One-step separation and recovery of copper and sulfur by electrolysis in deep eutectic solvents

Abstract

Cuprous sulfide constitutes the primary component of copper concentrate and matte. Due to copper's sulfur-affinity characteristics, achieving one-step separation and recovery of copper and sulfur has always posed a challenge in copper metallurgy. Deep eutectic solvents (DESs) have emerged as environmentally friendly electrolytes for the separation and recycling of metals and their compounds. This study demonstrates the feasibility of dissolving Cu₂S, reducing it to copper (Cu), and oxidizing it to sulfur (S) through electrolysis in Reline DES. Optimised electrolysis conditions of 1.2 V, 80 °C, and 6 hours result in the deposition of pure nano-sized copper particles, ranging from 100–200 nm, and the production of sulfur particles with an average size of around 5 μm. The crystalline structure of the anode product is identified as S₁₂ and S₆. When Cu₂S is introduced into Reline, it dissolves [CuCl₂]⁻ without disrupting the structure of the choline ion (Ch⁺). Furthermore, a kinetic study reveals that higher temperatures promote the redox processes of [CuCl₂]⁻ Cu and S²⁻ to S, enhancing the overall reaction rates. Additionally, the diffusion coefficient (D) of [CuCl₂]⁻ increases with rising temperatures.