Thermal pretreatment of spent button cell batteries (BCBs) for efficient bioleaching

Spent Zn-Mn button cells are one of the fastest-growing battery waste streams containing considerable amounts of Zn (12–28% (w/w)) and Mn (26–45% (w/w)) that could be considered as a potential industrially demanded source of Mn and Zn. However, due to the very toxic, stable, and refractory nature of the button cell batteries, applying microbial leaching for metal extraction from spent batteries is limited. In this regard, this study focused on detoxicate, enriching, and mobilizing major elements through thermal treatment assisted by acidic bioleaching. It was witnessed after thermal pretreatment of BCBs powder at 600 °C, the A. ferrooxidans could tolerate up to 20 g/L BCBs containing a high concentration of Mn and Zn by serial step-wise adaptation process. The use of thermal pretreatment increased by 76% and 75% extraction yields of Mn and Zn compared with the results obtained using un-thermally pretreated BCBs powder. The result indicated that 95% of zinc and 91% manganese were efficiently extracted from thermally pretreated BCBs. A. ferrooxidans and Fe ³⁺ play an important role to improve Mn and Zn extraction efficiency. The structural and morphological analyses showed that the proposed approach could successfully overcome spent button cell batteries complexities and extract most of the major metals.