Enhanced Leaching of Mn from Electrolytic Manganese Anode Slime via an Electric Field

Electrolytic manganese anode slime (EMAS) contains many Mn resources, and efficient Mn leaching is the key to realizing its high-value utilization. In this study, the effects of Fe2+ concentration, H2SO4 concentration, liquid–solid mass ratio, reaction temperature, and current density on Mn leaching efficiency were investigated. The enhanced leaching kinetics and mechanism of Mn from EMAS were analyzed. The results showed that the leaching efficiency of Mn in EMAS was 97.5%, the Pb content in the leaching residue was 42.24 wt % at a current density of 120 mA/cm2, the concentration of Fe2+ was 0.7 mol/L, the concentration of H2SO4 was 1.6 mol/L, the mass ratio of liquid–solid was 6 mL/g, and the reaction time and temperature were 150 min and 333 K. The leaching mechanism showed that the closed-cycle system of Fe2+–Fe3+–Fe2+ was formed in the process of electric field leaching, and Fe2+ and Fe3+ became the electron transport media, which realized the oxidation–reduction leaching of MnO2 and Fe2+ in EMAS. Leaching kinetics indicated that the apparent activation energy is 38.38 kJ/mol and the apparent efficiency equation is 1–2/3X – (1 – X)2/3 = A exp(−38.38/RT)t. This study provides a new method for resource utilization of EMAS.