Electrochemical evaluation of manganese reducers – Recovery of Mn from Zn–Mn and Zn–C battery waste

Extraction of manganese from ores or battery waste involves the use of reductive reagents for transformation of MnO2 to Mn2+ ions. There are many reducers, both organic and inorganic, described in the literature. A series of 18 reducers has been discussed in the paper and they were classified according to standard redox potential (pE = −log ae− where pE is used to express formal electron activity and ae- is formal electron activity). The experiments of manganese extraction from paramagnetic fraction of Zn–C and Zn–Mn battery waste in the laboratory scale have been described for 3 reducers of different origin. The best result was achieved with oxalic acid (75%, with the lowest redox potential) and urea (with typical redox potential) appeared inactive. Extraction supported by hydrogen peroxide resulted in moderate yield (50%). It shows that formal thermodynamic scale is only preliminary information useful for selection of possible reducers for manganese extraction resources. •The reduction reaction of MnO2 to Mn2+ was studied.•The analysis of oxidation-reduction potentials for specific reducers was carried out.•It was found that the best results of leaching were obtained by the use of oxalic acid as the reducer.