Abstract: The thermodynamics of a complex solution system, Cu(Ⅱ)-NH₃-NH₄Cl-H₂O, was presented both theoretically and experimentally. Firstly, according to the principles of simultaneous equilibrium and aqueous electronic charge neutrality of the system, a nonlinear mathematical thermodynamic model with multi-members was set up. In this model, there were six unknowns: pH value, concentration values of free Cl^－, free NH₃, total concentration values of Cu²⁺, Cl^－ and NH₃, four equilibrium equations and three equilibrium equations of total quantum of Cu²⁺, Cl^－ and NH₃, as well as an equilibrium equation of electric charge, were involved in the model. Then after specifying the values of total concentrate of NH₃ and Cl^－, the model was solved precisely using MATLAB language, and the other four unknowns were obtained. According to the values obtained above, various valuable figures regarding thermodynamic relation of the system were protracted also with MATLAB, including two and three dimensions figures. These figures and data can supply the theoretic conference for optimizing the ratio of leaching reagents in copper extraction through ammonia hydrometallurgy. Finally, the solubility of CuO were measured in the system of NH₃-NH₄Cl-H₂O. The results show that the model and the thermodynamic data obtained are reliable.

Key words:  copper hydrometallurgy; ammoniacal ammonium leaching; metal complex; thermodynamic model; MATLAB language