VALORISATION OF SPENT ALKALINE AND ZINC-CARBON BATTERIES

This paper is focused on the recovery of zinc and manganese from alkaline and Zn-C spent batteries. Those metals were extracted by an acid leaching with sulphuric acid in presence of a reducing agent. A two-level full factorial design was planned to study the effect of three process factors: sulphuric acid concentration, lactose concentration an temperature. A simultaneously recovery of 98% of manganese and 100% of zinc was obtained after 3h of leaching by the following experimental conditions: sulphuric acid concentration 2 M, temperature 90°C, lactose concentration 9 g L-1 and 10% w/v pulp density. The main effects and interactions among them were assessed by the analysis of variance (ANOVA). The statistically significant main effects were correlated by empirical linear models to perform simulation studies valid in the tested range of experimental conditions. Precipitation tests were carried out to recover Zn and Mn from leach liquor by a selective precipitation with NaOH. The results showed that it is not possible to separate those metals in a single stage. A whole recycling process is also proposed to valorise all the materials alkaline and Zn-C spent batteries are made of, as provided by the new European Directive 2006/66/EC.