Reverse electroosmotic filtration utilizing nanofluidic transport through asymmetric membranes

Abstract

The present invention relates to a process for purifying an electrolyte solution, the process comprising application of an alternating electric field between a first electrode and a second electrode, resulting in solvent transport and solute filtration through an asymmetric membrane, and to a system for purifying an electrolyte solution using such a process.

Description

[Technical Field]

[0001] The present invention relates to a continuous process for purifying an electrolyte solution, the process comprising application of an alternating electric field between a first electrode and a second electrode, resulting in solvent transport and solute filtration through an asymmetric membrane, and to a system for purifying an electrolyte solution using such a process.

[0002] Reference signs [X] in square brackets refer to the list of references at the end of the Examples. [Background technology]

[0003] The global water demand for the world's population is a key issue in the ecological transition. Indeed, climate change, population growth, and the rise of developing countries are increasing these needs, and therefore access to water is a critical factor for the future of our modern societies.

[0004] The oceans represent a huge source of water that could potentially be harnessed to meet this demand, provided it could be desalinated cleanly and sustainably at low cost. On the other hand, non-salt water sources such as rivers suffer from the presence of trace contaminants even after conventional treatment. Water purification also finds important applications for hydrogen production by electrolysis, where pure water is required.

[0005] Many technologies have been developed for the filtration and desalination of contaminants. Reverse osmosis (RO) is one of the most deployed techniques for water treatment.[1][2] Other processes, such as capacitive deionization or electrodialysis, have made significant progress in the past decades. However, these various processes suffer from several problems that limit their large-scale deployment.[3][4][5]

[0006] The efficiency of the membranes used in these various techniques plays a crucial role in the performance of the process. To optimize water transport while maintaining critical sieving properties, new materials have been developed over the past few decades. [6] The nature of the material and its architecture are key parameters that allow for the optimization of its performance. The emergence of 2D materials such as graphene oxide or MoS2 has made it possible to improve water transport properties for filtration and desalination. [7][8] Additionally, understanding the fundamental phenomena occurring at the nanoscale offers the possibility of targeting macroscopic materials with unique transport properties, which could potentially offer new perspectives for desalination, filtration, and energy harvesting. However, the fabrication of optimized nanostructured materials with long cycle life remains complex and costly and therefore represents a significant challenge.

[0007] Some technologies, such as the invention presented in EP 3862069, have shown that water purification and desalination using electroosmotic forces can be achieved with reasonable voltages comparable to standard pressure-driven technologies. However, macroscopic membranes and capacitive electrodes operating under electrostatic forces are known to suffer from polarization effects, which lead to a dramatic decrease in performance over a relatively short period of time. Indeed, charge accumulation on the two sides of the membrane and at the electrode / electrolyte interface led to reverse potentials that counteracted the overall electro-optical force. If this parasitic effect could be suppressed by conventional techniques, such as systematically shorting electrodes to reset the electrostatic environment during operation, it would limit the overall performance of the process, preventing the use of the technology for out-of-lab applications. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Application Publication No. 3862069 Summary of the Invention [Means for solving the problem]

[0009] In seeking solutions to the various technical problems associated with the prior art, the applicant surprisingly discovered a new technique for water treatment based on electroosmotic flow (EO flow), in which continuous transport of water through a selective membrane is maintained by applying an external AC voltage to the membrane. [Brief explanation of the drawings]

[0010] [Figure 1] (a) Schematic of an exemplary system according to the present invention with a composite asymmetric membrane element 30, (b) Schematic of an exemplary system according to the present invention with an asymmetric membrane element 30 comprising a single material, and (c) Schematic of an exemplary system according to the present invention with an asymmetric membrane element 30 comprising two materials. [Figure 2] FIG. 1 shows a schematic diagram of an exemplary system according to the present invention, further including a rubber flat seal 80A and one rubber thoric seal 80B. [Figure 3] (a) A photographic representation of a composite asymmetric membrane. (b) SEM cross-sectional image of a 2D lamellar membrane. [Figure 4] FIG. 1 shows X-ray diffractograms of GO and MoS multilayers showing 0.83 nm and 0.62 nm interlayers, respectively. [Figure 5a] FIG. 1 is a graph containing the fluxes measured for EO-driven and pressure-driven experiments of an asymmetric membrane with a charged polycarbonate (PC) submembrane and a semipermeable MoS 2 submembrane. [Figure 5b] Schematic diagram of the structure of two stacked monolayers of MoS2 (one central layer of molybdenum atoms is contained between two layers of sulfur atoms). [Figure 5c] FIG. 1 shows a schematic diagram of the structure of one monolayer of graphene oxide. [Figure 5d]Graph containing the flux measured for EO-driven and pressure-driven experiments of an asymmetric membrane with a charged polycarbonate (PC) sub-membrane and a semipermeable GO sub-membrane.

[11] [Figure 6a] This figure shows the IV response of the system for the electrode, PC membrane, and asymmetric membrane (PC+GO & PC+MoS2). It shows the ion current under voltage drop for various configurations: the membrane-free cell and the cell with a bare support PC membrane (symmetric) show a completely symmetric response, with no difference between the ion current under positive and negative voltages. On the other hand, the composite membrane is characterized by ion transport with a larger current under negative voltages relative to positive voltages (the asymmetry can be reversed by changing the orientation of the composite membrane relative to the ground electrode). The asymmetry in ion transport then translates into an asymmetry in EO water transport, which leads to the generation of asymmetric induced water flux. [Figure 6b] Figure 1 shows the dynamic response of EO flow and current of an asymmetric membrane under an AC electric field (amplitude: 10 V, frequency: 2.5 Hz). It shows the measured dynamic response of both current and flow rate of a composite membrane under AC voltage. The reported EO flux is highly asymmetric, which leads to net water transport from one side of the membrane to the other. [Figure 6c] FIG. 1 shows the evolution of the volume of net permeation through an asymmetric membrane for several frequencies (amplitude: 10 V). [Figure 7] FIG. 4 is a schematic diagram of an example of a vessel 40A or 40B, the vessel 40A or 40B including a wall 401 and an outlet pipe 402, the outlet pipe 402 being subdivided into two parts, a pipe sub-vessel 402A and a hyperbolic sub-vessel 402B, the pipe diameter being w, the larger opening of the hyperbolic sub-vessel having dimension y, the narrower opening of the hyperbolic sub-vessel having dimension x, and the height of the hyperbolic sub-vessel having dimension z. [Figure 8]FIG. 1 shows the measured removal rates of trace pollutants and their molecular structures (acetaminophen, caffeine, and rhodamine) for PC+GO and PC+MoS2 membranes. [Figure 9] Figure 1 shows the evolution of the net permeate volume through an asymmetric membrane obtained by pressure-assisted reverse electroosmosis filtration for different pressure inputs in Example 5. The experiments were carried out on a PC+GO membrane at a frequency of 2.5 Hz and for different voltage and pressure inputs. DETAILED DESCRIPTION OF THE INVENTION

[0011] definition 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 this invention pertains. Generally, the nomenclature and laboratory methods used herein (which will be described below) are those well known and commonly employed in the art.

[0012] To facilitate understanding of the present invention, several terms and phrases are defined below.

[0013] As used herein except in the claims, the terms "a," "an," "the," and / or "said" mean one or more. As used herein in the claims, when used in connection with the words "comprise," "comprises," and / or "comprising," the words "a," "an," "the," and / or "said" can mean one or more. As used herein and in the claims, the terms "having," "has," "is," "have," "including," "includes," and / or "include" have the same meaning as "comprising," "comprises," and "comprise." As used herein and in the claims, "another" can mean at least a second or more. As used herein and in the claims, "about" refers to any inherent measurement error or rounding of numbers associated with a value (e.g., a calculated value such as a measurement, ratio, etc.), and thus the term "about" may be used in conjunction with any value and / or range.

[0014] Phrases such as "combinations thereof" and "mixtures thereof" following a list, the use of "and / or" as part of a list, a list in a table, the use of "such as" as part of a list, the phrase "such as," and / or a parenthetical list with "for example" or "i.e." refer to any combination (e.g., any subset) of a set of listed components, and combinations and / or mixtures of related species and / or embodiments described herein are also contemplated, even though not directly placed within such a list. Such related and / or similar genera, subgenera, species, and / or embodiments described herein are contemplated both in the form of individual components that may be claimed, and in the form of mixtures and / or combinations that may be claimed as "at least one selected from," "mixtures thereof," and / or "combinations thereof."

[0015] As used herein, the term "and / or" means any one of the items, any combination of the items, or all of the items with which the term is associated.

[0016] As will be understood by those skilled in the art, all numbers, including those expressing properties such as amounts of ingredients, cavity / pore size and zeta potential, as well as experimental conditions, are approximate and are understood in all instances to be optionally modified by the term "about." These values ​​may vary depending on the desired properties sought to be obtained by the skilled artisan utilizing the teachings of the description herein. It is also understood that such values ​​inherently contain variations necessarily resulting from the standard deviation found in their respective testing measurements.

[0017] As used herein, the term "about" can refer to a ±5% variation of the specified value. For example, "about 50" percent can have a variation of 45 to 55 percent in some embodiments. With respect to integer ranges, the term "about" can include integers one or two greater and / or less than the recited integer. Unless otherwise indicated in the specification, the term "about" is intended to include values ​​(e.g., concentration values) that are close to the recited range and are equivalent in terms of the functionality of the individual component, composition, or embodiment.

[0018] As will be understood by those skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges described herein encompass any and all possible subranges and combinations of subranges, as well as the individual values ​​(especially integer values) comprising the range. A described range includes each specific value, integer, decimal, or identity within the range. Any recited range can be readily recognized as fully descriptive and allowing the same range to be broken down into at least two equal parts, one-third, one-quarter, one-fifth, or one-tenth. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third, upper third, etc.

[0019] Detailed Description of Certain Preferred Embodiments of the Invention The systems and processes according to the present invention overcome one or more of the above-discussed problems that may be commonly associated with conventional membrane technologies and processes. Specifically, the systems of the present invention use a reverse electro-osmosis filtration system. This and other unique features of the systems are discussed below and illustrated in the accompanying drawings.

[0020] It should be understood that various components, parts, and features of different embodiments may be combined together and / or substituted for one another, 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 mixing and matching of features, elements, and / or functions between various embodiments is expressly contemplated herein, and that those skilled in the art will recognize from the present invention that features, elements, and / or functions of one embodiment may be incorporated into another embodiment as appropriate, unless otherwise stated.

[0021] A first object of the present invention is to provide a method for manufacturing a computer-readable recording medium comprising the steps of: i) contacting a first volume V1 of a first electrolyte solution 11A containing a solute and a solvent with a first porous electrode 20A; ii) contacting a second volume V2 of a second electrolyte solution 11B including a solvent with the second porous electrode 20B; iii) applying an AC electric field between the first electrode 20A and the second electrode 20B, resulting in solvent transport and solute filtration through the membrane element 30, the change in volume V2 (V2(nT)) being defined by the following formula (Formula I): V2(nT) = μ EOeff ΔV eff πr 2 nTL -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 ) and 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) evacuating the gas bubbles generated during the parasitic electrochemical reaction; 1. A process for purifying an electrolyte solution, comprising: The first electrode 20A and the second electrode 20B are separated by an asymmetric membrane element 30 including a first side 30A and a second side 30B; the second side 30B of the asymmetric membrane element 30 has an average pore size that is 1.1 to 10,000 times smaller than that of the first side 30A; a separator 60 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 geometric, physicochemical, environmental, or a combination thereof; The first electrode 20A and the second electrode 20B are operably connected to a power supply 40 via two current collectors 70A and 70B.

[0022] Advantageously, the process according to the invention can be carried out in static or tangential mode. By static mode, it is meant that no specific flow is generated tangential to the membrane. By tangential mode, it is meant that, in addition to steps i) to iv) of the process according to the invention, a liquid flow is generated tangential to the membrane surface. The tangential mode limits membrane fouling. Tangential AC voltage reverse osmosis can be carried out in a co-flow or cross-flow configuration. The flow rate can be adjusted by those skilled in the art 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 delivery pump, or a vacuum. The tangential flow can be generated within 0.01 ms -1 from 1000m.s -1 Preferably 0.1 ms -1 from 100 m.s -1 Between 1 m.s. and 2 m.s. -1 from 100 m.s -1 The speed may be between

[0023] Advantageously, the process according to the invention may further comprise a step v) of pressure-induced reverse osmosis. To implement step v), the first and second vessels are pressure-resistant using appropriate valves corresponding to the range of pressures to be applied. They are preferably also connected to pressurized tanks of the feed and permeate solutions. Depending on the technique used to apply the mechanical pressure difference, the permeate compartment, the feed compartment, or both must be adapted. For example, the pressure difference can be applied by generating a pressure difference or a chemical gradient between the two vessels. For example, the pressure difference can be generated using a pumping system or a vacuum system. For example, if a pump is used to generate the pressure difference, the feed compartment must be pressure-resistant and connected to the pump. As another example, if a vacuum is used to generate the pressure difference, the permeate compartment must be pressure-resistant and connected to a vacuum delivery unit. The chemical gradient can be applied by a concentration gradient between the two electrolytes 11A and 11B. The pressure difference to be applied between the two vessels depends on the initial concentration difference of the two electrolytes, the osmotic pressure to be overcome, the type of membrane element, and the flux of the purified liquid to be obtained. For example, for seawater purification, the pressure gradient to be applied can range between 0.1 bar and 150 bar, preferably between 30 bar and 130 bar. The variation of the volume V2 (V2(nT)) is due to electro-osmosis in step iii). Step v) also has an influence on the variation of the volume V2. The volume variation induced by step v) and pressure-induced reverse osmosis results in V2(nT). 2p =K m dPt.

[0024] Steps iii) and v) can be implemented sequentially or simultaneously. When steps iii) and v) are implemented simultaneously, the total volume of change is calculated by the electroosmotic pressure V2(nT) as described in the following equation: EO and pressure-induced reverse osmosis V2p is the sum of the volume increases due to V2 = V2(nT) EO + V 2p = μ EOeff ΔV eff πr 2 nTL -1 + K m dPt where V2(nT) EO is the volumetric contribution due to electroosmotic filtration (m 3 ) and V 2p is the volumetric contribution due to pressure-induced reverse osmosis (m 3 ) and K m is the membrane permeability (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).

[0025] The second object of the present invention is to a first vessel 40A containing a first volume V1 of a first electrolyte solution 11A containing a solute and a solvent; a second vessel 40B containing a second volume V2 of a second electrolyte solution 11B including a solvent; a first electrode 20A in contact with a first electrolyte solution 11A; a second electrode 20B in contact with the second electrolyte solution 11B; an asymmetric membrane element 30 including a first side 30A and a second side 30B; a separator 60 positioned between the electrode 20A or 20B and the second side 30B of the asymmetric membrane element 30; - two current collectors 70A and 70B operatively connecting the first and second electrodes 20A and 20B to the power supply 40; 1. A system for purifying an electrolyte solution, comprising: the first vessel 40A and the second vessel 40B are configured to expel gas bubbles generated during the parasitic electrochemical reaction by a Venturi effect; the first and second electrodes 20A and 20B are porous electrodes, grid electrodes or any geometric shape through which the electrolyte can diffuse; the asymmetric membrane element 30 has an asymmetry of geometric, physicochemical, environmental, or a combination thereof between the first and second sides of the membrane element 30; The second side 30B of the asymmetric membrane element 30 has an average pore size that is 1.1 to 10,000 times smaller than that of the first side 30A, in this system.

[0026] Advantageously, the first and second electrodes 20A and 20B may be operably coupled to a source of electrical power 40 via two current collectors 70A and 70B such that an alternating electric field may be applied between the first electrode 20A and the second electrode 20B (e.g., the electrical energy source 40 enables an alternating electric field to be applied between the first electrode 20A and the second electrode 20B).

[0027] As used herein, the term "solute" refers to a liquid or solid material that dissolves in the solvent used in electrolyte solution 11A and / or 11B. Solid solutes may be selected from solid particles, organic or inorganic small molecules (e.g., dye complexes (e.g., tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate), etc.), biomolecules (e.g., hormones (e.g., testosterone), proteins, polysaccharides, polynucleotides, polypeptides, enzymes, or antibodies), perfluoroalkyl and polyfluoroalkyl substances (e.g., wastewater, industrial production water, or landfill leachate), metabolic waste, or salts / ions (e.g., NaCl, LiCl, Na2SO4, etc.). Liquid solutes may be organic acids (e.g., acetic acid, propionic acid, butyric acid, lactic acid, succinic acid, and boric acid), alcohols (e.g., ethanol and butanol), or hexane.

[0028] As used herein, the term "VIRO" refers to "Voltage Induced Reverse Osmosis."

[0029] As used herein, the term "membrane element" refers to a membrane that allows specific molecules or ions to pass through it by diffusion, osmosis, or artificially generated flux, as the term traditionally does in the field of filtration membranes. For example, it may 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.

[0030] As used herein, the term "electrolyte solution" refers to a conductive solution containing mobile ions (e.g., ions from dissolved salts such as NaCl, KCl, CaCl, or MgCl) that induce electroosmosis.

[0031] As used herein, "zeta potential" when referring to a membrane surface charge does not depart from the conventional meaning of the term in electrochemistry and refers to the potential difference between the membrane surface and a stationary layer of fluid attached to the membrane surface. Zeta potential typically depends on the nature of the membrane surface and the characteristics (e.g., pH, ion concentration, ionic force, etc.) of the electrolyte solution in contact with the membrane surface. Zeta potential can be calculated using the Smoluchowski equation (see Equation 1 below).

[0032] 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). As will be readily understood from the present invention, the present invention can be practiced using charged sub-membrane elements with negative or positive surface charges, and the zeta potential can be negative or positive, respectively, when the membrane is placed in contact with an electrolyte solution.

[0033] The asymmetric membrane element 30 may comprise a composite material having different properties for each element of the composite material, an assembly of two materials of the same nature having at least one inherent property that differs, or a single material having at least one inherent property that differs from one side to the other.

[0034] Advantageously, the second side 30B of the asymmetric membrane element 30 may have an average pore size that is 1.1 to 10,000 times smaller than that of the first side 30A, preferably 100 to 5,000 times smaller, and more preferably 500 to 2,000 times smaller.

[0035] The permeate, with rejected solutes removed therefrom, exits asymmetric membrane element 30 as a permeate stream and can be collected in vessel 40B.

[0036] In one variation, the second side (30B) of the asymmetric membrane element (30) is in contact with a second electrolyte solution 11B that includes a solvent.

[0037] In a second variant, the second side (30B) of the asymmetric membrane element (30) is in contact with a first electrolyte solution 11A containing a solvent.

[0038] Advantageously, the orientation of the membrane is such that the variation of the volume V2 (V2(nT)) satisfies the following formula (Formula I): V2(nT) = μ EOeff ΔV eff πr 2 nTL -1 may be defined by The variation of volume V1 (V1(nT)) is given by the following formula (Formula II): V1(nT) = -μ EOeff ΔV eff πr 2 nTL -1 It can be determined as can be defined by: 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 (m2 .V -1 .s -1 ) and ΔV eff is the local potential difference across the membrane (V), r is the average radius of the membrane pores (m), and L is the membrane thickness (m); In both formulas, μ EOeff and ΔV eff is strictly positive and frequency dependent. Moreover, r can be calculated based on the average value of the global pore radius.

[0039] Those skilled in the art will know how to adapt the orientation of the asymmetric membrane according to the type of membrane asymmetry, depending on the result of the calculation of V2(nT) or V1(nT) above.

[0040] 1. Composite asymmetric membrane An exemplary embodiment is illustrated in FIG. 1(a).

[0041] In one variation, the first side 30A of the asymmetric membrane element 30 includes a semipermeable sub-membrane and the second side 30B of the asymmetric membrane element 30 includes a charged sub-membrane.

[0042] 1.1. Semipermeable submembrane The semipermeable sub-membrane usable in the context of the present invention can be any semipermeable sub-membrane known in the art.

[0043] Advantageously, the semipermeable sub-membrane element 30A can be a size-exclusion membrane, an ion-exchange membrane, or any other membrane that enables the separation / filtration of specific molecules or ions from a given electrolyte solution (e.g., a semipermeable sub-membrane based on chemical affinity separation). For example, it can be a semipermeable sub-membrane that separates pure water molecules from salts and other impurities: a membrane that is permeable to water and relatively impermeable to various dissolved impurities, including dissolved salts, organic matter, bacteria, and pyrogens, as well as other small molecules. As such, it can be a semipermeable sub-membrane conventionally used in water purification technologies that use semipermeable sub-membranes to remove ions, molecules, and larger particles from contaminated water. It can also be a semipermeable sub-membrane for use in water purification or desalination systems (e.g., in reverse osmosis systems), such as thin-film composite membranes (TFC or TFM). Membranes used in reverse osmosis are typically made from polyamides, which are selected primarily for their permeability to water and relative impermeability to various dissolved impurities, including salt ions and other small molecules that cannot be filtered. In yet another example, semipermeable sub-membrane element 30A can be an anion exchange membrane (AEM) or a cation exchange membrane (CEM). For example, semipermeable sub-membrane element 30A can be a Nafion® semipermeable sub-membrane.

[0044] The average pore size of the semipermeable sub-membrane is adapted to filter the target solute from the electrolyte solution 11A. As such, the membrane average pore size is 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 sub-membrane 30A, while allowing the solvent and other smaller solutes to pass through the semipermeable sub-membrane 30A. The average pore size of the semipermeable sub-membrane is adapted depending on the intended application type: microfiltration (50-500 nm), ultrafiltration (1-50 nm), or nanofiltration (≦1 nm). Advantageously, the semipermeable sub-membrane element 30A may have an average pore size of <500 nm, preferably <300 nm, more preferably <100 nm, and most preferably <50 nm. In a preferred variant, the filtration system is for ultrafiltration, and the semipermeable sub-membrane element 30A may have an average pore size between 1 and 50 nm. In another preferred variation, the filtration system is for nanofiltration, and the semipermeable sub-membrane element 30A can have an average pore size of <1 nm. Such a nanofiltration system can be useful, for example, for desalination.

[0045] Advantageously, the semipermeable sub-membrane comprises a steric exclusion membrane, an electrostatic exclusion membrane, or a membrane capable of separating / filtering specific solid molecules or ions from a given electrolyte solution. More advantageously, the semipermeable sub-membrane is made of TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, polyamide, composite membranes (such as thin film composites (TFCs)), PTFE, polymeric membranes with polyelectrolyte layers, metal chalcogenides (such as WS2, MoS2, WSe2, or GaSe), semimetals (such as WTa2, TcS2), metal-organic framework membranes (MOFs), MXene, biomimetic membranes (such as aquaporins), any liquid membrane, carbon materials (such as graphene oxide, graphene, or graphite), superconductors (such as NbS2, TaSe2), topological insulators, and thermoelectric materials (such as Bi2Se3, Bi2Te), or the semipermeable sub-membrane is an organic or inorganic filtration membrane, preferably a nanofiltration, ultrafiltration, or reverse osmosis membrane. All these materials can exhibit similar properties of selective permeability and can be used as molecular sieves in applications involving membrane separation (eg, nanofiltration, desalination, etc.).

[0046] Carbon nanotube membranes (carbon materials) consist of two perforated graphene sheets connected by a short carbon nanotube of defined diameter. However, their practical applications are limited due to the complexity of their fabrication. Nanoporous graphene membranes consist of a single sheet of graphene with nanopores of defined sizes. However, obtaining large graphene sheets with predefined pore sizes and high pore densities remains challenging. Graphene oxide (GO) membranes consist of stacked GO nanosheets separated by interconnected nanochannels that form pores that allow selective permeation through the membrane. They can be produced relatively easily and inexpensively by depositing GO solutions onto various supports by spraying, dip coating, spin coating, vacuum filtration, etc., and are currently the most commonly used. Furthermore, GO sheets can be converted into graphene-like reduced GO (rGO) sheets, which have electrical, thermal, mechanical, and surface properties similar to those of pristine graphene.

[0047] Thus, in the context of the present invention, the semipermeable sub-membrane can 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.

[0048] Advantageously, the semipermeable sub-membrane 30A can be a size-exclusion selective membrane composed of stacked graphene oxide flakes. Advantageously, the stacked graphene oxide flakes can form a network of 2D nanochannels with an interlayer spacing between the GO flakes in the range of 0.7 to 1.4 nm. The interlayer spacing between the stacked graphene oxide flakes can be measured by any suitable process known in the art. For example, it can be measured using XRD.

[0049] Advantageously, the pore size of the nanoporous carbon membrane can be in the range of 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. "Pore size," when referring to a carbonaceous semipermeable submembrane, refers to the pore diameter in the case of carbon nanotube and nanoporous graphene membranes, and the width of the interlayer gap in the case of multilayer GO or rGO membranes. Typically, the nanoporous carbon membrane can be 0.05 μm to 1 μm thick, preferably 100 nm to 500 nm thick, in the case of carbon nanotube membranes. In the case of multilayer GO or rGO films, the carbon film can include at least two, preferably at least three, and up to 300 layers of GO or rGO sheets and can be 0.05 μm to 20 μm thick, e.g., 0.05 μm to 15 μm thick, 0.05 μm to 10 μm thick, 0.05 μm to 5 μm thick, or 0.05 μm to 1 μm thick. For example, the carbon film can be about 0.1 μm thick.

[0050] In another variation, the semipermeable sub-membrane 30A can be a laminated membrane of lamellar material. Any lamellar material can be used, such as MoS2, hexagonal NiB, clay, or graphite.

[0051] For example, the semipermeable sub-membrane 30A may be a multilayer MoS2 film, a multilayer hexagonal NiB film, or a multilayer GO or rGO film, preferably a multilayer GO or rGO film, most preferably a multilayer GO film.

[0052] In another exemplary variation, the semipermeable sub-membrane 30A is an anion exchange membrane (e.g., OH - , Cl - transport) or cation exchange membranes (e.g., H + , Na + , K. + The membrane may be an ion exchange membrane, such as a membrane transport membrane.

[0053] The semipermeable sub-membrane can be placed directly on top of the charged sub-membrane element 30B. This can be achieved, for example, by vacuum filtration, preferably in a wet condition (from a dispersion in water or an aqueous solvent). For example, a dispersion of a carbonaceous material (e.g., carbon nanotubes, graphene, GO, or rGO) or a lamellar material (e.g., MoS2, hexagonal NiB, clay, MXene, MOF graphite-based) in water can be added dropwise under vacuum to the top of the charged sub-membrane 30B. For example, the charged sub-membrane 30B can be placed on a Buchner funnel connected to a vacuum pump, and the dispersion of the carbonaceous or lamellar material in water can be added slowly (e.g., dropwise) to the top of the charged sub-membrane 30B to form a laminated membrane (semipermeable sub-membrane element) of the carbonaceous or lamellar material.

[0054] Advantageously, the semipermeable sub-membrane may be adapted to provide a solute rejection of preferably 98.0% or greater, preferably ≧98.5%, more preferably ≧99.0%, still more preferably ≧99.5%, and most preferably 100%, or about 100% solute rejection.

[0055] A person skilled in the art will know how to adapt the semipermeable sub-membrane average pore size to the context of its use, depending on the size of the solutes it has to filter.

[0056] 1.2. Charged Submembrane Charged sub-membranes that can be used in the context of the present invention can be any charged membrane known in the art.

[0057] 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 with a zeta potential of 5 mV or greater, preferably 20 mV or greater, and even more preferably 50 mV or greater.

[0058] In one variation, the charged submembrane may be a submembrane in which at least a portion of the inner surface of the membrane's nanochannels is essentially formed from at least one material having an appropriate surface charge. As used herein, unless otherwise indicated, the term "essentially formed" of a material means "made from" the material. The term also encompasses the possibility that the material may optionally be physically or chemically modified (e.g., on the surface and / or on the pore wall surface) to modulate its physicochemical properties to suit its intended use. Chemical modifications can include doping (e.g., adding metal elements onto the surface or into the core of the material network); coating (e.g., with a thin layer of a material with an appropriate surface charge); covalent functionalization; physisorption or chemisorption of compounds / species, for example, by 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 a pH change.

[0059] In one preferred embodiment, at least a portion of the interior surface of the nanochannel is formed essentially of or coated with at least one material having a suitable surface charge.

[0060] Advantageously, the nanochannels may be formed entirely from or coated with at least one material, preferably having an appropriate surface charge.

[0061] As used herein, "at least a portion of the inner surface of the nanochannel" refers to the fact that the inner surface of the nanochannel may include one or more sections essentially formed from a material having an appropriate surface charge, or that the entire inner surface is essentially formed from at least one material having an appropriate surface charge. The sections may be regular or irregular, discontinuous or non-discontinuous, and / or in the form of a single layer or multiple layers. Preferably, the total inner surface of the nanochannel is essentially formed from at least one material having an appropriate surface charge.

[0062] Charged sub-membranes usable in the context of the present invention can have a positive or negative surface charge.

[0063] When the charged sub-membrane carries a positive surface charge, applying an AC electric field between electrode 20A and electrode 20B (where electrode 20B, in contact with electrolyte solution 11B in second vessel 10B, is positively charged) will induce a flow of anions in electrolyte solution 11B from the positively charged pore surface of charged sub-membrane element 30B toward electrode 20B. This anion flow simultaneously induces a flow of solvent through asymmetric membrane element 30 from first vessel 10A toward second vessel 10B.

[0064] Conversely, when the charged sub-membrane carries a negative surface charge, applying an AC electric field between electrodes 20A and 20B (where electrode 20B, in contact with electrolyte solution 11B in second vessel 10B, is negatively charged) will induce a flow of cations in electrolyte solution 11B from the negatively charged pore surface of charged sub-membrane element 30B toward electrode 20B. This cation flow simultaneously induces a flow of solvent through asymmetric element 30 from first vessel 10A toward second vessel 10B.

[0065] Examples of materials with a surface charge suitable for the charged sub-membrane element according to the present invention include titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, nylon, polyamide, composite membranes (e.g., thin film composites (TFCs)), anodized aluminum oxide (anodic alumina), hydrotalcite, polymer membranes with a polyelectrolyte layer, any organic separator (e.g., porous PVC, PTFE), metal chalcogenides (e.g., WS2, MoS2, WSe2, or GaSe), semimetals (e.g., WTa2, TcS2), any liquid membrane, any biomimetic membrane (e.g., aquaporins), carbon materials (e.g., graphene oxide, graphene, or graphite), Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc (dobdc = Examples of suitable charged sub-membrane elements include 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, or polyelectrolyte layer polymer membranes (e.g., charged sub-membranes obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) onto a polycarbonate membrane). Ni2dobdc and Mg2dobdc are known metal-organic frameworks having dobdc ligands and Ni or Mg metal sites, respectively. Advantageously, materials having a surface charge suitable for the charged sub-membrane element of the present invention include 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, materials consisting essentially of titanium oxide, polycarbonate, and anodized aluminum oxide.

[0066] By titanium oxide is meant any type of titanium oxide, such as titanium(IV) oxide or titanium dioxide, and mixtures of two or more thereof. These titanium oxides can be in different solid polymorphic forms, in particular amorphous or crystalline. With regard to titanium dioxide (TiO), rutile or anatase crystalline morphological types are primarily used, with the anatase form being preferred.

[0067] As used herein, "formed essentially of titanium oxide, boron nitride, etc." refers to a material formed of titanium oxide, boron nitride, etc., which may contain small amounts of elements such as impurities.

[0068] The physicochemical properties of materials such as titanium oxide, boron nitride, anodized aluminum oxide, SiO2, etc. can generally be modulated and amplified by doping or functionalization, i.e., by inserting metallic chemical elements (e.g., iron, silver, vanadium, gold, platinum, niobium, tungsten, etc.), or non-metallic elements (e.g., nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, etc.), or different chemical compounds of the silane, amine, or other organic families, preferably in small amounts, onto the surface or into the core of the material network.

[0069] For example, the charged sub-membrane material may be titanium oxide, which may be doped on the surface or in the core of its crystalline network by inserting metallic chemical elements (e.g., iron, silver, vanadium, gold, platinum, niobium, tungsten, etc.), or non-metallic elements (e.g., nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, etc.), or different chemical compounds (e.g., silanes or amines, etc.), preferably in an amount between 0.5% and 10% by weight, more preferably between 1% and 5% by weight.

[0070] Charged sub-membranes usable in the context of the present invention may be supported by a nanoporous or perforated mechanical substrate onto which at least one material with a suitable surface charge has been deposited. For example, the charged sub-membrane may consist of a flexible polymer membrane onto which a layer of at least one material with a suitable surface charge (such as TiO) has been deposited.

[0071] Nanochannel-containing membranes with inner surfaces essentially formed of or coated with at least one material with an appropriate 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 grafted copolymers, also allow the synthesis of ceramic membranes with regularly oriented nanochannels (e.g., TiO2 membranes)

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

[0072] Alternatively, the surface of a negatively or positively charged material can be chemically modified to enhance the negative or positive charge naturally present on the material after the material is contacted with an electrolyte solution at a given pH. In other words, the surface of the charged submembrane 30B can be chemically modified to enhance the submembrane surface charge. The chemical modification can be effected by chemical vapor deposition, atomic layer deposition, sol-gel coating, or dip coating. Advantageously, the chemical modification can be effected on the surface of the charged submembrane pore walls. For example, the charged submembrane 30B can be obtained from a polycarbonate membrane having an average pore size of <500 nm, preferably <300 nm, and more preferably <200 nm, whose inner pore walls have been chemically modified by dip-coating the polycarbonate membrane in an aqueous solution of polydopamine. At pH=7, polycarbonate has a negative surface charge, which is enhanced when the polycarbonate surface is coated with polyamine.

[0073] In another alternative, when the surface of the membrane material carries ionizable functional groups, the surface charge of the membrane can be modulated using pH. For example, for membrane materials (e.g., TiO2, SiO2, Al2O3, etc.) with -OH groups on their surface, adjusting the pH of the electrolyte solution in contact with the membrane to a basic value (pH = 8-14) will deprotonate the -OH groups, thereby strengthening the negatively charged surface. Thus, pH variation can be used to modulate / control the zeta potential at the membrane surface. Indeed, depending on the pH of the electrolyte solution with which the charged sub-membrane element 30B is in contact, the surface charge of the same membrane can be positive or negative. For example, a charged sub-membrane element 30B essentially made of TiO2 can have a negative surface charge at pH ≥ 9 and a positive surface charge at pH ≤ 6.

[0074] Without wishing to be bound by any particular theory, it is believed that nanochannels of materials with negative surface charges, taking into account their type, size, and physicochemical properties, among others, have their surface charge density in the following order: Titanium dioxide: approx. -100mC / m 2 (at pH ≥ 9) Boron nitride: approx. -1C / m 2 (at pH ≥ 10) Silicon dioxide: approx. -10mC / m 2 (at pH ≥ 6) Polycarbonate: approx. -10mC / m 2 (at pH ≥ 5) Taking this into consideration, it is proposed that the passage of cations (i.e., ions with a charge opposite to the surface charge of the material) is driven via the phenomenon of electroosmosis nanofluidics, which is generated by the application of an AC electric field. The flow of cations from the Debye layer at the interface of the negatively charged membrane surface (which is electrically charged overall because it contains an imbalance of anions and cations under the influence of the surface charge) then induces a flow of solvent in the same direction as the cation flow.

[0075] Furthermore, the composite membrane is characterized by ion transport with a larger current under one voltage sign (e.g., negative voltage) than under the opposite voltage sign (e.g., positive voltage). The asymmetry can be reversed by changing the orientation of the composite membrane with respect to the ground electrode. The asymmetry in ion transport then translates into an asymmetry in EO water transport, which leads to the generation of asymmetric induced water flux. Therefore, under the application of an appropriate AC electric field, a net solvent flow occurs from vessel 10A to vessel 10B through asymmetric membrane element 30. Because asymmetric membrane element 30 includes semipermeable sub-membrane element 30A (which is selective for one or more specific solutes present in electrolyte solution 11A), the flow of cations generated in the pores of charged sub-membrane 30B induces the flow of electrolyte solution 11A from vessel 10A to vessel 10B while preventing the solute from passing through (the solute is filtered and remains in vessel 10A).

[0076] Conversely, it is proposed that nanochannels in materials with a positive surface charge promote the passage of anions (i.e., ions with a charge opposite to that of the material's surface charge) via the phenomenon of electroosmotic nanofluidics, which is generated by the application of an alternating electric field.

[0077] In both cases (cation or anion flow), the solvent flow is induced in the same direction as the cation / anion flow generated under the application of a suitable AC electric field between the first electrode 20A and the second electrode 20B.

[0078] The membrane surface charge can be measured using any suitable process known in the art, for example, the zeta potential of the charged sub-membrane can be elucidated using an electrokinetic analyzer.

[0079] The following equation can be implemented to estimate the zeta potential value on the surface of the membrane:

[0080]

number

[0081] where: 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 surface area of ​​all pores in the membrane exposed to the electrolyte solution, ΔP is the pressure drop across the pore length L, I stream is the electrical streaming current.

[0082] When charged submembranes with low tortuosity porosity (e.g., nanoporous anodic alumina with mostly cylindrical pores) are used, the pore length L can correspond to the thickness of the charged submembrane. For charged submembranes with significant tortuosity pores, calculation of the permeability versus applied pressure allows the total pore length to be determined by applying the relevant tortuosity factor.

[0083] The zeta potential of the membrane surface can be measured at different pH values ​​(acidic, neutral, and basic conditions) by varying the pH of the electrolyte solution using an appropriate acid (e.g., HCl) or base (e.g., KOH, NaOH, etc.) of an appropriate concentration. Preferably, the acid / base will be selected for compatibility with the ions present in the electrolyte solution used in the process / system according to the present invention. For example, when a KCl electrolyte solution is used, KOH can be used as a base to adjust the pH.

[0084] For example, if a minimum |zeta potential| of 5 mV at the membrane surface is desired, a membrane material may be selected that carries a high surface charge, which allows the membrane to maintain a high zeta potential at the surface when in contact with the electrolyte solution.

[0085] The charged sub-membrane element 30B preferably has an average pore size larger than that of the semipermeable sub-membrane element 30A, and 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 reverse osmotic flow of solvent upon application of an appropriate alternating electric field between the first electrode 20A and the second electrode 20B.

[0086] Advantageously, the charged sub-membrane element 30B, having 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 nm and 500 nm, preferably between 1 nm and 300 nm, more preferably between 10 nm and 100 nm, and most preferably between 10 nm and 50 nm.

[0087] As used herein, the term "average diameter" refers to the average inner diameter of a nanochannel. The nanochannel may have a nanotubular, conical, asymmetric, necked, 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, necked, or perforated base morphology, or an elliptical or irregular cross-section, the average diameter corresponds to the average of the smallest and largest inner diameters. The average diameter of a nanochannel can be measured using means 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 within 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.

[0088] Advantageously, in the context of the present invention, nanochannels have a nanotubular, conically asymmetric, necked or perforated base morphology, preferably said nanochannels have a conically asymmetric morphology.

[0089] Morphological parameters of charged sub-membranes usable in the context of the present invention can be assessed using conventional techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal scanning laser microscopy (CSLM), and transmission electron microscopy (TEM). Alternatively or additionally, X-ray computed tomography (microCT), 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 3D (volume) analysis). These techniques can assess morphological parameters of charged sub-membranes according to the present invention, such as pore size, pore size distribution, surface roughness, molecular weight cutoff, and thickness.

[0090] Pore ​​size refers to the dimensions of pores, which are channels of variable cross-section. The distance between two opposing pore walls is used as the pore size for simple geometries (typically the diameter of cylindrical pores for pore sizes > 2 nm and the width of slit-shaped pores for pore sizes < 2 nm). When pores have irregular shapes, some averaging is performed to report the average pore size. Processes for measuring pore size, average pore size, and pore size distribution of porous materials are well known in the art (see, for example, ISO 15901 standard), and include some statistical analysis using models such as nonlinear optimization and Monte Carlo integration for materials in which the pores do not all have the same size and / or geometry. Given the chemical and physical properties of the charged sub-membrane element 30B and the range of the average pore size (preferably, the average diameter of the nanochannels of the charged sub-membrane element 30B can be between 1 nm and 500 nm, preferably between 1 nm and 300 nm, more preferably between 10 nm and 100 nm, and most preferably between 10 nm and 50 nm), the average pore size can be measured by nitrogen gas adsorption at -196°C (liquid nitrogen temperature) according to the ISO 15901 standard.

[0091] Charged submembranes usable in the context of the present invention may have a non-uniform pore size distribution across the membrane thickness, or a uniform pore size distribution across the membrane thickness. Typically, for charged submembranes with a non-uniform pore size distribution, there is a very thin, dense surface layer acting as a functional layer on top of a porous sublayer with a specific pore diameter. Charged submembranes with a non-uniform pore size distribution consist, for example, of a 0.1-1 μm thick skin layer (selective barrier) on top of a highly porous 100-200 μm thick substructure. The pore size of the porous sublayer can be as low as ≦1 nm or as high as 500 nm, with the pore size range defining the type of application for which the charged submembrane can be used: microfiltration (50-500 nm), ultrafiltration (1-50 nm), and nanofiltration (≦1 nm). Pore size and its distribution can be determined by numerical analysis of pore dimensions observed in electron micrographs of membrane cross sections. The pore size figures given above represent the arithmetic mean of the pore size distribution observed by scanning electron microscopy (SEM) across the membrane cross section.

[0092] Advantageously, the average cross section of the charged sub-membrane nanochannels and their particular regular perforation morphology promote good diffusion of the solution through the membrane. Thus, the charged sub-membrane element 30B sets itself apart from the semipermeable sub-membrane element 30A, potentially allowing the circulation of both water molecules and ions through its pores (because, advantageously, each pore has a cross section larger than the size of these molecules).

[0093] Furthermore, the closest distance between the semipermeable sub-membrane 30A and the charged sub-membrane 30B reduces the overall electrical resistance of electroosmotic diffusion, thus reducing the benefits to process performance. Therefore, the semipermeable sub-membrane 30A is preferably overlapped with the charged sub-membrane 30B.

[0094] 1.3. Exemplary Features of Composite Membrane Filtration Systems In an exemplary embodiment, processes and systems according to the present invention may use an asymmetric membrane comprising a semipermeable sub-membrane 30A, a charged sub-membrane 30B having a surface charge with a |zeta potential| of ≧5 mV, and a particularly advantageous selection of electrodes 20A and 20B.

[0095] The semipermeable sub-membrane 30A can be selected from a nanoporous carbon membrane or a laminated membrane of lamellar material. The nanoporous carbon membrane or laminated membrane of lamellar material can be as previously described. The nanoporous carbon membrane pore size can be in the range of 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. For example, the semipermeable sub-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, and most preferably a multilayer MoS2 membrane. Advantageously, the semipermeable sub-membrane 30A can be a size-exclusion selective membrane composed of stacked graphene oxide flakes.

[0096] The charged sub-membrane 30B, having a surface charge with a |zeta potential| of ≧5 mV, can be made from titanium dioxide, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide; preferably titanium dioxide, boron nitride, SiO2, polycarbonate, and anodized aluminum oxide; most preferably titanium dioxide, polycarbonate, and anodized aluminum oxide.

[0097] The semipermeable sub-membrane 30A is preferably overlaid with the charged sub-membrane 30B. The semipermeable sub-membrane may be placed directly on top of the charged sub-membrane element 30B, or, as previously described, may first be placed on a separate porous support layer (33) (e.g., for ease of manufacturing and / or handling) before being placed on top of the charged sub-membrane element 30B.

[0098] The first and second electrodes 20A and 20B can be any metal or carbon electrode capable of exhibiting 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 graphitic carbon electrodes, or any carbon electrodes 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 have the advantage of allowing the filtration system of the present invention to operate under a wide range of voltages (on the order of 0.1 V to 1 kV, preferably between 0.1 V and 100 V, more preferably between 1 V and 50 V) that exhibit limited catalysis of parasitic electrochemical reactions.

[0099] 2. Asymmetric membranes containing one material An exemplary embodiment is illustrated in FIG. 1(b).

[0100] In another variation, the asymmetric membrane element 30 may be a single-material asymmetric membrane element, with the semipermeable sub-membrane element 30A and the charged sub-membrane element 30B being one and the same element to form a single asymmetric membrane 30A. Advantageously, the single-material asymmetric membrane 30A may have a predetermined pore size and zeta potential adapted to the target solute to be concentrated / depleted or rejected / filtered. Advantageously, the single-material asymmetric membrane 30A may have an average pore size adapted to filter 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.

[0101] For example, the average pore size of the asymmetric membrane 30A containing 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 containing one material, while allowing the solvent and other smaller-sized solutes to pass through the asymmetric membrane 30A containing one material. The average pore size of the asymmetric membrane 30A containing one material will be adapted depending on the intended application type: microfiltration (50-500 nm), ultrafiltration (1-50 nm), or nanofiltration (≦1 nm). Advantageously, the asymmetric membrane 30 containing one material can have a porosity (i.e., average pore size as measured according to the ISO 15901 standard) of <500 nm, preferably <300 nm, more preferably <100 nm, and most preferably <50 nm. In a preferred variant, the filtration system is for ultrafiltration, and the asymmetric membrane 30A containing one material can have a porosity (average pore size) between 1 and 50 nm.

[0102] The elements of the asymmetric membrane comprising one material may be charged sub-membranes having an appropriate (positive or negative) surface charge, as generally described in any of the above variations, including the preferred and advantageous variations, and an average pore size adapted to exclude / filter the target solute from the electrolyte solution 11A, as described in the immediately preceding paragraph. The portion of the description relating to the charged sub-membranes will not be repeated here for the sake of brevity, but it will be understood that it is applicable mutatis mutandis to elements of the asymmetric membrane comprising one material.

[0103] Advantageously, the asymmetric membrane 30A comprising one material may be a charged sub-membrane essentially formed from a material having a surface charge (positive or negative) with a |zeta potential| of ≧5 mV, preferably ≧20 mV, most preferably ≧50 mV, such as, for example, TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, or polyelectrolyte layer polymer membranes (such as charged sub-membranes obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) onto a polycarbonate membrane); preferably TiO2, BN, SiO2, polycarbonate, anodic alumina, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc, cellulose, or polyelectrolyte layer polymer membranes; most preferably TiO2, BN, anodic alumina, SiO2, or polycarbonate.

[0104] Advantageously, the asymmetric membrane 30A comprising one material may be a size-exclusion selective membrane coated with a material having a surface charge (positive or negative) on its inner pore walls, with a |zeta potential| of ≧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, Ni2dobdc, Mg2dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, or polyelectrolyte layer polymer membranes (such as charged sub-membranes obtained by sequentially dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) onto a polycarbonate membrane); preferably TiO2, BN, SiO2, polycarbonate, anodic alumina, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc, cellulose, or polyelectrolyte layer polymer membranes; most preferably TiO2, BN, anodic alumina, SiO2, or polycarbonate.

[0105] 3. Asymmetric membranes containing two materials An exemplary embodiment is illustrated in FIG. 1(c).

[0106] In another variation, the asymmetric membrane element 30 may be an asymmetric membrane element comprising two materials of the same nature, where at least one physical and / or one chemical parameter differs between one material and the other; preferably, the asymmetric membrane comprising two materials may be a membrane comprising first and second sides made from the same material, where the pore sizes of each side are different.

[0107] For example, an asymmetric membrane comprising two materials may include a first side made from polycarbonate and having a pore size of 200 nm, and a second side made from polycarbonate and having a pore size of 10 nm pores.

[0108] Vessels 10A and 10B In the present invention, any asymmetric membrane element 30 separating vessels 10A and 10B can be used without particular limitation, as long as it does not allow solutes to permeate therethrough and allows primarily solvent to permeate therethrough. Advantageously, asymmetric membrane element 30 can be adapted to achieve a solute rejection of preferably 98.0% or greater, preferably ≧98.5%, more preferably ≧99.0%, still more preferably ≧99.5%, and most preferably 100%, or about 100%.

[0109] To carry out the process according to the invention, one may use a separation device / system comprising two vessels separated by an asymmetric membrane element 30. In this situation, the mixture to be separated is placed in the first vessel (vessel 10A) and the extracted solvent is recovered in the second vessel (vessel 10B).

[0110] In the present invention, the reverse electroosmosis filtration / purification system can be run in a batch or continuous mode to maximize its effectiveness.

[0111] Preferably, the reverse electroosmosis filtration / purification system may be operated in a continuous manner.

[0112] Advantageously, the first and second vessels may be configured with an outlet pipe 402 (FIG. 7) to allow gas bubbles generated during the parasitic electrochemical reaction to be expelled by the Venturi effect.

[0113] Preferably, the first and / or second vessel may include an outlet pipe, or the outlet pipe may be connected to the top of the first and / or second vessel. Preferably, the outlet pipe may be made of the same material as the vessel. Preferably, the outlet pipe may have a circular, square, or oval shape.

[0114] Preferably, the first and / or second vessel may include a wall portion 401 and an outlet pipe 402, the outlet pipe 402 being subdivided into two parts, namely a pipe sub-vessel 402A and a hyperbolic sub-vessel 402B, the pipe diameter being w, the larger opening of the hyperbolic sub-vessel having dimension y, the narrower opening of the hyperbolic sub-vessel having dimension x, and the height of the hyperbolic sub-vessel having dimension z.

[0115] Preferably, the width w of the outlet pipe is 0.1 to 1000 times larger than the outlet width x of the vessel, more preferably 0.5 to 10 times larger, and even more preferably 0.3 to 3 times larger.

[0116] Preferably, the vessel outlet width x is 0.1 to 1 times, more preferably 0.2 to 1 times, and even more preferably 0.5 to 1 times larger than the vessel width y as measured at the bottom of the vessel height.

[0117] Preferably, the height z of the vessel is 0.1 to 5 times, more preferably 0.2 to 5 times, and even more preferably 0.5 to 2 times greater than the width y of the vessel as measured at the bottom of the vessel height.

[0118] More advantageously, the first and second vessels 40A and 40B have a geometry that allows for compression of the first and second electrodes.

[0119] The vessels described above are adapted for static mode. To apply the tangential mode, the first and second vessels 40A and 40B can independently include one or more fluid inlets depending on the process being applied. For example, appropriate valves and / or tubing (depending on the pressure range of the compartments) can be connected to the first and / or second vessels or both to allow tangential fluid flow inside the vessels and along the membrane surface. The first and / or second vessels can also be connected to one or several external tanks, each of which can contain an electrolyte. For example, the valves can be stream valves, diaphragm valves, needle valves, or even pressure relief valves. For example, the tubing can be metal or polymer tubing. Those skilled in the art will know which tubing and valves to select and how to assemble them to form a closed tangential circulation of electrolyte along the membrane surface depending on how the process is implemented.

[0120] The first and second vessels 40A, 40B may also be coupled to a pressure generator, which may be a pump, a vacuum delivery unit, or a chemical gradient concentration between both electrolytes. Thus, the process according to the invention may be a pressure-assisted AC voltage-induced reverse osmosis process, in addition to the flow induced by the electric field applied in step iii) of the process according to the invention.

[0121] For example, the reverse electroosmosis filtration / purification system according to the present invention may be configured in multiple stages, i.e., multiple units of "vessel 10A-asymmetric membrane element 30-vessel 10B".

[0122] In an exemplary variation, a reverse electroosmosis filtration / purification system may be provided that includes N vessels (10) and N-1 asymmetric membrane elements 30, where N is an integer. For example, N may range from 3 to 100, more specifically, from 3 to 50. In this multi-vessel device, the vessels and asymmetric membrane elements may be as defined above. Thus, an assembly may be formed from alternating vessels (10) that contain alternately concentrated and less concentrated electrolyte solutions with respect to the solute of interest, separated from each other by the asymmetric membrane elements 30. The expression "concentrated with respect to the solute" above means that the feed electrolyte solution contains a higher concentration of the solute than the eluted electrolyte solution.

[0123] solvent Advantageously, the solvent of the first electrolyte solution 11A and the solvent of the second electrolyte solution 11B may be the same or different.

[0124] Advantageously, the solvent of the first electrolytic solution 11A and the solvent of the second electrolytic solution 11B are independently selected from polar or non-polar solvents, and preferably, the solvent of the first electrolytic solution 11A and the solvent of the second electrolytic solution 11B are independently selected from water, one or more organic solvents, or mixtures thereof.

[0125] As used herein, the term "polar solvent" does not depart from its conventional meaning and common knowledge / usage in the art. Generally, polar solvents include, but are not limited to, aprotic solvents and protic solvents having a dielectric constant of ≧6 and a dipole moment of ≧1.50 D.

[0126] Preferably, the polar solvent may be advantageously a solvent capable of generating acidic ions, for example, water, alcohol (such as methanol or ethanol), a water-alcohol mixture, formic acid, acetic acid, hydrogen fluoride, ammonia, acetone, or acetonitrile.

[0127] For example, the non-polar solvent may be hexane, pentane, cyclohexane, cyclopentane, toluene, 1,4-dioxane, or benzene.

[0128] Electrolyte solutions 11A and 11B and solutes The electrolyte solution usable in the context of the present invention can be any electrolyte solution containing at least one solute of interest / undesirable solute in a solvent as defined above.

[0129] In a preferred variation, the electrolyte solution can be an aqueous solution containing electrolytes. The electrolyte can be of any chemical type, as long as it is dissolved in the solution in the form of charged ions. Preferably, these ions are derived from dissolved salts, such as NaCl, KCl, CaCl, and MgCl. The electrolyte solution can be a synthetic solution; a natural solution, such as freshwater from a lake or river, groundwater, brackish water, seawater, industrially produced water, petroleum-produced water, or a biological solution / fluid.

[0130] Examples of solute-containing aqueous solutions to be used as electrolyte solutions according to the present invention include seawater, brackish water, cellular metabolic products, reaction products, biological fluids, etc., where cellular metabolic products are intended to include animal cells, plant cells, or microbial cultures, their primary metabolites, secondary metabolites, in vitro secreted proteins, and biotransformation products.

[0131] Examples of reaction solutions include chemical reaction products and enzymatic reaction products.

[0132] Examples of microbial primary metabolites include, but are not limited to, organic acids (e.g., acetic acid, propionic acid, butyric acid, lactic acid, and succinic acid), alcohols (e.g., ethanol and butanol), hexane, amino acids (e.g., lysine and tryptophan), vitamins, and polysaccharides.

[0133] Examples of microbial secondary metabolites include antibiotics (e.g., penicillin, etc.), enzyme inhibitors, and physiologically active substances (e.g., taxol, etc.), and examples of in vitro secreted proteins of microorganisms include enzymes (e.g., amylase or cellulase, etc.), insulin, interferon, monoclonal antibodies, etc. In addition, microbial biotransformation products are substances produced by using microorganisms or enzymes, examples of which include, but are not limited to, steroids, etc.

[0134] Examples of biological fluids include blood, serum, plasma, urine, saliva, tears, dialysate, intestinal contents, parenteral nutrition solutions, seminal plasma, and cerebrospinal fluid.

[0135] Preferably, the electrolyte solution may be an aqueous solution containing a solute selected from alkali or alkaline earth halides, preferably selected from NaCl, KCl, CaCl2, and MgCl2, and more preferably the solute is NaCl.

[0136] The solute may be selected from solid particles, organic or inorganic small molecules (e.g., dye complexes (e.g., tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate), etc.), biomolecules (e.g., hormones (e.g., testosterone), proteins, polysaccharides, polynucleotides, polypeptides, enzymes, or antibodies), pollutants (e.g., from wastewater, industrial production water, or landfill leachate), metabolic waste, or salts / ions. When the solute of interest to be concentrated is a solid, it is preferably a material that readily crystallizes depending on temperature and pH and is not highly viscous even at high concentrations.

[0137] Advantageously, the solute is one of the following solutes: calcium (Ca 2+ ), magnesium (Mg 2+ ), sodium (Na + ), potassium (K + ), carbonate ions (CO3 2- ), bicarbonate ion (HCO3 - ), sulfate ions (SO4 2- ), chloride ions (Cl - ), nitrate ions (NO3 - ), or phosphate ions (PO4 3- ), solid objects such as microplastics, or any colloid or suspension, macromolecules or micropollutants in solution such as hormones, pesticides, antibiotics, dyes, chemical compounds, neuroactive agents, steroids, per- and polyfluoroalkyl substances (PFAS), or mixtures thereof.

[0138] 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 process is saltwater desalination. As such, the present invention is also directed to a saltwater desalination system including a reverse electroosmosis filtration system according to the present invention, in any of the variations described herein.

[0139] The present invention is also directed to a water purification system including a reverse electroosmosis filtration system according to the present invention, in any of the variations described herein. For example, the water contaminants to be filtered may include pharmaceutical drugs, endocrine disruptors, hormones, pesticides, and / or dyes.

[0140] More precisely, in one aspect, the invention relates to a process for purifying water and liquids containing impurities, implementing the electro-reverse osmosis technique.

[0141] By water purification, it is generally meant any operation consisting of treating water containing impurities at an initial content, so that at the end of this operation the final content of impurities is lower than the initial content. By impurities it is meant the removal of elements that constitute pure water (i.e. HO, OH, - , and H + ) means any element, molecule, ion, or the like that is different from the element (or elements) in the purification process. The purification process may be, for example, a process for desalinizing seawater, a process for treating industrial produced water, or a process for treating landfill leachate.

[0142] Thus, in one aspect, the present patent application advances a methodology for recovering potable water from vast sources of saltwater, particularly surface waters containing various concentrations of sodium chloride, in applications ranging from less than 1% to 20% salinity, such as for waters with the following salinities: brackish water with a salinity of 0.5% to 3.5%, seawater with a salinity of 3.5 to 4.5%, and brine water with a salinity of 5% to 20%.

[0143] In the present invention, the solute-containing electrolyte solution can be a biological fluid, preferably a dialysate. As such, the present invention is also directed to an implantable artificial kidney comprising a reverse electroosmosis filtration system according to the present invention, in any of the variations described herein.

[0144] The principle underlying the present invention is that asymmetric membrane element 30 (a single asymmetric membrane comprising one material) or at least a portion thereof (a composite membrane comprising semipermeable sub-membrane element 30A and charged sub-membrane element 30B) has sufficient surface charge (which can be positive or negative) to induce a zeta potential at the membrane / electrolyte solution interface that is sufficiently high to induce the flow of anions or cations, respectively, through the nanochannels of the charged sub-membrane when an appropriate alternating electric field is applied between electrodes 20A and 20B. This phenomenon is governed by the same principles of zeta potential applied to colloidal particle suspensions.

[0145] In the case of colloidal suspensions, the fact that many organic and mineral colloidal particles possess negative charges in aqueous environments causes them to repel each other, maintaining the stable state of dispersion that characterizes them. The electrochemical dispersion of colloidal particles has been studied for many years. Several models (e.g., double layer and DLVO theory) have been developed to explain colloidal stability. The double layer model predicts that when suspended particles exist in a liquid phase, an inner dense layer at the surface of each particle (composed of ions in solution that are attracted by the particle's charge) exhibits a charge of opposite polarity to the particle's own native charge under the physical and chemical conditions of the suspension. An outer layer of opposite polarity (also composed of ions in solution) is diffused within a given distance from the particle's surface. The net electric potential between the two layers (commonly referred to in the art as the zeta potential) generates a repulsive force that counteracts the attractive van der Waals forces between the particles. If the outer layer is spread over a wide enough radius, thereby increasing the influence of the zeta potential, the particles will be held apart and remain in stable suspension. On the other hand, if the radius of spread of the outer layer is reduced to the point where the van der Waals forces are overcome, the particles will be attracted together and form agglomerates that have a tendency to separate from the liquid phase.

[0146] Extending this principle to the present invention, a dense layer on the surface of the inner pore wall of the charged submembrane (composed of ions in the electrolyte solution attracted by the surface charge present on the surface of the inner pore wall of the charged submembrane) exhibits a charge of opposite polarity to the natural charge of the charged submembrane itself under the physical and chemical conditions of the electrolyte solution. An outer layer of opposite polarity (also composed of ions in the solution) is diffused within a given distance from the surface of the charged submembrane. 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. Thus, it characterizes the distribution of charge on the surface of the inner pore wall of the charged submembrane.

[0147] As such, the zeta potential depends on the ionic strength of the electrolyte solution and the concentration of ions in the solution around the membrane surface.

[0148] To increase the zeta potential and improve the reverse osmotic flow generated on either side of the asymmetric membrane element, the pH of the electrolyte solutions 11A and 11B can be adjusted as a function of the isoelectric point of the inner surface of the nanochannel of the charged submembrane 30B (composite membrane element or asymmetric membrane element comprising two materials) or 30 (asymmetric membrane element comprising one material).

[0149] The effect of pH on membrane surface charge can be studied by measuring the zeta potential of charged submembrane samples in electrolyte solutions of different pH. The zeta potential of the charged submembrane can be driven toward negative values ​​with increasing pH values ​​of the electrolyte solution. For example, one mechanism by which increasing pH drives the zeta potential toward negative values ​​is the deprotonation of species (e.g., OH to O) at the surface of the membrane inner pore walls. - to (e.g., at the surface of a TiO2 or SiO2 film).

[0150] 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 up to more than 14 pH units.

[0151] 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 units. For example, when the solution to be purified is brackish water contaminated with acidic or basic 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.

[0152] For example, when a ceramic charged submembrane (e.g., a TiO or BN charged submembrane) is used, 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 negative charges 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), to obtain positive charges on the inner surface of the nanochannel. The increase in the negative zeta potential value of the charged submembrane with increasing pH can occur, for example, due to deprotonation of functional groups on the membrane surface.

[0153] As used herein, "pHiso" refers to the pH at the isoelectric point of the material comprising the interior surface of the nanochannel. pHiso is measured using methods known to those skilled in the art, particularly by potentiometric acid-base titration methods.

[0154] Preferably, the temperatures of the first electrolyte solution 11A and the second electrolyte solution 11B differ by 1°C or more, more preferably 10°C or more, more preferably 50°C or more.

[0155] When the solute-containing electrolyte solution is an aqueous solution, the aqueous solution may have a pH of 0 to 14, depending on the nature of the charged submembrane and the surface charge naturally present thereon, as well as the temperature at which the water is maintained in the liquid state (e.g., 0°C to 100°C, preferably 15°C to 50°C, more preferably 20°C to 40°C). The temperature may be higher or lower than those recited above. For example, other solute / solvent mixtures may have temperatures that deviate from those recited above.

[0156] Electrodes 20A and 20B As previously discussed, each of the vessels 10A and 10B of the purification / filtration system according to the present invention includes electrodes (20A and 20B, respectively) positioned such that the electrodes are in contact with the electrolyte solution (11A and 11B, respectively).

[0157] Different types of electrodes can be used in the context of the present invention.

[0158] Advantageously, porous electrodes, grid electrodes, or any geometric shape through which the electrolyte can diffuse can be used. More advantageously, the electrode can contain cavities or pores in a range of sizes ranging from 0.1 nm to 1 mm.

[0159] Advantageously, 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.

[0160] More advantageously, the cation or anion (e.g., Na + or Cl - Any type of electrode capable of collecting the flow of ions (ions) can be used, preferably silver and silver chloride (Ag / AgCl), carbon and platinum (C / Pt), carbon (C), graphite, or type [Fe(CN)6] 4- / [Fe(CN)6] 3-The first and second electrodes 20A and 20B are electrodes composed of an iron complex of Zn, Fe, Pt, and Au. The first and second electrodes 20A and 20B can be any metal or carbon electrode capable of having 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 graphitic carbon electrodes, or any carbon electrodes used in salt batteries. Advantageously, the first and second electrodes 20A and 20B can be platinum electrodes. Advantageously, the first and second electrodes 20A and 20B can be carbon electrodes. The advantage of using carbon electrodes is that they allow the filtration system according to the present invention to operate under a wide range of voltages (on the order of 0.1 V to 1 kV, preferably between 0.1 V and 100 V, more preferably between 1 V and 50 V) that exhibit limited catalysis of parasitic electrochemical reactions.

[0161] The electrodes 20A and 20B can be partially or completely immersed in the electrolyte solution (11A, 11B), respectively. The electrodes 20A and / or 20B can also be provided in the form of at least one portion of the wall of the vessel 10A and / or 10B. The electrodes 20A and 20B are both connected to a source of electrical energy 40, which allows for the generation of an alternating electric field between the electrodes. The electrodes can be connected to the source of electrical energy 40 via a simple cable.

[0162] Sources of Electrical Energy40 In the systems and processes according to the present invention, the source of electrical energy 40 may be any suitable source of electrical energy known in the art.

[0163] Advantageously, the source of electrical energy is generated by a device that delivers only a DC voltage and is coupled to a DC / AC converter, or by a device that delivers an alternating current electrical signal.

[0164] For example, it may be a battery, a generator, a mains power supply, a solar panel, or any other source of an electrical signal.

[0165] In the present invention, the purpose of electrical energy source 40 is to generate an AC electric field between electrodes 20A and 20B.

[0166] Advantageously, the source of electrical energy 40 may include one or more batteries. As such, the reverse electroosmosis filtration system according to the present invention may be a portable / mobile system. For example, the source of electrical energy 40 may be configured to be charged by light, and may include, among other things, a solar cell or a photodiode.

[0167] Advantageously, the source of electrical energy 40 may be configured to be charged by using the reverse electroosmotic effect to pump an electrolyte solution through the asymmetric membrane element 30. To that effect, the source of electrical energy 40 may include a water turbine element operably connected to the asymmetric membrane element 30.

[0168] Here, the net electroosmotic flow Q EO is defined. Q EO can be calculated by the following formula (Formula III):

[0169]

number

[0170] 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), and μ EO is the effective EO mobility, and ΔV m is the local electric field at the membrane location (V), and L is the membrane thickness (m). r can be calculated based on the average value of the global pore radius.

[0171] A net electroosmotic flow is directed from the first electrolyte 11A to the second electrolyte 11B.

[0172] 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.

[0173] Separator 60 As used herein, separator 60 can independently be an organic, inorganic, or insulating composite material.

[0174] Separator 60 should have a much larger pore size to allow permeation of the electrolyte solution 11A solvent flow from vessel 10A to vessel 10B through asymmetric membrane element 30. As such, separator 60 preferably has a pore size at least 5, 10, or even larger than the pore size of semipermeable sub-membrane element 30A, and a thickness of 30 μm to 300 μm, more preferably 30 μm to 100 μm, preferably as thin as possible to reduce the distance between electrodes and, therefore, resistance. Separator 60 can be made from a neutral (no surface charge), non-reactive polymeric material, such as a fluoropolymer (e.g., polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE)), or a mixed cellulose ester or cellulose acetate, porous cellophane, nylon, or polyolefin film. Separator 60 can also be made from a porous ceramic material such as, by way of non-limiting example, alumina, or a silica-based porous ceramic.

[0175] In some embodiments, the system can include a second separator 60 positioned between electrode 20A or electrode 20B and the second side 30B of the asymmetric membrane element 30.

[0176] Preferably, the system includes only one separator 60, reducing the distance between the first electrode 20A and the second electrode 20B to its maximum extent, thereby reducing the overall resistance of the cell.

[0177] air bubbles As used herein, "gas bubbles" refers to small spheres that rise to the surface of a liquid filled with air or gas, including oxygen, hydrogen, chlorine, or any other gaseous compound, in response to an electrochemical reaction in response to a solvent or mixture thereof.

[0178] Current collectors 70A and 70B As used herein, current collectors 70A and 70B may be made of 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- The conductive materials may be independently selected from conductive materials such as

[0179] Flow Control (50) The reverse electrochemical flux through the asymmetric membrane element according to the present invention can be controlled using different parameters: (i) Surface charge of charged sub-membranes: Flux across a membrane element can be increased by membranes with higher surface charge. The surface charge can be adjusted by the choice of materials, any chemical modifications that may be applied to modify the membrane surface charge, and the pH of the electrolyte solution in contact with the charged sub-membrane surface. Advantageously, a minimum surface charge with a |zeta potential| of ≥ 5 mV is suitable, more preferably ≥ 20 mV, and most preferably ≥ 50 mV. The membrane surface charge can be adjusted based on the choice of materials comprising the charged sub-membranes and / or based on the ionic strength / concentration of the electrolyte solution in contact with the membrane, as previously explained. (ii) Pore size: For semipermeable sub-membranes (e.g., when composite membranes are used), the pore size will necessarily depend on the size and / or chemical properties of the solutes to be filtered / separated. For charged sub-membrane elements (which fulfill the "pumping function" in the system), the larger the pore size, the greater the electroosmotic flow that will be generated (see Formula III). There are no other specific constraints on the pore size, except in cases where the charged sub-membrane element also serves as a size-exclusion-type semipermeable sub-membrane (e.g., as in the case of the single-material asymmetric membrane elements described herein, in which the average pore size of the charged sub-membrane should be adapted to the size of the solutes to be separated / filtered). This applies to variations in which composite membranes are used, as well as variations in which asymmetric membranes containing two materials or single-material asymmetric membranes are used (i.e., when dual semipermeable / charged membrane elements are used, as in Figure 1(b)). Advantageously, the average pore size of the charged sub-membrane element (which fulfills the function of electrically conducting the flow of solvent through the system) may be >10 nm, preferably >100 nm, more preferably >1 μm, most preferably >500 μm. (iii) Pore Geometry: In general, the semipermeable submembrane need not have a well-defined pore geometry (it can be, for example, "spaghetti-like"). For charged submembrane elements, there are no specific constraints regarding pore geometry: the system will work with any pore geometry, ranging from materials with symmetrical pore shapes (e.g., anodized aluminum characterized by cylindrical pores) to materials with highly tortuous porosity (e.g., nylon or polycarbonate characterized by conical pores) (provided the charged submembrane material has an appropriate surface charge, as further detailed herein). For example, porosity associated with nanotubular morphology, i.e., cylindrical pores with circular cross-sections, conical asymmetric pore shapes, honeycomb pore geometries, hourglass-shaped porosity, etc., can be used. Electroosmotic flow across the charged submembrane can be optimized by modulating the membrane's pore geometry. This can be achieved empirically by varying the pore geometry of a given charged sub-membrane using methods well known in the art. Generally, flux can be optimized when the membrane pore geometry is preferably symmetrical, with little or no tortuosity. As such, a nanotubular morphology (i.e., circular cross section) will have the effect of increasing flux across the membrane, as opposed to, for example, a conical asymmetric pore shape. (iv) Electric Field Strength: For a given charged submembrane 30B and membrane surface area exposed to the electrolyte solution in a system according to the present invention, the flow rate increases as the applied current (and therefore the electric field) between the electrodes increases. 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 AC field are selected to maximize flow. It will also depend on the number of pores through which electroosmotic flow can be induced, and therefore on the surface area of ​​the charged submembrane in contact with the electrolyte solution, and the surface pore density of the charged submembrane. Typically, a flow vs. strength (or current) curve is plotted for given conditions, such as the pH concentration in the electrolyte solution, 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 is preferably adapted depending on the electrodes and / or membrane used. (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 is preferably in the range of 0.1 mM to 100 mM, preferably 0.1 mM to 50 mM, more preferably 0.1 mM to 10 mM, and most preferably 1 mM to 10 mM.

[0180] In summary, using a composite asymmetric membrane with nanometer average pore size (<500 nm), which has a significant surface charge, we have developed a filtration process based on the application of an AC electric field. When the membrane separates two vessels containing water (or other solvent) and a mobile electrolyte (e.g., a salt), the application of an AC electric field between the two vessels of the cell generates electroosmotic flow (the movement of water / solvent from one cell to the other in a direction opposite to the normal osmotic flow), which can be expressed for each single pore by the following formula (Formula III):

[0181]

number

[0182] where V is the net liquid volume (L) in the direction of electroosmotic flow, t is the time of the experiment (s), ω is the frequency (Hz), r is the pore radius (m), and μ EO is the effective EO mobility, and ΔV m is the local electric field at the membrane location (V) and L is the membrane thickness (m).

[0183] Moreover, the separator 60 makes it possible to protect the membrane from any mechanical deformation when closing the cell, preventing any short-circuits if the membrane is damaged during the process.

[0184] The present invention offers a complementary advantage: the porous electrode nature and vessel morphology allow for bubble evacuation and therefore no bubble accumulation. Indeed, any gas bubbles formed due to parasitic electrochemical reactions can reduce the active membrane surface if not evacuated. In the present invention, the vessel morphology allows for optimized bubble evacuation and limits bubble accumulation along the membrane surface.

[0185] As previously discussed, the scarcity of drinking water resources is a major international concern. On the one hand, certain industrial wastes (especially pharmaceutical and chemical wastes) pose major problems for treatment plants. On the other hand, some arid countries make extensive use of reverse osmosis desalination processes to obtain drinking water. However, the energy costs of these processes significantly increase not only the price of water but also the price of the equipment.

[0186] AC electrofiltration eliminates the need for high pressures in conventional water treatment processes. For example, low-pressure desalination requires the application of pressures exceeding the osmotic pressure (>30 bar), seawater desalination requires the application of pressures >60 bar, and brine treatment requires the application of pressures >120 bar. These processes are expensive and complex to implement. The application of AC electric fields reduces water treatment costs, even for larger molecules (e.g., hormones, drugs) that are sometimes difficult to remove. Furthermore, combining this filtration process with the use of 2D nanomaterials (e.g., graphene oxide or boron nitride) allows for the use of membranes with tunable porosity, as the 2D nanochannels can be easily chemically and geometrically modified, thus improving the feasibility of purification applications and improving permeability / selectivity thresholds.

[0187] Applying an AC voltage has the main advantage of avoiding effects due to charge polarization or electrode saturation. However, this technique cannot be applied to symmetric membranes because the average water flux over the cycle is zero. On the other hand, in nanocomposite membranes that display highly asymmetric transport, the average water flux over the cycle is non-zero, which leads to net mass transport from one side of the asymmetric membrane to the other.

[0188] The present invention reduces the use of alternating current electric fields to induce separation and filtration, as opposed to standard processes (typically of the reverse osmosis type) that rely on mechanical forces due to pressure differences. Thus, the present invention provides a filtration process based on the application of an alternating current electric field, rather than on concentration differences (e.g., direct osmosis) or pressure differences (reverse osmosis). This offers enormous economic advantages, including cheaper equipment, the fact that it is cheaper to apply electricity than pressure, and the avoidance of mechanical stress (which is not the case here, as pressures of the order of 50 bar are typically applied to membranes). Therefore, the use of specialized membrane materials that cannot mechanically withstand the high mechanical pressures of reverse osmosis can be considered. This also has significant ecological advantages, since it can provide an upstream solution for the filtration of complex molecules that would otherwise be rejected in a purification plant. For example, an AC electrofiltration system according to the present invention could be installed in a pharmaceutical or textile plant for the pretreatment of wastewater.

[0189] Thus, the present invention provides a highly valuable alternative for filtration / clarification and water treatment processes that overcomes the shortcomings of existing processes.

[0190] (Example) The processes and systems according to the present invention and their reduction to practice can be further understood by the examples that illustrate how some of the processes may be carried out, although it will be recognized that these examples should not be construed as limiting the invention.

[0191] Abbreviation GO: graphene oxide PC: Polycarbonate MoS2: Molybdenum disulfide

[0192] material and method A commercial graphene oxide aqueous dispersion with a concentration of 0.4 wt% was purchased from Gographene SA.

[0193] The polycarbonate track-etched membrane was supplied by Sterlitech Corporation.

[0194] Potassium chloride (>99%), tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (99.95%), and testosterone (>99.9%) were purchased from Sigma-Aldrich.

[0195] All experiments were carried out at room temperature (25±3°C) and neutral pH.

[0196] The experiment was carried out using a potentiostat (Bio-logic, SP200) for electrical induction and measurement. The potentiostat was connected to the electrodes using thin platinum wires (0.5 mm diameter). The flow response of the system was measured using a flow sensor (Sensirion, SLF3S-0600F), with a sampling frequency limit of 1 ms.

[0197] For DC voltage experiments, a voltage drop was applied to the electrodes for 30 minutes. Current and flow rates 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 voltage application, the electrodes were regenerated to avoid polarization effects on the next experiment. This regeneration phase can be performed by short-circuiting inside a distilled water solution, reversing the polarity, or forcing a return to equilibrium (by applying 0 V until the current reached a fairly low value (<1 mA)), as commonly described in the literature. All experiments presented here were performed by applying 0 V to the system between each test.

[0198] For AC voltage experiments, the frequency sampling of current and flow is chosen to capture a sufficient number of data points (>10) per period for the analysis. For DC voltage experiments, the system is returned to equilibrium between each measurement.

[0199] Example 1 Preparation and characterization of composite membranes Example 1 is set up in the system of FIG. 1(a).

[0200] The composite membrane was fabricated by depositing a 2D nanolaminate of GO 30A onto a commercially available macroporous polymer substrate 30B (Whatmann, PC membrane, pore size: 0.2 μm, pore density: 2×10 pores / m). 2 ) was deposited on the

[0201] A dispersion of GO in water was purchased from Graphenea SA (0.1% aqueous solution), which was diluted, sonicated for a further 10 min, and centrifuged twice at 3000 rpm to remove aggregates and obtain a monolayer dispersion.

[0202] The overall VIRO composite membrane was synthesized by depositing a 2D-based filter using vacuum filtration: a solution of exfoliated monolayer nanosheets dispersed in water was added dropwise onto a 25 mm polycarbonate (PC) substrate disk exhibiting a thickness of 24 ± 1 μm and a porosity of 4.7% provided by 100 nm track-etch pores (Nuclepore Track-Etch Membrane, 25 mm, 0.1 μm) disposed on top of a Buchner funnel (one end was sealed, the other end was connected to a vacuum pump).

[0203] The surface charge of the PC film was measured using the conductance equation [1] and was found to be approximately 0.2 mC / m 2 It was determined that.

[0204] The pore size of the 2D lamellar graphene oxide (GO) membranes was measured using X-ray diffraction performed on an Xpert Pro instrument (Philips Pana Analytical, Cu Kα; λ = 1.5418 Å, operating at 40 kV and 20 mA) and determined to be 0.8 nanometers on average. The XRD diffractogram revealed a wide distribution of interlayer distances (0.7 nm to 1.4 nm).

[0205] The second side 30B of the asymmetric membrane element 30 has an average pore size that is 250 times smaller than that of the first side 30A.

[0206] Material characterization The surface morphology of the composite films was observed by optical microscopy in transmission mode and by field-emission scanning electron microscopy (FE-SEM) on a Thermo-Fischer™ Quattro S instrument. Cross-sections of the 2D nanolaminate layers were observed after tilting the sample holder by 90°. X-ray diffractograms of the films were collected in refraction mode by using a powder XRD diffractometer (Bruker®). The average spacing between the GO layers of the GO / PC films was determined by applying Bragg's law to the 001 peak of the recorded diffractograms.

[0207] Example 2 Preparation and characterization of alternative composite membranes Composite films were fabricated according to Example 1 using 2D nanolaminates made from MoS2.

[0208] The MoS2 suspension was obtained by chemical exfoliation of MoS2 bulk crystals as previously reported, with further sonication and centrifugation steps as described in [7].

[0209] Example 3 Cells and electrodes The VIRO cell consists of two vessels 10A and 10B (feed water and fresh water) separated by a composite membrane 30. Capacitive electrodes 20A and 20B are positioned within each vessel 10A and 10B, allowing the application of an AC electric field to generate EO flow. To maximize this flow, the electrodes 20A and 20B are compressed against the membrane 30. This reduces the distance between the electrodes, leading to a higher AC electric field strength. The use of capacitive electrodes avoids the generation of large faradaic currents and thus limits the presence of electrochemical reactions that could interfere with the transport mechanism through the membrane. A 100 μm-thick, highly porous polymer felt acts as a separator 60 between the electrode 20B and the second side 30B of the membrane, preventing direct electrical contact between them.

[0210] The cells were fabricated by an additive manufacturing process (SLA) using a 3D printer (Formlabs, Form 3, 50 mL of Formlab resin). Once the cells were assembled and closed, each vessel was connected to its reservoir by a fluidic connection and valve system.

[0211] The capacitive electrodes used are activated carbon electrodes (Kynol GmbH).

[0212] Example 4 Trace contaminant filtration To investigate the molecular sieving properties of our nanocomposite membranes, their performance in terms of nanocontamination removal and desalination was evaluated under VIRO experiments. The removal rates under the EO process were measured for several typical trace pollutants (for which purification solutions are scarce and expensive): organic dye (rhodamine B), acetaminophen (paracetamol), caffeine, and testosterone. Filtration of nanocontaminants was achieved according to the following steps: i) a 30 mL volume V1 of a first electrolyte solution containing nanopollutants at a concentration of 10 mM in water is brought into contact with a first porous electrode according to Example 3; ii) contacting a second volume V2 of 10 mL of a second electrolyte solution comprising pure water with a second porous electrode according to Example 3; iii) Applying an AC electric field of 10 V at 10 Hz between the first electrode 20A and the second electrode 20B, resulting in solvent transport and solute filtration through the membrane element according to Example 1, the variation in volume V2 (V2(nT)) was 1.10 for n=9000 and T=0.1 (s). -5 m 3 is; iv) Gas bubbles generated during the parasitic electrochemical reactions are automatically drained by gravity due to the optimized cell geometry (Venturi effect).

[0213] Analysis of water for trace contaminant filtration is carried out by absorbance analysis (Thermo scientific, Nanodrop) using light transmission analysis of a droplet from the sample (1 μL).

[0214] The concentration of NaCl in both 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).

[0215] Results and Discussion Tests demonstrated the filtration of a 10 mL volume of water containing trace pollutant model molecules at a 10 mM feed concentration. Nanofiltration experiments resulted in greater than 99.9% removal of all trace pollutants and for both the GO+PC and GO+MoS2 asymmetric membranes (Figure 8). Up to 10 L.hm for the GO+PC and GO+MoS2 asymmetric membranes, respectively, was achieved. 2 and 80 L.hm. 2 Such tests allowed filtration within 150 and 15 minutes, respectively.

[0216] The asymmetry in EO transport demonstrates that applying an AC voltage has the primary advantage of avoiding effects due to charge polarization or electrode saturation. However, this technique cannot be applied to symmetric membranes, since the average water flux over the cycle is zero. On the other hand, nanocomposite membranes that display highly asymmetric transport exhibit a non-zero average water flux over the cycle, which leads to net mass transport from one side of the membrane to the other.

[0217] Example 5 Comparison of fluxes obtained using pure electroosmotic filtration and pressure-assisted electroosmotic filtration Example 4 was reproduced without and with some additional mechanical pressure, with the following modifications: i) a 10 mL volume V1 of a first electrolyte solution comprising a sodium chloride solution at a concentration of 10 mM in water is brought into contact with the first porous electrode according to Example 3; ii) a second volume V2 of 10 mL of a second electrolyte solution comprising a sodium chloride solution at a concentration of 10 mM in water is brought into contact with the second porous electrode according to Example 3; The first vessel was adapted with the addition of two valves and tubing connected to the side and top openings of the vessel. Both tubings were connected to a pressurized tank containing the first electrolyte. The combination of the first vessel, valve, two tubings, and pressure tank was interconnected and pressure sealed, allowing the first electrolyte to circulate therethrough at a controlled pressure. The pressurized tank was connected to a pressure generator that delivered a pressure ranging from 0 bar to 1 bar. iii) applying an AC electric field of 2.5 Hz at a voltage difference comprised between 1 V and 5 V between the first electrode 20A and the second electrode 20B resulted in solvent transport through the membrane element according to Example 1; iv) Gas bubbles generated during the parasitic electrochemical reactions are automatically drained by gravity due to the optimized cell geometry (Venturi effect).

[0218] Experiments performed without and with external mechanical pressure (pressure-assisted electroosmotic filtration, step v) showed a resulting electroosmotic flux (Q ) of 0.105 mL / min at a voltage amplitude of 5 V. EO ) without pressure (dP = 0 bar). When a pressure of 750 mbar was added under the same voltage and frequency conditions, a higher total flux (Q) of 1.15 mL / min was obtained. tot =Q EO +Q pressure ) were measured, thus confirming the possible combination of both electroosmotically and pressure-driven reverse osmosis fluxes. One advantage of such a combination could be the use of reverse electroosmotic filtration to reduce the operating mechanical pressure of the reverse osmosis filtration process.

[0219] References 1.Becker N, Lavee D, Katz D.Desalination and Alternative Water-Shortage Mitigation Options in Israel:A Comparative Cost Analysis.JWARP.2010;02(12):1042-56 2.Spiritos E, Lipchin C.Desalination in Israel.In:Becker N,▲e▼diteur.Water Policy in Israel [Internet].Dordrecht:Springer Netherlands;2013[cit▲e▼ 7 mars 2022].p.101-23.(Global Issues in Water Policy;vol.4).Disponible sur: http: / / link.springer.com / 10.1007 / 978-94-007-5911-4_7 3.Wang L,Dykstra JE,Lin S.Energy Efficiency of Capacitive Deionization.Environ Sci Technol.2 avr 2019;53(7):3366-78. 4.Oren Y.Capacitive deionization(CDI)for desalination and water treatment-past,present and future(a review).Desalination.ao▲u▼t 2008;228(1-3):10-29. 5.Al-Amshawee S,Yunus MYBM,Azoddein AAM,Hassell DG,Dakhil IH,Hasan HA.Electrodialysis desalination for water and wastewater:A review.Chemical Engineering Journal.janv 2020;380:122231. 6.Koros WJ,Zhang C.Materials for next-generation molecularly selective synthetic membranes.Nature Mater.mars 2017;16(3):289-97. 7.Ries L,Petit E,Michel T,Diogo CC,Gervais C,Salameh C,et al.Enhanced sieving from exfoliated MoS2 membranes via covalent functionalization.Nat Mater.oct 2019;18(10):1112-7. 8.Joshi RK,Alwarappan S,Yoshimura M,Sahajwalla V,Nishina Y.Graphene oxide:the new membrane material.Applied Materials Today.nov 2015;1(1):1-12. 9.Progress on free-standing and flow-through TiO2 nanotubes membranes,Guohua Lin,Kaiying Wang,Nils Hoivik,Henrik Jakobsen,Solar Energy Materials & Solar Cells,98,2012,pp 24-38;TiO2 nanotubes synthesis and applications,Poulomi Roy,Steffen Berger,Patrick Schmuki,Angewandte Chemistry Int.Ed,50,2011,pp 2904-2939. 10.Jung Tae Park, Won Seok Chi, Sang Jin Kim, Daeyeon Lee & Jong Hak Kim, Scientific Reports 4:5505,Nature,2014. 11.Song J.et al.,Preparation and Characterization of Graphene Oxide;Journal of Nanomaterials,276143,2014 [Explanation of symbols]

[0220] 10A First Vessel 10B Second Vessel 11A First Electrolyte Solution 11B Second Electrolyte Solution 20A First Electrode 20B Second electrode 30 Asymmetric Membrane Element 30A Semipermeable Sub-Membrane Element, First Side 30B Charged Sub-Membrane Element, Second Side 40 Sources of Electrical Energy 40A First Vessel 40B Second Vessel 60 Separator 70A current collector 70B current collector 80A Rubber Flat Seal 80B Rubber Solid Seal 401 Wall 402 Outlet Pipe 402A Pipe Sub-Vessel 402B Hyperbolic Sub-Vessel w Pipe diameter y Larger opening of hyperbolic sub-vessel x Narrow opening of hyperbolic sub-vessel z Hyperbolic sub-vessel height

Claims

1. Steps below: i) contacting a first volume V1 of a first electrolyte solution (11A) containing 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 a second porous electrode (20B); iii) applying an AC electric field between the first electrode (20A) and the second electrode (20B), resulting in solvent transport and solute filtration through the membrane element (30), wherein the variation in volume V2 is defined by the following formula (Formula I): V ２ (nT) = μ ＥＯｅｆｆ DV ｅｆｆ rr ２ ntat －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 ) and 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) evacuating the gas bubbles generated during the parasitic electrochemical reaction; 1. A process for purifying an electrolyte solution, comprising: 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 second side (30B) of the asymmetric membrane element (30) has an average pore size that is 1.1 to 10,000 times smaller than that of the first side (30A); a separator (60) 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 geometric, physicochemical, environmental, or a combination thereof; The process wherein the first electrode (20A) and the second electrode (20B) are operably connected to a source of electrical power (40) via two current collectors (70A, 70B).

2. The process of claim 1 , wherein the process is performed in a static or tangential mode.

3. 3. The process of claim 1 or 2, wherein the process further comprises a step v) of pressure-induced reverse osmosis.

4. 4. The process according to claim 1, wherein the temperatures of the first electrolyte solution (11A) and the second electrolyte solution (11B) differ by more than 1°C.

5. 5. The process of any one of claims 1 to 4, wherein the asymmetric membrane element (30) comprises a composite material having different properties of each element of the composite, an assembly of two materials of the same nature having at least one inherent property that differs, or a single material having at least one inherent property that differs from one side to the other.

6. 6. The process of any one of claims 1 to 5, wherein the first side (30A) comprises a semi-permeable sub-membrane and the second side (30B) comprises a charged sub-membrane.

7. 7. The process of claim 6, wherein the second side (30B) of the asymmetric membrane element (30) is in contact with the second electrolyte solution 11B, which comprises a solvent.

8. 5. The process of claim 4, wherein the second side (30B) of the asymmetric membrane element (30) is in contact with the first electrolyte solution 11A, which includes a solvent.

9. 7. The process of any one of claims 4 to 6, wherein the semipermeable sub-membrane (30A) comprises a steric exclusion membrane, an electrostatic exclusion membrane, or a membrane capable of separating / filtering specific solid molecules or ions from a given electrolyte solution.

10. 10. The process of any one of claims 1 to 9, 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 a membrane.

11. 11. The process of any one of claims 1 to 10, wherein the separator 60 is organic, inorganic, or an insulating composite.

12. The current collectors (70A, 70B) are made of 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－ 12. The process of claim 1, wherein the conductive material is independently selected from the group consisting of fluororesin, fluororesin, fluoroisotope ...

13. 13. The process of any one of claims 1 to 12, wherein the source of electrical energy (40) is generated by a device that delivers only a DC voltage and is coupled to a DC / AC converter, or by a device that delivers an AC electrical signal.

14. 14. The process according to any one of claims 1 to 13, 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. 15. The process of any one of claims 1 to 14, wherein the solvent of the first electrolytic solution (11A) and the solvent of the second electrolytic 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, or mixtures thereof.

16. a first vessel (40A) containing a first volume V1 for a first electrolytic solution (11A) containing a solute and a solvent; a second vessel (40B) containing a second volume V2 for a second electrolyte solution (11B) containing a solvent; a first electrode (20A) adapted to be in contact with said first electrolyte solution (11A); a second electrode (20B) adapted to be in contact with said second electrolyte solution (11B); an asymmetric membrane element (30) comprising a first side (30A) and a second side (30B); a separator (60) positioned between the electrode (20A or 20B) and the second side (30B) of the asymmetric membrane element (30); two current collectors (70A, 70B) operatively connecting said first and second electrodes (20A, 20B) to a power supply (40) configured to apply an alternating electric field between said first and second electrodes; 1. A system for purifying an electrolyte solution, comprising: - said first vessel (40A) and said second vessel (40B) are configured to expel gas bubbles generated during the parasitic electrochemical reaction by the Venturi effect; the first and second electrodes (20A, 20B) are porous electrodes, grid electrodes or any geometric shape through which the electrolyte can diffuse; the asymmetric membrane element (30) has an asymmetry of geometric, physicochemical, environmental nature, or a combination thereof, between the first side and the second side of the membrane element (30); - the second side (30B) of the asymmetric membrane element (30) has an average pore size that is 1.1 to 10,000 times smaller than that of the first side (30A).

17. 17. The system of claim 16, wherein the first and second electrodes are compressed against the membrane element (30).

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

19. 18. The system of claim 15, 16, or 17, wherein the first and second vessels (40A, 40B) are coupled to a pressure generator and process pressure-assisted AC voltage-induced reverse osmosis.

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