Method for preparing material for lithium extraction, material and use thereof

Abstract

The invention relates to a method for preparing a material capable of extracting lithium, comprising the following steps: (a) preparing a geopolymer mixture by mixing (i) an activating solution comprising at least lithium hydroxide and (ii) an aluminosilicate source; (b) curing the geopolymer mixture prepared in step a), thereby obtaining a geopolymer matrix material; and (c) washing the geopolymeric matrix material obtained in step b) so as to remove at least a portion of the lithium cations (Li +) contained in the geopolymeric matrix material and obtain a material capable of extracting lithium The invention also relates to the material thus obtained and to the use thereof.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of lithium extraction, in particular to the field of lithium extraction from solid materials.

[0002] The present invention thus proposes a method for the preparation of a solid geopolymer matrix material, optionally comprising a lithium selective adsorbent, as well as the material thus prepared and its use, in particular for the extraction of lithium. BACKGROUND

[0003] Over the last decade, the demand for lithium has dramatically increased due to the growing use of lithium-ion batteries. This growth is driven by the electrification of transportation and environmental regulations aiming at reducing the use of fossil fuels.

[0004] Currently, lithium resources are mainly divided into two categories: one is rock such as spodumene, lepidolite and petalite; the other is brine distributed in salt flats in Argentina, Bolivia, Chile, etc. Geothermal water also contains a large amount of lithium, and pilot-scale lithium resource research is currently underway. Lithium-ion battery recycling processes or production waste are also secondary resources of lithium.

[0005] For "liquid" ores represented by water in salt flats or geothermal sources, the salinity of these media is very high, up to one hundred grams per liter.

[0006] One of the challenges currently faced is therefore to develop a robust and efficient technology for the extraction of lithium from these aqueous media. Solid-phase extraction techniques are well suited for the extraction of low concentration elements from high salinity media. To this end, a lithium selective material or adsorbent needs to be chosen and shaped so as to be suitable for a fixed bed process that can handle high flow rates (up to several cubic meters per hour).

[0007] To extract lithium from geothermal brines, it has been envisaged to integrate a lithium extraction circuit in the geothermal cycle. This process must avoid any change in the physicochemical properties of the brine (i.e. limit inputs and outputs) so as not to significantly modify the composition of the brine before reinjection. Currently, several projects exist for the recovery of lithium from geothermal brines, but none of them is at industrial scale so far (project of Eramet is pre-industrial). Regarding a suitable solid-phase extraction method, a column filled with cation exchange microfibers can be used to extract lithium from brine and has been tested at pilot scale. In patent application FR3087356 Al [1], Geolith uses fibers from the company Ajelis (MECALICAPT ® ) which are organic materials functionalized with cation exchange organic groups. The use of organic fibers presents some drawbacks at high temperature, in particular the risk of degradation of the organic part.

[0008] Eramet uses lithium-loaded alumina trihydrate-based solid mineral materials as precursors of selective lithium extraction materials, after a proton exchange step before use, mainly for exploitation of salars (Argentina) and plans to use these materials for geothermal resources and even for battery recycling fluids. Although these materials have good adsorption properties in powder form, one of the difficulties is how to shape them to be suitable for a continuous fixed bed process.

[0009] Patent application FR3051787 A1 [2] proposes a method for preparing a crystalline solid mineral material that selectively extracts lithium in the form of extrudates, with good mechanical strength and cohesion, suitable for columns and free of fine particles. The preparation method uses a suspension, which is heat treated, extruded and dried to obtain a material of formula (LiCl)x x .Al(OH)3, nH2O, with n ranging from 0.01 to 10 and x ranging from 0.4 to 1. However, this method does not make it possible to prepare a porous material, which makes it difficult to optimize the accessibility of the adsorption sites to the fluid that flows through the fixed bed; thus, it is difficult to access the interior of the particles, which leads to a decrease in the extraction capacity and kinetics, which in turn affects the performance of the fixed bed process.

[0010] Patent application FR3015458 A1 [3] has the same objective as patent application FR3051787 A1 [2], which aims to prepare a material suitable for column processes, and uses an alumina-type binder, followed by extrusion and drying, with a synthesis method similar to that described in patent application FR3051787 A1 [2]. Again, the porosity of the material is limited, which means that only the outer part of the extrudate is in contact with the fluid in the column, which can reduce the performance of the material. Finally, in both patent applications, it is difficult to control the shape obtained during the drying step, and the shaping is limited to the formation of extrudates.

[0011] Geopolymers-based materials have also been proposed for the separation of metal or metalloid ions (such as metal or metalloid cations) from liquid media containing them.

[0012] Thus, international patent application WO 2016 / 173950 A1 describes a functionalization method of geopolymer monolith foams for the catalytic or purification of effluents in fixed bed treatment processes [4]. This synthesis method is performed in two steps: first, a foam is prepared, then a functionalization is performed in a second step. The global synthesis of this material is complex, which can make it difficult to apply on an industrial scale. Moreover, with this synthesis method, the number of adsorbing agents that can be introduced in the material is limited. Indeed, the selective adsorbent is only coated on the surface of the macropores of the foam, and is not present in the mesoporous walls, which limits its contact area with the effluent and thus the total adsorption capacity of the material. Furthermore, the functionalization method described in this application [4] is only suitable for metal coordination polymer nanoparticles with CN bonds, which are not suitable for the extraction of lithium. Moreover, this synthesis route aims to use the foam in monolith form, in particular directly as a "straight-through" purification column.

[0013] International patent application WO 2021 / 152248 A1 finally describes a synthesis method of a selective adsorbent-geopolymer composite material comprising an interconnected macroporous network [5]. To build this macroporous network, the synthesis process comprises the formulation of an emulsion comprising the precursors of the material, and the removal of the oil phase after the material has hardened. This synthesis method is still complex and difficult to industrialize. Moreover, this synthesis route leads to the formation of macropores with sometimes thin walls and sharp connections. Thus, the mechanical strength of these walls is weak, especially when the effluent flows through, which can lead to the degradation of the walls and the formation of fine particles that clog the adsorption column easily.

[0014] In view of the growing demand for lithium, the inventors have worked on the development of a lithium selective mineral adsorbent that can be used in fixed bed, which has a good adsorption capacity, flow rate (kinetics) and accessibility of the adsorption sites. Moreover, the preparation process of this material must be efficient, simple and easy to industrialize. SUMMARY

[0015] The present invention achieves the goal set by the inventors, namely to prepare a geopolymer matrix material that can act as a lithium extractant to provide a high capacity, while also acting as a mesoporous binder to introduce a more lithium selective adsorbent.

[0016] In fact, the structure of the geopolymer matrix material synthesized in the presence of lithium is suitable for the partial selective adsorption of lithium, thus achieving a high lithium extraction capacity. Moreover, the addition of ion exchangers (i.e. lithium selective adsorbents) in the geopolymer matrix material can increase its selectivity for lithium under the conditions of the specific effluent to be treated, especially in the case of high-salinity effluents. The mesoporous structure of the geopolymer matrix makes the adsorbent particles dispersed therein easily accessible, thus achieving extremely fast adsorption kinetics and optimized performance. Moreover, the mechanical strength of the geopolymer matrix is suitable for fixed beds. Therefore, the size of the ion exchangers, their dispersibility in the geopolymer matrix and the mesoporous structure of the latter make it possible to significantly improve the ion exchange kinetic performance and the shape of the breakthrough curve.

[0017] Finally, it should be noted that the method for preparing the geopolymer matrix material according to the present application is a traditional sol-gel method, which is easy to implement and industrialize. Moreover, the geopolymer matrix material according to the present application can be easily shaped in various ways, such as 3D printing, foaming, extrusion, grinding and sieving, etc., making it suitable for column processes.

[0018] Therefore, the present application relates to a method for preparing a material capable of extracting lithium, the method comprising the following steps:

[0019] a) preparing a geopolymer mixture by mixing together (i) an activation solution containing at least lithium hydroxide and (ii) an aluminosilicate source;

[0020] b) hardening the geopolymer mixture prepared in step a), thus obtaining a geopolymer matrix material;

[0021] c) washing the geopolymer matrix material obtained in step b), thus removing at least a portion of the lithium cations (Li + ) contained in the geopolymer matrix material and obtaining a material capable of extracting lithium.

[0022] The "geopolymer matrix" or "geopolymer" used in the present application refers to a solid, inorganic, porous material in the dry state, which is obtained by hardening a mixture containing a finely ground material (i.e. an aluminosilicate source) and a salt solution (i.e. an activation solution), which is capable of solidifying and hardening over time. The mixture can be referred to as "geopolymer mixture", "geopolymer mixture", "geopolymer composition" or "geopolymer composition". The hardening of the geopolymer is due to the dissolution / condensation reaction of the finely ground material in the salt solution (e.g. a high-pH salt solution, i.e. an activation solution) in the geopolymer mixture.

[0023] More specifically, a geopolymer or geopolymer matrix is an amorphous aluminosilicate inorganic polymer. This polymer is made from reactive materials (i.e. aluminosilicate sources) containing mainly silica and alumina, activated by a highly alkaline solution, with a very low solid / solution weight ratio in the formulation. The structure of a geopolymer is made of a Si-O-Al network, which is made of silica (SiO4) and alumina (AIO4) tetrahedra connected at their apices by shared oxygen atoms. The substitution of a silicon atom (+IV valence) by an aluminum atom (+III valence) leads to a charge deficit, which is compensated by one or more charge-compensating cations (also called compensating cations), which can compensate the negative charge of the AIO4 ⁻ tetrahedra. The compensating cations are usually alkali cations, typically Na + and K + cations.

[0024] A high-pH salt solution, also called "activating solution" in the field of geopolymerization, is a highly alkaline aqueous solution, which can contain silicate components, in particular silicate components selected from the group consisting of silica, colloidal silica and vitreous silica.

[0025] In the present invention, the terms "activating solution", "high-pH salt solution" and "highly alkaline solution" have similar meanings and can be used interchangeably.

[0026] The activating solution used in the scope of the present invention is an aqueous solution, which means that the solvent it contains is water. In the present invention, "water" means tap water, deionized water (or demineralized water), distilled water, ultrapure water (18.2 MΩ) or mixtures thereof.

[0027] "Highly alkaline" or "high-pH" means a solution with a pH greater than 9, in particular greater than 10, in particular greater than 11, more particularly greater than 12. In other words, the concentration of OH - in the activating solution is greater than 0.01 M, in particular greater than 0.1 M, in particular greater than 1 M, more particularly between 5 M and 20 M.

[0028] In addition, the activating solution comprises a compensating cation or a mixture of compensating cations, which can be in the form of an ionic solution or a salt.

[0029] In the scope of the present invention, since the activating solution used contains lithium hydroxide (LiOH), all or part of the compensating cation is lithium ion (Li + ). Typically, the content of LiOH in the activating solution is between 3% and 6% by mass, in particular between 4% and 5% by mass, in particular approximately 4.6% by mass (i.e. 4.6% ± 0.1%) relative to the total mass of the activating solution.

[0030] Furthermore, the activation solution used in the context of the present application can also contain one or more elements selected from the group consisting of sodium silicate (Na2SiO3), potassium silicate (K2SiO2), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), cesium hydroxide (CsOH), sodium oxide (Na2O), lithium oxide (Li2O), and mixtures thereof. In a particular embodiment, the activation solution used in the context of the present application comprises sodium oxide (Na2O) and lithium oxide (Li2O). In a more particular embodiment, the activation solution is an aqueous solution containing silicon dioxide (SiO2), sodium oxide (Na2O), lithium oxide (Li2O), and lithium hydroxide (LiOH). Exemplary activation solutions belonging to this embodiment are provided in the experimental section below.

[0031] In the context of the present application, the terms "aluminosilicate source" and "active material containing predominantly silicon dioxide and aluminum" are similar and can be used interchangeably.

[0032] The active material containing predominantly silicon dioxide and aluminum used for preparing the geopolymer matrix used in the context of the present application is preferably a solid source containing amorphous aluminosilicates. These amorphous aluminosilicates are in particular selected from the group consisting of natural aluminosilicate minerals such as illite, analcite, kaolinite, pyrophyllite, andalusite, bentonite, cyanite, eucolite, grovénite, antigorite, cordierite, feldspar, diaspore, and mixtures thereof; calcined natural aluminosilicate minerals such as metakaolin; synthetic glasses based on pure aluminosilicates; high-alumina cement; pumice; calcined by-products or residues generated in industrial processes such as fly ash generated by coal combustion and blast furnace slag generated during the conversion of iron ore into cast iron in a blast furnace. In a particular embodiment, the aluminosilicate source used is metakaolin.

[0033] In view of the silicate components that can be contained in the activation solution, the amount of aluminosilicate source should be such that the molar ratio SiO2 / Al2O3 in the geopolymer matrix of the material obtained in step b) (i.e. the material capable of capturing lithium prepared according to the method of the present application) is between 2.3 and 4.3, in particular between 3.0 and 3.6, and in particular, about 3.3 (i.e. 3.3 ± 0.1). This molar ratio can be obtained by dissolving the geopolymer matrix material in hydrofluoric acid.

[0034] With such a SiO2 / Al2O3 molar ratio, a sufficient amount of charge-compensating cations (Li + ) is obtained, so that the material prepared according to the method of the present application has an optimal intrinsic lithium capture capacity.

[0035] Furthermore, the amount of water in the activation solution is comprised between 65% and 80% by mass, in particular between 70% and 75% by mass, and in particular is about 72% by mass (i.e. 72% ± 1%) relative to the total mass of the activation solution.

[0036] It should be noted that the combination of the amount of water defined above and the SiO2 / Al2O3 molar ratio makes it possible to produce a geopolymer matrix material having mesopores the size of which is optimal for capturing lithium.

[0037] It should be noted that the geopolymer or geopolymer matrix has an intrinsic mesoporous porosity of about 5% to 30% of the total volume of the geopolymer, the latter possibly also having non- interconnected macropores, this porosity resulting mainly from the geopolymerization process. In other words, the geopolymer, due to its method of preparation, has both interconnected mesopores and possibly non-interconnected macropores.

[0038] By "mesopores" is meant pores or voids having an average diameter of between 2 and 50 nm, in particular between 2 and 20 nm. Within the scope of the application, the optimal mesopore size for capturing lithium is generally between 2 and 10 nm, in particular centered on about 5 nm.

[0039] Step a) of the method according to the application is a conventional step for preparing a geopolymer. Generally, it comprises the following sub-steps:

[0040] i) preparation of an activation solution comprising at least lithium hydroxide as described above,

[0041] ii) addition of at least one aluminosilicate source to the solution obtained in sub-step i) and mixing as a whole, thereby obtaining a geopolymer mixture comprising at least lithium hydroxide.

[0042] In sub-step ii), the aluminosilicate source is added to the activation solution comprising at least lithium hydroxide in one or more steps. After addition of the aluminosilicate source to the activation solution, the resulting solution or dispersion is mixed using a mixer, a magnetic stirrer, a magnetic bar, an ultrasonic bath or a homogenizer. The mixing in step ii) of the method according to the application is carried out manually or mechanically at a constant speed. By "constant speed" is meant within the scope of the application 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 stirring is carried out using a magnetic stirrer or a mixer. Any mixer known to the person skilled in the art can be used within the scope of the application. By way of example but not limitation, the following mixers can be used: ® stirrers, HOBART ® stirrers, HENSCHEL ® stirrers and HEIDOLPH ® stirrers.

[0043] For the sake of illustration, the following experimental section provides an example of the preparation of such geopolymer mixture.

[0044] Generally, step a) of the process, and in particular the sub-steps i) and ii) comprised therein, are carried out at a temperature ranging from 10°C to 40°C, advantageously from 15°C to 30°C, more particularly at ambient temperature (i.e. 23°C ± 5°C), for a duration of more than 1 minute, in particular from 2 minutes to 15 minutes, and especially from 3 minutes to 5 minutes.

[0045] Step b) of the process according to the application consists in placing the geopolymer mixture obtained in step a) in conditions allowing it to harden.

[0046] Any technique known to the person skilled in the art for hardening a geopolymer mixture can be used in the hardening step of the process.

[0047] The conditions allowing hardening in step b) of the process according to the application advantageously comprise a curing step, optionally followed by a drying step. The curing step can be carried out at a temperature ranging from 10°C to 80°C, in particular from 20°C to 60°C, especially from 30°C to 40°C, and for a duration ranging from 1 to 40 days, or even more. Alternatively, the conditions allowing hardening in step b) can comprise a curing step carried out at a temperature lower than 30°C, in particular at ambient temperature, and for a duration ranging from 18 hours to 150 days, in particular from 24 hours to 120 days, especially about 3 months (i.e. 3 months ± 5 days). Regardless of the temperature at which the curing step is carried out, this step can be carried out outdoors, underwater, in various sealed moulds, possibly by humidifying the air surrounding the geopolymer mixture, or by applying a water-impermeable coating on said geopolymer mixture.

[0048] Step c) of the process according to the application is carried out to remove at least some of the compensating cations, in particular at least some of the lithium cations (Li + ).

[0049] In a first embodiment, step c) can consist in contacting the geopolymer matrix material with a washing liquid and in carrying out a global stirring for a duration ranging from 10 seconds to 5 minutes, in particular from 20 seconds to 3 minutes, especially about 30 seconds (i.e. 30 seconds ± 5 seconds). After removal of the washing liquid containing the compensating cations, the steps of contacting and stirring with a new washing liquid can be repeated at least once, at least twice, at least five times, at least ten times or even at least fifteen times. The composition of the washing liquids for the two successive washings can be identical or different. In this first embodiment, the washing liquid recovered after contacting and stirring with the geopolymer matrix material contains less than 0.1 g / l of Li +The concentration of Li can be used to assess the progress of the washing and whether a repetition of the contact with a new washing liquid is necessary. In a second embodiment, step c) can consist of arranging the geopolymer matrix material in a column and circulating a washing liquid through the column. The circulation is usually continuous. By monitoring the Li + concentration at the column outlet, the progress of the washing can be assessed.

[0050] In general, the washing liquid that can be used in the first and second embodiments described above can be a neutral or acidic aqueous solution and optionally contains a higher concentration of sodium. An acidic aqueous solution that can be used within the scope of the present application refers to an aqueous solution having a pH value between 4 and 6. An aqueous solution containing a higher concentration of sodium that can be used within the scope of the present application refers to an aqueous solution in which the [Na + ] concentration is greater than or equal to 0.01 M. In a particular embodiment, the washing liquid is water as described above, in particular deionized water.

[0051] Advantageously, after the washing step and before using the material thus obtained, which is capable of extracting lithium, the material is dried. The drying temperature can be between 40 °C and 90 °C, in particular between 50 °C and 85 °C, in particular between 60 °C and 80 °C, and the drying time can be between 4 hours and 5 days, in particular between 8 hours and 2 days, in particular between 10 hours and 15 hours.

[0052] As described above, the geopolymer matrix material prepared according to the method of the present application is susceptible to shaping. This shaping can be performed before and / or after obtaining the geopolymer matrix material, i.e. before and / or after step b) of the method according to the present application.

[0053] In a first embodiment, the geopolymer matrix material prepared according to the method of the present application is in the form of a macroporous monolith, wherein the macropores are interconnected. In other words, the shaping step in the present first embodiment aims at obtaining a monolithic material having a geopolymer matrix, wherein the geopolymer matrix is of mesoporous and macroporous structure, and the macropores are interconnected. By "macropore" is meant a pore or void having an average diameter greater than 50 nm, in particular greater than 70 nm. The mesopores of the geopolymer matrix in the material obtained according to the present first embodiment are defined as described above.

[0054] Various techniques for preparing a monolithic macroporous polymer matrix material having interconnected macropores are well known to the person skilled in the art. Examples of such techniques include, but are not limited to, additive manufacturing (such as extrusion or 3D printing), foaming and use of sacrificial templates (emulsions, polymer beads, fibers, molds, etc.).

[0055] In a second embodiment, the geopolymer matrix material prepared according to the method of the present application is in the form of an object having a size between 100 pm and 10 mm. Such objects can be used to fill a column, in particular in the form of a powder, beads or an extrudate.

[0056] Various techniques for obtaining a geopolymer matrix material presenting objects having a size comprised between 100 pm and 10 mm are well known by the skilled person. They include, for example, but are not limited to, milling (which can be combined with sieving), extrusion, granulation or kneading.

[0057] In one particular variant of this second embodiment, the geopolymer matrix material is in the form of a micrometric powder, which is well suited to column processing methods. In other words, the material obtained according to this embodiment is particulate, with a particle size generally comprised between 100 pm and 700 pm, in particular between 200 pm and 500 pm.

[0058] In this variant, the geopolymer matrix material obtained after step b) of the method according to the application is milled, then sieved. Similarly, the geopolymer matrix material in the form of a micrometric powder is washed in step c), which makes it possible to remove, in addition to at least part of the compensating cations, fine particles generated during the milling process, which adhere to the particles of geopolymer matrix material.

[0059] As mentioned above, the material capable of extracting lithium prepared according to the method of the application can be pure or can comprise a lithium selective adsorbent therein. In fact, the material capable of extracting lithium can be a geopolymer as such, the formulation of which confers on it lithium selective extraction properties as such. This geopolymer can also be used as a mesoporous (or optionally macroporous) binder, in which one or more lithium selective adsorbents can be introduced. In this case, the material capable of extracting lithium presents a composite material comprising a geopolymer matrix in which lithium selective adsorbents are dispersed, coated and / or embedded. Generally, in this composite material, the lithium selective adsorbents are present at the surface, in particular at the surface of the mesoporous (and possibly macroporous) type pores and voids of the geopolymer matrix. The introduction of the selective adsorbents thus makes it possible to significantly increase the selectivity of the entire composite material. In fact, this composite material has a plurality of selective adsorption sites: one on the geopolymer matrix (or phase) and the other on the lithium selective adsorbents, which are highly selective.

[0060] To prepare this composite material capable of extracting lithium, the geopolymer mixture prepared in step a) also comprises at least one lithium selective extractant. This or these lithium selective extractants can be added to the activation solution containing at least lithium hydroxide, mixed with the aluminosilicate source and / or added to the fresh geopolymer mixture.

[0061] In the context of the present application, the terms "lithium selective extractant" and "lithium selective ion exchanger" are equivalent and can be used interchangeably.

[0062] The lithium selective extractants used in the context of the present invention must be compatible with the composition of the geopolymer. In other words, they must be stable in a strongly basic environment.

[0063] Advantageously, the lithium selective extractants used in the context of the present invention can be selected from the group consisting of lithium aluminum layered double hydroxides (LiX-2Al(OH)3), wherein X represents a hydroxide or a chloride; manganese oxides; titanium oxides; tin oxides; tin antimonates; antimony oxides; tantalum oxides; niobium oxides; iron phosphates; and zirconium phosphates.

[0064] Moreover, the size and shape of the suitable lithium selective extractants must be chosen so that their introduction into the geopolymer matrix does not affect the extraction kinetic properties of the latter, i.e. does not affect the formation of mesopores in the matrix nor does it hinder the access to the channels leading to the center of the matrix, especially when the matrix is in the form of particles and is easily dispersible. In order to meet these different conditions, the at least one lithium selective extractant is generally in the form of a powder and advantageously in the form of spheres and submicron morphology. In particular, the particle size of the lithium selective extractants used in the context of the present invention is between 2 nm and 50 pm, in particular between 10 nm and 10 pm, in particular between 20 nm and 1 pm.

[0065] The present invention also relates to a material capable of extracting lithium, which is prepared by the above-mentioned process.

[0066] In a first embodiment, the material capable of extracting lithium, prepared by the above-mentioned process, is a geopolymer, wherein the lithium content is at least 2% by mass relative to the total mass of the geopolymer. This embodiment corresponds to the case where no additional lithium selective extractant is used.

[0067] In a second embodiment, the material capable of extracting lithium, prepared by the above-mentioned process, is a composite material comprising at least one lithium selective extractant in a geopolymer matrix, the lithium content of which is at least 2% by mass relative to the total mass of the geopolymer matrix.

[0068] As mentioned above, the material capable of extracting lithium according to the present invention is synthesized in the presence of lithium in the form of lithium hydroxide (LiOH) in an activation solution. Lithium is present in the form of Li + cations, which can act together with other compensating cation(s) during the synthesis of the material, in particular Na + and K + cations. Even if the material is washed to remove at least part of the compensating cations, in particular Li + cations, lithium remains in its structure as a characteristic of the synthesis of the material in the presence of lithium. Thus, the geopolymer and the geopolymer matrix according to the present invention can be respectively defined as "lithium geopolymer" and "lithium geopolymer matrix".

[0069] The lithium content in the material according to the application capable of extracting lithium is specifically from 2 to 6% by mass, in particular from 2.5 to 5.5% by mass, more particularly from 3 to 5% by mass, even approximately 4% by mass (4% by mass ± 0.5%) relative to the total mass of the geopolymer matrix. The lithium content of the material according to the application is the content measured at the end of the washing step (i.e. step c defined above) and before contact with a liquid that can contain lithium. This lithium content can be obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) analysis of the material according to the application dissolved in an acid such as hydrofluoric acid.

[0070] Within the scope of the material according to the application, the mesopore size of the geopolymer or geopolymer matrix is from 2 nm to 50 nm, in particular centred around approximately 5 nm. The porosity of the material according to the application can be determined by nitrogen adsorption-desorption or mercury porosimetry.

[0071] As mentioned above, this material can easily be shaped into various shapes to be suitable for a column process. Thus, the material according to the application can be in the form of a powder, in particular a powder having a particle size of from 100 pm to 700 pm, in particular from 200 pm to 500 pm; also in the form of an extrudate, a geopolymer foam or even a macroporous monolith.

[0072] Obviously, the powder, the beads, the extrudate, the geopolymer foam and the macroporous monolith according to the application can or can not comprise at least one lithium selective extractant as described above.

[0073] In the experimental section below, the material according to the application not comprising a lithium selective extractant is capable of adsorbing at least 4 mg of lithium per gram of dry material, in particular from 4 mg to 8.4 mg of lithium per gram of dry material. Thus, the present application finally relates to the use of the above-mentioned material for the extraction of lithium from a lithium-containing solution.

[0074] In other words, the present application relates to a method for the extraction of lithium from a lithium-containing solution, this method consisting of a step of contacting the above-mentioned material or a material prepared according to the above-mentioned preparation method with a lithium-containing solution. After this step of contact, a lithium-loaded material is obtained.

[0075] The lithium-containing solution from which lithium is to be extracted, the lithium generally being present in the form of a lithium salt, is a natural salt solution, which can be a concentrated salt solution, or a salt solution originating from a lithium extraction or conversion process. More particularly, the solution is advantageously a salt solution chosen from the group consisting of a brine from a salt lake or a geothermal source, a brine from a salt lake or a geothermal source concentrated by evaporation, seawater, an effluent from a cathode production plant, an effluent from a lithium chloride or lithium hydroxide production plant, an effluent from a mineral lithium extraction process, or a mixture thereof. Depending on its nature, the solution used in the present application can also comprise 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), sulfate (SO4), carbonate (CO3), nitrate (NO3) and bicarbonate (HCO3). Generally, the amount of lithium in the solution used in the extraction method according to the application is between 0.005 M and 0.5 M, in particular between 0.05 M and 0.3 M.

[0076] In the extraction method of the application, the material described above is placed in a column and the lithium-containing solution is passed through the material in the column so as to come into contact with the material. In this case, the extraction method of the application is a column method.

[0077] Alternatively, the extraction method according to the application can be a batch method, i.e. a method which involves contacting the material described above with the lithium-containing solution and stirring the whole.

[0078] The extraction method of the application can also comprise a preliminary step, i.e. the preparation of the material according to the preparation method described above, and / or a subsequent step, i.e. the recovery of lithium from the lithium-loaded material obtained.

[0079] This last recovery step corresponds to a desorption step of lithium, i.e. the contact of the lithium-loaded material with an aqueous solution so as to obtain at least an eluate containing lithium, which can then be concentrated by evaporation. This contact can be carried out with stirring for a duration of between 30 seconds and 15 minutes, in particular between 1 minute and 10 minutes, 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. Generally, the aqueous solution used for the desorption of lithium can be a neutral or acidic aqueous solution, possibly containing a high concentration of alkali metal ions, in particular sodium ions (Na + ). The above description for the washing solution used in step c) also applies to the aqueous solution which can be used for the desorption of lithium. By "high concentration of alkali metal ions" is meant a solution in which the concentration of alkali metal 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.

[0080] Other features and advantages of the present invention will become apparent to those skilled in the art from a reading of the following non-limiting examples provided by way of illustration and reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0081] Figure 1 is a photograph of the monolithic material formed after setting of the geopolymer of the present invention (part (a)), and a photograph of the granules obtained at the end of the synthesis, which can be used in the fixed bed lithium extraction process (part (b)).

[0082] Figure 2 The diffractogram of the lithium geopolymer synthesized in Example 1 is shown.

[0083] Figure 3 The nitrogen adsorption / desorption isotherm of the lithium geopolymer synthesized in Example 1 is shown.

[0084] Figure 4 The mesopore size distribution of the lithium geopolymer synthesized in Example 1 is shown.

[0085] Figure 5 The variation of lithium concentration in the successive contact batches as a function of the total amount of water used is shown. DETAILED DESCRIPTION

[0086] Example 1 : Synthesis of lithium-based polymer granules

[0087] 7.536 g of a commercial Betolin Li24 solution (Wöllner company, composition Si02 mass fraction 23%, Na20 mass fraction 3%, Li20 mass fraction 5% and H20 mass fraction 69.2%) were mixed with 2.0 g of ultrapure water and 0.46 g of LiOH. The suspension was then homogenized manually.

[0088] In a second step, 5.332 g of clay powder (Metamax Metamax® off-highway kaolin, purchased from BASF) were added and the whole was again homogenized manually.

[0089] After 3 months of rest at ambient temperature, the monolithic material was obtained (part (a) of Figure 1 of the figure). This material was then ground and the obtained granules were sieved to obtain granules with a particle size distribution between 300 and 500 pm (part (b) of Figure 1 of the figure), which is the most suitable particle size for a column treatment process.

[0090] Finally, a washing step was performed (see Example 4).

[0091] This step aims at removing fine particles that stick to the granules after grinding (these particles tend to clog the column) and at removing part of the cations (Na + and especially Li+ To this end, 3 g of material were mixed with 100 mL of demineralized water, manually stirred for 30 seconds. This step was repeated 15 times, changing the water between each test.

[0092] Finally, the material was dried overnight at 80°C.

[0093] Example 2: Characterization of the lithium geopolymer

[0094] The lithium geopolymer of Example 1 was dissolved in hydrofluoric acid and its chemical composition was analyzed. The composition was as follows: 3.3 Si02: 1 Al203: 1 Li20: 17.5 H20.

[0095] The lithium content of this material was about 4% by weight.

[0096] The material synthesized in Example 1 was characterized by X-ray diffraction. The diffractogram is shown in Figure 2 .

[0097] The diffractogram showed the characteristic of an amorphous geopolymer, with a broad peak between 20° and 30°. The observed peaks corresponded to residual Ti02initially present in trace amounts in the metakaolin used as precursor of the material.

[0098] The material synthesized in Example 1 was characterized by nitrogen adsorption / desorption to assess its porous structure. The obtained isotherm is shown in Figure 3 .

[0099] The material presented isotherm characteristics of a mesoporous material. Its total pore volume was about 0.1 cm 3 .g -1 and its specific surface area was 81 m 2 .g -1 . As shown in Figure 4 , its pore size distribution was between 2 nm and 10 nm, centered at about 5 nm.

[0100] This pore size distribution and specific surface area were sufficient to improve the accessibility of lithium adsorption sites, especially those located inside the particles, and to achieve fast adsorption kinetics.

[0101] Example 3: Extraction of lithium from aqueous solutions using the lithium geopolymer

[0102] To evaluate the ability of the material of example 1 to extract lithium, it was contacted with a solution containing lithium. To do this, 20 to 50 mg of the material of example 1 were contacted with 10 mL of a solution containing 200 mg / L of lithium (in the form of a chloride), 11 g / L of sodium (in the form of a chloride) and 1.3 g / L of magnesium (in the form of a chloride). Under such high salinity conditions, 0.58 to 1.22 mmol (i.e. 4 to 8.4 mg) of lithium per gram of material of example 1 can be adsorbed.

[0103] Example 4: Extraction of lithium present in the lithium geopolymer

[0104] This example shows that the lithium present in the material of example 1 can be extracted by this step of contact with an aqueous solution.

[0105] In this example, 3 g of the material of example 1 (ground particles with a particle size of 300-500 pm) were contacted with 30 mL of an ultrapure aqueous solution for 2 minutes, with stirring, then the solids were allowed to settle.

[0106] After recovery of the solution, the lithium concentration in the solution was analysed. This step was repeated 20 times. Figure 5 The lithium concentration measured in each successive batch is shown as a function of the cumulative volume of water contacted (30 mL multiplied by the number of batches).

[0107] Thus, it can be observed that lithium can be extracted from the geopolymer by contact with an aqueous solution. After the first contact, approximately 20% of the lithium mass present in the material can be recovered. After 20 successive contacts, the recovery rate can reach 40%.

[0108] In this way, the lithium captured by the geopolymer material described in example 1 in the extraction step (as described in example 3) can be re-extracted by the step of contact with an aqueous solution.

[0109] References

[0110] [1] Patent application FR3087356 A1

[0111] [2] Patent application FR3051787 A1

[0112] [3] Patent application FR3015458 A1

[0113] [4] International application WO 2016 / 173950 A1

[0114] [5] International application WO 2021 / 152248 A1.

Claims

1. A method for preparing a material capable of extracting lithium, comprising the following steps: a) Prepare a geopolymer mixture by mixing the following substances together: (i) an activated solution containing at least lithium hydroxide and (ii) an aluminosilicate source; b) Harden the geopolymer mixture prepared in step a) to obtain a geopolymer matrix material; c) Cleaning the geopolymer matrix material obtained in step b) to remove at least a portion of the lithium cations (Li) contained in the geopolymer matrix material. + ), and obtain materials from which lithium can be extracted.

2. The preparation method according to claim 1, characterized in that, The amount of LiOH in the activation solution is 3% to 6% by mass relative to the total mass of the activation solution, particularly 4% to 5% by mass, and especially about 4.6% by mass (i.e., 4.6% ± 0.1%).

3. The preparation method according to claim 1 or 2, characterized in that, The SiO2 / Al2O3 molar ratio in the geopolymer matrix of the material obtained in step b) is 2.3 to 4.3, particularly 3.0 to 3.6, especially about 3.3 (i.e. 3.3 ± 0.1).

4. The preparation method according to any one of claims 1 to 3, characterized in that, The amount of water in the activation solution is 65% to 80% by mass, particularly 70% to 75% by mass, and especially about 72% by mass (i.e., 72% ± 1%), relative to the total mass of the activation solution.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The geopolymer mixture prepared in step a) further comprises at least one lithium selective extractant.

6. The preparation method according to claim 5, characterized in that, The at least one lithium selective extractant is selected from the group consisting of: lithium aluminum layered double hydroxide (LiX-2Al(OH)3), where X represents a hydroxide or chloride; manganese oxide; titanium oxide; tin oxide; tin antimonate; antimony oxide; tantalum oxide; niobium oxide; iron phosphate; and zirconium phosphate.

7. A material capable of extracting lithium, prepared by the preparation method according to any one of claims 1 to 4, wherein the material is a geopolymer and the lithium content of the geopolymer is at least 2% by mass relative to the total mass of the geopolymer.

8. A material capable of extracting lithium, prepared by the preparation method according to claim 5 or 6, said material being a composite material comprising at least one lithium selective extractant located in a geopolymer matrix, said lithium selective extractant being at least 2% by mass relative to the total mass of said geopolymer matrix.

9. The material according to claim 7 or 8, characterized in that, The mesopore size of the geopolymer or the geopolymer matrix is ​​from 2 nm to 50 nm.

10. The material according to any one of claims 7 to 9, characterized in that, The material is a monolithic material with interconnected macropores.

11. The material according to any one of claims 7 to 9, characterized in that, The material is presented as objects with dimensions ranging from 100µm to 10 mm.

12. Use of the material according to any one of claims 7 to 11 in the extraction of lithium from a lithium-containing solution.

13. A method for extracting lithium from a lithium-containing solution, comprising the step of contacting the material according to any one of claims 7 to 11 with the lithium-containing solution.

14. The extraction method according to claim 13, characterized in that, The method described is either the column method or the intermittent method.

15. The method according to claim 13 or 14, characterized in that, The solution is a salt solution selected from the group consisting of: brine from a salt lake or geothermal source, brine from a salt lake or geothermal source for lithium concentration by evaporation, seawater, effluent from a cathode production plant, effluent from a lithium chloride or lithium hydroxide production plant, effluent from a mineral lithium extraction process, or mixtures thereof.

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