Chemical Dissolution of Chalcopyrite Concentrate in Choline Chloride Ethylene Glycol Deep Eutectic Solvent

Currently, the high demand for copper is in direct contrast with the decrease in the mineral grade and, more significantly, the concerns regarding the environmental impact that arise as a result of processing such low-grade materials. Consequently, new mineral processing concepts are needed. This work explores the chemical dissolution of chalcopyrite concentrate at ambient pressure and moderate temperatures in a deep eutectic solvent. Copper and iron are dissolved without changing their oxidation state, without solvent pH change, and stabilized as a chloride complex with no evidence of passivation. Chemical equilibria of the metallic chloride complexes limit the dissolution, and the step that is rate-controlling of the kinetics is the interdiffusion of species in the solvent. The chemical mechanism may involve initial chloride adsorption at positive sites of the solid surface, pointing out the importance of surfaces states on chalcopyrite particles. A model based on a shrinking particle coupled with pseudo-second-order increase in the liquid concentration of copper describes the dissolution kinetics and demonstrates the importance of the liquid to solid ratio. Iron and copper can be recovered separately from the solvent, which highlights that this concept is an interesting alternative to both redox-hydrometallurgy and pyrometallurgy to obtain copper by the processing of chalcopyrite concentrate.

Automated summary

This study explores the chemical dissolution of chalcopyrite concentrate using a deep eutectic solvent at ambient pressure and moderate temperatures. The results show that copper and iron can be dissolved without changing their oxidation state or solvent pH, and they are stabilized as chloride complexes. The dissolution process is limited by the chemical equilibria of the metallic chloride complexes, and the rate-controlling step is the interdiffusion of species in the solvent. The study also highlights the importance of surface states on chalcopyrite particles and the liquid to solid ratio in the dissolution kinetics. Iron and copper can be recovered separately from the solvent, making this method an interesting alternative to traditional copper extraction processes.