Aqueous Electrochemical Processing Of Rare Earth Elements: A Review

Abstract

This chapter is a comprehensive review of various technologies and methods related to the separation and extraction of rare earth elements (REEs) at low temperatures (<100 °C). Addressed are various topics such as redox-based processing, liquid-metal cathode (LMC) studies, and electrochemistry-driven REE magnet dissolution and recovery. The chapter begins with an introduction to REEs, their importance in technology, and the need for a more sustainable process for REE separation and capture. The second section addresses the redox-based processing techniques for Ce and Eu separation and details the Eu and Ce anomaly which allows them to be extracted from aqueous REEs unlike the other REEs. The third section focuses on LMC studies using mercury (Hg) where REEs were extracted through electrolytic reduction or galvanic displacement. This section includes early work done prior to 1950, at Los Alamos National Laboratory, and in the former Soviet Union. The section also summarizes possible replacements for Hg. The thermodynamics for amalgam formation are also discussed. The fourth section covers electrochemistry-driven REE magnet dissolution and recovery. This section discusses dissolution of REE magnets to separate elements such as iron followed by REE precipitation. The final section provides perspective discussing the challenges and future directions in this field.