High-temperature thermodynamics of ZnO–NH4Cl–H2O system

Abstract

On the basis of the principles of simultaneous equilibrium, conservation of mass, and aqueous electronic charge neutrality and the correspondence principle of ion entropy, the high-temperature thermodynamics of the ZnO–NH4Cl–H2O system was studied to predict solubility and construct Zn species distribution. The model was constructed precisely by using the MATLAB program. The total Zn2+ concentration in the solution was affected significantly by temperature and total ammonium concentration. ZnNH3Cl3− was the predominant species in the ZnO–NH4Cl–H2O system. The solubility of zinc diammine chloride in NH4Cl solution (>2 mol·L−1) in the temperature range of 303–353 K was determined using equilibrium experiments, which had results that agreed well with the theoretical value. The data and high-temperature thermodynamic model used in this paper are reliable.

Keywords

• Zinc hydrometallurgy
• Ammonium chloride
• High-temperature thermodynamics
• Ion entropy