Extraction of Rare Earth Elements (REE) from End-of-Life NiMH Battery Electrode Powders Using Deep Eutectic Solvent (DES)

Rare Earth Elements (REEs) are critical raw materials essential for energy and digital transitions. In this study, original data are presented on the extraction of REEs from electrode powders of NiMH batteries pre-treated through physical methods in a cryo-mechanical pilot plant. The electrode powder was characterized for its chemical composition and subsequently subjected to extraction using a DES based on choline chloride and lactic acid (with a molar ratio of 1:2). The performance of DES extraction was compared with leaching using sulfuric acid under varying temperatures. Empirical modeling of extraction with sulfuric acid revealed a significant negative effect of increasing temperature on the extraction of both Lanthanum and Cerium, which consequently reduced REE selectivity. Kinetic tests using DES showed a positive effect of time on REE extraction, while other metals (such as Nickel and Manganese) exhibited a non-monotonic effect of time, ultimately enhancing REE selectivity at longer durations.