A New Solvent Extraction Design for the Recovery of Valuable and Environmentally Important Metals from Spent Rechargeable Ni-Cd Batteries

The Ni-Cd batteries content hazardous metals Ni, Cd and Co suspected carcinogenic [1]. The demands for metals is increasing, while primary sources are being decreased. This motivates the research on the recycling of the end-of-life products, which is important from both economic and environmental aspects [2]. The present communication describes a new procedure for the recovery of Ni, Cd and Co from the spent Ni-Cd batteries. A series of batteries were cleaved and the solid materials were collected for leaching the metal contents. The leaching process was optimized with respect to the influencing parameters. A multi-step solvent extraction procedure performed by contacting a given volume of the leached solution with an organic phase (tri-n-octylamine, TOA in dichloromethane, DCM) allowed to extract quantitatively Cd and Co contents into the organic phase. A selective back-extraction of Cd and Co using NH3 solution allowed separating these metals. The RSM optimization method reveled that an efficient leaching of Cd, Ni and Co from the solid materials can be achieved by leaching 4.5 g of the materials with 100 mL of HCl (2.7 M) after 200 min, at 47.3 °C. The solid materials contain 30.5, 27.2 and 2 wt% of Cd, Ni, and Co, respectively. An aliquot of 15 mL of the leached solution (202.5, 187.6 and 13.5 of Cd, Ni, and Co) was contacted, in four steps, with 15 mL of the organic phase (0.5 M TOA in DCM). The total transferred Cd and Co into the organic phase was 187.5 and 3.95 mg (92.5 and 29.3% of the initial amounts), respectively. The cadmium contents in the organic phase was totally back-extracted by using a 0.5 M NH3 solution. Under such condition, the extracted Co remained in the organic phase. In order to the separation of Ni and Co the remained in the source solution, the extraction of this aqueous phase was continued in a further five steps extraction procedure with the same organic solutions. The total extracted cobalt into the organic solutions was raised to 11.48 mg (85% of its initial amount). The back-extraction of Co was succeeded by using a 7 M of NH3 solution.