(677i) Leaching Mechanism for Chalcopyrite in Electrochemically Regenerated Vanadium(II)

Copper demand is growing globally due to the ongoing energy transition, making it imperative to develop alternatives to conventional smelting for sustainable copper production. This work introduces an innovative hydrometallurgical route for extracting copper from chalcopyrite utilizing vanadium (II) sulfate as a reductive lixiviant, with the V²⁺ reagent being regenerated through an electrochemical cell. The leaching kinetics of chalcopyrite in V²⁺ were characterized, demonstrating a fast leaching rate under ambient conditions, with ~90% iron being extracted within 60 minutes under all conditions tested. The solid product was reacted in ferric to demonstrate a copper recovery of ~80 %. The phase composition and particle morphology of the leached product were analyzed using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that the chalcopyrite mineral particles (~30 µm) were transformed into nanoparticles (~200 nm) identified as djurleite (Cu_1.94S). To provide insight into the conversion from chalcopyrite to djurleite, V²⁺ leaching was studied in an unstirred system, showing that the leached particles preserved the original external shape while attaining a highly porous structure. Accordingly, a dissolution-precipitation mechanism was proposed, and the precipitation chemistry is hypothesized to be a reaction between hydrogen sulfide and dissolved copper intermediate. In addition, copper metal was successfully obtained as the primary product of V²⁺ leaching when sufficient reactant was present. Consequently, a complete copper recovery was achieved upon the subsequent ferric leaching. The current findings on the leaching kinetics and the reaction mechanism can inform the optimization of industrial leaching process to improve the copper recovery, contributing to cleaner and more sustainable copper production.