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

Abstract

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.