A process for extracting lithium, aluminum, and
- silicon materials from lithium-containing aluminosilicate minerals, including spodumene, ˜LiAlSi2O6, comprising at least the steps of:
- providing a hard-rock source in the form of a granular concentrate of one or more lithium-containing aluminosilicate minerals, including spodumene (Step 1);
- calcining the concentrate at an elevated temperature sufficient to convert substantially all of the spodumene therein from its natural alpha (α) polymorphic crystal structure to a synthetic beta (β) crystal structure (Step 2);
- providing an aqueous solution of nitric acid (HNO3) (Step 3);
- mixing the calcined concentrate with the aqueous solution of nitric acid, and then subjecting the resulting mixture to conditions sufficient to effect leaching of lithium (Li) and aluminum (Al) from the calcined concentrate in a first primary reactor (Step 4) and, optionally, further reacting the concentrate with nitric acid in one or more secondary reactor(s), to form a slurry (optional Step 5);
- transferring the slurry from the first primary reactor, or from the one or more optional secondary reactors, to a second primary reactor with a lower gas pressure to reduce the pressure of the transferred slurry (Step 6);
- removing the slurry from the second primary reactor and allowing the slurry to cool down (Step 7);
- separating the cooled slurry into two fractions, where one fraction contains leached granular β-spodumene, and the other fraction is a LiNO3(aq)- and Al(NO3)3(aq)-containing liquid, the leached granular β-spodumene-containing fraction being transferred to a mixer where it is washed with water, separated from that washwater, and then, optionally, contacted with an aqueous solution of Na and/or K hydroxide under conditions sufficient to dissolve Li, Al, and SiO2, and then subjected to recovery of:
- (i) Li as one or more of Li2CO3, LiOH(aq), LiOH·xH2O (where x=1, 2, 3, or 6), and/or Li2O·ySiO2 (where y=1 or 2);
- (ii) Al as one or more of Al(OH)3, Al2O3·H2O, and/or Al2O3;
- and (iii) SiO2 as either retained in (Na,K)2SiO3(aq) and/or as precipitated silica and/or as precipitated silica gel (Step 8);
- and
- combining the LiNO3(aq)- and Al(NO3)3(aq)-containing washwater from the mixer with the LiNO3(aq)- and Al(NO3)3(aq)-containing liquid fraction in a third primary reactor, and then subjecting the resulting liquid mixture to one of two treatments to induce precipitation of “Al(OH)3(s),” either (i) a thermal treatment at a temperature sufficient to decompose the Al(NO3)3(aq) in the liquid mixture, or (ii) “a (NH4)2CO3 treatment” that involves bringing the LiNO3(aq)- and Al(NO3)3(aq)-containing liquid mixture into contact with (NH4)2CO3(aq) and/or (NH4)2CO3(s) (Step 9).