Methods for preparing functionalized geopolymers involving 3D printing, said geopolymers and their uses

Abstract

The present invention relates to a method for preparing a geopolymer capable of capturing at least one ion, comprising first a geopolymer preparation step comprising at least one step in which 3D printing is used, followed by a functionalization step of the geopolymer thus prepared with at least one extracting group, said extracting group not comprising an -NH2 amino group. The present invention also relates to the functionalized geopolymer thus prepared and its use for separating said at least one ion from a stream containing said at least one ion.

Description

[Technical Field]

[0001] The present invention is in the field of geopolymers, and in particular geopolymers useful for decontamination, purification and / or decontamination and filtration of liquid or gaseous effluents.

[0002] Indeed, the present invention proposes a method that makes it possible to prepare geopolymers capable of capturing at least one target element in ionic form by covalently grafting one or more identical or different extracting groups. Furthermore, this method includes a 3D printing step that optimizes the open porosity to obtain geopolymers with a sufficient specific surface area, allowing for the grafting of more extracting groups.

[0003] The present invention also relates to the geopolymers thus prepared and their various applications in any field requiring selective capture or selective extraction of target elements in ionic form. [Background technology]

[0004] Geopolymers are aluminosilicate materials synthesized by alkaline activation of aluminosilicate sources, such as metakaolin or fly ash. They are primarily amorphous materials with an intrinsic porosity of approximately 40–50%, an average pore size of 4–15 nm, and a pore size of 40–200 m, depending on the alkaline activator used, i.e., sodium or potassium. 2 / g (Non-Patent Document 1).

[0005] Geopolymers are said to have good mechanical strength, fire resistance, and acid resistance, and can be used in various industrial sectors, such as (i) in the construction industry as construction and insulation materials, (ii) in the nuclear industry for waste disposal, or (iii) in the chemical industry as catalyst supports or filtration membranes or for capturing toxic elements or other heavy metals.

[0006] Regarding the geopolymer aspect, geopolymers are particularly used for capturing cesium. Lee et al. (2017) showed that cesium in solution was adsorbed onto mesoporous geopolymers (Non-Patent Document 2). The recovery efficiency was 96%, and the maximum adsorption amount reached 15.24 mg / g of geopolymer, which was less than that of crushed mordenite (zeolite). Only three parameters were studied: the initial cesium concentration, the pH of the cesium solution, and the contact time of the geopolymer with this solution.

[0007] Since 2009, 3D printing has been constantly improved and transformed in many fields. A major advantage of 3D printing is the ability to contract manufacture more or less complex parts to meet the specifications of future applications. 3D printing of geopolymers has been described in the prior art.

[0008] A study carried out by Luukkonen et al. (2020) compared the effectiveness of different filtration membranes made of geopolymers incorporating either silver or copper, i.e. modified geopolymers, in filtering water (Non-Patent Document 3). Various synthesis routes have been investigated: additive manufacturing 3D printing, i.e., producing parts with complex and controlled shapes, direct foaming, and granulation. The geopolymer obtained by 3D printing of a specific composition carried out in [3] had the lowest total porosity (28% in the first layer) and the lowest specific surface area (6 m2) after curing at 60 °C for 4 hours. 2 / g).

[0009] (2020) demonstrated the feasibility of producing 3D-printable geopolymers capable of selectively reducing gaseous nitrogen oxides (NOx), a pollutant emitted by combustion engines (NPL 4). To solve this problem, the geopolymer incorporates zeolite (37 wt% ZSM-5) and is functionalized by ion exchange (copper ions) using a copper acetate solution. Depending on the composition of the geopolymer used, mesopores can be generated after acid treatment. However, these studies show that copper incorporation is suboptimal because copper is found in the form of copper hydroxide, which is not reactive in the selective catalytic reduction of NOx.

[0010] The inventors aimed to propose an easy-to-implement method for preparing geopolymers capable of effectively capturing at least one element of interest in ionic form, in particular with a view to producing filtration membranes or to decontaminating liquid or gaseous emissions of toxic elements or other heavy metals. Summary of the Invention

[0011] The present invention makes it possible to achieve the objectives set out by the inventors by providing a method that makes it possible to prepare, in a simple and easy to implement way, a geopolymer capable of effectively trapping at least one ion, such as a metal or metalloid ion, which material does not have the drawbacks of the materials of the prior art.

[0012] More specifically, the inventors have shown that it is possible to solve the technical problems of the materials of the prior art by combining the preparation of a geopolymer comprising at least one step of 3D printing and the functionalization of the geopolymer thus prepared with at least one abstracting group capable of capturing, chelating and / or complexing at least one ion, such as a metal or metalloid ion.

[0013] Indeed, there are numerous advantages to both direct (or additive manufacturing) 3D printing and inverse 3D printing using a sacrificial support (or scaffold) (also known as a "template"), particularly for fabrication of structures over lengths of tens of meters. 2 It is possible to obtain geopolymers with high specific surface areas, such as 1 / g, which means sufficient surface area and a sufficient number of reactive functional groups for grafting extracting groups. Such specific surface areas can be obtained with much weaker macroporosity (from a few micrometers to a few hundred nanometers) by increasing the printing density through a decrease in printing resolution (from the order of millimeters to micrometers). Furthermore, geopolymers or sacrificial supports prepared by 3D printing can have complex shapes with increased specific surface areas due to the increased tortuosity resulting from the modification of the printing geometry.

[0014] Furthermore, direct 3D printing allows the preparation of geopolymers with connected macropores obtained via 3D printing in addition to the mesopores and any unconnected macropores that primarily result from the geopolymerization method.

[0015] Similarly, in inverse 3D printing using a sacrificial support immersed in a geopolymer mixture or grout, removing the sacrificial support after the geopolymer has hardened opens up the macropores of the geopolymer and therefore allows for a lower resolution in terms of macropore size to be achieved.

[0016] Thus, the geopolymer obtained by the method of the present invention can be in the form of a geopolymer foam without the addition of pore-forming materials to the geopolymer mixture or geopolymer grout. The pore-forming materials may require physical and / or chemical modification to be removed from the geopolymer. However, the present invention allows for the use of pore-forming materials that do not require or require removal by treatments that do not physically or chemically modify the geopolymer.

[0017] Finally, the inventors demonstrated that it is possible to obtain geopolymers without the need to dry the material at high temperatures to open voids. Indeed, the inventors demonstrated that, more specifically, by 3D printing geopolymer grout, the need for heat treatment is eliminated. This advantage, i.e., the absence of a high-temperature step, also exists when geopolymers are obtained by using sacrificial supports created by 3D printing. However, it should be noted that in inverse 3D printing, high temperatures of more than 30 °C may be required if the steps of opening voids by removing the sacrificial support and functionalizing with extracting groups are performed simultaneously.

[0018] The present invention therefore relates to a method for preparing a geopolymer capable of trapping at least one ion, comprising the following steps: - a geopolymer preparation process, including at least one process in which 3D printing is used, and - functionalizing the prepared geopolymer with at least one abstracting group specific for said at least one ion.

[0019] Advantageously, in the method according to the invention, the extraction group does not contain an -NH2 amine group.

[0020] "Geopolymer" in the present invention means a solid, porous material in the dry state, obtained after hardening a mixture containing finely divided materials (i.e., aluminosilicate source) and a salt solution (i.e., activation solution), which can set and harden over time. This mixture is also referred to by the terms "geopolymer mixture," "geopolymeric mixture," "geopolymer composition," or "geopolymeric composition." The geopolymer hardens by dissolution / polycondensation of the finely divided materials of the geopolymer mixture in a salt solution, such as a salt solution with a high pH (i.e., activation solution).

[0021] More specifically, geopolymers are amorphous aluminosilicate inorganic polymers. They are obtained from reactive materials essentially containing silica and aluminum (i.e., aluminosilicate sources) activated by a strong alkaline solution, with a low solid / solution mass ratio in the composition. The structure of geopolymers consists of a Si-O-Al network formed by silicate (SiO4) and aluminate (AlO4) tetrahedra connected by sharing oxygen atoms at their vertices. Within this network, there are one or more charge-compensating cations (also called compensation cations), and these cations are AlO4 - The negative charge of the complex can be compensated by said compensating cation, which is advantageously selected from the group consisting of alkali metals such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs); alkaline earth metals such as magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba); or mixtures thereof.

[0022] The expressions "reactive material substantially comprising silica and aluminum" and "aluminosilicate source" are equivalent and can be used interchangeably in the present invention.

[0023] The reactive material essentially containing silica and aluminum that can be used to prepare the geopolymer matrix embodied in the present invention is advantageously a solid source containing amorphous aluminosilicates, selected in particular from natural aluminosilicate minerals such as illite, stilbite, kaolinite, pyrophyllite, andalusite, bentonite, kyanite, mylanite, globnite, amesite, cordierite, feldspar, allophane, etc.; calcined natural aluminosilicate minerals such as metakaolin; synthetic glasses containing pure aluminosilicates; aluminous cements; pumice; by-products or industrial residues such as fly ash or blast furnace slag obtained from the combustion of coal or the conversion of iron ore to pig iron in a blast furnace; and mixtures thereof.

[0024] The high pH salt solution, also known in the field of geopolymerization as an "activation solution," is a strongly alkaline aqueous solution that may optionally contain a silicate component selected from the group consisting of silica, colloidal silica, and vitreous silica, among others.

[0025] The expressions "activating solution", "high pH salt solution" and "strong alkaline solution" are synonymous and can be used interchangeably in the present invention.

[0026] By "strongly alkaline" or "having a high pH" is meant a solution having a pH greater than 9, particularly greater than 10, particularly greater than 11, more particularly greater than 12. In other words, the activation solution is greater than 0.01M, particularly greater than 0.1M, particularly greater than 1M, more particularly 5-20M OH. - It has a concentration.

[0027] Furthermore, the activation solution comprises a compensation cation or a mixture of compensation cations in the form of an ionic solution or salt, and is therefore selected in particular from aqueous solutions of sodium silicate (Na2SiO3), potassium silicate (K2SiO2), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), cesium hydroxide (CsOH) and derivatives thereof.

[0028] Geopolymers have a mesoporous intrinsic porosity of approximately 10-20% by volume relative to the total volume of the geopolymer, and the geopolymer may also have unconnected macropores. In other words, geopolymers have connected mesopores and possibly unconnected macropores, depending on their preparation method. However, it is possible to prepare mesoporous and macroporous geopolymers with connected macropores through direct 3D printing processes or inverse 3D printing processes using sacrificial supports. In this case, they are called geopolymer foams. "Mesopores" refer to pores or spaces with an average diameter of 2-50 nm, particularly 2-20 nm. "Macropores" refer to pores or spaces with an average diameter greater than 50 nm, particularly greater than 70 nm. In geopolymer foams, the total porosity, corresponding to the macroporosity and mesoporosity, is greater than 70% by volume, particularly greater than 75%, and especially greater than 80% of the total volume of the geopolymer foam.

[0029] In the present invention, the geopolymer can be either a mesoporous geopolymer, optionally with unconnected macropores, or a mesoporous and macroporous geopolymer, i.e., a geopolymer foam, in which the macropores are connected. In these two options, the extracting groups are present on the surface, and in particular on the surface of the mesopores or voids of the mesoporous geopolymer, optionally with unconnected macropores, or the geopolymer foam.

[0030] As mentioned above, the geopolymers prepared by the method according to the present invention are capable of capturing one or more ions via ion-specific extraction groups introduced on their surfaces.

[0031] Extracting groups are also known in the prior art by the expressions "chelating groups" or "complexing groups". These are groups that are capable of capturing, chelating and / or complexing one or more ions, in particular one or more metal or metalloid ions. Any organic extracting group known in the prior art can be used in the present invention.

[0032] Illustrative, non-limiting examples of such abstracting groups include:

[0033] -R1, R2 and R3 are the same or different and represent a hydrogen atom, an alkyl group or an aryl group; -N + an ammonium group of formula (R1)(R2)(R3), -R4 and R5 are the same or different and represent a hydrogen atom, an alkyl group or an aryl group (provided that when R4 represents a hydrogen atom, R5 does not represent a hydrogen atom), an amino group of the formula -N(R4)(R5); - an amide group of the formula -C(=O)-N(R6)(R7) or -N(R6)C(=O)-(R7), in which R6 and R7 are identical or different and represent a hydrogen atom, an alkyl group or an aryl group; -n represents 0 or 1, X1 represents an oxygen atom or a sulfur atom, and X2, X3, and X4 are the same or different and represent a chemical bond, an oxygen atom, a sulfur atom, or -CR 10 R 11 - group, R8 and R9 are the same or different and each represent a hydrogen atom, an alkyl group, or an aryl group, and R 10 and R 11 are the same or different and represent a hydrogen atom or an alkyl group (such phosphorus functional groups include groups ranging from phosphonic acid groups to phosphine oxides and their mono- or di-thiolated equivalents), -R 12 , R 13 and R 14 are the same or different and represent an alkyl group or an aryl group, -N(R 12 )-C(=O)-CH2-O-CH2-C(=O)-N(R 13 )(R 14 ) a diglycolamide group of the formula -m represents 0 or an integer selected from the group consisting of 1, 2, 3 and 4, -[N(CH2COOH)-C2H4] m an amino or polyamino group having an acetyl group of the formula -N(CH2-COOH)2, -p represents 0 or an integer selected from the group consisting of 1, 2, 3, 4 and 5, (CH2)p sulfonic acid group (SO3H), -R 15 , R 16 and R 17 are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group; -NR 15 -C(=O)-N(R 16 )(R 17 ) a urea group of the formula polymeric or multidentate groups such as crown ethers, thioether crowns, calixarenes, porphyrins, phthalocyanines, pyrazolines, phenanthrolines, ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid (EDTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and diethylenetriaminepentaacetic acid (DTPA), and -Any combination of them.

[0034] In the case of an abstracting group of amino type of formula -N(R4)(R5), R4 and R5 are identical or different and advantageously represent an alkyl or aryl group.

[0035] In the present invention, the term "combination" refers to a combination of at least two identical or different groups selected from the above groups. These groups may be bonded to each other, or may substitute the same or different atoms in the hydrocarbon chain. Specific examples of such combinations include polyethyleneimino groups, amidothiophosphonic acid groups, aminosulfonic acid groups, or -R 18 and R 19 are the same or different and represent a hydrogen atom or an alkyl group; X5 and X6 are the same or different and represent a chemical bond or an oxygen atom; R 20 and R 21 are the same or different and represent an alkyl group or an aryl group; 18 R 19 -P(=O)(X5R 20 )(X6R 21 ) an aminophosphonic acid group of the formula:

[0036] By "alkyl group" (or Alk) is meant in the present invention a linear, branched or cyclic alkyl group containing 1 to 15 carbon atoms, in particular 1 to 12 carbon atoms, in particular 1 to 8 carbon atoms, which alkyl group may optionally contain at least one heteroatom and / or at least one carbon-carbon double or triple bond. The alkyl group may be substituted.

[0037] By "heteroatom" is meant, in the present invention, an atom selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, silicon, fluorine, chlorine and bromine.

[0038] The term "aryl group" as used herein means any group containing one aromatic ring or multiple identical or different aromatic rings linked or connected by a simple bond or a hydrocarbon chain, the aromatic rings having 3 to 20 carbon atoms, preferably 4 to 14 carbon atoms, and more preferably 5 to 8 carbon atoms, and optionally containing heteroatoms. The aryl group may be substituted.

[0039] The term "substituted alkyl / aryl group" as used herein means an alkyl / aryl group as defined above substituted with a group or groups, identical or different, selected from the group consisting of halogen, amine, diamine, carboxyl, carboxylate, aldehyde, ester, ether, thioether, ketone, hydroxyl, optionally substituted alkyl, amide, sulfonyl, sulfoxide, sulfonic acid, sulfonate, nitrile, nitro, acyl, epoxy, phosphonic acid, isocyanate, thiol, glycidoxy and acryloxy.

[0040] By "halogen" is meant, in the present invention, an atom selected from the group consisting of iodine, fluorine, chlorine and bromine.

[0041] In the present invention, functionalization of a geopolymer with an extracting group involves the formation of at least one covalent bond, and thus the extracting group is covalently attached, incorporated, or immobilized on the surface of the geopolymer, particularly on the surface of the mesopores and macropores of the geopolymer.

[0042] In the present invention, the attachment, incorporation, or immobilization of the extractive groups to the surface of the geopolymer can be direct or indirect. Thus, the functionalization of the geopolymer with the extractive groups can be direct. Alternatively, the functionalization of the geopolymer with the extractive groups can be indirect.

[0043] If direct, the covalent bond formed involves an atom present on the surface of the geopolymer and an atom of the abstracting group.

[0044] In the indirect case, attachment, incorporation or immobilization requires a connector, also called a "binding arm" or "grafting agent", which is bound on the one hand to the surface of the geopolymer and on the other hand to the extracting group. The bond formed is advantageously a covalent bond. The connector has a dual function: on the one hand, it provides flexibility to the structure, especially to the extracting group (carbon chemistry of the type polyethylene glycol (PEG), alkylene chains, polyethylene terephthalate (PET), etc.), and on the other hand, it attaches the extracting group to the geopolymer. Typically, the connectors implemented in the present invention are alkylene chains.

[0045] In the present invention, the term "alkylene chain" means a linear, branched or cyclic alkylene chain containing 1 to 30 carbon atoms, particularly 1 to 20 carbon atoms, and particularly 1 to 15 carbon atoms, and the alkylene chain may optionally contain at least one heteroatom.

[0046] When functionalization is direct, both the extracting group and the surface of the geopolymer have or are substituted with at least one identical or different reactive functional group to facilitate the formation of a covalent bond between the extracting group and the surface of the geopolymer. When a connector is used, the connector has a reactive functional group that can react with the same or different reactive functional group present on the surface of the geopolymer.

[0047] These reactive functional groups include, in particular, silane groups, silanol groups, amino groups, thiol groups, aldehyde groups, allyl groups, epoxy groups, R 22 , R 23 and R 24 are the same or different and represent an alkyl group as defined above, in particular methyl (Me) or ethyl (Et), -Si(OR 22 )(OR 23 )(OR 24 ) an alkoxysilane group of the formula:

[0048] In a first embodiment of the preparation of the geopolymer, a geopolymer mixture or grout is subjected to 3D printing. The preparation of the geopolymer thus comprises the following steps:

[0049] a1) preparing a geopolymer mixture; b1) subjecting the geopolymer mixture prepared in step a1) to 3D printing; and c1) The geopolymer mixture printed in step b1) is cured to obtain a geopolymer.

[0050] Step a1) of the method according to the invention involves adding to the activation solution defined above at least one pre-prepared source of aluminosilicate as defined above. This step and the pre-preparation of the activation solution are conventional steps in the field of geopolymers.

[0051] As mentioned above, the activation solution may optionally contain one or more silicate components, in particular selected from the group consisting of silica, colloidal silica and vitreous silica. When the activation solution contains one or more silicate components, said silicate components are present in the activation solution in an amount of 100 mM to 10 M, in particular 500 mM to 8 M, in particular 1 to 6 M.

[0052] The aluminosilicate source is added to the activation solution all at once or in batches. Once the aluminosilicate source has been added to the activation solution, the resulting solution or dispersion is mixed using a mixer, a magnetic stirrer, a magnetic stir bar, an ultrasonic bath or a homogenizer. The mixing / stirring in step i) of the method according to the invention is carried out at high speed. "High speed" in the present invention means that the rotor of the mixer or magnetic stirrer has a rotation speed of 1000 rpm or more, in particular 1500 rpm or more, and in particular 2000 rpm or more. Advantageously, this stirring is carried out using a magnetic stirrer or mixer. Any mixer known to those skilled in the art can be used in the present invention. Non-limiting examples include NAUTA® mixers, HOBART® mixers, HENSCHEL® mixers and HEIDOLPH® mixers.

[0053] Taking into account the possible silicate components that the activation solution may contain, the amount of aluminosilicate source is such that the SiO2 / Al2O3 molar ratio in the final geopolymer is 3.2-4.2, in particular 3.4-4.0, in particular about 3.8 (i.e. 3.8±0.1).

[0054] Furthermore, when activating solution denotes the mass of the activating solution expressed in g and MK denotes the mass of the aluminosilicate source used expressed in g, the activation solution / MK mass ratio is advantageously between 0.9 and 1.8, in particular between 1.2 and 1.5. As a specific example, the activation solution / MK ratio is about 1.36 (i.e., 1.36±0.10).

[0055] For direct 3D printing, it may be necessary to increase the viscosity of the geopolymer mixture used. In this case, a viscosity modifier can be added to the mixture. Any organic or non-organic viscosity modifier known to those skilled in the art can be used. Specific examples of such viscosity modifiers include fine powders or surfactants.

[0056] Fine powders, also called "fillers" or "additive fines", are finely divided dry products obtained from the cutting, milling or processing of natural rocks, aggregates and decorative stones. Advantageously, the fine powders have an average particle size of, in particular, 5 to 200 μm.

[0057] Surfactants that can be used to increase the viscosity of the geopolymer mixture are selected in particular from anionic surfactants, cationic surfactants, zwitterionic surfactants, amphoteric surfactants, and neutral (non-ionic) surfactants. More particularly, surfactants that can be used to increase the viscosity of the geopolymer mixture are selected from cationic surfactants, such as cetyltrimethylammonium bromide (CTAB).

[0058] The amount of viscosity modifier used in the present invention largely depends on the desired viscosity of the geopolymer mixture. A person skilled in the art will be able to determine the appropriate amount by routine testing. For example, the viscosity modifier is present in an amount of 0.1 to 20% by weight, particularly 0.5 to 15% by weight, and especially 1 to 10% by weight, based on the total weight of the geopolymer mixture.

[0059] Step a1) of the method according to the invention is carried out at a temperature between 10°C and 40°C, advantageously between 15°C and 30°C, more particularly at ambient temperature (i.e. 23°C ± 5°C), for more than 2 minutes, in particular between 4 minutes and 1 hour, in particular between 5 minutes and 15 minutes.

[0060] In a first specific embodiment, the geopolymer mixture prepared in step a1) comprises a pore-forming material as defined above.

[0061] In a second specific embodiment, the geopolymer mixture prepared in step a1) does not comprise any pore-forming materials.

[0062] In a third specific embodiment, the geopolymer mixture prepared in step a1) does not contain zeolites.

[0063] In a fourth specific embodiment, the geopolymer mixture prepared in step a1) does not comprise any pore-forming material or zeolite.

[0064] Step b1) of the method according to the invention involves subjecting the geopolymer mixture obtained in step a1) to 3D printing, which allows the geopolymer to be given a predetermined shape, in particular to obtain geopolymers of the geopolymer foam type and / or in the form of filters.

[0065] Any device usable for 3D printing can be used in the present invention, including, for example, 3D printers from the following suppliers: VormVrij, StoneFlower, Lynxter, 3D Potter, and WASP.

[0066] Step c1) of the method according to the invention involves subjecting the geopolymer mixture printed after step b1) to conditions allowing it to harden.

[0067] Any technique known to those skilled in the art for hardening geopolymer mixtures can be used during the hardening step.

[0068] The conditions allowing curing in step c1) advantageously comprise a curing step which can be carried out in open air or in water, which is advantageously carried out at a temperature of less than 30° C., in particular at ambient temperature, and which can last from 18 hours to 20 days, in particular from 24 hours to 16 days, in particular about 14 days (i.e. 14 days±1 day).

[0069] Finally, as mentioned above, no heat treatment, ie, at temperatures above 30° C., should be applied to the material after this curing step in order to open up its voids.

[0070] In a specific embodiment, steps a1), b1) and c1) of the preparation of the geopolymer are all carried out at ambient temperature.

[0071] In a second embodiment of the preparation of the geopolymer, the geopolymer mixture or grout is brought into contact with a sacrificial support obtained by 3D printing. The preparation of the geopolymer thus comprises the following steps:

[0072] a2) creating a sacrificial support by 3D printing; b2) contacting the sacrificial support prepared in step a2) with a pre-prepared geopolymer mixture; c2) curing the geopolymer mixture in contact with the sacrificial support; and d2) Obtaining the geopolymer by removing the sacrificial support.

[0073] In step a2) of the geopolymer preparation, a sacrificial support is printed with a fused deposition model 3D printer (FDM type), and the selected filament can have various chemical properties. However, the filament must be dissolvable by simple immersion in a solvent, such as an organic solvent. The printing parameters, such as the nozzle and bed outlet temperatures, are selected depending on the filament chemistry.

[0074] It is clear that the sacrificial support has the same chemical nature as the filaments. Advantageously, said filaments are organic polymers. Specific examples of filaments that can be used during step a2) include filaments made of high impact polystyrene (HIPS), water-soluble polyethylene oxide, nylon, polylactic acid (PLA), polycarbonate, polyurethane (PLU), polyacrylonitrile or poly(acrylonitrile / butadiene / styrene) (ABS).

[0075] All that has been said above for the preparation of the geopolymer mixture in step a1) applies to the preparation of the geopolymer mixture in step b2).

[0076] However, it should be noted that inverse 3D printing allows the use of geopolymer mixtures with more variable viscosity than those used in direct 3D printing. Thus, the viscosity of the geopolymer mixtures used in inverse 3D printing is higher at a shear rate of 0.1 s -1 The viscosity of the geopolymer mixture used for direct 3D printing is between 1 Pa·s and 200 Pa·s at a shear rate of 0.1 s. -1 can be greater than 1000 Pa·s.

[0077] Thus, step b2) involves immersing or submerging the sacrificial support in the geopolymer mixture, or pouring this mixture onto the sacrificial support. After this immersion, it may be necessary to remove any remaining air bubbles in the geopolymer mixture by subjecting the assembly (geopolymer mixture + sacrificial support) to the action of ultrasound. This treatment can be carried out for 15 seconds to 1 minute, in particular for about 30 seconds (30 seconds ± 5 seconds).

[0078] All that has been said above for step c1) applies mutatis mutandis to step c2).

[0079] Finally, in step d2), the porosity of the geopolymer is opened by dissolving the polymeric sacrificial supports present in the material obtained after step c2). For this purpose, the mixture is immersed under stirring in a solvent capable of dissolving the sacrificial supports and is kept in this state until its mass stabilizes. The geopolymer thus prepared has a controlled porosity.

[0080] Examples of solvents that can be used during step d2) include water, ethyl acetate, acetone, ethanol, isopropanol, tetrahydrofuran (THF), dioxane or dichloromethane.

[0081] The removal of the sacrificial support in step d2) and the functionalization of the geopolymer with one or more abstracting groups in step i) defined below can be carried out simultaneously, under conditions corresponding to those of step i) defined below.

[0082] The geopolymer can be dried in air or in an oven after the sacrificial support has been removed, especially at temperatures below 30° C. However, this drying step is optional.

[0083] Before step d2), it may be necessary to prepare the surface of the material obtained after step c2) in order to expose the surface of the sacrificial support. Indeed, the material obtained after step c2) may be in the form of a geopolymer with the sacrificial support trapped inside. This preparation is typically carried out by mechanical cutting, for example using a circular saw or a wire saw or a chainsaw equipped with a diamond disc.

[0084] In the method according to the invention, regardless of the embodiment of the preparation of the geopolymer, said geopolymer is then functionalized with one or more of the same or different extracting groups defined above.

[0085] This functionalization advantageously comprises the following steps:

[0086] i) contacting a molecule comprising at least one abstracting group and at least one reactive functional group, as defined above, with a geopolymer under conditions that allow the formation of at least one covalent bond between said molecule and said geopolymer; and ii) Obtaining a geopolymer functionalized with at least one extracting group by removing the molecules that did not react with the geopolymer during step i).

[0087] The molecule used in step i) can contain at least one reactive functional group directly attached to the extracting group, which is the case when direct functionalization is carried out.

[0088] In the case of indirect functionalization, the molecule used in step i) may comprise at least one reactive functional group directly attached to a connector as defined above, which itself is directly attached to an extracting group.

[0089] The molecules used in step i) can be commercially available molecules or molecules that are synthesized by conventional chemical techniques before carrying out the functionalization step.

[0090] Table 1 below lists some examples of molecules ("final compounds") that can be used to functionalize geopolymers and identifies the ions that are captured by the extractable groups of these molecules.

[0091] [Table 1]

[0092] When used in step i), the molecules are diluted in a solvent called "grafting solvent". Advantageously, said solvent is selected from organic solvents such as acetone, ethyl acetate, THF and dioxane; alcohols such as methanol, ethanol and isopropanol; chlorosolvents such as dichloromethane and chloroform; aliphatic solvents such as alkanes; aromatic solvents such as toluene and xylene; supercritical fluids such as supercritical CO2 and supercritical butane; and mixtures thereof. Specific examples of mixtures include mixtures of the supercritical fluids defined above with organic solvents.

[0093] It will be easy for a person skilled in the art to choose the most suitable solvent depending on the molecule used and the amount thereof used in step i).

[0094] The conditions used in step i) that allow the molecules to attach to the surface of the geopolymer depend on the reactive functional groups of the molecules. For example, these conditions can include heating and / or stirring. This heating can be conventional or microwave heating; the temperature during this treatment is between 40°C and 150°C, in particular between 40°C and 120°C, depending on the boiling point of the solvent used.

[0095] Usually, step i) of the method according to the invention lasts from 1 hour to 18 hours.

[0096] Before step i) of the method according to the invention, the geopolymer can be subjected to a pretreatment, in particular an acidic pretreatment, which makes it possible to increase the number of "graftable" functional groups on the surface of the geopolymer. Once this pretreatment has been carried out, the geopolymer can be dried.

[0097] Step ii) according to the invention aims to remove molecules carrying extractable groups that have not reacted with the surface of the geopolymer, in particular that have not been covalently bound to this surface. This step ii) corresponds to at least one washing step.

[0098] Advantageously, step ii) of the method according to the invention comprises one (or more) washings of the surface of the geopolymer on which one or more extraction groups are immobilized with the same or different washing solutions. In particular, step ii) of the method according to the invention comprises at least two, at least three, at least four or at least five washings of the surface of said geopolymer. Those skilled in the art will be able to easily define the number of washings necessary and sufficient depending on the molecules and their concentrations used in step i) of the method, as well as the washing solutions used.

[0099] The washings can be carried out with the same or different washing solutions. Indeed, in step ii) it is possible to use the same washing solution for each wash, different washing solutions for each wash, or the same or different washing solutions for each wash. The washings can be carried out for the same or different times, these times being between 1 hour and 1 week, in particular about 48 hours (48 hours ± 2 hours). Step ii) of the process according to the invention is advantageously carried out under stirring and at ambient temperature.

[0100] In step ii) of the method according to the present invention, any washing solution known to those skilled in the art can be used.By way of example and not limitation, the solvent of the washing solution carried out in step ii) of the method according to the present invention can be selected from organic solvents such as tetrahydrofuran (THF) and dioxane; alcohols such as methanol, ethanol and isopropanol; chlorosolvents such as dichloromethane and chloroform; aliphatic solvents such as alkanes; aromatic solvents such as toluene and xylene; supercritical fluids such as supercritical CO2 and supercritical butane; and mixtures thereof, in particular as defined above.

[0101] After the final washing step ii) of the method according to the invention, the functionalized geopolymer obtained can be dried before any further use. Ideally, this drying is carried out at atmospheric pressure and ambient temperature or under a flow of air, for example under a fume hood.

[0102] The main steps of the method for preparing a geopolymer capable of trapping at least one ion according to the present invention are shown schematically in FIG.

[0103] The present invention also relates to a geopolymer capable of trapping at least one ion, prepared according to the method defined above. Everything stated above regarding this functionalized geopolymer applies to this aspect of the invention.

[0104] Thus, the geopolymer according to the invention is in the form of a mesoporous geopolymer, optionally with unconnected macropores, or in the form of a foam, and is functionalized, directly or indirectly, with at least one ion-specific extracting group that does not contain an -NH2-amine group.

[0105] Finally, the present invention relates to the use of such functionalized geopolymers for separating at least one ion, such as a metal or metalloid ion, from a stream containing said at least one ion, such as a metal or metalloid ion.

[0106] The present invention therefore relates to a method for separating at least one ion, such as a metal or metalloid ion, from a stream comprising said at least one ion, such as a metal or metalloid ion, which method involves contacting a functionalized geopolymer according to the present invention with the stream comprising at least one ion, such as a metal or metalloid ion, to obtain a stream depleted in ions, such as metal or metalloid ions, and a surface of the geopolymer on which ions, such as metal or metalloid ions, are immobilized via extraction groups present on the surface.

[0107] In other words, the method according to the present invention can be considered as a method for treating a stream containing at least one ion, such as a metal or metalloid ion. "Treatment of a stream containing at least one ion, such as a metal or metalloid ion" means reducing the amount of ions, such as metal or metalloid ions, present in the stream before carrying out the method according to the present invention, i.e., before contact with the functionalized geopolymer. This reduction can involve partial or total removal of these ions in the stream. This embodiment is also shown schematically in Figure 1.

[0108] Indeed, the excellent mechanical strength and stability of the functionalized geopolymers prepared by the method according to the invention, resulting from their specific structure, allows their preparation in a column and the continuous implementation of the separation / fixation method, for example in a fluidized bed, and therefore allows them to be easily integrated, for example in existing facilities, in a processing chain or line comprising several steps.

[0109] After the separation method according to the invention, the elements (such as anions or cations) present in the stream to be treated are immobilized in the functionalized geopolymer according to the invention by adsorption, chelation or complexation with the extracting groups themselves attached to the surface of the geopolymer, this attachment being advantageously covalent.

[0110] "Stream containing at least one ion, such as a metal or metalloid ion" means a liquid or gas stream from which the present invention aims to separate, recover or remove unwanted metal or metalloid ions or, conversely, metal or metalloid ions of interest. Thus, the stream implemented in the present invention may be any liquid or gas stream that can contain at least one metal or metalloid ion, such as an ion, as defined above.

[0111] Advantageously, the stream containing at least one ion, such as a metal or metalloid ion, used in the present invention is a liquid stream. The liquid stream can be in the form of a single-phase solution, a microemulsion, a suspension, and / or a dispersion. The liquid stream used can be an aqueous solution, which can optionally contain an acid, a base, or an organic compound. Alternatively, the solution can be a solution of an aliphatic compound, such as an alkane or alkene, an aliphatic or non-aliphatic alcohol, an active molecule, such as a surfactant or an extractant, a mixture of these organic solvents, or a mixture of water and one or more of these organic solvents. The solution can further contain an active molecule, such as a surfactant, such as octanol, sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB), or an extractant, such as aliphatic amines, organic phosphates, and derivatives of amides.

[0112] Examples of liquid or gas streams that may be practiced in the present invention include those selected from the group consisting of ambient air samples, air samples from chemical, agri-food, pharmaceutical, cosmetic or nuclear industries, municipal water, river water, sea water, lake water, discharges from wastewater treatment plants, wastewater, domestic liquid discharges, medical or hospital liquid discharges, industrial liquid discharges such as discharges from the nuclear industry or other activities related to the nuclear industry, discharges from non-nuclear industries, and mixtures thereof.

[0113] The various liquids and effluents of the nuclear industry, nuclear installations and activities carrying out radionuclides that can be treated with the functionalized geopolymers prepared by the method according to the invention include, for example, the cooling waters and wash waters of power plants, regeneration solutions of resins or all the various effluents that come into contact with radioisotopes, such as organic effluents from research and development activities.

[0114] Various liquids and effluents from non-nuclear industries include cement plant effluents, which contain thallium, a highly toxic substance, or effluents from the paper industry.

[0115] Thus, the streams and solutions that can be treated with the functionalized geopolymers that immobilize ions, such as metal or metalloid ions, prepared by the method according to the invention are very diverse, and may contain competitive, corrosive, or other extractants due to the excellent chemical stability of the geopolymers according to the invention. The functionalized geopolymers prepared by the method according to the invention are particularly usable over a very wide pH range, for example, from neutral pH to pH 10.

[0116] In general, by appropriate selection of the abstraction groups on its surface, the functionalized geopolymer according to the present invention can be used to immobilize, chelate, complex or capture any given ion. By "ion" we mean either a cation or an anion, whether said cation or said anion is an impurity, a contaminant, or a recyclable cation or anion such as lithium.

[0117] In a specific embodiment, the ions immobilized, chelated, complexed or trapped by geopolymers according to the invention are metal or metalloid ions.

[0118] By "metal or metalloid ions" is meant in the present invention unwanted metal or metalloid ions (such as impurities or contaminants) or, conversely, metal or metalloid ions of interest that may be or are present in the stream as defined above. Said metal or metalloid ions may furthermore be toxic, harmful and / or radioactive.

[0119] The present invention can be implemented with any metal or metalloid ion known to those skilled in the art. Advantageously, the metal ions are ions of base metals, alkaline earth metals, transition metals, actinides or lanthanides. The metal or metalloid ions to which the present invention relates also include ions of heavy metals or heavy metalloids. For the avoidance of doubt, heavy metals or metalloids are defined as those with a density of 5 g / cm or less, such as mercury, lead, cadmium, copper, arsenic, nickel, zinc, cobalt and manganese. 3 It is a metal or metalloid element exceeding 1000 ppm.

[0120] Advantageously, the metal or metalloid ions in the context of the present invention are ions of a metal or metalloid as defined above, in particular having two or more oxidation states. In particular, the metal or metalloid ions may be ions of radionuclides.

[0121] As illustrative examples, metal or metalloid ions in the present invention may be ions of elements selected from mercury, gold, silver, platinum, lead, iron, indium, gallium, aluminum, bismuth, tin, cadmium, copper, lithium, arsenic, nickel, zinc, titanium, cobalt, manganese, palladium, curium, americium, radium, ruthenium, thorium, uranium, plutonium, actinium, ytterbium, erbium, terbium, gadolinium, europium, neodymium, praseodymium, cerium, cesium, thallium, strontium, and lanthanum.

[0122] In the present invention, ions such as metal or metalloid ions may be present in free form or in the form of colloids or complexes, where the latter may be derived from a stable metal or metalloid or a radioactive isotope of either.

[0123] Ions, such as metal or metalloid ions, may be present in the stream to be treated in a very diluted form or in a much more concentrated form, and thus the amount of said ions in the liquid stream may be between 1 pg and 100 mg per liter of liquid stream, in particular between 1 μg and 10 mg per liter of liquid stream, and in particular between 10 μg and 1 mg per liter of liquid stream.

[0124] Typically, the separation process implementing the functionalized geopolymers that are the subject of the present invention is carried out continuously, in particular by using this geopolymer in particulate form and by preparing it in column form, for example, so that the geopolymer forms a fluidized bed, the fluidization of which is ensured by the flow to be treated. Alternatively, the separation process can also be carried out discontinuously in "batch" mode, the contact between the geopolymer and the flow to be treated being advantageously carried out under stirring. The preparation in a column makes it possible to continuously treat a sufficient amount of flow at a high flow rate.

[0125] The contact time between the stream to be treated and the functionalized geopolymer forming the subject of the present invention can be variable and can be, for example, from 1 minute to 1 hour in the case of continuous operation, for example, from 10 minutes to 36 hours and for example 24 hours in the case of "batch" operation.

[0126] Furthermore, the functionalized geopolymers may be in the form of monoliths and can be used as conditioning materials to trap elements that are contained and leached out during the conditioning.

[0127] Other characteristics and advantages of the present invention will become apparent to those skilled in the art upon reading the examples given below, given for illustrative and non-limiting purposes, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0128] [Figure 1] FIG. 1 is a diagram of the main steps of a method for preparing a geopolymer capable of trapping at least one ion and its use in the decontamination of a liquid effluent containing said at least one ion. [Figure 2] Figure 2 shows photographs of the materials obtained during the various steps that allow the creation of geopolymers with controlled porosity. The sample shown has a theoretical porosity of about 25% by volume. [Figure 3] Figure 3 shows photographs tracking the process over time that allows the creation of geopolymers with controlled porosity (the sample shown has a theoretical porosity of about 25% by volume). [Example]

[0129] I. Methods for preparing geopolymers with controlled porosity.

[0130] I.1. Direct 3D printing method. Step 0: Modeling of the percolation network on a computer, the shape of the filling of the part is selected to correspond to the complex shape. Step 1: Printing the part on a fused deposition model 3D printer (FDM type). The selected filament is a geopolymer with the following composition expressed in molar units: 3.8 SiO2:1.0 Al2O3:1.0 Na2O:11.0 H2O. The printing parameters are as follows: - Layer height: 0.5mm, -Nozzle size: 0.8mm, -Filling type: Gyroid, -Filling rate: 20~80%, No heating of the bed or nozzle, this technique corresponds to the deposition of fresh geopolymer paste.

[0131] I.2. Inverse 3D printing method. The protocol followed to create geopolymers by inverse 3D printing is as follows.

[0132] Step 0: Modeling of the sacrificial support on a computer, the shape of the filling of the part is chosen to correspond to the complex shape. Step 1: Printing the part on a fused deposition model 3D printer (FDM type). The selected filament is HIPS. The printing parameters are a nozzle temperature of 240°C and a print bed temperature of 110°C. Step 2: i. Composition of the geopolymer mixture, which involves mixing the activation solution and metakaolin in proportions corresponding to the following composition, expressed in molar units: 3.8 SiO2:1.0 Al2O3:1.0 Na2O:11.0 H2O. For this, 54.2 g of BETOL 52T (aluminosilicate source), 0.5 g of water, 2 g of NaOH and 43.3 g of IMERYS M1000 metakaolin are used. The whole is then placed under stirring to homogenize the geopolymer paste. ii. Immersion of a polymer sacrificial support into the geopolymer paste. The sample is then placed under ultrasound for 30 seconds to remove any residual air bubbles in the geopolymer. Other techniques can be used, such as placing it under vacuum to remove any residual air bubbles, or using a specific mold (i.e., a suitable syringe) that allows the paste to be forced into the sacrificial support. Step 3: In this step, the composite (geopolymer with sacrificial support) is cured for 7 days to ensure that the geopolymer retains sufficient mechanical strength for the next step. Surface preparation of the sample is required to expose the surface of the sacrificial support. Both ends of the geofilter are cut with a circular saw or wire saw to expose the channels in the sacrificial support. Step 4: Opening of porosity by dissolving the polymer (HIPS) present in the material. For this purpose, the material is immersed in dichloromethane under stirring and left until its mass stabilizes. The material thus prepared has a controlled porosity.

[0133] After drying (in an oven or in air at temperatures between ambient and 30° C. for a period of 2 to 4 hours), the material is ready for the next step of the method (grafting).

[0134] Steps 1 to 4 are shown in Figure 2 for a geopolymer with a porosity of 25% by volume relative to the total volume. The photograph of step 1 corresponds to the sacrificial support made of HIPS obtained by 3D printing. The photograph of step 2 corresponds to its filling with the geopolymer matrix. The photograph of step 3, taken after the geopolymer has hardened, corresponds to a cross-section of the resulting material, where the encapsulation of the sacrificial support within the geopolymer can be observed. The photograph of step 4, taken after the dissolution of the sacrificial support made of polymer and the opening of its voids, corresponds to a cross-section of the resulting geopolymer, where voids in the geopolymer corresponding to the location of the sacrificial support can be observed.

[0135] Figure 3 corresponds to step 4, where the sacrificial support made of HIPS is dissolved, and complex and controlled shapes can be observed inside the material.

[0136] II. Methods for functionalizing this controlled porosity geopolymer.

[0137] The grafting step is carried out after the void opening step.

[0138] The pretreatment step 0 is optional. However, if step 0 is not included, step 4 of "Opening pores" in the "Preparation of geopolymers with controlled pores" process can be performed simultaneously with step 2 of grafting.

[0139] Step 0: Acidic pretreatment and drying of geopolymer filters. The filter is immersed in a 0.1 M nitric acid solution at ambient temperature with gentle stirring, avoiding contact between the stirring mechanism and the filter. The filter is immersed in the toluene solution at ambient temperature with gentle stirring, avoiding contact between the stirring mechanism and the filter. Step 1: The grafting agent used is [3-(diethylamino)propyl]trimethoxysilane, CAS: 41051-80-3 and having the following formula: [ka] Step 2: Graft the extracting groups onto the geopolymer by contacting the grafting agent with the geopolymer and heating overnight in dichloromethane under reflux (40°C) (1 mmol of grafting agent / 1 g of geofilter / 10 mL of solvent). Step 3: Repeated washing with dichloromethane in a Soxhlet apparatus to wash out residual impurities (150 mL of solvent under reflux overnight on a filter placed in a cellulose cartridge). Step 4: The sample is dried in an oven (80°C, overnight), the material is then ready for analysis.

[0140] III. Characterization of the obtained functionalized geopolymers.

[0141] The geopolymers obtained by the method according to the invention can be characterized by various techniques, including gravimetry, porosimetry (gas, mercury), nuclear magnetic resonance such as MAS-NMR (Magic Angle Spinning-NMR), infrared spectroscopy such as Fourier Transform Infrared Spectroscopy (FTIR), and differential scanning calorimetry (DSC) coupled with thermogravimetry.

[0142] Table 2 below shows the post-grafting properties of a geopolymer with 25% porosity by volume functionalized with a grafting reagent, [3-(diethylamino)propyl]trimethoxysilane, whose reactive functional group is trimethoxysilane and whose extracting group connector is diethylpropylamine.

[0143] This extractant can be aimed at the extraction of actinides (uranium) from organic solutions, but can also be used for water purification of transition metals / metalloids (e.g., arsenic, lead, copper, cadmium).

[0144] The appearance of MAS-NMR signals in the 13C spectrum (analysis of NMR signals obtained directly by solid analysis) typical of alkyl chains attached to amines, and the overall increase in mass correlated with a decrease in the specific surface area (coupled with the coverage of the surface by organic functional groups), confirm the functionalization by grafting of the porous geopolymers produced by Inverse 3D.

[0145] [Table 2] [Prior art documents] [Non-patent literature]

[0146] [Non-Patent Document 1] Steins et al, 2014, “Effect of aging and alkali activator on the porous structure of a geopolymer”, Journal of Applied Crystallography, vol. 47, pages 316-324. [Non-patent document 2] Lee et al, 2017, “Adsorption characteristics of cesium onto mesoporous geopolymers containing nano-crystalline zeolites”, Microporous and Mesoporous Materials, vol. 242, pages 238-244. [Non-patent document 3] Luukkonen et al, 2020, “Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation”, Scientific Reports, vol. 10, pages 1-14. [Non-Patent Document 4] Cepollaro et al, 2021, “Cu-exchanged 3D-printed geopolymer / ZSM-5 monolith for selective catalytic reduction of NOx”, Chemical Engineering Transactions, vol. 84, pages 67-72.

Claims

1. 1. A method for preparing a geopolymer capable of trapping at least one ion, comprising: A geopolymer preparation process, including at least one step in which 3D printing is used; and specific for said at least one ion, -NH ２ functionalizing the geopolymer thus prepared with at least one abstracting group that does not have an amino group.

2. 10. The method of claim 1, wherein the geopolymer is a mesoporous geopolymer having optionally unconnected macropores.

3. The method of claim 1 , wherein the geopolymer is a geopolymer foam.

4. The at least one abstracting group is R １ , R ２ and R ３ are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group; ＋ (R １ ) (R ２ ) (R ３ ) an ammonium group of the formula: R ４ and R ５ are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group (provided that R ４ When represents a hydrogen atom, R ５ does not represent a hydrogen atom)-N(R ４ ) (R ５ ) an amino group of the formula: R ６ and R ７ are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group; ６ ) (R ７ ) or -N(R ６ )C(=O)-(R ７ ) an amide group of the formula: n represents 0 or 1; X １ represents an oxygen atom or a sulfur atom, and X ２ , X ３ and X ４ are the same or different and are a chemical bond, an oxygen atom, a sulfur atom, or -CR １０ R １１ represents a - group, and R ８ and R ９ are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group; R １０ and R １１ are the same or different and represent a hydrogen atom or an alkyl group; ２ -P (=X １ ) ｎ (X ３ R ８ ) (X ４ R ９ ) a phosphorus group of the formula: R １２ , R １３ and R １４ are the same or different and represent an alkyl group or an aryl group. １２ )-C(=O)-CH ２ -O-CH ２ -C(=O)-N(R １３ ) (R １４ ) a diglycolamide group of the formula: m represents 0 or an integer selected from the group consisting of 1, 2, 3 and 4, -[N(CH ２ COOH)-C ２ H ４ ] ｍ -N(CH ２ -COOH) ２ an amino or polyamino group having an acetyl group of the formula: p represents 0 or an integer selected from the group consisting of 1, 2, 3, 4 and 5 (CH ２ ) ｐ (SO ３ H) sulfonic acid group; R １５ , R １６ and R １７ are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group; １５ -C(=O)-N(R １６ ) (R １７ ) a urea group of the formula: Polymeric or multidentate groups such as crown ethers, thioether crowns, calixarenes, porphyrins, phthalocyanines, pyrazolines, phenanthrolines, ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid (EDTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and diethylenetriaminepentaacetic acid (DTPA); The method of any one of claims 1 to 3, wherein the compound is selected from the group consisting of:

5. 5. The method according to any one of claims 1 to 4, wherein the functionalization of the geopolymer with at least one abstracting group is direct.

6. 5. The method according to any one of claims 1 to 4, wherein the functionalization of the geopolymer with at least one extracting group is indirect, a connector being attached on the one hand to the surface of the geopolymer and on the other hand to the extracting group.

7. 2. The method of claim 1, wherein the preparation of the geopolymer comprises: Step a of preparing a geopolymer mixture １ ), Process a １ Step b) subjecting the geopolymer mixture prepared in step b) to 3D printing １ ), and Process b １ Step c) of obtaining a geopolymer by hardening the printed geopolymer mixture １ ), including The method according to any one of claims 1 to 6.

8. 2. The method of claim 1, wherein the preparation of the geopolymer comprises: Step a. Creating a sacrificial support by 3D printing ２ ), Process a ２ Step b) contacting the sacrificial support prepared in step b) with a pre-prepared geopolymer mixture ２ ), c) contacting the geopolymer mixture with the sacrificial support and curing it; ２ ), and Step d) of obtaining a geopolymer by removing the sacrificial support ２ ), including The method according to any one of claims 1 to 6.

9. i) contacting the geopolymer with a molecule comprising at least one abstracting group and at least one reactive functional group under conditions that allow the formation of at least one covalent bond between the molecule and the geopolymer; and ii) removing the molecules that did not react with the geopolymer during step i) to obtain a geopolymer functionalized with at least one extracting group; The method according to any one of claims 1 to 8.

10. A geopolymer capable of trapping at least one ion, prepared according to the method defined in any one of claims 1 to 9, said geopolymer being in the form of a mesoporous geopolymer, optionally with disconnected macropores, or in the form of a foam, and functionalized directly or indirectly with an extracting group specific for at least one ion, said extracting group being -NH ２ -A geopolymer that does not contain amino groups.

11. 11. Use of the geopolymer of claim 10 for separating said at least one ion from a stream containing said at least one ion.

12. 12. The use according to claim 11, wherein the flow containing the at least one ion is selected from the group consisting of an outdoor air sample, an air sample from an industry in the chemical, agri-food, pharmaceutical, cosmetic or nuclear sector, municipal water, river water, sea water, lake water, effluent from a wastewater treatment plant, wastewater, domestic liquid effluent, medical or hospital liquid effluent, industrial liquid effluent, and one of their mixtures.

13. 13. The use according to claim 11 or 12, wherein the ion is a metal or metalloid ion.

14. 14. The use according to claim 13, wherein the metal or metalloid ion is an ion of an element selected from mercury, gold, silver, platinum, lead, iron, indium, gallium, aluminum, bismuth, tin, cadmium, copper, lithium, arsenic, nickel, zinc, titanium, cobalt, manganese, palladium, curium, americium, radium, ruthenium, thorium, uranium, plutonium, actinium, ytterbium, erbium, terbium, gadolinium, europium, neodymium, praseodymium, cerium, cesium, thallium, strontium and lanthanum.

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