| Abstract: | Nickel–metal hydride batteries contain valuable metallic components and although they are not considered a hazardous waste, recovery of these materials is necessary from an economic point of view. In this work a hydrometallurgical method for the dissolution and separation of the metals from cylindrical nickel–metal hydride rechargeable batteries was investigated. Hydrochloric acid was employed as the leaching agent to dissolve the metals from the batteries. Dissolution of metals was investigated as a function of acid concentration, leaching time and temperature. Suitable conditions for maximum metal dissolution were 3 h leaching with 4.0 mol dm?3 hydrochloric acid solutions at 95 °C. Extraction of 98% of nickel, 100% of cobalt and 99% of rare earth elements was achieved under these conditions. Separation of the rare earths from nickel and cobalt was preliminarily investigated by single batch solvent extraction with 25% bis(2‐ethylhexyl)phosphoric acid. Efficient separation via complete extraction of the rare earths was obtained at a pH of approximately 2.5 while leaving nickel and cobalt in the raffinate. A shrinking particle model which can enable, under certain conditions, evaluation of the extent of metal dissolution present in nickel–metal hydride batteries was developed. A proposed electrochemical recovery of nickel and cobalt is also briefly discussed. Copyright © 2004 Society of Chemical Industry |
