Systems and methods for conductive membrane separation - Patents.com

Abstract

The present disclosure relates to systems and methods for conductive membrane separation from a mixed solution via membrane nanofiltration, electrofiltration, or electroextraction by generating an electric field across a membrane filter, holding the membrane filter at a constant potential, or passing a constant current through the membrane filter; feeding the mixed solution through a membrane nanofilter system; and separating components from the mixed solution into a permeate solution.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 213,085, filed June 21, 2021, the contents of which are incorporated by reference in their entirety herein. [Technical field]

[0002] The present invention relates generally to the field of conductive membrane separations, and more specifically to novel and useful systems and methods for conductive membrane-based ion separations. [Background technology]

[0003] As battery technology has become essential to modern society, there is a rapidly growing need to recycle batteries, battery components, and critical battery materials. Of particular importance are lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni). Current methods commonly involve grinding critical battery components (such as anodes and cathodes) into "black mass", exposing them to strong acids (such as H2SO4 or HCl) to leach the black mass, and then adding neutralizing agents (such as sodium compounds such as sodium carbonate and sodium hydroxide) to precipitate valuable materials. Solvent extraction and thermal crystallization are also common process steps that allow further separation and purification of valuable materials.

[0004] While these methods are useful, they are not optimal in terms of capital costs, operating costs, and environmental impact. Furthermore, the use of chemical precipitation techniques inevitably results in contamination of the black mass due to residual sodium and other chemicals, making lithium extraction difficult. Thus, there is a need in the field of hydrometallurgical battery recycling to create new and useful systems and methods for low-cost, environmentally sustainable extraction of key materials that minimizes chemical precipitation, thermal crystallization, and solvent exchange. The present invention provides such a new and useful system and method. Summary of the Invention

[0005] One aspect of the present disclosure is a system for conductive membrane separation, including a membrane filter having a nanoporous structure, an electrical contact in contact with the membrane filter, and a counter electrode on the upper surface of the membrane electrode. The membrane filter and the counter electrode via the electrical contact are configured to generate an electric field between the membrane filter and the counter electrode, to hold the membrane filter at a constant potential or to pass a constant current through the membrane filter. The membrane filter is configured to separate components from a mixed solution into a permeate solution.

[0006] In some embodiments, the system can be used in a hydrometallurgical separation process. In some embodiments, the mixed solution includes a black mass leachate. For example, the components of the mixed solution can be selected from the group consisting of Co, Ni, Al, Mn, Fe, Li, Cu, Ag, Zn, ions thereof, or mixtures thereof. The mixed solution can include an acid and have a pH less than 4.0. In some examples, the acid is H2SO4. The system can be configured to recycle up to 50% of the acid. In some embodiments, Li is a component separated in the permeate solution. In some embodiments, components not included in the permeate solution exit the system in a retentate solution. The system can be configured to recycle the retentate solution. In other embodiments, the retentate solution can be passed through another membrane filter to separate one or more additional components of the mixed solution. In one embodiment of the present disclosure, the membrane filter includes silicon. The membrane filter can have a pore size ranging from 1 nm to 500 nm, 1 nm to 1,000 nm, or 500 nm to 1,000 nm.

[0007] The system can include a membrane filter in a cross-flow or dead-end configuration. In some examples, a flow-through configuration can be used with electroextraction, where components are not rejected at the membrane surface (i.e., all flow through), but the target components are selectively immobilized within the membrane filter pores via electrochemical reduction or oxidation. The system can further include a pressure cell configured to accommodate the membrane filter and a counter electrode. The pressure cell can further include an opening configured to receive an electrical contact. The pressure cell can be operable at pressures up to 3000 psi. In various embodiments, the system can include modules for size filtration, charge filtration, electro-filtration, electro-extraction, or combinations thereof. In some embodiments, the system is configured for electrofiltration, and an electric field is applied between the membrane filter and the counter electrode. In this embodiment, the membrane filter has a pore size of 1 nm to 10 nm, 1 nm to 100 nm, 10 nm to 50 nm, or 50 nm to 100 nm, and the system is configured to operate at a pressure of more than 700 psi. In other embodiments, the system is configured for electroextraction, and the membrane filter is held at a constant potential or a constant current is passed through the membrane filter. For example, the pore walls may provide a current to components (e.g., ions) in close proximity in the mixed solution, resulting in the reduction of the ions. In this embodiment, the membrane filter has a pore size of 50 nm to 100 nm, 100 nm to 500 nm, or 500 nm to 1,000 nm, and the system is configured to operate at a pressure of less than 500 psi. In some embodiments, the system may be configured for size- and charge-selective filtration.

[0008] In some embodiments of the present disclosure, the system is in a cross-flow configuration. In various embodiments, the system may include modules for size filtration, charge filtration, electrofiltration, electroextraction, or a combination thereof. The system may be configured for electrofiltration, where an electric field is applied between the membrane and the counter electrode. In some embodiments, the system is configured for size and charge selective filtration.

[0009] The electric field can be adjusted to select the desired components. For example, 0.1 V to 5 V can be applied to the electrical contacts and the counter electrode to generate an electric field, a constant potential, or a constant current across the membrane filter.

[0010] Further aspects of the present disclosure include generating an electric field above or within a membrane filter, holding the membrane filter at a constant potential or passing a constant current through the membrane filter; feeding a mixed solution into a membrane nanofilter system; and separating components from the mixed solution into a permeate solution. For example, holding the membrane filter at a constant potential or passing a constant current through the membrane filter can include electrochemically driving / passing a reduction or oxidation current through the membrane filter.

[0011] The method may further include providing a membrane nanofilter system comprising: a membrane filter comprising the nanoporous structure, an electrical contact in contact with the membrane filter, and a counter electrode on top of the membrane electrode.

[0012] In some embodiments, the mixed solution comprises a black mass leachate. The mixed solution components to be separated may be selected from the group consisting of Co, Ni, Al, Mn, Fe, Li, Cu, Ag, Zn ions, ions thereof, or mixtures thereof. The mixed solution may comprise an acid, and the mixed solution may have a pH less than 4.0. For example, the acid is H2SO4. In some embodiments, the method further comprises recycling the acid up to 50%. In some embodiments, Li is a component in the permeate solution.

[0013] In various embodiments, the method may further include removing a retentate solution that includes components not included in the permeate solution. The electric field may be configured to separate components having a lower charge into a permeate solution and components having a higher charge into a retentate solution. For example, the permeate solution may include components having an ionic charge of 1+ or less, and the retentate solution may include components having an ionic charge of 2+ or more. In some embodiments, the method may further include recycling the retentate solution to the leaching step. In further embodiments, the method may further include separating a second component from the recycled mixed solution. In further embodiments, the method may further include passing the retentate solution through one or more additional membrane filters to separate one or more additional components of the mixed solution.

[0014] In some embodiments, the membrane filter comprises silicon and can have a pore size ranging from 1 nm to 500 nm or 500 nm to 1,000 nm. The system may be in a flow-through, dead-end configuration, and / or a cross-flow configuration. The components are separated from the mixed solution by electrofiltration, where the electric field is above the membrane filter, and / or the components (or additional components) are separated from the mixed solution by electroextraction, where an electrochemical oxidation / reduction current is conducted through the membrane filter, where the membrane filter is held at a constant potential, or where a constant current is driven through the membrane filter. In other or additional embodiments, the components are separated from the mixed solution via size- and charge-selective filtration, where the electric field is 0 V / m.

[0015] In some embodiments, the method may further include adjusting the electric field to select the desired component. For example, 0.1 V to 5 V can be applied to an electrical contact connected to the membrane filter and a counter electrode to generate an electric field, potential, or current across the membrane filter.

[0016] In some embodiments, one or more components of the mixture not included in the permeate solution may be retained within the pores of the membrane filter by electrochemical oxidation or reduction, chemical or physical affinity, adsorption, or absorption. The method may further include reversing the polarity of the potential or direction of the current and passing a pure draw solution through the membrane filter. In some embodiments, the pure draw solution comprises water or sulfuric acid. In some embodiments, the method further includes leaching the one or more components retained in the membrane filter into a pure product stream comprising the pure draw solution and the one or more components. The pure draw solution can have a volume between 1% and 50% of the mixture solution volume, producing a concentrated solution of the one or more components.

[0017] In some embodiments, the method may further include precipitating a component from the permeate solution, the retentate solution, the pure product stream, or the pure draw solution.

[0018] Another aspect of the present disclosure is a conductive membrane separation method from a mixed solution, comprising: holding the membrane filter at a constant potential or driving a constant current through the membrane filter; feeding the mixed solution through the membrane filter; and separating components from the mixed solution into a permeate solution.

[0019] Yet another aspect of the present disclosure is a method for separating a conductive membrane from a mixed solution, comprising the steps of: generating an electric field perpendicular or perpendicular to the membrane filter; feeding the mixed solution through the membrane; and separating components from the mixed solution into a permeate solution.

[0020] A further aspect of the present disclosure is a conductive membrane separation method from a mixed solution, comprising: applying an orthogonal or perpendicular electric field to a membrane filter; feeding the mixed solution through the membrane; and separating components from the mixed solution into a permeate solution.

[0021] In one embodiment, the solution includes a monovalent ion component and a multivalent ion component, and the monovalent ion component and the multivalent ion component are filtered differently based on their charge. In another embodiment, the solution includes a first multivalent ion component and a second multivalent ion component, and the first multivalent ion component and the second multivalent ion component are of different charges. In this embodiment, the first multivalent ion component and the second multivalent ion component are filtered differently based on their charge.

[0022] In some embodiments, the method further comprises isolating the monovalent ion component and / or isolating the multivalent ion component. [Brief description of the drawings]

[0023] [Figure 1A] FIG. 1 is a schematic diagram of an exemplary system for performing size- and charge-selective filtration in a dead-end configuration. [Figure 1B] FIG. 1 is a schematic diagram of an exemplary system for performing size- and charge-selective filtration in a cross-flow configuration. [Figure 2A] FIG. 1 is a schematic diagram of an exemplary system for performing electrofiltration in a dead-end configuration. [Figure 2B] FIG. 1 is a schematic diagram of an exemplary system for performing electrofiltration in a cross-flow configuration. [Figure 3A] FIG. 1 is a schematic diagram of one exemplary system for performing the first step of electroextraction in a flow-through configuration. [Figure 3B] FIG. 1 is a schematic diagram of an exemplary system for performing the second step of electroextraction in a flow-through configuration. [Figure 4A] 1 is an exemplary membrane filter system having a charged membrane filter within a pressure cell. [Figure 4B] FIG. 1 is an example of a membrane filter system with a charged membrane filter within a pressure cell. [Figure 4C] 1 is an example showing how a ring terminal connects to a counter electrode. [Figure 4D]1 is an example showing the distance between a counter electrode and a membrane filter. [Figure 4E] 1 shows a cross section of the bottom of a pressure cell of an exemplary membrane filter system. [Figure 4F] 1 illustrates an exemplary spring-loaded electrical contact in an exemplary membrane filter system. [Figure 4G] 1 shows portions of an exemplary membrane filter system being assembled or disassembled. [Figure 4H] 1 shows portions of an exemplary membrane filter system being assembled or disassembled. [Figure 4I] 1 shows portions of an exemplary membrane filter system being assembled or disassembled. [Figure 5A] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5B] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5C] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5D] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5E] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5F] 1 illustrates a portion of an exemplary membrane filter system having a charged membrane filter within a stainless steel pressure cell. [Figure 5G] 1 shows an exemplary membrane filter system comprising a charged membrane filter in a polycarbonate pressure cell. [Figure 5H] 5A-5F show testing of the exemplary membrane filter system. [Figure 6A]FIG. 2 is an exploded view of an exemplary membrane module. [Figure 6B] 1 is an exemplary membrane module with three membrane filter plates. [Figure 6C] The feed solution is shown being drawn up into a manifold, distributed in parallel across multiple membrane filters, and then collected in another manifold before being exhausted from the module. [Figure 6D] The feed solution is shown being drawn up into a manifold, distributed in parallel across multiple membrane filters, and then collected in another manifold before being exhausted from the module. [Figure 6E] The permeate solution is shown passing through the membrane filter into the flow channel and moving outward towards the circumferential grooves where it is collected in a common drain. [Figure 6F] The permeate solution is shown passing through the membrane filter into the flow channel and moving outward towards the circumferential grooves where it is collected in a common drain. [Figure 7A] 1 illustrates the top surface of an exemplary membrane filter plate. [Figure 7B] 1 shows the underside of an exemplary membrane filter plate. [Figure 7C] FIG. 2 is a side view of an exemplary membrane filter plate. [Figure 8] 1 is a flowchart representation of an exemplary method. [Figure 9A] 1 is a flowchart representation of an alternative exemplary method for electrofiltration. [Figure 9B] 1 is a flowchart representation of an alternative exemplary method for electrical extraction. [Figure 10] 1 is a process flow diagram of another example method. [Figure 11] 11 is a process flow diagram of an additional exemplary method. [Figure 12] 1 shows the difference in transport of ionic species through an exemplary membrane filter when the membrane is charged (1 V) and uncharged (0 V). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The following description of embodiments of the invention is not intended to limit the invention to those embodiments, but rather to enable any person skilled in the art to make and use the invention.

[0025] overview The systems and methods for nanofiltration methods include a membrane filter including a nanoporous structure; and one or more electrodes configured to apply an electric potential to the membrane filter or drive a current through the membrane filter. For example, the system can include electrical contacts in contact with the membrane filter and a counter electrode, and the system can be configured to generate an electric field between the membrane filter and the counter electrode and hold the membrane filter at a constant electric potential or drive a constant current through the membrane filter. In one example, the system may be operable to separate a component from the mixed solution when the pH of the mixed solution is 5.0 or less. For example, the system may be operable at a pH of 2-5, less than 5, less than 4, less than 3, less than 2, or less than 1. In some examples, the membrane filter may further include a coating, including a functional coating within and around the porous structure of the membrane filter. In one embodiment, the system and method further include feeding the mixed solution through the membrane filter, thereby separating the desired component (i.e., compound / compounds / ions) from the mixed solution. The components separated from the mixed solution may be selected from Co, Ni, Al, Mn, Fe, Li, Cu, Ag, Zn, ions thereof, or mixtures thereof. Non-limiting examples of ions include Co, 2+ , Co 3+ , Ni 2+ , Al 3+ , Mn 2+ , Fe 2+ , Fe 3+ , Li + , Cu 2+ , Ag + , Zn 2+, and combinations and variations thereof. The system and method functions to uniquely construct and employ a membrane filter system capable of separating nanoscale compounds at low pH utilizing size, charge, and / or compound-membrane interactions. The system and method can enable multiple variations of separation, in a first method of separation, the mixture is separated by driving the small pore size (e.g., less than 100 nm) of the membrane filter through the membrane system under high pressure (e.g., via hydraulic pressurization of the feed mixture solution). The system and method can also enable different forms of separation, where components are separated by diffusion through or across the membrane driven by a concentration gradient (or other type of gradient). In one embodiment, the system and method can perform separation using electrofiltration, using high pressure and small pore size of the charged membrane to separate the desired compound / compound / ion from the mixed solution. In other embodiments, the system and method can perform separation using electroplating, using low pressure and large pore size in the charged membrane to separate the desired compound / compound / ion from the mixed solution.

[0026] The present systems and methods have general applicability to any area of ​​nanoscale (or larger) separation and / or extraction.

[0027] The present systems and methods are applicable to the extraction of small charged ions, elements, and compounds from mixtures, where the present systems and methods are particularly useful for molecular (i.e., nanometer scale) extraction at lower pH (i.e., below pH 5.0). The present systems and methods further allow for nanoscale extraction at pH below 2.0 or below 1.0. The present systems and methods are also applicable to atomic scale (i.e., on the order of angstroms) extraction (e.g., elemental or ionic extraction), where the present systems and methods are particularly useful for atomic extraction at low pH (i.e., below pH 5.0) or ultra-low pH (i.e., below pH 2.0 or below 1.0). In various examples, the system can be operated at a pH ranging from 0-5, 0-4, 0-3, 0-1, 0.5-5, 0.5-4, 0.5-3, 0.5-2, 0.5-1, 0.1-5, 0.1-4, 0.5-3, 0.1-2, 0.1-1, 1-5, 1-4, 1-3, 1-2, 2-4, or 2-5. In some examples, the system can be operated at a pH of 2-5, less than 5, less than 4, less than 3, less than 2, or less than 1. This compound extraction is particularly useful in the field of hydrometallurgy where small compounds and elements can be filtered and / or extracted without the need for chemical precipitation, chemical pH neutralization techniques, liquid-liquid extraction (solvent exchange), thermal distillation, or thermal crystallization.

[0028] The present system and method are particularly applicable to material extraction from battery leachates (e.g., as applied to battery recycling). That is, the present system and method can be applied to the extraction of typical battery compounds (e.g., lithium carbonate, lithium hydroxide, cobalt sulfate, nickel sulfate, manganese oxide) from batteries or battery leachates (e.g., black mass leachates). In some examples, the major black mass components include, but are not limited to, Al, Co, Cu, Fe, Li, Ni, Ag, Zn, Mn, graphite, F, P, and ions thereof.

[0029] The present systems and methods may provide many potential advantages. The present systems and methods are not limited to providing such advantages in any particular case, and are presented only as exemplary representations of how the present systems and methods may be used. The list of advantages is not intended to be exhaustive, and other advantages may additionally or alternatively exist.

[0030] Some advantages of the present systems and methods include reduced system complexity and / or reduced processing stages / footprint due to the ability to recover multiple components of the mixed solution without further difficult processing steps and / or the ability to reuse one or more components of the system, which can lead to reduced capital and operating costs as well as reduced chemical and heat usage.

[0031] One potential advantage of the present systems and methods is that they enable membrane separations under acidic conditions.

[0032] Additionally, the present systems and methods provide the potential advantage of being usable for multiple forms of membrane separation, for example, in some embodiments, the systems and methods allow for the use of membrane separation to separate by molecular / atomic / ionic size, charge, and / or membrane interactions.

[0033] As part of battery recycling implementations, the present systems and methods can enable separation and extraction of valuable metals with very high selectivity and / or yield, potentially offering a significant advantage over current chemical precipitation / solvent extraction / thermal crystallization techniques that contaminate the battery mixture and require high capital and operating costs, thereby limiting extraction.

[0034] As part of the implementation of battery recycling, the present system and method can further provide the potential benefit of a means for lithium extraction. Using current battery recycling means, the battery mixture is generally too contaminated for most extraction techniques to be applied at a reasonable cost of resources and time. Especially for battery chemistries such as lithium-iron-phosphate, where lithium is the only high-value material, recycling is particularly difficult from an economic standpoint. In such cases, the present system and method are particularly beneficial.

[0035] system A system for nanofiltration capable of low pH includes a membrane filter comprising a porous structure having pore sizes ranging from the order of 1 nanometer to the order of 1,000 nanometers. In one embodiment, the system includes at least one electrode operable to pass an electric current through the membrane filter or to hold the filter at a constant potential. For example, the system can be configured to generate an electric field between the membrane filter and a counter electrode to hold the membrane filter at a constant potential or to pass a constant current through the membrane filter. In other embodiments, the membrane filter may include a coating, including a functional coating, within and around the porous structure of the membrane filter. The system functions as a membrane particularly suitable for filtration of nanometer or atomic scale compounds at low pH (i.e., pH 5.0 or less) or ultra-low pH (i.e., pH 2.0 or less). In various examples, the system can be operated at pH values ​​ranging from 0-5, 0-4, 0-3, 0-1, 0.5-5, 0.5-4, 0.5-3, 0.5-2, 0.5-1, 0.1-5, 0.1-4, 0.5-3, 0.1-2, 0.1-1, 1-5, 1-4, 1-3, 1-2, 2-5, less than 5, less than 4, less than 3, less than 2, or less than 1. In other examples, the system can be operated at a neutral pH range of 6-8, or at a basic pH range of 8-14. In at least one example, the system can be used with a mixed solution that includes sulfuric acid. In some embodiments, the system can be operable to recycle at least a portion of the sulfuric acid. As shown in Figures 1A-3B, the system and / or membrane filter can have multiple variations and can be implemented to separate via size, charge, and / or membrane / compound interactions (e.g., membrane adsorption, electrochemical reduction and / or oxidation, or substrate binding). 4A-6C show an exemplary membrane nanofilter system.

[0036] The system is particularly useful for filtering battery metals and chemicals from battery leachates (e.g., as part of a process for battery recycling). For example, the system can be implemented to extract lithium (Li) from a battery solution (e.g., black mass leachate). If desired, the system can be implemented for filtering other battery metals or chemicals, such as cobalt (Co), manganese (Mn), nickel (Ni), etc. Additionally or alternatively, the system can be implemented for filtering other chemicals or minerals used in current or future batteries.

[0037] The system can include a membrane filter, which acts as a primary filtration body, and which includes a porous body, i.e., the membrane filter includes a porous structure, which allows fluid to flow through the membrane filter, and depending on the implementation, certain compounds (or elements / ions) within the fluid selectively pass through the membrane filter at different rates.

[0038] Membrane filters, as porous bodies, can be implemented with any desired porosity. For general filtration purposes, membrane filters can be implemented to have a desired porosity between 1%-5%, 5%-10%, 10%-20%, 20%-30%, 30%-40%, or 40%-50%. Alternatively, membrane filters may have porosities below or above the suggested ranges. For example, in industrial high-flow, high-throughput implementations, membrane filters may be constructed from thick columns (e.g., 20 μm-1 cm thick) with high porosity (e.g., 70% porosity).

[0039] The pores in and through the membrane filter may vary depending on the embodiment. Unless otherwise stated, for ease of explanation, the pores in the membrane filter are described herein as being relatively cylindrical, and the pore size refers to the approximate diameter of the pore. In practice, the pores in the membrane filter may be of any shape, and the pore size refers to the size of a certain common uncharged spherical molecule or spherical uncharged particle that can pass through the pore at a reasonable speed. In some variations, especially in the filtration of large molecules (e.g., polymers), the shape of the pores can be controlled to match the shape of molecules with complex shapes. In such variations, the discussion of pore size may be ignored, and the relative permeability of molecules is discussed instead.

[0040] The membrane filter can have pores that are generally on the order of nanometers long or longer. In some examples, the pores may extend through the membrane filter such that there is a path for at least one component of the mixed solution to pass through the pores of the membrane filter from the top to the bottom. In various embodiments, the pore size of the membrane filter can be between about 1 nm to 10 nm, 1 nm to 100 nm, 10 nm to 50 nm, 10 nm to 100 nm, 50 nm to 100 nm, or 100 nm to 500 nm, or 500 nm to 1000 nm. In some examples, the pore size of the membrane filter is 1 nm to 10 nm, 10 nm to 20 nm, 20 nm to 30 nm, 30 nm to 40 nm, 40 nm to 50 nm, 50 nm to 60 nm, 60 nm to 70 nm, 70 nm to 80 nm, 80 nm to 90 nm, or 90 nm to 100 nm. In some embodiments, a pore size is considered small if it is less than 100 nm, less than 50 nm, or less than 10 nm. In other examples, the pore size may be between about 100 nm to 150 nm, 150 nm to 200 nm, 200 nm to 250 nm, 250 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, 400 nm to 450 nm, 450 nm to 500 nm, 500 nm to 550 nm, 550 nm to 600 nm, 600 nm to 650 nm, 650 nm to 700 nm, 700 nm to 750 nm, 750 nm to 800 nm, 800 nm to 850 nm, 850 nm to 900 nm, 900 nm to 950 nm, or 950 nm to 1000 nm. In some embodiments, a pore size may be considered large if it is greater than 100 nm. Alternatively, the pore size of the membrane filter can be large or small (e.g., 1 Å, 1 μm, 10 μm, etc.) Depending on the implementation, the dispersion and distribution of membrane filter pore sizes can be controlled.

[0041] As is common in many filtration practices, the pore sizes may be relatively similar. That is, the pore sizes may have a small variance. For example, the pore size variance may be about 1% of the pore size. In general, the pore size variation may be in any range. For example, in some embodiments, the pore size variance is about 1%-5% of the pore size; in other embodiments, the pore size variance is about 5%-10% of the pore size; in other embodiments, the pore size variance is about 10%-20% of the pore size; in other embodiments, the pore size variance is about 20%-30% of the pore size; in other embodiments, the pore size variance is about 30%-40% of the pore size; in other embodiments, the pore size variance is about 10%-20% of the pore size. in other embodiments, the pore size distribution is about 50% to about 60% of the pore size; in other embodiments, the pore size distribution is about 60% to about 70% of the pore size; in other embodiments, the pore size distribution is about 70% to about 80% of the pore size; in other embodiments, the pore size distribution is about 80% to about 90% of the pore size; in other embodiments, the pore size distribution is about 90% to about 100% of the pore size, etc.

[0042] The thickness of the membrane filter may vary, and the thickness may be selected to meet a particular filtration embodiment. In a typical embodiment, the membrane filter may generally have a thickness in the range of 10 μm to 50 μm, 50 μm to 100 μm, 100 μm to 150 μm, 150 μm to 200 μm, 200 μm to 250 μm, 250 μm to 300 μm, 300 μm to 350 μm, 350 μm to 400 μm, 400 μm to 450 μm, 450 μm to 500 μm, 500 μm to 1000 μm, or 1000 μm to 10000 μm. In at least one example, the membrane filter may have a thickness of 280 μm. Alternatively, the membrane filter may have a thickness of less than that. For example, in one embodiment, the membrane filter has a thickness of about 1 μm. In general, the thickness of a membrane filter is limited only by mechanical constraints (e.g., that the membrane is thick enough so that it does not break or twist during filtration) and the membrane pore size (i.e., that the membrane thickness is large enough to incorporate the desired pore size, or range of pore sizes) and porosity. If the membrane is thin, it can be supported by a mechanically stable thicker layer with a larger pore size. In this embodiment, the thin membrane and the thicker support layer may be monolithic (a continuous piece of material). In some embodiments, the membrane filter may be a flat disk having a diameter of 1 inch to 1.5 inches, 1.5 inches to 2 inches, 2 inches to 2.5 inches, 2.5 inches to 3 inches, 3 inches to 3.5 inches, or 3.5 inches to 4 inches. In at least one example, the membrane filter may have a diameter of 2 inches. In at least one example, the membrane filter may have a diameter of 0.4 meters.

[0043] The membrane filter may be composed of an inorganic element or compound (or compounds). In some embodiments, the membrane filter is composed of a conductive material. In one variation, the inorganic compound membrane filter includes a body composed primarily of silicon. In one example, the silicon body is composed of a monolithic piece of silicon, or alternatively of nanoporous silicon. For example, the membrane filter may be a silicon wafer modified to have pores in the range of 1 nm to 500 nm, or 1 nm to 1,000 nm. Alternatively, the silicon body may include multiple portions (e.g., layers of silicon).

[0044] In other variations, the membrane filter is composed of an organic compound (or compounds). In one variation, the organic compound membrane filter includes a body made of a polymer. Examples of polymeric materials can include polyamide, polysulfone, polycarbonate, PTFE, and / or polyimide. In some variations, the membrane filter may include multiple layers of the same polymer, or a composite of multiple layers of different polymers. In this variation, the polymeric membrane can be made conductive by functionalizing the membrane with a conductive material.

[0045] Depending on the intended implementation of the system, the membrane filter may enable one or more types of filtration. Depending on the implementation, the membrane filter may be configured to filter based on size, charge, electrochemical reduction and oxidation potential, and / or via membrane / compound interaction(s). In some examples, the system may be configured for size and charge selective filtration, electrofiltration, or electroextraction. The membrane filter may also be capable of filtering based on hydrophobicity, chirality, solubility, redox potential, coordination number, and / or other molecular / compound properties.

[0046] In some variations, the membrane filter may include structures that allow for size filtration. In such variations, the membrane filter may include pore sizes that are "tuned" to allow the passage of one or more compounds / molecules / atoms / ions and retain all other species. That is, the membrane filter is configured with a desired porosity and a desired pore size that depends on the effective size of the compounds / molecules / atoms / ions to allow for filtration and / or separation. For example, in the case of black mass leachate, Li passes through the membrane filter while Co, Ni, Mn are retained. This size exclusion may not be based solely on atomic mass / size, but also on additional coordination effects (e.g., hydration and ionic charge), which may result in different effective sizes of the filtered compounds.

[0047] In some variations, the membrane filter may include structures that allow for filtration by charge. In such variations, the membrane filter may be constructed of a material (e.g., silicon) that can carry a charge or is conductive. That is, the membrane filter is constructed with a desired conductivity, or range of conductivity, to allow for filtration and / or separation of compounds / molecules / ions that depend on the effective charge. In some examples, the membrane filter may have a resistivity in the range of 100 Ω·cm to 0.001 Ω·cm, 100 Ω·cm to 50 Ω·cm, 50 Ω·cm to 10 Ω·cm, 10 Ω·cm to 1 Ω·cm, 1 Ω·cm to 0.1 Ω·cm, 0.1 Ω·cm to 0.01 Ω·cm, or 0.01 Ω·cm to 0.001 Ω·cm. For charge separation, the system may further include a current source or sources, and may include a current sink or sources; where a desired current or currents are formed and driven through or on the membrane filter, or a constant potential is applied to the membrane filter.

[0048] Membrane filters can be implemented with different directions of flow. In addition to flow directly through the membrane, membrane filters can also be used with flow parallel to the membrane surface and / or at an angle to the membrane. The system can be in a flow-through, dead-end, or cross-flow configuration. In a flow-through or dead-end configuration, the mixed solution is fed down through the upper side of the membrane filter (e.g., perpendicular to the membrane filter), and the permeate solution is collected on the lower side of the membrane filter. Figures 1A, 2A, and 3A show examples of dead-end / flow-through configurations. In a cross-flow configuration, the mixed solution is fed across the upper side of the membrane filter (e.g., parallel to the membrane filter), the permeate solution is collected below the membrane filter, and the retentate solution remains above the membrane filter. Figures 1B and 2B show exemplary cross-flow configurations. In some embodiments, the separation can be operated in a continuous mode and / or allow for the reuse of one or more components of the mixed solution.

[0049] The system may use size filtration, electrofiltration, electroextraction, or a combination thereof to separate at least one component from the mixed solution. In some embodiments, such as electrofiltration as seen in Figures 2A and 2B, an electrical contact may be placed in electrical contact with the membrane filter, and a counter electrode may be placed above the top surface of the membrane filter. As an example, the charged membrane filter may be the cathode and the counter electrode may be the anode. When a voltage is applied between the charged membrane filter and the counter electrode, an electric field is generated above the top surface of the membrane filter, and the electric field prevents highly charged components (compounds / molecules / atoms / ions) from passing through the pores, while allowing less charged components (compounds / molecules / atoms / ions) to pass through the pores. In other words, the electric field is configured to separate components with lower charges into the permeate solution and components with higher charges into the retentate solution. In other examples, the electric field acts to "pull" ions through the membrane, with higher charges being more likely to be pulled into the permeate solution. In some embodiments, the permeate solution consists of components with an ionic charge of 1+ or less, and the retentate solution consists of components with an ionic charge of 2+ or more. For example, in the case of black mass leachate, the electric field causes Li to pass through the membrane filter, while Co, Ni, Mn, etc. are retained above the membrane filter. In some embodiments, the separation of one component and retention of the other in the mixed solution may also be based on additional coordination effects (e.g., size, polarity, hydration), which may result in different effective permeabilities of the filtered compounds.

[0050] Referring to Figure 2A, in some embodiments, the system can be configured for electrofiltration in a dead-end configuration. Figure 2A shows how the feed solution (i.e., the mixed solution) enters the membrane filter from the top and passes through an electric field between the top surface of the charged membrane filter and a counter electrode. x represents an ion dissolved in an aqueous solution, with an ionic charge of x. The less charged component (generally M + The highly charged components (generally M 2+ and M.3+ The charged components (denoted as ) are held in an electric field above the membrane filter. In some instances, uncharged components pass through the pores into the permeate solution or are retained above the membrane filter by size selection of the pore size. In some embodiments, the strength of the electric field can be adjusted to select for differently charged components.

[0051] Returning to FIG. 2B, in some embodiments, the system may be configured for electrofiltration in a cross-flow configuration. FIG. 2B shows how the feed solution (i.e., the mixed solution) flows across the top surface of the membrane filter and passes through an electric field between the top surface of the charged membrane filter and a counter electrode. The less charged components (typically M + The highly charged components (generally M 2+ and M. 3+ The charged components (denoted as ) are retained in the electric field above the membrane filter and are discharged as a retentate solution. In some instances, uncharged components pass through the pores into the permeate solution or are retained above the membrane filter by size selection of the pore size. In some embodiments, the strength of the electric field can be adjusted to select for differently charged components.

[0052] In some embodiments, the membrane filter may have small pores when used for electrofiltration by an electric field at the surface of the membrane filter. For example, the membrane filter may have a pore size of 1 nm to 10 nm, 10 nm to 20 nm, 20 nm to 30 nm, 30 nm to 40 nm, 40 nm to 50 nm, 50 nm to 60 nm, 60 nm to 70 nm, 70 nm to 80 nm, 80 nm to 90 nm, or 90 nm to 100 nm when used for electrofiltration.

[0053] In other embodiments, such as electroextraction (e.g., electroplating) as seen in Figures 3A and 3B, electrical contacts may be placed on the membrane filter and a counter electrode may be placed above the membrane filter to hold the membrane filter at a constant potential or to drive a constant current through the membrane filter such that the pore walls in the membrane filter are charged and attract certain components (compounds / molecules / atoms / ions) to be electrochemically reduced or oxidized and immobilized on the pore walls while allowing other components to pass through. In some embodiments, for electroextraction, the membrane filter is held at a constant potential or a constant current is driven through the membrane filter. In some instances, the potential and / or current may vary. Thus, as used herein, a "constant" potential or a "constant" current may be controlled to be within a set parameter threshold (e.g., ±10% of a desired constant potential or constant current). Electroextraction may be used in a constant flow system or a batch pressure cell.

[0054] The specific components can be immobilized within the pores of the membrane filter, either at the membrane filter pore wall surface or by being absorbed within the membrane material. The initial feed solution (mixed solution) can then be replaced with a pure solution (e.g., water or sulfuric acid) into which the specific components of interest can be released. In this example, the polarity of the electric field can be reversed to aid in the release of the components retained in the membrane filter. In this example, the total volume of pure solution passing through the membrane is much less (1-50%) than the volume of the mixed solution from which the components were extracted, resulting in a more concentrated solution of the components of interest. In another example, the mixed solution flows across the membrane filter, and multiple components pass freely through the membrane filter, but only one (or multiple specific components) of the mixed solution is retained by the membrane filter. A pure solution is then passed through (optionally with an electric field of reversed polarity) to release the retained specific components therein. The components retained within the membrane filter and / or the components passing through the membrane filter can be selected from Li, Co, Ni, Al, Mn, Fe, Cu, Al, Ag, Zn, etc. In one example, as seen in FIG. 3A, a feed solution (e.g., battery leachate) may pass through a membrane filter where some components (compounds / molecules / atoms / ions) such as Co, Ni, Al, Mn, Fe, Cu, Al, Ag, Zn are retained within the pores of the membrane filter while other components such as Li pass through the pores. In some embodiments, as seen in FIG. 3B, the polarity of the electric field can be reversed and a pure draw solution (e.g., water) passed through the system to extract the components (compounds / molecules / atoms / ions) trapped within the pores of the membrane filter and exit the system as a pure product stream. In some examples, an acid wash may be required to achieve 100% or close to 100% removal.

[0055] In some embodiments, when used for electroextraction by an electric field inside the membrane filter, the membrane filter may have larger pores. For example, the membrane filter may have a pore size of 100 nm to 150 nm, 150 nm to 200 nm, 200 nm to 300 nm, 300 nm to 400 nm, 400 nm to 500 nm, or 500 nm to 1,000 nm when used for electroextraction.

[0056] In some embodiments, the system may be configured for recycling of acid and other materials used in the system. The batteries crushed into black agglomerates are typically dissolved in an acid, such as sulfuric acid or hydrochloric acid, to form a leachate. Typically, unwanted low-value materials in the leachate, such as Fe and Al, precipitate and the sulfuric acid could not be recovered, as this would also require the addition of heat and neutralizing chemicals (sodium hydroxide or sodium bicarbonate). Since the system and process of the present invention does not require the addition of heat, precipitation, or other chemicals, at least a portion of the sulfuric acid can be recovered and reused for further use in the leaching system / process. For example, up to 10%, up to 20%, up to 30%, up to 40%, or up to 50% of the sulfuric acid can be recovered and reused in the system / process. Thus, the system allows for continuous reuse of the sulfuric acid.

[0057] In additional embodiments, the process can be run multiple times and the electric field adjusted to select for different components. For example, the retentate and / or permeate solutions can be reused as a mixed solution or recycled into the mixed solution so that a second component can be separated. In other embodiments, multiple electrofiltration and / or electroextraction modules can be combined in series to extract a range of components.

[0058] 4A-4I show one embodiment of a system that may be used for electrofiltration or electroextraction. The system 100 may include a pressure cell 102 operable to enable charging of the membrane filter 104 and to introduce an electric field 101 to a surface of the membrane filter 104. In an embodiment, the pressure cell 102 may include the membrane filter 104, a counter electrode 106, and an electrical contact 134. In various embodiments, the system may further include a porous support piece 108, an inlet pressure port 110, an O-ring 112, a housing 114, an insulated wire (i.e., counter electrode lead) 116, a plastic shim 118, a shim 120, a clamp 122, an end cap 124, a spout 126, a plastic rod 128, a centering spacer 130, and / or a quick disconnect terminal 132.

[0059] In some embodiments, the counter electrode 106 may be constructed of a conductive mesh with large porosity to allow all compounds / ions to pass through. In at least one example, the counter electrode 106 is a platinum mesh. FIGS. 4B-4D further show that the counter electrode 106 may be supported by a rod 128 that extends the length of the housing 114 of the pressure cell 102. In some embodiments, the rod 128 may be supported by at least one centering spacer 130. In some examples, the rod 128 comprises a plastic material and the centering spacer 130 comprises a plastic material or PTFE. The two centering spacers 130 may be press-fit into the pressure cell 102. FIG. 4G shows how the rod 128, counter electrode 106, insulated wire 116, and associated elements may be removed through the bottom of the pressure cell if needed for cleaning, modification, or replacement. Figure 4H shows that the counter electrode 106 is reinstalled through the bottom of the pressure cell 102, the membrane filter 104 and porous support piece 108 are installed, and the clamp 122 is clamped to the bottom of the pressure cell 102. Figure 4I shows how the insulated wire 116 is connected to the lid pass-through 146 using the quick connect / disconnect terminal 132.

[0060] The insulated wire 116 may be an electrical lead connected to the counter electrode 106. As seen in FIG. 4B, the insulated wire 116 may have a quick disconnect terminal 132. In one example, it may be a ¼” quick disconnect terminal 132. The insulated wire 116 may be an epoxy wire, such as a PTFE insulated wire. In some examples, as seen in FIG. 4C, the insulated wire 116 may be connected to the counter electrode 106 via a gold plated ring terminal 138. The ring terminal 138 may be held in place using one or more washers 140 and a mounting screw 142. Referring to FIG. 4D, the distance 144 between the counter electrode 106 and the membrane filter 104 may be controlled by the number of washers 140 added below the mounting screw 142. The distance 144 between the ring terminal 138 and the filter 104 may range from 0.1 mm to 10 mm. In some non-limiting examples, the distance 144 may be 0.1 mm to 0.5 mm, 0.5 mm to 1 mm, 0.5 mm to 1.5 mm, 1.25 mm, 2.5 mm, 3.75 mm, or 5 mm. In some embodiments, the washer 140 may be a PTFE washer and the mounting screw 142 may be a PEEK mounting screw. Other materials known in the art are contemplated for the ring terminal 138, washer 140, and screw 142. In some examples, the washer 140 and screw 142 may be made of a non-conductive material.

[0061] In one embodiment, the electrical contacts 134 are spring-loaded electrical contacts. For example, the electrical contacts 134 may be pogo pins. As seen in FIG. 4F, the wires / leads 138 for the electrical contacts 134 are disposed within an insulating plastic tube and pass through a Swagelok fitting. The housing 114 may further include an opening 136 operable to receive the electrical contacts 134. The electrical contacts 134 may contact the membrane filter 104 on an upper side of the membrane filter 104. FIGS. 5A-5F show an exemplary system having the electrical contacts 134 inserted into the pressure cell 102 through an opening 136 in the side of the housing 114.

[0062] In an embodiment, the pressure cell 102 is made of stainless steel, for example as seen in Figures 5A-5F. In some embodiments, the pressure cell 102 is made of polycarbonate, Teflon, PFA, or other chemically resistant materials. Figure 5G shows an exemplary polycarbonate pressure cell 102. The pressure cell includes an inlet pressure port 110, a relief valve 111 (60 psi), a counter electrode lead 116, a counter electrode 106, a membrane filter 104, and a porous support piece 108.

[0063] In various embodiments, the pressure cell can operate under pressures ranging from 0 psi to 50 psi, 50 psi to 100 psi, 100 psi to 200 psi, 200 psi to 300 psi, 300 psi to 400 psi, 400 psi to 500 psi, 500 psi to 1000 psi, 1000 psi to 1500 psi, 1500 psi to 2000 psi, 2000 psi to 2500 psi, or 2500 psi to 3000 psi. Whether the system is electrified or non-electrified, the system can operate at pressures up to 3000 psi. In some examples, low pressure conditions may refer to pressures below 500 psi. In other examples, high pressure conditions may refer to pressures above 500 psi. Stainless steel pressure cells can operate in both low and high pressure conditions, while polycarbonate or Teflon pressure cells can operate in low pressure conditions. As an example, a stainless steel pressure cell may be internally coated with a chemically resistant polymer to allow operation at high pressures with low pH solutions (pH<2). As an example, a stainless steel pressure cell may withstand pressures up to 3000 psi. In one embodiment, systems with smaller pore sizes (e.g., 1 nm to 100 nm) are used at higher pressures and systems with larger pore sizes (e.g., 100 nm to 1000 nm) are used at lower pressures. In at least one example, a system with a membrane filter with a pore size of 10 nm may operate at pressures in excess of 700 psi.

[0064] In various embodiments, the system may further include a pump operable to pump the mixed solution, the permeate solution, and / or the reverse osmosis solution through the system at a desired pressure.

[0065] In some embodiments, the housing of the pressure cell can have a polymeric or other electrically insulating coating that prevents the conduction of electrical current throughout the pressure cell and allows the electrical current to be confined to the membrane filter or between the membrane filter and the counter electrode.

[0066] Application of electric current to the membrane does not act to draw specific ions through the membrane, but rather acts to enhance the ion separation selectivity of the membrane, allowing for greater specificity in the separation of target substances. In this embodiment, transport through the membrane is achieved by either concentration gradient or pressure-driven flow. As part of the charge separation, the membrane filter can allow for the separation of multiple compounds / elements in a solution, and molecules / ions of different charge magnitudes can be positionally separated within the solution as the entire sample solution, or a portion of the sample solution, passes through the membrane filter.

[0067] In some variations, the membrane filter may include structures that allow for filtration by interaction of molecules / compounds / ions in solution with the membrane. In such variations, the membrane filter may be composed of materials that allow for interaction with specific molecules / ions / atoms, types of molecules. In some variations, this may include binding sites where a substrate may bind to the membrane and allow / disable passage across the membrane.

[0068] Additionally or alternatively, the membrane filter may be comprised of a semi-permeable membrane that allows the passage of certain types of molecules / ions while blocking the passage of other types of molecules / ions. For example, in some embodiments, the membrane filter may be comprised of a semi-permeable membrane that allows the passage of polar molecules while blocking the passage of non-polar molecules. In other variations, the membrane filter may allow for unique interactions with certain molecules or classes of molecules. For example, a silicon-based membrane filter may allow for unique interactions with lithium ions, allowing the passage of lithium ions while blocking other ions and other molecules from passing through the membrane filter. In this example, the properties of the silicon membrane filter may be utilized to allow sorption of Li by the membrane filter, followed by desorption to allow the release of Li. In this example, a coating may be applied within the pores of the membrane and on the membrane surface that allows or improves the selective oxidation or reduction of Li, Ni, Co, Al, Fe, Cu, Mn, or other components via an electric current applied to the conductive silicon membrane.

[0069] In some variations, the system may include multiple membrane filters, which can function to provide enhanced filtering of a particular type, multiple types of filtering, and / or other filtering benefits.

[0070] In one example, multiple membrane filters constructed for size filtration can be stacked together to improve size filtration. In one embodiment of this example, multiple membrane filters with decreasing or increasing pore sizes can be stacked in a row to allow filtration of multiple compounds of different sizes. These stacked filters can be used in this manner to create a molecular size gradient in a solution or to filter / separate multiple compounds / ions.

[0071] 6A illustrates an embodiment of a system having multiple membrane filters in a membrane module. In some embodiments, the membrane module 210 may include a top plate 202, one or more membrane plates 204 operable to support a membrane filter 206, and a base plate 208. In some examples, the base plate may also be operable to support the membrane filter 206. Multiple membrane support plates 204 may be stacked between the top plate 202 and the base plate 208 to form a stacked membrane module 210. The membrane module 210 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10-50, 50-100, or multiple (>100) membrane plates 204 and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10-50, 50-100, or multiple (>100) membrane filters 206. FIG 6B shows an exemplary membrane module 210 with three membrane plates and four membranes. The membrane module 210 can have ports 212, 214, 224 for feed, retentate, and permeate lines. FIG 6C and FIG 6D show the mixed solution / concentrate flow entering the manifold / port 212 and being distributed in parallel to multiple membrane filters 206, then collected in another manifold / port 214 before exiting the module. FIG 6E and FIG 6F show the permeate flow passing through the membrane filters 206, entering the channel 216, and moving outward toward the circumferential groove 218 where it is collected in a common drain.

[0072] 7A-7C show views of an exemplary membrane support plate 204. FIG. 7A shows the top side of the membrane support plate 204. In some embodiments, the membrane support plate 204 may include a smooth surface 220 or a flat isotopically microporous surface for supporting the membrane filter 206, a face seal 222 around the retentate manifold / port 214, a permeate hole in the channel 216, a plate drain manifold / port 224, a face seal 226 for the permeate, a secondary seal 228 for the retentate on a cylindrical boss, a face seal 230 around the supply manifold / port 212, one or more PTFE pins 232 for locating the membrane filter 204, and a plate separation groove 234. FIG. 7B shows the bottom side of the membrane support plate 204. In some embodiments, the membrane support plate 204 may further include a smooth surface 236 for a face seal, a circumferential permeate collection groove 218, a cross-flow outlet 238, one or more clearance holes 240 operable to receive one or more PTFE pins 232, a cylindrical bore 242 for a secondary seal 228, a primary face seal 244 for the membrane filter 204, a cross-flow inlet 246, and a clearance hole 248 operable to receive a threaded rod 250.

[0073] In some embodiments, the height of the membrane support plate 204 may be in the range of 0.5 inches to 1 inch. For example, the height of the membrane support plate 204 may be in the range of 0.5 inches to 0.6 inches, 0.6 inches to 0.7 inches, 0.7 inches to 0.8 inches, 0.8 inches to 0.9 inches, or 0.9 inches to 1 inch. In at least one example, the membrane support plate 204 can have a height of 0.875 inches. In some embodiments, the height of the top plate 202 may be in the range of 0.5 inches to 1 inch. For example, the height of the top plate 202 may be in the range of 0.5 inches to 0.6 inches, 0.6 inches to 0.7 inches, 0.7 inches to 0.8 inches, 0.8 inches to 0.9 inches, or 0.9 inches to 1 inch. In at least one example, the top plate 202 can have a height of about 0.875 inches. In some embodiments, the height of the base plate 208 may be in the range of 0.5 inches to 1 inch. For example, the height of the base plate 208 may range from 0.5 inches to 0.6 inches, 0.6 inches to 0.7 inches, 0.7 inches to 0.8 inches, 0.8 inches to 0.9 inches, or 0.9 inches to 1 inch. In at least one example, the base plate 208 may have a height of approximately 0.875 inches. The membrane support module 210 may have a height ranging from 1.5 inches to 10 inches depending on the number of membrane support plates 204 included in the membrane support module 210. In one example, the membrane support module 210 may have a height of approximately 4 inches when including three membrane support plates 204 and four membrane filters 206. The permeate, retentate, and feed manifolds / ports may be sized to accommodate the desired total flow rate through the system. In some embodiments, the size of the manifolds may be larger for more membrane support plates 204 in the membrane module 210 or for a higher flow rate per membrane filter 206. In some instances, the manifolds may be up to 0.5 to 1.0 meters in diameter, with the height increasing with the number of membranes required.

[0074] Similar to multiple filters with the same or varying pore sizes, other types of membrane filters (e.g., charge / current, or membrane-bound / membrane-coated) can be implemented in the same manner. In another example, multiple membrane filters configured to conduct electricity are placed in series. A voltage can then be passed through the membranes such that multiple differently charged components are separated, with the majority of each component being spatially separated by the membrane filters.

[0075] Additionally or alternatively, the system may include multiple filters of different types. For example, one system may include one or more membrane filters that filter by size and one or more membrane filters that interact with desired compounds / ions. In one embodiment for Li filtration, the system may include a silicon membrane filter that adsorbs and desorbs Li and another membrane filter that filters by pore size.

[0076] In some variations, the system can include a coating, which includes a functional coating in and around the porous structure, as well as on the surface of the membrane filter. The specific type of coating can depend on the implementation of the system. The coating can function to improve membrane filtration. Additionally or alternatively, the coating can improve the durability of the membrane filter (e.g., provide increased structural support to the porous structure).

[0077] In some variations, the coating can improve membrane filtration. For example, in an embodiment where a membrane interaction electrowinning process is used to separate Li from black mass leachate, the coating can include a compound or compounds that catalyze the reduction of Li (or other target material) below the reduction potential of water (to avoid the formation of hydrogen and oxygen). The coating can catalyze a sorption / desorption reaction (which may be a redox reaction). That is, the coating can catalyze a reaction between the desired compound and the membrane such that it is sorbed or desorbed from the surface or bulk of the membrane material. For example, the coating can promote the absorption of Li by the membrane when the membrane is conditioned to a particular charge / polarity and release lithium from the membrane when the charge / polarity is removed or switched. Examples of coating compounds can include vanadium oxide, titanium oxide, aluminum oxide, and other oxides. These compounds can be applied to the membrane surface and pores by processes such as atomic layer deposition.

[0078] In some variations, the coating may include a structural coating that improves the structural integrity of the membrane filter. This may be in addition to or instead of the functional aspects of the coating described above. The structural coating may include a compound or compounds that conformally stratify the membrane filter, particularly the porous structure, and provide additional structural support and / or durability. Additionally or alternatively, the structural coating may prevent degradation of the porous structure of the membrane filter. Examples of structural coatings may include non-reactive metals and metal alloys (e.g., aluminum, titanium). In variations where the coating may provide functional aspects, the metal coating may be a metal oxide (e.g., aluminum oxide, titanium oxide).

[0079] In variants where the system includes a coating, the coating can be performed in any desired manner. For nanoscale deposition in the pore structure, atomic layer deposition can be performed. Alternatively, solution-based electrochemical deposition can be performed. Nanoscale deposition allows for the deposition of the coating in and on the porous structure of the membrane filter.

[0080] method As shown in FIG. 8, a method 300 for extracting a substance from a mixture by membrane filtration includes providing a membrane nanofilter system 302; obtaining a mixture solution 304, the mixture solution including a solution containing a desired component for separation; and feeding the mixture solution through a membrane nanofilter system 306, thereby separating the desired component (e.g., compound / ion) from the undesired component (e.g., compound) in the mixture solution. The method functions to separate the desired component from other "undesirable" components. The method can utilize the properties of the membrane filter system to perform the substance extraction process by separating by size, charge, membrane / compound interaction, electrochemical oxidation or reduction, sorption, and / or any combination thereof. Additionally or alternatively, the method may utilize other separation properties such as shape, polarity, magnetization, electrical conductivity, and / or other properties or combinations of properties of the compounds.

[0081] In some variations, the methods function by passing all or a portion of the mixed solution through a membrane nanofilter system (e.g., via pressure-driven flow), whereby the mixed solution is actively filtered such that the desired compound is specifically blocked from passing by the membrane nanofilter system while other compounds in the mixed solution are allowed to pass through the membrane nanofilter system. Alternatively, the desired compound may specifically pass through the membrane nanofilter system while other compounds in the mixture are blocked or prevented from passing through the nanofilter system.

[0082] In some other variations, the method can function by first saturating the membrane nanofilter system with the mixture and then passively or actively driving the mixture out of the membrane nanofilter system. Thus, in such variations, the method can further include saturating the membrane nanofilter system with the mixed solution. Depending on the implementation, the desired compound is separated from the membrane nanofilter system such that the undesired compounds remain in (or are blocked by) the membrane nanofilter system, or the undesired compounds are filtered out of the membrane nanofilter system and the desired compound remains.

[0083] In another variation, the method can function by generating an electric field in the membrane filter, such that the membrane nanofilter system separates components from the mixed solution by charge, as shown in Figures 9A and 9B. In one embodiment, the method 400 of Figure 9A may include providing a membrane nanofilter system 402; obtaining a mixed solution 404; forming an electric field in the membrane filter 406; and feeding the mixed solution through the membrane nanofilter system 408. In another embodiment, the method 450 of Figure 9B may include providing a membrane nanofilter system 452; obtaining a mixed solution 454; passing an electrochemically reducing current through the membrane filter 456; feeding the mixed solution through the membrane nanofilter system 458; feeding a pure draw solution through the membrane filter 460; reversing the current for electrochemical oxidation 462; and recovering the components of the mixed solution in a pure solution 464.

[0084] The method can be carried out using a system as described above. Additionally or alternatively, the method can be carried out using any conventional membrane filter system, particularly for the extraction of desired substances in hydrometallurgical processes.

[0085] Blocks 402 or 452, which include preparing a membrane nanofilter system, function to enable a desired type of filtration in the membrane nanofilter system. Preparing the membrane nanofilter system 402 or 452 may depend on the mixture, the desired compounds to be filtered, and the desired method of filtration. In some variations, the method may not require blocks 402 or 452 because the membrane filter is already prepared.

[0086] In some variations, preparing the membrane nanofilter system 402 or 452 may include constructing the membrane nanofilter system. This includes fabricating an appropriate membrane filter set of the desired size, shape, and thickness. Depending on the type of filtration, fabricating the membrane nanofilter system may further include membrane pore size, pore density, charge capacity, conductivity, functional coating chemistry, binding site configuration, and the like. In some examples, the membrane filter may be prepared as described in U.S. Pat. No. 10,128,341, U.S. Pat. No. 10,943,982, or U.S. Pat. No. 11,004,943, the contents of each of which are incorporated herein in their entirety.

[0087] Although any general steps for constructing a membrane nanofilter system can be carried out, an example for constructing a single Si membrane, membrane nanofilter system is provided herein. Constructing a Si membrane can include obtaining a silicon feedstock (e.g., a silicon wafer); depositing metal particles on the silicon surface (e.g., using sputtering film deposition); and forming the silicon feedstock into a Si membrane (e.g., chemically etching the silicon feedstock by depositing the silicon wafer in a chemical etching bath for a period of time).

[0088] In some variations, preparing the membrane nanofilter system 400 may include treating the membrane nanofilter system. The treatment of the membrane nanofilter system may function to improve functionality. For example, to improve Li / Na separation through the silicon membrane, treating the membrane nanofilter system includes applying a functional coating. The functional coating may function as a catalyst to electrochemically reduce lithium to lithium metal. The reduction or oxidation of lithium is mediated by a voltage applied to the conductive membrane. Once reduced, the lithium diffuses into the silicon lattice and the membrane functions as a reversible lithium sponge. The coating is applied using atomic layer deposition to apply the coating to the nanoscale pore structure or using electrochemical deposition. Examples of coatings include vanadium oxide, titanium oxide, aluminum oxide, and other oxides.

[0089] Block 404 or 454, including obtaining a mixed solution, functions in obtaining a raw material for filtration, the mixed solution including some desired compounds that can be extracted from the mixed solution, the mixed solution being in a suitable form for use with the membrane nanofilter system. In some variations, obtaining the mixed solution 404 or 454 may simply include obtaining (e.g., purchasing, receiving, etc.) the mixed solution. In other variations, obtaining the mixture may include converting lithium ion batteries to black mass and leaching the black mass with a strong acid (H2SO4 or HCl). An exemplary mixed solution may include black mass components including, but not limited to, 1-5 wt% Al, 3-33 wt% Co, 1-3 wt% Cu, 0.1-0.3 wt% Fe, 3.5-4 wt% Li, 3-11 wt% Mn, approximately 35 wt% graphite, 2-4 wt% F, and 0.5-1 wt% P.

[0090] For use in a membrane nanofilter system, the mixed solution may be in a form such that it can be filtered. Depending on the type of membrane nanofilter system, this may vary. Generally, the mixed solution is in some liquid form. If not, obtaining the mixed solution 404 or 454 further includes converting the mixed solution into a usable form. This includes bringing the mixed solution to the proper pH and the proper concentration. The mixed solution is preferably sufficiently dilute so that it can flow through the membrane nanofilter system. This may vary widely depending on the type of filtration and the content of the mixture. In one example, about 1 kg of black lump powder may be dissolved in about 110 kg of sulfuric acid. In another example, about 1 kg of black lump powder may be dissolved in about 10-20 kg of sulfuric acid. In another example, about 1 kg of black lump powder may be dissolved in about 20-50 kg of sulfuric acid. In another example, about 1 kg of black lump powder may be dissolved in about 50-100 kg of sulfuric acid.

[0091] While the pH may vary for each particular embodiment, the method may be particularly applicable for use at relatively neutral or low pH (e.g., pH 1-10). In various examples, the pH of the mixed solution may range from 0-5, 0-4, 0-3, 0-1, 0.5-5, 0.5-4, 0.5-3, 0.5-2, 0.5-1, 0.1-5, 0.1-4, 0.5-3, 0.1-2, 0.1-1, 1-5, 1-4, 1-3, or 1-2. In some variations, the pH may be very acidic. In some acidic examples, the pH is about 2.0, less than 2.0, or between pH 1.0 and pH 2.0. In other acidic examples, the pH is about 1.0. In other acidic examples, the pH is less than 1.0. In some pH<1.0 (e.g., pH 0.1) embodiments, the system may be first run with concentrated sulfuric acid (98%). In some examples, the method includes recycling a portion of the sulfuric acid. Depending on the desired results, the system may be maintained at that pH or the pH may be increased during operation (e.g., the pH may be increased to pH ~1.0). In other examples, the system may operate at a neutral pH in the range of 6-8, or at a basic pH in the range of 8-14.

[0092] Generally, in hydrometallurgical implementations, obtaining the mixed solution 404 or 454 may include digesting solid compounds, thereby producing a liquid mixture for filtration. For example, in battery recycling implementations, obtaining the mixed solution 404 or 454 may include converting the batteries into "black mass." This may include physically separating the battery components, crushing the anodes and cathodes, digesting the crushed components with acid, adding neutralizing components, etc.

[0093] Block 406 of FIG. 9A includes generating an electric field on the membrane filter of the membrane nanofilter system. The electric field can be generated perpendicular or perpendicular to the membrane filter. For charge filtration implementations (e.g., electrofiltration), generating the electric field 406 can include generating an electric field between the membrane filter and a counter electrode (e.g., through electrical contact and applying a voltage to the membrane filter via the counter electrode). A voltage applied to the membrane filter and the counter electrode generates an electric field between them. This electric field can act as a driving force to separate components from the mixed solution. The strength and / or polarity of the electric field can also be increased, decreased, or changed direction during filtration. For electroextraction in FIG. 9B, electrochemically applying a reducing current to the membrane filter 456 can include charging the membrane filter (e.g., the membrane filter is held at a constant potential or a constant current is passed through the membrane filter). In some examples, the membrane filter is held at a constant potential or a constant current is passed through the membrane filter. Charged membrane filters are capable of selectively immobilizing target components within the membrane filter pores via electrochemical reduction or oxidation.

[0094] The electrical contacts and the counter electrode are subjected to a voltage between 0.1 V and 5 V. In some examples, a voltage of 0.1 V, 0.5 V, 1 V, 1.5 V, 2 V, 2.5 V, 3 V, 3.5 V, 4 V, 4.5 V, or 5 V may be applied to the electrodes to generate an electric field.

[0095] In some instances, the electric field is above the top surface of the membrane filter, and the components of the mixed solution must pass through the electric field before reaching the membrane filter. In this example of electrofiltration (Figure 9A), some components with a higher charge are retained in the electric field, while other components with a lower charge are able to pass through the field and enter the pores of the membrane filter. In some instances, the membrane filter may be held at a constant potential with little current passing through it to apply the electric field.

[0096] In another example, the membrane filter may be charged for an electroextraction configuration (FIG. 9B). In this configuration, some components will adhere to and be retained in the charged membrane filter, while other components will pass through the pores of the membrane filter. In some embodiments, in the electroextraction configuration, a consistent current flow at a particular potential can reduce the target component ions.

[0097] In other examples, no charge may be applied and the membrane filter may be used to separate components by their size or other characteristics without the use of an electric field.

[0098] Block 408 or 458, which includes passing the mixed solution through a membrane nanofilter system, functions to perform filtration / separation of the mixed solution. The performance of block 408 or 458 can be highly dependent on the content of the mixed solution, the compounds desired for filtration, and the type of membrane nanofilter system used. Driving the mixed solution through membrane nanofilter system 408 can consist of either passive driving (e.g., simple diffusion, or directed diffusion such as by a concentration gradient) or active driving (e.g., a pump to generate flow). In an active driving variation, driving the mixed solution may consist of setting a flow rate (e.g., solution [volume] flow rate or material [mass] flow rate). In a solution flow rate variation, the solution flow rate through the membrane can be between 0.1 and 200 [L / (m 2hr)]. In some embodiments, the solution flow rate may be lower or higher. In the variation of the material flow rate, the material flow rate is between 1.0 and 1000 [g / (m 2 hr). In some variations, the material flow rate may be lower or higher.

[0099] In some variations, the feeding of the mixed solution may include multiple stages. The feeding of the mixed solution may be used in combination with an electric field to control the separation of components from the mixed solution. In one example, when lithium (Li) is filtered through a silicon (Si)-based membrane nanofilter system, an initial driving charge force is initiated, allowing Li to pass through the pores of the Si membrane filter while the other components of the mixed solution are attracted to the surface of the Si membrane filter. Once the permeate solution containing Li has passed through, the feed is switched to a pure draw solution (water or sulfuric acid), changing the polarity of the membrane filter and releasing the other components. The components then diffuse out of the membrane filter and are either collected by the pure draw solution (water, pure acid, or dilute acid) or driven to be collected by other flows (e.g., pumps). In other embodiments, Li is the component retained in the membrane filter and the other components pass through the membrane filter.

[0100] In active filtration type embodiments of the method, the supply of the mixed solution may include a unidirectional flow in which the mixed solution is driven through or across the membrane filter. In the case of saturated filtration, this is generally not the case. In saturated filtration, passive forces (e.g., simple or directional diffusion), such as concentration gradients, pH gradients, charge gradients, etc., may be more commonly implemented. In general, active and saturated filtration can incorporate unidirectional, multidirectional, or non-biased diffusion, as desired.

[0101] In some variations, the mixed solution is not fed through the membrane filter, but instead is fed along the membrane filter, or only partially against the membrane filter. That is, the mixed solution is fed parallel, adjacent to the membrane, or partially at an angle, so that the mixed solution is fed against and along the membrane filter. In such "cross-flow" variations, components of the mixed solution that can pass through the membrane can pass, while the mixed solution itself, including components that cannot pass through the membrane, continues to exit. Cross-flow variations can implement passive and / or active transport. In purely passive embodiments, the membrane nanofilter system is pre-saturated with the solution, and a counterflow of the draw solution on the permeate side of the membrane can be used to maintain a concentration gradient.

[0102] In general, the supply of the mixed solution 408 or 458 can include any type of driving force that is desired and applicable to the implementation. As previously mentioned, the supply of the mixed solution 408 or 458 can be at least somewhat dependent on the filtration type. For a particular type of filtration, there can be several preferred methods for supplying the mixed solution 408 or 458. For example, the supply of the mixed solution 408 or 458 can include forming a pH or concentration gradient driven, or a pressure driven flow. In the case of membrane interaction (e.g., selective absorption, adsorption, or ion exchange) filtration, the supply of the mixed solution 408 or 458 can include chemically driving the flow. In one embodiment, for Li interaction with the Si membrane, a redox reaction can be initiated to drive the flow by improving the Li-Si interaction, whereby Li is reduced at the pore walls and adsorbed into the bulk Si lattice.

[0103] For variations that require the filtration membrane to first be saturated with a liquid prior to the separation process, the method can include saturating the membrane nanofilter system with the mixed solution. Saturating the membrane nanofilter system with the mixed solution serves to set up a saturated filtration process. Saturating the membrane nanofilter system with the mixed solution can include leaving the membrane nanofilter system in the mixed solution or a pure solvent (water or a pure acid solution) for an allotted time. In another example, the pure solvent (water or a pure acid solution) is actively driven (e.g., via pressure-driven flow) through the membrane until the membrane is saturated. In another example, if the membrane pore size is too small to be directly saturated with an aqueous solution due to surface tension, a sequential approach can be used in which the pore structure is first saturated with a low surface tension organic solvent or supercritical CO2, and then replaced with a pure aqueous solution. In some implementations, the mixed solution can be heated, mixed, or agitated in some way to improve saturation. An example would be to saturate the membrane with water vapor at a temperature above the boiling point of water, possibly driving it under pressure, and then lowering the temperature to promote precipitation of pure water within the membrane's pore structure. In some variations where the membrane nanofilter system reacts with compounds in a mixed solution, an electrical charge can be passed through the solution to also promote saturation of the membrane.

[0104] FIG. 9B further includes feeding 460 the pure draw solution through a membrane filter, reversing 462 the current driven to the membrane filter for electrochemical oxidation, and recovering 464 the components of the mixed solution in the pure draw solution. For example, one or more components retained in the membrane filter can be eluted by the pure draw stream into the pure product stream after the current is reversed. In some examples, the pure draw solution includes, but is not limited to, water or sulfuric acid. The pure draw solution can have a volume of 1%-5%, 5%-10%, 10%-20%, 20%-30%, 30%-40%, or 40%-50% of the mixed solution volume. By reducing the volume of the pure draw solution in this manner, a concentrated pure product stream (e.g., a concentrated solution of one or more components of the mixed solution) can be formed.

[0105] 10 shows an exemplary multi-step process 500 for hydrometallurgical separation from a mixed solution via a membrane nanofilter with recycle. The process 500 can utilize multiple membrane filter modules in various combinations. The membrane filter modules can utilize electrofiltration, electroextraction, or a combination thereof.

[0106] In this process 500, ground battery powder can be combined with sulfuric acid to obtain a mixed solution 502. The mixed solution can then be filtered through a mesh for coarse filtration 504 to remove solids from the mixed solution. The mixed solution can then enter a concentration loop 506 where the mixed solution can enter an electric filter module 508 containing a lithium permeable membrane. The permeate solution from the electric filter module 508 contains the lithium that passed through the membrane filter. The permeate solution can then be mixed with a precipitation reagent to precipitate lithium carbonate or lithium hydroxide 510. At least a portion of the sulfuric acid remaining after precipitation can be recycled 511 back to the beginning of the process.

[0107] The remaining mixed solution that did not pass through the membrane filters of the electrofilter modules enters one or more electroextraction modules 512 to remove other components of the remaining mixed solution. The electroextraction modules 512 remove metals that may plate / attach to the membrane filters by recovering a second permeate solution 514 containing the non-plated / non-attached metals. The components in the second permeate solution can then be purified. The plated metals on the membrane filters can be periodically removed into the draw solution (water or sulfuric acid) 516 after reversing the polarity of the electric field, possibly at concentrations as high as the saturation point in the solution. For example, an electroextraction module can remove metals (iron, copper, etc.) below the potential of cobalt and nickel. In another example, a cascade of electroextraction modules may be used to separate the mixed solution into multiple pure solutions, with a first solution containing lower value Fe, Mn, Cu, a second solution containing Co and Ni, and a third solution containing Li and Al. A pure stream of Li can then be separated by electrofiltration.

[0108] The residual solution (including components not removed in the electroextraction module) may then pass through an additional electroextraction module 518 configured to remove remaining components from the residual solution. For example, the additional electroextraction module may be configured to remove cobalt and nickel and exit the additional electroextraction module with a third permeate solution 520. As with the other electroextraction modules, the draw solution may be passed through an electroextraction module 522 for periodic removal of plating metals after reversing the polarity of the electric field. The permeate solution 520 exiting the additional electroextraction module may then be mixed with a precipitating reagent 524 to precipitate components 526 in the second permeate solution. For example, cobalt sulfate and nickel sulfate may be precipitated from the solution. The sulfuric acid remaining after precipitation may be recycled 528 back to the beginning of the process. The remaining mixed solution is discharged from the system as waste 530.

[0109] FIG. 11 shows an exemplary process 600 for separation of conductive membrane filters from a mixed solution by a membrane nanofilter with recycling. In this process 600, ground battery powder can be combined with sulfuric acid to obtain a mixed solution 602. The mixed solution is then filtered through a coarse filtration mesh 604 to remove solids from the mixed solution. The mixed solution can then enter an electroextraction module 612. The permeate solution of the electroextraction module 612 contains the components that passed through the membrane filter (e.g., the desired metals to be extracted). The permeate solution 516 can be a pure solution of the extracted metals that is close to saturation. The permeate solution can then be mixed 617 with a precipitation reagent to precipitate a pure solid product 610. At least a portion of the sulfuric acid remaining after precipitation can be recycled 611 back to the beginning of the process. The plated metal on the membrane filter can be periodically removed into the draw solution (water or sulfuric acid) 614 after reversing the polarity of the electric field. The remaining mixed solution can be recycled to the beginning 513 of the process.

[0110] definition As used herein, the term "about" is used to provide flexibility to the endpoints of a numerical range by providing that a given value may be "a little above" or "a little below" the endpoint. For example, the endpoint may be within 10%, 8%, 5%, 3%, 2%, or 1% of the stated value. Furthermore, for convenience and simplicity, a numerical range of "about 50 mg / mL to about 80 mg / mL" should also be understood to support the range "50 mg / mL to 80 mg / mL". The endpoints may also be based on the variability allowed by appropriate regulatory agencies, such as the FDA, USP, etc.

[0111] As used herein, "comprises," "comprising," "containing," "having," and the like, can have the meanings given to them in U.S. Patent Law, and can mean "includes," "including," and the like, and are generally construed as open-ended terms. The terms "consisting" or "consisting of" are closed terms and include only those components, structures, steps specifically recited with the term, as well as those pursuant to U.S. Patent Law. "Consisting essentially of" or "consists essentially of" have the meanings generally given by U.S. Patent Law. In particular, such terms are generally closed terms, with the exception of permitting the inclusion of additional items, materials, components, steps, or elements that do not materially affect the basic and novel characteristics or functions of the item in connection therewith. For example, minor elements that are present in a composition but do not affect the properties or characteristics of the composition are permissible if present under the term "consisting essentially of" even if they are not explicitly set forth in the list of items following such a term. When open-ended terms such as "comprising" or "including" are used herein, it is understood that direct support should be given not only to the "consisting essentially of" language, but also to the "consisting of" language as if explicitly set forth, and vice versa.

[0112] As used herein, first, second, third, etc. are used to characterize and distinguish various elements, components, regions, layers, and / or sections. These elements, components, regions, layers, and / or sections should not be limited by these terms. The use of numerical terms may be used to distinguish one element, component, region, layer, and / or section from other elements, components, regions, layers, and / or sections. The use of such numerical terms does not imply a sequence or order unless clearly indicated by the context. Such numerical references may be used interchangeably without departing from the teachings of the embodiments and variations herein.

[0113] As used herein, the terms "membrane filter" and "wafer" can be used interchangeably to refer to a nanoporous filter as described herein.

[0114] As used herein, the terms "battery leachate," "black mass leachate," "mixed solution," and "feed solution" may be used interchangeably to refer to the solutions entering the membrane filter system.

[0115] As used herein, the terms "compound" and "component" are used to refer to any type of material without loss of generality to the material in question, i.e., a compound may refer to any element, ion, molecule, complex structure, or combination thereof (e.g., metal oxide, metal sulfide).

[0116] Working Example An example system with a silicon membrane filter in a pressure cell was tested to verify the current passing from the electrical contacts to the membrane filter. Figure 5H shows a pogo pin inserted through a port in the pressure cell to make electrical contact with the inner surface of the silicon membrane, mounted within the cell, and a meter probe placed on the unpolished back side of the silicon membrane. The contact resistance on the unpolished side was assumed to be low. The membrane filter was compressed onto the pogo pin up to the O-ring. Resistance was measured at 23-130 ohms with a 0.4' maximum compression pin and 1103-1771 ohms with a 0.25' maximum compression pin.

[0117] In another instance, the resistance of the electrical contacts was approximately 1000 ohms. The pressure cell was pressurized to 700 psi and held at that pressure for 45 minutes without any significant leakage or cracking of the wafer. Pressurization was repeated with the same wafer and three times with different wafers. Pressurization was held for approximately five minutes.

[0118] Figure 12 shows the results of an example of electrofiltration. Water was placed in a filtration cell equipped with a silicon membrane filter with pore size of approximately 100 nm and low pressure (50 psi). After a liquid bridge formed on both sides of the membrane, the pressure was stopped and MgSO4 was added to one side of the membrane to evaluate diffusive transport in no-flow conditions. The diffusion of MgSO4 across the membrane was then measured. Figure 12 shows the difference in the flow of MgSO4 through the membrane by conductivity measurements over time when the membrane is charged (1 V) and uncharged (0 V). Diffusion-based (non-pressurized flow) filtration experiments with MgSO4 showed that the ability of salt to pass through the membrane was significantly reduced when an electric field was applied.

[0119] As will be appreciated from the foregoing detailed description, and from the figures and claims, those skilled in the art can make modifications and variations to the embodiments of the invention without departing from the scope of the invention, which is defined in the following claims.

Claims

**Claim 1** A membrane nanofilter system for conductive membrane separation, comprising: A membrane filter comprising a nanoporous structure; An electrical contact in contact with the membrane filter; and A counter electrode above the upper surface of the membrane electrode; The membrane filter and the counter electrode via the electrical contact are configured to generate an electric field between the membrane filter and the counter electrode, to hold the membrane filter at a constant potential, or to pass a constant current through the membrane filter; The membrane filter is configured to separate components from a mixed solution into a permeate solution, and The membrane filter contains silicon, the system. **Claim 2** The system according to claim 1, wherein the components of the mixed solution are selected from the group consisting of Co, Ni, Al, Mn, Fe, Li, Cu, Ag, Zn, graphite, F, P, their ions, or mixtures thereof. **Claim 3** The system according to claim 1 or 2, wherein the mixed solution contains an acid and the pH of the mixed solution is less than 4.

0. **Claim 4** The system according to claim 1, further comprising one or more additional membrane filters, wherein the residual solution passes through one or more additional membrane filters to separate one or more additional components of the mixed solution. **Claim 5** The system according to claim 1, wherein the system is configured for electrofiltration and an electric field is applied between the membrane filter and the counter electrode. **Claim 6** The system according to claim 5, wherein the membrane filter has a pore size of 1 nm to 100 nm. **Claim 7** The system according to claim 1, wherein the system is configured for electroextraction and the membrane filter is held at a constant potential or a constant current is passed through the membrane filter. **Claim 8** The system according to claim 1, wherein the system is configured for selective filtration of size and charge. **Claim 9** A method for separating a conductive membrane from a mixed solution, comprising: A membrane filter comprising a silicon nanoporous structure; An electrical contact in contact with the membrane filter; and A counter electrode above the upper surface of the membrane filter; Providing a membrane nanofilter system comprising Generating an electric field above or inside the membrane filter, maintaining the membrane filter at a constant potential, or passing a constant current through the membrane filter; Passing the mixed solution through the membrane filter; and Separating components from the mixed solution into the permeate solution, a method comprising.

10. The method according to claim 9, wherein the components of the mixed solution are selected from the group consisting of ions of Co, Ni, Al, Mn, Fe, Li, Cu, Ag, Zn, graphite, F, P, those ions, or mixtures thereof.

11. The method according to claim 9 or 10, wherein the mixed solution contains an acid and the pH of the mixed solution is less than 4.

0.

12. Removing a residual solution containing components not contained in the permeate solution; Recycling the residual solution to the mixed solution; and Separating a second component from the recycled mixed solution; The method according to claim 9, further comprising.

13. The electric field is configured to separate components with lower charges into the permeate solution and components with higher charges into the residual solution, or The permeate solution contains components having an ionic charge of 1+ or less, and the residual solution contains components having an ionic charge of 2+ or more, the method according to claim 9.

14. The method according to claim 9, wherein the components are separated from the mixed solution via electrofiltration and the electric field is applied between the membrane filter and the counter electrode.

15. The components are separated from the mixed solution by electroextraction, the membrane filter is maintained at a constant potential, or a constant current is passed through the membrane filter, and Optionally, one or more components of the mixed solution not present in the permeate solution are retained within the pores of the membrane filter, the method according to claim 9.

16. The method according to claim 15, further comprising reversing the polarity of the potential or the direction of the current and passing a pure draw solution through the membrane filter, the pure draw solution containing water or sulfuric acid.

17. Leaching one or more components retained on the membrane filter into a pure draw solution and a pure product stream containing one or more components; and precipitating one or more components from the pure product stream; the method according to claim 16, wherein the pure draw solution has a volume of 1% to 50% of the volume of the mixed solution.

18. The method according to claim 9, further comprising adjusting an electric field strength or polarity to select a desired component.

19. The method according to claim 9, wherein the electric field is orthogonal or perpendicular to the membrane filter.

20. The mixed solution comprises a monovalent ion component and a polyvalent ion component; and The monovalent ion component and the polyvalent ion component are filtered to be different based on their charges, according to the method of claim 9.

21. The method according to claim 20, further comprising separating a monovalent ion component or a polyvalent ion component.

Images