Selective Recovery of Zn and Mn from Waste Zinc–Manganese Batteries by Autocatalytic Reduction Roasting Followed by Leaching Process

Waste Zn-Mn batteries were the largest producer of e-waste, which was not only typical hazardous materials but also the high-grade secondary resource of Zn and Mn. Existing hydrometallurgy methods mainly used acids to leach the waste batteries, and then purified the products by precipitating, extracting, etc. However, Mn-Zn spinel was easily formed in spent batteries, which were stubborn and only dissolved in strong acid systems. In this study, a novel process for selective recovery of Zn and Mn from waste batteries by reduction roasting followed by an acid leaching process was developed, of which spent graphite electrodes were used as reducing agents. The effect of roasting and leaching parameters was studied, and the recovery efficiency of Zn and Mn was about 98.5% and 99.5%, respectively. In addition, the phase transformation of Mn-Zn spinel was declared by thermomechanical analysis, XRD, ICP, etc.