A totally hydrometallurgical process for the recovery of nickel, cobalt and rare earths from spent nickel-metal hydride secondary batteries has been developed. In this process, the electrode materials are mechanically separated from the external case and leached with hydrochloric acid. The resulting leach liquor typically contained, in grams per liter, 23.4 Ni, 1.7 Co, 3.4 Fe, 0.72 Zn, 0.46 Al, 1.2 Mn, 4.2 La, 0.26 Ce, 0.82 Pr, 2.6 Nd and 0.074 Sm, as well as 50 Cl~-.The pH of the solution was around 1.2. The rare earth values are recovered from the leach liquor by use of a solvent extraction circuit with 25 percent D2EHPA in kerosene, followed by precipitation with oxalic acid. A mixed rare earth oxide of over 99 percent purity was obtained after calcination of the precipitate. The total yield of rare earths approached 98 percent. The cobalt and nickel in the raffinate are effectively separated by selective extraction of cobalt with 25 percent TOA in kerosene after concentration of the solution (up to [Cl~-] approx= 220 gL~(-1)). Subsequently the individual cobalt and nickel are recovered as oxalates by addition of ammonium oxalate. Highly pure cobalt oxalate and nickel oxalate with a purity close to 99.9 percent were obtained. The overall recoveries of cobalt and nickel were found to be approximately 98 percent and 96 percent, respectively.
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