Hydrometallurgical processing of spent zinc-manganese batteries

Abstract

This paper explores the possibility of zinc-manganese battery recycling in alkaline solutions. It was shown that three-stage washing could remove potassium chlorides from active mass of milled batteries. Influence pattern regularities were established for some parameters (temperature, alkali concentration and number of cycles) of alkaline leaching of a zinc-carbon and alkaline battery mixture in respect of zinc extraction into the solution. The reason of low zinc extraction from this material was found to be the presence of zinc and manganese compounds as heterolite and hydroheterolite that are difficult to dissolve in alkalis. It was found that zinc extraction increases by 2.6 times with an increase in the NaOH concentration from 100 to 205 g/dm 3 , but further increase in the NaOH concentration, as well as an increase in temperature in the range of 30–85 °C, does not affect zinc extraction into the solution. Optimal process parameters of zinc-carbon and alkaline battery leaching at 30 min leaching time and 200 g/dm 3 pulp density were determined as follows: temperature is 30 °C, NaOH concentration is 390 g/dm 3 . Experiments on zinc ion accumulation with repeated filtrate leaching showed that increasing the initial NaOH concentration to 390 g/dm 3 makes it possible to transfer the maximum possible amount of zinc into the solution at the same NaOH consumption due to the cyclic treatment of solutions. Zinc and NaOH concentrations in solutions after leaching reached 59 g/dm 3 and 300 g/dm 3 , respectively. Solutions obtained could be sent to zinc electrowinning and then returned to leaching again.