Leaching Mechanism\nfor Chalcopyrite in Electrochemically\nRegenerated Vanadium(II)

Vanadium(II) sulfate was utilized as an electrochemical\nreagent\nto reductively leach and convert chalcopyrite into less refractory\nmineral phases for subsequent copper extraction. During leaching,\niron was selectively extracted into the solution. Fast leaching kinetics\nunder various pulp densities and temperatures were observed, with\n∼90% iron being leached within 60 min under all conditions\ntested. The phase composition and particle morphology of the solid\nproduct were analyzed by using X-ray diffraction (XRD), automated\nmineral identification characterization systems (AMICS), and scanning\nelectron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS).\nThe results showed that djurleite (Cu<sub>1.94</sub>S) emerged as\nthe predominant product after V<sup>2+</sup> leaching. The conversion\nof chalcopyrite to djurleite was accompanied by a significant morphological\ntransformation from ∼30 μm mineral particles to ∼200\nnm nanoparticles. To provide insight into the phase conversion, the\ninitial stage of the reaction between chalcopyrite and V<sup>2+</sup> solution was examined, revealing crack formation within the inner\nparticle and nucleation of the product phase at the leached particle\nsurface. Along the cracks and at the particle surface, chalcopyrite\nwas replaced by an iron-depleted and copper-rich phase. In an unstirred\nsystem, the leached particles were found to preserve the original\nexternal shape while attaining a highly porous structure. Based on\nthe texture observations, a dissolution–precipitation mechanism\nwas proposed. And the precipitation chemistry was hypothesized to\nbe a reaction between hydrogen sulfide and dissolved copper intermediate.\nIn addition, copper metal was successfully obtained as the primary\nproduct of V<sup>2+</sup> leaching when a sufficient reactant was\npresent.