Modeling AU(CN)(2)(-) extraction by mixtures of Primene JMT and Cyanex 925reagents

A chemically based thermodynamic model to pr edict the distribution coeffic ient has been developed for the Au(CN)(2)(-)-Primene JMT-Cyanex 925 system. The predictive model makes use of the extraction mechanism, speciation in the organic phase, and the equilibrium constant for the extraction reaction . The distribution coefficient of gold can be predicted by the equation D-A u = K'[H+], where K' is an effective extraction constant and [H+] is the pr oton concentration of the aqueous phase at equilibrium. Excellent agreement between the experimental data and the predicted value was obtained. Furthe rmore, for the present extraction system the equilibrium isotherm was deter mined at 20 degrees C.