Shifting the Burden of Selectivity from Chemical to Physical Separation Processes via Selective Sulfidation

Abstract

Increasing demand for critical metallic elements for sustainability applications motivates new approaches in primary and secondary production to handle falling ore grades and increasingly-convoluted recycling streams. Separation of elements in distinct phases is generally less energy intensive than separation of elements substituted in a single phase, a phenomenon referred to in primary extraction as the “mineralogical barrier”. Engineered materials leverage element substitution within single phase solutions to achieve target material performance. This results in large energy requirements during end of life recycling to selectively recover, via chemical separation, the target elements contained within a single phase. Herein, we present selective sulfidation as a novel, pyrometallurgical pretreatment to selectively partition target elements from a single phase into distinct, separate phases. We find such approach may support more competitive physical separation of difficult to isolate elements that previously required separation via complete hydrometallurgical dissolution and aqueous-organic liquid-liquid solvent extraction. We demonstrate selective sulfidation as applied to end-of-life magnet, battery, and copper slag recycling as a means to shift the burden of selective separation from chemical to physical processes.