Recovery of valuable metals from spent lithium ion batteries by solvent extraction

摘要

Cobalt is recovered from square type of spent lithium ion batteries (LIBs) containing 5-20 % Co, 5-7 % Li, 5-10 % Ni, 15% organic chemicals, and 7% plastics together with Cu, Al, Fe, and Mn. The waste LIB was prepared by physical treatment. After screening, the crushed LIBs were separated to +8 mesh, -8/+16 mesh, and -16 mesh powder. Among these, -16 mesh powder was selected for leaching. The leaching test was investigated at 2 M H2SO4, 6 vol.% H_2O_2, reaction temperature 60 °C, agitation speed 300 rpm, solid/liquid ratio 50 g/ 500 ml, reaction time 1 h. The leaching efficiency of cobalt was more than 99 % and its concentration was 24.9 g/L. For removing of impurities such as copper, iron, and aluminum in the leaching solution before cobalt solvent extraction, the impurities were eliminated by pH control with alkali solution. For selective extraction of cobalt, the aqueous phase removed impurities was equilibrated with different volumes of 0.4 M Cyanex 272 saponified of 50 %. Extraction efficiency of cobalt was about 80 % at first step. Separation coefficient (ssCoLi) of cobalt and lithium extractions was 206.5. Over 9.0 % of pure cobalt sulfate solution was obtained after stripping with H_2SO_4 solution.