Vacuum thermal reduction of used alkaline Zn–Mn batteries to recover Zn and prepare Al–Mn alloys

Alkaline zinc–manganese batteries are the most used disposable batteries in the world and cannot be recharged. Spent alkaline zinc–manganese batteries are mainly disposed of in landfills, and the resulting enrichment of the soil with potassium(K), zinc(Zn), and manganese(Mn) pollutes the groundwater and wastes valuable resources. Herein, a process for the treatment of used alkaline zinc(Zn)–manganese(Mn) batteries that involved water leaching, calcination, and vacuum aluminothermic reduction was developed. Investigation of the elemental migration process and reaction mechanism showed that the purity of potassium carbonate(K 2 CO 3 ) reached 99 % with 92.1 % recovery at a water leaching temperature of 60 °C and time of 25 min. The leaching slag was calcined at 700 °C for 1 h to obtain calcined slag with zinc oxide (ZnO), manganese(III) oxide (Mn 2 O 3 ), and manganese(II) oxide (MnO) as the main phases. When the calcined slag was reduced with aluminum powder, the recovery rate of Zn reached 99.7 % at a reduction temperature of 1100 °C, reduction time of 2 h, and ratio of aluminum powder to calcined slag of 1.5:1. Under these conditions, Mn was recovered in the form of Al 6 Mn alloy, and the main phase of the remaining reduced slag was alumina. In this study, potassium and metallic zinc were separated and recovered, and at the same time, an aluminum(Al)–manganese(Mn) alloy was prepared. The developed environmentally friendly and emission-free process enables the efficient recycling of the valuable resources K, Zn, and Mn, resulting in cleaner battery disposal.