Beneficiation of Zimbabwean petalite : extraction, purification and compound synthesis

Abstract

Lithium is one of the most strategically important minerals at the time of writing. The demand for lithium and lithium compounds to be used in lithium-ion batteries is increasing day by day. Zimbabwe possesses a considerable resource of lithium ore, estimated at 23 000 mt Li. Beneficiation of this lithium ore could indeed be a very promising business in the near future. This work focuses on processing of petalite concentrate from the Bikita deposit in Zimbabwe for production of Li2CO3, with subsequent preparation of LiF and LiCl. Analysis performed on the petalite showed that the average Li2O content is 4.10 %. The extraction method used involves roasting the pre-heated concentrate with concentrated H2SO4 followed by water leaching of the resulting Li2SO4, solution purification and precipitation of Li2CO3 with subsequent preparation of LiF and LiCl. Investigation of the roasting and leaching showed that the dissolution rates are significantly influenced by roasting temperature and stirring speed. 97.3 % optimum rate of extraction was attained at 320 rpm and roasting temperature of 300 C. Water-washed lithium carbonate with a purity of 99.21 %( metal basis) and an average particle size of 1.4 ìm was produced. Good quality LiF and LiCl can be produced with purity of 99.36 % and 99.02 % respectively. The pH, concentration and agitation have a great influence on the morphology of the precipitated LiF. Lower pH values and optimum concentration of the Li2CO3 solution results in smaller particle size. High recovery of 96.53 % LiF was realised. Anhydrous LiCl was found to absorb moisture when exposed to air at ambient temperature. The synthesised LiCl melts at 606.2 C with a corresponding enthalpy of fusion of 18.4 kJ mol-1, close to the values reported in the literature. Copyright