A Citric Acid/Na2S2O3 System for the Efficient Leaching of Valuable Metals from Spent Lithium-Ion Batteries

Recycling of valuable metals from spent lithium-ion batteries (LIBs) appears inevitable for both environmental protection and resource recovery. In the present study, an efficient hydrometallurgical leaching of Co and Li from cathode materials of spent LIBs using a citric acid/sodium thiosulfate (Na 2 S 2 O 3 ) system is explored. The effects of citric acid and Na 2 S 2 O 3 concentrations, leaching time, temperature, and the solid/liquid ( S / L ) ratio on the leaching processes are also examined. With the exception of the S / L ratio, the increase of citric acid concentration, Na 2 S 2 O 3 concentration, leaching time, and temperature all have positive effects on the leaching of Co and Li. Ultimately, approximately 96% of Co and 99% of Li are recycled from the spent LIBs in this citric acid/sodium thiosulfate system under the leaching conditions of an S / L ratio of 20 g l −1 , concentration of Na 2 S 2 O 3 of 0.3 M, concentration of citric acid of 1.2 M, leaching time of 30 min, and leaching temperature of 70°C. The Avrami equation is well fitted by the data of the leaching processes, and model equations are built to describe the leaching of Co and Li. Furthermore, pure sulfur can be obtained as a by-product during the leaching process, and SO 2 produced during the reaction is easily collected as a raw material for industrial production of sulfuric acid. The present study represents a promising process for hydrometallurgical recovery of valuable metals from spent LIBs.