Lithium carbonate recovery process
A process for the recovery of lithium carbonate from a solution ( 1 ) containing a mixture of lithium sulfate and lithium hydroxide, the process comprising the precipitation of lithium carbonate ( 3 ) from the solution ( 1 ) containing a mixture of lithium sulfate and lithium hydroxide through the addition of carbon dioxide ( 2 ).
1 . A process for the recovery of lithium carbonate from a solution containing a mixture of lithium sulfate and lithium hydroxide, the process comprising the steps of:
a) Precipitation of lithium carbonate from a solution containing lithium sulfate and lithium hydroxide through the addition of carbon dioxide;
b) Solid liquid separation and optionally washing of the precipitated lithium carbonate to recover a liquor containing lithium sulfate;
c) Recycle of the liquor to a subsequent step to convert lithium sulfate to lithium hydroxide;
d) Purification of the lithium carbonate by pulping in water and addition of carbon dioxide to produce lithium bicarbonate solution;
e) Solid liquid separation of the lithium bicarbonate solution to remove insoluble impurities;
f) Heating the lithium bicarbonate solution to strip carbon dioxide and re-precipitate lithium carbonate; and
g) Solid liquid separation, drying and packing of the purified lithium carbonate product.
2 . The process of claim 1 , wherein the lithium carbonate precipitation step a) is operated at atmospheric pressure.
3 . The process of claim 1 , wherein the lithium carbonate precipitation step a) is operated in a temperature range of:
a. between ambient to about 100° C.;
b. greater than about 50° C.; or
c. between about 50° C. to 100° C.
4 . The process of claim 1 , wherein the lithium carbonate precipitation step a) occurs over a residence time of about 2 hours.
5 . The process of claim 1 , wherein the lithium carbonate precipitation step a) achieves a precipitation extent of about 90% of the stoichiometric mass of lithium hydroxide contained in the solution containing both lithium sulfate and lithium hydroxide.
6 . The process of claim 1 , wherein the lithium carbonate precipitation step a) comprises the addition of in excess of stoichiometric carbon dioxide addition.