Integrated process for lithium recovery from zinnwaldite

Process development for production of lithium carbonate (Li2CO3) from regionally occurring zinnwaldite concentrate (3.0 wt.-% Li2O) was conducted. By acid digestion with mineral acids, preferably hydrochloric acid under reflux (approx. 110 °C) and atmospheric pressure, lithium is mobilised up to 94%. In contrast to using sulphuric acid no toxic hydrogen fluoride is released with hydrochloric acid, what is a crucial factor for digestion process design. Separation technologies for recycling of more than 80% of unspent hydrochloric acid, as well as the recovery of associated components, particularly iron hydroxide and potassium/aluminium/fluoride as sodium-potassium-cryolite, are part of the process. After removal of impurities by means of electrodialysis and concentration, technical grade lithium carbonate was obtained by precipitation with soda. Hot water washing furnishes crude-product purities ≥ 98.0% with a total lithium yield of ~ 70%.