Process for preparing an adsorbent material and process for extracting lithium using said material
The present invention relates to the field of solid materials for the adsorption of lithium. In particular, the present invention relates to a novel process for preparing a solid crystalline material formed preferably in extrudate form, of formula (LiCl) x .2Al(OH) 3 ,nH 2 O with n being between 0.01 and 10, x being between 0.4 and 1, comprising a step a) to precipitate boehmite under specific conditions of temperature and pH, a step to place the precipitate obtained in contact with a specific quantity of LiCl, at least one forming step preferably via extrusion, said process also comprising a final hydrothermal treatment step, all allowing an increase in lithium adsorption capacity and in the adsorption kinetics of the materials obtained compared to prior art materials, when used in a process to extract lithium from saline solutions.
1. A process for preparing a solid crystalline material of formula (LiCl) x .2Al(OH) 3 .nH 2 O, wherein n is between 0.01 and 10, and x is between 0.4 and 0.6, said process comprising:
a) precipitating boehmite, in an aqueous medium, comprising the contacting of at least one base precursor with at least one acid precursor, wherein at least one of the base or acid precursors comprises aluminium, to obtain a suspension of boehmite, said precipitating being conducted at a temperature of between 5 and 35° C., and the amount of base precursor being selected so as to obtain an end-precipitation pH of between 7.5 and 9.5 in the reaction medium;
b) washing and filtering the precipitate of boehmite obtained in a);
c) placing the precipitate obtained in b) in contact with a quantity of lithium chloride equivalent to a Li/AI molar ratio of between 0.3 and 0.5;
d) filtering the suspension obtained in c) to obtain a paste;
e) drying the paste obtained in d) at a temperature of between 20° C. and 80° C.;
f) shaping said dried paste; and
g) drying the shaped dried paste obtained in f) at a temperature of between 20° C. and 200° C.
2. The process according to claim 1 , wherein the base precursor is sodium hydroxide (NaOH).
3. The process according to claim 1 , wherein said precipitating is conducted at a temperature of between 10 and 25° C.
4. The process according to claim 1 , wherein the amount of base precursor is selected so as to obtain an end-precipitation pH in the reaction medium of between 7.7 and 8.8.
5. The process according to claim 1 , wherein c) is conducted for a time of between 15 minutes and 5 hours.
6. The process according to claim 1 , wherein f) is implemented via extrusion.
7. The process according to claim 6 , wherein f) is implemented directly after e).
8. The process according to claim 6 , wherein f) is implemented via base knead-extrusion wherein said dried paste derived in e) is kneaded in the presence of an amount of base of between 0.5 and 3 weight % relative to the dry matter, the dry matter being the weight of said paste derived from e), said base being selected from the group consisting of inorganic bases and organic bases in solution, and wherein said paste is then subjected to an extrusion.
9. The process according to claim 1 , wherein said base precursor is selected from the group consisting of sodium aluminate, potassium aluminate, ammonia, sodium hydroxide, potassium hydroxide, and any mixtures thereof.
10. The process according to claim 1 , wherein said acid precursor is selected from the group consisting of aluminium chloride, hydrochloric acid, and any mixtures thereof.