Thermodynamic modeling of phase formation conditions in the system CuO–CO<sub>2</sub>–H<sub>2</sub>O–NH<sub>3</sub>

Phase formation in the CuO–CO2–H2O–NH3 system has been studied using thermodynamic modelling in the temperature range of 20–100°C, рo = 0.1 MPa and ammonia concentrations of 0, 0.01 and 2.0 mol/kg. The stability fields of tenorite [CuO], malachite [Cu2CO3(OH)2], azurite [Cu3(CO3)2(OH)2] were determined and the compositions of the solutions in equilibrium with the solid phases were calculated. The effect of temperature and ammonia concentration on the change in phase relations in the system was shown. It was found that during the interaction of tenorite, malachite and azurite with ammonia solutions 1.0–3.0 mol/kg, the copper content in the solution increased with increasing ammonia concentration and decreased with increasing temperature. The results presented provide a basis for understanding the mechanism of mineral formation in aqueous copper-carbonate systems, as well as for solving a number of environmental problems and developing technological processes for ammonia leaching.