A conceptual process for copper extracti

A conceptual flowsheet is proposed and the main processing steps are evaluated for the alkaline processing of chalcopyrite where glycine is the complexing agent. Glycine is utilised in an oxidising, alkaline environment to leach chalcopyrite at atmospheric pressure and mildly elevated temperatures. Process steps to recover copper and glycine from alkaline aqueous solutions were also investigated. The leaching of chalcopyrite flotation concentrate in glycine solutions was conducted at different leach conditions in a 1.25 L leach reactor with an agitated slurry and controlled dissolved oxygen (DO) concentration. In the presence of air, oxygen or hydrogen peroxide or a mixture thereof, glycine can dissolve copper from chalcopyrite at either ambient or elevated (40–60 °C) temperatures and atmospheric pressure. Increasing temperature, pH, glycine concentration and DO concentration will increase the rate and extent of copper extraction. The extraction of copper from “as-received” chalcopyrite flotation concentrate, at a particle size of 100 μm, was shown to occur at a significant rate within 24 h. If the chalcopyrite concentrate underwent an ultra fine grind 10–20 μm with prior alkaline atmospheric pre-oxidation, 92% of the copper is leached within 17 h at 60 °C, atmospheric pressure and 2% solids during a batch leach. Prior associated with the chalcopyrite remained untreated during leaching of chalcopyrite and iron concentration in the final pregnant solution was found to be less than 20 mg/L. Copper recovery by sulphide precipitation from the leach solutions was proved to yield up to 99.1% at a Cu:S2 molar ratio of 1:1. Solvent extraction (SX) experiments with LIX 84-I demonstrated that copper can be extracted into the organic phase up to 99.4% in a single stage at an equilibrium pH range 8.8–10.0.