Electrochemical insights into chalcopyrite leaching: Applying semiconductor theory for enhanced recovery

Abstract

The need for copper is driving innovation in hydrometallurgy, particularly as high-grade resources become scarcer. It emphasizes the importance of environmentally friendly and cost-effective ore processing solutions compared to pyrometallurgy. However, chalcopyrite’s remarkable resistance to leaching and its complex dissolution mechanisms present challenges. This study focused on the leaching of concentrated chalcopyrite at varying initial Fe(II) ion concentrations and pulp densities at 30 °C. Evaluation of copper extraction efficiency under optimum conditions (initial Fe(II) concentration of 398 mmol L-1 and a pulp density of 5 %) yielded an extraction rate of approximately 71 ± 3 % over 160 days. Various chalcopyrite dissolution reactions were evaluated, suggesting the predominance of the bornite and chalcocite mechanism (identified by X-ray diffraction), in which chalcopyrite undergoes initial reduction followed by dissolution. This mechanism was facilitated by maintaining the solution potential (ES) below the Nernst potential (E4 and E5). To elucidate these findings, a semiconductor-based chalcopyrite leaching model was proposed in which electron injection by Fe(II) ions accelerate reactions and the formation of an accumulation layer in the space charge region of chalcopyrite, specifically when ES < EF (or Eredox > EF, on an energy scale). In addition, Response Surface Methodology (RSM) was employed to generate a model capable of effectively predicting the experimental data, yielding significant results with p < 0.05 and a coefficient of determination (R2) of 95.05 %. Understanding the dissolution of chalcopyrite ore based on semiconductor electrochemistry and assessing the spontaneity of different pathways is crucial for promoting efficient leaching.