Determination and modeling of activity coefficients of cobalt chloride in the (water plus ethanol) mixed solvent system by potentiometric method at 298.15 K

In this work, the thermodynamic properties of (CoCl2 + C2H5OH + H2O) system were investigated by potentiometric method and based on Pitzer ion interaction model. For this purpose, primarily the mean activity coefficients of CoCl2 in pure water and ethanol-water mixture solvent were determined using a galvanic cell without liquid junction potential of type: Co2+-ISE vertical bar CoCl2 (m), C2H5OH (wt.%), H2O (100-wt.%) vertical bar Ag center dot AgCl. The measurements were performed at T = 298.15 K and at total ionic strengths from 0.001 to 6.000 mol.kg(-1) in various ethanol-water mixed solvent systems containing 0, 10, 20, 30, 40 and 50% mass fractions of ethanol. The mean activity coefficients measured were correlated with Pitzer ion interaction model and the Pitzer adjustable parameters were determined. Then these parameters were used to calculate the thermodynamics properties for under investigated system. The results showed that the Pitzer ion interaction model can satisfactory describe the investigated system. The modified three-characteristic-parameter correlation (TCPC) model was applied to correlate the experimental activity coefficient data for under investigation electrolyte system, too. The results showed that the modified TCPC model also was suitable in the case of the mixed solvent system. (C) 2014 Elsevier B.V. All rights reserved.