Reverse electroosmosis filtration with nanofluid transport through asymmetric membranes

Abstract

The present invention relates to a method of purifying an electrolyte solution, the method comprising applying an alternating electric field between a first electrode and a second electrode, thereby enabling solvent transfer and solute filtration through an asymmetric membrane. The invention also relates to a system for purifying the electrolyte solution by adopting the method.

Description

Technical Field

[0001] The present invention relates to a continuous method for purifying an electrolyte solution, comprising applying an alternating electric field between a first electrode and a second electrode, thereby achieving solvent transfer and solute filtration through an asymmetric membrane. The present invention also relates to a system for purifying an electrolyte solution using the method.

[0002] References in square brackets [X] refer to the reference list at the end of the Examples. Background Art

[0003] The water needs of the global population are a major issue in the ecological transition. In fact, climate change, population growth and the rise of developing countries are making these needs increasingly important, making access to water a key element of the future of our modern society.

[0004] The ocean represents a vast source of water that could potentially be tapped to meet this demand, provided it can be desalinated in a cost-effective, clean, and sustainable manner. On the other hand, non-saline water sources such as rivers contain micropollutants even after conventional treatment. Furthermore, water purification has important applications in hydrogen production via electrolysis, which requires pure water.

[0005] Many technologies have been developed for filtering pollutants and desalination. Reverse osmosis (RO) is one of the most widely deployed technologies for water treatment [1][2]. Other methods such as capacitive deionization or electrodialysis have also made significant progress in the past few decades. However, these different methods have several problems that have limited their large-scale deployment [3][4][5].

[0006] The efficiency of the membranes used in these different technologies plays an important role in the performance of the processes. In recent decades, new materials have been developed to optimize water transport while maintaining important sieving properties [6]. The properties of the material and its structure are important parameters for optimizing its performance. The emergence of two-dimensional (2D) materials such as graphene oxide or MoS2 has improved the water transport properties for filtration and desalination [7][8]. In addition, understanding the fundamental phenomena occurring at the nanoscale opens the possibility of developing macroscopic materials with unique transport properties, which may provide new perspectives for desalination, filtration and energy harvesting. However, the manufacture of optimized nanostructured materials with long cycle life remains complex, expensive and therefore a very important challenge.

[0007] Some technologies, such as the invention disclosed in patent application EP3862069, show that water purification and desalination using electroosmotic driving forces can be achieved at reasonable voltages comparable to standard pressure-driven technologies. However, macroscopic membranes and capacitive electrodes operating under electrostatic drive are known to suffer from polarization effects, resulting in a sharp drop in performance in a relatively short period of time. In fact, the accumulation of charge on both sides of the membrane and at the electrode / electrolyte interface leads to a reverse potential that offsets the overall electroosmotic (EO) driving force. Although this parasitic effect can be suppressed by conventional techniques (such as systematically short-circuiting the electrodes during operation to reset the electrostatic environment), the overall performance of the method is limited, which hinders the application of the technology outside the laboratory.

[0008] In the process of seeking to solve the various technical problems associated with the prior art, the applicant surprisingly discovered a new water treatment technology based on electroosmotic flow (EO flow), in which continuous transport of water through a selective membrane is maintained by applying an external alternating current (AC) voltage across the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 (a) schematically illustrates an exemplary system according to the present invention involving a composite asymmetric membrane element 30.

[0010] Figure 1 (b) schematically illustrates an exemplary system according to the present invention involving an asymmetric membrane element 30 comprising a single material.

[0011] Figure 1 (c) schematically illustrates an exemplary system according to the present invention involving an asymmetric membrane element 30 comprising two materials.

[0012] Figure 2 An exemplary system according to the present invention is schematically shown, which also includes a rubber flat washer 80A and a rubber O-ring seal 80B.

[0013] Figure 3 (a) The composite asymmetric membrane is shown in photographic form.

[0014] Figure 3 (b) shows a scanning electron microscope (SEM) cross-sectional image of the two-dimensional layered film.

[0015] Figure 4 X-ray diffraction patterns of GO and MoS2 multilayer films are shown, revealing interlayer spacings of 0.83 nm and 0.62 nm, respectively.

[0016] Figure 5(a) shows a graph containing the measured flow rates for EO-driven and pressure-driven experiments of an asymmetric membrane with a charged sub-membrane of polycarbonate (PC) and a semipermeable sub-membrane of MoS2.

[0017] Figure 5(b) schematically shows the structure of two stacked MoS2 monolayers (where a central molybdenum atomic layer is sandwiched between two sulfur atomic layers).

[0018] FIG5( c ) schematically shows the structure of a single-layer graphene oxide.

[0019] Figure 5(d) shows a graph containing the measured flow rates for EO-driven and pressure-driven experiments of an asymmetric membrane having a charged sub-membrane of polycarbonate (PC) and a semipermeable sub-membrane of GO.

[11]

[0020] Figure 6(a) shows the IV response of the system for the following conditions: electrode, PC membrane, and asymmetric membrane (PC+GO & PC+MoS2). It shows the ion current for different configurations under voltage drop: the cell without membrane and the cell with bare supported PC membrane (symmetric) show a completely symmetric response, with no difference in ion current under positive and negative voltages. On the other hand, the composite membrane is characterized by a larger current for ion transport under negative voltage than under positive driving force (this asymmetry can be reversed by changing the orientation of the composite membrane relative to the ground electrode). The asymmetry in ion transport is then converted into an asymmetry in EO water transport, resulting in an asymmetric induced water flux.

[0021] Figure 6(b) shows the EO flow and current dynamic response of the asymmetric membrane under an alternating electric field (amplitude: 10 V, frequency: 2.5 Hz). It shows the measured dynamic response of the composite membrane's current and flow rate under an alternating voltage. The reported EO flow rate is highly asymmetric, resulting in a net transport of water from one side of the membrane to the other.

[0022] FIG6( c ) shows the evolution of the net volume of permeate passing through the asymmetric membrane at several frequencies (amplitude: 10 V).

[0023] Figure 7 An example of a container 40A or 40B is schematically shown, which includes a wall 401 and an outlet tube 402 divided into two parts; a tubular sub-container 402A and a hyperbolic sub-container 402B, where the tube diameter is w, the larger opening dimension of the hyperbolic sub-container is y, the narrower opening dimension of the hyperbolic sub-container is x, and the height dimension of the hyperbolic sub-container is z.

[0024] Figure 8The measured rejection rates of micropollutants (acetaminophen, caffeine, and rhodamine) by PC+GO and PC+MoS2 membranes are shown, along with their molecular structures.

[0025] Figure 9 The evolution of the net volume of permeate through the asymmetric membrane obtained by pressure-assisted reverse electroosmotic filtration for different pressure inputs in Example 5 is shown. The experiments were performed on a PC+GO membrane at a frequency of 2.5 Hz and different voltage and pressure inputs.

[0026] definition

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Generally, the nomenclature used herein and the experimental procedures to be described below are well known and commonly used in the art.

[0028] To facilitate understanding of the present invention, a number of terms and phrases are defined below:

[0029] In this document, except in the claims, the terms "a", "an", "the" and / or "said" mean one or more. When used in the claims, when used in conjunction with the words "comprising", "containing" and / or "comprising", the words "a", "an", "the" and / or "said" may mean one or more than one. In this document and in the claims, the terms "have", "have", "is", "include", and / or "include" have the same meanings as "containing", "including" and "comprising". In this document and in the claims, "another" may mean at least a second or more. In this document and in the claims, "about" refers to any inherent measurement error or numerical rounding of a value (e.g., a measurement, a calculation such as a ratio), so the term "about" may be used with any value and / or range.

[0030] The phrases "combinations thereof," "mixtures thereof," and similar expressions following a list, the use of "and / or" as part of a list, a list in a table, the use of "etc." as part of a list, the phrase "for example," and / or a list with "for example" or "i.e." in parentheses, refer to any combination (for example, any subset) of the listed set of components, and combinations and / or mixtures of related species and / or embodiments described herein that are not directly placed in such a list are also contemplated. Such related and / or similar genera, subgenera, species, and / or embodiments described herein are contemplated both as individual components that may be claimed and as mixtures and / or combinations that may be described in the claims as "at least one selected from," "mixtures thereof," and / or "combinations thereof."

[0031] The term "and / or" as used herein means any one, any combination of the items, or all of the items associated with the term.

[0032] Those skilled in the art will understand that all numbers, including those representing quantities of ingredients, properties such as cavity / pore size and zeta potential, experimental conditions, etc., are approximate and are understood to be optionally modified in all instances by the term "about." These values ​​can vary depending on the desired properties sought to be obtained by one skilled in the art utilizing the teachings described herein. It is also understood that such values ​​inherently contain variability necessarily resulting from the standard deviation in their respective testing measurements.

[0033] As used herein, the term "about" may refer to a variation of ±5% of a specified value. For example, "about 50%" may, in some embodiments, encompass a variation from 45% to 55%. For integer ranges, the term "about" may include one or both integers greater than and / or less than the recited integer. Unless otherwise indicated herein, the term "about" is intended to include adjacent values, such as concentration values, that are functionally equivalent to the recited range for individual components, compositions, or embodiments.

[0034] It will be understood by those skilled in the art that for any and all purposes, particularly in providing a written description, all ranges listed herein also encompass any and all possible subranges and combinations thereof, as well as the individual values, particularly integer values, that constitute the range. A listed range includes each specific value, integer, decimal, or identifier within the range. Any listed range can be easily identified as sufficient to describe and enable the same range to be decomposed into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be easily decomposed into a lower third, a middle third, and an upper third, etc. DETAILED DESCRIPTION

[0035] The system and method according to the present invention overcome one or more of the above-mentioned problems commonly associated with conventional membrane technologies and methods. Specifically, the system of the present invention uses a reverse electroosmotic filtration system. This system and its other unique features will be discussed below and shown in the accompanying drawings.

[0036] It should be understood that the various components, parts and features of the different embodiments can be combined and / or interchanged with each other, all of which are within the scope of the present invention, even if not all variations and specific embodiments are shown in the drawings. It should also be understood that the mixing and matching of features, elements and / or functions between different embodiments is expressly contemplated herein, so that those skilled in the art can understand from this disclosure that the features, elements and / or functions of one embodiment can be appropriately incorporated into another embodiment, unless otherwise described.

[0037] A first object of the present invention is a method for purifying an electrolyte solution, comprising the following steps: i) contacting a first volume V1 of a first electrolyte solution 11A comprising a solute and a solvent with a first porous electrode 20A; ii) contacting a second volume V2 of a second electrolyte solution 11B comprising a solvent with the second porous electrode 20B; iii) applying an alternating electric field between the first and second electrodes 20A and 20B to achieve solvent transfer and solute filtration through the membrane element 30, and the change in volume V2 (V2(nT)) is defined by the following formula (Formula 1): V2(nT)=μ EOeff ΔV eff πr 2 n TL -1 Where T is the period of the applied signal (s), n is the number of completed cycles, and μ EOeff is the effective electroosmotic mobility (m 2 ·V -1 ·s -1 ), ΔV eff is the local potential difference at the membrane (V), r is the average radius of the membrane pores (m); and L is the membrane thickness (m); iv) Exhaust bubbles generated during parasitic electrochemical reactions in, The first electrode 20A and the second electrode 20B are separated by an asymmetric membrane element 30 comprising a first side 30A and a second side 30B; The average pore size of the second side 30B of the asymmetric membrane element 30 is 1.1 to 10,000 times smaller than the average pore size of the first side 30A; The diaphragm 60 is positioned between the electrode 20A or 20B and the second side 30B of the asymmetric membrane element 30; The asymmetry between the first side and the second side of the membrane element 30 is a property of geometric, physicochemical, environmental properties, or a combination thereof; and First and second electrodes 20A and 20B are operatively coupled to power source 40 through two current collectors 70A and 70B.

[0038] Advantageously, the method according to the invention can be carried out in static mode or in tangential mode. Static mode means that no specific flow tangential to the membrane is generated. Tangential mode means that in addition to steps i) to iv) of the method according to the invention, a liquid flow flows tangentially to the membrane surface. Tangential mode limits membrane fouling. Tangential AC voltage reverse osmosis can be carried out in a co-current or cross-current configuration. The flow rate can be adjusted by the technician depending on the application and the fouling tendency of the membrane. The tangential flow can be generated by any pumping or vacuum system. For example, it can be a peristaltic pump, a diaphragm pump, a booster pump, a transfer pump or a vacuum pump. The speed of the tangential flow can be between 0.01 and 1000 m·s -1 between 0.1 and 100 m·s -1 between 1 and 100 m·s -1 between.

[0039] Advantageously, the method according to the present invention may further include a step v) of pressure-induced reverse osmosis. To implement step v), the first and second containers are pressure-sealed using appropriate valves corresponding to the applied pressure range. They may also preferably be connected to pressurized tanks for the feed and permeate solutions. Depending on the technique used to apply the mechanical pressure differential, the permeate chamber, the feed chamber, or both must be adapted. For example, the pressure differential can be generated by creating a pressure differential or a chemical gradient between the two containers. For example, the pressure differential can be generated using a pumping system or a vacuum system. For example, if a pump is used to create the pressure differential, the feed chamber must be pressure-tight and connected to the pump. As another example, if a vacuum is used to create the pressure differential, the permeate chamber must be pressure-tight and connected to a vacuum transfer unit. The chemical gradient can be imposed by a concentration gradient between the two electrolytes 11A and 11B. The pressure differential to be applied between the two containers depends on the initial concentration difference between the two electrolytes, the osmotic pressure to be overcome, the type of membrane element, and the desired flux of the purified liquid. For example, for seawater purification, the applied pressure gradient can be between 0.1 and 150 bar, preferably between 30 and 130 bar. The change in volume V2 (V2(nT)) is due to electroosmosis in step iii). Step v) also has an effect on the change in volume V2. The volume change caused by step v) and pressure-induced reverse osmosis is V 2P =K m dPt.

[0040] Steps iii) and v) can be performed sequentially or simultaneously. When steps iii) and v) are performed simultaneously, the total volume change is the volume increase V2 (nT) due to electroosmosis. EO and the volume increase V caused by pressure-induced reverse osmosis 2p The sum is as follows: V2=V2(nT) EO +V2P =μ EOeff ΔV eff πr 2 n TL -1 +K m dPt

[0041] Among them, V2 (nT) EO is the volume contribution due to electroosmotic filtration (m 3 ), V 2P is the volume contribution due to pressure-induced reverse osmosis (m 3 ), K m is the membrane permeability under pressure-induced reverse osmosis (m 3 ·h -1 bar -1 ), dP is the pressure difference between the first and second vessels (bar), and t is the filtration time (hours).

[0042] A second object of the present invention is a system for purifying an electrolyte solution, comprising: a first container 40A containing a first volume V1 of a first electrolyte solution 11A, the first electrolyte solution 11A comprising a solute and a solvent; a second container 40B containing a second volume V2 of a second electrolyte solution 11B, the second electrolyte solution 11B comprising a solvent; - a first electrode 20A in contact with the first electrolyte solution 11A; - a second electrode 20B in contact with the second electrolyte solution 11B; - an asymmetric membrane element 30 comprising a first side 30A and a second side 30B; a membrane 60 positioned between the electrode 20A or 20B and the second side 30B of the asymmetric membrane element 30 ; and - two current collectors 70A and 70B operatively coupling the first and second electrodes 20A and 20B to the power source 40; in, - the first and second containers 40A and 40B are configured to discharge bubbles generated during the parasitic electrochemical reaction by the Venturi effect; - the first and second electrodes 20A and 20B are porous electrodes, grid electrodes or electrodes of any geometry through which the electrolyte can diffuse; The asymmetric membrane element 30 has an asymmetry in geometric, physicochemical, environmental properties, or a combination thereof, between the first side and the second side of the membrane element 30 ; The average pore size of the second side 30B of the asymmetric membrane element 30 is 1.1 to 10,000 times smaller than the average pore size of the first side 30A.

[0043] Advantageously, the first and second electrodes 20A and 20B can be operatively coupled to the power source 40 via the two current collectors 70A and 70B so that an alternating electric field can be applied between the first and second electrodes 20A and 20B (e.g., the power source 40 allows an alternating electric field to be applied between the first and second electrodes 20A and 20B).

[0044] As used herein, the term "solute" refers to a liquid or solid material dissolved in the solvent used in electrolyte solution 11A and / or 11B. Solid solutes can be selected from solid particles, organic or inorganic small molecules such as dye complexes (e.g., tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate), biomolecules such as hormones (e.g., testosterone), proteins, polysaccharides, polynucleotides, polypeptides, enzymes or antibodies, perfluoro and polyfluoroalkyl substances (e.g., from wastewater, industrial process water or landfill leachate), metabolic waste products or salts / ions (e.g., NaCl, LiCl, Na2SO4). Liquid solutes can be organic acids (e.g., acetic acid, propionic acid, butyric acid, lactic acid, succinic acid, boric acid, etc.), alcohols (e.g., ethanol, butanol, etc.) or hexane.

[0045] The term "VIRO" as used herein refers to "Voltage Induced Reverse Osmosis".

[0046] The term "membrane element" as used herein, as it is commonly understood in the field of filtration membranes, refers to a membrane that allows certain molecules or ions to pass through it by diffusion, osmosis, or artificially generated flux. For example, it can be a size exclusion membrane, an ion exchange membrane, or any other membrane that allows the separation / filtration of specific molecules or ions from a given electrolyte solution.

[0047] As used herein, the term "electrolyte solution" refers to an electrically conductive solution containing mobile ions, such as ions derived from dissolved salts (eg, NaCl, KCl, CaCl2, or MgCl2), which cause electroosmosis.

[0048] As used herein, "zeta potential," when referring to the surface charge of a membrane, does not deviate from its conventional meaning in electrochemistry, which refers to the potential difference between the membrane surface and the stationary layer of fluid attached to the membrane surface. The zeta potential generally depends on the properties of the membrane surface and the characteristics of the electrolyte solution in contact with the membrane surface (e.g., pH, ion concentration, ionic strength, etc.). The zeta potential can be calculated using the Smoluchowski equation (see Equation 1 below).

[0049] As used herein, "|zeta potential|" refers to the absolute value of the zeta potential (i.e., the numerical value of the zeta potential without regard to its sign). It will be readily understood from this disclosure that the present invention can be performed using charged sub-membrane elements with either negative or positive surface charges: once the membrane is in contact with the electrolyte solution, the zeta potential can be negative or positive, respectively.

[0050] The asymmetric membrane element 30 may comprise a composite material with different properties for each element of the composite, an assembly of two materials having the same properties but differing in at least one inherent property, or a single material with at least one inherent property differing on either side.

[0051] Advantageously, the average pore size of the second side 30B of the asymmetric membrane element 30 may be 1.1 to 10,000 times smaller than the average pore size of the first side 30A, preferably 100 to 5,000 times smaller, more preferably 500 to 2,000 times smaller.

[0052] The permeate, from which the rejected solutes have been removed, will exit the asymmetric membrane element 30 as a permeate stream and may be collected in vessel 40B.

[0053] In one variant, the second side (30B) of the asymmetric membrane element (30) is in contact with a second electrolyte solution 11B comprising a solvent.

[0054] In a second variant, the second side (30B) of the asymmetric membrane element (30) is in contact with a first electrolyte solution 11A comprising a solvent.

[0055] Advantageously, the membrane can be oriented so that the change in volume V2 (V2(nT)) can be defined by the following formula (Formula 1): V2(nT)=μ EOeff ΔV eff πr 2 n TL -1

[0056] The change in volume V1 (V1(nT)) can be defined by the following formula (Formula II): V1(nT)=-μ EOeff ΔV eff πr 2 n TL -1

[0057] Where T is the period of the applied signal (s), n is the number of completed cycles, and μ EOeff is the effective electroosmotic mobility (m 2 ·V -1 ·s -1 ), ΔV effis the local potential difference at the membrane (V), r is the average radius of the membrane pores (m); and L is the membrane thickness (m);

[0058] In both formulas, μ EOeff and ΔV eff are strictly positive and frequency dependent. In addition, r can be calculated from the average value of the total pore radius.

[0059] Those skilled in the art will know how to adjust the orientation of the asymmetric membrane according to the above calculation results of V2(nT) or V1(nT) depending on the asymmetry type of the membrane.

[0060] 1. Composite asymmetric membrane

[0061] An exemplary embodiment is Figure 1 .a is shown.

[0062] In one variation, the first side 30A of the asymmetric membrane element 30 comprises a semi-permeable sub-membrane, while the second side 30B of the asymmetric membrane element 30 comprises a charged sub-membrane.

[0063] 1.1 Semipermeable membrane

[0064] The semipermeable membrane that can be used in the context of the present invention may be any semipermeable membrane known in the art.

[0065] Advantageously, the semipermeable membrane element 30A can be a size exclusion membrane, an ion exchange membrane, or any other membrane that allows separation / filtration of specific molecules or ions from a given electrolyte solution (e.g., a semipermeable membrane based on chemical affinity separation), advantageously a size exclusion membrane or an ion exchange membrane. For example, it can be a semipermeable membrane that separates pure water molecules from salts and other impurities: that is, a membrane that is permeable to water but relatively impermeable to various dissolved impurities (including dissolved salts, organic matter, bacteria and pyrogens and other small molecules). Therefore, it can be a semipermeable membrane conventionally used in water purification technology, which uses a semipermeable membrane to remove ions, molecules and larger particles from contaminated water. It can also be a semipermeable membrane used in water purification or desalination systems, reverse osmosis systems, such as thin film composite membranes (TFC or TFM). The membrane used for reverse osmosis is usually made of polyamide, mainly selected for its permeability to water and relative impermeability to various dissolved impurities including salt ions and other small molecules that cannot be filtered. In another example, the semipermeable membrane element 30A may be an anion exchange membrane (AEM) or a cation exchange membrane (CEM). For example, the semipermeable membrane element 30A may be a Nafion semipermeable membrane.

[0066] The average pore size of the semipermeable membrane will be adjusted to filter out the target solute from the electrolyte solution 11A. Therefore, the average pore size of the membrane will be small enough to prevent the target solute (and any other solutes with a particle size larger than the target solute) from passing through the semipermeable membrane 30A, while allowing the solvent and other smaller solutes to pass through the semipermeable membrane 30A. The average pore size of the semipermeable membrane will be adjusted according to the intended application type: microfiltration (50-500nm), ultrafiltration (1-50nm) or nanofiltration (≤1nm). Advantageously, the semipermeable membrane element 30A can have an average pore size of <500nm, preferably <300nm, more preferably <100nm, and most preferably <50nm. In a preferred variant, the filtration system is intended for ultrafiltration, and the semipermeable membrane element 30A can have an average pore size between 1-50nm. In another preferred variant, the filtration system is intended for nanofiltration, and the semipermeable membrane element 30A can have an average pore size of <1nm. Such a nanofiltration system can be used for desalination, for example.

[0067] Advantageously, the semipermeable membrane comprises a steric repulsion separation membrane, an electrostatic repulsion separation membrane, or a membrane capable of separating / filtering specific solid molecules or ions from a given electrolyte solution. More advantageously, the semipermeable membrane comprises a material selected from TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc) (dobdc is 1,4-dioxo-2,5-phthalate), cellulose, polyamide, composite membranes such as thin film composite (TFC) membranes, PTFE, polymer membranes of polyelectrolyte layers, metal sulfide compounds such as WS2, MoS2, WSe2 or GaSe, semimetals (e.g., WTa2, TcS2), metal organic framework membranes (MOFs), MXenes, biomimetic membranes (e.g., water channel proteins), any liquid membranes, carbon materials such as graphene oxide, graphene or graphite, superconductors (e.g., NbS2, TaSe2), topological insulators and thermoelectric materials (e.g., Bi2Se3, Bi2Te3), or the semipermeable membrane is an organic or inorganic filtration membrane, preferably a nanofiltration, ultrafiltration or reverse osmosis membrane.

[0068] All of these materials can exhibit similar selective permeation properties and can be used as molecular sieves in applications involving membrane separations, such as nanofiltration, desalination, etc.

[0069] Carbon nanotube membranes (carbon materials) are composed of perforated graphene sheets connected by two short carbon nanotubes of a determined diameter. However, their practical applications are limited due to the complexity of their manufacture. Nanoporous graphene membranes are composed of single-layer graphene with nanopores of a determined size. However, it is still difficult to obtain large graphene sheets with a predetermined pore size and a high pore density. Graphene oxide (GO) membranes are composed of stacked GO nanosheets separated by interconnected nanochannels that form pores, allowing selective permeation through the membrane. They can be produced relatively easily and cheaply by depositing GO solutions onto various supports by spraying, dip coating, spin coating, vacuum filtration, etc., and are currently the most commonly used. In addition, GO sheets can be converted into graphene-like reduced GO (rGO) sheets, whose electrical, thermal, mechanical and surface properties are similar to those of original graphene.

[0070] Therefore, in the context of the present invention, the semipermeable membrane may be a carbon nanotube membrane, a nanoporous graphene membrane or a multilayer GO or rGO membrane, preferably a multilayer GO or rGO membrane, most preferably a multilayer GO membrane.

[0071] Advantageously, the semipermeable membrane 30A can be a size exclusion selective membrane composed of stacked graphene oxide flakes. Advantageously, the stacked graphene oxide flakes can form a two-dimensional nanochannel network, and the interlayer spacing between the GO flakes ranges from 0.7 to 1.4 nm. The interlayer spacing between the stacked graphene oxide flakes can be measured by any suitable method known in the art. For example, it can be measured using X-ray diffraction (XRD).

[0072] Advantageously, the pore size of the nanoporous carbon membrane may range from 0.7 nm to 1.5 nm, preferably ≤1.4 nm, more preferably ≤1.3 nm, still more preferably ≤1.1 nm, and even more preferably ≤1.0 nm. When referring to carbonaceous semipermeable membranes, "pore size" refers to the pore diameter in the case of carbon nanotube and nanoporous graphene membranes, and to the width of the interlayer gap in the case of multilayer GO or rGO membranes. Typically, the thickness of the nanoporous carbon membrane may be from 0.05 μm to 1 μm, preferably from 100 to 500 nm thick in the case of carbon nanotube membranes. In the case of multilayer GO or rGO membranes, the carbon membrane may comprise at least 2 layers, preferably at least 3 layers, up to 300 layers of GO or rGO sheets, and may be from 0.05 to 20 μm thick, for example from 0.05 to 15 μm thick, from 0.05 to 10 μm thick, from 0.05 to 5 μm thick, or from 0.05 to 1 μm thick. For example, the carbon film may be approximately 0.1 μm thick.

[0073] In another embodiment, the semipermeable membrane 30A can be a stack of layered materials. Any layered material can be used, for example, MoS2, hexagonal NiB, clay, or graphite systems.

[0074] For example, the semi-permeable membrane 30A may be a multi-layer MoS 2 film, a multi-layer hexagonal NiB film, or a multi-layer GO or rGO film, preferably a multi-layer GO or rGO film, and most preferably a multi-layer GO film.

[0075] In another exemplary variation, the semipermeable membrane 30A may be an ion exchange membrane, such as an anion exchange membrane (eg, OH-, Cl- transport) or a cation exchange membrane (eg, H + ,Na + ,K + transport).

[0076] The semipermeable membrane can be placed directly on the charged sub-membrane element 30B. This can be achieved, for example, by vacuum filtration, preferably under wet conditions (from a dispersion dispersed in water or an aqueous solvent). For example, a dispersion of a carbonaceous material (e.g., carbon nanotubes, graphene, GO or rGO) or a layered material (e.g., MoS2, hexagonal NiB, clay, MXene, MOF graphite system) in water can be added dropwise to the top of the charged sub-membrane 30B under vacuum. For example, the charged sub-membrane 30B can be placed on a Buchner funnel connected to a vacuum pump, and a dispersion of the carbonaceous material or layered material in water can be slowly (e.g., dropwise) added to the charged sub-membrane 30B to form a stacked membrane (semipermeable membrane element) of carbonaceous material or layered material.

[0077] Advantageously, the semipermeable membrane is preferably adapted to achieve a solute rejection of 98.0% or higher, preferably ≥98.5%, more preferably ≥99.0%, still more preferably ≥99.5%, most preferably 100% or about 100% solute rejection.

[0078] A person skilled in the art will know how to adapt the mean pore size of the semipermeable membrane according to the context of its use and according to the size of the solutes it has to filter.

[0079] 1.2 Charged electron membrane

[0080] The charged electronic membrane that can be used in the context of the present invention can be any charged membrane known in the art.

[0081] Advantageously, the charged sub-membrane comprises a material capable of generating electroosmotic flow or separating / filtering specific molecules or ions from a given electrolyte solution. More advantageously, the charged sub-membrane comprises a surface charge having a zeta potential greater than or equal to 5 mV, preferably greater than or equal to 20 mV, and more preferably greater than or equal to 50 mV.

[0082] In one variation, the charged sub-membrane can be a sub-membrane in which at least a portion of the inner surface of the nanochannel of the membrane is substantially formed of at least one material having a suitable surface charge. As used in the present invention, unless otherwise indicated, the term "substantially formed of" means a material "made of". The term also encompasses the possibility that the material may be optionally physically or chemically modified (e.g., on the surface and / or pore wall surface) to adjust its physicochemical properties to suit the intended use. Chemical modification can include doping (e.g., adding a metal element to the surface or core of the material network); coating (e.g., with a thin layer of a material having a suitable surface charge); covalent functionalization; physical adsorption or chemical adsorption of compounds / species by methods such as chemical vapor deposition, atomic layer deposition, sol-gel coating or dip coating, or electrochemical deposition; or ionization of ionizable functional groups on the surface of the material by pH changes.

[0083] In a preferred embodiment, at least a portion of the interior surface of the nanochannel is substantially formed or coated by at least one material having a suitable surface charge.

[0084] Advantageously, the nanochannels are preferably formed or coated entirely of at least one material having a suitable surface charge.

[0085] As used herein, "at least a portion of the inner surface of a nanochannel" means that the inner surface of the nanochannel may include one or more portions substantially formed from a material having a suitable surface charge, or the entire inner surface may be substantially formed from at least one material having a suitable surface charge. The portions may be regular or irregular, intermittent or non-intermittent, and / or exist in the form of a single layer or multiple layers. Preferably, the entire inner surface of the nanochannel is substantially formed from at least one material having a suitable surface charge.

[0086] Charged sub-membranes that can be used in the context of the present invention may have a positive or negative surface charge.

[0087] When the charged sub-membrane has a positive surface charge, an alternating electric field is applied between electrodes 20A and 20B, where electrode 20B, which is in contact with electrolyte solution 11B in second container 10B, is positively charged. This induces anions in electrolyte solution 11B to flow from the positively charged pore surfaces of charged sub-membrane element 30B to electrode 20B. This anion flow simultaneously induces solvent to flow from first container 10A to second container 10B through asymmetric membrane element 30.

[0088] Conversely, when the charged sub-membrane has a negative surface charge, an alternating electric field is applied between electrodes 20A and 20B, where electrode 20B, which is in contact with electrolyte solution 11B in second container 10B, is negatively charged. This induces cations in electrolyte solution 11B to flow from the negatively charged pore surfaces of charged sub-membrane element 30B to electrode 20B. This cation flow simultaneously induces solvent to flow from first container 10A to second container 10B through asymmetric element 30.

[0089] Examples of materials with surface charges suitable for use in charged sub-membrane elements according to the present invention include titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, nylon, polyamide, composite membranes such as thin film composite (TFC) membranes, anodized aluminum oxide (anodized aluminum oxide), hydrotalcite, polymer membranes with polyelectrolyte layers, any organic membranes such as porous PVC, PTFE, metal sulfide compounds such as WS2, MoS2, WSe2 or GaSe, semimetals (e.g. WTa2, TcS2), any liquid membrane, any biomimetic membrane (e.g. aquaporin), carbon materials such as graphene oxide, graphene or graphite, Ni–Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc) (dobdc is 1,4-dioxo-2,5-phthalate), cellulose or polyelectrolyte layer polymer membranes, for example, charged sub-membrane obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic polyacrylic acid onto a polycarbonate membrane. Ni2(dobdc) and Mg2(dobdc) are known metal organic frameworks having dobdc ligands and Ni or Mg metal sites, respectively. Advantageously, materials with surface charge suitable for use in the charged sub-membrane element according to the present invention include materials essentially formed from titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, and anodized aluminum oxide; preferably titanium oxide, boron nitride, SiO2, polycarbonate, and anodized aluminum oxide; and most preferably titanium oxide, polycarbonate, and anodized aluminum oxide.

[0090] Titanium oxide is understood to mean any type of titanium oxide, for example titanium (IV) oxide or titanium dioxide, and mixtures of two or more thereof. These titanium oxides may be in different solid polymorphic forms, in particular amorphous or crystalline forms. For titanium dioxide (TiO2), rutile or anatase crystalline forms are primarily used, preferably anatase.

[0091] As used herein, “substantially formed of titanium oxide, boron nitride, or the like” refers to a material formed of titanium oxide, boron nitride, or the like, which may include a minority element such as an impurity.

[0092] The physicochemical properties of materials such as titanium oxide, boron nitride, anodic aluminum oxide, SiO2 can often be tuned and enhanced by doping or functionalization, i.e. by inserting metallic chemical elements such as iron, silver, vanadium, gold, platinum, niobium, tungsten, or non-metallic elements such as nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, or different chemical compounds of the silane, amine or other organic families, preferably in small amounts, on their surface or in the core of the material network.

[0093] For example, the charged electron film material can be titanium oxide, which can be doped by inserting metallic chemical elements such as iron, silver, vanadium, gold, platinum, niobium, tungsten, or non-metallic elements such as nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, or different chemical compounds such as silanes or amines on its surface or in the core of the crystal network, preferably in an amount between 0.5 and 10 weight%, more preferably between 1 and 5 weight%.

[0094] Charged electronic membranes useful in the context of the present invention can be supported by a nanoporous or perforated mechanical substrate on which at least one material having a suitable surface charge is deposited. For example, the charged electronic membrane can consist of a flexible polymer film on which a layer of at least one material having a suitable surface charge, such as TiO2, is deposited.

[0095] Membranes comprising nanochannels whose inner surface is essentially formed or coated by at least one material having a suitable surface charge, such as ceramic membranes (e.g., titanium oxide, anodized aluminum oxide, SiO2), can be obtained directly by anodizing metal foils (e.g., Ti, Al or Si) [9]. Other techniques such as sol-gel techniques in the presence of block copolymers or graft copolymers also allow the synthesis of ceramic membranes, such as TiO2 membranes, with regular, oriented nanochannels

[10] . By this process, the morphological parameters, length, width and asymmetry of the through-nanochannels can also be adjusted. In addition, powder and sintering techniques can be used to obtain very thin ceramic membranes, such as titanium oxide membranes with regular, controlled through-nanochannels. The membranes can also be obtained by different deposition techniques, such as by chemical vapor deposition (CVD), atomic layer deposition (ALD) or high power impulse magnetron sputtering (HiPIMS), for example on nanoporous substrates with preformed morphology.

[0096] Alternatively, the surface of the negatively or positively charged material can be chemically modified to enhance the negative or positive charge naturally present on the material after contact with the electrolyte solution at a given pH. In other words, the surface of the charged sub-membrane 30B can be chemically modified to enhance the surface charge of the sub-membrane. The chemical modification can be achieved by chemical vapor deposition, atomic layer deposition, sol-gel coating or dip coating. Advantageously, the chemical modification can be performed on the surface of the pore wall of the charged sub-membrane. For example, the charged sub-membrane 30B can be obtained from a polycarbonate membrane having an average pore size of <500nm, preferably <300nm, more preferably <200nm; the inner pore wall of which has been chemically modified by dipping the polycarbonate membrane in an aqueous solution of polydopamine. At pH = 7, polycarbonate has a negative surface charge, and this charge is enhanced when the polycarbonate surface is coated with polydopamine.

[0097] In another alternative, when the surface of the membrane material carries ionizable functional groups, the surface charge of the membrane can be adjusted by using pH. For example, for membrane materials such as TiO2, SiO2, Al2O3, etc. that carry –OH groups on the surface, driving the pH of the electrolyte solution in contact with the membrane to an alkaline value (pH = 8-14) will deprotonate the –OH groups, thereby enhancing the negatively charged surface. Therefore, changes in pH can be used to adjust / control the zeta potential of the membrane surface. In fact, depending on the pH of the electrolyte solution in contact with the charged sub-membrane element 30B, the surface charge of the same membrane can be positive or negative. For example, a charged sub-membrane element 30B substantially formed of TiO2 can have a negative surface charge at pH ≥ 9 and a positive surface charge at pH ≤ 6.

[0098] Without wishing to be bound by any particular theory, it is proposed that nanochannels of materials with negative surface charge, taking into account their type, size and physicochemical properties, in particular their surface charge density is of the order of: Titanium dioxide: ~-100mC / m 2 (at pH ≥ 9) Boron nitride: ~-1C / m 2 (at pH ≥ 10) Silicon dioxide: ~-10mC / m 2 (at pH ≥ 6) Polycarbonate: ~-10mC / m 2 (at pH ≥ 5)

[0099] This promotes the passage of cations (ions with an opposite charge to the material's surface charge) through the electroosmotic nanofluid phenomenon generated by the application of an alternating electric field. The cation flow in the Debye layer at the interface of the negatively charged membrane surface is charged overall due to the imbalance of anions and cations under the action of the surface charge, thereby inducing the solvent to flow in the same direction as the cation flow.

[0100] Furthermore, the composite membrane is characterized by a greater current flow under one voltage sign (e.g., negative voltage) than under the opposite driving force (e.g., positive voltage). This asymmetry can be reversed by changing the orientation of the composite membrane relative to the ground electrode. The asymmetry in ion transport is then converted into an asymmetry in EO water transport, resulting in an asymmetric induced water flux. Thus, under the application of a suitable alternating electric field, a net solvent flow will occur through the asymmetric membrane element 30, from container 10A to container 10B. Because the asymmetric membrane element 30 includes a semipermeable sub-membrane element 30A that is selective for one or more specific solutes present in the electrolyte solution 11A, the cation flow generated in the pores of the charged sub-membrane 30B induces the electrolyte solution 11A to flow from container 10A to container 10B while preventing the solute from passing through (the solute is filtered out and remains in container 10A).

[0101] Conversely, it is proposed that nanochannels of materials with positive surface charge will facilitate the passage of anions (ie, ions with an opposite charge to the material's surface charge) through the electroosmotic nanofluidic phenomenon generated by the application of an alternating electric field.

[0102] In both cases (cation or anion flow), solvent flow is induced in the same direction as the generated cation / anion flow when a suitable alternating electric field is applied between the first and second electrodes 20A and 20B.

[0103] The membrane surface charge can be measured using any suitable method known in the art. For example, an electrokinetic analyzer can be used to determine the zeta potential of the charged sub-membrane.

[0104] The following equation can be implemented to estimate the zeta potential value of the membrane surface: in: ε is the dielectric constant of the solvent (e.g. water), ζ is the zeta potential, η is the viscosity of the solvent (e.g. water), A p is the total cross-sectional area of ​​all pores in the membrane exposed to the electrolyte solution, ΔP is the pressure drop over the length L of the hole, and I stream is the electric current.

[0105] When using a charged sub-membrane with low tortuosity porosity (e.g., nanoporous anodic aluminum oxide with mostly cylindrical pores), the pore length L can correspond to the thickness of the charged sub-membrane. For charged sub-membranes with significant tortuosity pores, calculations of permeability with respect to applied pressure allow the total pore length to be determined by applying the relevant tortuosity factor.

[0106] The zeta potential of the membrane surface can be measured at different pH values ​​(acidic, neutral and alkaline conditions) by changing the pH of the electrolyte solution using appropriate concentrations of a suitable acid (e.g., HCl) or base (e.g., KOH, NaOH, etc.). Preferably, the acid / base will be selected to be compatible with the ions present in the electrolyte solution used in the method / system according to the present invention. For example, when using a KCl electrolyte solution, KOH can be used as a base to adjust the pH.

[0107] For example, if one wishes to obtain a |zeta potential| of at least 5 mV at the membrane surface, one may choose a membrane material with a high surface charge, which allows the membrane to maintain a high zeta potential at the surface when in contact with an electrolyte solution.

[0108] The charged sub-membrane element 30B preferably has a larger average pore size than the semipermeable sub-membrane element 30A: the solute filtration function is performed by the semipermeable sub-membrane element 30A, while the function of the charged sub-membrane element 30B is to promote the reverse osmosis flow of the solvent when an appropriate alternating electric field is applied between the first and second electrodes 20A and 20B.

[0109] Advantageously, the charged sub-membrane element 30B with a positive or negative surface charge may have an average pore size of <500 nm, preferably <300 nm, more preferably <100 nm, and most preferably <50 nm. Preferably, in the context of the present invention, the average diameter of the nanochannels of the charged sub-membrane element 30B may be between 1 and 500 nm, preferably between 1 and 300 nm, more preferably between 10 and 100 nm, and most preferably between 10 and 50 nm.

[0110] As used herein, the term "average diameter" refers to the internal average diameter of a nanochannel. The nanochannel can have a nanotubular, conical asymmetric, neck-shaped, or perforated base morphology. If the nanochannel has a nanotubular morphology, i.e., a circular cross-section, the average diameter corresponds to the inner diameter of the circular cross-section. If the nanochannel has a conical asymmetric, neck-shaped, or perforated base morphology, or an elliptical or irregular cross-section, the average diameter corresponds to the average of the minimum and maximum inner diameters. The average diameter of the nanochannel can be measured using methods known to those skilled in the art. For example, the average diameter can be measured by scanning electron microscopy or transmission electron microscopy. Advantageously, the nanochannels contained in the charged sub-membrane element 30B can have a uniform diameter. If the nanochannels do not all have a uniform diameter on the same membrane, the average diameter will correspond to the average of the average diameters of all nanochannels.

[0111] Advantageously, in the context of the present invention, the nanochannel has a nanotubular, tapered asymmetric, necked or perforated base morphology, preferably the nanochannel has a tapered asymmetric morphology.

[0112] The morphological parameters of the charged sub-films that can be used in the context of the present invention can be evaluated using conventional techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal scanning laser microscopy (CSLM) and transmission electron microscopy (TEM). Alternatively, or in addition, X-ray computed microtomography (micro-CT), nuclear magnetic resonance (NMR), spin-echo small-angle neutron scattering (SESANS) and / or magnetic small-angle neutron scattering (MSANS) can be used (these techniques are generally faster and more complete because they can provide three-dimensional (volume) analysis). By these techniques, the morphological parameters of the charged sub-films according to the present invention, such as pore size, pore size distribution, surface roughness, molecular weight cut-off and thickness, can be evaluated.

[0113] Aperture represents the size of a channel with a variable cross section. For simple geometries, the distance between two relative pore walls is taken as the pore size (generally: when pore size>2nm, the diameter of the cylindrical pore is taken, when pore size<2nm, the width of the slit-shaped pore is taken). If the pore has an irregular shape, some averages are performed to report the average pore size. The method for measuring the pore size, average pore size and pore size distribution of porous materials is well known in the art (e.g., referring to ISO 15901 standard), including statistical analysis using models such as nonlinear optimization and Monte Carlo integration, for materials where the pores do not all have the same size and / or geometry. In view of the chemical and physical properties of the charged sub-membrane element 30B and the average pore size range (preferably, the average diameter of the nanochannels of the charged sub-membrane element 30B can be between 1 and 500 nm, preferably between 1 and 300 nm, more preferably between 10 and 100 nm, and most preferably between 10 and 50 nm), according to the ISO 15901 standard, the average pore size can be measured by nitrogen adsorption at -196°C (liquid nitrogen temperature).

[0114] Charged sub-membranes that can be used in the context of the present invention can have a pore size distribution that is non-uniform across the membrane thickness, or they can have a pore size distribution that is uniform across the membrane thickness. Typically, for charged sub-membranes with a non-uniform pore size distribution, there is a very thin, dense surface layer that serves as a functional layer on top of a porous sub-layer with a specific pore size. Charged sub-membranes with a non-uniform pore size distribution can consist, for example, of a 0.1–1 μm thick skin layer (selective barrier) and a highly porous 100–200 μm thick sub-structure. The pore size of the porous sub-layer can range from ≤1 nm to 500 nm, a range that defines the types of applications in which the charged sub-membranes can be used: microfiltration (50–500 nm), ultrafiltration (1–50 nm), and nanofiltration (≤1 nm). The pore size and its distribution can be determined by numerical analysis of the pore sizes observed in electron micrographs of membrane cross-sections. The pore size values ​​listed above represent the arithmetic mean of the pore size distribution observed across the membrane cross-section using scanning electron microscopy (SEM).

[0115] Advantageously, the average cross-section of the charged sub-membrane nanochannels and their specific, regular morphology throughout promote good diffusion of solutions through the membrane. Thus, the charged sub-membrane element 30B is clearly distinguished from the semipermeable sub-membrane element 30A by its pores, which may allow the circulation of water molecules and ions because each pore advantageously has a cross-section larger than the size of these molecules.

[0116] Furthermore, the closest distance between the semipermeable sub-membrane 30A and the charged sub-membrane 30B will reduce the overall resistance to electroosmotic diffusion, thus facilitating the performance of the method. Therefore, the semipermeable sub-membrane 30A preferably overlaps the charged sub-membrane 30B.

[0117] 1.3 Exemplary Characteristics of Composite Membrane Filtration Systems

[0118] In exemplary embodiments, methods and systems according to the present invention may utilize an asymmetric membrane comprising a semipermeable sub-membrane 30A, a charged sub-membrane 30B with a surface charge having a |zeta potential| ≥ 5 mV, and a particularly advantageous selection of electrodes 20A and 20B.

[0119] The semipermeable membrane 30A can be selected from a stack of nanoporous carbon films or layered materials. The stack of nanoporous carbon films or layered materials can be as described above. The pore size range of the nanoporous carbon film can be from 0.7nm to 1.5nm, preferably ≤1.4nm, more preferably ≤1.3nm, still more preferably ≤1.1nm, even more preferably ≤1.0nm. For example, the semipermeable membrane can be a multilayer MoS2 or WS2 membrane, a multilayer hexagonal NiB or BN membrane or a multilayer GO or rGO membrane, preferably a multilayer GO or rGO membrane, most preferably a multilayer MoS2 membrane. Advantageously, the semipermeable membrane 30A can be a size exclusion selective membrane composed of stacked graphene oxide flakes.

[0120] The charged electronic membrane 30B with a surface charge of |zeta potential| ≥ 5mV can be made of titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide; preferably titanium oxide, boron nitride, SiO2, polycarbonate and anodized aluminum oxide; most preferably titanium oxide, polycarbonate and anodized aluminum oxide.

[0121] The semipermeable membrane 30A is preferably overlapped with the charged membrane 30B. The semipermeable membrane can be placed directly on the charged membrane element 30B, or can be placed on another porous support layer (33) (for example, for ease of manufacturing and / or handling) and then placed on the charged membrane element 30B, as described above.

[0122] The first and second electrodes 20A and 20B can be any metal or carbon electrodes and can have a capacitive effect. Suitable metal electrodes include Zn, Fe, Pt, Ag or Au electrodes. Suitable carbon electrodes include carbon paste electrodes, glassy carbon electrodes, graphite or graphite carbon electrodes, or any carbon electrode used in salt batteries. Advantageously, the first and second electrodes 20A and 20B can be platinum electrodes. Preferably, the first and second electrodes 20A and 20B can be carbon electrodes (which has the advantage of allowing the filtration system according to the present invention to operate over a wide voltage range while showing limited parasitic electrochemical reaction catalysis (on the order of 0.1 V–1 kV, preferably between 0.1 V–100 V, and more preferably between 1 V–50 V)).

[0123] 2. Asymmetric membrane containing one material

[0124] An exemplary embodiment is Figure 1 .b is shown.

[0125] In another variation, the asymmetric membrane element 30 can be a single-material asymmetric membrane element, wherein the semipermeable sub-membrane element 30A and the charged sub-membrane element 30B are the same element, forming a single asymmetric membrane 30A. Advantageously, the single-material asymmetric membrane 30A can have a predetermined pore size and zeta potential to accommodate the target solute to be concentrated / depleted or eliminated / removed. Advantageously, the single-material asymmetric membrane 30A can have an average pore size suitable for removing the target solute from the electrolyte solution 11A, and a surface charge on the inner pore wall surface of the single-material asymmetric membrane having a |zeta potential| of ≥ 5 mV, preferably ≥ 20 mV, and most preferably ≥ 50 mV.

[0126] For example, the average pore size of the asymmetric membrane comprising one material will be small enough to prevent the target solute (and any other solutes with a particle size larger than the target solute) from passing through the asymmetric membrane 30A comprising one material, while allowing the solvent and other smaller solutes to pass through the asymmetric membrane 30A comprising one material. The average pore size of the asymmetric membrane 30A comprising one material will be adjusted according to the intended application type: microfiltration (50-500nm), ultrafiltration (1-50nm) or nanofiltration (≤1nm). Advantageously, the asymmetric membrane 30 comprising one material can have a porosity of <500nm (i.e., an average pore size measured according to ISO 15901 standard), preferably <300nm, more preferably <100nm, and most preferably <50nm. In a preferred variant, the filtration system is intended for ultrafiltration, and the asymmetric membrane 30A comprising one material can have an average pore size between 1-50nm.

[0127] The asymmetric membrane element comprising a single material may be a charged sub-membrane having a suitable (positive or negative) surface charge, as described above generally and in any variant (including preferred and advantageous variants), and having an average pore size suitable for eliminating / filtering the target solute from the electrolyte solution 11A, as described in the immediately preceding paragraph. The description of the charged sub-membrane will not be repeated here for the sake of brevity, but it should be understood that it is applicable, mutatis mutandis, to the asymmetric membrane element comprising a single material.

[0128] Advantageously, the asymmetric membrane 30A comprising a material may be a charged sub-membrane formed essentially of a material having a surface charge (positive or negative) with a |zeta potential| ≥ 5 mV, preferably ≥ 20 mV, most preferably ≥ 50 mV, such as TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc) (dobdc = 1,4-dioxo-2,5-benzene diformate), cellulose or polyelectrolyte layer polymer membrane, for example, a charged electron membrane obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic polyacrylic acid onto a polycarbonate membrane; preferably TiO2, BN, SiO2, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc), cellulose or polyelectrolyte layer polymer membrane; most preferably TiO2, BN, anodized aluminum oxide, SiO2 or polycarbonate.

[0129] Advantageously, the asymmetric membrane 30A comprising a material may be a size exclusion selective membrane coated on the inner pore walls with a material having a surface charge (positive or negative) with a |zeta potential| ≥ 5 mV, preferably ≥ 20 mV, most preferably ≥ 50 mV, such as TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc) (dobdc = 1,4-dioxo-2, 5-phthalate), cellulose or polyelectrolyte layer polymer membrane, for example, a charged electron membrane obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic polyacrylic acid onto a polycarbonate membrane; preferably TiO2, BN, SiO2, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2(dobdc), Mg2(dobdc), cellulose or polyelectrolyte layer polymer membrane; most preferably TiO2, BN, anodized aluminum oxide, SiO2 or polycarbonate.

[0130] 3. Asymmetric membranes containing two materials

[0131] An exemplary embodiment is Figure 1 .c is shown.

[0132] In another variation, the asymmetric membrane element 30 can be an asymmetric membrane element comprising two materials of the same nature, wherein one material differs from the other material in at least one physical and / or chemical parameter. Preferably, the asymmetric membrane comprising two materials can be a membrane comprising a first side and a second side made of the same material, wherein the pore size of each side is different.

[0133] For example, an asymmetric membrane comprising two materials may include a first side made of polycarbonate with a pore size of 200 nm and a second side made of polycarbonate with a pore size of 10 nm.

[0134] Containers 10A and 10B

[0135] In the present invention, any asymmetric membrane element 30 that separates the containers 10A and 10B can be used without particular limitation, as long as it does not allow solute permeation and primarily allows solvent permeation. Advantageously, the asymmetric membrane element 30 is preferably adapted to achieve a solute rejection of 98.0% or higher, preferably ≥98.5%, more preferably ≥99.0%, even more preferably ≥99.5%, and most preferably 100% or approximately 100%.

[0136] To carry out the method according to the invention, a separation device / system can be used which comprises two vessels separated by an asymmetric membrane element 30. In this case, the mixture to be separated is placed in the first vessel (vessel 10A), while the extracted solvent is recovered in the second vessel (vessel 10B).

[0137] In the present invention, the reverse electroosmotic filtration / purification system can be performed in a batch or continuous manner to maximize its effectiveness.

[0138] Preferably, the reverse electroosmotic filtration / purification system can be performed in a continuous manner.

[0139] Advantageously, the first and second containers can be configured to discharge bubbles generated during the parasitic electrochemical reaction by the Venturi effect, with the bubbles being discharged through the outlet tube 402 ( Figure 7 ).

[0140] Preferably, the first and / or second container may include an outlet pipe, or the outlet pipe may be connected to the first and / or second container. Preferably, the outlet pipe may be made of the same material as the container. Preferably, the outlet pipe may have a circular, square or oval shape.

[0141] Preferably, the first and / or second container may include a wall 401 and an outlet tube 402 divided into two parts; a tubular sub-container 402A and a hyperbolic sub-container 402B, wherein the tube diameter is w, the larger opening dimension of the hyperbolic sub-container is y, the narrower opening dimension of the hyperbolic sub-container is x, and the height dimension of the hyperbolic sub-container is z.

[0142] Preferably, the width w of the outlet pipe is 0.1 to 1000 times greater than the outlet width x of the container, more preferably 0.5 to 10 times greater, even more preferably 0.3 to 3 times greater.

[0143] Preferably, the outlet width x of the container is 0.1 to 1 times greater than the width y of the container (when measured at the bottom of the container height), more preferably 0.2 to 1 times greater, even more preferably 0.5 to 1 times greater.

[0144] Preferably, the height z of the container is 0.1 to 5 times greater than the width y of the container (when measured at the bottom of the container height), more preferably 0.2 to 5 times greater, even more preferably 0.5 to 2 times greater.

[0145] More advantageously, the first and second containers 40A and 40B have a geometry that allows compression of the first and second electrodes.

[0146] Container as described above is applicable to static mode.In order to apply tangential mode, the first and second containers 40A and 40B can independently include one or more fluid inlets, and this depends on the process applied.For example, suitable valve and / or pipeline (depending on the pressure range of the compartment) can be connected to the first and / or second container or both, to allow fluid to flow tangentially in the container and along the membrane surface.The first and / or second container also can be connected to one or more external tanks, and these tanks can respectively contain electrolyte.For example, valve can be flow valve, diaphragm valve, needle valve or even pressure relief valve.For example, pipeline can be metal or polymer tube.Those skilled in the art will know which pipeline and valve are selected according to the embodiment of process, and how to assemble them to form the closed tangential circulation of the electrolyte along the membrane surface.

[0147] The first and second containers 40A, 40B may also be combined with a pressure generator. The pressure generator may be a pump, a vacuum transfer unit, or a chemical concentration gradient between the two electrolytes. Thus, the method according to the present invention may be a pressure-assisted, AC voltage-induced reverse osmosis method, in addition to the field-induced flow applied in step iii) of the method according to the present invention.

[0148] For example, the reverse electroosmotic filtration / purification system according to the present invention may be configured in plural. In other words, the unit "container 10A-asymmetric membrane element 30-container 10B" may be configured in multiple stages.

[0149] In an exemplary variant, it can be provided that the reverse electroosmotic filtration / purification system comprises N containers (10) and N-1 asymmetric membrane elements 30, where N is an integer. For example, N can be between 3 and 100, more particularly between 3 and 50. In this multi-container device, the containers and asymmetric membrane elements can be defined as described above. Thus, the assembly can be formed by alternating containers (10) that alternately contain an electrolyte solution enriched in the target solute and an electrolyte solution with a lower concentration, separated from each other by an asymmetric membrane element 30. The expression "enriched solute" mentioned above means that the feed electrolyte solution contains a higher concentration of solute than the elution electrolyte solution.

[0150] solvent

[0151] Advantageously, the solvent of the first electrolyte solution 11A and the solvent of the second electrolyte solution 11B may be the same or different.

[0152] Advantageously, the solvent of the first electrolyte solution 11A and the solvent of the second electrolyte solution 11B are independently selected from polar solvents or non-polar solvents. Preferably, the solvent of the first electrolyte solution 11A and the solvent of the second electrolyte solution 11B are independently selected from water, one or more organic solvents or mixtures thereof.

[0153] As used herein, the term "polar solvent" does not deviate from its ordinary meaning and common knowledge / usage in the art. Generally, polar solvents include, without limitation, aprotic solvents having a dielectric constant ≥ 6 and a dipole moment ≥ 1.50 D, as well as protic solvents.

[0154] Preferably, the polar solvent may be a solvent capable of generating acidic ions. For example, the polar solvent may be water, an alcohol such as methanol or ethanol, a water-alcohol mixture, formic acid, acetic acid, hydrogen fluoride, ammonia, acetone or acetonitrile.

[0155] For example, the non-polar solvent may be hexane, pentane, cyclohexane, cyclopentane, toluene, 1,4-dioxane, or benzene.

[0156] Electrolyte solutions 11A and 11B and solute

[0157] The electrolyte solution that can be used in the context of the present invention may be any electrolyte solution containing at least one target solute / undesired solute in a solvent as defined above.

[0158] In a preferred embodiment, the electrolyte solution can be an aqueous solution containing electrolytes. The electrolytes can be of any chemical type, as long as they dissolve in the solution as charged ions. Preferably, these ions are derived from dissolved salts such as NaCl, KCl, CaCl2, and MgCl2. The electrolyte solution can be a synthetic solution; a natural solution such as fresh water from a lake or river, groundwater, brackish water, seawater, industrial process water, oil production water, or a biological solution / fluid.

[0159] Examples of solute-containing aqueous solutions used as electrolyte solutions according to the present invention include seawater, brackish water, cell metabolites, reaction products, biological fluids, etc., wherein cell metabolites are intended to include cultures of animal cells, plant cells or microorganisms, their primary metabolites, secondary metabolites, proteins secreted in vitro, and biotransformations.

[0160] Examples of reaction solutions include chemical reaction products and enzymatic reaction products.

[0161] Examples of major microbial metabolites include organic acids (e.g., acetic acid, propionic acid, butyric acid, lactic acid, succinic acid, etc.), alcohols (e.g., ethanol, butanol, etc.), hexane, amino acids (e.g., lysine, tryptophan, etc.), vitamins, polysaccharides, etc., but are not limited thereto.

[0162] Examples of microbial secondary metabolites include antibiotics (e.g., penicillin), enzyme inhibitors, and physiologically active substances (e.g., paclitaxel), while examples of microbial in vitro secreted proteins include enzymes such as amylase and cellulase, insulin, interferon, and monoclonal antibodies. Furthermore, microbial biotransformation refers to substances produced by microorganisms or enzymes, examples of which include, but are not limited to, steroids.

[0163] Examples of biological fluids include blood, serum, plasma, urine, saliva, tears, dialysate, intestinal contents, parenteral nutrition solutions, seminal plasma, and cerebrospinal fluid.

[0164] Preferably, the electrolyte solution may be an aqueous solution comprising a solute selected from alkali metal halides or alkaline earth metal halides, preferably selected from NaCl, KCl, CaCl2 and MgCl2, more preferably the solute is NaCl.

[0165] The solute may be selected from solid particles, organic or inorganic small molecules such as dye complexes (e.g., tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate), biomolecules such as hormones (e.g., testosterone), proteins, polysaccharides, polynucleotides, polypeptides, enzymes or antibodies, pollutants (e.g., from wastewater, industrial process water or landfill leachate), metabolic waste products or salts / ions. When the target solute to be concentrated is a solid, it is preferably a material that readily crystallizes depending on temperature and pH and does not have high viscosity even at high concentrations.

[0166] Advantageously, the solute is selected from the group consisting of ions such as calcium (Ca 2+ ), magnesium (Mg 2+ ), sodium (Na + ), potassium (K + ), carbonate (CO3 2- ), bicarbonate (HCO3 - ), sulfate (SO4 2- ), chloride (Cl - ), nitrate (NO3 - ) or phosphate ([PO4] 3- ), solid objects such as microplastics or any colloids or suspensions, macromolecules in solution or micropollutants such as hormones, pesticides, antibiotics, dyes, chemical compounds, neurostimulants, steroids, perfluoroalkyl and polyfluoroalkyl substances (PFAS) or their mixtures.

[0167] In the present invention, the solute can be a salt (or liquid), and the solvent can be water. For example, the electrolyte solution 11A can be seawater, the solute is NaCl, and the method is water desalination. Therefore, the present invention also relates to a water desalination system comprising a reverse electroosmotic filtration system according to the present invention, in any of the variations described herein.

[0168] The present invention also relates to a water purification system comprising a reverse electroosmotic filtration system according to the present invention, in any of the variations described herein. For example, water contaminants to be filtered may include pharmaceuticals, endocrine disruptors, hormones, pesticides and / or dyes.

[0169] More specifically, in one aspect, the present invention relates to a method for purifying a liquid comprising water and impurities, the method implementing electro-reverse osmosis technology.

[0170] Water purification generally means any operation that consists in treating water containing an initial content of impurities, by purifying the water so that, at the end of the operation, the final content of impurities is lower than the initial content.

[0171] Impurities are any elements, molecules, ions or other elements that are different from those that make up pure water (i.e. H2O, OH - and H + Such a purification method can be, for example, a method for desalination of seawater, a method for treating industrial process water, or a method for treating landfill leachate.

[0172] Thus, in one aspect, the present patent application promotes a methodology for recovering potable water from a wide variety of salinity sources, particularly surface waters containing various concentrations of sodium chloride, in applications ranging from less than 1% to 20% salinity, such as in applications involving the following salinities: brackish water of 0.5% to 3.5% salinity, seawater of 3.5% to 4.5% salinity, and brine of 5% to 20% salinity.

[0173] In the present invention, the electrolyte solution containing the solute may be a biological fluid, preferably a dialysate.Thus, the present invention also relates to an implantable artificial kidney comprising a reverse electroosmotic filtration system according to the present invention, in any of the variants described herein.

[0174] The basic principle of the present invention is that the asymmetric membrane element 30 (a single asymmetric membrane comprising a single material), or at least a portion thereof (a composite membrane comprising a semipermeable sub-membrane element 30A and a charged sub-membrane element 30B), has a sufficient surface charge (which can be positive or negative) to induce a zeta potential at the membrane / electrolyte solution interface. This potential is high enough to induce anion or cation flow, respectively, through the nanochannels of the charged sub-membrane when a suitable alternating electric field is applied between electrodes 20A and 20B. This phenomenon is governed by the same zeta potential principles that apply to colloidal particle suspensions.

[0175] In the case of colloidal suspensions, the fact that many organic and inorganic colloidal particles carry a negative charge in an aqueous environment causes them to repel each other and maintain the stable dispersion state that characterizes them. The electrochemical dispersion of colloidal particles has been studied for many years. Several models, such as the double layer theory and the DLVO theory, have been developed to explain the stability of colloids. The double layer model predicts that when suspended particles exist in a liquid phase, an inner dense layer on the surface of each particle (composed of ions in the solution that are attracted to the particle's charge) exhibits a charge of opposite polarity to the particle's natural charge under the physical and chemical conditions of the suspension. An outer layer of opposite polarity, also composed of ions in the solution, diffuses at a certain distance from the particle surface. The net potential between the two layers, commonly referred to in the art as the zeta potential, creates a repulsive force that counteracts the van der Waals attraction between the particles. If the outer layer spreads to a sufficiently wide radius, thereby increasing the influence of the zeta potential, the particles will be separated and maintained in a stable suspension. On the other hand, if the diffusion radius of the outer layer is reduced to the point where van der Waals forces dominate, the particles are attracted to form agglomerates that tend to separate from the liquid phase.

[0176] Extending this principle to the present invention: a dense layer at the inner pore wall surface of the charged sub-membrane (composed of ions in the electrolyte solution attracted by the surface charge present on the inner pore wall surface of the charged sub-membrane) exhibits a charge of opposite polarity to the natural charge of the charged sub-membrane itself under the physical and chemical conditions of the electrolyte solution. An outer layer of opposite polarity, also composed of ions in the solution, diffuses within a certain distance from the surface of the charged sub-membrane. The net potential between the two layers is called the zeta potential. The zeta potential is the potential difference between the Stern dense layer and the liquid. Therefore, it characterizes the charge distribution on the inner pore wall surface of the charged sub-membrane.

[0177] Therefore, the zeta potential depends on the ionic strength of the electrolyte solution, as well as the ion concentration in the solution surrounding the membrane surface.

[0178] In order to increase the zeta potential and improve the reverse osmosis flow generated on both sides of the asymmetric membrane element, the pH of the electrolyte solutions 11A and 11B can be adjusted according to the isoelectric point of the inner surface of the nanochannel of the charged sub-membrane 30B (composite membrane element or asymmetric membrane element comprising two materials) or 30 (asymmetric membrane element comprising one material).

[0179] The effect of pH on membrane surface charge can be studied by measuring the zeta potential of charged membrane samples at different pH values ​​of the electrolyte solution. The zeta potential of a charged membrane can tend to be negative as the pH value of the electrolyte solution increases. For example, one mechanism by which the zeta potential tends to be negative as the pH value increases includes the deprotonation of species on the pore wall surface of the membrane (e.g., the deprotonation of OH to O- on the surface of TiO2 or SiO2 membranes).

[0180] Advantageously, the pH of the first electrolyte solution 11A and the second electrolyte solution 11B may differ by more than 1 pH unit, more preferably by at most 14 pH units.

[0181] For example, when the solution to be purified is seawater (i.e., the solute is NaCl), the pH of the first electrolyte solution 11A and the second electrolyte solution 11B differ by 0 pH unit. For example, when the solution to be purified is brackish water contaminated by acidic or alkaline compounds (i.e., the solute is H + or OH- ions), the pH of the first electrolyte solution 11A and the second electrolyte solution 11B differ by 4 pH units. For example, when the solution to be purified is a battery electrolyte (i.e., the solute is lithium, sodium, or potassium), the pH of the first electrolyte solution 11A and the second electrolyte solution 11B differ by 0.1 to 14 pH units.

[0182] For example, when using a ceramic charged electron membrane, such as TiO2 or BN charged electron membrane, to obtain a negative charge on the inner surface of the nanochannel, the pH of the solution can be adjusted to a value between (pHiso+1) and 14, more preferably between (pHiso+2) and 12. To obtain a positive charge on the inner surface of the nanochannel, the pH of the solution can be adjusted to a value between 0 and (pHiso-1), more preferably between 1 and (pHiso-2). The increase in the negative zeta potential value of the charged electron membrane with increasing pH may be due to, for example, deprotonation of functional groups on the membrane surface.

[0183] As used herein, "pHiso" refers to the pH at the isoelectric point of the material constituting the inner surface of the nanochannel. pHiso is measured using methods known to the skilled artisan, particularly potentiometric acid-base titration.

[0184] Preferably, the temperature difference between the first electrolyte solution 11A and the second electrolyte solution is more than 1°C, more preferably more than 10°C, and more preferably more than 50°C.

[0185] When the electrolyte solution containing the solute is an aqueous solution, the pH of the aqueous solution can be 0 to 14, depending on the nature of the charged sub-membrane and the surface charge naturally present thereon, and the temperature is maintained at a temperature at which water is liquid, for example, 0 to 100° C., preferably 15 to 50° C., and more preferably 20 to 40° C. The temperature can be higher or lower than the above-mentioned temperature. For example, other solute / solvent mixtures can have a temperature that deviates from the above-mentioned temperature.

[0186] Electrodes 20A and 20B

[0187] As previously mentioned, each container 10A and 10B of the purification / filtration system according to the present invention includes an electrode (20A and 20B, respectively) arranged to be in contact with an electrolyte solution (11A and 11B, respectively).

[0188] Different types of electrodes can be used in the context of the present invention.

[0189] Advantageously, porous electrodes, grid electrodes or electrodes of any geometry through which the electrolyte can pass may be used. More advantageously, the electrodes may contain cavities or pores having a size ranging from 0.1 nm to 1 mm.

[0190] Advantageously, the first electrode 20A and the second electrode 20B are independently chosen from capacitive electrodes or electrodes capable of maintaining an alternating electric field across the membrane.

[0191] Advantageously, all types of materials capable of collecting cation or anion flows (e.g., Na + or Cl- ions), preferably silver and silver chloride (Ag / AgCl), carbon and platinum (C / Pt-), carbon (C-), graphite or [Fe(CN)6] 4- / [Fe(CN)6] 3- The first and second electrodes 20A and 20B may be any metal or carbon electrodes and may have a capacitive effect. Suitable metal electrodes include Zn, Fe, Pt and Au electrodes. Suitable carbon electrodes include carbon paste electrodes, glassy carbon electrodes, graphite or graphite carbon electrodes, or any carbon electrode used in salt batteries. Advantageously, the first and second electrodes 20A and 20B may be platinum electrodes. Advantageously, the first and second electrodes 20A and 20B may be carbon electrodes. The advantage of using carbon electrodes is that it allows the filtration system according to the present invention to operate over a wide voltage range while showing limited parasitic electrochemical reaction catalysis (on the order of 0.1 V–1 kV, preferably between 0.1 V–100 V, and more preferably between 1 V–50 V).

[0192] The electrodes 20A and 20B can be partially or completely immersed in the electrolyte solution (11A, 11B). Provision can also be made so that the electrodes 20A and / or 20B can be in the form of at least a portion of the wall of the container 10A and / or 10B. These electrodes 20A and 20B are connected to a power supply 40 that allows an alternating electric field to be generated between the two electrodes. These electrodes can be connected to the power supply 40 by a conventional cable.

[0193] Power Supply 40

[0194] In the method and system according to the present invention, the power source 40 may be any suitable power source known in the art.

[0195] Advantageously, the power supply is generated by a device providing only a DC voltage and coupled to a DC / AC converter, or by a device providing an alternating electrical signal.

[0196] For example, it can be a battery, a generator, a mains supply, a photovoltaic panel or any other source of electrical signals.

[0197] In the present invention, the purpose of power supply 40 is to generate an alternating electric field between electrodes 20A and 20B.

[0198] Advantageously, the power source 40 may comprise one or more batteries. Thus, the reverse electroosmotic filtration system according to the present invention may be a portable / mobile system. For example, the power source 40 may be configured to be charged by light, wherein the power source may particularly comprise a solar cell or a photodiode.

[0199] Advantageously, the power source 40 may be configured to be charged by utilizing the reverse electroosmotic effect of pumping electrolyte solution through the asymmetric membrane element 30. To this end, the power source 40 may include a turbine element operatively connected to the asymmetric membrane element 30.

[0200] Here we define the net electroosmotic flow Q EO .Q EO It can be calculated using the following formula (Formula III):

[0201] Where: D is the ion diffusion coefficient (m 2 / s), ω is the frequency (Hz), r is the average radius of the membrane pores (m), μ EO is the effective EO mobility, ΔV m is the local electric field at the membrane location (V), L is the membrane thickness (m), and r can be calculated from the average value of the total pore radius.

[0202] The net electroosmotic flow is directed from the first electrolyte solution 11A to the second electrolyte solution 11B.

[0203] Advantageously, the alternating electric field has an amplitude of 1 V to 1 kV and a frequency of 1 mHz to 1 GHz, preferably 0.001 Hz to 500 Hz, preferably between 0.01 Hz and 5 Hz.

[0204] Diaphragm 60

[0205] As used herein, separator 60 may independently be organic, inorganic, or an insulating composite material.

[0206] The diaphragm 60 should have a much larger pore size to allow the solvent flow of the electrolyte solution 11A to penetrate from the container 10A to the container 10B through the asymmetric membrane element 30. Therefore, the diaphragm 60 preferably can have a pore size that is at least 5 times, 10 times or more larger than the pore size of the semi-permeable membrane element 30A, and a thickness of 30 to 300 μm, more preferably 30 to 100 μm, preferably as thin as possible to reduce the distance between the electrodes, thereby reducing the resistance. The diaphragm 60 can be made of a neutral (no surface charge) non-reactive polymer material, such as a fluoropolymer such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), or a mixed cellulose ester or cellulose acetate, porous glass paper, nylon or polyolefin film. The diaphragm 60 can also be made of a porous ceramic material, such as alumina or silica-based porous ceramics, as non-limiting examples.

[0207] In some embodiments, the system may include a second membrane 60 positioned between the electrode 20A or 20B and the second side 30B of the asymmetric membrane element 30 .

[0208] Preferably, the system includes only one separator 60 to reduce the overall resistance of the battery by minimizing the distance between the first and second electrodes 20A and 20B.

[0209] bubble

[0210] As used herein, "bubbles" refer to small spheres that rise to the surface of a liquid and are filled with air or contain oxygen, hydrogen, chlorine, any other gaseous compound produced by electrochemical reactions depending on the solvent, or a mixture thereof.

[0211] Current collectors 70A and 70B

[0212] As used herein, the current collectors 70A and 70B may be independently selected from conductive materials such as silver chloride (Ag / AgCl), carbon and platinum (C / Pt-), platinum / iridium (Pt / Ir), platinum (Pt), carbon (C-), aluminum (Al), nickel (Ni), graphite, stainless steel (Fe / C), iron complex ([Fe(CN)6] 4- / [Fe(CN)6] 3- ).

[0213] Flow rate control (50)

[0214] The electrically induced reverse flow rate through the asymmetric membrane element according to the present invention can be controlled using different parameters:

[0215] (i) Surface charge of the charged sub-membrane: The flow rate of the membrane can be increased by using a membrane with a higher surface charge. The surface charge can be adjusted by the choice of materials, any chemical modification that can be used to change the surface charge of the membrane, and the pH of the electrolyte solution in contact with the surface of the charged sub-membrane. Advantageously, the |zeta potential| of the minimum surface charge is preferably ≥5mV, more preferably ≥20mV, and most preferably ≥50mV. The membrane surface charge can be adjusted based on the choice of materials constituting the charged sub-membrane and / or based on the ionic strength / concentration of the electrolyte solution in contact with the membrane, as previously described.

[0216] (ii) Pore size: With respect to semipermeable membranes (eg when composite membranes are used), the pore size will naturally depend on the size and / or chemical properties of the solutes to be filtered / separated.

[0217] With respect to the charged sub-membrane element (which performs the "pumping function" in the system), the larger its pore size, the greater the electroosmotic flow generated (see Formula III). There are no other specific restrictions on pore size, except in the case where the charged sub-membrane element also functions as a size-exclusion semipermeable sub-membrane (e.g., the case of an asymmetric membrane element comprising one material described herein, in which case the average pore size of the charged sub-membrane should be adapted to the size of the solute to be separated / filtered out). This is true for variants using composite membranes as well as for variants using asymmetric membranes comprising two materials or asymmetric membranes comprising one material (i.e., when using a dual semipermeable / charged membrane element, as in Figure 1 Advantageously, the average pore size of the charged sub-membrane element (which functions to electrically induce solvent flow in the system) may be >10 nm, preferably >100 nm, more preferably >1 μm, and most preferably >500 μm.

[0218] (iii) Pore geometry: In general, a semipermeable sub-membrane may not have a well-defined pore geometry (e.g., it may be "spaghetti-shaped"). With respect to the charged sub-membrane elements, there are no particular restrictions on the pore geometry: the system will be applicable to any pore geometry (provided that the charged sub-membrane material carries a suitable surface charge, as further detailed herein), ranging from materials with symmetrical pore shapes (e.g., anodized aluminum, which has cylindrical pores) to materials with highly tortuous porosity (e.g., nylon or polycarbonate, which have conical pores). For example, porosities with nanotubular morphology, i.e., cylindrical pores with a circular cross-section, conical asymmetric pore shapes, honeycomb pore geometries, hourglass-shaped porosities, etc. may be used. The electroosmotic flow through the charged sub-membrane can be optimized by adjusting the pore geometry of the membrane. This can be achieved empirically by varying the pore geometry of a given charged sub-membrane using methods well known in the art.

[0219] In general, flow rate can be optimized if the membrane pore geometry is preferably symmetrical and has little or no tortuosity. Thus, a nanotubular morphology, i.e., a circular cross-section, will have the effect of increasing flow rate through the membrane, as opposed to, for example, a conical asymmetric pore shape.

[0220] (iv) Electric field strength: For a given charged sub-membrane 30B and membrane surface area exposed to the electrolyte solution in the system according to the present invention, the flow rate increases with increasing current (and therefore electric field) applied between the electrodes. The choice of applied current will depend in part on the type of filtration application (microfiltration (50–500 nm), ultrafiltration (1–50 nm) or nanofiltration (≤1 nm)). The strength and alternating electric field are selected to maximize the flow rate. It will also depend on the number of pores that can induce electroosmotic flow, and therefore on the surface area of ​​the charged sub-membrane in contact with the electrolyte solution and the surface pore density of the charged sub-membrane. Typically, for given electrolyte solution conditions such as pH concentration, a curve of flow rate versus strength (or current) is plotted to determine the optimal range of electric field strength. For ultrafiltration purposes, the resulting current is preferably less than 100 A, more preferably less than 1 A, and more preferably less than 100 mA. The electric field strength will preferably be adjusted according to the electrodes and / or membrane used.

[0221] (v) Ionic Strength / Concentration of the Electrolyte Solution: The flow rate is inversely proportional to the salt concentration in the electrolyte solution. The choice of salt concentration in the electrolyte solution will depend on the flow rate to be achieved. For ultrafiltration purposes, the salt concentration in the electrolyte solution preferably ranges from 0.1 mM to 100 mM, preferably from 0.1 mM to 50 mM, more preferably from 0.1 mM to 10 mM, and most preferably from 1 mM to 10 mM.

[0222] In summary, we have developed a filtration method based on the application of an alternating electric field using a composite asymmetric membrane with a nanoscale average pore size (<500 nm) and a significant surface charge. When the membrane separates two containers containing water (or other solvents) and a mobile electrolyte (such as salt), the application of an alternating electric field between the two containers of the cell generates electroosmotic flow (the movement of water / solvent from one reservoir to the other in the opposite direction to normal osmotic flow), which can be expressed for each single pore by the following formula (Formula III):

[0223] Where: V is the net liquid volume along the electroosmotic flow direction (L), t is the experimental time (s), ω is the frequency (Hz), r is the radius of the pore (m), μ EO is the effective EO mobility, ΔV m is the local electric field at the membrane location (V), L is the membrane thickness (m);

[0224] Furthermore, the separator 60 allows the membrane to be protected from any mechanical deformation when the cell is closed and prevents any short circuits if the membrane is damaged during the process.

[0225] The present invention offers a complementary advantage, namely that the nature of the porous electrodes and the shape of the container allow for the expulsion of bubbles, thereby preventing their accumulation. Indeed, any bubbles formed due to parasitic electrochemical reactions, if not expelled, could potentially reduce the active membrane surface. In the present invention, the shape of the container optimizes the expulsion of any bubbles, limiting their accumulation along the membrane surface.

[0226] As mentioned earlier, the scarcity of drinking water resources is a major international concern. On the one hand, certain industrial wastes, particularly pharmaceutical and chemical waste, pose significant challenges for treatment plants. On the other hand, some arid countries utilize reverse osmosis desalination processes on a large scale to produce drinking water. However, the energy costs of these processes significantly increase the price of water and the cost of the equipment.

[0227] Alternating electric field filtration makes it possible to eliminate the high pressures required in traditional water treatment processes. For example, low-pressure desalination requires pressures exceeding the osmotic pressure (>30 bar); seawater desalination requires pressures >60 bar; and brine treatment requires pressures >120 bar. These processes are expensive and complex to implement. Applying an alternating electric field reduces water treatment costs, even for larger molecules that are sometimes difficult to eliminate (hormones, drugs, etc.). Combining the use of two-dimensional nanomaterials (such as graphene oxide or boron nitride) with this filtration process also makes it possible to work with membranes with tunable porosity, as the two-dimensional nanochannels can be easily chemically and geometrically modified, increasing the possibility of adapting them to purification applications and improving permeability / selectivity thresholds.

[0228] The main advantage of applying an alternating voltage is that it avoids any effects due to charge polarization or electrode saturation. However, this technique cannot be applied to symmetric membranes because the average water flux over one cycle is zero. On the other hand, for nanocomposite membranes that exhibit highly asymmetric transport, the average water flux over one cycle is non-zero, resulting in a net transport of mass from one side of the asymmetric membrane to the other.

[0229] The present invention puts into practice the use of an alternating electric field to induce separation and filtration, as opposed to standard processes based on mechanical drive of pressure differences (usually of the reverse osmosis type). The present invention thus provides a filtration method that is not based on concentration differences (as in forward osmosis) or pressure differences (reverse osmosis), but on the application of an alternating electric field. This offers a huge economic advantage: the equipment is cheaper, applying electricity is cheaper than applying pressure, and the method avoids mechanical stress (usually a pressure of about 50 bar is used on the membrane, which is not the case here). As a result, the use of exotic membrane materials that are mechanically unable to withstand the high mechanical reverse osmosis pressures can be considered. This also has a significant ecological advantage, as it can provide an upstream solution for the filtration of complex molecules to be eliminated in purification plants. For example, the alternating electric field filtration system according to the present invention can be installed in plants in the pharmaceutical or textile industries for wastewater pretreatment.

[0230] Thus, the present invention provides an extremely valuable alternative to filtration / purification methods and water treatment processes that overcome the shortcomings of existing methods.

[0231] Examples

[0232] The method and system according to the present invention and its implementation can be further understood by illustrating some examples of how the method is performed. However, it should be understood that these examples should not be interpreted as limiting the present invention.

[0233] abbreviation GO: graphene oxide PC: Polycarbonate MoS2: molybdenum disulfide

[0234] Materials and Methods

[0235] Commercial graphene oxide aqueous dispersion with a concentration of 0.4 wt% was purchased from Gographene SA.

[0236] Polycarbonate track-etched membranes were supplied by Sterlitech Corporation.

[0237] Potassium chloride (>99%), tris(2,2′-bipyridyl)ruthenium(II) dichloride hexahydrate (99.95%), and testosterone (>99.9%) were purchased from Sigma-Aldrich.

[0238] All experiments were performed at room temperature (25 ± 3 °C) and neutral pH.

[0239] The experiments used a potentiostat (Bio-logic, SP200) for electrical excitation and measurement. The potentiostat was connected to the electrodes via thin platinum wires (0.5 mm diameter). The flow rate response of the system was measured using a flow sensor (Sensirion, SLF3S-0600F), with a sampling frequency limited to 1 ms.

[0240] For the DC voltage experiments, a voltage drop was applied to the electrodes for 30 minutes. Current and flow rate were recorded at a high sampling frequency (>10 Hz) to capture the dynamic response of the system over a short period of time. Before each application of voltage, the electrodes were regenerated to avoid any polarization effects in the next experiment. This regeneration phase can be accomplished as commonly described in the literature by short-circuiting, reversing polarity, or forcing equilibrium to be restored in a distilled water solution (by applying 0 V until the current reaches a significantly low value (<1 mA)). All experiments presented herein were performed by applying 0 V to the system between each test.

[0241] For AC voltage experiments, the sampling frequencies for current and flow rate were chosen so that a sufficient number of data points (>10) were captured for each cycle for analysis. As with the DC voltage experiments, the system was allowed to return to equilibrium between each measurement.

[0242] Example 1 – Preparation and characterization of composite membranes

[0243] Example 1 in Figure 1 (a) is set in the system.

[0244] The composite membrane was prepared by depositing a two-dimensional nanolaminate of GO 30A onto a commercial macroporous polymer substrate 30B (Whatmann, PC membrane, pore size: 0.2 μm, pore density: 2·10 13 Hole / m 2 ) prepared above.

[0245] GO dispersion in water was purchased from Graphenea SA (concentration 0.1%). The latter was diluted and further sonicated for 10 min and centrifuged twice at 3000 rpm to remove aggregates and obtain a monolayer dispersion.

[0246] The entire VIRO composite membrane has been synthesized by deposition of a two-dimensional filter using vacuum filtration: a solution of exfoliated monolayer nanosheets dispersed in water was added dropwise on top of a 25 mm diameter polycarbonate (PC) substrate disc, presenting a thickness of 24 ± 1 μm and a porosity of 4.7% given by 100 nm track-etched pores (Nuclepore track-etched membrane, 25 mm, 0.1 μm). The disc was placed on a Buchner funnel: one end was sealed and the other end was connected to a vacuum pump.

[0247] The surface charge of the PC membrane was measured using the conductivity equation [1] and determined to be approximately 0.2 mC / m 2 .

[0248] The pore size of the two-dimensional layered graphene oxide (GO) membrane was measured using an Xpert Pro instrument (Philips PanaAnalytical, Cu Kα; The XRD pattern revealed a broad distribution of interlayer distances (ranging from 0.7 to 1.4 nm).

[0249] The average pore size of the second side 30B of the asymmetric membrane element 30 is 250 times smaller than the average pore size of the first side 30A.

[0250] Material characterization

[0251] The surface morphology of the composite film was observed by optical microscopy in transmission mode and field emission scanning electron microscopy (FE-SEM) in a Thermo-Fischer™ QuattroS instrument. The cross section of the two-dimensional nanolaminated layer was observed after tilting the sample holder by 90°. The X-ray diffraction pattern of the film was obtained by using a powder XRD diffractometer. The average spacing between the GO layers of the GO / PC film was determined by applying Bragg's law to the 001 peak of the recorded diffraction pattern.

[0252] Example 2 – Preparation and Characterization of Alternative Composite Membranes

[0253] Composite membranes were prepared according to Example 1, but using a two-dimensional nanolaminate made of MoS2.

[0254] The MoS2 suspension has been obtained by chemical exfoliation of MoS2 bulk crystals as previously reported and further sonication and centrifugation steps as described in [7].

[0255] Example 3 – Cell and Electrode

[0256] The VIRO cell consists of two containers 10A and 10B (feed water and pure water), separated by a composite membrane 30. Capacitive electrodes 20A and 20B are located in each container 10A and 10B to allow the application of an alternating electric field to generate an EO flow. In order to maximize this flow, the electrodes 20A and 20B are compressed on the membrane 30. The distance between the electrodes is therefore small, resulting in a higher alternating electric field strength. The use of capacitive electrodes avoids the generation of large Faradaic currents and therefore limits the presence of electrochemical reactions that could interfere with the transport mechanism through the membrane. A 100 μm thick highly porous polymer felt is used as a diaphragm 60 between the electrode 20B and the second side of the membrane 30B to avoid direct electrical contact between them.

[0257] The cell was fabricated using an additive manufacturing process (SLA) using a 3D printer (Formlabs, Form 3, 50 mL Formlab resin). Once the cell was assembled and closed, each container was connected to its reservoir via fluid connections and a valve system.

[0258] The capacitive electrode used was an activated carbon electrode (Gmbh, Kynol).

[0259] Example 4 – Filtration of micropollutants

[0260] To investigate the molecular sieving properties of nanocomposite membranes, their performance in nanopurification and desalination was evaluated using VIRO (Vitro Inertial Oxygen Reduction) experiments. The retention of several typical micropollutants, for which purification options are scarce and expensive, was measured in EO processes: an organic dye (rhodamine B), acetaminophen (paracetamol), caffeine, and testosterone. Filtration of the nanopollutants was performed according to the following steps:

[0261] i) contacting a first electrolyte solution of 30 mL volume V1 comprising nanopollutants in water at a concentration of 10 mM with the first porous electrode according to Example 3;

[0262] ii) contacting a second electrolyte solution comprising pure water in a volume V2 of 10 mL with the second porous electrode according to Example 3;

[0263] iii) An alternating electric field of 10 V and 10 Hz was applied between the first and second electrodes 20A and 20B, thereby achieving solvent transfer and solute filtration through the membrane element according to Example 1, and a change in volume V2 (nT) of 1·10 -5 m 3 , where n = 9000 and T = 0.1 s;

[0264] iv) Gas bubbles generated during the parasitic electrochemical reaction are automatically discharged by gravity due to the optimized cell geometry (Venturi effect).

[0265] Analysis of the filtered water for micropollutants was performed by absorbance analysis (Thermo scientific, Nanodrop) using light transmission analysis from a droplet of the sample (1 μL).

[0266] The concentration of NaCl in the two reservoirs was measured using conductivity or inductively coupled plasma optical emission spectrometry (ICP-OES). ICP-OES measurements were obtained using an ICAP 7400 ICP-OES analyzer spectrometer (THERMO SCIENTIFIC).

[0267] Results and Discussion

[0268] The tests demonstrated the filtration of 10 mL of water containing 10 mM feed concentration of micropollutant model molecules. Nanofiltration experiments achieved a rejection of over 99.9% for all micropollutants and for both GO+PC and GO+MoS2 asymmetric membranes ( Figure 8 For GO+PC and GO+MoS2 asymmetric membranes, the maximum values ​​of 10 L·h were obtained, respectively. -1 ·m -2 and 80L·h -1 ·m -2 The electroosmotic flow rate QEO was 150 min and 15 min respectively.

[0269] The asymmetry in EO transport demonstrates that the main advantage of applying an alternating voltage is that it avoids any effects due to charge polarization or electrode saturation. However, this technique cannot be applied to symmetric membranes, as the average water flux over one cycle is zero. On the other hand, for nanocomposite membranes that exhibit highly asymmetric transport, the average water flux over one cycle is non-zero, resulting in a net transport of mass from one side of the asymmetric membrane to the other.

[0270] Example 5 – Comparison of flux obtained by pure electroosmotic filtration and pressure-assisted electroosmotic filtration

[0271] Example 4 was repeated without applying additional mechanical pressure and with several additional mechanical pressures, with the following modifications:

[0272] i) contacting a first electrolyte solution having a volume V1 of 10 mL and comprising an aqueous sodium chloride solution having a concentration of 10 mM with the first porous electrode according to Example 3;

[0273] ii) contacting a second electrolyte solution having a volume V2 of 10 mL and comprising an aqueous sodium chloride solution having a concentration of 10 mM with the second porous electrode according to Example 3;

[0274] The first container has been adapted by adding two valves and pipes connected to the side and top openings of the container. Both pipes are connected to a pressurized tank containing the first electrolyte. The combination of the first container, valves, two pipes, and the pressure tank is interconnected and pressure-tight so that the first electrolyte can circulate through it under controlled pressure. The pressurized tank is connected to a pressure generator that provides a pressure in the range of 0 to 1 bar.

[0275] iii) applying an alternating electric field at 2.5 Hz with a voltage difference between 1 V and 5 V between the first and second electrodes 20A and 20B, causing the solvent to be transferred through the membrane element according to Example 1,

[0276] iv) Gas bubbles generated during the parasitic electrochemical reaction are automatically discharged by gravity due to the optimized cell geometry (Venturi effect).

[0277] Experiments performed without and with external mechanical pressure (pressure-assisted electroosmotic filtration, step v)) showed that at a voltage amplitude of 5 V, the electroosmotic flux (Q EO ) was 0.105 mL / min. When the pressure was increased to 750 mbar under the same voltage and frequency conditions, a higher total flux (Q tot =Q EO +Q pressure ) was 1.15 mL / min, thus demonstrating that electroosmosis and pressure-driven reverse osmosis flux can be combined. One advantage of this combination may be the use of reverse electroosmosis filtration to reduce the operating mechanical pressure of the reverse osmosis filtration process.

[0278] References

[0279] 1.Becker N, Lavee D, Katz D. Desalination and Alternative Water-ShortageMitigationOptions in Israel: A Comparative Cost Analysis. JWARP. 2010; 02(12): 1042-56.

[0280] 2.Spiritos E,Lipchin C.Desalination in Israel.In:Becker N,éditeur.Water Policy inIsrael[Internet].Dordrecht:Springer Netherlands;2013[cité7 mars 2022].p.101-23.(GlobalIssues in Water Policy;vol.4).Disponiblesur: http: / / link.springer.com / 10.1007 / 978-94-007-5911-4_7

[0281] 3.Wang L,Dykstra JE,Lin S.Energy Efficiency ofCapacitiveDeionization.Environ SciTechnol.2 avr 2019;53(7):3366-78.

[0282] 4.Oren Y.Capacitive deionization(CDI)for desalination and watertreatment—past, present and future(a review).Desalination. 2008;228(1-3):10-29.

[0283] 5.Al-Amshawee S,Yunus MYBM,Azoddein AAM,Hassell DG,Dakhil IH,HasanHA.Electrodialysis desalination for water and wastewater:A review.ChemicalEngineering Journal.janv 2020;380:122231.

[0284] 6.Koros WJ,Zhang C.Materials for next-generation molecularlyselective syntheticmembranes.Nature Mater.mars 2017;16(3):289-97.

[0285] 7.Ries L,Petit E,Michel T,Diogo CC,Gervais C,Salameh C,et al.Enhancedsievingfrom exfoliated MoS2 membranes via covalent functionalization.NatMater.oct 2019;18(10):1112-7.

[0286] 8.Joshi RK,Alwarappan S,Yoshimura M,Sahajwalla V,Nishina Y.Grapheneoxide:thenew membrane material.Applied Materials Today.nov 2015;1(1):1-12.

[0287] 9.Progress on free-standing and flow-through TiO2 nanotubesmembranes,Guohua Lin,Kaiying Wang,Nils Hoivik,Henrik Jakobsen,Solar EnergyMaterials&Solar Cells,98,2012,pp24-38;TiO2 nanotubes synthesis andapplications,Poulomi Roy,Steffen Berger,Patrick Schmuki,Angewandte ChemistryInt.Ed,50,2011,pp 2904-2939.

[0288] 10.Jung Tae Park,Won Seok Chi,Sang Jin Kim,Daeyeon Lee&Jong Hak Kim, Scientific Reports 4:5505,Nature,2014.

[0289] 11.Song J.et al.,Preparation and Characterization of Graphene Oxide;Journal of Nanomaterials,276143,2014.

Claims

1. A method for purifying an electrolyte solution, comprising the following steps: i) contacting a first electrolyte solution (11A) of a first volume V1 with a first porous electrode (20A), the first electrolyte solution (11A) comprising a solute and a solvent; ii) contacting a second electrolyte solution (11B) of a second volume V2 with a second porous electrode (20B), wherein the second electrolyte solution (11B) includes a solvent; iii) applying an alternating electric field between the first and second electrodes (20A) and (20B) to achieve solvent transfer and solute filtration through a membrane element (30), wherein the change in volume V2 is defined by the following formula (Formula I): V2(nT)=μ EOeff ΔV eff πr 2 n TL -1 Where T is the period of the applied signal (s), n is the number of completed cycles, and μ EOeff is the effective electroosmotic mobility (m 2 ·V -1 ·s -1 ), ΔV eff is the local potential difference at the membrane (V), r is the average radius of the pores of the membrane (m); and L is the membrane thickness (m); iv) exhausting bubbles generated during parasitic electrochemical reactions; in, The first electrode (20A) and the second electrode (20B) are separated by an asymmetric membrane element (30), and the asymmetric membrane element (30) includes a first side (30A) and a second side (30B); The average pore size of the second side (30B) of the asymmetric membrane element (30) is 1.1 to 10,000 times smaller than the average pore size of the first side (30A); A diaphragm (60) is positioned between the electrode (20A or 20B) and the second side (30A) of the asymmetric membrane element (30); The asymmetry between the first side and the second side of the membrane element (30) is a geometric, physicochemical, environmental property or a combination thereof; and The first electrode (20A) and the second electrode (20B) are operatively coupled to a power source (40) via two current collectors (70A, 70B).

2. The method according to the preceding claim, wherein The method is performed in a static mode or a tangential mode.

3. The method according to any one of the preceding claims, further comprising the step of v) pressure-induced reverse osmosis.

4. A method according to any preceding claim, wherein: The temperature difference between the first electrolyte solution (11A) and the second electrolyte solution (11B) exceeds 1°C.

5. A method according to any preceding claim, wherein: The asymmetric membrane element (30) comprises a composite material, each element of which has different properties; or comprises a component composed of two materials of the same nature, wherein at least one inherent property is different; or comprises a single material, wherein at least one inherent property is different on both sides.

6. A method according to any preceding claim, wherein: The first side (30A) comprises a semi-permeable sub-membrane and the second side (30B) comprises a charged sub-membrane.

7. The method according to the preceding claim, wherein The second side (30B) of the asymmetric membrane element (30) is in contact with the second electrolyte solution (11B) including a solvent.

8. The method according to claim 4, wherein: The second side (30B) of the asymmetric membrane element (30) is in contact with the first electrolyte solution (11A) including a solvent.

9. The method according to any one of claims 4 to 6, wherein: The semipermeable membrane (30A) includes a steric repulsion separation membrane, an electrostatic repulsion separation membrane, or a membrane capable of separating / filtering specific solid molecules or ions from a given electrolyte solution.

10. A method according to any preceding claim, wherein: The first electrode (20A) and the second electrode (20B) are independently selected from capacitive electrodes or electrodes capable of maintaining an alternating electric field across the membrane.

11. A method according to any preceding claim, wherein: The separator (60) is organic, inorganic or insulating composite material.

12. A method according to any preceding claim, wherein: The current collectors (70A, 70B) are independently selected from conductive materials such as silver chloride (Ag / AgCl), carbon and platinum (C / Pt-), platinum (Pt), carbon (C-), graphite and iron complex ([Fe(CN)6] 4- / [Fe(CN)6] 3- ).

13. A method according to any preceding claim, wherein: The power supply (50) is generated by a device that provides only a DC voltage and is coupled to a DC / AC converter, or by a device that provides an alternating electrical signal.

14. A method according to any preceding claim, wherein: The solvent of the first electrolyte solution (11A) and the solvent of the second electrolyte solution (11B) may be different or the same.

15. A method according to any preceding claim, wherein: The solvent of the first electrolyte solution (11A) and the solvent of the second electrolyte solution (11B) are independently selected from the following solvents: water, one or more organic solvents, one or more polar solvents, one or more non-polar solvents and mixtures thereof.

16. A system for purifying an electrolyte solution, comprising: a first container (40A) comprising a first volume V1 for a first electrolyte solution (11A), said first electrolyte solution (11A) comprising a solute and a solvent; - a second container (40B) comprising a second volume V2 for a second electrolyte solution (11B), said second electrolyte solution (11B) comprising a solvent; - a first electrode (20A) configured to be in contact with the first electrolyte solution (11A); - a second electrode (20B) configured to be in contact with the second electrolyte solution (11B); - an asymmetric membrane element (30) comprising a first side (30A) and a second side (30B); - a diaphragm (60) positioned between the electrode (20A or 20B) and the second side (30B) of the asymmetric membrane element (30); as well as - two current collectors (70A, 70B) operatively coupling the first electrode and the second electrode (20A, 20B) to a power source (40) configured to apply an alternating electric field between the first electrode and the second electrode; in, - the first container (40A) and the second container (40B) are configured to discharge bubbles generated during the parasitic electrochemical reaction through a Venturi effect; - the first and second electrodes (20A, 20B) are porous electrodes, grid electrodes or electrodes of any geometry through which the electrolyte can pass; - the asymmetric membrane element (30) has an asymmetry of geometric, physicochemical, environmental properties or a combination thereof between the first side and the second side of the membrane element (30); The average pore size of the second side (30B) of the asymmetric membrane element (30) is 1.1 to 10,000 times smaller than the average pore size of the first side (30A).

17. System according to the preceding claim, wherein The first electrode and the second electrode are pressed onto the membrane element (30).

18. The system according to claim 16 or 17, wherein: The first container and the second container (40A, 40B) independently have one or more fluid inlets.

19. The system according to any one of claims 15, 16 or 17, wherein: The first container and the second container (40A, 40B) are combined with a pressure generator to process pressure-assisted AC voltage-induced reverse osmosis.

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