Recovery of Ni-based alloys from spent NiMH batteries

Abstract

Although spent nickel metal-hydride (NiMH) batteries are not considered hazardous waste, there are valuable materials that could be recovered; therefore the recycling of these batteries should be considered. This paper discusses spent NiMH batteries characterization and describes a simple process to recover valuable materials based on mineral processing techniques, hence the specific objective of this work is to study a process for the recovery of valuable metals from spent NiMH batteries. Batteries were manually dismantled in order to classify their components. The electrodes could be separated during the manual dismantling and were characterized through X-ray diffraction (XRD) analysis. A significant fraction of the batteries, around 37 wt.%, is composed of Ni-based alloy. The spent batteries were treated using laboratory equipment. The treatment that produced the best results was hammer milling, magnetic separation, knife milling, magnetic separation and size separation. The overall metal yield was in the order of 86%. A preliminary economic study is presented to show the feasibility of the process.