A thermodynamic equilibrium model is developed for the distribution of copper between the phases for the system copper-sulfuric acid-xylene-/3-alkenyl 8-hydroxyquinoline. Chemical equilibrium data were obtained for the range of experimental parameters of [Cu] aq, i T (0.005 to 0.02 mol/dm3), [S]T (0.05 to 0.2 mol/dm3), extractant (0.02 to 0.06 mol/dm3), and temperature (20 to 50 ‡C). The nonlinear regression analysis best fit model is ln(Dαo/γCusu++) = 3.83 + 642(1/T - 1/308) +2 ln([HR]/[H+]γH +) where D is the distribution coefficient, αo is the reciprocal of the degree of formation of copper ion, and γ refers to activity coefficients of ionic species. The analysis of the data considers the aqueous phase ionic equilibria and a technique to estimate the impurities present in the reagent. The results indicate that the enthalpy of the reaction and the entropy change are -5338 J/mol and 14.5 J/mol · K, respectively. Also, the stoichiometric coefficient of two, determined for the extractant with cupric ion, is in agreement with other investigators.
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