Use of Liquid–Liquid Extraction with Neutral Organophosphorous Derivatives in the Estimation of (AuCl 4 -,H + ) Interaction Coefficients †

The liquid–liquid extraction of Au(III) from HCl solutions by a series of solvation extractants had been studied. The reagents are neutral organophosphorous derivatives such as phosphine oxides (Cyanex 921 and Cyanex 923) and phospholene derivatives (DMPL, EHMPL and NMPL). The distribution of gold between the aqueous and organic phases has been investigated under different variables. Experimental data were treated numerically in order to define the corresponding extracted species. Both experimental and numerical data were used to estimate the interaction coefficient between AuCl₄^- and H⁺ by using the specific interaction theory (SIT). Moreover, experimental data on the liquid–liquid extraction of HCl by these phosphorous derivatives were given.