Method for preparing a material useful for lithium extraction, material and uses thereof

Abstract

The present invention relates to a method for preparing a material capable of extracting lithium, which comprises the steps consisting in: (a) preparing a geopolymer mixture by mixing together (i) an activation solution comprising at least lithium hydroxide and (ii) an aluminosilicate source; (b) allowing the geopolymer mixture prepared in step a) to cure, whereby a geopolymer matrix material is obtained; and (c) washing the geopolymer matrix material obtained in step b), whereby at least a portion of the lithium cations (Li+) comprised in the geopolymer matrix material are removed and a material capable of extracting lithium is obtained. The present invention also relates to the material thus obtained and to the uses thereof.

Description

[0001] PROCESS FOR PREPARING A MATERIAL USEFUL FOR LITHIUM EXTRACTION, SAID MATERIAL AND ITS USES

[0002] TECHNICAL FIELD

[0003] The present invention relates to the field of lithium extraction and in particular to the field of lithium extraction involving solid materials.

[0004] Thus, the present invention provides a process for preparing a solid material with a geopolymer matrix optionally comprising lithium-selective adsorbents, the material thus prepared and its uses, in particular for the extraction of lithium.

[0005] STATE OF THE PRIOR ART

[0006] Demand for lithium has increased significantly over the past decade due to the growing use of lithium-ion batteries. This growth is driven by the electrification of transportation and environmental regulations aimed at reducing the use of fossil fuels.

[0007] Today, the two primary lithium resources are rocks such as spodumene, epidolite, and petalite, and brines from salt flats found in many countries such as Argentina, Bolivia, and Chile. Geothermal waters also contain significant amounts of lithium and are being studied on a pilot scale as a lithium resource. Lithium-ion battery recycling processes or manufacturing waste are also secondary lithium resources.

[0008] Concerning the "liquid" mineral that represents the water from salt flats or geothermal sources, the salinity of these environments is very high and can reach up to a hundred g / L.

[0009] One of the current challenges is therefore to develop robust and efficient technologies for extracting lithium from these aqueous media. Solid support extraction technology is well suited to extracting an element present in low concentration in a saline environment. To do this, it is necessary to choose a lithium-selective material or sorbent and to shape this material so that it can be used in a fixed bed process accepting high treatment flow rates (up to several m 3 / h).

[0010] For the extraction of lithium contained in geothermal brines, it is envisaged to insert a lithium extraction loop on the geothermal loop. This process must necessarily avoid the physicochemical alteration of the flow (i.e. limitation of inputs and outputs) in order not to significantly modify the composition of the brine before its reinjection. Today, there are several projects for the recovery of lithium from geothermal brines, but none on an industrial scale to date (pre-industrial scale for Eramet). Concerning the extraction processes on suitable solid support, the extraction of lithium from brines can be done using columns packed with cationic exchange microfibers with pilot scale tests. In patent application FR3087356 A1 [1], Geolith uses fibers from the company Ajelis (MECALICAPT®) which are organic materials functionalized by organic cation exchange groups.The use of organic fibers has disadvantages when used at high temperatures, including a risk of degradation of the organic part.

[0011] Eramet uses solid mineral materials such as lithium-charged aluminum trioxide as precursor materials for the selective extraction of lithium, with a prior proton exchange step, in the context of salt flat exploitation (Argentina), and is considering using these materials for geothermal sources, or even for juices from battery recycling. While the sorption properties of these materials are effective in powder form, one of the difficulties arises from their shaping for a continuous fixed-bed process.

[0012] Patent application FR3051787 A1 [2] proposes a process for preparing a crystallized solid mineral material selectively extracting lithium in extruded form, with good mechanical strength and good cohesion for use in columns, without the presence of fine particles. The manufacturing process uses a suspension which, after heat treatment, is extruded and then dried, whereby a material of formula (LiCl) is obtained. x .Al(OH)3, n H2O with n between 0.01 and 10 and x between 0.4 and 1. However, this process does not allow the production of a porous material optimizing the accessibility of the adsorbent sites to the flow passing through the bed and, consequently, the interior of the grains cannot be accessible, reducing the extraction capacity and kinetics and therefore degrading the performance in fixed bed processes.

[0013] Patent application FR3015458 A1 [3] has the same objective of shaping a material suitable for a column process and presents the use of an alumina-type binder followed by extrusion and a drying phase with a synthesis process similar to that described in patent application FR3051787 A1 [2]. In this case also, the porosity of the material is limited, implying that only the external part of the extrudates is used when brought into contact with the column flow, which can reduce the performance of the materials. Finally, in these two patent applications, the shape obtained is not very controllable during the drying step and the shaping is limited to the formation of extrudates.

[0014] Geopolymer-based materials have also been proposed for the separation of metal or metalloid ions such as metal or metalloid cations from a liquid medium containing them.

[0015] Thus, international application WO 2016 / 173950 A1 describes the functionalization of monolithic geopolymer foam for the catalysis or decontamination of effluents in fixed bed treatment processes [4]. The synthesis is carried out in two stages: the foam is first prepared and then its functionalization is carried out in a second stage. The overall synthesis of the material is complicated, which can make its transposition to the industrial scale complex. Furthermore, with such a synthesis, the quantity of adsorbent that can be introduced into the material is limited. Indeed, the selective adsorbents are only lined on the surface of the macropores of the foam and not present in the mesoporous walls of the latter, which can limit the contact surface with the effluent and therefore the total capacity of the material.Furthermore, the functionalization method described in this application [4] only applies to nanoparticles of metal coordination polymers with CN bonds which are not suitable for lithium extraction. Furthermore, this synthesis route aims to use the foams in their monolithic form, in particular directly as a “straight” decontamination column.

[0016] International application WO 2021 / 152248 A1 finally describes the synthesis of a selective adsorbent-geopolymer composite comprising an interconnected macroporous network [5]. To create the macroporous network, the synthesis involves the formulation of an emulsion comprising precursors of the material as well as the elimination of the oily phase once the material has hardened. The synthesis process remains complicated, making it difficult to industrialize. Furthermore, this synthesis route results in the formation of macropores with sometimes thin walls and sharp junctions. These walls thus have weakened mechanical strength, particularly during the passage of an effluent, which can lead to their degradation and the formation of fine particles likely to clog a column.

[0017] Given the growing demand for lithium, the inventors set themselves the goal of proposing a lithium-selective mineral adsorbent that could be used in a fixed bed, with good properties in terms of capacity, flow rate (kinetics) and optimized accessibility to "sorbent" sites. Furthermore, this material must be prepared by an efficient, simple and easily industrialized process.

[0018] STATEMENT OF THE INVENTION

[0019] The present invention makes it possible to achieve the goal set by the inventors since the latter propose to prepare a geopolymer matrix material in which this matrix serves as a lithium extractant in order to have a high capacity but can also serve as a mesoporous binder to incorporate a more selective lithium adsorbent.

[0020] Indeed, synthesized in the presence of lithium, the structure of the geopolymer matrix material is adapted to be partly lithium selective and allows a high lithium extraction capacity. In addition, the possible addition of an ion exchanger, i.e. a lithium-selective adsorbent within this geopolymer matrix material provides increased selectivity towards lithium in the conditions of specific effluents to be treated, particularly highly saline effluents. The mesoporous structure of the geopolymer matrix allows accessibility of the adsorbent particles dispersed within it and therefore extremely rapid sorption kinetics and optimized performance. In addition, the mechanical strength of the geopolymer matrix is ​​suitable for use in a fixed bed.The size of the ion exchangers, their dispersion in the geopolymer matrix and the mesoporosity of the latter therefore make it possible to significantly improve the kinetic properties of ion exchange and therefore the shape of the breakthrough curves.

[0021] Finally, note that the process for preparing the geopolymer matrix material according to the invention is a conventional sol-gel process, easy to implement and industrialize. Furthermore, the geopolymer matrix material according to the invention can be easily shaped in different ways such as 3D printing, foaming, extrusion, grinding with sieving to make it suitable for a column process.

[0022] Thus, the present invention relates to a method for preparing a material capable of extracting lithium, comprising the steps of: a) preparing a geopolymeric mixture by mixing together (i) an activation solution comprising at least lithium hydroxide and (ii) an aluminosilicate source; b) allowing said geopolymeric mixture prepared in step a) to harden, whereby a geopolymeric matrix material is obtained; c) washing the geopolymeric matrix material obtained in step b) whereby at least a portion of the lithium cations (Li + ) that comprise the geopolymer matrix material are eliminated and a material capable of extracting lithium is obtained.

[0023] By "geopolymer matrix" or "geopolymer" is meant in the context of the present invention a solid, inorganic and porous material in the dry state, obtained following the hardening of a mixture containing finely ground materials (i.e. the aluminosilicate source) and a saline solution (i.e. the activation solution), said mixture being capable of setting and hardening over time. This mixture can be referred to as "geopolymeric mixture", "geopolymer mixture", "geopolymeric composition" or even "geopolymer composition". The hardening of the geopolymer is the result of the dissolution / polycondensation of the finely ground materials of the geopolymeric mixture in the saline solution such as a high pH saline solution (i.e. the activation solution).

[0024] More specifically, a geopolymer or geopolymer matrix is ​​an amorphous alumino-silicate inorganic polymer. Said polymer is obtained from a reactive material containing essentially silica and aluminum (i.e. the alumino-silicate source), activated by a strongly alkaline solution, the solid / solution mass ratio in the formulation being low. The structure of a geopolymer is composed of a Si-O-Al network formed of silicate (SiO4) and aluminate (AIO4) tetrahedra linked at their vertices by sharing oxygen atoms. The substitution of a silicon atom (valence +IV) by an aluminum atom (valence +111) results in a charge deficit compensated by one or more charge compensating cation(s) also called compensation cation(s) which compensate for the negative charge of the AlO4' complex. Compensating cations are usually alkali metal cations and typically Na cations + and K + .

[0025] The high pH saline solution, also known in the field of geopolymerization as "activation solution", is a strongly alkaline aqueous solution which may possibly contain silicate components chosen in particular from the group consisting of silica, colloidal silica and vitreous silica.

[0026] The terms "activating solution", "high pH saline solution" and "strongly alkaline solution" are, in the present invention, similar and can be used interchangeably.

[0027] The activation solution used in the context of the invention is an aqueous solution, which means that the solvent it contains is water. By "water", we mean, in the context of the invention, tap water, deionized water (or demineralized water), distilled water, ultrapure water (18.2 MQ) or a mixture thereof.

[0028] By "strongly alkaline" or "high pH" is meant a solution whose pH is greater than 9, in particular greater than 10, in particular greater than 11 and, more particularly, greater than 12. In other words, the activation solution has an OH' concentration greater than 0.01 M, in particular greater than 0.1 M, in particular greater than 1 M and, more particularly, between 5 and 20 M.

[0029] In addition, the activation solution includes the compensating cation or the mixture of compensating cations in the form of an ionic solution or a salt.

[0030] In the context of the present invention, since the activation solution used contains lithium hydroxide (LiOH), all or part of the compensation cations are lithium cations (Li +). Typically, the amount of LiOH in the activation solution is between 3% and 6% by mass, in particular between 4% and 5% by mass and, in particular, of the order of 4.6% (i.e. 4.6% ± 0.1%) by mass relative to the total mass of the activation solution.

[0031] Furthermore, the activation solution used in the context of the invention may also contain one or more element(s) chosen from the group consisting of sodium silicate (NazSiOg), potassium silicate (K2SiO2), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (CafOHh), cesium hydroxide (CsOH), sodium oxide (Na2O), lithium oxide (LÎ2O) and a mixture thereof. In a particular embodiment, the activation solution used in the context of the invention contains sodium oxide (Na2O) and lithium oxide (U2O). In a more particular embodiment, the activation solution is an aqueous solution containing silica (SiO2), sodium oxide (Na2O), lithium oxide (U2O) and lithium hydroxide (LiOH). The experimental part below provides an example of an activation solution belonging to such an embodiment.

[0032] The expressions "aluminosilicate source" and "reactive material containing essentially silica and aluminum" are, in the present invention, similar and can be used interchangeably.

[0033] The reactive material containing essentially silica and aluminum that can be used to prepare the geopolymer matrix used in the context of the invention is advantageously a solid source containing amorphous aluminosilicates. These amorphous aluminosilicates are in particular chosen from natural aluminosilicate minerals such as illite, stilbite, kaolinite, pyrophyllite, andalusite, bentonite, kyanite, milanite, grovenite, amesite, cordierite, feldspar, allophane, etc.; calcined natural aluminosilicate minerals such as metakaolin; synthetic glasses based on pure aluminosilicates; aluminous cement; pumice; calcined by-products or residues of industrial exploitation such as fly ash and blast furnace slag respectively obtained from the combustion of coal and during the transformation of iron ore into cast iron in a blast furnace; and mixtures thereof.In a particular embodiment, the aluminosilicate source used is metakaolin.

[0034] Taking into account any silicate components that the activation solution may contain, the quantity of aluminosilicate source(s) is such that the SiC / A Ch molar ratio in the geopolymer matrix of the material obtained in step b) and therefore of the material capable of trapping lithium prepared according to the method of the invention is between 2.3 and 4.3, in particular between 3.0 and 3.6 and, in particular, of the order of 3.3 (i.e. 3.3 ± 0.1). This molar ratio can be obtained by dissolving the geopolymer matrix material in hydrofluoric acid.

[0035] With such a SiC / AhOa molar ratio, it is possible to have a quantity of charge compensating cations (Li+) making it possible to obtain an optimal intrinsic lithium trapping capacity for the material prepared according to the process of the invention.

[0036] Furthermore, the quantity of water in the activation solution is between 65% and 80% by mass, in particular between 70% and 75% by mass and, in particular, of the order of 72% (i.e. 72% ± 1%) by mass relative to the total mass of the activation solution.

[0037] Note that the combination of such a quantity of water and the SiOz / AhOa molar ratio as previously defined makes it possible to obtain a geopolymer matrix material whose mesopore size is optimal for trapping lithium.

[0038] As a reminder, a geopolymer or a geopolymer matrix has an intrinsic mesoporous porosity of the order of 5 to 30% by volume compared to the total volume of the geopolymer, the latter can also have unconnected macropores, this porosity resulting mainly from the geopolymerization process. In other words, a geopolymer has, due to its preparation process, connected mesopores and possibly unconnected macropores.

[0039] By "mesopores" is meant pores or voids having an average diameter of between 2 and 50 nm and in particular between 2 and 20 nm. In the context of the present invention, the optimal mesopore size for trapping lithium is typically between 2 and 10 nm and in particular centered around 5 nm.

[0040] Step a) of the process according to the invention is a conventional step in the preparation of geopolymers. Typically, it comprises the following sub-steps: i) preparing an activation solution comprising at least lithium hydroxide as previously defined, ii) adding to the solution obtained in sub-step i) at least one aluminosilicate source and mixing the whole, whereby a geopolymeric mixture comprising at least lithium hydroxide is obtained.

[0041] In sub-step ii), the alumino-silicate source(s) is / are added to the activation solution comprising at least lithium hydroxide in one go or in several goes. Once the alumino-silicate source(s) has / have been added to the activation solution, the solution or dispersion obtained is mixed using a mixer, a magnetic stirrer, a magnetic bar, an ultrasonic bath or a homogenizer. The mixing / kneading in sub-step ii) of the method according to the invention is carried out manually or mechanically at a sustained speed. By "sustained speed" is meant, in the context of the present invention, a rotation speed of the rotor of the mixer or magnetic stirrer, greater than or equal to 1000 rpm, in particular greater than or equal to 1500 rpm and, in particular, greater than or equal to 2000 rpm. Advantageously, this agitation is carried out using a magnetic stirrer or a mixer.Any mixer known to those skilled in the art can be used in the context of the present invention. By way of non-limiting examples, mention may be made of a NAUTA® mixer, a HOBART® mixer, a HENSCHEL® mixer and a HEIDOLPH® mixer.

[0042] The experimental part below gives, by way of illustration, an example of preparation of such a geopolymeric mixture. Typically, step a) of the process and in particular the sub-steps i) and ii) which it comprises are carried out at a temperature between 10°C and 40°C, advantageously between 15°C and 30°C and, more particularly, at room temperature (i.e. 23°C ± 5°C) for a duration greater than 1 min, in particular between 2 min and 15 min and, in particular, between 3 min and 5 min.

[0043] Step b) of the process according to the invention consists of subjecting the geopolymeric mixture obtained in step a) to conditions allowing it to harden.

[0044] Any technique known to those skilled in the art for curing a geopolymeric mixture can be used during the curing stage of the process.

[0045] The conditions allowing hardening during step b) of the method according to the invention advantageously comprise a curing step optionally followed by a drying step. The curing step can be carried out at a temperature between 10°C and 80°C, in particular between 20°C and 60°C and, in particular, between 30°C and 40°C and can last between 1 and 40 days, or even longer. Alternatively, the conditions allowing hardening during step b) can comprise a curing step at a temperature below 30°C and, in particular, at room temperature and can last between 18 h and 150 days and in particular between 24 h and 120 days and, in particular, of the order of 3 months (i.e. 3 months ± 5 days).Whatever the temperature at which the curing step is carried out, the latter can be done in the open air, under water, in various airtight molds, by humidification of the atmosphere surrounding the geopolymeric mixture or by application of an impermeable coating on said geopolymeric mixture.

[0046] Step c) of the method according to the invention is implemented to eliminate at least part of the compensation cations and in particular at least part of the lithium cations (Li + ) which comprises the geopolymer matrix material.

[0047] In a first embodiment, step c) may consist of bringing the geopolymer matrix material into contact with a washing solution and stirring the assembly for a period of between 10 seconds and 5 minutes, in particular between 20 seconds and 3 minutes and, in particular, of the order of 30 seconds (i.e. 30 seconds ± 5 seconds). After removing the washing solution containing compensation cations, it is possible to repeat the step of bringing into contact with a new washing solution and stirring at least one, at least two, at least five, at least ten or even at least fifteen times. The washing solution may have an identical or different composition for two consecutive washes. In this first embodiment, the concentration of Li +in the washing solution recovered after contact with the geopolymer matrix material and agitation makes it possible to assess the progress of the washing and the need or not to repeat the contact with a new washing solution. In a second form of implementation, step c) may consist of placing the geopolymer matrix material in a column and circulating a washing solution through this column. This circulation is typically carried out continuously. By monitoring the Li concentration + at the column outlet, the progress of the washing can be assessed.

[0048] Typically, the washing solution that can be used for both the first embodiment and the second embodiment as defined above can be a neutral or acidic aqueous solution, optionally concentrated in sodium. An acidic aqueous solution that can be used in the context of the invention is an aqueous solution whose pH is between 4 and 6. A concentrated aqueous sodium solution that can be used in the context of the invention comprises a concentration of [Na + ] greater than or equal to 0.01 M. In a particular embodiment, the washing solution is water as previously defined and in particular deionized water.

[0049] Advantageously, following this washing step and before any use of the material capable of extracting lithium thus obtained, the latter is subjected to drying. This can be done at a temperature between 40°C and 90°C, in particular between 50°C and 85°C and, in particular, between 60°C and 80°C and can last between 4 hours and 5 days, in particular between 8 hours and 2 days and, in particular, between 10 hours and 15 hours.

[0050] As previously mentioned, the geopolymer matrix material prepared according to the method of the invention can easily be shaped. This shaping can take place before and / or after obtaining this geopolymer matrix material, i.e. before and / or after step b) of the method according to the invention. In a first embodiment, the geopolymer matrix material prepared according to the method of the invention is in the form of a macroporous monolith with connected macropores. In other words, the shaping used in this first embodiment aims to obtain a monolithic geopolymer matrix material in which the geopolymer matrix is ​​mesoporous and macroporous, with connected macropores. By "macropores" is meant pores or voids having an average diameter greater than 50 nm and in particular greater than 70 nm.The mesopores in the geopolymer matrix of the material obtained following this first embodiment are as previously defined.

[0051] The skilled person knows different techniques for obtaining a geopolymer matrix material in the form of a macroporous monolith with connected macropores. Illustrative and non-limiting examples of such techniques include additive manufacturing such as extrusion or 3D printing, foaming and the use of sacrificial templates (emulsion, polymer beads, fibers, molds, etc.).

[0052] In a second embodiment, the geopolymer matrix material prepared according to the method of the invention is in the form of objects whose size is between 100 μm and 10 mm. Such objects can be used in packed columns and can be in particular in the form of powders, beads or even extrudates.

[0053] Those skilled in the art know different techniques for obtaining a geopolymer matrix material in the form of objects whose size is between 100 μm and 10 mm. By way of illustrative and non-limiting examples, mention may be made of grinding possibly associated with sieving, extrusion, granulation or even compounding.

[0054] In a particular variant of this second embodiment, the geopolymer matrix material in the form of a micron powder, ideal in a column treatment process. In other words, the material obtained following this embodiment is in the form of grains whose size is typically between 100 μm and 700 μm and, in particular, 200 μm and 500 μm. In this variant, the geopolymer matrix material obtained following step b) of the process according to the invention is subjected to grinding followed by sieving. Similarly, the washing step c) carried out on the geopolymer matrix material in the form of a micron powder allows, in addition to the elimination of at least a portion of the compensation cations, the elimination of the particles resulting from the grinding and adhering to the grains of geopolymer matrix material.

[0055] As previously mentioned, the material capable of extracting lithium prepared according to the method of the invention can be used pure or can incorporate, within it, a selective lithium adsorbent. Indeed, the material capable of extracting lithium can be the geopolymer itself, the formulation of which intrinsically gives it a property of selective extraction of lithium. This geopolymer can also be used as a mesoporous and possibly macroporous binder capable of incorporating one or more selective lithium adsorbents within it, the material capable of extracting lithium then being in the form of a composite comprising a geopolymer matrix in which the selective lithium adsorbent(s) are dispersed, coated and / or incorporated. Typically, in this composite material, the selective lithium adsorbents are present at the surface and in particular at the surface of the pores and voids of the mesopore and possibly macropore type of the mesoporous geopolymer matrix.The integration of selective adsorbents thus makes it possible to significantly increase the selectivity of the entire composite. Indeed, the latter then has several selective sorption sites: one on the geopolymer matrix (or phase) and another, very selective, at the level of the lithium selective adsorbents.

[0056] To prepare such a composite material capable of extracting lithium, the geopolymeric mixture prepared in step a) further comprises at least one lithium-selective extractant. This or these lithium-selective extractants may be added to the activation solution comprising at least lithium hydroxide, mixed with the aluminosilicate source and / or added to the fresh geopolymeric mixture.

[0057] In the context of the present invention, the expressions “selective lithium extractant” and “selective lithium ion exchanger” are equivalent and can be used interchangeably. The selective lithium extractant(s) used in the context of the present invention must be compatible with the composition of a geopolymer. In other words, they must be stable in a strongly basic environment.

[0058] Advantageously, the selective lithium extractant(s) used in the context of the invention may be chosen from the group consisting of a double lamellar lithium-aluminium hydroxide (LiX-2Al(OH)3) with X representing a hydroxide or a chloride, manganese oxide, titanium oxide, tin oxide, tin antimonate, antimony oxide, tantalum oxide, niobium oxide, iron phosphate and zirconium phosphate.

[0059] Furthermore, the size and shape of this or these selective lithium extractants must be chosen such that its / their incorporation within the geopolymer matrix does not impact the kinetic properties of extraction of the latter, i.e. does not influence the formation of mesopores in the matrix, does not block access to the center of the matrix and in particular when the latter is in the form of grains and is easily dispersible. To satisfy these different conditions, the at least one selective lithium extractant is typically in the form of a powder with an advantageously spherical and submicronic morphology. In particular, the grain size of the selective lithium extractant used in the invention is between 2 nm and 50 pm, in particular between 10 nm and 10 pm and, in particular, between 20 nm and 1 pm.

[0060] The present invention also relates to a material capable of extracting lithium prepared by a process as previously defined.

[0061] In a first embodiment, the material capable of extracting lithium prepared by a method as previously defined is a geopolymer in which the lithium content is at least 2% by mass relative to the total mass of said geopolymer. This embodiment corresponds to the case where no additional lithium selective extractant is used.

[0062] In a second embodiment, the material capable of extracting lithium prepared by a method as previously defined is a composite material comprising at least one selective lithium extractant in a geopolymer matrix in which the lithium content is at least 2% by mass relative to the total mass of said geopolymer matrix.

[0063] As previously explained, the material capable of extracting lithium according to the invention is synthesized in the presence of lithium provided essentially in the form of lithium hydroxide (LiOH) in the activation solution. Lithium in the form of cation Li + plays the role of compensation cation possibly with one or more other types of compensation cations and in particular with Na cations + and K + in the material during its synthesis. Even if the material is subjected to washing in order to eliminate at least part of the compensation cations and in particular the Li cations + , there remains, in its structure, lithium, signature of this synthesis in the presence of lithium. For this reason, the geopolymer and the geopolymer matrix according to the invention can be defined respectively as “lithium geopolymer” and “lithium geopolymer matrix”.

[0064] The lithium content in the material capable of extracting lithium according to the invention is in particular between 2% and 6% by mass, in particular between 2.5% and 5.5% by mass, more particularly between 3% and 5% by mass and, most particularly, of the order of 4% by mass (4% ± 0.5% by mass) relative to the total mass of said geopolymer matrix. The lithium content of the material according to the invention is understood to be at the end of the washing step, i.e. step c) as previously defined and before any contact with a liquid likely to contain lithium. This lithium content can be obtained after analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) of the material according to the invention dissolved in an acid such as hydrofluoric acid.

[0065] In the context of the material according to the invention, the size of the mesopores of the geopolymer or the geopolymeric matrix is ​​between 2 nm and 50 nm and in particular centered around 5 nm. The porosity of the material according to the invention can be measured by nitrogen adsorption-desorption or by mercury intrusion.

[0066] As previously mentioned, the material can be easily shaped in different ways as described above to be suitable for a column process. Thus, the material according to the invention can be in the form of a powder and in particular a powder whose particle size is between 100 pm and 700 pm and, in particular, 200 pm and 500 pm, an extrudate, a geopolymer foam or even a macroporous monolith.

[0067] It is evident that the powder, beads, extrudates, geopolymer foam and macroporous monolith according to the present invention may or may not comprise at least one selective lithium extractant as previously defined.

[0068] In the experimental part below, the material according to the invention not comprising a lithium-selective extractant is capable of adsorbing at least 4 mg of lithium per g of dry material and in particular between 4 mg and 8.4 mg of lithium per g of dry material. Also, the present invention finally relates to the use of a material as previously defined for extracting lithium from a solution containing it.

[0069] In other words, the present invention relates to a method for extracting lithium from a solution containing it, consisting of bringing a material as previously described or a material prepared by a preparation method as previously defined into contact with a solution containing lithium. At the end of this contacting step, a material loaded with lithium is obtained.

[0070] The solution containing lithium, typically in the form of a lithium salt from which lithium is to be extracted, is a natural saline solution, concentrated or resulting from a lithium extraction or transformation process. More particularly, said solution is advantageously a saline solution chosen from the group consisting of brines from salt lakes or geothermal sources, brines from salt lakes or geothermal sources, concentrated in lithium following evaporation, seawater, effluents from cathode production plants, effluents from lithium chloride or hydroxide production plants, effluents from processes for extracting lithium from minerals or a mixture thereof.Depending on its nature, the solution used in the invention may, in addition, contain one or more species chosen from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), sulfates (SO4), carbonates (CO3), nitrates (NO3) and bicarbonates (HCO3). Typically, the quantity of lithium in the solution used in the extraction method according to the invention is between 0.005 M and 0.5 M and in particular between 0.05 M and 0.3 M.

[0071] In the extraction method according to the invention, the material as previously defined is placed in a column and the contact between the lithium-containing solution and the material is achieved by passing the solution over the material in the column. In this case, the extraction method according to the invention is a column method.

[0072] Alternatively, the extraction process according to the invention may be a batch process, i.e. a process involving contact between the material as previously defined and the solution containing lithium and stirring of the whole.

[0073] The extraction method according to the invention may, in addition, comprise a prior step of preparing the material according to the preparation method as previously defined and / or a subsequent step of recovering lithium from the lithium-laden material obtained.

[0074] This last recovery step corresponds to a lithium desorption step carried out by bringing the lithium-loaded material into contact with an aqueous solution to obtain an eluate comprising at least lithium, the latter being subsequently able to be concentrated by evaporation. The contacting, possibly carried out with stirring, lasts between 30 seconds and 15 minutes, in particular between 1 minute and 10 minutes and, for example, 2 minutes. Furthermore, this recovery step can be repeated at least once, at least twice, at least three times, at least five times, at least ten times, at least fifteen times or even at least twenty times. Typically, the aqueous solution used for the lithium desorption can be a neutral or acidic aqueous solution, possibly concentrated in alkali ions and in particular in Na ions. +. Everything previously described for the washing solution used in step c) applies mutatis mutandis to the aqueous solution useful for the desorption of lithium. By "concentrated in alkali ions" is meant a solution in which the concentration of alkali ions is greater than or equal to 0.01 M. In a particular embodiment, the aqueous solution used for the desorption of lithium is ultrapure water. Other characteristics and advantages of the present invention will become apparent to those skilled in the art upon reading the examples below given for illustrative and non-limiting purposes, with reference to the appended figures.

[0075] BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 is a photograph of the monolith formed after setting of the geopolymer (part (a)) as well as the grains obtained at the end of synthesis and which can be used in fixed-bed lithium extraction processes (part (b)).

[0077] Figure 2 shows the diffractogram of the lithium geopolymer synthesized in Example 1.

[0078] Figure 3 shows the nitrogen adsorption / desorption isotherm carried out on the lithium geopolymer synthesized in Example 1.

[0079] Figure 4 shows the mesopore size distribution of the lithium geopolymer synthesized in Example 1.

[0080] Figure 5 shows the lithium concentration in successive contact batches as a function of the total volume of water used.

[0081] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0082] Example 1: Synthesis of lithium geopolymer grains

[0083] 7.536 g of a commercial Betolin Li24 solution (Wöllner, composed of 23% by mass SiOz, 3% by mass NazO, 5% by mass LizO and 69.2% by mass HzO) are mixed with 2.0 g of ultrapure water and 0.46 g of LiOH. The solution is then homogenized manually.

[0084] In a second step, 5.332 g of clay powder (metakaolin Metamax from BASF) are finally added and the whole thing is once again homogenized manually.

[0085] After 3 months of rest at room temperature, a monolithic material is obtained (part (a) of Figure 1). This material is then ground and the grains obtained are sieved to obtain grains with a size distribution between 300 and 500 pm (part (b) of Figure 1), which is the most suitable particle size for use in column treatment processes.

[0086] Finally, a washing step is carried out (see example 4).

[0087] This step is necessary to eliminate the presence of fine particles adhered to the grains following grinding (likely to clog the column) and to eliminate part of the cations (Na + and especially Li + ) present in the material. To do this, 3 g of material are stirred manually for 30 seconds in the presence of 100 mL of demineralized water. This step is repeated 15 times, changing the water between each test.

[0088] The materials are finally dried at 80°C overnight.

[0089] Example 2: Characterization of lithium geopolymer

[0090] The chemical composition of the lithium geopolymer of Example 1 was analyzed after dissolving it in hydrofluoric acid. This composition is as follows: 3.3 SiOz : 1 AI2O3 : 1 U2O : 17.5 H2O.

[0091] The lithium content of this material is around 4% by mass.

[0092] The material synthesized in Example 1 was characterized by X-ray diffraction. The diffractogram is shown in Figure 2.

[0093] The diffractogram is characteristic of an amorphous geopolymer with a large hump between 20 and 30°. The observed peaks correspond to the presence of residual TiO2 initially present in trace amounts in the metakaolin used as a precursor of the material.

[0094] The material synthesized in Example 1 was characterized by nitrogen adsorption / desorption to evaluate its porous structure. The resulting isotherm is shown in Figure 3.

[0095] This material exhibits an isotherm characteristic of a mesoporous material. It has a total pore volume of approximately 0.1 cm 3 .g 1 and a specific surface area of ​​81 rr^.g 1. As observed in Figure 4, it exhibits a pore size distribution between 2 and 10 nm, centered around 5 nm. This pore size distribution and specific surface area are sufficient to improve the accessibility of lithium adsorption sites, particularly those located inside the grain, and allow rapid sorption kinetics.

[0096] Example 3: Extraction of Lithium from an aqueous solution by lithium geopolymer

[0097] The material from Example 1 was brought into contact with a solution containing lithium to evaluate its lithium extraction capacity. To do this, between 20 and 50 mg of the material from Example 1 were brought into contact with 10 mL of a solution containing 200 mg / L of Li (in chloride form), 11 g / L of Na (in chloride form) and 1.3 g / L of magnesium (in chloride form). Under these very saline conditions, the material from Example 1 captured between 0.58 and 1.22 mmol (i.e. between 4 and 8.4 mg) of lithium per g of material.

[0098] Example 4: Extraction of Lithium present in lithium geopolymer

[0099] This example shows the feasibility of extracting the lithium present in the material of example 1 using a step of contacting it with an aqueous solution.

[0100] For this example, 3 g of the material from example 1 in the form of grains ground to 300-500 pm are brought into contact with 30 mL of an ultrapure water solution for 2 min with stirring, then the solid is left to settle.

[0101] After recovery of the solution, the lithium concentration in the latter is analyzed. This step is carried out 20 times. Figure 5 shows the evolution of the Li concentration measured in each of the successive batches as a function of the cumulative volume of water used for contact (30 mL multiplied by the number of batches).

[0102] Thus, it is observed that lithium can be extracted from the geopolymer by contacting it with an aqueous solution. After a first contact step, approximately 20% of the mass of Li present in the material is recovered. This percentage rises to 40% after 20 successive contact steps. In this way, the lithium captured during the extraction step (described in Example 3) by a geopolymer material as described in Example 1 can be re-extracted by contact steps with an aqueous solution. References

[0103] [1] Patent application FR3087356 Al

[0104] [2] Patent application FR3051787 Al

[0105] [3] Patent application FR3015458 Al

[0106] [4] International application WO 2016 / 173950 Al [5] International application WO 2021 / 152248 Al

Claims

CLAIMS 1. A method of preparing a material capable of extracting lithium, comprising the steps of: a) preparing a geopolymeric mixture by mixing together (i) an activation solution comprising at least lithium hydroxide and (ii) an aluminosilicate source; b) allowing said geopolymeric mixture prepared in step a) to harden, whereby a geopolymeric matrix material is obtained; c) washing the geopolymeric matrix material obtained in step b) whereby at least a portion of the lithium cations (Li + ) that comprise the geopolymer matrix material are eliminated and a material capable of extracting lithium is obtained.

2. Preparation process according to claim 1, characterized in that the quantity of LiOH in said activation solution is between 3% and 6% by mass, in particular between 4% and 5% by mass and, in particular, of the order of 4.6% (i.e. 4.6% ± 0.1%) by mass relative to the total mass of said activation solution.

3. Preparation process according to claim 1 or 2, characterized in that the SiOz / AhOa molar ratio in the geopolymer matrix of the material obtained in said step b) is between 2.3 and 4.3, in particular between 3.0 and 3.6 and, in particular, of the order of 3.3 (i.e. 3.3 ± 0.1).

4. Preparation process according to any one of claims 1 to 3, characterized in that the quantity of water in said activation solution is between 65% and 80% by mass, in particular between 70% and 75% by mass and, in particular, of the order of 72% (i.e. 72% ± 1%) by mass relative to the total mass of the activation solution.

5. Preparation process according to any one of claims 1 to 4, characterized in that the geopolymeric mixture prepared in said step a) further comprises at least one selective lithium extractant.

6. Preparation process according to claim 5, characterized in that said at least one selective lithium extractant is chosen from the group consisting of a lamellar double hydroxide of lithium-aluminium (LiX-2AI(OH)3) with X representing a hydroxide or a chloride, manganese oxide, titanium oxide, tin oxide, tin antimonate, antimony oxide, tantalum oxide, niobium oxide, iron phosphate and zirconium phosphate.

7. Material capable of extracting lithium prepared by a process as defined in any one of claims 1 to 4, said material being a geopolymer in which the lithium content is at least 2% by mass relative to the total mass of said geopolymer.

8. Material capable of extracting lithium prepared by a process as defined in claim 5 or 6, said material being a composite material comprising at least one selective lithium extractant in a geopolymer matrix in which the lithium content is at least 2% by mass relative to the total mass of said geopolymer matrix.

9. Material according to claim 7 or 8, characterized in that the size of the mesopores of said geopolymer or of said geopolymeric matrix is ​​between 2 nm and 50 nm.

10. Material according to any one of claims 7 to 9, characterized in that said material is in the form of a macroporous monolith with connected macropores.

11. Material according to any one of claims 7 to 9, characterized in that said material is in the form of objects whose size is between 100 im and 10 mm.

12. Use of a material according to any one of claims 7 to 11 for extracting lithium from a solution containing it.

13. A method of extracting lithium from a solution containing it, comprising bringing a material according to any one of claims 7 to 11 into contact with a solution containing lithium.

14. Extraction method according to claim 13, characterized in that said method is a column method or a batch method.

15. Method according to claim 13 or 14, characterized in that the solution is a saline solution chosen from the group consisting of brines from salt lakes or geothermal sources, brines from salt lakes or geothermal sources, concentrated in lithium following evaporation, sea water, effluents from cathode production plants, effluents from lithium chloride or hydroxide production plants, effluents from processes for extracting lithium from minerals or a mixture thereof.

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