Solvent mediated interactions for the selective recovery of Cadmium from Ni-Cd battery waste

This work deals with the development of a solvent extraction process for the selective separation of cadmium, from cobalt and nickel, using DEHPA as an extractant. After mechanical separation, dissolution of the electrode material in H2SO4 and iron removal the leach liquor obtained was subjected to solvent extraction for the extraction and separation of all the three metal ions. The conditions were optimized for the selective recovery of Cd using 20% D2EHPA with 60% saponification. Saturated loading capacity for 20% (60% saponified D2EHPA) was found to be 10.89 g L-1 Cd, 1.404 g L-1 Ni, and 0.032 g L-1 Co at O/A ratio of 1:1. McCabe-Thiele plot at varying O/A ratio indicated the requirement of 4 stages for 100% extraction of Cd at O/A ratio of 1:1.5. The dependence of extraction on pH indicated that the extraction of Cd(II) proceeds according to a cation-exchange reaction at lower acidity and to a solvating reaction at higher acidities. The co-extracted Ni and Co were effectively scrubbed with 50 g L-1 CdSO4 at pH 0.5.99.6% Cd was stripped from the loaded D2EHPA with 75 g L-1 of H2SO4. Based on the slope analysis of the plots of log D-Cd versus log [(HR)2] and pH vs log D-Cd. Cd was found to be extracted as CdR2.(HR)(2). The process seems to be promising for the production of pure metal streams which can further be used to produce valuable commercial products vis-a-vis the environmental protection. (C) 2012 Elsevier B.V. All rights reserved.