Solubility and Modeling of Li2SO4•H2O in Aqueous H2SO4-MgSO4 Solutions for Lithium Extraction from Spodumene

Lithium extraction from spodumene (LiAlSi2O6) is of great importance to meet the increasing demand for lithium-ion batteries used in electric energy storage. However, conventional processing of spodumene involves enormous consumption of H2SO4 during the neutralization step. We propose a new flowsheet to avoid wasting H2SO4 by adding a cooling crystallization step to crystallize lithium sulfate as Li2SO4 center dot H2O. To advance the process development, the solubilities of Li2SO4 center dot H2O in the system H2SO4-MgSO4-H2O from 283.15 to 353.15 K were measured experimentally via a dynamic method. Chemical modeling for the solubility was carried out by regressing the mixed solvent electrolyte model parameters with the average absolute relative deviation of less than 2%. The newly built model is capable of calculating the solubility of Li2SO4 center dot H2O in aqueous H 2 SO 4 -MgSO 4 solutions in wide concentration and temperature ranges. Cooling crystallization of Li2SO4 center dot H2O in concentrated H2SO4 was conducted and its feasibility was proved.