Recycling Spent Primary Cells for the Synthesis of Spinel ZnMn2O4 using Waste Polypropylene as Reductant in a Microwave Oven

Abstract

This work investigates the recycling of spent primary cells for the synthesis of spinel zinc manganese oxide (ZnMn₂O₄) using waste polypropylene as reductant in a domestic microwave oven. Spent zinc-carbon batteries (TigerHead brand) were cut into approximately two equal parts and the MnO₂/Mn₂O₃/ZnO/carbon black mixture was carefully removed. The residual casing was dismantled and scrap iron, plastic and paper separated. The removed mixture was soaked in water for 24 hours after which it was filtered and the residue air-dried for 24 hours and pulverised in a mortar using a pestle. The pulverised mass was thoroughly mixed with pulverised polypropylene obtained from a mixture of waste bucket and the cap of the zinc-carbon battery. The mixture was then placed in a fireclay crucible and irradiated in a domestic microwave oven (Pioneer, Model PM-25 L, 2450 MHz, 1000 W) for 20 minutes and reaction products were separated and characterised. Spherical particles of spinel zinc manganese oxide (ZnMn₂O₄) were isolated after crushing the reduced mass. Analysis (XRD) of the residual reduced mass showed that it consisted of several peaks of ZnMn₂O₄ along with peaks of SiO₂ and uncombined ZnO and Mn₃O₄.

Keywords: Spinel ZnMn₂O₄, Primary cells, Zinc-carbon battery, Polypropylene, Microwave oven