Membrane and method for selective ion transfer

Abstract

The invention relates to a membrane (10) including: - a porous substrate (30) including two opposite main surfaces (32, 34), - a selective ion transfer layer (20) including sheets (22) of a nanomaterial extending over one of the two main surfaces (32, 34) of the porous substrate, the nanomaterial being of the formula: XMNO14, M being of the formula As3(1-y-z)Sb3yBi3z, and N being of the formula P2kAs2(1-k), y, z and k being numbers ranging from 0 to 1 with y+z less than or equal to 1, X being of the formula H3(1-x)A3x, A being an alkali, an ammonium cation or a cation derived from a water-soluble hydroxide salt or a mixture thereof, x being a number ranging from 0 to 1.

Description

[0001] Description

[0002] Title: Membrane and selective ion transfer process

[0003] The present invention relates to a membrane, in particular for selective ion transfer, and the device comprising such a membrane. It also relates to a method for manufacturing such a membrane and a method for selective ion transfer using such a membrane.

[0004] Technical field

[0005] Membranes play a crucial role in many industrial and scientific processes involving the separation and selective transmission of ions. They are essential in applications such as water purification, energy production, gas separation, electrochemical catalysis, the manufacture of energy storage devices, electronic waste recycling processes, and many others. These membranes act as selective barriers, allowing the selective passage of specific ions while blocking other ionic or molecular species, making them indispensable in a variety of industrial and scientific processes.

[0006] In the state of the art, membranes based on nanomaterials are known in particular, in particular membranes based on:

[0007] - graphene oxide 2 porous for the selective separation of lithium from Li+Co, Li+Ni or Li+Mn mixtures;

[0008] - MXene (TiaCiTx) 3 non-porous with faster permeation of lithium than calcium, magnesium, aluminum and nickel;

[0009] - MOF 4 porous for the selective separation of lithium from a complex mixture containing the following elements Li, Ba, Ni, Cu, Cd, Pb, Al, Cr and Zr.

[0010] These nanomaterials present: (i) either artificial porosity created by drilling or chemical etching, as for porous graphene, with a fairly wide pore size dispersion; (ii) either intrinsic / crystalline porosity as for MOFs, with a very low size dispersion, due to their atomically defined structures; (iii) or no porosity, as for MXenes but a lamellar structure allowing the selective passage of chemical species between the lamellae or sheets. For the first nanomaterials with artificial porosity, the control of dispersity is complicated and the polydispersity of the pore size generates a low selectivity of certain chemical species, in particular ions. Intrinsically porous materials such as MOFs present chemical instability limiting their use and their selectivity of certain chemical species, in particular ions.Lamellar materials without porosity, such as bentonite, do not always have a sufficiently small interlamellar distance to allow sufficient selectivity for certain chemical species, in particular ions.

[0011] Despite significant advances in ion transfer membranes, several challenges remain, particularly regarding selective efficiency, durability, chemical resistance and cost-effectiveness.

[0012] We can note in particular that such known membranes do not allow sufficient selectivity of silver ions in e-waste leaching solutions, especially when there is a real need for such recycling. Indeed, in 2022, the demand for silver was approximately 35,000 tonnes worldwide, constantly increasing compared to 29,000 tonnes in 2014. Silver is often scarce since the supply reached 28,500 tonnes in 2022 (Silver Institute 2023), a quantity well below the demand. The demand for silver comes mainly from its industrial use (50% of the silver market is used for industrial applications, such as solar panels and electronics). Silver is also used for jewelry (21% of the market), as an investment (18% in coins and ingots), for silverware or for photography.Most current photovoltaic (PV) panels are based on crystalline silicon technology. The silver contacts of these PVs require between 14 and 37 g / W of installed photovoltaic capacity. If the technology does not evolve, and given the necessary increase in photovoltaic installations to mitigate the effects of climate change, this application alone would consume between 85 and 98% of known silver reserves. At the same time, forecasts indicate that e-waste production is expected to increase from 53.6 Mt in 2019 to 74.7 Mt in 2030. Of this, less than 20% is recycled. 40,000 tons of PV will reach their end of life in France alone by 2030. Recycling already provides approximately 5,000 tons of silver each year. However, recycling such waste remains complex.Improved e-waste recycling processes that recover silver from e-waste of complex and variable compositions could reduce pressure on silver supply chains while reducing the amount of e-waste going to landfill. One challenge with e-waste recycling is that silver is found in e-waste containing multiple other metals and plastics, and the purity required for silver uses means that silver must be efficiently separated from other compounds. Current recycling practices involve crushing or melting e-waste, dissolving the silver, primarily using nitric acid to ensure the solubility of silver nitrate, separating it, and recovering it in its high-purity metallic form.Silver recovery has been demonstrated using ion exchange resins, solvent extraction, liquid membrane processes or solid membrane processes containing adsorbents, electrodeposition, or precipitation. However, the lack of selectivity of these recovery methods leads to significant co-extraction of ions corresponding to several different metals, thus requiring multiple purification cycles to achieve the desired purity. The use of multiple cycles leads to long, complicated, and expensive processes consuming a large amount of chemicals.

[0013] This situation is not limited to silver; it also applies to other elements present in electronic waste that would be interesting to recycle easily and more efficiently. For example, it is interesting to recycle lithium more efficiently in NMC (Nickel Manganese Cobalt) lithium-ion batteries or lead in lead-acid batteries or to recover several elements independently by different processing steps of a complex initial solution containing said elements in a mixture.

[0014] It is also interesting to improve membranes for the transfer of protons between two solutions to improve the efficiency of fuel cells.

[0015] There is therefore a need to develop new membranes offering improved performance and meeting the specific requirements of the various applications mentioned above, in particular for ion transfer membranes with good transfer efficiency of certain elements of interest from one solution to another, which are easy to manufacture, reusable, inexpensive and simple to use.

[0016] In particular, there is a need for a membrane exhibiting good extraction selectivity of certain ions over others in a complex mixture that is easy to manufacture, reusable, inexpensive, and simple to use while providing good selectivity of target ions.

[0017] In particular, there is a need for a membrane having good selectivity for extracting silver or hydrogen in a complex mixture comprising a plurality of ions, or lithium or lead in a complex mixture including little or no silver and little or no hydrogen.

[0018] Statement of the invention

[0019] The invention meets this need according to a first aspect using a membrane comprising: a porous support comprising two opposite main surfaces, a selective ion transfer layer comprising sheets of a nanomaterial extending over one of the two main surfaces of the porous support, the nanomaterial being of formula:

[0020] XMNO14

[0021] M being of formula As3(i- y -z)Sb3yBi3z,, and N being of formula P2kAs2(ik), y, z and k being numbers varying from 0 to 1, with y+z less than or equal to 1,

[0022] X being of formula H3(i- X )A3X , A being an alkali, an ammonium cation or a cation derived from a water-soluble hydroxide salt or a mixture thereof, x being a number ranging from 0 to 1.

[0023] According to a first embodiment, the subject of the invention is a membrane comprising: a porous support comprising two opposite main surfaces, a selective ion transfer layer comprising sheets of a nanomaterial extending over one of the two main surfaces of the porous support, the nanomaterial being of formula:

[0024] XMP2O14

[0025] M being of formula As3(i- y -z)Sb3yBi3z,, y and z being numbers varying from 0 to 1 with y+z less than or equal to 1,

[0026] X being of formula H3(i- X )A3 X , A being an alkali, an ammonium cation or a cation derived from a water-soluble hydroxide salt or a mixture thereof, x being a number ranging from 0 to 1.

[0027] According to a second embodiment, the subject of the invention is a membrane comprising: a porous support comprising two opposite main surfaces, a selective ion transfer layer comprising sheets of a nanomaterial extending over one of the two main surfaces of the porous support, the nanomaterial being of formula:

[0028] XMNO14

[0029] M being of formula As3(iyz)Sb3yBÎ3z,, and N being of formula P2kAs2(ik), y, z and k being numbers varying from 0 to 1, with y+z less than or equal to 1 and k different from 1,

[0030] X being of formula H3(i- X )A3 X , A being an alkali, an ammonium cation or a cation derived from a water-soluble hydroxide salt or a mixture thereof, x being a number ranging from 0 to 1.

[0031] Such membranes allow high selectivity for certain ions in a complex mixture, making them an ideal choice for a diverse range of industrial and scientific applications. It therefore allows selective ionic transfer of ions through it.

[0032] Such membranes allow in particular the extraction of ions in a leaching solution of electrical and electronic waste, resulting in particular from the treatment of electronic waste such as printed circuits or photovoltaic panels, jewelry, jewelry waste, metal alloys and / or silverware, with a minor co-extraction of impurities, even when the ions to be extracted are present only in small quantities compared to other ions in the mixture. This can allow the easy recovery, for example, of silver ions in such solutions with satisfactory purity for the purpose of silver recovery and new use and this in a reduced number of purification cycles, in particular in a single recovery cycle. They can also make it possible to separate lithium or lead ions from complex aqueous solutions, in particular containing little or no silver ions.They can therefore allow, for example, the extraction of lithium in ionic solutions resulting from the treatment of NMC (Nickel Manganese Cobalt) lithium-ion batteries.

[0033] When used in a fuel cell, for example, they can also serve as a proton transfer membrane between the different compartments of the cell.

[0034] Such membranes are also of interest in other areas of membrane use, at least due to their ease of manufacture and use, their lifespan and their low cost.

[0035] Furthermore, such membranes are reusable after simple washing and retain their selectivity even after several uses. They are therefore stable over time, even after several uses. This helps reduce the overall cost of such membranes.

[0036] Selective ion transfer layer

[0037] Preferably, the selective ion transfer layer has an average surface quantity of nanomaterials greater than or equal to 0.3 mmol / m 2 , better greater than or equal to 0.5 mmol / m 2 , even better greater than or equal to 0.6 mmol / m 2 Such an average surface quantity makes it possible in particular to improve the selectivity of the membrane towards certain ions.

[0038] The nanomaterial sheets are preferably substantially uniformly distributed in the selective ion transfer layer. This improves the selectivity of the membrane.

[0039] Preferably, the sheets extend in the selective ion transfer layer along extension planes substantially parallel or inclined at an angle less than or equal to 45° to the extension plane of the selective ion transfer layer.

[0040] Preferably, the selective ion transfer layer has a thickness in the dry phase at a temperature of 20°C greater than or equal to 10 nm, better still greater than or equal to 15 nm, even better still greater than or equal to 20 nm. Such a thickness can be measured by imaging using a scanning electron microscope with appropriate magnification on a membrane dried at room temperature, in particular dried at room temperature under a hood for several days. Such a thickness makes it possible to have a superposition of several sheets of nanomaterials in the thickness of the selective ion transfer layer, which improves the selectivity of the membrane for the ions to be separated, in particular silver, hydrogen, lithium and / or lead ions.

[0041] The thickness of the selective ion transfer layer is preferably substantially constant across the entire major surface over which it extends.

[0042] The selective ion transfer layer may be uniform over an entire area delimited by a continuous contour of the main surface of the porous support. The area may be of substantially circular, or rectangular, or any other shape, depending on the shape of the membrane manufacturing tool.

[0043] The average inter-layer distance in the dry phase at a temperature of 20°C can be between 0.5 nm and 2 nm, better between 0.8 nm and 1.6 nm. This distance is determined by calculation according to Bragg's law from the peaks of the first-order (00f) planes of a diffractogram obtained by X-ray diffraction.

[0044] The average size of the two-dimensional sheets in the plane of the selective ion transfer layer is preferably larger than the average pore size of the porous support, in particular between 100 and 2500 nm. The average size of the sheets can be determined from images of the nanosheets deposited on a silicon substrate from dilute suspensions, obtained using a scanning electron microscope with appropriate magnification or by atomic force microscopy (AFM).

[0045] Preferably, the surface charge density of the selective ion transfer layer is greater than or equal to 0.25 C / m 2 , better greater than or equal to 0.5 C / m 2 . The surface charge density can be determined by potentiometric titration or calculated from the crystallographic structure of the nanomaterial. Such a surface charge improves the selectivity properties of the membrane.

[0046] Preferably, A is selected from lithium, sodium, potassium, rubidium, cesium, ammonium cations such as tetramethyl, tetraethyl, tetrabutyl or tetrapropyl ammonium, molecular (or ionic) cations existing in the form of a water-soluble hydroxide salt, or a mixture thereof.

[0047] The selective ion transfer layer may comprise more than 25%, better more than 30%, even better more than 50%, preferably more than 80%, even better more than 90%, by mass of nanomaterials.

[0048] The selective transfer layer can be free of binder between the sheets. It can consist of more than 90% nanomaterial sheets.

[0049] Alternatively, the selective transfer layer is a hybrid layer comprising: a polymer, in particular chosen from polyamide, polyimide, polyester, polyamine, polyurethane and polyurea, and the sheets of the nanomaterial in the polymer, the mass proportion of nanomaterial sheets in the selective ion transfer layer being between 25% and 40%. The combination of the polymer layer with the nanomaterials in the selective ion transfer layer can make the membranes more robust and stable, improve the permeability of the solvent, provide resistance to fouling and increase the selectivity of the membrane. Preferably, M, A and the value of x are predetermined according to the species of ions to be extracted and according to the initial solution containing it, in particular according to the other ions present in the initial ionic solution. This allows the use of this type of membrane for many application cases.

[0050] The parameters of the nanomaterial formula can be such that k is different from 0, y is different from 1 and z is different from 0.

[0051] The nanomaterial may be of formula XSbaNOu, in particular of formula XSb3P20i4.

[0052] Alternatively, the nanomaterial may include a non-zero proportion of bismuth as a replacement for antimony, in particular being of formula XSb3 y Bi3(i- y )NOi4, in particular of formula XSb3 y Bi3(i- y )P20i4, with y between 0 and 1 being different from 1.

[0053] Alternatively, the nanomaterial may contain a non-zero proportion of arsenic as a replacement for antimony, in particular being of formula XAs3(i- y )Sb3 y NOi4, in particular of formula XAs3(i- y )Sb3 y P20i4, with y between 0 and 1 being different from 1.

[0054] Alternatively, the nanomaterial may contain a non-zero proportion of bismuth and arsenic replacing antimony according to the formula X3As3(i- y - z )Sb3yBi3zNOi4, in particular of formula X3As3(i- y -z)Sb3 y Bi3zP2Oi4 with y and z between 0 and 1, y different from 1 and z different from 0. Preferably, y is different from 0.

[0055] The parameters y, z and k of the nanomaterial formula, defining the proportions of bismuth and arsenic, can be chosen to allow a predetermined ionic selectivity. Indeed, the inventors have demonstrated that the selectivity is adjustable by adjusting the quantity of bismuth and / or arsenic replacing F in the nanomaterial, these proportions making it possible in particular to vary the size of the pores and the inter-layer distance.

[0056] Support

[0057] The porous support may have an average pore size less than or equal to 10 pm, better still less than or equal to 1 pm, better still less than or equal to 500 nm, even better still less than or equal to 300 nm.

[0058] The porous support can be made of a material compatible with acid solutions, for example polyvinylidene fluoride (PVDF), particularly hydrophilic. PVDF is commonly used as a porous support for composite membranes due to its compatibility with acid solutions, its robustness, its flexibility and its stability. Alternatively, the porous support can be made of polytetrafluoroethylene (PTFE). If resistance to very acidic or very basic pH is not required, any porous substrate can be used because its main role is to provide mechanical strength to the assembly while not preventing the passage of ions.

[0059] Protective layer

[0060] The membrane may include a porous protective layer extending over the selective transfer layer on the side opposite the support. This may limit degradation of the selective ion transfer layer by detachment of the nanomaterial sheets in the solution with which it is in contact.

[0061] Manufacturing process

[0062] The invention also relates, according to a second aspect, to a method for manufacturing the membrane as described above, comprising the vacuum suction of an aqueous solution comprising sheets of the nanomaterial in suspension from a surface of the porous support intended to be covered by the selective transfer layer towards an opposite surface of the support in the porous support.

[0063] With such a process, at least some of the nanomaterial sheets do not pass through the membrane by their size and they are deposited in a layer on the surface of the porous support. They then form a lamellar layer. The lamellar layer thus formed forms the selective ion transfer layer.

[0064] Alternatively, the aqueous solution may further comprise first monomers, the method comprising bringing the layer obtained on the surface of the support into contact with an organic solution comprising second monomers configured to generate a polymerization reaction of the first monomers upon contact to form the selective ion transfer layer.

[0065] The method may comprise, upstream of the passage of the aqueous solution, the immersion of the support in a wetting solution, in particular ethanol, in particular when the support is hydrophobic, for example when it is made of PTFE. Such a wetting solution makes it possible to improve the affinity of the support for water. In this case, the method may comprise the addition to the aqueous solution comprising the nanomaterial sheets of a conditioning solution, in particular identical to the wetting solution, before the mixture is placed under vacuum. Preferably, the method comprises bringing one of the main faces of the support into contact with the mixture for a predetermined non-zero duration, then placing the mixture under vacuum.

[0066] The method may include depositing a porous protective layer on the selective ion transfer layer.

[0067] The process may include drying the resulting membrane.

[0068] The support can be stationary during the manufacturing process. In this case, the process allows for the independent manufacturing of each membrane. Alternatively, the support can be mobile during the manufacturing process. The support can move under the aqueous solution. The manufacturing of the membrane is then continuous.

[0069] Device

[0070] The invention also relates, according to a third aspect, to a device comprising an ion transfer unit comprising a first and a second compartment separated from each other by a membrane as described previously.

[0071] Such a device allows the selective transfer of ions between the two compartments through the membrane. It allows an ionic solution to be treated to be introduced into one of the two compartments and a permeate solution to be introduced into the other compartment so that a selective ionic transfer takes place through the membrane by osmosis. It is then possible to recover a permeate and a retentate having ionic concentrations different from the initial solution, in particular a permeate enriched in certain ions, notably silver, lithium and / or lead.

[0072] Preferably, the ion transfer unit, including the device, is fluid-tight, except through the membrane.

[0073] Preferably, the selective ion transfer layer extends over the entire surface of the membrane separating the two compartments. Preferably, the selective ion transfer layer is substantially uniform over the entire surface. This allows for uniform ion selectivity over the entire surface separating the two compartments, which improves the overall selectivity of the membrane.

[0074] Microfluidic device

[0075] The first and second compartments may be first and second microfluidic circulation chambers facing each other. The first and second microfluidic circulation chambers may each be in the form of a portion of microfluidic conduit, in particular arranged rectilinearly or in the form of a serpentine.

[0076] The first and second microfluidic circulation chambers may each have an inlet and an outlet, with fluid flowing from the inlet to the outlet.

[0077] The device may comprise one or more fluid circulation systems in the first and second compartments, in particular in the first and second microfluidic circulation chambers. The fluid circulation system(s) are configured to circulate fluids continuously or according to a predetermined circulation profile in the first and second compartments, in particular the first and second microfluidic circulation chambers, and / or control their flow rates. The fluid circulation system(s) may be pumps, syringe pumps or any other known fluid circulation system.

[0078] Preferably, the fluid circulation system(s) are configured so that the fluid flows in the first and second compartments, in particular the first and second microfluidic circulation chambers, are tangential to the membrane.

[0079] The ion transfer unit can operate in co-current mode, i.e. with fluid circulations on both sides of the membrane substantially in the same direction and the same sense, or in counter-current mode, i.e. with fluid circulations on both sides of the membrane substantially in the same direction and in opposite senses. Operation in counter-current mode makes it possible in particular to maintain a significant difference in osmotic pressure over the entire exchange zone of the cell and thus to achieve permeation rates of silver or other targeted cations greater than 50%.

[0080] The first and second compartments, in particular the first and second microfluidic circulation chambers, may have contours that are symmetrical to each other relative to the membrane. The first and second compartments, in particular the first and second microfluidic circulation chambers, may be completely symmetrical to each other relative to the membrane. This allows ionic transfer through the membrane over the entire dimension of the fluidic circulation chambers, which may allow this transfer to be optimized. The depth of the first and second compartments, in particular the first and second microfluidic circulation chambers, may be less than or equal to 2 mm, better still less than or equal to 1 mm, even better still less than or equal to 0.2 mm.Such a low depth of circulation chambers makes it possible to limit the resistance due to the diffusion of ions in the two compartments and thus to minimize the time necessary to achieve interesting extraction and selectivity for flow rates of the ionic solution in the corresponding microfluidic circulation chamber, which is conventional in microfluidics, in particular between 1 and 20 pL / min.

[0081] Without excessive effort, a person skilled in the art will be able to adapt such a device to industrial constraints, particularly in terms of dimensions, volumes, topologies, flow rates or quantities of fluids in the first and second compartments.

[0082] Preferably, the support is hydrophobic, such as polytetrafluoroethylene (PTFE). It preferably has a thickness less than or equal to 100 μm, better still less than or equal to 50 μm, even better less than or equal to 30 μm. It may have a porosity greater than or equal to 10%, better still greater than or equal to 50%, even better still greater than or equal to 90%, with a pore size greater than or equal to 10 nm. The greater the porosity of the substrate, the better the flux.

[0083] The device may comprise a plurality of ion transfer units each comprising a first and a second compartment separated from each other by a membrane as described previously, the ion transfer units being connected to each other in series or in parallel.

[0084] Preferably, they are connected together in series, the output of one of the first and second compartments of the upstream transfer units being connected to the input of one of the first and second compartments of the downstream transfer units.

[0085] The device may be configured so that there is fluid continuity between the ion transfer units, the inlets and outlets of the first and / or second compartments being connected to each other without any flow interruption member.

[0086] Preferably, the first compartments are connected together in series. The device may comprise a single fluid circulation system configured to continuously circulate the fluid in the first compartments connected together.

[0087] Preferably, the first compartment of the most upstream ion transfer unit is connected at the inlet to an ion solution supply and the second compartments of the ion transfer units are connected to one or more permeate solution supplies, in particular to a single permeate solution supply. The outlets of the second compartments may be connected to one or more permeate extraction tanks.

[0088] Ion transfer units can be the same or different. In particular, they can have different membranes. For example, M, A, and / or the value of x can be different. The membranes can be configured to extract different ion species, including in cascades depending on the initial ion solution.

[0089] Ion transfer process

[0090] The invention also relates, according to a fourth aspect, to a selective ion transfer method comprising the steps consisting in: providing a device as described above or an ion transfer unit comprising a first and a second compartment separated from each other by a membrane as described above, inserting an ionic solution comprising a first and a second different ion species into the first compartment, the ionic solution being in contact with a main face of said membrane in said first compartment, and transferring for a predetermined duration at least a portion of the ions of said ionic solution through said membrane to said second compartment with a selectivity of the first ion species relative to the second ion species strictly greater than 1 so as to form a permeate in said second compartment and a retentate in said first compartment.

[0091] Such a method makes it possible to recover a permeate having a ratio between the molar composition of the first ion species and between the second ion species greater than that of said ionic solution.

[0092] The second ion species can be the majority ion species by mole in the ionic solution excluding the first ion species.

[0093] Ionic solution

[0094] The transfer of ions during the predetermined duration through said membrane to said second compartment is preferably carried out with a selectivity of the first ion species relative to the second ion species greater than or equal to 2, even better greater than or equal to 10, even better greater than or equal to 100. The ionic solution may comprise at least two different ion species chosen from copper, iron, nickel, lead, aluminum, lithium, silver, manganese, cobalt, hydrogen, sodium, potassium, rubidium, cesium, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine.A correlation between the permeation rates / fluxes of ions through said membrane and their hydrated radii allows this membrane to be applied to many ion species.

[0095] Preferably, the first ion species, all isotopes combined, is one of the ions silver, lead, lithium, hydrogen, sodium, potassium, rubidium and cesium and the second ion species, different from the first ion species, can be one of the ions copper, iron, nickel, aluminum, manganese, lead, lithium, cobalt, hydrogen, sodium, potassium, rubidium, cesium, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine.

[0096] The ionic solution is preferably an acidic solution, in particular containing hydrochloric acid, sulfuric acid and / or nitric acid, or even organic acids. The ionic solution may have a pH less than or equal to 7, better still less than or equal to 3, better still less than or equal to 1, even better still less than or equal to 0, even better still less than or equal to -0.6. Such a pH promotes the selectivity of the membrane.

[0097] Alternatively, the ionic solution could be basic. For example, in the case of a leaching solution that has undergone selective precipitation steps by increasing the pH.

[0098] Preferably, the permeate obtained has a molar composition in ions of the first species of ions enriched by a factor greater than 5, better than 10, better than 50, even better than 100, even better than 1000, relative to the molar composition in ions of the first species of ions of the ionic solution inserted into the first compartment.

[0099] By "the permeate obtained has a molar composition in ions of the first species of ions enriched by a factor greater than", we understand that the molar composition, that is to say the relative molar proportion, of the first species in the permeate is greater than that of the first species in the initial ionic solution, the ratio between the molar composition of the first species in the permeate and the molar composition of the first species in the initial ionic solution being greater than the factor indicated.

[0100] Preferably, the ionic solution comprises silver ions and the permeate obtained may have a molar composition of silver ions enriched by a factor greater than 5, better than 50, even better than 100, even better than 1000, relative to the molar composition of silver ions of the ionic solution inserted into the first compartment. The permeate obtained may have a molar composition of silver ions greater than or equal to 0.5%, better than or equal to 5%, even better than or equal to 50%, even better than or equal to 90%, of the total molar composition of ions of the permeate. This depends in particular on the initial composition of the ionic solution and the predetermined transfer duration.

[0101] The ionic solution may comprise silver ions and copper, aluminum, iron, nickel, manganese, cobalt, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine ions, the transfer of the ions during the predetermined time through said membrane to said second compartment being carried out with a selectivity of the silver ions with respect to at least one, better each, of the copper, aluminum, iron, nickel, manganese, cobalt, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium ions, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine greater than or equal to 2, better still greater than or equal to 10,better greater than or equal to 100, even better greater than or equal to 500. The permeate obtained may have a molar composition in silver ions greater than or equal to 60%, better greater than or equal to 75%, even better greater than or equal to 80%, even better greater than or equal to 90%, of the total molar composition in ions of the permeate.,

[0102] The ionic solution may comprise silver ions and lithium, lead and / or sodium ions, the transfer of the ions during the predetermined duration through said membrane to said second compartment being carried out with a selectivity of the silver ions compared to the lithium, lead and / or sodium ions strictly greater than 1, better still greater than or equal to 5, even better still greater than or equal to 10.

[0103] Alternatively, the ionic solution may comprise hydrogen ions and other ion species among lithium, lead, silver, copper, iron, nickel, aluminum, manganese, cobalt, sodium, potassium, rubidium, cesium, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine, the transfer of the ions during the predetermined duration through said membrane to said second compartment being carried out with a selectivity of the hydrogen ions with respect to at least one, better each, of the other aforementioned ion species strictly greater than 2, better greater than or equal to 10, better greater than or equal to 100, even better greater than or equal to 500.

[0104] Alternatively, the ionic solution is substantially free of silver ions. The resulting permeate may have a molar ion composition of the first ion species enriched by a factor greater than 2, more preferably greater than 5, relative to the molar ion composition of the first ion species of the ionic solution inserted into the first compartment. The first species may be lithium, lead, sodium, potassium, rubidium and / or cesium.The ionic solution may further comprise other ion species among the ions copper, iron, nickel, aluminum, manganese, cobalt, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine, the transfer of the ions during the predetermined duration through said membrane to said second compartment being carried out with a selectivity of the ions of the first species with respect to at least one, better each, of the other aforementioned ion species greater than or equal to 2, better still greater than or equal to 10, even better still greater than or equal to 20.

[0105] Osmosis

[0106] Preferably, the method comprises inserting a permeate solution into the second compartment, the transfer of at least a portion of the ions from the ionic solution through the membrane being carried out by osmotic transfer into the permeate solution. Alternatively, the ionic transfer of at least a portion of the ions from the ionic solution through the membrane being carried out by passage, in particular under pressure, of at least a portion of the ionic solution through the membrane.

[0107] The permeate may be an acidic solution. Preferably, in the case of extraction of a species other than hydrogen, the pH difference between the permeate solution and the ionic solution is less than or equal to 2. Such a pH difference between the two solutions makes it possible to limit the competition between the transfer of metal ions and the transfer of protons, which improves the transfer of ions other than hydrogen and the selectivity of the first ion species compared to the second ion species.

[0108] The method may include stirring the ionic solution and / or the permeate solution during ion transfer. Such stirring makes it possible to homogenize the ionic solution during ion transfer and to limit the phenomena of ion concentration polarization at the surface of the membrane, which improves the extraction of the first ion species in the solution.

[0109] The method may comprise a step of circulating the ionic solution in a fluidic circulation circuit, in particular a microfluidic circuit, comprising a chamber or a portion of conduit forming the first compartment between an inlet of the ionic solution and an outlet of the retentate. The method may comprise circulating the permeate solution in a fluidic circulation circuit, in particular a microfluidic circuit, comprising a chamber or a portion of conduit forming the second compartment between an inlet of the permeate solution and an outlet of the permeate. The circulation of the ionic solution and the permeate solution may be in the same direction and the same sense in the fluidic chambers relative to the membrane. Alternatively, they are in opposite directions to each other. The flow rates of the ionic solution and the permeate solution may be identical or not.Preferably, the flow rate of the ionic solution and / or the permeate solution is chosen so that the contact time of the ionic solution with the membrane corresponds to the predetermined transfer time. The flow rate of the ionic solution and / or the permeate solution may be a function of the effective separation surface of the membrane.

[0110] The predetermined duration may be a function of the volumes of the compartments, the contact surfaces with the membrane, the concentrations of the different ion species, the structure of the membrane, in particular the selective ion transfer layer, the agitation of the solutions, the first ion species, the shape of the compartments, in particular their contour relative to the membrane. It may be predetermined to present an optimal selectivity of the first ion species compared to the second ion species, the second ion species being preferentially the majority species outside the first ion species in the initial ionic solution.

[0111] The predetermined duration may be less than or equal to 10 days, better still less than or equal to 6 days, even better less than or equal to 3 days, even better less than or equal to 30 min.

[0112] The process may include extraction of retentate and permeate

[0113] The method may comprise the use of the extracted retentate or permeate as an ionic solution in the same ionic transfer unit or another ionic transfer unit comprising a first and a second compartment separated from each other by a membrane, in particular as described above. The method may then comprise several ionic transfer stages in successive ionic transfer units or in the same ionic transfer unit. Thus, it is possible to obtain a permeate which is increasingly pure in terms of the first ion species or a retentate which is less and less concentrated in terms of the first ion species.

[0114] Preferably, the method comprises several ion transfer stages in successive ion transfer units connected in series with each other. The method can be carried out with continuous flow between the different ion transfer stages.

[0115] At least two, or more preferably all, of the ion transfer units may be different, including having different membranes. The different membranes may be configured with respect to each other and the ion transfer units may be arranged with respect to each other to extract different ion species from the ionic solution.

[0116] At least two, or better all, of the ion transfer units may be identical.

[0117] The method may comprise at least the extraction by the first ion transfer unit of a first ion species, then the extraction by the second transfer unit of another ion species, the retentate having been depleted in the first ion species. The membranes may be identical, the retentate being depleted in the first ion species, thus allowing the extraction with the same membrane of another ion species. Alternatively, the membranes of two successive transfer units are different and chosen to extract different ion species. The method may comprise the insertion of the retentate from an upstream ion transfer stage into a downstream ion transfer stage as an ionic solution, the permeates from the downstream stage and the upstream stage being extracted.

[0118] Alternatively, the method may include inserting the permeate from an upstream ion transfer stage into a downstream ion transfer stage as an ionic solution.

[0119] Recycling process

[0120] The invention also relates, according to a fifth aspect, to a method for recycling waste electrical and electronic equipment, jewelry, jewelry waste, metal alloys and / or silverware using the membrane comprising the steps of the ionic transfer method as described above.

[0121] The process may also include a step of leaching electrical and electronic waste, in particular from the treatment of electronic waste such as printed circuits or photovoltaic panels, jewelry, jewelry waste, metal alloys and / or silverware, the ionic solution comprising the leaching solution thus obtained.

[0122] Brief description of the drawings

[0123] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which:

[0124] [Eig 1] schematically represents in section a membrane according to the invention,

[0125] [Eig 2] is a scanning electron microscope view of a membrane according to the invention at x5000 magnification,

[0126] [Eig 3] is a membrane variant according to the invention,

[0127] [Eig 4] represents a device according to the invention,

[0128] [Eig 5] represents a variant of the device according to the invention,

[0129] [Fig 6] corresponds to graphs representing the permeation rate P of different ions as a function of time for a membrane according to the invention (graph a) and a porous PVDF support without a selective ion transfer layer (graph b),

[0130] [Fig 7] is a graph representing the selectivity S of silver ions with the other ions of the ionic solution of figure 6 for a membrane according to the invention H3 / PVDF and a porous support in PVDF without selective ionic transfer layer, [Fig 8] is a graph representing the molar composition Cm in different ions of the ionic solution (on the left at t=Oh) and in the permeate (on the right) at different times (8, 24, 48, 78 and 144h) of the experiment of figures 6 and 7,

[0131] [Fig 9] is a graph representing the permeation rate P of different ions as a function of time for a membrane comprising an ion transfer layer comprising bentonite nanosheets,

[0132] [Fig 10] represents graphs corresponding to the permeation flux J of different ions as a function of time (graph a) and to the selectivity S of silver ions with other ions (graph b) for H3 / PVDF membranes according to the invention having different quantities of nanomaterials,

[0133] [Fig 11] represents graphs corresponding to the permeation flux J of different ions as a function of time (graph a) and to the selectivity S of silver ions with other ions (graph b) for H3 / PVDF membranes according to the invention from different phases,

[0134] [Fig 12] represents the permeation flux J of different ions as a function of time for an H3 / PVDF membrane according to the invention, comparing the transfer in acidified solutions with different acids,

[0135] [Fig 13] represents graphs corresponding to the permeation flux J of different ions (graph a) and to the selectivity S of silver ions with other ions (graph b) for an H3 / PVDF membrane according to the invention, comparing the ionic transfer at different acidity concentrations in solution,

[0136] [Fig 14] is a graph representing the permeation rate P of different ions as a function of time for a membrane according to the invention with different molar concentrations of acids in the ionic solution and the permeate solution,

[0137] [Fig 15] is a graph representing the quantity of protons as a function of time in the permeate and the retentate in the case of first and second compartments separated by a membrane according to the invention with a 1.0 M nitric acid solution on the side of the first compartment and 45 mL of a 0.10 M HNO3 solution on the side of the second compartment,

[0138] [Fig 16] is a graph representing the permeation rate P of different ions as a function of time for an H3 / PVDF membrane according to the invention, [Fig 17] is a graph representing the permeation rate P of different ions as a function of time for an H3 / PVDF membrane according to the invention,

[0139] [Fig 18] is a graph representing the permeation rate P of different ions for different ion species after 48h of transfer for membrane variants according to the invention,

[0140] [Fig 19] represents graphs corresponding to the permeation flux J of different ions (graph a) and to the selectivity S of silver ions with other ions (graph b) for an H3 / PVDF membrane according to the invention, comparing the ionic transfer from an ionic leaching solution and a synthetic ionic solution at 2 days of transfer and 10 days of transfer,

[0141] [Fig 20] is a graph representing the molar composition Cm in silver and copper ions of the ionic solution (at t=Oh) and the permeate (on the right) at different times (24, 49 and 120h) for different solutions, a solution with a ratio [Cu 2+ ] / [Ag + ] of about 50 (left part), with stirring (AA) and without stirring (SA) and a solution with a ratio [Cu 2+ ] / [Ag + ] of approximately 4500 without agitation (SA),

[0142] [Fig 21] represents variants of microfluidic device according to the invention,

[0143] [Fig 22] is a graph representing the permeation rate P of different ions for different successive separations using the microfluidic device of Figure 21, images a to c after a contact time of 1.7 min for each separation,

[0144] [Fig 23] is a graph showing the permeation rate P of different ions by transfer using the two microfluidic devices of Figure 21 as a function of contact time (determined by the device used and the fluid flow rate in the two compartments), and

[0145] [Fig 24] presents graphs representing the permeation rate P (graph a) of different ions and the selectivity with respect to the silver ion (graph b) by transfer using the microfluidic device of Figure 21, images a to c as a function of the direction of the current of the ionic solution with respect to the permeate solution in the microfluidic circulation conduits.

[0146] [Fig 25] is a diffractogram of a powder of KaSbaPiOu nanosheets.

[0147] [Fig 26] is a diffractogram of a powder of nanosheets of K3Sb2,7Bio,3P20i4, hereinafter denoted “K3Biio%”, and [Fig 27] is a diffractogram of a powder of nanosheets of K3Sb2,25Bio,7sP20i4, hereinafter denoted “KaBi25%”.

[0148] Detailed description

[0149] Figure 1 illustrates a membrane 10 according to the invention comprising a porous support 30 comprising two opposite main surfaces 32 and 34 and a selective ion transfer layer 20 extending over the main surface 32.

[0150] The selective ion transfer layer 20 comprises, as visible in FIG. 2, sheets of a nanomaterial extending over one of the two main surfaces 32 of the porous support. The nanomaterial has the formula:

[0151] XMN014

[0152] M being of formula As3(i- y-z)Sb3yBi3z and N being of formula P3kAs(ik), y, z and k being numbers varying from 0 to 1 with y+z less than or equal to 1, X being of formula H3(i- X )A3X, A being an alkali or an ammonium salt, x being a number ranging from 0 to 1. For example, M is As3, Sb3, Bi3, As2Bi, As2Sb, Sb2,sBio,5, Aso,sSb2Bio,5 among others. Preferably, A is selected from lithium, sodium, potassium, rubidium, cesium, tetramethyl ammonium or a cation derived from a water-soluble hydroxide salt or a mixture thereof, tetraethyl ammonium (TEA) or tetrabutyl ammonium, or any other ammonium or molecular (or ionic) cation existing in the form of a water-soluble hydroxide salt or their mixture. For example, H3(i- x )A3x is H3, H2,?Nao,3, TEA3, Hi,iLii,2Rbo,7 among others.

[0153] According to a first embodiment, the nanomaterial has the formula XMP2O14, X and M being as described previously.

[0154] According to a second embodiment, the nanomaterial is of formula XMNO14, X, M and N being as described previously, k being different from 1 in the formula of N.

[0155] In the latter case, the parameters z and k are preferably different from 0 and the parameter y is preferably different from 1.

[0156] The selective ion transfer layer 20 has an average surface quantity of nanomaterials greater than or equal to 0.3 mmol / m 2 , better greater than or equal to 0.5 mmol / m 2 , even better greater than or equal to 0.6 mmol / m 2. The sheets 22 preferably extend in the selective ion transfer layer 20 along extension planes that are substantially parallel or inclined at an angle less than or equal to 45° to the extension plane of the selective ion transfer layer 20 and are preferably substantially uniformly distributed in the selective ion transfer layer 20. Preferably, the selective ion transfer layer 20 has a thickness in the dry phase at a temperature of 20°C that is substantially constant and greater than or equal to 10 nm, better still greater than or equal to 15 nm, even better still greater than or equal to 20 nm. The average inter-sheet distance in the dry phase at a temperature of 20°C is between 0.5 nm and 2 nm, better still between 0.8 nm and 1.6 nm. The average size of the sheets 22 in two dimensions in the plane of the selective ion transfer layer 20 is preferably greater than the average size of the pores of the porous support, in particular between approximately 100 and 2500 nm.

[0157] The selective ion transfer layer 20 may comprise more than 90%, by mass, of nanomaterials and be devoid of binder between the sheets 22.

[0158] Alternatively, the selective transfer layer 20 may be a hybrid layer comprising: a polymer, notably chosen from polyamide, polyimide, polyester, polyamine, polyurethane, polyurea, and the nanomaterial sheets in the polymer, the proportion by mass of nanomaterial sheets in the selective ionic transfer layer being between 25% and 40%.

[0159] The porous support 30 may have an average pore size less than or equal to 10 μm, better less than or equal to 1 μm, better less than or equal to 500 nm, even better less than or equal to 300 nm. The porous support 30 may be made of a material compatible with acid solutions, for example polyvinylidene fluoride (PVDF), in particular hydrophilic, or polytetrafluoroethylene (PTFE). If resistance to very acidic or very basic pH values ​​is not necessary, any porous substrate may be suitable because its role is simply to provide mechanical strength to the assembly.

[0160] In a variant illustrated in FIG. 3, the membrane 10 may comprise a porous protective layer 40 extending over the selective transfer layer 20 on the side opposite the support 30.

[0161] Such a membrane 10 can be integrated into an ion transfer unit of a device 100 between two compartments 110 and 120, as illustrated in FIG. 4. The ion transfer unit is preferably fluid-tight, except through the membrane 10.

[0162] Such an ion transfer unit makes it possible to introduce into the first compartment 110 an ionic solution SI to be treated and to introduce into the second compartment 120 a permeate solution SP so that a selective ionic transfer takes place through the membrane 10 by osmosis. The two solutions SI and SP are in contact with the membrane by its faces 12 or 14 respectively. It is then possible to recover a permeate and a retentate having ionic concentrations different from the initial solution, in particular a permeate enriched in certain ions, in particular silver, lithium and / or lead.

[0163] In a variant further illustrated in FIG. 5, the device 100 comprises a plurality of ion transfer units 100a to 100c each as described previously in series with respect to each other.

[0164] The outlet of the first compartment 110a of the first ion transfer unit 100a is connected to the inlet of the first compartment 110b of the second ion transfer unit 100b so that the retentate RI extracted from the first ion transfer unit 100a is entered as an ionic solution in the second ion transfer unit 100b and the outlet of the first compartment 110b of the second ion transfer unit 100b is connected to the inlet of the first compartment 110c of the third ion transfer unit 100c so that the retentate R2 extracted from the second ion transfer unit 100b is entered as an ionic solution in the third ion transfer unit 100c. The second compartments 120a, 120b and 120c can be supplied at the inlet with the same permeate solution SP or, alternatively not shown, with different permeate solutions.The outlets of the second compartments 120a, 120b and 120c are connected to the same tank 150 for recovering the permeates P1, P2 and P3. The retentate R3 at the outlet of the first compartment of the third ion transfer unit 100c may or may not be recovered. In this case, the method comprises inserting the ionic solution SI into the first compartment 110a, recovering the retentate RI at the outlet of the first compartment 110a to introduce it at the inlet of the first compartment 110b and recovering the permeate PI in the reservoir 150, recovering the retentate R2 at the outlet of the first compartment 110b to introduce it at the inlet of the first compartment 110c and recovering the permeate P2 in the reservoir 150 and recovering the permeate P3 in the reservoir 150. The permeate Pe recovered in all of the second compartments 120a, 120b and 120c then has a very good extraction rate of the first ion species.

[0165] The extraction process by this device may be sequential between the different ion transfer stages or, preferably, be carried out in continuous flow between the different ion transfer stages, the upstream stage retentate continuously feeding the inlet of the downstream stage at a flow rate defined by the initial supply of ion solution and the sizes of conduit connecting the different stages.

[0166] The illustrated example is limited to three ion transfer stages but only two or more stages can also be implemented in a similar manner.

[0167] The ion transfer units 100a, 100b and 100c may be identical or alternatively different from each other. If they are identical, they may allow a larger quantity of the first ion species to be extracted. If they are different, they may alternatively allow for different selectivities between the ions present in the inlet ionic solution. It is thus possible to create a tailor-made device depending on the initial ionic solution, the application, and the ion species to be separated. For example, it is possible to extract, from a complex solution comprising silver, lithium, and lead ions, successively, each with one or more transfer units, silver, lead, and then lithium.

[0168] The example illustrated in Figure 5 is limited to the reuse of retentates from upstream stages at the inlet of the downstream stages. However, it is possible to have a similar device by reprocessing the permeates instead of the retentates by connecting the outlets of the second compartments 120a and 120b to the inlet of the first downstream compartments 110b and 110c respectively or a mixed device using, depending on the desired result, the permeate in certain transfer stages and the retentate in others.

[0169] Examples of implementation and comparative tests are described below.

[0170] Example 1

[0171] Manufacture of fhSbd composite membrane or PVDF

[0172] A powder of tLSbaPiOu (named H3 in the following) was synthesized. The synthesis is carried out in three steps: the synthesis of a precursor of formula KaSbaPiOu, the cationic exchange between the K + and the H +and washing and drying the powder obtained.

[0173] The first step is carried out by the synthesis of KjSbaPiOu following the protocol described by Piffard et al., in the article “Phosphatoantimonates KSbiPOs, KjSbaPiOu and KsSbsPiCho”. Revue Chim. minérale 1985, 22 (1), 101-106, which consists of heating to 300 °C in air a stoichiometric mixture of monoammonium phosphate (2.24.10' 1 mol, NH4H2PO4, Prolabo), antimony(III) oxide (1.66.10' 1 mol, SbiCh, Merck) and potassium nitrate (3.32.10' 1 mol, KNO3, Prolabo) for 4 h, then at 1000 °C for 24 h.

[0174] The H3 material is then prepared by ion exchange in aqueous solution, described by Piffard et al., “The Layered Phosphatoantimonic Acid PLSbaPiOu, X.H2O”. Revue Chim. minérale 1986, 23 (6), 766-775, according to the following equation.

[0175] K3Sb3P2O 14 + 3 HNO3-» H3Sb3P2O 14 + 3 KNO3

[0176] This step consists of carrying out three cycles defined as follows: (i) for 20.45 g of the white powder of K3Sb3P20i4 obtained previously, the latter is dispersed in 1 L of concentrated nitric acid (7.5 M) in an Erlenmeyer flask fitted with a water condenser, heated to 50 °C and placed under magnetic stirring (280 rpm) for 24 h; then (ii) centrifugation at 4500 g for 2 min to recover the powder. The third cycle was carried out at 80 °C and for 48 h to ensure a complete exchange of the K cations + in H + and the mixture was centrifuged for 3 min.

[0177] The final step of the synthesis, washing the white H3 powder with ethanol, removes the remaining NO3' nitrate ions by successive centrifugation for 3 min at 5000 g, removing the supernatant and replacing it with a new ethanol solution between each centrifugation, until the supernatant has reached a neutral pH. Drying of the solid is carried out at 70 °C for approximately 24 h.

[0178] A white H3 powder was thus obtained. The H3 powder was mixed in ultrapure water (Millipore, 18.2 Milan) in which it exfoliated to form a colloidal suspension of nanosheets on average 1 nm thick and 2 to 3 pm wide. The mixture was stirred for 2 h by magnetic stirring (300 rpm). Optionally, it was then centrifuged at 3600 g for 15 min (Jouan B4i centrifuge). The solution after centrifugation has three phases: on the one hand a "supernatant" phase, composed of the smallest H3 sheets, on the other hand a phase sometimes called "gel", containing larger H3 sheets, and a solid phase, which includes the solid impurities.

[0179] In order to deposit a thin layer of H3 nanomaterials on the porous support, the vacuum filtration technique was chosen. Two vacuum pumps were used: the piston pump, model Tritech TR40, or the membrane pump, model ME 4C NT Vacuubrand. Both pumps were equipped with vacuum pressure measurement and were operated at the same relative pressure. A Rocker brand Büchner type filtration support, consisting of a funnel topped with an integrated sintered glass disc, a glass reservoir and a clamp to hold everything, was used.

[0180] The porous support used to manufacture H3-based membranes according to the invention is a hydrophilic PVDE porous membrane, 47 mm in diameter, with pores of 0.22 μm (Merck brand), and a thickness of 125 μm. This polymer was chosen because of its robustness, stability, flexibility and compatibility with acid solutions. This porous support was wedged between the sintered glass base and the glass reservoir by the holding clamp which sealed the system.

[0181] Several membranes according to the invention were manufactured from different H3 solutions in suspension. The different H3 solutions are obtained by mixing a proportion of H3 powder in ultrapure water (Millipore, 18.2 MO. cm) in which it exfoliates to form a colloidal suspension of nanosheets on average 1 nm thick and 1 to 3 pm wide. The different mixtures were stirred for 2 h by magnetic stirring (300 rpm). Some of these solutions were then centrifuged at 3600 g for 15 min (Jouan B4i centrifuge) to recover only a portion. The solutions after centrifugation have three phases: on the one hand a "supernatant" phase, composed of the smallest H3 sheets, on the other hand a phase sometimes called "gel", containing larger H3 sheets, and a solid phase, which includes the solid impurities.The different solutions were derived from the “supernatant” phase, the “gel” phase, or from mixtures without centrifugation. Each H3 suspension solution was poured onto a porous support in the reservoir. Vacuum was applied to the system at a pressure of -906.6 mbar (or 106.7 mbar absolute pressure) and stopped when all the liquid had passed through the porous support. Each membrane thus obtained was then removed from the filtration support using forceps and left to dry under a hood for approximately 24 h. The compositions of the selective ion transfer layers of the different membranes are shown in Table 1 below. The quantity of H3 nanosheets filtered was calculated for each membrane, from the concentration and volume of filtered suspension and the molar mass of H3 (MH3 = 654.4 g / mol).

[0182] [Table 1]

[0183] Method of separation and measurement

[0184] The previously formed H3 / PVDF membranes were studied in the device 100 of Figure 4 to evaluate their ion separation performance. This device 100 comprises two identical compartments 110 and 120 separated by the membrane 10 cut and surrounded by a PTFE tape to ensure the sealing of the device and limit evaporation. The compartment 110 on the side of the selective ion transfer layer receives the ionic solution to be treated forming the retentate and the other compartment 120 receives a permeate solution forming the permeate.

[0185] Before filling the device, two graduated cylinders containing the permeate solution and the ionic solution respectively were weighed using a precision balance and the cylinders, once emptied, were reweighed to know the exact masses, and therefore the volumes, introduced. The two glass compartments 110 and 120 were filled simultaneously to identical volume. The volume on either side of the membrane is sufficient to completely cover the membrane during the test time, typically 42 mL per compartment. The tests were carried out at room temperature. The compositions of the ionic and permeate solutions are specified subsequently according to the study carried out.

[0186] To measure the evolution of the ion concentration in the permeate and retentate, 0.6 mL samples, typically after 7 h, 24 h, 48 h, 72 h and 144 h of testing, were taken using a volumetric pipette in both compartments. The permeate and retentate were taken from the same volume to maintain a constant volume on each side of the membrane (excluding osmosis). After dilution with 2% nitric acid (prepared from 67-69% HNO3, SCP Science), the samples were analyzed by inductively coupled plasma atomic / optical emission spectroscopy, ICP-OES (model Optima 8300, Perkin Elmer). 2% nitric acid was also used for dilution of standard solutions (QC 7 and QC 21 Multi-Element Control Standards, 1000 ppm, SPEX CertiPrep).

[0187] The permeation flux of ions J through the membrane was calculated using the following equation. where Ji, t (mmol.m^.h' 1) is the permeation flux of ion i at time t, Ani, p , t (mmol) is the variation in the amount of matter of ion i in the permeate at time t, A (m 2 ) is the effective membrane area, i.e. the area of ​​the membrane in contact with the retentate, At

[0188] (h) is the time variation, Ci, p ,t and Ci, p ,o (mg / L) are the concentrations of ion i in the permeate at time t and time t = 0 h respectively, V p ,t and V p ,o (L) are the volumes of the permeate at time t and at time t = 0 h respectively, k is the number of samples taken at time t, Ci, e , P j (mg / L) is the concentration of ion i in the sample taken j at the permeate, V e , P j (L) is the volume of sample j taken from the permeate and Mi (g / mol) is the molar mass of ion i. The effective membrane area is 2.01 cm 2(effective diameter = 1.6 cm). The masses of the initial and final solutions were weighed using a precision balance, giving the initial volumes Vo and final volumes Vf of the two compartments. The volume of the permeate at time t V p ,t (excluding initial and final time) was calculated by the following equation. where V p ,o and V p ,f (L) are the initial and final volumes of the permeate, n is the total number of samples taken during the experiment, Atf (h) is the total duration of the experiment and k, V e , P j and At have been defined previously.

[0189] The permeation rate of ions in the permeate P was also calculated to observe the permeation over time, according to the following equation. where Pi, t (%) is the permeation rate of ion i at time t, ni, r ,o (mmol) is the amount of matter of ion i in the initial ionic solution and Ani, p , twas previously defined.

[0190] Finally, the selectivity Sij between ion i and ion j was determined by calculating the ratio between the permeation rate of the two ions, in order to take into account the difference in concentration between the two ions in the feed.

[0191] Composition of ionic and permeate solutions

[0192] Among the chemical elements present in the printed circuit boards of waste electrical and electronic equipment (WEEE), nine metal ions were studied: (i) copper, iron, nickel, lead, aluminum and silver, present in many electronic components; and (ii) manganese, cobalt and lithium present more predominantly in batteries. Copper, aluminum, lead and silver also constitute photovoltaic cells. Thus, the separation performance of the membranes could be evaluated on chemical elements from several types of waste, but also on ions of several valences.

[0193] The mineral acid HNO3 was used to acidify ionic and permeate solutions. This acid is one of the acids used in leaching. It is a powerful oxidant, which eliminates the need for other oxidants such as hydrogen peroxide. It can solubilize a wide range of metals, particularly silver, which is difficult to dissolve in other media, particularly sulfuric or hydrochloric media, and it can be regenerated.

[0194] The ionic solution for the separation tests was prepared from copper nitrates (Cu(NO3)2-3H2O, 98 - 103%), iron (Fe(NO3)3-9H2O, > 98%), nickel

[0195] (Ni(NO3)2-6H2O, > 97%), lead (Pb(NO3)2, > 99%), aluminum (A1(NO3)3-9H2O, > 98%), silver (AgNO3, > 99%), manganese (Mn(NO3)2-4H2O, > 97%), cobalt (CO(NO3)2-6H2O, > 98%) and lithium (LiNO3, 99.99%), from Sigma Aldrich. In WEEE printed circuit boards, these elements can be concentrated at hundreds or thousands of ppm - like silver, manganese or cobalt - up to sometimes several tens of percent by mass - like iron, copper or aluminum. An intermediate molar concentration of 10.0 mmol / L, identical for each metal ion used, was chosen for the separation tests, to study the permeation of these ions at the same initial concentration. The nine metal nitrates were dissolved in a 1.00 mol / L nitric acid solution (prepared from HNO3, 68% VWR or 70% Sigma Aldrich). In the literature, the leaching acid concentration is often between 1 and 10 mol / L, or even higher.The use of a concentration of 1 mol / L was chosen to limit HNO3 consumption and releases.

[0196] The permeate solution is a 1.00 mol / L nitric acid solution. The use of an identical acid concentration on each side of the membrane was chosen to allow only the separation of metal ions by the membrane to be observed.

[0197] All solutions were magnetically stirred for 30 min at 300 rpm before use in both compartments.

[0198] Comparison between an H3 / PVDF membrane and a PVDF membrane

[0199] The H3 / PVDF membrane type H3-NC-1-7 in Table 1 was tested with the ionic and permeate solutions described previously and the ion permeation was monitored over time.

[0200] At the same time and for reference, a PVDF membrane, without a selective ion transfer layer, was also tested under the same conditions.

[0201] The graphs in Figure 6 represent the ion permeation rates as a function of time measured for the H3 / PVDF membrane of type H3-NC-1-7 in graph a of Figure 6 and for the PVDF membrane in graph b of Figure 6. It shows in graph a a permeation of 40.0% of Ag ions + through the H3 / PVDF membrane in 144 h (6 days), corresponding to a permeation flux of 6.1 mmol.m' 2 .h _1 . At 6 days, Pb ions 2+ also pass through the H3 / PVDF membrane with a permeation rate of 5.4% (permeation flux = 0.89 mmol.m' 2 .h _1 ), followed by Li ions +at 0.79%. Finally, the other six ions are almost completely blocked by the membrane, with permeation rates below 0.25%. With the reference sample, the PVDF membrane without H3 (see graph b), all ions show a high permeation rate of the same order after 6 days of osmosis, between 38.7 and 44.0%. The H3 nanomaterial layer therefore provides selectivity and allows significant separation, mainly between silver and the other ions.

[0202] Indeed, on a quantitative level, Figure 7 gives the selectivities between silver ions and other ions for the H3 / PVDF (left columns) and PVDF (right columns) membranes after 144 h, showing no selectivity (approximately equal to 1.1) of the ions with the silver ions for the PVDF membrane and for the H3 / PVDF membrane: (i) a very high selectivity between silver and the trivalent Fe ions 3+ and Al 3+(selectivity of 397 and 439 respectively); (ii) as well as with the divalent Cu ions 2+ , Neither 2+ , Co 2+ , Mn 2+ (selectivity between 191 and 291); (iii) a selectivity of 7 for lead, which is therefore the lowest.

[0203] Figure 8 provides the molar elemental composition Cm of the ionic solution (left at t=Oh) and the evolution of the molar composition in the permeate (right) at different times (8, 24, 48, 78 and 144h) of the experiment. The H3 / PVDF membrane thus allows to go from a nine-metal solution, with a molar composition of approximately 11% for each ion, to a solution enriched to 95.6% in silver ions, with 3.6% lead ions in 8 hours of permeation. The enrichment in silver ions decreases over time, as the other ions, including mainly lead, continue to pass through the H3 / PVDF membrane. Comparison of the ion separation performance with another 2D material, bentonite, with a high surface charge density but non-porous

[0204] Bentonite, Na + -montmorillonite is a natural clay that exfoliates directly in water.

[0205] The bentonite used is commercially available in the form of a fine powder (purity > 95% according to the supplier Fisher Scientific). 20.01 g of powder was dispersed in 400.0 mL of ultrapure water; the colloidal suspension of approximately 50 g / L of exfoliated bentonite nanosheets was magnetically stirred for 3 h at 300 rpm. The suspension was centrifuged at 3600 g for 10 min (Jouan B4i centrifuge), to obtain, on the one hand, the "supernatant" phase, composed of the smallest sheets, on the other hand, the "gel" phase, containing the larger sheets, and a solid phase, which includes the solid impurities. Approximately 300 mL of “supernatant” phase was recovered and concentrated in a rotary evaporator (Rotavapor R-210, Büchi), for 1 h at 130 mbar at 60 °C, allowing the volume of the “supernatant” phase to be reduced by approximately 50%.The concentrations of the supernatant phase thus concentrated and of the “gel” phase (without further modification) were determined by TGA, at 3.00 and 9.02% by mass respectively. The average sizes of the bentonite sheets, determined by SEM images, are 315 nm for the “supernatant” phase and 1500 nm for the “gel” phase. The thickness of the sheets is approximately 1.33 ± 0.13 nm. In order to deposit a thin layer of Na-bentonite nanomaterials on the porous support, the same vacuum filtration technique as for the H3 membranes was chosen, with the same PVDF support and the same suction pressure.

[0206] Membranes based on the supernatant phase were prepared. Typically, 5.0 mL of 8.00 g / L bentonite (BE) colloidal suspensions, or 40 mg of bentonite, were filtered. Approximately 15 min of filtration was required to fabricate the bentonite / PVDF hybrid membranes.

[0207] The permeation rates of the nine ions were plotted in Figure 9 as a function of time, for an experiment carried out over four days.

[0208] First of all, it is possible to observe that all the studied ions pass through the membrane from the first hours of permeation. No ion is preferentially rejected by the membrane. Then, a segregation between mono-, bi- and bivalent ions seems to appear, also from the first hours of the experiment, with a permeation order as follows: +1 (Ag + and Li + ) > +2 (Pb 2+ , Cu 2+ , Neither 2+ , Co 2+ , Mn 2+ ) > +3 (Fe 3+ , Al 3+ ). The difference in permeation rates between divalent ions and trivalent ions is not very clear, but among monovalent ions, silver passes more through the membrane than lithium, with a permeation rate of 33.9% for Ag +against 25.4% for Li + after 96 hours of testing. The selectivity between the ions does not exceed a value of 2.

[0209] It is deduced that the Na-bentonite / PVDF hybrid membranes are not particularly selective for one or more ions, among those studied, unlike the H3 / PVDF membranes.

[0210] Study of the variation in the quantity of nanomaterials

[0211] The separation performances of H3 / PVDF membranes, manufactured from different amounts of H3 from uncentrifuged solution, from 11 to 0.76 pmol (see Table 1), were compared after 72 h of testing. Graph a in Figure 10 gives the permeation flux J of the different ions through these different membranes. The decrease in the amount of nanomaterials, and consequently the decrease in the thickness of the H3 / PVDF membrane, leads to an increase in the permeation flux J of all ions. This increase in permeation flux J, although interesting for example for silver ions, also leads to a decrease in the selectivity S and therefore in the purity of the silver recovered in the permeate. This variation in selectivity between Ag +and the eight other metals tested is shown in graph b of Figure 10. Decreasing the amount of nanomaterials filtered on the PVDF support, from 11 to 7.6 pmol of H3, significantly reduces this selectivity by a factor of 5 to 6 depending on the ions, except for Ag / Cu where the decrease is more moderate (factor 1.3) and Ag / Pb and Ag / Li where the selectivities remain unchanged within the uncertainty interval. Between 7.6 and 3.8 pmol, the silver selectivities also decrease, by a factor of about 2, except for the two pairs Ag / Cu and Ag / Li, where the selectivity decreases by a factor of 4. With 0.76 pmol of H3 in the membrane, the ion permeation fluxes increase (by a factor of 6 to 40 compared to the membrane with 3.8 pmol of H3), except for Ag + where the increase is less, reflecting a decrease in Ag selectivity + / other ions at about 2. This limit of membrane separation efficiency from a certain amount of H3, between 0.76 and 3.8 pmol, may be due to an insufficient number of leaflet layers.

[0212] In order to maintain high selectivity between silver ions and other ions in the next permeation tests, the concentration and volume parameters of filtered H3 colloidal suspension were kept at 1 g / L and 7 mL respectively, or 11 pmol of H3. In addition, to observe a silver selectivity greater than 2, the amount of H3 nanomaterials must be approximately greater than 0.67 mmol / m 2 , i.e. a thickness of the H3 layer approximately greater than 20 nm.

[0213] Study of the variation in the size of nanosheets

[0214] To study the variation in nanosheet size and purity of the 2D material (before and after centrifugation), H3 / PVDF membranes made from the uncentrifuged phase, the supernatant phase, or the gel phase (H3-NC-1-7, H3-S-1-7, or H3-G-1-7 membranes in Table 1) were tested and compared after 48 h of permeation. The supernatant phase has the smallest nanosheets in diameter, while the gel phase consists of the largest sheets, and the uncentrifuged phase contains all sizes of nanosheets as well as traces of unexfoliated solid impurities from the initial solid-phase synthesis. Graph a in Figure 11 shows the permeation fluxes J of the nine ions for the different phases of H3 and graph b in Figure 11 shows the ion selectivity with respect to silver for the eight ions for the different phases of H3. For Ag ions +, the permeation flux J with the "supernatant" phase is similar (considering the uncertainties) to that with the uncentrifuged phase, while with the gel phase the permeation flux is lower than that with the uncentrifuged phase. This shows that by decreasing the average size of the sheets the Ag ions + pass more quickly through the H3 / PVDF membrane.

[0215] Looking at the permeation of lead, we observe that by removing solid impurities, lead is more rejected by the H3 / PVDF membrane, which results in an increase in Ag / Pb selectivity, as shown in graph b of Figure 11. In addition, as for Ag ions + , Pb ions 2+ pass less quickly through the membrane when the H3 sheets are the largest ("gel" phase). For Li ions + , the variation in permeation flux between different membrane types is negligible.

[0216] The H3 / PVDF membrane formed with the nanosheets from the “supernatant” phase strongly rejects other ions (except Ag + , Pb 2+ and Li + ), with a permeation flux < 0.03 mmol.m' 2 .h _1 , as with uncentrifuged H3, maintaining a very high silver selectivity (greater than 400). The permeation flux of these other ions is, on the other hand, higher with the “gel” phase, which leads to a decrease in the selectivity between silver and these ions, observed in graph b of figure 11.

[0217] This first study of the influence of the size of the nanosheets thus shows an increase in the Ag / Pb selectivity, by a factor of approximately 2, by purification (by centrifugation) of the H3 phase and a permeation flux of silver and a selectivity between Ag + and Li ions + , Cu 2+ , Neither 2+ , Co 2+ , Mn 2+ , Fe 3+ and Al 3+higher with an H3 / PVDF membrane from the “supernatant” phase than with an H3 / PVDF membrane from the “gel” phase.

[0218] Lithium ion extraction

[0219] The feed here is an equimolar mixture (10.0 mmol / L) of the five ions in 1.0 M acid (permeate: same acid at 1.0 M). The five ions are lithium, nickel, cobalt, manganese and copper, which are the main elements constituting NMC lithium-ion batteries. The H3 / PVDF membranes used are of the H3-S-1-7 type, i.e. they were manufactured with the "supernatant" phase. The tests are carried out with two acids, sulfuric acid H2SO4 and hydrochloric acid HCl.

[0220] The ion permeation fluxes are shown in Figure 12 for the two leaching acids used. According to the data in Figure 12, the permeation flux of each ion through the membrane is identical, within the uncertainty range, between the two acids used. The permeation flux of lithium ions remains low (around 0.3 mmol.m' 2 .h _1 ), compared to that of silver for example, previously tested (13.9 mmol.m' 2 .h _1 ). However, the difference in permeation between lithium and other ions shows interesting separation potentials in the context of lithium-ion battery recycling.

[0221] Study of the impact of pH

[0222] To observe the effects of a decrease in pH on separation performance, a nitric acid concentration of 5.0 M was chosen to prepare the feed and permeate solutions. To limit the quantities of reagents and ions studied, only Ag ions + (monovalent ion), Pb 2+ (particular behavior), Cu 2+ (bivalent ion) and Fe 3+ (trivalent ion) were tested, at 10.0 mmol / L.

[0223] The separation results at this high nitric acid concentration were compared with those obtained with 1.0 M nitric acid solutions (other parameters remaining unchanged). H3-S-1-7 type membranes were used in both cases. Figure 13 compares the permeation fluxes J and silver selectivities S of the membranes in media with nitric acid concentrations HNO3 of 1.0 M and 5.0 M respectively after an identical transfer time of 118 h. The main observation that emerges is the significant inhibition of the permeation of Pb ions 2+ , Cu 2+ and Fe 3+ with a 5 times higher concentration of protons. The drop in permeation is even more obvious for lead (-98%), which is blocked by the decrease in pH, while conversely, Ag ions +have a slightly higher permeation flux (+33%). These negative pH conditions (pH = -0.70) therefore result in a significantly higher selectivity between silver and other ions than with a pH = 0. The pH therefore has a significant influence on the selectivity of ion transfer through the membrane. Thus, depending on the species to be extracted, it may be preferable for the ionic and permeation solutions to be at negative pH. However, the invention is not limited to acidic pHs.

[0224] Then, a forward osmosis permeation test through an H3 membrane was carried out with different nitric acid concentrations on either side of the membrane: 5.0 M on the ionic solution side, with Ag ions + , Pb 2+ , Cu 2+ and Fe 3+at 10.0 mmol / L, and 1.0 M on the permeate solution side. As observed in Figure 14, after almost 5 days of osmosis, the silver permeation rate remains low, at 2.3%, close to the permeation rate of other ions, thus severely limiting the silver selectivity. With an identical nitric acid concentration on each side of the membrane, a silver permeation rate of 35-40% is observed after 5 days of osmosis. This difference may be due to competition between the permeation of protons and silver ions.

[0225] Proton transfer across the H3 membrane

[0226] The transfer of protons across an H3-S-1-7 membrane was studied. For this, 45 mL of a 1.0 M nitric acid solution was introduced into the first compartment and 45 mL of a 0.10 M HNO3 solution was introduced into the second compartment. Monitoring the pH in the first and second compartments of the membrane over time allowed the calculation of the quantities of nn+ protons in the retentate and permeate. The evolution over time is provided in Figure 15. After 218 hours of osmosis, an equalization of the quantity of protons is observed, which proves the transfer of protons across the membrane.

[0227] Transfer of different ions across the H3 membrane

[0228] A forward osmosis permeation test through an H3 / PVDF membrane of type H3-NC-1-7 was carried out with an ionic solution comprising a mixture of Fe ions 3+ and rare earths 3+ , Nd 3+ , Pr 3+ , Eu3+ , Yb 3+ at a concentration of 5.0 mM, in 1.0 M HNO3 and a permeate solution containing 1.0 M HNO3. As observed in Figure 16, after 5 days of osmosis, the permeation rate P of all ions is low, less than 1%. This shows that these ions do not mainly cross the membrane and that when mixed with silver for example, a separation between silver and these ions (selective ionic transfer of silver) may also be possible.

[0229] Another forward osmosis permeation test through an H3 / PVDF membrane of type H3-S-1-7 was carried out with an ionic solution comprising a mixture of K ions + , N / A + , Mg 2+ and that 2+at a concentration of 0.10 mol / L in water, and a permeate solution comprising 1.0 M HCl. As observed in Figure 17, after 3 days of osmosis, the permeation rate of potassium ions is approximately 50%, while sodium has a rate of 11.6%, and Mg ions 2+ and that 2+ are mostly blocked by the H3 / PVDF membrane with a permeation rate of less than 0.3%. These differences in permeation rates make it possible, after three days of testing, to obtain selectivities between K + and Na ions + , That 2+ and Mg 2+ respectively 4.5; 192 and 241. It can be observed that potassium ions have a permeation similar to silver ions and calcium and magnesium ions have behaviors comparable to the other bi and bivalent ions tested (excluding lead).

[0230] Example 2

[0231] Synthesis of H3(ix)A3xSb3P2Oi4 phases

[0232] The H3(i- x )A3X Sb3P20i4 (also called for simplification H3(i- X )A3 X ) were obtained by ion exchange, following the equation below:

[0233] H3Sb3P2O 14 . + 3xA0H ^3(ix)^3x^^3 ^ , 2 ^i4 + 3xH2O where A is an alkali cation, notably Li cations + , N / A + , K + , Rb + or Cs + , or a quaternary ammonium cation, in particular tetraethyl ammonium Et4N + , and x is the cation exchange rate (x = n AOH / (3n H3 ) = n A0H / n H +).

[0234] This cation exchange is carried out by acid-base titration of phosphatoantimonic acid with the corresponding alkali or quaternary ammonium bases AOH. The titrations were carried out using a Metrohm automatic titrator (Titrino plus 484). The NaOH and KOH bases used are commercial Titrinorm solutions (0.1 M, VWR). The LiOH, RbOH and CsOH bases were prepared at 0.1 M by dissolving pellets or by diluting stock solutions, supplied by Alfa Aesar. The exact concentrations of the prepared solutions were determined by titration with a Titrinorm solution of HCl (0.1 M, VWR). Typically, 15 mL of H3 suspension from the “supernatant” phase at 1.0 g / L were titrated by successive addition of doses of a volume of 0.01 mL of an alkaline base with a flow rate of 0.05 mL.min' 1with vigorous stirring. This slow protocol is necessary because it involves the titration of a suspended solid acid with a molecular base, for which adding too much base results in local flocculation of the colloids. This phenomenon is restrictive because these flocculates do not redisperse easily. To avoid this, the lowest titration flow rate offered by the device was chosen. At the end of each titration, the electrode was rinsed with deionized water to prepare it for the next titration.

[0235] The titration with the quaternary ammonium base, here tetraethylammonium hydroxide, TEAOH, was also carried out according to the following protocol. 10 mL of a colloidal suspension of H3 from the “supernatant” phase at 0.60 g / L (i.e. nn+=27 pmol) were titrated by successive additions of 10 pL of base, using a syringe pump (WPI, Aladdin AL1000). The base was prepared by diluting commercial solutions (TEAOH: 25.1% by mass, Thermo Scientific) to 0.1 M. The base additions were carried out under vigorous stirring (350 rpm for 3 min for each addition), then the pH was measured after each addition, without stirring, with a pH meter (Mettler Toledo S220 SevenCompact, previously calibrated) (1 to 2 min of pH stabilization). As the titration was long (several hours before reaching equivalence), parafilm was added to the bottle to prevent evaporation of the titrated suspension.

[0236] Study of membranes based on H3(ix)M3xSb3P2Oi4

[0237] These new H3(i- X )A3 X , and more precisely those with A = Li, Na, K, Rb, Cs or TEA, were used to prepare membranes and test their separation capacity.

[0238] These membranes were studied on two membrane separation devices: (i) osmotic cells, previously described, for osmosis separation and (ii) a pressurized system, described later, for nano / ultra / microfiltration by frontal filtration. The latter system was developed to allow the faster study of these membranes.

[0239] The chosen values ​​of x are given in Table 2 below.

[0240] [Table 2]

[0241] The method for manufacturing composite membranes described previously in relation to H3-based membranes was used to prepare these membranes. A volume of 7.0 mL was vacuum filtered onto a PVDE support. The appearance, uniformity, and adhesion to the support of the H3(i- X )A3 X were comparable to the H3-based membranes in Example 1. No notable difference visible to the naked eye was observed.

[0242] Materials and methods The membranes thus manufactured were tested on the batch osmotic separation device described in connection with the H3-based membranes in example 1.

[0243] A leaching-type solution, containing nine metal ions (Ag + , Pb 2+ , Li + , Cu 2+ , Neither 2+ , Co 2+ , Mn 2+ , Fe 3+ and Al 3+) at 10.0 mmol / L in 1.00 mol / L nitric acid HNO3 was used as the ionic solution to test these membranes. A 1.00 mol / L nitric acid solution was introduced as the permeate solution.

[0244] As for example 1 in osmosis separation, monitoring of the concentrations in the permeate by analysis by atomic / optical emission spectroscopy by inductively coupled plasma, ICP-OES (model Optima 8300, Perkin Elmer) over time was carried out, here after 24 h and 48 h of testing.

[0245] Osmosis Separation Results

[0246] The 48 h data are provided in Figure 18. The permeation rates with an H3 membrane, derived from a “supernatant” phase, at the same concentration and same filtered volume, have also been added to Figure 18 for comparison.

[0247] A first general observation from the graph is that silver ions pass more through the different membranes, with a permeation rate of between 31 and 38% depending on the H3(i- phase) X )A3 X used, than the other ions. This first observation shows that the membranes based on the different H3(i- X )A3 X exhibit significant selectivity, notably greater than 13, between Ag ions + and the other eight ions tested.

[0248] The intersheet distances of the phases H3(i- X )A3 X with A = Li, Na, K, Rb, Cs or TEA are respectively 8.1, 8.7, 10.2, 10.5, 10.9 and 16.1 Å against 9.2 Å for H3. Considering the uncertainties, the permeation rates of Ag ions + are almost the same between the different phases H3(i- X )A3 X, around 30-35%. These silver ion permeation rates are higher, by 15 to 41%, than that obtained with the H3 phase, which can be explained by the increase in the interlayer distance. The difference in permeation rates of Ag + between H3 and Hi,sLii,2 is greater (34%) than between H3 and the phases H2,?Nao,3 (19%) and H2,?KO,3 (18%), which can be linked to the value of the exchange rate x, higher for Li.

[0249] Variations in Li ion permeation + are not commented on in detail, given the high uncertainties in the results. Cu ions 2+ , Neither 2+ , Co 2+ , Mn 2+ , Fe 3+ and Al 3+ are mainly rejected by all phases with a low permeation rate. For Pb ions 2+ , the permeation rates obtained with the H3(i- X )A3 Xremain close to that obtained with the H3 membrane (equal to 0.93%), except: (i) for the Hi,sLii,2 and H2,?Ko,3 phases, where the permeation rates are significantly higher (2.64 and 2.38% respectively), and (ii) for the TEA3 phase, with an equally higher rate, equal to 1.45%.

[0250] Example 3

[0251] Fabrication tests of membranes consisting of a porous support (e.g., PVDF) and a thin layer of polyamide (PA) including H3 nanosheets were performed with the "supernatant" H3 phase and piperazine (PIP, 99%, Sigma-Aldrich) and 1,3,5-benzenetricarbonyl trichloride (TMC, 98%, Sigma-Aldrich) monomers. These two monomers are commonly used for the fabrication of the PA layer, in the aqueous and organic phases, respectively. As the 2D H3 material exfoliates in water and is therefore initially in the aqueous phase, it was mixed with the PIP monomer. More precisely, 0.01 g of PIP was dissolved in 5.0 mL (~0.2% by mass) of a suspension of H3 at 1 g / L (~0.1% by mass) with a mass ratio H3 / PIP = 1 / 2. After 3 h of magnetic stirring at 300 rpm, the suspension did not present any flocculates visible to the naked eye.The organic phase was prepared by dissolving 0.16 g of TMC in 100 mL of n-hexane (>99%, Sigma-Aldrich), i.e. approximately 0.16% by mass.

[0252] By the vacuum filtration method, the first step of the interfacial polymerization reaction consisted of filtering the aqueous phase (5.0 mL) containing the monomer and nanomaterials onto the PVDF support. The 2 emeThe first step of F IP is the addition of the organic solution containing the second monomer onto the already deposited H3 and PIP layer. For this, 3 mL of organic solution containing the second monomer was added without vacuum filtration onto the membrane surface (in the filtration support) and left in contact for 2 min to allow the polymerization reaction to occur. The excess organic solution was then removed and the membrane was allowed to dry at room temperature. A layer that was uniform to the naked eye, slightly iridescent like the H3 layer without PA, was obtained.

[0253] Example 4

[0254] Application to the recycling of photovoltaic panels

[0255] H3 / PVDF membranes were tested on synthetic solutions and leachates from the treatment of end-of-life photovoltaic (PV) panels. After isolation and grinding of the photovoltaic cells encapsulated in the ethylene vinyl acetate layers, several known leaching steps follow to dissolve the metals in order to separate them. At the end of these steps, a 1.0 mol / L nitric acid solution, containing mainly copper, lead, silver and aluminum ions, is obtained.

[0256] Table 3 specifies the molar concentrations of the four elements in these two solutions. The synthetic solution Synt-1, made from the nitrate salts of the metals given above, was prepared at concentrations close to that of the PV-1 solution, to allow comparative tests.

[0257] [Table 3]

[0258] From the values ​​in Table 3, we observe that: (i) the concentration of copper ions is higher than that of silver ions, by a factor of 38, (ii) the concentration of lead ions is approximately two times lower than that of silver ions and (iii) the concentration of aluminum ions is at trace levels (102 pmol / L). The question then arises whether the H3 membrane has the capacity to reject mainly copper, even at a concentration 10 times higher than that studied previously and in a ratio of ~50 to 1, while allowing the passage of silver and lead, and at what fluxes?

[0259] The PV-1 leaching solution was tested in an osmotic cell with H3 / PVDF membranes of type H3-NC-05-5 mentioned in Table 1 (uncentrifuged H3 phase, 0.500 g / L and 5.0 mL permeate: 1.0 M HNO3). The ion permeation fluxes and selectivities with silver are shown in Figure 19. Data at 48 h and about 10 days of experiment are provided, as well as the results of an experiment with the synthetic solution Synt-1, for comparison.

[0260] We are initially only interested in the separation of the leaching solution after 48 h (graph a in figure 19). We note that the Ag ions + pass through the membrane at a flux of 6.16 mmol.m' 2 .h _1 , despite a much higher concentration of Cu ions 2+, while the latter remain mainly blocked by the membrane. A particularly high selectivity between silver and copper (of 636) is then obtained, as shown in graph b of figure 19. The Pb ions 2+ also pass through the membrane with a molar flux of 0.53 mmol.m' 2 .h _1 , limiting the selectivity between silver and lead.

[0261] With the synthetic solution over 48 h of osmosis, the permeation fluxes of silver and lead ions are reduced compared to the leach solution, by 54 and 89% respectively. Although the initial concentration in the feed is lower by approximately 25% between PV-1 and Synt-1 for both ions, this does not fully explain such a difference in permeation flux. The presence of other species in the leach solution, resulting from the potential dissolution of unanalyzed / monitored species in the spent photovoltaic cells, could lead to a variation in separation performance compared to a synthetic solution.

[0262] After about ten days of testing with the synthetic solution, a stabilization / plateau of the permeation rate of Ag ions +appears, as shown in graph b of Figure 19, which means that the amount of silver in the permeate stagnates. This plateau results in a decrease in the permeation flux of silver between 2 and 10 days of experiment. The permeation fluxes of lead and copper are rather constant over time.

[0263] Study of separation according to the concentration ratio [Cu 2+ ] / [Ag + ]

[0264] Additional leaching steps also subsequently allowed the extraction of lead and aluminum from the previous leaching solution, leaving only silver and copper in the leachate. The concentration ratio [Cu 2+ ] / [Ag +] obtained by this selective leaching of PV is approximately 50. A synthetic solution of a copper / silver mixture at a similar ratio was therefore also prepared and tested with the H3 membranes. In order to study an extreme case of difference in concentrations between copper and silver, to take into account the variability of the composition of the waste, a solution with a ratio [Cu 2+ ] / [Ag + ] of about 4500, fixed arbitrarily, was also used. Table 4 shows the silver and copper concentrations in the two synthetic solutions thus described.

[0265] [Table 4]

[0266] Synthetic solutions Synt-2 and -3, consisting of Cu ions 2+ and Ag + in concentration ratios of approximately 50 and 4500 respectively, were tested with H3 / PVDF membranes of type H3-S-1-7 from Table 1 (H3 phase supernatant, 1.0 g / L and 7.0 mL). In ratio [Cu 2+ ] / [Ag+ ] ~ 50, a first study of the influence of agitation on the kinetics and separation performance was carried out. Indeed, the ion permeation tests in the osmotic cell were all carried out without agitation (SA), except for the test specified in this section. Agitation makes it possible in particular to limit the phenomena of ion concentration polarization on the membrane surface, which can reduce separation performance.

[0267] Comparing the experiments at the ratio of about 50, with (AA) and without stirring (SA), there is first of all an increase in the permeation rate of Ag ions + thanks to the agitation of the permeate and the retentate, without significantly impacting the permeation of Cu ions 2+ The difference in permeation is even more significant after 24 hours, with a permeation rate, and by analogy a permeation flux 46 times higher with the agitation of the osmotic cell.

[0268] Then, comparing the experiments with different concentration ratios in the ionic solution, the permeation rate of silver is lower throughout the experiment with the ratio [Cu 2+ ] / [Ag + ] of about 4500. Conversely, copper ions pass more through the membrane, with a permeation rate of 0.88%. Although this rate is low, the concentration in the ionic solution is particularly high compared to Ag ions + , this permeation rate results in a decrease of approximately one order of magnitude in the Ag / Cu selectivity (selectivity = 35 with the ratio 4500 versus 461 with the ratio 50). At extreme concentration differences, the capacity for separating silver ions and the rejection of copper ions is therefore reduced but remains significant.

[0269] The molar compositions Cm at different times of the three types of experiments carried out were calculated at the permeate and compared to the initial composition (t = 0 h) of the ionic solutions. This molar composition over time is visible in Figure 20. The previous observation at ratio 4500, indicating a decrease in the permeation rate of silver ions and an increase in that of copper, is expressed by a very low proportion of silver ions in the permeate (right part of Figure 20). An enrichment of a factor of 150 of silver is still obtained compared to the feed solution. At ratio 50 (left part of Figure 20), despite an initial composition of the feed approximately 50 times more concentrated in copper, the H3 / PVDF composite membrane allows enriching the permeate with a purity of 84.6% in silver after 24 h of permeation. Thanks to the agitation of the cell, this purity rises to 90.4% of Ag ions + in the permeate.

[0270] Example 5

[0271] Microfluidic device

[0272] A microfluidic experimental platform, suitable for the study of membranes, could be applied to H3-based membranes.

[0273] This microfluidic device is composed of two plates 130 and 140 made of poly(methylmethacrylate) (PMMA), which enclose between them the membrane 10 to be tested by screws and silicone glue (RS). The latter ensures the sealing of the chip on its edges. Each PMMA block is etched with either a 17 cm long serpentine channel, shown in Figure 21, images a to c, or a 2 cm long single channel, visible in Figure 21, images d and e, both 1 mm wide and 0.2 mm deep. The volume of the microfluidic channel is then 34 pL for the serpentine channel and 4 pL for the single channel. The membrane 10, placed between the two PMMA blocks, then separates the two channels. The serpentine channels or single channels form the first and second compartments 110 and 120. The effective separation area of ​​the membrane 10 is 1.7 cm 2 for the serpentine chip and 0.2 cm 2 for the single chip.

[0274] To circulate solutions in the channels, two syringes, placed on a syringe pump, are connected to the inlets of the microfluidic chip by PTFE tubes with an internal diameter of 0.45 mm. Adapted 150 tips, glued with epoxy glue (Katiobond 4594) on the chip (see Figure 21, images b, c and e), allow the connection between the microfluidic cell and the tubes. Glass vials, closed by septum caps and put at atmospheric pressure, are connected to the outlets of the chip by the PTFE tubes to collect the liquids at the outlet.

[0275] This microfluidic assembly allows the study of ion separation / permeation by osmosis, in tangential flow, through a membrane. As for osmosis separation in an osmotic cell (H-cell, batch), the membrane selectively allows certain ions to pass through compared to others, initially present in a feed solution. The latter, introduced into the chip using the syringe pump, circulates on one side of the membrane, while a permeate solution circulates on the other side. The separation can be carried out in co-current or counter-current by reversing the inlet and outlet on a PMMA block.

[0276] The syringe pump allows the inlet flow rate of the two solutions (ionic solution and permeate) to be modified to study the kinetics of ion separation. The single channel, with a smaller volume, allows the study of membrane separation at low contact times (< 1 min). Table 5 lists the applied flow rates and associated contact times with the two microfluidic cells. At flow rates above 20 pL / min, with both channel geometries, leakage problems at the test cell were observed, preventing the study at lower contact times.

[0277] [Table 5]

[0278] Experiments were carried out with H3 / PTFE (polytetrafluoroethylene) hybrid membranes with the serpentine cell, at the different flow rates given in Table 5, the porous PTFE support has pores of 0.02 pm (Cobetter brand, porosity of 70%) and a thickness of 30 pm. It is hydrophobic.

[0279] Since this support is hydrophobic, while the H3 nanosheets are suspended in water, adjustments to the vacuum filtration membrane fabrication protocol (described previously) were made. First, before depositing the porous PTFE support on the filtration support, the porous support was immersed in an ethanol solution (96% vol., VWR) for 5 min. Ethanol allows the porous support to be wetted and is miscible in water. Then, to aid the filtration of the colloidal H3 suspension, 1 mL of 96% vol. ethanol was added to the latter. The mixture, prepared in a centrifuge tube, was vigorously shaken manually and then on a vortex mixer for a few seconds. The ethanol-wet PTFE porous support was then deposited on the filtration support and the H3 / ethanol mixture was introduced into the filtration support on the porous support.The vacuum pump (model ME 4C NT Vacuubrand, absolute pressure = 80 torr) was started 10 min after introduction of the mixture, to allow contact / impregnation time between the mixture and the porous support.

[0280] The parameters of the colloidal suspension for the membranes studied in this section are as follows: H3 phase “supernatant” at 1.0 g / L. The volume of suspension to be filtered was set at 5 mL, to limit the filtration time while maintaining good membrane selectivity.

[0281] Separation of silver ions from other ions

[0282] For the separation experiments, the application to WEEE recycling was chosen, i.e. the separation of metal ions in leachates. For this, the same chemicals previously used were used. Typically, a solution of the nine metal ions (Ag + , Pb 2+ , Li + , Cu 2+ , Neither 2+ , Co2+ , Mn 2+ , Fe 3+ and Al 3+ ) at 10.0 mmol / L in 1.00 mol / L nitric acid was prepared as the feed solution, along with a 1.00 mol / L nitric acid solution for the permeate side. 0, 10 mol / L and 2.00 mol / L HNO3 solutions were also prepared and their use is described subsequently.

[0283] First, the membrane is cut and placed on one of the PMMA blocks of the microfluidic chip, so as to cover all the channels (coil or single). A space is left free around the membrane on the chip to deposit a thin layer of silicone glue. The layer of nanomaterials faces the channel on the ionic solution side.

[0284] Since the support is hydrophobic and the input solutions are aqueous (ionic solution and permeate sides), a first step of impregnation / wetting of the membrane with ethanol is necessary. For this, the syringe that feeds the permeate solution side, i.e. the porous PTFE support side, was filled with 96% vol. ethanol and the other syringe was filled with the ionic solution containing the metal ions.

[0285] The solutions at the inlet and those collected at the outlet of the microfluidic chip were analyzed by ICP-OES, to determine the ion concentration. The exact masses delivered by the syringe pump at the inlet of the chip were measured by weighing, using a precision balance, at the different flow rates applied for a given volume setpoint to be delivered (typically 500 pL). Thus, the exact volumes delivered were known. In the same way, the vials at the outlet of the chip were previously tared and then weighed after each experiment, to determine the exact volume collected, permeate and retentate sides. Thus, the molar permeation rate of the ions could be calculated according to the equation below, adapted to the microfluidic device. where Pi (%) is the permeation rate of ion i, Ani, p (mmol) is the variation in the amount of matter of ion i in the permeate between the outlet and the inlet of the chip, ni, r , e(mmol) is the amount of material of ion i entering the chip on the retentate side, Ci, p , s and Ci, p , e (mmol / L) are the molar concentrations of ion i at the outlet and inlet of the chip on the permeate side respectively, V p , s and V p , e are the volumes of solutions on the permeate side, collected at the outlet and dispensed at the inlet respectively, Ci, r ,e (mmol / L) is the molar concentration of ion i at the chip inlet on the retentate side and V r , e is the volume of solution dispensed at the inlet on the retentate side.

[0286] For each study, at each change in operating conditions (input solution, flow rate), the solution at the outlet of the microfluidic chip was collected for analysis only after reaching the permanent (or stationary) regime: this permanent regime can in fact be considered reached, according to theory, after approximately five passage times (-residence times) T of the solution in the microfluidic chip on either side of the membrane, i.e. at t ~ 5 XT = 5 XQ x V m (where Q is the solution flow rate in pL / min and V m is the volume of a microfluidic channel in pL). To ensure that steady state is reached and to take into account the volume of liquid in the pipes, a time approximately 20% greater than 5T was applied.

[0287] For this study, the serpentine chip was used at a constant flow rate of 20 pL / min on both the permeate and retentate sides, giving a contact time of 1.7 min. When steady state was considered reached, a delivered volume setpoint of 500 pL was given to the syringe pump. Four successive separations (Spl, Sp2, Sp3 and Sp4) of 500 pL were chained together by quickly changing (a few seconds) the output vials after each 500 pL delivered to avoid losing steady state between each separation. The graph providing the ion permeation rate at each separation is given in Figure 22.

[0288] Compared with the results obtained in the osmotic cell of Example 1, similar separation performances were obtained with an H3 / PTFE membrane and the microfluidic device. Indeed, a high permeation rate of silver (48.4 to 49.4%) was obtained against a permeation rate between 1.2 and 1.4% for lead and less than 0.5% for the other ions. A high selectivity between Ag ions + and the other ions is thus observed, calculated at 38 with Pb 2+ and 351 with Cu 2+ for example, on average over the four separations.

[0289] Then, by comparing the ion permeation rates between each separation, it is possible to observe a good general stability of the separation performances. Indeed, the permeation rate of Ag ions + remains stable in the uncertainty interval, as do the other ions, except for the Al ions 3+. These latter present an unexplained increase in the permeation rate of +65% between the 3 eme and the 4 eme separation (respectively 0.23 and 0.38%). Despite this variation, these results show the stability of the membrane and the selective layer of nanomaterials after successive separations in tangential flow.

[0290] Study of separation kinetics

[0291] As mentioned at the beginning of this section, the microfluidic device allows the study of ion permeation kinetics, by performing separation tests at several flow rates and therefore at different contact times. To study a wide range of contact times, both the serpentine and single chips were used for this study (see Table 5). For each separation experiment, a volume setpoint of 500 pL was applied. At each change of flow rate, a steady-state waiting time was respected. The ion permeation rates obtained at the different contact times are graphically represented in Figure 23.

[0292] Kinetic profiles similar to those obtained in Example 1 are observed for all ions with H3 / PTFE membranes in a microfluidic cell in tangential flow. The permeation of silver ions is rapid while that of lead ions, possibly slowed down by the chemical exchange reaction, is slower. A plateau in the silver permeation rate, and consequently in the silver concentration in the permeate, appears from a contact time of 1.7 min. For a contact time of 34 min, all ions have a higher permeation rate than at Contact = 6.8 min; this increase is less marked for Ag ions. + , which causes a decrease in selectivity and therefore in the separation capacities of the membrane. An optimum to maximize the selectivity between Ag ions +and other ions while having a high concentration of silver in the permeate (reaching the plateau) would be a contact time between 1.7 and 3.4 min. This device therefore makes it possible to highlight the optimal contact times in order to maximize the separation of the ions.

[0293] For a comparable kinetic study performed in the osmotic cell of Example 1, approximately 200 h of experiment are required to achieve an equivalent profile up to tcontact ~ 6.8 min. Whereas in the microfluidic cell in tangential flow, this kinetic study required only approximately 6.5 h of cumulative experiments (up to tcontact = 6.8 min). In addition, approximately 84 mL are required for a study with the H-cell, while only 10 mL of solution were used with the microfluidic chip, including transient periods. The microfluidic device therefore allows minimizing both the experiment time and the amount of liquid waste generated.

[0294] Comparison of co-current and counter-current separation

[0295] Countercurrent permeation experiments were performed at 20 pL / min (tcontact = 1.7 min) (volume setpoint: 500 pL) and the permeation rates obtained were compared with those in co-current in Figure 24, graph a. The stability of the membrane with a succession of separation tests was also confirmed in countercurrent.

[0296] The permeation rate of Ag ions + is first of all higher in counter-current compared to co-current operation; it is higher than a value of 50%, which means that the concentration on the permeate side is higher than that on the retentate side. Conversely, Pb ions 2+pass less through the membrane in countercurrent. These initial observations reflect an increase in selectivity between silver and lead in countercurrent, as shown in Figure 24, graph b. For the other ions, their permeation rate is higher in countercurrent, which leads to a decrease in selectivity between silver and the other ions.

[0297] Example 6 Synthesis of K3Sb3yBi3(i- y )P2Oi4

[0298] The inventors have demonstrated that the invention is not limited to membranes with antimony and an x ​​other than 1. The following phases have been synthesized in powder form:

[0299] - K3Sb3P20i4 ;

[0300] K3Sb2,7Bi0,3P2Oi4, hereinafter referred to as “K3Biio%” and K3Sb2,25Bio,7sP20i4, hereinafter referred to as “K3Bi25%”.

[0301] The corresponding diffractograms are respectively in figures 25, 26 and 27.

[0302] It is clearly apparent on these diffractograms from the first-order peaks that the inter-layer distance is greater in the presence of bismuth.

[0303] Comparison of permeation rates for an H3Sb3 membrane and for an H3BilO% membrane

[0304] The permeation rates (in %) of each ion for an ILSb membrane and for a PLBi membrane were determined in the table below.

[0305] These results show that adding bismuth increases both the pore size and the inter-layer distance, allowing ions to pass through more easily. It is then possible to control ion permeation by varying the amount of bismuth in the phase.

[0306] Similarly, a phase containing arsenic instead of bismuth, according to the K3Sb3(i- y)P2kAs2(ik)Oi4 with k between 0 and 1, 1 being preferably excluded, or in combination with bismuth has a reduced pore size and interlayer distance compared to that with bismuth or with antimony alone, thus increasing the selectivity for silver.

[0307] Thus, by modulating the amount of bismuth and arsenic in the phase, it is possible to adjust the permeation of ions, particularly silver and lead.

[0308] The invention is not limited to the embodiments and examples which have just been described. For example, the membrane may comprise a porous support other than those described, the device may have a shape other than those described or the method may comprise steps additional to those described above.

Claims

Claims 1. Membrane (10) comprising: a porous support (30) comprising two opposite main surfaces (32, 34), a selective ion transfer layer (20) comprising sheets (22) of a nanomaterial extending over one of the two main surfaces (32, 34) of the porous support, the nanomaterial being of formula: XMN014 M being of formula As3(i- y -z)Sb3yBi3z,, and N being of formula P2kAs2(ik), y, z and k being numbers varying from 0 to 1 with y+z less than or equal to 1, X being of formula H3(i- X )A3 X , A being an alkali, an ammonium cation or a cation derived from a water-soluble hydroxide salt or a mixture thereof, x being a number ranging from 0 to 1.

2. Membrane according to claim 1, in which the selective ion transfer layer (20) has an average surface quantity of nanomaterials greater than or equal to 0.3 mmol / m 2, better greater than or equal to 0.5 mmol / m 2 , even better greater than or equal to 0.6 mmol / m 2 .

3. Membrane according to claim 1 or 2, in which the selective ion transfer layer (20) has a thickness in the dry phase at a temperature of 20°C greater than or equal to 10 nm, better still greater than or equal to 15 nm, even better still greater than or equal to 20 nm.

4. Membrane according to any one of the preceding claims, in which A is chosen from lithium, sodium, potassium, rubidium, cesium, ammonium cations such as tetramethyl, tetraethyl, tetrabutyl or tetrapropyl ammonium, or molecular (or ionic) cations existing in the form of a water-soluble hydroxide salt or a mixture thereof.

5. Membrane according to any one of the preceding claims, in which the selective ion transfer layer comprises more than 25%, better still more than 30%, even better still more than 50%, preferably more than 80%, even better still more than 90%, by mass of nanomaterials.

6. Device (100) comprising an ion transfer unit comprising a first and a second compartment (110, 120) separated from each other by a membrane (10) according to any one of the preceding claims.

7. Device according to claim 5, comprising a plurality of ion transfer units (100a, 100b, 100c) each comprising a first and a second compartment (110a; 12a, 110b; 12b, 110c; 120c) separated from each other by a membrane (10) according to any one of claims 1 to 5, the ion transfer units (100a, 100b, 100c) being connected to each other in series, in particular the outlet of one of the first and second compartments of the upstream transfer units being connected to the inlet of one of the first and second compartments of the downstream transfer units.

8. A method of selective ion transfer comprising the steps of: providing a device (100) according to claim 5 or 6 or an ion transfer unit comprising a first and a second compartment (110, 120) separated from each other by a membrane (10) according to any one of claims 1 to 5, inserting an ionic solution (SI) comprising a first and a second different ion species into the first compartment (110), the ionic solution being in contact with a main face (12) of said membrane (10) in said first compartment (110),and transferring for a predetermined duration at least a portion of the ions of said ionic solution (SI) through said membrane (10) to said second compartment (120) with a selectivity S of the first species of ions with respect to the second species of ions strictly greater than 1 so as to form a permeate in said second compartment (120) and a retentate in said first compartment (110)., 9. Method according to claim 8, in which the transfer of ions during the predetermined duration through said membrane to said second compartment is done with a selectivity of the first species of ions compared to the second species of ions strictly greater than 2, even better strictly greater than 10, better still greater than or equal to 100.

10. Method according to claim 8 or 9, in which the ionic solution (SI) is an acid solution, in particular having a pH less than or equal to 7, better still less than or equal to 3, better still less than or equal to 1, even better still less than or equal to 0, even better still less than or equal to -0.

6.

11. Method according to any one of claims 8 to 10, in which the permeate (Pe) obtained has a molar composition (Cm) in ions of the first ion species enriched by a factor greater than 5, better than 10, better than 50, even better than 100, even better than 1000, relative to the molar composition in ions of the first ion species of the ionic solution (SI) inserted in the first compartment.

12. Method according to any one of claims 8 to 11, in which the ionic solution (SI) comprises silver ions and the permeate (Pe) obtained has a molar composition of silver ions enriched by a factor greater than 5, better still greater than 50, even better still greater than 100, even better still greater than 1000, relative to the molar composition of silver ions of the ionic solution inserted into the first compartment.

13. Method according to any one of claims 8 to 12, in which the ionic solution (SI) comprises silver ions and lithium, lead, copper, aluminum iron, nickel, manganese, cobalt, sodium, potassium, rubidium, cesium, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine ions, the transfer of the ions during the predetermined time through said membrane to said second compartment being carried out with a selectivity of the silver ions with respect to at least one, better each, of the copper, aluminum iron, nickel, manganese, cobalt ions, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium,holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine greater than or equal to 2, better still greater than or equal to 10, better still greater than or equal to 100, even better still greater than or equal to 500 and with a selectivity of silver ions with respect to at least one, better still each, of the lithium, lead and / or sodium ions strictly greater than 1, better still greater than or equal to 5, even better still greater than or equal to 10., 14. Method according to any one of claims 8 to 13, in which the ionic solution (SI) comprises hydrogen ions and other ion species among lithium, lead, silver, copper, iron, nickel, aluminum, manganese, cobalt, sodium, potassium, rubidium, cesium, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine, the transfer of ions during the predetermined duration through said membrane to said second compartment being carried out with a selectivity of hydrogen ions with respect to at least one, better each, of the other aforementioned ion species strictly greater than 2, better greater than or equal to 10, better greater than or equal to 100, even better greater than or equal to 500.

15. A method according to any one of claims 8 to 11, wherein the ionic solution (SI) is substantially free of silver ions and comprises lithium, lead, sodium, potassium, rubidium or cesium ions and other ion species among copper, iron, nickel, aluminum, manganese, cobalt, calcium, magnesium, barium, zinc, cadmium, chromium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, tantalum, gold, palladium, zirconium, strontium, platinum, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium, fluorine, chlorine and / or bromine, the transfer of the ions during the predetermined time through said membrane to said second compartment being done with a selectivity of the lithium ions with respect to at least one, better each, of the other species of the aforementioned ions greater than or equal to 2, better still greater than or equal to 10, even better still greater than or equal to 20.

16. Method according to any one of claims 8 to 15, comprising the insertion of a permeate solution (SP) into the second compartment (120), the transfer of at least a portion of the ions from the ionic solution through the membrane (10) being carried out by osmotic transfer into the permeate solution (SP), the permeate being in particular acidic with a pH difference with the ionic solution (SI) less than or equal to 2.

17. Method according to any one of claims 8 to 16, comprising stirring the ionic solution (SI) and / or the permeate solution (SP) during the transfer of the ions.

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