Application of mechanical processing operations for the recycling of nickel metal hydride batteries

Rapid technological development in recent decades has led to very high generation of waste electrical and electronic equipment, including exhausted nickel metal hydride batteries. Therefore, efficient and environmentally friendly recycling techniques are required for the recovery of the valuable materials of this type of waste. The aim of the present work was to develop an alternative process for recovery of the different materials present in these batteries, by means of mechanical processing with additional steps of size separation than the usual in the literature. Firstly, the batteries were manually disassembled, and the different components were separated and weighed. The components were then characterized by XRD, XRF, DSC and SEM–EDS analyses. After the characterization, mechanical processing was performed, involving the following steps: comminution in a hammer mill, oven-drying to eliminate the electrolytes, size separation by sieving, magnetic separation and two additional steps of size separation by sieving. The proposed process was shown to be highly efficient, achieving recovery efficiencies in the range of 86.54–91.25 wt.% for the different outputs obtained, with high degree of calculated purity attained as well (96.64–100.00 wt.%).