Solvent extraction and separation of Cd(II), Ni(II) and Co(II) from chloride leach liquors of spent Ni-Cd batteries using commercial organo-phosphorus extractants

Development of a flow sheet for the solvent extraction, separation and recovery of cadmium(II), cobalt(II) and nickel(II) from chloride leach liquors of spent Ni-Cd batteries by hydrometallurgical route was investigated. Cyanex 923 showed selective separation of cadmium(II) from nickel(II) and cobalt(II). Two-stage counter-current extraction at 1:1 phase ratio and three stages of stripping with distilled water at an aqueous to organic (A:O) phase ratio of 1.75:1 gave > 99.9% Cd extraction and stripping efficiency. Studies on the separation of cobalt from nickel from the cadmium raffinate indicated Cyanex 272 as the best extractant with a separation factor > 4700. Cobalt(II) extraction efficiency of ∼ 99.9% was achieved with 0.03 M Cyanex 272 in three counter-current stages at an A:O ratio of 1.5:1. Complete stripping of metal from the loaded organic containing 0.33 g/L Co was carried out at pH 1.5 in 2 stages at an O:A ratio of 2:1. The enrichment of cobalt was about 4.7 times. More than 99% Ni recovery was achieved with 1 M TOPS 99 as the extractant from the cobalt raffinate. A complete flow sheet of the process for the separation and recovery of Cd(II), Co(II) and Ni(II) as chlorides was demonstrated.