0.3 nm, greater than or equal to 0.4 nm, greater than or equal to 0.5 nm, greater than or equal to 0.6 nm, greater than or equal to 0.8 nm, greater than or equal to 1 nm, greater than or equal to 2 nm, greater than or equal to 5 nm, greater than or equal to 10 nm, greater than or equal to 25 nm, greater than or equal to 40 nm, or greater than or equal to 50 nm.
  • the selective pores of the plurality of selective pores have an initial average pore size of less than or equal to 50 nm, less than or equal to 40 nm, less than or equal to 25 nm, less than or equal to 10 nm, less than or equal to 5 nm, less than or equal to 2 nm, less than or equal to 1 nm, less than or equal to 0.8 nm, less than or equal to 0.6 nm, less than or equal to 0.5 nm, less than or equal to 0.4 nm, less than or equal to 0.3 nm, less than or equal to 0.2 nm, or less than or equal to 0.1 nm.
  • the selective pores of the plurality of selective pores have an initial average pore size of greater than or equal to 0.5 nm and less than or equal to 1 nm).
  • Other combinations are also possible.
  • a fraction (e.g., 90%) of the plurality of selective pores may have a certain initial pore size range (e.g., greater than or equal to 0.1 nm and less than or equal to 1 nm).
  • One skilled in the art could use techniques such as electron microscopy (e.g., transmission electron microscopy, scanning electron microscopy) to measure pore size in addition to utilizing the teachings of the present disclosure to arrive at desired results.
  • the plurality of selective pores may have a size variance.
  • the variance of initial pore sizes of the plurality of selective pores is greater than or equal to 0.1 nm, greater than or equal to 0.2 nm, greater than or equal to 0.5 nm, greater than or equal to 1 nm, greater than or equal to 2 nm, greater than or equal to 5 nm, or greater than or equal to 10 nm.
  • the variance of initial pore sizes of the plurality of selective pores is less than or equal to 10 nm, less than or equal to 5 nm, less than or equal to 2 nm, less than or equal to 1 nm, less than or equal to 0.5 nm, less than or equal to 0.2 nm, or less than or equal to 0.1 nm. Combinations of the above-mentioned ranges are possible (e.g., greater than or equal to 0.1 nm and less than or equal to 10 nm).
  • the modified pore size of the plurality of selective pores may have a suitable length.
  • the average modified pore size of the plurality of selective pores is greater than or equal to 0.3 nm, greater than or equal to 0.4 nm, greater than or equal to 0.5 nm, greater than or equal to 0.6 nm, greater than or equal to 0.7 nm, greater than or equal to 0.8 nm, greater than or equal to 0.9 nm, or greater than or equal to 1 nm.
  • the plurality of selective pores may have an average modified pore size of less than or equal to 1 nm, less than or equal to 0.9 nm, less than or equal to 0.8 nm, less than or equal to 0.7 nm, less than or equal to 0.6 nm, less than or equal to 0.5 nm, less than or equal to 0.4 nm, or less than or equal to 0.3 nm.
  • the deposited material may affect the initial average pore size of the plurality of selective pores and have an average modified pore size of greater than or equal to 0.3 nm and less than or equal to 1 nm
  • the deposited material may affect the initial average pore size of the plurality of selective pores and have an average modified pore size of greater than or equal to 0.5 nm and less than or equal to 0.8 nm).
  • Other combinations are also possible.
  • the material deposited adjacent to and/or inside any selective pore within the plurality of selective pores may affect the variance of pore sizes.
  • a given membrane may have a variance in initial pore size that is larger than a variance in modified pore size.
  • the variance of the modified pore size of selective pores is greater than or equal to 0.05 nm, greater than or equal to 0.1 nm, greater than or equal to 0.2 nm, greater than or equal to 0.5 nm, greater than or equal to 1 nm, or greater than or equal to 2 nm.
  • the variance of the modified pore size is less than or equal to 2 nm, less than or equal to 1 nm, less than or equal to 0.5 nm, less than or equal to 0.2 nm, less than or equal to 0.1 nm, or less than or equal to 0.05 nm. Combinations of the above-recited ranges are possible (e.g., greater than or equal to 0.05 nm and less than or equal to 2 nm). Without wishing to be bound by theory, a smaller selective pore size variance results in better membrane selectivity and performance, as compared to a membrane with a larger pore size variance.
  • the present disclosure focuses on manufacturing membranes with improve selectivity and performance and related methods.
  • the membranes disclosed herein may include defects.
  • methods for sealing defects of atomically thin active layers may also be used.
  • the membranes described herein may have tears, ruptures, deformations, leakages, and/or other defects according to certain embodiments. Some defects may occur as a result of being subject to processing, transporting, among other things.
  • the systems and/or methods described herein may seal, repair, and/or alleviate the effects of having defects, such that membranes can be substantially defect-free and the selective pores may primarily dictate the selective transport of species.
  • the defects of the atomically thin active layer may have a size that is greater than a size of the selective pores.
  • the average size of defects is greater than or equal to 10 nm, greater than or equal to 15 nm, greater than or equal to 20 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 500 nm, greater than or equal to 1 micrometer, or greater than or equal to 10 micrometers.
  • the average size of defects is less than or equal to 10 micrometers, less than or equal to 1 micrometer, less than or equal to 500 nm, less than or equal to 100 nm, less than or equal to 50 nm, less than or equal to 20 nm, less than or equal to 15 nm, or less than or equal to 10 nm. Combinations of the above recited ranges are also possible.
  • the selective pores and defects disclosed herein may be viewed as separate populations of openings formed in the atomically thin active layers with different sizes and distributions. Additionally, in some embodiments, the defects may also be sealed to substantially prevent passage of material therethrough.
  • the charged polymer layers may have a selective affinity that is pH dependent.
  • modifying a pH of a solution may be used to selectively permit or prevent passage of a target species across the membranes disclosed herein.
  • Selective affinity is herein referred to as the ability to find species (e.g., ions, small molecules).
  • the selective functional groups of the charged polymer layers e.g., chelating agents on a first charged polymer layer or second charged polymer layer
  • the selective functional groups can selectively bind to species under certain conditions, such as a suitable pH, for example.
  • the selective functional groups are configured to bind to species such as ions in acidic medium.
  • the acidic medium where the selective functional groups are configured to bind species has a pH of greater than or equal to 1, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 3.5, greater than or equal to 4, or greater than or equal to
  • the medium where the selective functional groups can bind to species has a pH of less than or equal to 4.5, less than or equal to 4, less than or equal to
  • the medium where ions are configured to bind the selective functional groups can be neutral or basic.
  • certain selective functional groups may bind to ions more efficiently or selectively at a given pH.
  • the selective functional groups of the charged polymer layers can have selectivity towards certain species.
  • the selectivity can be based on ionic size, where the diameter of the ion may dictate the size.
  • the ions may have a hydrated diameter that may impact its size.
  • Certain ions may have a charge or a valency, where the charge of the ions may be a parameter used to achieve selectivity with the membranes disclosure herein.
  • the valency of some ions may be monovalent, divalent, trivalent, or tetraval ent.
  • Some examples of ions that have a different valency include alkali metal ions (Li + , Na + , K + , Rb + ), alkaline metal ions (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ), and rare earth ions (Nd 3+ and Dy 3+ ).
  • LiCl, NaCl, KC1 and RbCl are example of salts that share the same anion but have a different cation, which the present disclosure may be used to achieve selectivity between these cations.
  • some ions may have a tendency to bind to certain functional groups and may not follow a specific trend.
  • certain functional groups may selectively bind to certain ions (e.g., diamides may selectively bind to lanthanides).
  • the selectivitity of the selective functional groups may be towards certain organic compounds (e.g. organic azo dyes such as Allura Red AC).
  • an atomically thin active layer can have a plurality of pores.
  • atomically thin active layer 102 has selective pore 104 of a plurality of selective pores that extend through atomically thin active layer 102.
  • Atomically thin active layer 102 may have first surface 106 and second surface 108 located opposite from first surface 106 with selective pore 104 extending therebetween.
  • first charged polymer layer 110 is disposed on first surface 106 and second charged polymer layer 112 is disposed on second surface 108.
  • the charged polymers layers e.g., first charged polymer layer, second charged polymer layer
  • the charged polymer layers disposed on the atomically thin active layer may provide some selectivity to the plurality of selective pores.
  • selective pore 104 of a plurality of selective pores is partially covered by first charged polymer layer 110 and second charged polymer layer 112.
  • either or both of the charged polymer layers can be permeable (e.g., permeable to ions).
  • first charged polymer layer 110 and second charged polymer layer 112 may be bonded to each other through at least a portion of filled selective pore 114 of the plurality of selective pores, such that at least a portion of each or either of first charged polymer layer 110 and second charged polymer layer 112 is present inside at least a portion of filled selective pore 114 of the plurality of selective pores.
  • filled selective pore 114 can have at least a portion of first charged polymer layer 110 and/or at least a portion of second charged polymer layer 112 inside filled selective pore 114, where such selective pore is permeable.
  • certain parameters can impact the ability of bonding the first charged polymer and the second charged polymer through the plurality of selective pores, such as, for example, the average initial pore size of the plurality of selective pores, properties of charged polymers (e.g., molecular weight, hydrodynamic radius of charged polymers, dispensability), type or extent of bonding between the atomically thin active layer and any of the charged polymer layers, among others.
  • properties of charged polymers e.g., molecular weight, hydrodynamic radius of charged polymers, dispensability
  • type or extent of bonding between the atomically thin active layer and any of the charged polymer layers among others.
  • the charged polymer layers are disposed on the atomically thin active layer, where such atomically thin active layer can have functional groups that may facilitate the assembly, deposition, or orientation of the charged polymer layers.
  • the selective membrane 200 includes an atomically thin active layer 202 with a functionalized surface with a plurality of functional groups 210 attached thereto.
  • the functional groups 210 may be configured to bond with the first charged polymer layer 204 and the second charged polymer layer 206.
  • the charged polymer layers may also have selective functional groups configured to selectively bind and/or pass different species.
  • these selective functional groups may be configured to selectively bind to a desired species, thus improving selectivity to some selective membranes.
  • membrane 220 having atomically thin active layer 222 with first charged polymer layer 224 and second charged polymer layer 226 attached thereto, where first charged polymer layer 224 can have selective functional group 228 and second charged polymer layer 226 can have selective functional group 230.
  • the selective functional groups are configured to bind to species, such as ions.
  • Fig. 2C schematically shows a membrane 240 with an atomically thin active layer 242 with a selective pore 243 of a plurality of selective pores formed therein.
  • the same figure shows first charged polymer layer 244 and second charged polymer layer 248 disposed on atomically thin active layer 242, where at least a portion of first charged polymer layer 244 and second charged polymer layer 248 is disposed inside selective pore 243.
  • first charged polymer layer 244 and second charged polymer layer 248 are bonded through selective pore 243.
  • selective pore 243 can have selective functional group 246 of first charged polymer layer 244 and selective functional group 250 of second charged polymer layer 248.
  • the selective functional groups inside the plurality of selective pores are configured to bind to a target species when it is present within and/or adjacent to the pore 243 where such binding can be selective to certain species to help prevent passage of the target species through the selective pores.
  • the charged polymer layers may not be positioned inside the plurality of selective pores.
  • the charged polymer layers e.g., first charged polymer layer, second charged polymer layer
  • the charged polymer layers covering at least a portion of the pore may provide some selectivity considering that the charged polymer layers may be permeable.
  • a membrane may be positioned on a porous substrate. For example, as schematically shown in Fig.
  • membrane 300 has atomically thin active layer between first charged polymer layer 304 and second charged polymer layer 306, where second charged polymer layer 306 is adjacent to or otherwise disposed on a porous support 312.
  • first charged polymer layer 304 can be disposed on first surface 308 and second charged polymer layer 306 can be disposed on second surface 310 of atomically thin active layer 302. Nevertheless, in Fig.
  • first charged polymer layer 304 can be adjacent to second changed polymer layer 306, such that a multi-layer arrangement of alternating charged polymer layers with alternating charges may be provided between the porous support 312 and the atomically thin active layer 302.
  • the materials of the first and second charged polymer layers 304 and 306 may be used to form the alternating arrangement of different charged polymer layers.
  • the multilayer arrangement is not limited a first surface of the atomically thin active layer, it can also be present in a second surface of such layer or in both surfaces.
  • second charged polymer layer 406 can be formed on porous substrate 408, via deposition methods (e.g., spin coating, drop casting, blade coating, spray coating), and atomically thin active layer 402 is positioned or disposed on support substrate 410.
  • the support substrate can be a metal block (e.g., copper block), base layer, support layer, or the like, and it may be useful in providing support to atomically thin active layers or other membrane components.
  • atomically thin active layer 402 is transferred to second charged polymer layer 406, such that second charged polymer layer 406 is disposed on or adjacent to atomically thin active layer 402.
  • Such transfer step of atomically thin active layer 402 to support substrate 408 may be achieved through certain transfer methods (e.g., lamination, dry transfer method, liquid transfer method, polymer-assisted transfer method, nanoporous-carbon-assisted transfer).
  • the plurality of selective pores may be formed in atomically thin active layer 402 either prior to, or after, transferring atomically thin active layer 402 to porous substrate 408 with second charged polymer 406 through any of various methods described (e.g., chemical etching).
  • second polymer layer can be disposed on atomically thin active layer 402 via similar deposition methods (e.g., spin coating, drop casting, blade coating, spray coating) as first charged polymer 406.
  • Fig. 4B shows a schematic diagram for fabricating the same.
  • a similar process to that described in Fig. 4A may be followed for the overall formation and transfer process.
  • the method may include the formation of a plurality of alternating charged polymer layers disposed between the atomically thin active layer 402 and the porous support 408.
  • second charged polymer layer 456 can be formed on porous substrate 458, whereas atomically thin active layer 452 is positioned on support substrate 460.
  • one or more charged polymer layers of an alternating type (e.g., first charged polymer followed by second charged polymer) of charge polymer are formed by having first charged polymer layer 454 positioned on second charged polymer layer 456 that is disposed on porous substrate 258 and another first charged polymer layer 454 is positioned on second charged polymer layer 456 on atomically thin active layer 452, and another layer of second polymer charger layer 456 is deposited on first charged polymer layer 454 of porous support 458. Then, first charged polymer layer 454 of support substrate 460, without such substrate, is transferred to second charged polymer layer 456 of porous support 458.
  • first charged polymer layer 454 of support substrate 460 without such substrate
  • first charged polymer layer 454 can be deposited on an uncovered surface of atomically thin active layer 452, such that first charged polymer layer 454 is the uppermost layer and atomically thin active layer 452 has a different type of polymer in a different surface.
  • one or more layers of first charged polymer layer and/or second charged polymer layers can be deposited on an outer first charged polymer layer, such that the first charged polymer layer and the second charged polymer layer are arranged between each other.
  • Fig. 5 depicts a generalized flow diagram for forming a membrane. Any of the steps described in Fig. 5 are applicable to either or both of Figs. 4A and 4B.
  • Step 500 describes form an atomically thin active layer on a support substrate.
  • Step 502 describes form selective pores in the atomically thin active layer, as described elsewhere in the present disclosure in more detail.
  • Step 504 describes depositing one or more polymer layers including a first charged polymer layer disposed on a porous substrate, which, in some embodiments, can be a plurality of alternating polymer layers. The first charged polymer layer may be an upper most layer of the structure in instances where multiple layers are used.
  • step 506 transfer atomically thin active layer to first charged polymer layer.
  • second charged polymer layer may be deposited onto a surface of the atomically thin active layer opposite from the first charged polymer layer as described previously above.
  • portions of the first and second charged polymer layers may bind to each other through the selective pores of the atomically thin active layer as previously described above.
  • the current disclosure helps in enhancing selective separations through atomically thin active layers by using self-assembled molecules on either side of the atomically thin layer. These molecules can then be optimized to provide selective ionic separations by (1) varying pore size distributions on the basis of the size of the self-assembled molecules and (2) functionalizing with functional groups that selectively interact with one of the ions. It is demonstrated for separating alkali, alkaline from rare earth elements. Selectivity is also demonstrated between ions of the same charge (e.g, Li + and K + ). The method can be extended to other separation ranging from biomolecule separations, dialysis, organic solvent nanofiltration and gas separations.
  • Positively and negatively charged polyelectrolytes are introduced on either side of the nanoporous graphene membrane and are allowed to assemble across the interface, through the created pores. These molecules selectively assemble over the larger pores, and can seal defects.
  • polyelectrolyte assembly over largely non-selective pores is shown not only to reduce the transport of larger species (e.g., Nd 3+ and Dy 3+ ) as expected from sealing of non-selective pores, but also to allow the membrane to provide selective transport between these ions through these larger non-selective pores.
  • the transport through the membrane with polyelectrolyte assembly shows behaviors that depart from size and charge selectivity; thus, self- assembly of molecules over non-selective pores imparts selectivity in a manner that depends on the characteristics of the self-assembled molecules.
  • Graphene was transferred on a polyimide track etched membrane support (PI 20 nm) using a PMMA-assisted wet transfer method. After the transfer, atomic layer deposition equipment was used to deposit Hafinia (HfCh). The operating temperature was set to 130 °C, and 5 nm of film was deposited. This was done to make sure that the initial nanoporous atomically thin membrane that we start with demonstrated some selectivity. Pores were created in this membrane using 02 plasma etching. The membrane was put in Harrick Plasma Cleaner and exposed to 02 plasma at low voltages for 10 s, at an oxygen pressure of 0.5 Torr.
  • the solution was fed into the feed side of the diffusion cell to react with the graphene layer.
  • the performance of the membrane was tested in a diffusion cell where we introduced 10 ions in the feed side, including alkali metal ions (Li + , Na + , K + , Rb + ), alkaline metal ions (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) and rare earth ions (Nd 3+ and Dy 3+ ) with a base salt solution.
  • alkali metal ions Li + , Na + , K + , Rb +
  • alkaline metal ions Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+
  • rare earth ions Na 3+ and Dy 3+
  • the feed solution contained ImM LiCl, NaCl, KC1 and RbCl; lOOuM MgCh, CaCh, BaCh and SrCh; lOuM NdCh and DyCh in a background of 80mM CsCl and ImM HC1.
  • the background salt is added to ensure that the transport being measured is governed by diffusion and not by electrostatic interactions.
  • the permeate solution contains just the background of 80mM CsCl and ImM HC1.
  • the base salt solution was introduced on the permeate side too. Over time, the concentrations of all elements were measured in the feed and the permeate solutions using Inductively Charged Plasma Mass Spectroscopy (ICP-MS).
  • ICP-MS Inductively Charged Plasma Mass Spectroscopy
  • Polyelectrolytes assembly was then carried out on the graphene interface. Simultaneously exposing opposite surfaces of nanoporous graphene to oppositely charged polyelectrolytes results in their self-assembly across the atomically thin layer, where selfassembly is favored across pores above a certain size.
  • the diffusion cell was then rinsed four times with DI water. It is seen that they selectively assemble over the larger pores and hence block transport through them. The transport of the ions through this membrane was also tested. A significant enhancement was observed in the performance of the membrane with selectivity of over 130 observed between the smallest and the largest ions. Much of the selectivity can be attributed to tuning of the pore size in the 7-9 A range.
  • FIG. 6A permeance of Dy 3+ and Rb + with graphene membrane with atomic layer deposition and pore created using oxygen plasma and polyelectrolyte assembly (PEA) on the same membrane.
  • Fig. 6B shows selectivity of different ions with respect to Dy 3+ represented as the line graphs, without PEA and with PEA. The hydrated diameters of these ions are represented as bar graphs with the right y-axis.
  • Table 1 Inter-ion selectivity chart. The selectivity is given as T’ /X ⁇ ' where M n+ is the ion in row and X 7 is the ion in the column. The selectivity values between ions of the same charge are boxed together.
  • Fig. 7A permeance of Dy 3+ and Rb + with bare polyimide support with polyelectrolyte assembled and polyelectrolyte assembled on graphene membrane.
  • Fig. 7B selectivity of different ions with respect to Dy 3+ represented as the line graphs, on support membrane with PEA and on graphene membrane with PEA. The hydrated diameters of these ions are represented as bar graphs with the right y-axis.
  • This example describes the effect of different methods for creating pores in atomically thin active layers.
  • the effect of the pore creation process was tested, by comparing two membranes with the same amount of atomic layer deposition cycles and the only difference being the pore creation process.
  • O2 plasma treatment as described above was used to create the pores.
  • pores were created using focused ion beam (FIB) followed by the chemical reaction with potassium permanganate solution (KMnCh).
  • FIB focused ion beam
  • KMnCh potassium permanganate solution
  • the dosage of FIB was approximately 6 X 10 12 ions cm' 2 , and the incident angle of the beam was set to 52°.
  • KMnCh solution was prepared with 1.875 mM KMnCh in 6.25 wt% H2SO4 solution.
  • pore creation method also affects the selectivity boost that can be achieved using PEA as seen in Figs. 8 A and 8B.
  • pore creation methods can also be varied to change the way PEA interacts with the atomically thin layer and hence with the transport of ions.
  • polyelectrolyte system demonstrated using polyallylamine and polyacrylic acid can be varied and tuned for specific applications in the following ways:
  • polyelectrolytes can be used which would decide which pores on which these molecules self-assemble, typically smaller molecular weight polyelectrolytes would prefer smaller pores. Using this the pore size distribution could be tuned to achieve selectivity.
  • Other polyelectrolyte systems used for layer by layer literature can be used in this application as well, including polycations like PAH, PDADMAC, PDMC, branched- PEI, CS, QVP-C2 and P4VP and polyanions like PSS, DSS, CMCNa, PSaMA, also known as polyallylamine hydrochloride, polydiallyldimethylammonium chloride, poly(methacryloyloxy ethyltrimethylammonium chloride), branched-polyethylenimine, chondroitin sulfate, poly(N-ethyl-4-vinylpyridinium), poly(4-vinylpyridine), polystyrene sulfonate, dextran
  • Add functional groups that selectively interact with certain ions can be added to the polyelectrolyte or any general self-assembling molecules which preferentially interact with one of the components that we are trying to separate - in the given case being ions.
  • phenolic oximes are selective towards Cu 2+ as opposed to Fe 3+ ions
  • phosphonic acid reagents can distinguish between Zn, Cu, Mn, Ni ions.
  • 8- hydroxyquinolines form stable complexes with di-, tri- and tetra- valent cations.
  • P-diketones can also be used. Addition of chelating agents to these assembled molecules could also help tune selectivity.
  • Amides, amino acids, azomethines, oximes, crown ethers, phenanthroline derivatives, calixarenes are chelating agents that can be used.
  • Diamides containing ether groups are used for the extraction of lanthanides, thioglycol amides are used for extraction of noble metals. Similar to solvent extraction processes, functional groups that have affinity to certain ions can facilitate their transport across the atomically thin layer selfassembled molecules that otherwise hinder transport.
  • Common solvent used for extraction and can be used during self-assembly include acid extractants such as Bis(2-ethylhexyl)phosphoric acid (D2EHPA), bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), and Versatic Acid 10 (a mixture of CIO carboxylic acids) and neutral extractants such as Tri-n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (TOPO), and Cyanex 923 (a mixture of trialkyl phosphine oxides).
  • acid extractants such as Bis(2-ethylhexyl)phosphoric acid (D2EHPA), bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272)
  • Versatic Acid 10 a mixture of CIO carboxylic acids
  • neutral extractants such as Tri-n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (
  • the interaction of PEA with the pore edges of graphene pores can be tuned by using different pore creation methods and can change the transport of ions through them.
  • the interaction of the polyelectrolyte with the graphene surface can be tuned by functionalizing (e.g., with oxygen plasma) or coating the graphene surface with ALD or other methods.
  • the surface of a porous support membrane is first functionalized with a polyelectrolyte.
  • a polyelectrolyte Various methods known in the literature may be used for this purpose, including layer-by-layer assembly, grafting, or adsorption.
  • a nanoporous graphene layer is then deposited on top of the membrane, on the polyelectrolyte functionalized surface.
  • Various methods including lamination, polymer-assisted transfer, or direct transfer may be used for this purpose.
  • the polyelectrolyte on the membrane may contain functional groups that bind to the graphene layer (e.g., pyrene) or react with the graphene layer (e.g., diazonium).
  • pores may be created in the graphene layer after it is deposited on the polyelectrolyte-coated membrane support.
  • the pores in the graphene layer may range in size between 0.3 nm to preferably 50 nm or less to allow for the molecules to self-assemble without freely passing through the graphene layer.
  • the graphene will have a significant fraction of pores above 0.5 nm in size to allow self-assembly (e.g., >10% of pores between 0.3 nm or above being >0.5 nm in size).
  • 90% of the pores range in size from 0.1-1 nm, in some cases between 0.1-3 nm, in some cases between 0.1-10 nm, and in some cases between 0.1-50 nm.
  • a polyelectrolyte of the opposite charge is deposited on the graphene using methods such as exposing the graphene surface to a solution containing the polyelectrolyte.
  • graphene may be replaced by other nanoporous atomically thin layers, including various derivatives of graphene (e.g., hydrogenated graphene, oxygenated graphene, fluorinated graphene, etc.) as well as materials such as hexagonal boron nitride, molybdenum disulfide, and others.
  • various derivatives of graphene e.g., hydrogenated graphene, oxygenated graphene, fluorinated graphene, etc.
  • materials such as hexagonal boron nitride, molybdenum disulfide, and others.
  • the self-assembled molecules may be polyelectrolytes or other kinds of molecules that self-assemble. These interactions between the molecules could be covalent or non-covalent.
  • the self-assembled molecules may also have covalent or non-covalent interactions with the atomically thin layer.
  • block copolymers consisting of a polyelectrolyte block and another block that confers fouling resistance e.g., zwitterionic polymer or polyethylene glycol blocks.
  • hydrophobic interactions rather than charge interactions may be used for self-assembly.
  • Such systems include surfactants, hydrophobic polymers, block copolymers consisting of hydrophobic and hydrophilic blocks, alkane-based self-assembled monolayers, and others. These systems may have functional groups including those listed above for polyelectrolytes, and the membranes may be fabricated using similar or other methods.
  • Fig. 8 A permeance of Dy 3+ and Rb + with graphene membrane with atomic layer deposition and pore created using oxygen plasma and PEA and a graphene membrane with ALD and pore creation using FIB and KMnCh chemical etching and PEA.
  • Fig. 8B selectivity of different ions with respect to Dy 3+ represented as the line graphs, O2 plasma etch method of pore creation and FIB + KMnCh method of pore creation.
  • the hydrated diameters of these ions are represented as bar graphs with the right y-axis.
  • Figs. 9A and 9B effect of different polyelectrolyte assembly on a graphene membrane with atomic layer deposition and pores created using oxygen plasma, using polyallylamine hydrochloride (PAH) as the polycation and polystyrene sulphonic acid (PSS) as anion.
  • PAH polyallylamine hydrochloride
  • PSS polystyrene sulphonic acid
  • the hydrated diameters of these ions is represented as bar graphs with the right y-axis.
  • Figs. 10A and 10B show the effect of dual poly electrolyte assembly on a graphene membrane with atomic layer deposition and pores created using oxygen plasma, using polyallylamine hydrochloride (PAH) as the polycation and polystyrene sulphonic acid (PSS) and polyacrylic acid (PAA) as anion.
  • the hydrated diameters of these ions is represented as bar graphs with the right y-axis.
  • Fig. 11 shows selectivity of other rare earths with respect to Dysprosium. Note that hydrated diameter of these elements is Yttrium (Y, 9 A), Lanthanum (La, 9.04 A), Cerium (Ce, 9.04 A), Neodymium (Nd, 9.06 A), Dysprosium (Y, 9.3 A).
  • Embodiment 1 A membrane comprising nanoporous atomically thin layers, selected from the group consisting of graphene, hydrogenated graphene, oxygenated graphene, fluorinated graphene, hexagonal boron nitride, molybdenum disulfide, wherein the atomically thin layer has a pore size of 0.1 to 50 nm, and wherein the atomically thin layer is treated with polyelectrolytes, wherein the polyelectrolytes are self-assembling molecules that modify the pore size; and a polyimide track etched membrane support.
  • nanoporous atomically thin layers selected from the group consisting of graphene, hydrogenated graphene, oxygenated graphene, fluorinated graphene, hexagonal boron nitride, molybdenum disulfide, wherein the atomically thin layer has a pore size of 0.1 to 50 nm, and wherein the atomically thin layer is treated with polyelectrolytes, wherein the
  • Embodiment 2 The membrane of embodiment 1, wherein the atomically thin layer comprises graphene.
  • Embodiment 3 The membrane of embodiment 1, wherein the atomically thin layer is functionalized with oxygen plasma or coated with ALD.
  • Embodiment 4 The membrane of embodiment 1, wherein the poly electrolytes comprise a compound selected from the group consisting of block copolymers consisting of a polyelectrolyte block and another block that confers fouling resistance surfactants, hydrophobic polymers, block copolymers consisting of hydrophobic and hydrophilic blocks, and alkane- based self-assembled monolayers.
  • Embodiment 5. The membrane of embodiment 1, the poly electrolytes comprise one or more compounds selected from the group that consists of PAH, PDADMAC, PDMC, branched- PEI, CS, QVP-C2 and P4VP and polyanions like PSS, DSS, CMCNa, and PSaMA.
  • Embodiment 6 The membrane of any one of embodiments 4-5, wherein the polyelectrolytes further comprise functional groups that interact with certain ions.
  • Embodiment 7 The membrane of embodiment 6, wherein the functional groups comprise chelating agents.
  • Embodiment 8 The membrane of embodiment 1, wherein the poly electrolytes bind to the graphene layer.
  • Embodiment 9 The membrane of embodiment 8, wherein the polyelectrolytes comprise a pyrene.
  • Embodiment 10 The membrane of embodiment 1, wherein the poly electrolytes react with the graphene layer.
  • Embodiment 11 The membrane of embodiment 10, wherein the poly electrolytes comprise a di azonium.
  • Embodiment 12 The membrane of embodiment 4, wherein the block copolymers comprise zwitterionic polymer or polyethylene glycol blocks.
  • Embodiment 13 The membrane of embodiment 1, wherein the nanoporous atomically thin layers comprise 90% of the pores range in size from 0.1-1 nm.
  • Embodiment 14 The membrane of embodiment 1, wherein the nanoporous atomically thin layers have two sides, and wherein the polyelectrolytes used to treat one side differ from the polyelectrolytes used to treat the other side.
  • Embodiment 15 A method of fabricating a membrane, the method comprising: transferring the nanoporous atomically thin layers on a polyimide track etched membrane support to produce a membrane surface; deposit Hafnia (HfCh) on the membrane surface; creating pores on the membrane; introducing polyelectrolytes on both sides of the nanoporous atomically thin layers; and rinsing to remove excess polyelectrolytes.
  • HfCh Hafnia
  • Embodiment 16 The method of embodiment 15, wherein transferring the nanoporous atomically thin layers uses a PMMA-assisted wet transfer.
  • Embodiment 17 The method of embodiment 15, wherein pores are created by focused ion beam followed by reaction with potassium permanganate solution (KMnCh) or by O2 plasma etching.
  • KnCh potassium permanganate solution
  • Embodiment 18 A method of separating ions using the membrane of any of the preceding embodiments is described.
  • Embodiment 19 The method of embodiment 18, wherein the ions are inorganic ions.
  • Embodiment 20 The method of embodiment 18, wherein the ions are metallic ions.
  • Embodiment 21 The method of embodiment 18, wherein the ions are of the same charge.
  • Embodiment 22 The method of embodiment 18, wherein the ions are species less than 3 A apart in size.
  • a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
  • the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
  • This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified.
  • “at least one of A and B” can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
  • embodiments may be embodied as a method, of which various examples have been described.
  • the acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and/or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention se rapporte de manière générale aux molécules à auto-assemblage sur des couches actives atomiquement minces de membranes destinées à être utilisées dans des séparations sélectives. Dans un mode de réalisation, une membrane comprend une couche active atomiquement mince présentant une pluralité de pores sélectifs, une première couche de polymères chargés et une seconde couche de polymères chargés étant disposées sur des surfaces opposées de la couche active atomiquement mince. Dans un autre mode de réalisation, la couche active atomiquement mince est liée de manière covalente ou non covalente aux couches de polymères chargés. Dans encore un autre mode de réalisation, des groupes fonctionnels sélectifs sur les couches de polymères chargés sont conçus pour lier sélectivement des ions.
PCT/US2024/054838 2023-11-07 2024-11-07 Molécules à auto-assemblage sur des couches actives atomiquement minces Pending WO2025101687A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20200001245A1 (en) * 2018-06-28 2020-01-02 Massachusetts Institute Of Technology Coatings to improve the selectivity of atomically thin membranes
US20230138828A1 (en) * 2021-10-28 2023-05-04 Korea Institute Of Geoscience And Mineral Resources Selective recovery method of vanadium and cesium from waste sulfuric acid vanadium catalyst, and high-quality vanadium aqueous solution and cesium alum produced thereby

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20200001245A1 (en) * 2018-06-28 2020-01-02 Massachusetts Institute Of Technology Coatings to improve the selectivity of atomically thin membranes
US20230138828A1 (en) * 2021-10-28 2023-05-04 Korea Institute Of Geoscience And Mineral Resources Selective recovery method of vanadium and cesium from waste sulfuric acid vanadium catalyst, and high-quality vanadium aqueous solution and cesium alum produced thereby

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