Processes for treating aqueous compositions comprising lithium sulfate and sulfuric acid

A process for treating an aqueous composition comprising lithium sulfate and sulfuric acid, said process comprising:

• evaporatively crystallizing the aqueous composition comprising lithium sulfate and sulfuric acid under conditions to obtain crystals of lithium sulfate monohydrate and a lithium sulfate-reduced solution;
• optionally separating the crystals of the lithium sulfate monohydrate from the lithium sulfate-reduced solution;
• and
• wherein the evaporative crystallization is carried out using a vapour recompression evaporator in which vapour from one effect is used to evaporate further vapour in either a different effect, or in the same effect by either operating an additional effect at a different pressure, or compressing the vapour and recondensing in a steam chest in the same effect.