Process for preparing an adsorbing material comprising a precipitating step of boehmite according to specific conditions and process for extracting lithium from saline solutions using this material
The present invention relates to the field of solid materials for adsorption of lithium. In particular, the present invention relates to a novel method for preparing a crystallized and shaped solid material, preferably as extrudates, of formula LiX x .2Al(OH) 3 , nH 2 O with n being comprised between 0.01 and 10, x being equal to 1 when X is an anion selected from among chloride, hydroxide and nitrate anions, and x being equal to 0.5 when X is an anion selected from among sulfate and carbonate anions, comprising a step a) for precipitation of boehmite under specific temperature and pH conditions, at least one shaping step, preferably by extrusion, said method also comprising a final hydrothermal treatment step, the whole giving the possibility of increasing the adsorption capacity for lithium as well as the adsorption kinetics of the materials obtained as compared with the materials of the prior art when the latter is used in a method for extracting the lithium from saline solutions.
1. A method for preparing a crystallized solid material of formula LiX x .2Al(OH) 3 ,nH2O with n being comprised between 0.01 and 10, x being equal to 1 when X is an anion selected from among chloride, hydroxide and nitrate anions, and x being equal to 0.5 when X is an anion selected from among sulfate and carbonate anions, said method comprising:
a) precipitating boehmite in an aqueous medium, wherein the precipitation comprises contacting at least one basic precursor; and at least one acid precursor, wherein at least one of the basic or acid precursors comprises aluminium, thereby obtaining a suspension of boehmite, said precipitating being performed at a temperature comprised between 5 and 35° C., and wherein the amount of the basic precursor gives a pH at the end of precipitation in the reaction medium comprised between 7.5 and 9.5,
b) washing and filtering the boehmite precipitate obtained in a),
c) putting the precipitate obtained in b) in contact with at least one lithium source thereby obtaining a suspension,
d) filtering the suspension obtained in c) thereby obtaining a slurry,
e) drying the slurry obtained at the end of d) at a temperature comprised between 20 and 80° C.,
f) shaping said dried slurry,
g) drying the shaped material obtained at the end of f) at a temperature comprised between 20 and 200° C., and
h) hydrothermally treating the dry shaped material obtained at the end of g) at a temperature comprised between 50 and 200° C.
2. The method according to claim 1 , wherein said basic precursor is selected from the group consisting of sodium aluminate, potassium aluminate, ammonia, sodium hydroxide, potassium hydroxide, and any mixture thereof.
3. The method according to claim 1 , wherein said basic precursor is sodium hydroxide (NaOH).
4. The method according to claim 1 , wherein said acid precursor is selected from the group consisting of aluminium sulfate, aluminium chloride, aluminium nitrate, sulfuric acid, hydrochloric acid, nitric acid, and any mixture thereof.
5. The method according to claim 1 , wherein said acid precursor is aluminium trichloride (AlCl 3 ).
6. The method according to claim 1 , wherein said precipitating is performed at a temperature comprised between 10 and 25° C.
7. The method according to claim 1 , wherein the amount of the basic precursor gives a pH at the end of precipitation in the reaction medium comprised between 7.7 and 8.8.
8. The method according to claim 1 , wherein said lithium source is selected from the group consisting of lithium chloride (LiCl), lithium hydroxide (LiOH), lithium nitrate (LiNO 3 ), lithium sulfate (Li 2 SO 4 ) and lithium carbonate (Li 2 CO 3 ), and any a mixture thereof.
9. The method according to claim 8 , wherein said lithium source is lithium chloride (LiCl).
10. The method according to claim 1 , wherein said shaping is achieved by extrusion.
11. The method according to claim 10 , wherein said shaping is directly applied after the drying.