Thermodynamic assessment on the extraction of zinc from spent alkaline batteries-PVC waste streams

Abstract

Spent Alkaline Batteries (SAB) and Polyvinyl Chloride (PVC) are generated world-wide in large quantities with the absence of a sustainable recycling route. To study their potential co-recycling, we present a theoretical thermodynamic investigation of their co-thermal treatment utilizing the Gibbs free energy minimization approach. In the model, the possibility of recycling SAB and PVC by thermally treating their mixture followed by water leaching is reported. Results suggest that the thermal treatment of washed SAB (WSAB) with PVC at 300 ⁰C and under oxidative conditions promotes the selective chlorination of zinc over iron and manganese (leaving them in their respective oxide forms Fe₂O₃ and MnO₂). Simulations also revealed that performing water leaching of the thermally processed residue should be performed in the pH range 2–6 to dissolve zinc selectively while keeping both iron and manganese in their solid phase. Hence, to achieve high extraction selectivity towards zinc, SAB should first be water washed to dissolve sodium and potassium hydroxides. The product from water washing is then thermally treated with PVC (300 ⁰C with oxygen molar ratio above 1). The thermal treatment residue should then be water leached in the pH window 2–6.