Modeling the phase equilibrium in liquid-liquid extraction of copper over a wide range of copper and hydroxyoxime extractant concentrations

The phase equilibrium in the loading and stripping stages of liquid-liquid extraction of copper with hydroxyoxime extractant in kerosene was studied over a wide range of Acorga M5640 extractant (5-25 vol%) and copper (1-45 g/L) concentrations. A mechanistic mathematical model explaining the phase equilibrium was developed and validated. The model accounts for the non-ideality of both the aqueous and the organic phases. The composition of the aqueous sulfate solution was calculated through speciation of the electrolytes with an ion association model. The concentration of the extractant in the organic phase has a strong effect on the equilibrium constant of the extraction reaction. The organic phase non-ideality in the loading stage was described with an empirical correlation. The model parameters were fitted against the experimental data using nonlinear regression analysis. A Markov chain Monte Carlo algorithm was used to assess the reliability of the modeling results. The model has a significantly wider range of application than previous models and thus facilitates the optimization of extractant concentration.