Processes for preparing highly pure lithium carbonate and other highly pure lithium containing compounds
The invention generally relates to methods of selectively removing lithium from various liquids, methods of producing high purity lithium carbonate, methods of producing high purity lithium hydroxide, and methods of regenerating resin.
1. A method of producing highly pure lithium carbonate, the method comprising the steps of:
feeding a first aqueous solution comprising a purified lithium chloride stream to an electrolyzer equipped with a membrane or a separator, wherein the first aqueous solution has a lithium chloride concentration of up to 40% by weight to form a second aqueous solution comprising at least 10% by weight lithium chloride;
applying a current to the electrolyzer to produce a third aqueous solution in the cathode compartment that comprises greater than 4 wt % lithium hydroxide;
optionally cooling the third aqueous solution;
supplying the third aqueous solution and carbon dioxide to a carbonation reactor to produce a fourth aqueous solution comprising lithium bicarbonate;
separating the fourth aqueous solution from the carbon dioxide and lithium carbonate solids formed using a gas-liquid-solid reactor;
filtering the fourth aqueous solution to remove trace impurities; and
feeding the filtered fourth aqueous solution to a precipitation reactor maintained at a temperature of at least about 95° C. to precipitate highly pure lithium carbonate.
2. The method of claim 1 , further comprising supplying the fourth aqueous solution following the filtration step to an ion exchange column to remove divalent ions.
3. The method of claim 2 , wherein the ion exchange column comprises an ion exchange resin.
4. The method of claim 3 , wherein the ion exchange resin is comprised of a polystyrene matrix cross linked with divinyl benzene.
5. The method of claim 1 , wherein the membrane or separator operates to prevent migration of cations from migrating in the direction of the negative electrode.
6. The method of claim 1 , wherein the current is applied in a density of up to about 8,000 A/m 2 .
7. The method of claim 1 , wherein high purity lithium carbonate is defined as having a purity of at least 99.99%.
8. The method of claim 1 , wherein the recovered lithium carbonate is washed using a counter current wash.