Reverse electroosmosis filtration system and uses thereof

Abstract

The present invention relates to a purification / filtration system that uses reverse electroosmosis flow through composite or hybrid membrane elements. The present invention also relates to a process for purifying electrolyte solutions using such a system. The present invention further relates to a water purification system, a saline desalination system, and an implantable artificial kidney that include a reverse electroosmosis filtration system according to the present invention.

Description

[Technical Field]

[0001] (Priority) This PCT application claims priority to European Patent Application Publication No. 20305110.7, filed February 6, 2020, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present invention relates to a purification / filtration system that uses reverse electroosmotic flow through composite or hybrid membrane elements. The present invention also relates to a process for purifying electrolyte solutions using such a system. [Background technology]

[0003] Due to population growth and improvements in quality of life, ensuring clean water has become a central issue worldwide. Drinking water is becoming contaminated with a wide variety of contaminants, ranging from particles to small molecules such as colorants, pesticides, drugs, and hormones, due to various sources. In fact, hormones, spread in water by primary industries, are currently one of the most common contaminants and are one of the most difficult to remove. Although these molecules are present in very small amounts, usually below standard detection limits, they pose a risk to the environment and human health. For example, planned pregnancy releases estradiol and other hormones associated with reduced sperm quality into potentially potable water. These hormones, present in agriculture, precision industries, or directly excreted by humans, are further absorbed into soil, plants, and animals. More than 70% of human breast cancers are estrogen-dependent, and their development and proliferation should be considered as influenced not only by endogenous estrogens but also possibly by estrogenic endocrine disruptors in the environment. Osmotic purification is a well-known water purification method. Osmotic pressure is a natural phenomenon based on the following principle: when two aqueous solutions with different concentrations of impurities such as salts are separated by a semipermeable membrane that is permeable to water and impermeable to impurities such as salts, pure water will move from the solution with the lower concentration to the solution with the higher concentration.

[0004] Specifically, the semipermeable membrane prevents the passage of salts dissolved in the water, so the movement of pure water is the only means by which concentration balance can be established on both sides of the membrane.

[0005] The direct result of pure water moving into the compartment containing the more concentrated solution is an increase in solution pressure across the membrane. This pressure is called the osmotic pressure (P osm ) is called.

[0006] There are two types of water treatment technologies that utilize the properties of semipermeable membranes and the osmosis phenomenon: one is the so-called reverse osmosis method, and the other is the so-called direct (forward) osmosis method.

[0007] Currently, the most developed technology is reverse osmosis, which involves applying a pressure much higher than the osmotic pressure to a highly concentrated solution, reversing the flow of water molecules through a semipermeable membrane.

[0008] This reverse osmosis method allows for the production of highly pure water, but the osmotic pressure P osm Reverse osmosis is a technology that requires much higher pressures and very high energy consumption to implement. For example, water desalination by reverse osmosis is a known technology in the field of water treatment. However, reverse osmosis desalination involves the artificial application of relatively high pressures and therefore necessarily involves very high energy consumption. As a result, the investment and operating costs of reverse osmosis facilities are high.

[0009] Furthermore, these processes are generally well suited to the removal of contaminants, especially those targeted within the nanosize range. In some cases, it is possible to obtain a high water flow rate with low selectivity (low removal rate). The low concentration and small size of hormone molecules not only hinders their detection by routine analytical methods, for example in the determination of pollutants in water, but also hinders the removal of such small organic molecules by common purification methods.

[0010] Current commercial seawater reverse osmosis (SWRO) desalination can achieve up to 50% recovery of desalinated water, resulting in a rejected stream with a salinity of 7% and an associated osmotic pressure of 784 psi. Actual desalination operating pressures must be taken into account, as required pump pressures can exceed 1000 psi due to inefficiencies in pumping equipment and control systems.

[0011] Most semipermeable polymer membranes suitable for desalination of seawater cannot sustain operation or separation efficiency at pressures above 1,100 psi and suffer more or less failure, so the desalination process must be operated at low rejection rates, i.e., 40% or less, to maintain membrane life.

[0012] Although processes and systems already known in the art aim to increase energy efficiency, a major drawback is that they still require relatively high energy consumption.

[0013] Thus, there exists a great need for further improvements in reverse osmosis water purification systems. The present invention fulfills these needs and provides further related advantages. [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows a schematic diagram of an exemplary system according to the present invention with a composite reverse osmosis membrane element (30). [Figure 2] 1 shows a schematic diagram of an exemplary system according to the present invention with a hybrid reverse osmosis membrane element (30). [Figure 3] 1 shows a schematic diagram of an exemplary system according to the present invention involving a composite reverse osmosis membrane element (30) and a porous support (33). [Figure 4A] 1 illustrates exemplary features of a system according to the present invention. 2 illustrates a schematic diagram of an exemplary filtration system / experimental setup according to the present invention. [Figure 4B] 1 illustrates exemplary features of a system according to the present invention;FIG. 2 illustrates a schematic representation of a molecular filtration process in an exemplary filtration system according to the present invention;FIG. [Figure 4C] 1 shows exemplary features of a system according to the present invention: a representative FE-SEM image of the GO surface of a GO / PC composite reverse osmosis membrane element according to the present invention (left) and a 90° cross-section of the highly stacked GO (right), showing a thickness of 8.66 μm of self-supported GO. [Figure 4D] 1 shows an exemplary feature of a system according to the present invention: X-ray diffractogram of a GO / PC composite reverse osmosis membrane element according to the present invention, in which the first peak is associated with the interlayer planes of GO in the range of 0.7-1.4 nm, and the second peak correlates with the presence of PC in the composite membrane. [Figure 5A] Figure 1 shows exemplary results using a system according to the invention (GO / PC composite membrane): Development of saturation voltage over time in each chamber of the cell in the presence of 100 mM KCl (equilibration time was considered to be 2 hours). [Figure 5B] 1 shows exemplary results using a system according to the present invention (GO / PC composite membrane): Electroosmotic flux versus salt concentration and strength. [Figure 5C] 1 shows exemplary results using a system according to the present invention (GO / PC composite membrane): Strength vs. electroosmotic flux. [Figure 5D] 1 shows exemplary results using a system according to the present invention (GO / PC composite membrane): Current vs. intensity. [Figure 5E] An exemplary result using the system according to the present invention (GO / PC composite membrane) is shown. The voltage measured as a function of the applied ionic current. The asymmetric response is due to the charge asymmetry across the GO / PC composite membrane. This measurement demonstrates that the membrane is composed of two materials with different characteristics. [Figure 5F] Exemplary results using the system according to the invention (GO / PC composite membrane): constant applied intensity values ​​ranging from -1 to 1 mA, voltage obtained after voltage equilibrium was achieved; (inset) various electroosmotic flows generated by the device for varying salt concentrations (1 mM, 10 mM, 30 mM, and 100 mM) in both vessels, showing that the flow rate increases with decreasing salt concentration and increasing applied intensity. [Figure 6A]1 shows exemplary removal results using a system according to the present invention (GO / PC composite membrane). First removal results. [Figure 6B] 1 shows exemplary removal results using the system according to the present invention (GO / PC composite membrane). 2nd optimized dye. [Figure 6C] Figure 1 shows exemplary removal results using a system according to the invention (GO / PC composite membrane): Hormone removal: UV-visible spectrum of testosterone present in the vessel supplied for filtration ("Test Initial") compared with the absorption spectrum obtained after filtration during the elution phase ("Test Elution"). [Figure 6D] Figure 1 shows exemplary removal results using a system according to the present invention (GO / PC composite membrane): Range of complete removal rates under operating electroosmotic conditions (1 mM KCl, 0.5 mA) for the molecule used as a model (Rubypy). [Figure 7] Simulation method: Calculation of water flow across an asymmetric membrane under voltage drop (AV) in an exemplary system according to the invention: Q=water flow through the membrane, Qosm=osmotic flow of water through the membrane at ΔV=0. [Figure 8] Optical microscope image of the surface of the GO / PC composite film according to the present invention (no cracks detected at long distances). [Figure 9] BET surface area (analysis of the average pore size of the GO membrane element of the GO / PC composite reverse osmosis membrane according to the present invention, in the absence of the PC substrate). [Figure 10] Pore ​​size distribution of the GO membrane element of the GO / PC composite reverse osmosis membrane according to the present invention, showing a wide distribution from 1.8 nm to 6 nm. [Figure 11] Nitrogen adsorption BET isotherm of the GO membrane element of the GO / PC composite reverse osmosis membrane according to the present invention. [Figure 12] Photograph of an exemplary embodiment of a filtration system according to the present invention. [Figure 13] Electroosmotic flow rate versus concentration and voltage using bare PC membranes (PC-only membranes) as vessel separators and KCl electrolyte solutions of different concentrations. [Figure 14] Calibration curve: Ru(biPy) concentration versus absorbance at 283 nm. [Figure 15]Comparative electroosmotic fluxes determined at a relatively low concentration (1 mM KCl) and different strength values ​​tested by using a PC-only membrane (open circles) or a GO / PC composite membrane according to the present invention (filled circles) as the container separator. The modulation of flow versus current in the composite membrane indicates the charge asymmetry of the membrane.

[0015] While the systems and processes of the present application are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit application to the particular embodiments disclosed, but rather the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the processes of the present application as defined by the appended claims.

[0016] 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 used herein and the laboratory procedures described below are those well known and commonly employed in the art.

[0017] To facilitate understanding of this disclosure, several terms and phrases are defined below.

[0018] When used outside the claims, the words "a," "an," "the," and / or "the" mean one or more. When used in the claims, the words "comprise," "comprises," and / or "comprising" When used in connection with, the words "a," "an," "the," and / or "said" may mean one or more than one. As used in this specification and claims, "having," "has," "is," "have," The terms "including," "includes," and / or "include" may be used interchangeably with "comprising," "comprises," and "comprise." As used in the specification and claims, "another" may mean at least a second or more. As used in the specification and claims, "about" refers to any inherent measurement error or rounding of numbers for values ​​(e.g., measurements, calculations such as ratios), and thus the term "about" may be used in conjunction with any value and / or range.

[0019] The phrase "combinations thereof," as well as mixtures thereof, and similar phrases 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 "for example," and / or a list in parentheses with "for example" or i.e., refers to any combination (e.g., any subset) of the listed series of elements; combinations, mixtures of related species, and / or embodiments described herein, although not directly located in such list, are also contemplated. Such related and / or similar genera, subgenera, species, and / or embodiments described herein are contemplated both in the form of individual elements that may be claimed, and mixtures and / or combinations that may be described in the claims as "at least one selected from," "mixtures thereof," and / or "combinations thereof."

[0020] 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 it is associated.

[0021] As will be understood by those of ordinary skill in the art, all numbers, including those expressing quantities of ingredients, properties such as cavity / pore size and zeta potential, experimental conditions, and the like, are understood to be approximate and, optionally, modified in all instances by the term "about." These values ​​may vary depending on the desired properties sought to be obtained by one of ordinary skill in the art utilizing the teachings set forth herein. It is also understood that such values ​​inherently contain variations necessarily resulting from the standard deviation found in their respective testing measurements.

[0022] As used herein, the term "about" may refer to a ±5% variation of the specified value. For example, "about 50" percent may, in some embodiments, include a variation of 45 to 55 percent. For integer ranges, the term "about" may include integers one or two greater and / or less than the recited integer. Unless otherwise indicated herein, the term "about" is intended to include values, e.g., concentration values, that are close to the recited range and are equivalent with respect to the functionality of the individual component, composition, or embodiment.

[0023] As will be understood by those skilled in the art, for any and all purposes, particularly with respect to providing a written description, all ranges recited herein also encompass any and all possible subranges and combinations of those subranges, as well as the individual values, particularly integer values, that make up the ranges. A recited range includes each specific value, integer, decimal point, or identity within that range. Any recited range is fully described and encompasses at least one of the same range. It can be readily recognized that any range can be broken down into equal parts, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third, upper third, etc. DETAILED DESCRIPTION OF THE INVENTION

[0024] Illustrative embodiments are described below. For clarity, not all features of an actual implementation are described herein. It will, of course, be understood that in the development of any such actual implementation, implementation-specific decisions will need to be made to achieve the developer's particular goals, including compliance with system- and business-related constraints that vary from implementation to implementation. It will further be understood that such a development effort might be complex and time-consuming, but would nevertheless be routine for those of ordinary skill in the art having the benefit of this disclosure.

[0025] Reference may be made herein to spatial relationships between various components, and the spatial orientation of various aspects of components, as the devices are depicted in the accompanying drawings. However, as will be recognized by those skilled in the art after fully reading this application, the devices, members, instruments, etc. described herein may be positioned in any desired orientation. Thus, the use of terms to describe spatial relationships between various components, or the spatial orientation of aspects of such components, should be understood to describe the relative relationships between the components or the spatial orientation of aspects of such components, as the devices described herein may be oriented in any desired direction.

[0026] The present system and process overcome one or more of the above-mentioned problems commonly associated with conventional membrane technologies and processes. Specifically, the present system uses a reverse electro-osmosis filtration system. These unique features of the present system are discussed below and illustrated in the accompanying drawings.

[0027] The system and process, both its structure and operation, will be understood from the accompanying drawings in conjunction with the accompanying description. Several embodiments of this system are presented herein in Figures 1-15. It should be understood that various components, parts, and features of different embodiments can be combined with and / or substituted for one another, and that all variations and specific embodiments are within the scope of the present application, even if they are not shown in the drawings. Furthermore, mixing and matching of features, elements, and / or functions between various embodiments is expressly contemplated herein, and those skilled in the art should understand from this disclosure that features, elements, and / or functions of one embodiment can be incorporated into other embodiments as appropriate, unless otherwise noted.

[0028] In one aspect, the present invention provides a reverse electroosmosis filtration system, the system comprising: a) a first container (10A) intended to receive an electrolyte solution (11A) enriched in a solute of interest, the first container comprising a first electrode (20A) in contact with the electrolyte solution (11A) contained in the container (10A); b) a second container (10B) intended to receive an electrolyte solution (11B) substantially free or depleted of the same solute of interest, the second container comprising a second electrode (20B) in contact with the electrolyte solution (11B) contained in the container (10B); c) a reverse osmosis membrane element (30) separating the two vessels, (i) a semi-permeable membrane element (31), and (ii) a nanoporous membrane element (32) with a surface charge of which |Zeta potential| is ≧5 mV, preferably >20 mV, most preferably ≧50 mV, wherein the semipermeable membrane element (31) and the nanoporous membrane element (32) with a surface charge can be one and the same element or two different elements, The semi-permeable membrane element (31) is configured to contact the electrolyte solution (11A) in the first container (10A), and the nano-porous membrane element (32) having a surface charge is configured to contact the electrolyte solution (11A) in the second container (10A). and a reverse osmosis membrane element (30) configured to contact the electrolyte solution (11B) of the container (10A) with the electrolyte solution (11A), the reverse osmosis membrane element (30) fulfilling both the functions of (i) solute filtration and (ii) electrically conducting a solvent flow of the electrolyte solution (11A) from the container (10A) to the container (10B) through the reverse osmosis membrane element (30); the electrolyte solutions (11A) and (11B) in the containers (10A) and (10B), respectively, contain the same polar solvent; the first and second electrodes (20A) and (20B) are operably coupled to a source of electrical energy (40); Application of an electric field between the first electrode (20A) and the second electrode (20B) induces reverse osmosis flow of the polar solvent of the electrolyte solution (11A) from the vessel (10A) to the vessel (10B) through the reverse osmosis membrane element (30).

[0029] The filtration system according to the present invention may be a purification system.

[0030] In another aspect, the present invention provides a process for purifying an electrolyte solution in a polar solvent, the process comprising: i) providing an electrolyte solution (11A) containing undesired solutes in a polar solvent; and ii) providing a second electrolyte solution (11B) free of undesired solutes in the same or a different polar solvent as in step i); iii) providing a reverse electroosmosis filtration system, the system comprising: a) a first container (10A) equipped with a first electrode (20A); b) a second vessel (10B) having a second electrode (20B), the first and second electrodes (20A) and (20B) being operably connected to a source of electrical energy (40); c) a reverse osmosis membrane element (30) separating the two vessels (10A) and (10B), (i) a semi-permeable membrane element (31), and (ii) a nanoporous membrane element (32) with a surface charge of which |Zeta potential| is ≧5 mV, preferably ≧20 mV, most preferably ≧50 mV, wherein the semipermeable membrane element (31) and the nanoporous membrane element (32) with a surface charge can be one and the same element or two different elements; a reverse osmosis membrane element, wherein the semi-permeable membrane element (31) is in contact with the electrolyte solution (11A) in the container (10A), and the nanoporous membrane element (32) having a surface charge is in contact with the electrolyte solution (11B) in the container (10B); the reverse osmosis membrane element (30) fulfills both the functions of (i) solute filtration and (ii) electrically conducting the solvent flow of the electrolyte solution (11A) from the container (10A) to the container (10B) through the reverse osmosis membrane element (30); the reverse osmosis membrane element (30) is adapted to selectively block the diffusion of undesired solutes through the reverse osmosis membrane element (30); iv) placing the electrolyte solution (11A) to be prepared in the container (10A) so that the first electrode (20A) provided therein is in contact with the electrolyte solution (11A); v) placing a sufficient amount of second electrolyte solution (11B) in the container (10B) so that the second electrode (20B) provided therein is in contact with the electrolyte solution (11B); vi) applying an electric field between the first electrode (20A) and the second electrode (20B) to induce a reverse osmosis flow of the polar solvent from the vessel (10A) to the vessel (10B) through the reverse osmosis membrane element (30) separating the two vessels (10A) and (10B), thereby allowing the solvent to flow from the container (10A) towards the container (10B) while retaining the undesired solutes within the container (10A); vii) recovering the purified electrolyte solution (11B) from the vessel (10B) substantially free of or depleted of undesired solutes.

[0031] Throughout this disclosure, the first and second electrodes (20A) and (20B) are operably coupled to an electrical energy source (40) such that an electric field is or can be applied between the first electrode (20A) and the second electrode (20B) (e.g., the electrical energy source (40) enables the application of an electric field between the first electrode (20A) and the second electrode (20B)).

[0032] As used herein, the term "solute" refers to a liquid or solid material that dissolves in the polar solvent used in the electrolyte solution (11A) and / or (11B).

[0033] As used herein, the term "substantially free of solutes" means that ≥99%, preferably ≥99.5%, more preferably ≥99.8%, even more preferably >99.9%, and most preferably 100% of the solutes have been removed (meaning that ≥99.0%, more preferably ≥99.5%, even more preferably ≥99.8%, even more preferably ≥99.9%, and most preferably 100% or about 100% solute removal is achieved). In other words, the reverse osmosis membrane element (30) separating the two vessels (10A) and (10B) allows <1.0%, more preferably <0.5%, even more preferably <0.2%, even more preferably <0.1%, and most preferably 0% of the undesired solutes to pass through the reverse osmosis membrane.

[0034] As used herein, the term "solute-enriched" means that the supplied electrolyte solution (11A) contains a higher concentration of solute than the eluted electrolyte solution (11B).

[0035] As used herein, the term "solute-depleted" means that the eluted (second) electrolyte solution (11B) contains a lower concentration of solute than the supplied (first) electrolyte solution (11A).

[0036] As used herein, the term "semipermeable membrane" refers to a membrane that allows the passage of specific molecules or ions by diffusion or artificially created flux, without departing from the conventional meaning of the term 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 (e.g., a semipermeable membrane based on separation by chemical affinity).

[0037] As used herein, the term "electrolyte solution" refers to a conductive solution containing mobile ions that induce electroosmosis.

[0038] As used herein, the term "nanoporous membrane" does not deviate from the conventional meaning of the term in the field of filtration membranes and refers to a membrane with an average pore size <1 μm, preferably ≦500 nm.

[0039] As used herein, when referring to a membrane surface charge, "zeta potential" does not deviate from the conventional meaning of the electrochemical term and refers to the potential difference between the membrane surface and a fixed layer of fluid attached to the membrane surface. Zeta potential typically depends on the nature of the membrane surface and the properties of the electrolyte solution in contact with the membrane surface (e.g., pH, ion concentration, ionic force, etc.). Zeta potential can be calculated using the Smoluchowski equation (see Equation 1 below).

[0040] As used herein, |Zeta potential| refers to the absolute value of the zeta potential (i.e., the numerical value of the zeta potential regardless of sign). As can be readily understood from this disclosure, the present invention provides This can be done using nanoporous membrane elements with negative or positive surface charges, and the zeta potential can be negative or positive, respectively, when the membrane is in contact with the electrolyte solution.

[0041] As used herein, the term "polar solvent" does not deviate from its conventional meaning and common knowledge / usage in the field. Generally, polar solvents include, but are not limited to, aprotic solvents with a dielectric constant of ≧6 and a dipole moment of ≧1.50 D, and protic solvents such as water, alcohols, formic acid, acetic acid, hydrogen fluoride, and ammonia.

[0042] The underlying phenomenon behind the present invention is based on the reverse electro-osmotic effect, which excludes other diffusion phenomena such as electrophoresis and diffusio-osmotic effects.

[0043] The reverse osmosis membrane element (30) may be a composite membrane element or a hybrid membrane element.

[0044] The permeate, from which the rejected solutes have been removed, exits the reverse osmosis membrane element (30) as permeate stream (50), which may be collected in vessel (10B). Accordingly, the present invention also relates to a method for separating solvent and solutes from a solute-containing electrolyte solution using a filtration system or purification process according to the present invention.

[0045] 1.Composite membrane An exemplary embodiment is shown in FIG.

[0046] In a variant, the reverse osmosis membrane element (30) may be a composite membrane element, and the reverse electroosmosis filtration system according to the present invention comprises a semipermeable membrane element (31) and a nanoporous membrane element (32) having a surface charge, which are two distinct elements combined together to form a two-layer composite asymmetric membrane (30A). The composite asymmetric membrane (30A) may comprise a semipermeable membrane (31) superimposed with a charged nanoporous membrane (32). Advantageously, the composite asymmetric membrane (30A) may comprise a semipermeable membrane (31) superimposed with a charged nanoporous membrane (32) having a surface charge with a |zeta potential| of ≧5 mV, preferably ≧20 mV, and most preferably ≧50 mV.

[0047] As discussed below, the semipermeable membrane element itself may combine a semipermeable membrane with a porous support layer.

[0048] 1.1. Semipermeable membrane The semipermeable membrane usable in the context of the present invention may be any semipermeable membrane known in the art. For example, the semipermeable membrane element (31) may be a size-exclusion membrane, an ion-exchange membrane, or any other membrane capable of separating / filtering specific molecules or ions from a given electrolyte solution (e.g., a semipermeable membrane based on chemical affinity separation), and is preferably a size-exclusion membrane or an ion-exchange membrane. For example, it may be a semipermeable membrane that separates pure water molecules from salts and other impurities, or 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. Thus, it may be a semipermeable membrane conventionally used in water purification technology, where semipermeable membranes are used to remove ions, molecules, and larger particles from contaminated water. It may also be a semipermeable membrane for use in water purification or desalination systems, reverse osmosis systems, such as a thin film composite membrane (TFC or TFM).

[0049] Membranes used in reverse osmosis are generally made from polyamides selected primarily for their permeability to water and their relative impermeability to various dissolved impurities, including salt ions and other small molecules that cannot be filtered. In yet another example, the semipermeable membrane element (31) can be an anion exchange membrane (AEM) or a cation exchange membrane (CEM). For example, the semipermeable membrane element (31) can be a Nation semipermeable membrane.

[0050] The mean pore size of the semipermeable membrane is adapted to filter the target solute from the electrolyte solution (11A). Therefore, the mean pore size of the membrane is sufficiently small to prevent the target solute (and any other solutes with a particle size larger than the target solute) from passing through the semipermeable membrane (31), while allowing polar solvents and other smaller solutes to pass through the semipermeable membrane (31). The mean pore size of the semipermeable membrane is adapted depending on the intended type of application: microfiltration (50-500 nm), ultrafiltration (1-50 nm), or nanofiltration (≦1 nm). Advantageously, the semipermeable membrane element (31) may have a mean 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 intended for ultrafiltration, and the semipermeable membrane element (31) may have a mean pore size of 1-50 nm. In another preferred variant, the filtration system is intended for nanofiltration, and the semipermeable membrane element (31) may have an average pore size of <1 nm. Such a nanofiltration system may be useful, for example, for desalination.

[0051] Advantageously, the semipermeable membrane can be a nanoporous carbon membrane. Nanoporous carbon membranes include carbon nanotube membranes, nanoporous graphene membranes, and multilayer graphene oxide membranes. All of these materials exhibit similar properties of selective permeability and can be used as molecular sieves in applications involving membrane separation, such as nanofiltration and desalination. Carbon nanotube membranes 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 fabricated 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.

[0052] 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.

[0053] Thus, in the context of the present invention, the semipermeable membrane may be a carbon nanotube membrane, a nanoporous graphene membrane, or a multilayer GO or rGO membrane, preferably a multilayer GO or rGO membrane, most preferably a multilayer GO membrane.

[0054] Advantageously, the semipermeable membrane (31) 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 interlayer spacing between the GO flakes in the range of 0.7-1.4 nm. The interlayer spacing between the stacked graphene oxide flakes can be measured by any suitable method known in the art, for example, using XRD.

[0055] Advantageously, the pore size of the nanoporous carbon membrane may be in the range of 0.7 nm to 1.5 nm, preferably ≦1.4 nm, more preferably ≦1.3 nm, even more preferably ≦1.1 nm, and even more preferably ≦1.0 nm. "Pore size," when referring to carbonaceous semipermeable membranes, refers to the pore size in the case of carbon nanotube and nanoporous graphene membranes, and the width of the interlayer spacing in the case of multilayer GO or rGO membranes. Typically, the nanoporous carbon membrane may be 0.05 μm to 1 μm thick, preferably 100 to 500 nm thick, in the case of carbon nanotube membranes. In the case of multilayer GO or rGO membranes, the carbon membrane should have a thickness of at least 2, preferably at least 3, It may contain up to 300 layers of GO or rGO sheets and may be 0.05-20 μm thick, e.g., 0.05-15 μm thick, 0.05-10 μm thick, 0.05-5 μm thick, or 0.05-1 μm thick. For example, the carbon film may be about 0.1 μm thick.

[0056] In another variant, the semipermeable membrane can be a laminate of lamellar materials. Any lamellar material can be used, such as MoS2, hexagonal NiB, clay, or graphite.

[0057] For example, the semipermeable membrane can be a multilayer MoS2 membrane, a layer hexagonal NiB membrane, or a multilayer GO or rGO membrane, preferably a multilayer GO or rGO membrane, most preferably a multilayer GO membrane.

[0058] In another exemplary variation, the semipermeable membrane can be an ion exchange membrane, such as an anion exchange membrane (eg, OH − , Cl − transport) or a cation exchange membrane (eg, H + , Na + , K + transport).

[0059] The semipermeable membrane can be placed directly on the nanoporous membrane element (32) having a surface charge. This can be achieved, for example, by vacuum filtration, preferably under wet conditions (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, graphite-based) in water can be added dropwise under vacuum to the top of the nanoporous membrane having a surface charge. For example, the nanoporous membrane having a surface charge can be placed on a Buchner funnel connected to a vacuum pump, and the dispersion of the carbonaceous material or lamellar material in water can be added slowly (e.g., dropwise) to the nanoporous membrane having a surface charge to form a membrane (semipermeable membrane element) with the carbonaceous material or lamellar material laminated thereon. Alternatively, the semipermeable membrane can be first placed on another porous support layer (33) (e.g., for ease of manufacture and / or handling) and then placed on the nanoporous membrane element (32) having a surface charge. The porous support layer (33) should have a much larger pore size to allow the polar solvent of the electrolyte solution (11A) to flow from the container (10A) to the container (10B) through the reverse osmosis membrane element (30). Therefore, when used, the porous support layer preferably has a pore size at least 5, 10, or more times larger than the pore size of the semipermeable membrane element (32) and a thickness of 30 to 300 μm, more preferably 100 to 200 μm. The porous support layer (33) can be made of a neutral (no surface charge), non-reactive polymeric material, such as a fluoropolymer such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), or a mixed cellulose ester or cellulose acetate. It can also be made of a porous ceramic material, such as alumina, or a silica-based porous ceramic, by way of non-limiting example.

[0060] When the semipermeable membrane (31) is disposed on the porous support layer (33), the resulting combination filtration membrane can be used in any orientation, i.e., so that either the semipermeable membrane side or the porous support side can be in contact with the nanoporous membrane element (32) bearing the surface charge. Combination filtration membranes in which the semipermeable membrane (31) is disposed on both sides of the porous support layer (33) or, alternatively, between two porous support layers, as well as multi-layer combination filtration membranes in which two or more layers of semipermeable membrane (31) alternate with two or more layers of porous support (33) can also be used.

[0061] Advantageously, the semi-permeable membrane may be adapted to achieve a solute rejection of preferably 98.0% or greater, preferably ≧98.5%, more preferably ≧99.0%, even more preferably ≧99.5%, and most preferably 100% or about 100%.

[0062] Naturally, the average pore size of the semipermeable membrane is adapted to the solutes that it is intended to filter out.

[0063] 1.2. Nanoporous membranes with surface charges Nanoporous membranes usable in the context of the present invention can be any membrane with a surface charge known in the art that is nanoporous, i.e., any nanoporous membrane in which at least a portion of the inner surface of the nanochannels of the membrane is essentially formed of at least one material with an appropriate surface charge. As used in this disclosure, unless otherwise specified, the term "essentially formed" of a material means "made from the material." This term also encompasses the possibility of optionally chemically modifying the material (e.g., on the surface and / or on the pore wall surface) to adjust its physicochemical properties to suit the intended application. Chemical modifications can include doping (e.g., adding metal elements to the surface or core of the material network), coating (e.g., using a thin layer of a material with a suitable surface charge), covalent functionalization, such as physisorption or chemisorption of compounds / species 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.

[0064] In one preferred embodiment, at least a portion of the interior surface of the nanochannel is essentially formed of or coated with at least one material having a suitable surface charge. Advantageously, the nanochannel may preferably be completely formed of or coated with at least one material having a suitable surface charge.

[0065] 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 formed essentially of a material having an appropriate surface charge, or the entire inner surface may be formed essentially of at least one material having an appropriate surface charge. The sections may be regular or irregular, intermittent or non-intermittent, and / or in the form of a single layer or multiple layers. Preferably, the entire inner surface of the nanochannel is formed essentially of at least one material having an appropriate surface charge.

[0066] Nanoporous membranes that can be used in the context of the present invention can have a positive or negative surface charge.

[0067] When the nanoporous membrane has a positive surface charge, application of an electric field between electrodes (20A) and (20B) (where electrode (20B) is in contact with the electrolyte solution (11B) in the second container (10B) and is positively charged) induces a flow of anions in the electrolyte solution (11B) from the positively charged pore surface of the nanoporous membrane element (32) toward electrode (20B). This flow of anions simultaneously induces a flow of polar solvent through the reverse osmosis membrane element (30) from the first container (10A) toward the second container (10B).

[0068] Conversely, when the nanoporous membrane has a negative surface charge, application of an electric field between electrodes (20A) and (20B) (where electrode (20B) in contact with the electrolyte solution (11B) in the second container (10B) is negatively charged) induces a flow of cations in the electrolyte solution (11B) from the negatively charged pore surface of the nanoporous membrane element (32) toward electrode (20B). This flow of cations simultaneously induces a flow of polar solvent through the reverse osmosis membrane element (30) from the first container (10A) toward the second container (10B).

[0069] Advantageously, the nanoporous membrane with a positive or negative surface charge has a surface charge with a |Zeta potential| of ≧5 mV, preferably ≧20 mV, most preferably ≧50 mV.

[0070] Examples of materials having a surface charge suitable for use in nanoporous membrane elements according to the present invention include titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, and the like. Examples of suitable nanoporous membrane elements include anodic alumina, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, or polyelectrolyte polymer membranes, such as nanoporous membranes obtained by successive dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) onto a polycarbonate membrane. Ni2dobdc and Mg2dobdc are known metal-organic frameworks containing dobdc ligands and Ni or Mg metal sites, respectively. Advantageously, materials with surface charges suitable for nanoporous membrane elements according to 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.

[0071] Titanium oxide refers to 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 forms. With regard to titanium dioxide (TiO2), the rutile or anatase crystalline forms are mainly used, with the anatase form being preferred.

[0072] As used herein, "formed essentially of titanium oxide, boron nitride, etc." refers to a material formed from titanium oxide, boron nitride, etc., which may contain small amounts of elements such as impurities.

[0073] The physicochemical properties of materials such as titanium oxide, boron nitride, anodized aluminum oxide, SiO2, etc. can generally be adjusted and amplified by doping or functionalization, i.e., by inserting metallic elements such as iron, silver, vanadium, gold, platinum, niobium, tungsten, etc., or non-metallic elements such as nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, etc., or different compounds of silanes, amines or other organic families, preferably in small amounts, on the surface or within the core of the material network.

[0074] For example, the nanoporous membrane material may be titanium oxide, which can be doped on the surface or within the core of the crystalline network by inserting metallic elements such as iron, silver, vanadium, gold, platinum, niobium, tungsten, or non-metallic elements such as nitrogen, sulfur, carbon, hydrogen, boron, phosphorus, or different compounds such as silanes, amines, etc., preferably in amounts of 0.5-10 wt %, more preferably 1-5 wt %.

[0075] Nanoporous 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 nanoporous membrane may consist of a flexible polymer membrane onto which a layer of at least one material with a suitable surface charge, such as TiO2, has been deposited.

[0076] Membranes containing nanochannels with an inner surface essentially formed of or coated with at least one material with a suitable surface charge, such as ceramic membranes (e.g., titanium oxide, anodized aluminum oxide, SiO2), can be obtained directly by anodizing metal foils (e.g., Ti, Al, or Si) (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. 2 904-2939). Other techniques, such as the sol-gel method in the presence of block copolymers or grafted copolymers, also allow the synthesis of ceramic membranes, such as TiO2 membranes, with regularly oriented nanochannels (see Jung Tae Park, Won Seok Chi, Sang Jin Kim, Daeyeon Lee & Jong Hak Kim, Scientific Reports 4:5505, Nature, 2014). This method also allows for the control of the morphological parameters of the through-hole nanochannels, such as length, width, and asymmetry. In addition, powder and sintering methods can be used to obtain very thin ceramic membranes, such as titanium oxide membranes, with regularly controlled through-hole nanochannels. Such membranes can also be obtained using various deposition techniques, for example, by CVD (chemical vapor deposition), ALD (atomic layer deposition), or HiPIMS (high-power impulse magnetron sputtering) on ​​nanoporous substrates with preformed morphologies.

[0077] Alternatively, the surface of a negatively or positively charged material may be chemically modified to enhance the negative or positive charge naturally present on the material after contact with an electrolyte solution at a given pH, respectively. In other words, the surface of the charged nanoporous membrane 32 can be chemically modified to enhance the surface charge of the nanoporous membrane. The chemical modification can be achieved by chemical vapor deposition, atomic layer deposition, sol-gel coating, or dip coating. Advantageously, the chemical modification can be achieved on the surface of the nanoporous membrane pore walls. For example, the charged nanoporous membrane 32 can be obtained from a polycarbonate membrane having an average pore diameter of <500 nm, preferably <300 nm, and more preferably <200 nm, whose internal pore walls have been chemically modified by dip-coating the polycarbonate membrane in an aqueous polydopamine solution. At pH=7, polycarbonate has a negative surface charge, which is enhanced when the polycarbonate surface is coated with a polyamine.

[0078] In another alternative, if the surface of the membrane material has ionizable functional groups, the surface charge of the membrane can be adjusted using pH. For example, for membrane materials such as TiO2, SiO2, and Al2O3, which have -OH groups on their surface, changing the pH of the electrolyte solution in contact with the membrane to a basic value (pH = 8-14) deprotonates the -OH groups, thereby enhancing the negatively charged surface. Therefore, the zeta potential of the membrane surface can be adjusted / controlled using changes in pH. In practice, the surface charge of the same membrane can be positive or negative depending on the pH of the electrolyte solution in contact with the nanoporous membrane element (32). For example, a nanoporous membrane element (32) made essentially of TiO2 can have a negative surface charge at pH ≥ 9 and a positive surface charge at pH ≤ 6.

[0079] Without wishing to be bound by any particular theory, nanochannels of materials with negative surface charges are likely to be formed by considering their type, size, and physicochemical properties, in particular their surface charge density in the order of: titanium dioxide: ∼−100 mC / m 2 (pH ≥ 9) Boron nitride: ~-1C / m 2 (pH ≥ 10) Silicon dioxide: ~-10mC / m 2 (pH ≥ 6) Polycarbonate: ~-10mC / m 2 (pH ≥ 5) It has been proposed that the passage of cations (i.e., ions with a charge opposite to the surface charge of the material) is facilitated through the phenomenon of electroosmosis nanofluidics, which is induced by the application of an electric field. The flow of cations from the Debye layer at the interface of the negatively charged membrane surface, which is overall charged due to the imbalance of anions and cations under the influence of the surface charge, then induces a flow of polar solvent in the same direction as the cation flow. Thus, under the application of a suitable electric field, the polar solvent flows from the container (10A) to the container (10B) through the reverse osmosis membrane element (30). Because the reverse osmosis membrane element (30) includes a semipermeable membrane element (31) selected for one or more specific solutes present in the electrolyte solution (11A), the flow of cations generated within the pores of the nanoporous membrane (32) induces the flow of the electrolyte solution (11A) from the container (10A) to the container (10B) while preventing the solutes from passing through (the solutes are filtered out and remain in the container (10A)).

[0080] Conversely, nanochannels in materials with a positive surface charge have been proposed to facilitate 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 caused by the application of an electric field.

[0081] In both cases (cation or anion flow), the polar solvent flow is induced in the same direction as the cation / anion flow generated by application of a suitable electric field between electrodes (20A) and (20B).

[0082] The membrane surface charge can be measured using any suitable method known in the art, for example, the zeta potential of the nanoporous membrane can be elucidated using an electrokinetic analyzer.

[0083] The following equation can be implemented to estimate the zeta potential value on the surface of the membrane:

[0084]

number

[0085] When nanoporous membranes with low tortuosity porosity are used (e.g., nanoporous anodic alumina with mostly cylindrical pores), the length of the pores L can correspond to the thickness of the nanoporous membrane. For nanoporous membranes with significantly tortuosity pores, the total pore length can be determined by calculating the permeability versus applied pressure and applying the associated tortuosity factor.

[0086] 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 concentration of a suitable acid (e.g., HCl) or base (e.g., KOH, NaOH, etc.). Preferably, the acid / base is selected for its compatibility with the ions present in the electrolyte solution used in the process / system according to the present invention. For example, if a KCl electrolyte solution is used, KOH can be used as a base to adjust the pH.

[0087] For example, if a |zeta potential| of at least 5 mV is desired at the membrane surface, a membrane material with a high surface charge can be selected, which will allow the membrane to maintain a high zeta potential at the surface when in contact with an electrolyte solution.

[0088] Average pore size - nanoporous membrane Nanoporous membrane element (32) preferably has a larger average pore size than semipermeable membrane element (31), and the function of filtering solutes is performed by semipermeable membrane element (31), while the function of nanoporous membrane element (32) is to facilitate reverse osmosis flow of solvents upon application of an appropriate electric field between electrodes (20A) and (20B).

[0089] Advantageously, the nanoporous membrane element (32) with a positive or negative surface charge may have an average pore diameter 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 nanoporous membrane element (32) may be between 1 and 500 nm, preferably between 1 and 300 nm, more preferably between 10 and 100 nm, and most preferably between 10 and 50 nm.

[0090] As used herein, the term "mean diameter" refers to the internal average diameter of a nanochannel. The nanochannel may have a nanotubular, conical asymmetric, necked, or porous substrate morphology. When the nanochannel has a nanotubular morphology, i.e., a circular cross section, the mean diameter corresponds to the internal diameter of the circular cross section. When the nanochannel has a conical asymmetric, necked, or porous substrate morphology, i.e., an elliptical or irregular cross section, the mean diameter corresponds to the average of the smallest and largest internal diameters. The mean diameter of a nanochannel can be measured using means known to those skilled in the art. For example, the mean diameter can be measured by scanning electron microscopy or transmission electron microscopy. Advantageously, the nanochannels contained in the nanoporous membrane element (32) can have a uniform diameter. When the nanochannels do not all have a uniform diameter on one and the same membrane, the mean diameter corresponds to the average of the mean diameters of all the nanochannels.

[0091] Advantageously, in the context of the present invention, nanochannels have a nanotubular, conical asymmetric, necked or perforated substrate morphology, preferably said nanochannels have a conical asymmetric morphology.

[0092] The morphological parameters of nanoporous membranes usable in the context of the present invention can be evaluated using conventional techniques, such as scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal scanning laser microscopy (CSLM), and transmission electron microscopy (TEM). Alternatively, or in addition, X-ray computed 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, and therefore capable of performing 3D (volume) analysis). These techniques can be used to evaluate the morphological parameters of nanoporous membranes according to the present invention, such as pore size, pore size distribution, surface roughness, molecular weight cutoff, and thickness.

[0093] 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 is >2 nm, and the width of slit-shaped pores is <2 nm). When pores have irregular shapes, some averaging is performed to arrive at the average pore size. Methods 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), including some statistical analysis techniques 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 geometric shape. Considering the chemical and physical properties of the nanoporous membrane element (32) and the range of the average pore diameter (preferably, the average diameter of the nanochannels of the nanoporous membrane element (32) can be 1 to 500 nm, preferably 1 to 300 nm, more preferably 10 to 100 nm, and most preferably 10 to 50 nm), according to the ISO 15901 standard, the average pore diameter can be measured by nitrogen gas adsorption at -196°C (liquid nitrogen temperature).

[0094] Nanoporous membranes usable in the context of the present invention can be symmetric or asymmetric. As used herein, when referring to a nanoporous membrane according to the present invention, "asymmetric" means that the nanoporous membrane pore size distribution is not uniform across the membrane thickness. Conversely, a symmetric membrane has a uniform pore size distribution across the membrane thickness. Typically, in an asymmetric membrane, there is a very thin, dense surface layer that acts as a functional layer on top of a porous sublayer with a specific pore diameter. Asymmetric membrane For example, an asymmetric membrane consists of a thin skin layer (selective barrier) of 0.1 to 1 μm thick over a highly porous 100 to 200 μm thick substructure. The pore size of the porous sublayer can range from about ≦1 nm to about 500 nm, and the pore size range defines the type of application for which the asymmetric membrane can be used: microfiltration (50 to 500 nm), ultrafiltration (1 to 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 aforementioned pore size values ​​represent the arithmetic mean of the pore size distribution observed by scanning electron microscopy (SEM) across the membrane cross-section.

[0095] Advantageously, the average cross section of the nanoporous membrane nanochannels and their particular regular perforation morphology promote a good diffusion of the solution through the membrane. Thus, the nanoporous membrane element (32) sets itself clearly apart from the semipermeable membrane element (31) through nanochannels that potentially allow the circulation of both water molecules and ions, since each of the nanochannels advantageously has a cross section larger than the size of these molecules.

[0096] Thus, in one aspect, a reverse electroosmosis filtration system according to the present invention combines a semipermeable membrane (31) with a charged nanoporous membrane (32) having a surface charge, preferably stacked with the charged nanoporous membrane (32). This invention significantly overcomes technical deficiencies related to surface chemistry that can adversely affect the performance of charged membranes in their ability to electrically induce the flow of electrolyte solution (11A) from the container (10A). For example, it can be expected that the association of GO and 2D material membranes with oxide-type membranes (e.g., aluminum oxide, silicon oxide, titanium oxide) can, under certain conditions, form chemical bonds between the two surfaces (via hydroxyl condensation), making the delamination of the composite membrane elements more difficult and potentially compromising the stability and overall performance of the composite membrane elements. Unlike existing technical deficiencies, the present inventors have reduced the need to implement a highly stable, high-performance composite membrane by associating a semipermeable membrane (31) with a charged nanoporous membrane (32) having a surface charge.

[0097] 1.3. Exemplary Features of Composite Membrane Filtration Systems In an exemplary embodiment, a reverse electroosmosis filtration system according to the present invention may combine a particularly advantageously selected semipermeable membrane (31), a charged nanoporous membrane (32) having a surface charge with a |zeta potential| of ≧5 mV, and electrodes (20A) and (20B).

[0098] The semipermeable membrane (31) can be selected from a nanoporous carbon membrane or a laminated membrane of lamellar materials. The nanoporous carbon membrane or the laminated membrane of lamellar materials can be as described above. 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, even more preferably ≦1.1 nm, and even more preferably ≦1.0 nm. For example, the semipermeable membrane can be a multilayer MoS2 membrane, a multilayer hexagonal NiB membrane, or a multilayer GO or rGO membrane, preferably a multilayer GO or rGO membrane, and most preferably a multilayer GO membrane. Advantageously, the semipermeable membrane (31) can be a size-exclusion selective membrane composed of stacked graphene oxide flakes.

[0099] The charged nanoporous membrane (32) having a surface charge of |Zeta potential| ≥ 5 mV can be made from titanium oxide, boron nitride, SiO2, polyethersulfone, polycarbonate, anodized aluminum oxide, preferably titanium oxide, boron nitride, SiO2, polycarbonate, and anodized aluminum oxide, most preferably titanium oxide, polycarbonate, and anodized aluminum oxide.

[0100] The semipermeable membrane (31) is preferably overlaid with a charged nanoporous membrane (32). The semipermeable membrane may be placed directly on the nanoporous membrane element (32) bearing a surface charge, or may first be placed on a separate porous support layer (33) (e.g., for ease of manufacture and / or handling). ), which can then be placed on the nanoporous membrane element (32) having the aforementioned surface charge.

[0101] 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, 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. Preferably, the first and second electrodes (20A) and (20B) can be carbon electrodes (the advantage of which is that the filtration system according to the present invention can be operated at very low voltages (as low as 1-2 V)).

[0102] 2. Hybrid membrane An exemplary embodiment is shown in FIG.

[0103] In another variant, the reverse osmosis membrane element (30) may be a hybrid membrane element, in which the semipermeable membrane element (31) and the nanoporous membrane element (32) with a surface charge are one and the same element to form a single hybrid membrane (30B). Advantageously, the hybrid membrane (30B) may have a predetermined pore size and zeta potential adapted to the target solute to be concentrated / depleted or removed / filtered. Advantageously, the single hybrid membrane (30B) may have an average pore size adapted to the filtration of the target solute from the electrolyte solution (11A) and a surface charge on the inner pore wall surface of the hybrid membrane with a |zeta potential| of ≧5 mV, preferably ≧20 mV, and most preferably ≧50 mV.

[0104] For example, the average pore size of the hybrid membrane (30B) is sufficiently small to prevent the target solute (and any other solutes with a particle size larger than the target solute) from passing through the hybrid membrane (30B), while allowing polar solvents and other smaller solutes to pass through the hybrid membrane (30B). The average pore size of the hybrid membrane (30B) is adapted depending on the intended type of application: microfiltration (50-500 nm), ultrafiltration (1-50 nm), or nanofiltration (≦1 nm). Advantageously, the porosity of the hybrid membrane (30) (i.e., the average pore size measured according to the ISO 15901 standard) can be <500 nm, preferably <300 nm, more preferably <100 nm, and most preferably <50 nm. In a preferred variant, the filtration system is intended for ultrafiltration, and the hybrid membrane (30B) can have a porosity with an average pore size of 1-50 nm.

[0105] The hybrid membrane element may be a nanoporous membrane having a suitable (positive or negative) surface charge as described generally and in any of the above variants, such as the preferred and advantageous variants, and having an average pore size adapted to remove / filter target solutes from the electrolyte solution (11A), as described in the immediately preceding paragraph. The portion of the description relating to nanoporous membranes will not be repeated here for the sake of brevity, but it will be understood that it applies mutatis mutandis to the hybrid membrane element.

[0106] Advantageously, the hybrid membrane (30B) has a |zeta potential| of ≥ 5 mV, preferably ≥ 20 mV, most preferably ≥ 50 mV, and is a nanoporous membrane essentially formed from a material with a positive or negative surface charge, such as TiO2, boron nitride, SiO2, polyethersulfone, polycarbonate, anodic aluminum oxide, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, or a polyelectrolyte layer polymer membrane, such as a nanoporous membrane obtained by successive dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) on a polycarbonate membrane, preferably TiO2, BN, SiO2, polycarbonate, anodic alumina, hydrotalcite, Ni -Fe layered double hydroxide, Ni2dobdc, Mg2dobdc, cellulose or polyelectrolyte layer polymer membrane, most preferably TiO2, BN, anodic alumina, SiO2, or polycarbonate.

[0107] Advantageously, the hybrid membrane (30B) is a size-exclusion selective membrane coated on its inner pore walls with a material having a |zeta potential| of ≥ 5 mV, preferably ≥ 20 mV, most preferably ≥ 50 mV, and having a positive or negative surface charge, 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), cell The cellulose or polyelectrolyte layer polymer membrane, for example, a nanoporous membrane obtained by successive dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) on a polycarbonate membrane, preferably TiO2, BN, SiO2, polycarbonate, anodic alumina, hydrotalcite, Ni-Fe layered double hydroxide, Ni2dobdc, Mg2dobdc, cellulose or polyelectrolyte layer polymer membrane, most preferably TiO2, BN, anodic alumina, SiO2, or polycarbonate.

[0108] Containers (10A) and (10B) In the present disclosure, any reverse osmosis membrane element (30) separating vessels (10A) and (10B) may be used without particular limitation, so long as it does not allow solutes to permeate therethrough and primarily allows solvents to permeate therethrough. Advantageously, reverse osmosis membrane element (30) may be adapted to achieve solute rejection of preferably 98.0% or greater, preferably ≥ 98.5%, more preferably ≥ 99.0%, even more preferably ≥ 99.5%, and most preferably 100% or about 100%.

[0109] To carry out the process according to the invention, any separation device / system comprising two compartments separated by a reverse osmosis membrane element (30) can be used: the mixture to be separated is placed in the first compartment (vessel (10A)), and the extracted organic compounds are collected in the second compartment (vessel (10B)).

[0110] In the present disclosure, the reverse electroosmosis filtration / purification system can be implemented in a batch or continuous manner to maximize its effectiveness. For example, the reverse electroosmosis filtration / purification system according to the present invention can be configured in multiple stages. In other words, the unit "vessel (10A) - reverse osmosis membrane element (30) - vessel (10B)" can be configured in multiple stages.

[0111] In one exemplary variation, a reverse electro-osmosis filtration / purification system can be provided comprising N vessels (10) and N-1 reverse osmosis membrane elements (30), where N is an integer. For example, N can be in the range of 3 to 100, more specifically 3 to 50. In this multi-vessel device, the vessels and reverse osmosis membrane elements can be as defined above. Thus, an assembly can be formed with alternating vessels (10) containing electrolyte solutions enriched in a target solute and electrolyte solutions with lower concentrations, separated from each other by reverse osmosis membrane elements (30).

[0112] Polar solvents The polar solvent may advantageously be a solvent capable of generating acidic ions, for example, water, an alcohol such as methanol or ethanol, a water-alcohol mixture, ammonia, acetone, or acetonitrile.

[0113] Electrolyte solutions (11A) and (11B) and solutes The electrolyte solution that can be used in the context of the present invention comprises, in a polar solvent as defined herein: It can be any electrolyte solution containing at least one solute of interest / undesirable solute.

[0114] For example, the solvent can be water or an aqueous solution.

[0115] In a preferred variant, the electrolyte solution may be an aqueous solution containing an electrolyte. The electrolyte may be any chemical species, 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 may be a synthetic solution, freshwater from a lake or river, groundwater, brackish water, seawater, industrially produced water, petroleum-produced water, or a natural solution such as a biological fluid.

[0116] Examples of solute-containing aqueous solutions that can be used as electrolyte solutions according to the present invention include seawater, brackish water, cellular metabolic products, reaction products, biological fluids, etc., and cellular metabolic products are intended to include animal cells, plant cells, or microbial cultures, their primary metabolic products, secondary metabolic products, in vitro secreted proteins, biotransformation products, etc.

[0117] Examples of reaction solutions include chemical reaction products and enzymatic reaction products.

[0118] Examples of microbial primary metabolites include, but are not limited to, organic acids (e.g., acetic acid, propionic acid, butyric acid, lactic acid, succinic acid, etc.), alcohols (e.g., ethanol, butanol, etc.), hexane, amino acids (e.g., lysine, tryptophan, etc.), vitamins, polysaccharides, etc.

[0119] Examples of microbial secondary metabolites include antibiotics (e.g., penicillin), enzyme inhibitors, physiologically active substances (e.g., taxol), etc., and examples of in vitro secreted proteins of microorganisms include enzymes such as amylase and cellulase, insulin, interferon, monoclonal antibodies, etc. Furthermore, microbial biotransformation products are substances produced by using microorganisms or enzymes, and examples thereof include, but are not limited to, steroids, etc.

[0120] Examples of biological fluids include blood, serum, plasma, urine, saliva, tears, dialysate, intestinal contents, parenteral nutrition solutions, seminal plasma, and cerebrospinal fluid.

[0121] 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, more preferably the solute is NaCl.

[0122] The solute may be selected from solid particles, organic or inorganic small molecules such as dye complexes (e.g., tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate), biomolecules such as hormones (e.g., testosterone), proteins, polysaccharides, polynucleotides, polypeptides, enzymes or antibodies, pollutants (e.g., from wastewater, industrially produced water, or landfill leachate), metabolic waste, or salts / ions. If the solute of interest to be concentrated is solid, it is preferably a material that readily crystallizes in response to temperature and pH and is not highly viscous even at high concentrations.

[0123] In the present disclosure, the solute may be a salt (or liquid) and the solvent may be water. For example, the electrolyte solution (11A) may be seawater, the solute may be NaCl, and the process may be saltwater desalination. Accordingly, the present invention also relates to a saltwater desalination system comprising a reverse electroosmosis filtration system according to the present invention, in any of the variations described herein. Thus, in one aspect, the present invention relates to a seawater desalination process, the process comprising: i) a reverse electroosmosis filtration system; So, a) a first vessel (10A) containing seawater and provided with a first electrode (20A), the first electrode (20A) being in contact with the seawater contained in the first vessel (10A); b) a second vessel (10B) containing seawater and equipped with a second electrode (20B), the second electrode (20B) being in contact with the seawater contained in the second vessel (10B), the first and second electrodes (20A) and (20B) being operably connected to a source of electrical energy (40); c) a reverse osmosis membrane element (30) separating the first and second vessels (10A) and (10B), (i) a semipermeable membrane element (31) having an average pore size of <1 nm, and (ii) a nanoporous membrane element (32) having a surface charge of |Zeta potential| ≥ 5 mV, preferably ≥ 20 mV, most preferably ≥ 50 mV, as measured using an electrokinetic analyzer, wherein the nanoporous membrane has an average pore size of < 1 μm, preferably < 500 nm, as measured according to the ISO 15901 standard; the semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two different elements, preferably superimposed on one another; a reverse osmosis membrane element, wherein the semipermeable membrane element (31) is in contact with seawater contained in a first container (10A) and the nanoporous membrane element (32) having a surface charge is in contact with water contained in a second container (10B), the reverse osmosis membrane element (30) fulfills both the functions of (i) solute filtration and (ii) electrically conducting the flow of water from the first container (10A) to the second container (10B) through the reverse osmosis membrane element (30); the reverse osmosis membrane element (30) is adapted to selectively block the diffusion of Na+ and Cl- through the reverse osmosis membrane element (30); and ii) applying an electric field between the first electrode (20A) and the second electrode (20B) to induce a reverse osmosis flow of water from the first container (10A) to the second container (10B) through the reverse osmosis membrane element (30) separating the first and second containers (10A) and (10B), thereby allowing the Na+ and Cl- solutes to be retained within the first container (10A) while allowing water to flow from the first container (10A) towards the second container (10B); and iii) recovering demineralized water from the second vessel (10B) substantially free of Na+ and Cl- solutes, wherein ≥99%, preferably ≥99.5%, more preferably ≥99.8%, even more preferably ≥99.9%, and most preferably 100% of the Na+ and Cl- solutes are retained in the seawater contained in the first vessel (10A). This process results in the water contained in the first vessel (10A) being more concentrated in NaCl than the seawater placed in the first vessel (11A) at the start of the process. Conversely, this process allows fresh water ("eau douce" in French) to be recovered in the second vessel (11B). The semipermeable membrane element (31) can be any semipermeable membrane for use in water purification or desalination systems, reverse osmosis systems, such as a thin film composite membrane (TFC or TFM). The semipermeable membrane element (31) can be any nanofiltration semipermeable membrane. For example, the nanoporous carbon membranes described herein may have pore sizes in the range of 0.7 nm to 1.5 nm, preferably ≦1.4 nm, more preferably ≦1.3 nm, even more preferably ≦1.1 nm, and even more preferably ≦1.0 nm, and may be suitable for desalination processes according to the present invention. For example, the semipermeable membrane (31) may be a size-exclusion selective membrane composed of stacked graphene oxide or reduced graphene oxide flakes, preferably a size-exclusion selective membrane composed of stacked graphene oxide flakes. While salinity varies across the ocean, the relative proportions of the most predominant dissolved components remain substantially constant. Sodium (Na+) and chloride (Cl−) ions account for approximately 91% of all ions in seawater, although there are small amounts of other ions (e.g., K+, Mg2+, S042−) in seawater. Advantageously, the present invention provides a method for the desalination process according to the present invention. The process of desalination of seawater by light can produce a removed stream having a salinity of ≦5% (≦50 parts per thousand), preferably ≦3% (≦30 ppt), more preferably ≦1% (≦<10 ppt), and most preferably ≦0.5% (≦5 ppt). Salinity is often derived from electrical conductivity (EC) measurements. EC is measured by passing an electric current between two metal plates or electrodes in a water sample and measuring how easily the current flows between the plates. The use of EC measurements to estimate the ionic content of seawater led to the development of the Practical Salinity Scale of 1978 (PSS-78, developed by the Joint Panel on (It has been reviewed by the Oceanographic Tables and Standards and is recommended by all oceanographic organizations as the scale for reporting future salinity data.) The practical salinity of a seawater sample is defined as the ratio of the electrical conductivity of the seawater sample at a temperature of 15°C and a pressure of 1 standard atmosphere to the electrical conductivity of a potassium chloride (KCl) solution containing 32.4356 g of KCl per kg of solution at the same temperature and pressure. A ratio equal to 1 corresponds to a practical salinity of 35 (standard seawater). Because the definition is a ratio, practical salinity is expressed as a dimensionless number.

[0124] The present invention also relates to a purification system including a reverse electroosmosis filtration system according to the present invention, in any variation as described herein. For example, the water contaminants to be filtered can include endocrine disruptors, hormones, pesticides, and / or dyes.

[0125] More precisely, in one aspect, the invention relates to a method for purifying a liquid containing water and impurities, implementing the electroreverse osmosis method, to purify water, where water purification generally means any operation consisting in treating water containing an initial content of impurities so that at the end of this operation the final content of impurities is lower than the initial content. The impurities are the elements that make up pure water, namely HO, OH, etc. - , and H +means any element, molecule, ion, or other entity different from that of the element. For example, the purification process may be a process for desalination of seawater, a process for treating industrial produced water, or a process for treating landfill leachate.

[0126] Thus, in one aspect, the present patent application promotes a method for recovering potable water from a vast source of saltwater, particularly surface waters containing various concentrations of sodium chloride. Applications range from less than 1% to 20% salinity, for example, to 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 with a salinity of 5% to 20%.

[0127] In the present disclosure, the solute-containing electrolyte solution may be a biological fluid, preferably a dialysis fluid. Accordingly, the present invention also relates to an implantable artificial kidney comprising a reverse electroosmosis filtration system according to the present invention, in any of the variations described herein.

[0128] The principle behind the present invention is that the reverse osmosis membrane element (30) (a single hybrid membrane), or at least a portion thereof (a composite membrane comprising a semipermeable membrane element (31) and a nanoporous membrane element (32)), has a sufficient surface charge (which may be positive or negative) to induce a zeta potential at the membrane / electrolyte solution interface that is high enough to induce the flow of anions or cations, respectively, through the nanochannels of the nanoporous membrane upon application of a suitable electric field between electrodes (20A) and (20B).

[0129] This phenomenon is governed by the same principles as the zeta potential applied to a suspension of colloidal particles.

[0130] In the case of colloidal suspensions, the fact that many organic and mineral colloidal particles have a negative charge in an aqueous environment causes them to repel each other and maintain the stable state of dispersion that characterizes them. The electrochemical dispersion of colloidal particles has been studied for many years. Several models, such as the bilayer and DLVO theories, have been developed to explain colloidal stability. The bilayer 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 attracted by the particle's charge, will exhibit a polarity opposite to the particle's own natural 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 potential between the two layers, generally referred to in the art as the zeta potential, generates a repulsive force that offsets the attractive van der Waals forces between the particles. If the outer layer is diffused over a sufficiently large 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 diffusion radius of the outer layer is reduced to the point where the van der Waals forces are overcome, the particles will be attracted to each other and form aggregates that tend to separate from the liquid phase.

[0131] Extending this principle to the present invention, a dense layer at the surface of the inner pore walls of a nanoporous membrane, consisting of ions in the electrolyte solution attracted by surface charges present on the surface of the inner pore walls of the nanoporous membrane, exhibits a polarity charge opposite to the natural charge of the nanoporous membrane itself under the physical and chemical conditions of the electrolyte solution. An outer layer of opposite polarity, also consisting of ions in the solution, is diffused within a given distance from the surface of the nanoporous membrane. The net potential between the two layers is called the zeta potential. The zeta potential is the potential difference between the dense Stern layer and the liquid. Thus, it characterizes the distribution of charge on the surface of the inner pore walls of a nanoporous membrane.

[0132] The zeta potential therefore depends on the ionic strength of the electrolyte solution and the ion concentration in the solution around the membrane surface.

[0133] To increase the data potential and improve the reverse osmosis flow generated on either side of the reverse osmosis 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 nanochannels of the nanoporous membrane with surface charge (32) (composite membrane element) or (32A) (hybrid membrane element).

[0134] The effect of pH on membrane surface charge can be studied by measuring the zeta potential of nanoporous membrane samples in electrolyte solutions of different pH. The zeta potential of a nanoporous membrane can move toward negative values ​​with increasing pH values ​​of the electrolyte solution. For example, one mechanism by which increasing pH can drive the zeta potential toward negative values ​​involves the deprotonation of species at the surface of the membrane's interior pore walls (e.g., OH to O). - to (e.g., at the surface of a TiO2 or SiO2 film).

[0135] For example, when a ceramic nanoporous membrane, such as a TiO or BN nanoporous membrane, is used, the pH of the solution can be adjusted to a value of (pHiso + 1) to 14, more preferably (pHiso + 2) to 12, to obtain a negative charge on the inner surface of the nanochannel. To obtain a positive charge on the inner surface of the nanochannel, the pH of the solution can be adjusted to a value of 0 to (pHiso - 1), more preferably 1 to (pHiso - 2). The increase in the negative zeta potential value of the nanoporous membrane with increasing pH can occur, for example, due to the deprotonation of functional groups on the membrane surface.

[0136] 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 potentiometric acid-base titration.

[0137] When the electrolyte solution containing the solute is an aqueous solution, the aqueous solution will be determined based on the nature of the nanoporous membrane and the surface charge naturally present thereon, as well as the temperature at which water is maintained in a liquid state, e.g. For example, the pH may be 2 to 13 depending on the temperature, for example, 0 to 100°C, preferably 15 to 50°C, and more preferably 20 to 40°C. The temperature may be higher or lower than the above temperatures. For example, other solute / solvent mixtures may have temperatures that deviate from the above temperatures.

[0138] Electrodes (20A) and (20B) As previously mentioned, each of the vessels (10A) and (10B) of the purification / filtration system according to the present invention comprises an electrode (20A and 20B, respectively) arranged so that the electrode is in contact with the electrolyte solution (11A and 11B, respectively). Different types of electrodes may be used in the context of the present invention.

[0139] Cations or anions (e.g., Na + or Cl - Any type of electrode capable of collecting the current of ions, preferably silver and silver chloride (Ag / AgCl), carbon and platinum (C / Pt), carbon (C), graphite, or [Fe(CN)6] 4- / [Fe(CN)6] 3 Electrodes made of iron composites of the type described above may be used. The first and second electrodes (20A) and (20B) may be any metal or carbon electrode capable of exhibiting 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) may be platinum electrodes. Advantageously, the first and second electrodes (20A) and (20B) may be carbon electrodes. The advantage of using carbon electrodes is that they allow the filtration system according to the present invention to operate at very low voltages (as low as 1-2 V).

[0140] Electrodes 20A and 20B can be partially or completely immersed in electrolyte solutions 11A and 11B, respectively. Electrodes 20A and / or 20B can also be provided so that they can be formed as at least a portion of the walls of containers 10A and / or 10B. Both of these electrodes 20A and 20B are connected to a power source 40, which allows for the generation of an electric field between the electrodes. The electrodes can be connected to the power source 40 via a simple cable.

[0141] Electrical energy source elements (40) In the systems and processes according to the present invention, the electrical energy source element 40 can be any suitable power source known in the art, such as a power generator, a battery, a solar panel, or any other form of power source. In the present disclosure, the purpose of the energy source element 40 is to generate an electric field between the electrodes 20A and 20B. In that regard, the electrodes 20A and 20B connected to the energy source element 40 is not used to collect the ionic current generated by the membrane element (eg, by diffusiosmotic effects).

[0142] Advantageously, the electrical energy source element (40) may include one or more batteries. Thus, the reverse electroosmosis filtration system according to the present invention may be a portable / mobile system. For example, the electrical energy source element (40) may be configured to be charged by light, and in particular, the electrical energy source element may comprise a solar cell or a photodiode.

[0143] Advantageously, the electrical energy source element (40) may be configured to be charged by using the reverse electroosmosis effect to pump an electrolyte solution through the reverse osmosis membrane element (30).

[0144] To that effect, the electrical energy source element (40) may comprise a water turbine element operably connected to the reverse electroosmosis membrane element (30).

[0145] Flow Control (50) The reverse electromotive flux through a composite or hybrid membrane element according to the present invention can be controlled using different parameters.

[0146] (i) Surface charge of the nanoporous membrane: The flux across the membrane element can be increased if the membrane has a higher surface charge. The surface charge can be adjusted by the choice of material, any chemical modifications that may be applied to modify the membrane surface charge, and the pH of the electrolyte solution in contact with the membrane surface bearing the surface charge. Advantageously, a minimum surface charge is preferred, with a |Zeta potential| of ≥ 5 mV, more preferably ≥ 20 mV, and most preferably ≥ 50 mV. The membrane surface charge can be adjusted based on the choice of material constituting the membrane and / or the ionic strength / concentration of the electrolyte solution in contact with the membrane, as described above. (ii) Pore size: For semipermeable membranes (eg, when composite membranes are used), the pore size necessarily depends on the size and / or chemical properties of the solutes to be filtered / separated. Regarding the nanoporous membrane element (which fulfills the "pumping function" in the system), there are no specific restrictions on the pore size, unless the nanoporous membrane element also serves as a size-exclusion semipermeable membrane (e.g., in the case of the hybrid membrane element described herein, the average pore size of the nanoporous membrane should be adapted to the size of the solutes to be separated / filtered). In other words, electroosmosis is not or hardly dependent on the pore size of the nanoporous membrane element. The pore size of the nanoporous membrane simply needs to be sufficient to induce electroosmotic flow of the polar solvent through the membrane. This applies to variations in which composite membranes are used, as well as variations in which hybrid membranes are used (i.e., when dual semipermeable / nanoporous membrane elements such as those in Figure 2 are used). Advantageously, the average pore size of the nanoporous membrane element (which fulfills the function of electrically inducing the flow of polar solvents in the system) can be <500 nm, preferably <300 nm, more preferably <100 nm, and most preferably <50 nm. In a preferred variation, the filtration system is intended for ultrafiltration, and the average pore size of the nanoporous membrane element can be 1 to 50 nm. (iii) Pore Shape: In general, semipermeable membranes do not need to have well-defined pore shapes (e.g., they can be "spaghetti"-like). There are no specific constraints on pore geometry for the nanoporous membrane element: the system will function with any pore shape (provided the nanoporous membrane material has a suitable surface charge, as further detailed herein), ranging from materials with symmetrical pore shapes (e.g., anodized aluminum characterized by cylindrical pores) to materials with highly tortuous porosity (e.g., polycarbonate). For example, nanotubular morphologies of porosity, i.e., cylindrical pores with circular cross-sections, conical asymmetric pore shapes, honeycomb pore shapes, hourglass porosity, etc., can be used. Electroosmotic flow across a nanoporous membrane can be optimized by adjusting the membrane's pore shape. This can be achieved empirically by modifying the pore shape of a given nanoporous membrane using methods well known in the art. In general, flow rates can be optimized when the membrane pore geometry is preferably symmetrical, with little or no tortuosity. Thus, a nanotubular morphology, i.e., a circular cross section, has the effect of increasing the flow rate across the membrane, as opposed to, for example, a conical asymmetric pore geometry. (iv) Electric Field Strength: For a given nanoporous membrane (32) in a system according to the present invention and membrane surface area exposed to the electrolyte solution, the flux increases as the current (i.e., electric field) applied between the electrodes increases (see, e.g., Figures 4B and 12). The choice of applied current depends in part on the filtration application (microfiltration (50-500 nm), ultrafiltration (1-50 nm), or nanofiltration (≦1 nm)). The strength and electric field are selected to maximize the flux. It also depends on the number of pores through which electroosmotic flow can be induced, i.e., the surface area of ​​the nanoporous membrane in contact with the electrolyte solution and the surface pore density of the nanoporous membrane. Typically, for given conditions, such as the pH concentration in the electrolyte solution, a flux vs. strength (or current) curve is plotted to determine the optimal range of electric field strength. For ultrafiltration purposes, the applied current is preferably in the range of 0.5 mA to 20 mA, e.g., 0.5 mA to 15 mA, 0.5 mA to 10 mA, preferably 0.5 mA to 5 mA, more preferably 0.5 mA to 2 mA, depending on the size of the membrane. The electric field strength is preferably adapted depending on the electrodes and / or membrane used. Care should be taken to ensure that there are no secondary reduction / oxidation reactions that could damage the electrodes and / or membrane. For example, if platinum electrodes are used, there is no limit to the voltage that can be applied (the electrodes can withstand any voltage); rather, the voltage limit is the voltage threshold at which electrolysis of the solvent begins (for example, if water is used as the solvent, the applied voltage should not exceed 5 V to avoid water electrolysis). Conversely, if an Ag / AgCl electrode is used, the applied voltage must not exceed 1 V to avoid secondary reduction / oxidation reactions at the electrode level (in this case, it is the nature of the electrode that limits the applied voltage). (V) Ionic strength / concentration of the electrolyte solution: The flow rate is inversely proportional to the salt concentration in the electrolyte solution (see, for example, Figure 4B and Figure 12). The choice of salt concentration in the electrolyte solution depends 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.

[0147] In summary, we have developed a filtration method based on the application of an electric field using a composite membrane with a significant surface charge and a nanometer average pore size (<500 nm). When the membrane separates two reservoirs / containers containing water (or other polar solvents) and a mobile electrolyte (e.g., salt), applying an electric field between the two reservoirs / containers of the cell generates electroosmotic flow (the movement of water / solvent from one cell to the other in the opposite direction to normal osmotic flow). Herein, we demonstrate that this reverse osmotic flow can be used for filtration / purification applications by the unexpected combination of a nanoporous membrane with a surface charge and a selective membrane. Thus, electrolyte-charged water can be used as a separation vector for uncharged molecules (e.g., hormones, dyes, drugs). There is no need for a difference in electrolyte concentration between the two reservoirs / containers of the cell, nor is there a need for a pressure difference to achieve flow. This flow can be controlled by different parameters, such as the membrane's surface charge, the pore diameter and their shape (tortuosity, asymmetricity, etc.), and the electric field.

[0148] As mentioned above, the scarcity of potable water resources is a major international concern. Meanwhile, waste from certain industries, especially the pharmaceutical and chemical industries, poses significant problems for treatment plants. Meanwhile, some arid countries make extensive use of reverse osmosis desalination processes to obtain potable water. However, the energy costs of these processes significantly increase the price of water and capital investment.

[0149] Electric field filtration allows the application of high pressures in conventional water treatment processes. For example, desalination requires the application of pressures exceeding the osmotic pressure (>30 bar). Implementing these processes is expensive and complex. The application of electric fields reduces water treatment costs, even for larger molecules that are often difficult to remove (hormones, drugs, etc.). Combining this filtration method with the use of 2D nanomaterials (e.g., graphene oxide or boron nitride) also allows for implementation with thinner membranes, thus improving permeability for the same selectivity.

[0150] The present invention reduces the implementation of the use of electric fields to induce separation and filtration, as opposed to standard methods (typically of the reverse osmosis type) that rely on mechanical forces due to pressure differences. Thus, the present invention provides a filtration method based on the application of an electric field rather than on concentration differences (such as direct osmosis) or pressure differences (such as reverse osmosis). This offers significant economic advantages: cheaper equipment, cheaper application of electrical power than pressure, and a process that avoids mechanical stress (which, although not applicable here, typically involves pressures of up to 50 bar on membranes). It also has significant ecological advantages, since it can provide an upstream solution for the filtration of complex molecules that are removed in purification plants. For example, an electric field filtration system according to the present invention can be installed in pharmaceutical or textile factories for the pretreatment of wastewater.

[0151] Thus, the present invention provides a highly valuable alternative to filtration / purification and water treatment processes that overcomes the shortcomings of existing processes.

[0152] equivalent The following representative examples, together with the accompanying drawings, are intended to help illustrate the invention and are not intended to, nor are they required to, limit the scope of the invention. Indeed, various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of the specification, including the examples set forth in accordance with and with reference to the scientific and patent literature cited herein.

[0153] It should further be understood that the contents of the cited references are incorporated herein by reference to help illustrate the art.

[0154] The following examples contain important additional information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and the equivalents thereof. [Example]

[0155] The processes and systems according to the present invention and their simplification to implementation can be further understood by examples showing how some of the processes can be carried out. However, it will be understood that these examples should not be construed as limiting the invention. Variations of the invention, now known or further developed, are considered to be within the scope of the invention, as described herein and as claimed below.

[0156] Abbreviation GO: graphene oxide PC: Polycarbonate PMMA: Methyl polymethacrylate

[0157] Materials and Methods Commercially available graphene oxide aqueous dispersion with a concentration of 0.4 wt% was purchased from Graphenea SA. Polycarbonate track-etched membranes were supplied by Sterlitech Corporation. Potassium chloride (>99%), tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (99.95%), and testosterone (>99.9%) were purchased from Sigma-Aldrich. All experiments were performed at room temperature (25±3°C) and neutral pH.

[0158] Example 1 - Preparation and characterization of composite membranes GO / PC membranes were prepared by vacuum filtration. In a typical preparation, a dilute dispersion of graphene oxide (GO) was first prepared by centrifuging a commercial dispersion provided by Graphenea SA at low speed (2000 rpm, ALLEGRA 64-R). The precipitated solid was discarded, typically for four cycles, until the density of the dispersion was adjusted to 1.003 mg L. Then, 1.5 mL of this suspension was diluted with MiliQ® water (obtained with an advantage A10 system (Millipore)) to a total volume of 15 mL. This diluted GO dispersion was added dropwise to the top of a 25 mm polycarbonate (PC) substrate disk (Nuclepore Track-Etch Membrane, 25 mm, 0.1 μm) with a thickness of 24 ± 1 μm and a porosity of 4.7% provided by 100 nm track-etched pores, placed on a Buchner funnel, sealed at one end, and connected to a vacuum pump at the other end. When the incubation was complete, typically less than 16 h, the composite GO / PC membrane disc was split into two pieces: one fraction was inserted into the purification device, and the other was kept for characterization.

[0159] The surface charge of the PC film was measured using the conductance equation [1] and found to be approximately 0.2 mC / m 2 It was determined that.

[0160] The pore size of the GO membrane was measured using XRD and determined to be an average of 0.8 nanometers (average interlayer distance between stacked GO flakes). The XRD pattern revealed a wide distribution of interlayer distances (0.7–1.4 nm).

[0161] Materials characterization The surface morphology of the GO / PC membrane was observed by optical microscopy in transmission mode and field-emission scanning electron microscopy (FE-SEM) on a Thermo-Fischer™ Quattro S instrument (Figure 4C). The cross-section of the GO layer was observed after tilting the sample holder by 90°. X-ray diffraction patterns of the membrane were collected in refraction mode using a powder XRD diffractometer (Bruker®) (Figure 4D). Nitrogen adsorption / desorption isotherms at 77 K were collected on a TRIFLEX micrometries® volumetric instrument. The average interlayer spacing of the GO membrane in the GO / PC membrane was determined by applying Bragg's law to the 001 peak of the recorded diffraction pattern, while the pore size distribution of the membrane and its specific surface area were determined by applying the DFT model and the BET equation, respectively, to the typical nitrogen adsorption isotherm.

[0162] Example 2 - Filtration of dye complex Evaluation of the electroosmotic purification system according to the present invention was carried out using a custom electrokinetic device (Fig. 1) in which the composite GO / PC membrane prepared according to Example 1 separated two 6 mL reservoirs. During flow rate determination, each reservoir (10A) and (10B) was filled with a salt (KCl) of the same concentration as the aqueous solution. For rejection experiments, 1-200 μM tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (99.95%) (Ru-bypi) was added to reservoir (10A) as the test contaminant.

[0163] One Pt electrode (Sigma-Aldrich) was placed in each reservoir (10A) and (10B) and wired to a Keithley 2410 source meter to ensure a constant voltage between -1 and 1 mA.

[0164] A PMMA disk with a 0.5 cm diameter circular hole in the center was attached to the gap between the two reservoirs. To this end, adhesive (Staycast 1266, Aldrich) was spread around the GO / PC composite film, leaving the center of the PMMA disk open facing the hole. After the adhesive cured (typically for 24 h), the PMMA disk with the GO / PC composite film covering the hole was placed between the reservoirs, placed on each O-ring, and then compressed to mechanically seal.

[0165] After closing the electrical circuit, the flow rate from reservoir (10A) to reservoir (10B) was measured by connecting the reservoir outlet pipe to a flow meter consisting of a millimeter-calibrated capillary. Briefly, each reservoir was independently connected to a flow meter (a glass capillary of known diameter with a ruler attached to the side so that the volume could be measured). Quantitative measurements of Ru(bypi) were performed using a nanodrop (Thermo Fisher Scientific) UV-Vis spectrometer. External calibration curves and removal measurements for the device were performed by preparing 0.5 μM to 100 μM Ru(bypi) solutions and determining their absorbance at 283 nm.

[0166] Example 3 - Hormone filtration Example 2 was repeated using 10 mg mL-1 testosterone as the contaminant instead of Ru(bypi) dye.

[0167] Quantitative measurement of testosterone was performed using a UV-Vis nanodrop (Thermo Fisher Scientific) instrument. External calibration curves and elimination measurements were performed by preparing 0.9 μM to 9 μM testosterone solutions and determining their absorbance at 283 nm (see Figure 5A).

[0168] Results and Discussion Throughout the above examples, ultrafiltration processes and systems have been achieved through thin composite semipermeable membranes (~8-9 μm) composed of graphene oxide (semipermeable membrane) combined with polycarbonate nanoporous membranes exhibiting a suitable surface charge, where flow is achieved by applying low-energy electrical power. The examples illustrate an experimental setup consisting of two reservoirs (10A) and (10B) separated by a composite membrane according to the present invention, where a voltage drop can be applied across the membrane. The system was first tested for flux and rejection using a probe molecule to optimize operating conditions and finally using testosterone hormone, a substance that often contaminates drinking water.

[0169] Without wishing to be bound by any particular theory, it is proposed that electroosmotic flow of water is generated within the nanopores of the PC membrane due to the Debye layer formed in intimate contact with the charged surface of the PC material under voltage drop. The overall asymmetry of membranes made from nanoporous materials that exhibit surface charge [2] results in an asymmetric response of water flow versus voltage drop. The water flow rate is given by: Q=Qosm+Qs * (exp(V / V0)-1) (Equation 2) In the formula, Qosm=K_hydro * kT Dc * 2 is the osmotic contribution to the flux, and the second term comes from the rectified electroosmotic flow in the asymmetric membrane. Q is the saturation value of the flux and depends on the properties of the membrane pores.

[0170] The semipermeability of the GO membrane means that it cannot transport ions, allowing only water to pass through the GO / PC membrane, while the high layer-by-layer cohesion of the GO membrane provides high selectivity during the purification process.

[0171] First, we calculated the water flow through the asymmetric membrane at a voltage drop (AV) (Figure 7). Interestingly, for ΔV > 0, the flow increases exponentially with the voltage drop, overcoming the osmotic contribution to the flow. This indicates that the osmotic flow rate can be offset beyond a threshold voltage. In this situation, flow can be generated from the positive electrode to the negative electrode of the membrane.

[0172] At this stage, it is particularly worth noting that the above shows that the characteristic voltage in Equation 2 is fixed by ΔV 0 .

[0173] Next, we constructed a simple, measurable device that can operate under the premise of utilizing the phenomenon of water purification from incoming pollutants that are harmful to the environment and human health. This device consists of two reservoirs (10A) and (10B) separated by the semipermeable GO / PC membrane prepared in Example 1. Each reservoir was further filled with a solution of water and salt (KCl), and then connected to a power source via two platinum electrodes (Figure 4A). A permselective graphene oxide layer on top of the polycarbonate membrane was formed by layer-by-layer stacking of GO flakes through pressure difference and water permeation. The prepared GO / PC membrane was suitable for purification because no cracks were detected over long distances (Figure 8). FE-SEM images of the membrane surface (Figure 4C) confirmed the previously observed cohesive nature, while a cross-section of the membrane revealed a dense mesostructure with a thickness of approximately 9 μm. (Figure 4C).

[0174] This film exhibits an average interlayer distance of 0.8 nm as derived from the PXRD diagram (Figure 4D), which is in good agreement with previously reported GO films prepared in the presence of water. The broad peak recorded in the diffractogram indicates a wide distribution of interlayer distances (0.7–1.4 nm). [2] The presence of the PC substrate is also confirmed in the diffractogram, corresponding to a second diffraction peak centered at 17°. [3] Further analysis of the average pore size of the GO layers in the composite film in the absence of the PC substrate revealed a value of 18 nm. 2 g- 1 The apparent surface area of ​​GO films prepared according to a similar method was revealed (Fig. 9), which is consistent with previously reported GO films prepared according to a similar method [4]. The pore size distribution of the GO layer was also determined from collected nitrogen adsorption isotherm data, and showed a broad distribution ranging from 1.8 nm to 6 nm (Fig. 10). In addition, the isotherm tended to plateau at approximately 0.6 P / P (Fig. 11), indicating the absence of large pores in the film.

[0175] After matching the GO membrane, the GO / PC membrane was placed between the reservoirs of the system. The contents of reservoir (10A) contacted the GO side of the composite GO / PC membrane, while the contents of reservoir (10B) contacted the PC side of the composite GO / PC membrane. The electrokinetic cell was mechanically closed, and several experiments were performed to demonstrate the feasibility of this phenomenon and its intended applications.

[0176] Each reservoir was independently filled with 6 mL of water to first confirm the absence of leaks in the system and then to confirm the stasis of flow when no electrical driving force was applied (Figure 12). Voltage was then applied to the electrodes by fixing it at 1 A. As expected, after 2 hours, no change in the system was detected, as the driving force was provided solely by the movement of ions that counteracted the GO surface charge close to the surface. [5]

[0177] When a second agent capable of generating an ionic imbalance was included (100 μM KCl), water flux was detected after application of a driving force (Figure 5A). The boundary condition for this phenomenon was estimated as ΔV = 0, as predicted by our theoretical model. We then estimated the resulting flux at different salt concentrations and applied intensities by using a GO / PC membrane (Figure 5B) or bare PC substrate (Figure 13) as the reservoir separation membrane. Figure 5B reveals a clear trend of increasing flux throughout the system as the salt concentration decreases. This is observable for both bare PC and GO / PC over a salt concentration range of 100 mM to 1 mM and intensities of 1 mA to 0.5 mA. Therefore, we fixed the operable condition at 1 mM KCl. The use of thin films is preferable from a cost perspective because no additional pressure is required to drive flux across the membrane, and the amount of starting material required is small.

[0178] Variable intensities ranging from -1 to 1 A were applied to the electrodes (Figure 5C). Water flow ranged from no flow to 1.3 mLs. -1Up to ΔV, the applied intensity exponentially correlates with a threshold value, below which there is no flow, again in good agreement with the model predictions. Interestingly, the negative nature of the GO surface is also countered by the absence of this flow when ΔV<0. Under these conditions, no interphases close to the surface form, and as a result, flow is not promoted. Note also that measurements performed by keeping the same membrane and changing the feed solution or switching to a new one yielded no change in flow, demonstrating the membrane's resilience to the process. After establishing the fundamentals of the phenomenon, we monetized the interphase voltage drop during the process (Figure 5D). The obtained values ​​suggest a low-energy process comparable to pressure-driven processes. Without further optimization, lab-scale values ​​can be extrapolated, and considering the linear correlation, 1 m 2 At this membrane window, the flux across the membrane is estimated to be in excess of 238 L / hr.

[0179] In Figure 5, the electrokinetic response of the composite membrane under electric force is shown. The GO / PC membrane was subjected to water and 10 The membrane is placed between two macroscopic reservoirs filled with 0 mM KCl solution. Initially, a constant voltage drop is applied to the electrodes, and the induced ionic current is recorded. As evidenced by Figure 5A, the system required a relatively long time to stabilize at the equilibrium value. After approximately 2 h of a constant potential of 4 V, a constant current of ~2 mA is measured. Only when such a constant current regime is achieved is the membrane considered to be in equilibrium on all sides of the solution-filled GO membrane. The salt concentration is then reduced to Cs = 1 mM, a realistic condition in freshwater. Figure 5E shows the voltage-current plot recorded in this study to fully characterize the membrane response. This plot shows a clear asymmetric response, with positive currents resulting in a larger voltage than negative currents of equal magnitude. Such asymmetric responses are common in nanofluidic systems that exhibit geometric or charge asymmetry. In the system under study, we speculate that the asymmetry arises from the charge contrast between the neutral GO and the negatively charged polycarbonate. Most importantly, the measurements confirmed the presence of surface charges at the fluid-solid interface, a form of surface conduction essential for electroosmotic flow. Finally, in Figure 5F, we demonstrate water flow through the membrane induced by an electric force. Water flow as a function of current strength is shown for different salt concentrations, from 1 to 100 mM Cs. The induced flow is linear with respect to current and strongly dependent on salt concentration, with lower concentrations resulting in greater electroosmotic flow. The electroosmotic rate can be quantified by the following equation:

[0180]

number

[0181] Illustration of an apparatus for purification under electroosmotic conditions Under these conditions, only water molecules flow when a voltage drop is applied, while the layer-to-layer stacking of the GO membrane acts as a molecular sieve for molecules exceeding the hydrodynamic diameter of the membrane's average pore size, providing the membrane's selectivity. While the PC membrane acts as the engine for water flow, the thin-layered GO acts as a selective filter. GO, with its perfect 2D flake stacking, presents a highly ordered structure with an interlayer distance of -0.8 nm, which can be further reduced in the presence of water. Any particles in the fluid larger than this critical distance cannot pass through the composite membrane.

[0182] In the removal experiments, a small molecule (Ru-bip) with an expected hydrodynamic radius of 0.6 nm was detected. y) was chosen. [6] The removal rate of molecules was determined after 2 hours of electroosmosis process (Equation 3, Figure 14). Removal = 1-(Cperm / Cfeed) (Equation 3) where Cperm represents the concentration of the solute in the permeate and Cfeed represents the concentration of the solute in the feed solution (the electrolyte solution being filtered using the system).

[0183] In the first assay, Ru-bipy filtration was performed at a feed rate (Ru-bipy concentration) of 9 μM and a constant power of 1 mA. The elution phase only presents Ru(bypi) at a concentration of 0.9 μM, corresponding to a 90% removal rate (Figure 6A). This experiment already demonstrates the use of the system according to the present invention to purify water containing small molecules under reverse electroosmosis conditions.

[0184] Complete removal assay The applied power was reduced to 0.5 mA, thereby reducing the applied driving force and, consequently, the probability of molecules passing through the GO membrane nanodefects. Under these conditions, complete removal was obtained with concentrations of Ru-bipy up to 150 μM, with the removal ratio decreasing to 0.99 and finally to 0.84 when a 200 μM Ru-bipy solution was used (Figure 6B). This complete removal can be achieved under low-energy conditions.

[0185] Hormone removal Under low energy cost conditions (0.32 kWh / m 3After demonstrating with a probe molecule that complete removal can be obtained with a concentration of 10 mg / mL, the reservoir was then supplied with an aqueous solution of the hormone testosterone (10 mg / mL). This hormone selection is particularly interesting because it exceeds the values ​​commonly present in water. This molecule, commonly present in some water sources, is difficult to detect and filter due to its small hydrodynamic radius. An aqueous solution of the hormone testosterone (10 mg / mL) was then supplied to the reservoir (10A) containing the electrolyte solution in contact with the GO side of the composite GO / PC membrane. mL), which represents a concentration more than 100 times higher than would be expected in a real water sample. [7] This molecule, commonly present in some water sources, is difficult to detect and filter due to its low proportion. Optimized conditions were applied (for the membrane used in the examples, the applied intensity was reduced to 0.5 mA and the membrane was filtered to ∼78 mm 2 The surface area of ​​the disk corresponds to the surface of the gap between the two reservoirs (10A) and (10B), the diameter of the disk is 0.5 cm, and we confirmed the retention of approximately 75% of the hormones present in the feed solution (Figure 6C), demonstrating the great potential of this new method for water purification.

[0186] In summary, a reverse electro-osmosis water purification device has been developed, consisting of a feed reservoir (10A), a semipermeable graphene oxide-based membrane, an elution reservoir (10B), and two electrodes that induce a voltage drop between the two faces of the membrane. This device is capable of achieving a water flux of 4.7 mL / h. Voltage-induced reverse electro-osmosis purification performed by the GO-based membrane results in liquid flow across a threshold voltage, which corresponds to a flux per bar at 40 V, operating at 0.5 mA, or 0.32 kWh / m. 3The GO-based membrane was optimized for complete removal of small molecules of 0.6 nm in terms of energy consumption. Given their small size and the expected linear extrapolation of this phenomenon, larger membrane sections could be used to increase fluxes comparable to traditional filtration methods, but with the benefit of the high selectivity of the inventive method. Reverse electroosmosis purification performed with GO-based membranes was optimized for energy consumption and removal rate, estimating a threshold voltage V > 0 for flow and complete removal of a test molecule (Ru-bipy) with a hydrodynamic radius of 0.6 nm when 0.5 mA is applied.

[0187] Finally, the common levels of hormones (testosterone) currently found in drinking water The device has also been tested for filtration applications, with high retention rates (75%) estimated without any noticeable loss of detected flow.

[0188] List of References 1. Bocquet, L. & Charlaix, E. Nanofluidics, from bulk to interfaces. Chem. Soc. Rev., 2010, 39, 1073-1095. 2. Zhang et al. JACS, 2015, 137, 46, 14765-14772. 3.Vijayalakkshmi et at.International Journal of Polymer Science,2011,1687. 4.Wei etal.International journal of hydrogen energy,2016,41,11692-11699 5. Kirby, 2009, Cambridge University press. Micro-nanoscale fluid mechanics: Transport in microfluidic devices. 6. Joshi et al. Science, 2014, 343, 752-754. 7.US geological survey (USGS),2008,www.epa.gov 8.A.Siria,P.Poncharal,A.-L.Biance,R.Fulcrand,X.Blase,S.Purcell,L.Bocquet,”Giant osmotic energy conversion measured in a single transmembrane boron- nitride nanotube” Nature 494455-458 (2013)

Claims

1. 1. A reverse electroosmosis filtration system comprising: a) a first container (10A) intended to receive a first electrolyte solution (11A) enriched in a solute of interest, the first container comprising a first electrode (20A) in contact with the first electrolyte solution (11A) contained in the first container (10A); b) a second container (10B) intended to receive a second electrolyte solution (11B) that does not contain or is depleted of the same solute of interest, said second container comprising a second electrode (20B) in contact with said second electrolyte solution (11B) contained in said second container (10B), said first electrolyte solution (11A) containing a higher concentration of solute than said second electrolyte solution (11B) or in which ≥ 99% of said solute of interest has been removed in said second electrolyte solution (11B) intended to be received in said second container (10B) compared to said first electrolyte solution (11A); c) a reverse osmosis membrane element (30) separating the first and second vessels, (i) a semipermeable membrane element (31), and (ii) a nanoporous membrane element (32) having a surface charge of |Zeta potential| ≥ 5 mV as measured using an electrokinetic analyzer, in combination with a nanoporous membrane having an average pore size of < 1 μm as measured according to the ISO 15901 standard; The semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two are different elements of the semipermeable membrane element (31) is configured to be in contact with the first electrolyte solution (11A) in the first container (10A), and the reverse osmosis membrane element (30) fulfills both the functions of (i) solute filtration and (ii) electrically conducting a solvent flow of the first electrolyte solution (11A) from the first container (10A) to the second container (10B) through the reverse osmosis membrane element (30); the first electrolyte solution (11A) and the second electrolyte solution (11B) in the first container (10A) and the second container (10B), respectively, contain the same polar solvent, the polar solvent comprising an aprotic solvent having a dielectric constant of ≧6 and a dipole moment of ≧1.50 D, and a protic solvent; the first electrode (20A) and the second electrode (20B) are operably connected to a source of electrical energy (40); The reverse electroosmosis filtration system is configured to apply an electric field between the first electrode (20A) and the second electrode (20B) to induce a reverse osmosis flow of the polar solvent of the first electrolyte solution (11A) from the first vessel (10A) to the second vessel (10B) through the reverse osmosis membrane element (30).

2. 2. The reverse electroosmosis filtration system of claim 1, wherein the semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two different elements combined together to form a two-layer composite asymmetric membrane (30A), the composite asymmetric membrane (30A) comprising a semipermeable membrane element (31) superimposed with a charged nanoporous membrane element (32) having a surface charge with a |zeta potential| of ≧5 mV.

3. 3. The reverse electroosmosis filtration system of claim 2, wherein the semipermeable membrane element (31) is a semipermeable membrane based on separation by chemical affinity, a size exclusion membrane, or an ion exchange membrane.

4. 4. The reverse electroosmosis filtration system of claim 3, wherein the semipermeable membrane element (31) is a size-exclusion selective membrane composed of stacked graphene oxide flakes.

5. The nanoporous membrane element (32) having a surface charge has an average pore size of <500 nm and is TiO ２ , boron nitride, SiO ２ , polyethersulfone, polycarbonate, anodized aluminum, hydrotalcite, Ni-Fe layered double hydroxide, Ni ２ dobdc, Mg ２ 3. The reverse electroosmosis filtration system of claim 2, made of a material selected from dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, polyelectrolyte layer polymer membranes, and nanoporous membranes obtained by successive dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) on a polycarbonate membrane.

6. 5. The reverse electroosmosis filtration system of claim 2 or 4, wherein the surface of the charged nanoporous membrane element (32) is chemically modified to enhance the surface charge of the nanoporous membrane.

7. The reverse electroosmosis filtration system of claim 6 , wherein the chemical modification is provided on the surface of the pore walls of the nanoporous membrane.

8. 8. The reverse electroosmosis filtration system of any one of claims 5 to 7, wherein the charged nanoporous membrane element (32) is obtained from a polycarbonate membrane with an average pore size of <500 nm, the internal pore walls of which have been chemically modified by dip-coating the polycarbonate membrane in an aqueous solution of polydopamine.

9. The electrical energy source (40) according to any one of claims 1 to 8, wherein the electrical energy source (40) is a battery. Reverse electroosmosis filtration system.

10. 10. The reverse electroosmosis filtration system of claim 9, wherein the electrical energy source (40) is configured to be charged by one of light or by using the reverse electroosmosis effect to pump an electrolyte solution through the reverse osmosis membrane element (30).

11. A reverse electroosmosis filtration system as described in claim 10, wherein the electrical energy source (40) comprises a solar cell or a photodiode and is configured to be charged by light.

12. A reverse electroosmosis filtration system as described in claim 10, wherein the electrical energy source (40) is configured to be charged by use of the reverse electroosmosis effect to pump an electrolyte solution through the reverse osmosis membrane element (30), and the electrical energy source (40) comprises a hydraulic turbine element operably connected to the reverse osmosis membrane element (30).

13. 1. A process for purifying an electrolyte solution in a polar solvent, comprising: i) providing a first electrolyte solution (11A) comprising a solute in a polar solvent, the polar solvent comprising an aprotic solvent having a dielectric constant of ≧6 and a dipole moment of ≧1.50 D, and a protic solvent; ii) providing a second electrolyte solution (11B) free of said solute in the same or different polar solvent as in step i); iii) providing a reverse electroosmosis filtration system, said reverse electroosmosis filtration system comprising: a) a first container (10A) equipped with a first electrode (20A); b) a second vessel (10B) comprising a second electrode (20B), said first electrode (20A) and said second electrode (20B) being operably coupled to a source of electrical energy (40); c) a reverse osmosis membrane element (30) separating the first vessel (10A) and the second vessel (10B), (i) a semipermeable membrane element (31), and (ii) a nanoporous membrane element (32) having a surface charge of |Zeta potential| ≥ 5 mV as measured using an electrokinetic analyzer, in combination with a nanoporous membrane having an average pore size of < 1 μm as measured according to the ISO 15901 standard; The semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two different elements, a reverse osmosis membrane element, wherein the semipermeable membrane element (31) is in contact with the first electrolyte solution (11A) in the first container (10A), and the nanoporous membrane element (32) having a surface charge is in contact with the second electrolyte solution (11B) in the second container (10B); the reverse osmosis membrane element (30) fulfills both the functions of (i) solute filtration and (ii) electrically conducting a solvent flow of the first electrolyte solution (11A) from the first vessel (10A) to the second vessel (10B) through the reverse osmosis membrane element (30); the reverse osmosis membrane element (30) is adapted to selectively block diffusion of the solute through the reverse osmosis membrane element (30); iv) placing the first electrolyte solution (11A) to be purified in the first container (10A) so that the first electrode (20A) provided therein is in contact with the first electrolyte solution (11A); v) placing a sufficient amount of the second electrolyte solution (11B) in the second container (10B) so that the second electrode (20B) provided therein is in contact with the second electrolyte solution (11B); vi) applying an electric field between the first electrode (20A) and the second electrode (20B); directing a reverse osmosis flow of the polar solvent from the first vessel (10A) to the second vessel (10B) through the reverse osmosis membrane element (30) separating the first vessel (10A) and the second vessel (10B), thereby allowing the solvent to flow from the first container (10A) towards the second container (10B) while retaining the solute within the first container (10A); vii) recovering the purified second electrolyte solution (11B) from the second vessel (10B) that is free or depleted of solutes, wherein the first electrolyte solution (11A) contains a higher concentration of solutes than the second electrolyte solution (11B) or ≧99% of the solutes are retained in the first electrolyte solution (11A).

14. 14. The process of claim 13, wherein the polar solvent is a solvent capable of generating acidic ions.

15. 14. The process of claim 13, wherein the solute is selected from solid particles, organic or inorganic small molecules, biomolecules, pollutants, metabolic waste products, or salts / ions.

16. A water purification system comprising the reverse electroosmosis filtration system of any one of claims 1 to 8.

17. A saltwater desalination system comprising the reverse electroosmosis filtration system of any one of claims 1 to 15.

18. An implantable artificial kidney comprising the reverse electroosmosis filtration system of any one of claims 1 to 15.

19. 1. A process for desalination of seawater, comprising: i) providing a reverse electroosmosis filtration system, said reverse electroosmosis filtration system comprising: a) a first vessel (10A) containing seawater and provided with a first electrode (20A), said first electrode (20A) being in contact with the seawater contained in said first vessel (10A); b) a second vessel (10B) containing seawater and provided with a second electrode (20B), said second electrode (20B) being in contact with the seawater contained in said second vessel (10B), said first electrode (20A) and said second electrode (20B) being operably connected to a source of electrical energy (40); c) a reverse osmosis membrane element (30) separating the first vessel (10A) and the second vessel (10B), (i) a semipermeable membrane element (31) having an average pore size of <1 nm; and (ii) a nanoporous membrane element (32) having a surface charge of |Zeta potential| ≥ 5 mV as measured using an electrokinetic analyzer, in combination with a nanoporous membrane having an average pore size of < 1 μm as measured according to the ISO 15901 standard; The semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two different elements, a reverse osmosis membrane element, wherein the semipermeable membrane element (31) is in contact with seawater contained in the first container (10A), and the nanoporous membrane element (32) having a surface charge is in contact with water contained in the second container (10B); The reverse osmosis membrane element (30) has the functions of (i) solute filtration, and (ii) directing the flow of water from the first vessel (10A) to the second vessel (10B) through the reverse osmosis membrane element (30). and fulfill the function of electrical induction, The reverse osmosis membrane element (30) is ＋ and Cl － adapted to selectively inhibit diffusion through said reverse osmosis membrane element (30); ii) applying an electric field between the first electrode (20A) and the second electrode (20B) to induce a reverse osmosis flow of water from the first vessel (10A) to the second vessel (10B) through the reverse osmosis membrane element (30) separating the first vessel (10A) and the second vessel (10B); Thereby, while water flows from the first container (10A) to the second container (10B), Na ＋ and Cl － allowing a solute to be retained in said first container (10A); iii) Na ＋ and Cl － Recovering demineralized water from the second vessel (10B) free of solutes, ＋ and Cl － wherein the solute is held in seawater contained in said first vessel (10A).

20. 20. The process of any one of claims 13 to 15 and 19, wherein the semipermeable membrane element (31) and the nanoporous membrane element (32) having a surface charge are two distinct elements combined together to form a two-layer composite asymmetric membrane (30A), the composite asymmetric membrane (30A) comprising a semipermeable membrane element (31) superimposed with a charged nanoporous membrane element (32) having a surface charge with a |zeta potential| of ≥ 5 mV.

21. 21. The process of claim 20, wherein the semipermeable membrane element (31) is a semipermeable membrane based on separation by chemical affinity, a size exclusion membrane, or an ion exchange membrane.

22. 22. The process of claim 21, wherein the semipermeable membrane element (31) is a size-exclusion selective membrane composed of stacked graphene oxide flakes.

23. The nanoporous membrane element (32) having a surface charge has an average pore size of <500 nm and is TiO ２ , boron nitride, SiO ２ , polyethersulfone, polycarbonate, anodized aluminum, hydrotalcite, Ni-Fe layered double hydroxide, Ni ２ dobdc, Mg ２ 21. The process of claim 20, wherein the membrane is made of a material selected from dobdc (dobdc = 1,4-dioxide-2,5-benzenedicarboxylate), cellulose, polyelectrolyte layer polymer membranes, and nanoporous membranes obtained by successive dip-coating layers of cationic polyethyleneimine and anionic poly(acrylic acid) on a polycarbonate membrane.

24. 23. The process of claim 20 or 22, wherein the surface of the charged nanoporous membrane element (32) is chemically modified to enhance the surface charge of the nanoporous membrane.

25. 25. The process of claim 24, wherein the chemical modification is provided to the surface of the pore walls of the nanoporous membrane.

26. 26. The process of any one of claims 23 to 25, wherein the charged nanoporous membrane element (32) is obtained from a polycarbonate membrane with an average pore size of <500 nm, the internal pore walls of which have been chemically modified by dip-coating the polycarbonate membrane in an aqueous polydopamine solution.

27. The process according to any one of claims 19 to 26, wherein the source of electrical energy (40) is a battery.

28. The electrical energy source (40) is a source of light or electrolysis through the reverse osmosis membrane element (30).

28. The process of claim 27, wherein the electrolyte is configured to be charged by one of: a) using a reverse electroosmotic effect to pump the electrolyte solution;

29. The process described in claim 28, wherein the electrical energy source (40) comprises a solar cell or a photodiode and is configured to be charged by light.

30. The process described in claim 28, wherein the electrical energy source (40) is configured to be charged by use of the reverse electroosmosis effect to pump an electrolyte solution through the reverse osmosis membrane element (30), and the electrical energy source (40) comprises a hydraulic turbine element operably connected to the reverse osmosis membrane element (30).

31. The reverse electroosmosis filtration system of any one of claims 1 to 12, wherein the |Zeta potential| is ≧50 mV.

32. 31. The process of any one of claims 13 to 15 and 19 to 30, wherein the |Zeta potential| is ≧50 mV.

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