The Study Of Activity Coefficients Of CuSO₄-NiSO₄-H₂O System

The study of electrolyte solution thermodynamic properties, especially the activity coefficients of components in electrolyte solution, is a useful tool for obtaining the interaction of various components and developing electrolyte solution theory. Meanwhile, the study of mean activity coefficients of electrolytes in the mixed solvent is of important significance in establishment or optimization the hydrometallurgical. The activity coefficients of the related systems of copper and nickel sulfate are determined by the isopiestic method.The research in this paper is as follows:1The osmotic coefficients of the CuSO4-H2O and NiSO4-H2O system at298.15K have been determined by the isopiestic method in the ion strength range from0.3963～6.6868mol/kg,0.3839～5.7499mol/kg,0.3877～5.7986mol/kg respectively. The experimental data were represented by the Pitzer ion-interaction model, and the Pitzer ion interaction parameters were obtained from resulting osmotic coefficients by multiple nonlinear regression. The parameters for those systems were obtained, and those were as follows:βCuSO4(0)=0.2323, βCuSO4(1)=2.489, βCuSO4(2)=-6592CCuSO4φ=0.0052,βNiSO4(1)=0.1941βNiSO4(1)=2.852βNiSO4(2)=-39.60, CNiSO4φ=0.0153. The fitting offset were0.002. The osmotic determined in this work were in good agreement with literature values This verified the reliability of the experimental device and method.2The activity coefficients of CuSO4-H2O, NiSO4-H2O binary system are verified by Gibbs-Duhem equation. The calculated value and the measured values by isopiestic method are in reasonable agreement. It states that datas by the isopiestic method are reliable.3The osmotic coefficients of the CuSO4-NiSO4-H2O system at298.15K have been determined by the isopiestic method in the ion strength range from0.3877～5.7986mol/kg. The experimental data were represented by the Pitzer ion-interaction model, and the Pitzer ion interaction parameters were obtained from resulting osmotic coefficients and the ion interaction parameters of pure salts by multiple linear regression. The parameters for those systems were θcu2+Ni2+=0.01963, Ψ Cu2+Ni2+SO42-=0.00046. The fitting offset was0.0044. The deviation between the calculated value and the experimental value was within±0.03. Those indicates that the Pitzer model can describe the system’s thermodynamics properties well at298.15K. The mean activity coefficients of CuSO4and NiSO4were also calculated for the CuSO4-NiSO4-H2O system, and these calculations establish their variations with ionic strength.