Efficient extraction and recovery of lithium from waste aluminum cryolite electrolyte

Abstract

The accumulation of alkali metals in cryolite electrolyte has negative impacts on the operation of aluminum electrolysis, and part of electrolytes need to be periodically replaced and discharged. A cleaner and efficient process was proposed to recover LiF and Al2(SO4)3 from the waste cryolite electrolyte. Under the optimum sulfated roasting conditions, 87.55% of Li and 30.30% of Al were leached. The obtained cryolite residue with a low molecular ratio could be returned to the aluminum electrolysis system. The addition of sodium benzoate achieved the efficient separation of Al3+ from Li-containing leachate, and the Al precipitation ratio was 99.78%. Acid leaching of the aluminum precipitate regenerated benzoic acid and recovered 99.62% of Al2(SO4)3. Finally high-purity cubic LiF was prepared from Li2SO4 solution, and the recovery of LiF was 98.78%.