(Invited) Thermodynamic and Electrochemistry of Metal Separation and Recovery Using Molten Sulfides

Abstract

A greater emphasis on processes with limited greenhouse gas emissions and water usage, along with electrification and a need to increase the recovery of valuable metals from mining and recycled sources, put chemical and electrolytic approaches at high temperature to the forefront. Herein, sulfides and molten sulfides are surveyed as possible candidates, starting with their unique standard-state electrochemical series. Evidences of the validity of electrochemistry in molten sulfides are then presented, highlighting key electrochemical engineering features that suggest high productivity and overall efficiency for elements such as copper or iron but also molybdenum, silver, zinc, nickel, or cobalt. A recent development to predict the conditions of simultaneous deposition of metallic elements, using non-standard states, is presented, supporting the importance of thermodynamic in the design and application of high temperature electrolytes for metal recovery.