Hydrometallurgical Processing of Spent Zinc-Manganese Batteries

In this paper, the possibility of processing zinc-manganese batteries in alkaline solutions is studied. It is shown that three-stage washing can remove potassium chloride from the active mass of milled batteries. The regularities of influence of some parameters (temperature, amount of alkali and number of cycles) on the extraction of zinc into solution during alkaline leaching of a mixture of salt and alkaline batteries are established. The reason for the low extraction of zinc from this material is the presence of zinc and manganese compounds as heterolite and hydroheterolite that are difficult to dissolve in alkalis. It is found that, with an increase in the concentration of NaOH from 100 to 205 g/dm³, zinc extraction increases by 2.6 times, but a further increase in the concentration of NaOH, as well as an increase in temperature in the range of 30–85°C, does not affect the zinc extraction into solution. The optimal process parameters of leaching of salt and alkaline batteries at duration of 30 min and pulp density of 200 g/dm³ are determined as follows: temperature of 30°C, NaOH concentration of 390 g/dm³. Conducting experiments on the accumulation of zinc ions with repeated filtrate coursing for leaching shows that, upon increasing the concentration of alkali to 390 g/dm³, owing to cyclic treatment of solutions, it is possible to transfer the maximum possible amount of zinc into the solution without increasing the NaOH consumption. The zinc concentration in solutions after leaching was equal to 59 g/dm³, and the NaOH concentration was 300 g/dm³. The obtained solutions can be directed to zinc electrowinning and after that be returned for leaching.