Selective separation and recovery of cobalt from leach liquor of discarded Li-ion batteries using thiophosphinic extractant

Abstract

Plenty of valuable metals especially cobalt is present in spent batteries. The conventional process of disposing the spent batteries as land fill or metal recovery through pyrometallurgical process was not sustainable step to resolve problems. Present work is a part of systematic study involving solvent extraction for the separation and recovery of cobalt from leach liquor of spent batteries containing 21.83 g/L, 2.77 g/ L, 9.14 g/L and 4.14 g/L of cobalt, lithium, copper and aluminum, respectively. Initially bench scale studies were carried out using synthetic solution of 10.44 g/L cobalt and 1.33 g/L lithium (composition similar to the leach liquor diluted two times) in sulfate medium to optimize the condition for the metal recovery from the leach liquor of available batteries. 15% Cyanex 272 as extractant, 3% isodecanol as phase modifier and kerosene as diluent extracted about 99.9% cobalt from synthetic solution at equilibrium pH 5, O/A ratio 1:1 within 5 min of contact time in two stages. The metal loaded organic was scrubbed with 10% Na2CO3 and stripped with 10% H2SO4. The optimized condition obtained was compared with the leach liquor of batteries which shows the presence of about 99.99% cobalt in the stripped solution and about 95% Li in the raffinate. Hydrated salt of cobalt can be further obtained by using evaporation, Crystallization,precipitation and cementation process.