Development of a combined pyro- and hydro-metallurgical route to treat spent zinc-carbon batteries.

The potential of solvent extraction using Cynanex272 for the recovery of zinc from spent zinc carbon batteries after a prior leaching in hydrochloric acid has been investigated. The elemental analysis of the spent material was carried out by ICP-MS. The major metallic elements are: ZnO (41.30%), Fe(2)O(3) (4.38%), MnO(2) (2.69%), Al(2)O(3) (1.01%), CaO (0.36%) and PbO (0.11%). The quantitative leaching by hydrochloric acid showed that the dissolution rates are significantly influenced by temperature and concentration of the acid solutions. The experimental data for the dissolution rates have been analyzed and were found to follow the shrinking core model for mixed control reaction with surface chemical reaction as the rate-determining step. About 90.3% dissolution was achieved with 4M HCl solution at 80 degrees C with 0.050-0.063 mm particle size within 120 min at 360 rpm. Activation energy value of 22.78 kJ/mol and a reaction order of 0.74 with respect to H(+) ion concentration were obtained for the dissolution process. An extraction yield of 94.23% zinc by 0.032M Cyanex272 in kerosene was obtained from initial 10 g/L spent battery leach liquor at 25+/-2 degrees C and at optimal stirring time of 25 min. Iron has been effectively separated by precipitation prior to extraction using ammoniacal solution at pH 3.5, while lead and other trace elements were firstly separated from Zn and Fe by cementation prior to iron removal and zinc extraction. Finally, the stripping study showed that 0.1M HCl led to the stripping of about 95% of zinc from the organic phase.