Dissolution study of chalcopyrite concentrate in oxidative ammonia/ammonium carbonate solutions at moderate temperature and ambient pressure

• Higher­ copper recovery achieved in comparison with acid sulphate leaching at the same condition.
• Up to now no one has studied Sarcheshmeh copper concentrate leaching in ammoniacal solution.
• This is a comprehensive study on copper concentrate in ammoniacal solution.

In this research, the dissolution behaviour and leaching kinetics of Sarcheshmeh chalcopyrite concentrate was investigated in oxidative ammonia/ammonium carbonate solution. Temperature, concentration of ammonia and ammonium carbonate, agitation speed, solid to liquid ratio, oxygen flow rate, pH and particle size were chosen as parameters in the experiments. About 70% of copper was effectively recovered at temperature 60 °C; ammonia/ammonium carbonate concentrations: 5 M NH3 + 0.3 M (NH4)2CO3; agitation speed: 1000 rpm; solid to liquid ratio: 1:20 g/mL; oxygen flow rate: 1 L/min; leaching times: 240 min and 80% passing size finer than 42 μm. Also kinetic results and morphology and elemental composition of residue at the most suitable conditions show that, the leaching process is controlled by the diffusion of reagents or products from iron oxide passive layer formed on chalcopyrite surface. Activation energy was determined to be 25 kJ/mol.