Solvent extraction of Au(CN)(2)(-) with mixtures of the amine Primene JMT and the phosphine oxide Cyanex 923

The partition of gold(I) between aqueous cyanide solutions and organic phases of the mixture of the amine Primene JMT and the phosphine oxide Cyanex 923 in xylene was studied at various aqueous pH values, extractant mixtures and gold concentrations, different temperatures and equilibration times. The behaviour of the extraction system with different organic diluents, aqueous ionic strengths and the selectivity of the system with respect to the extraction of different metal-cyano complexes was also investigated. The gold(I) extraction mechanism is discussed on the basis of the experimental results and numerical treatment of the experimental data, the species formed in the organic phase having the probable stoichiometry HAu(CN)(2)RNH(2)(R(3)PO)(n), n being 1 (log Ke(ext) 11.94 +/- 0.07) or 2 (log K-ext 12.45 +/- 0.15). Stripping of gold from loaded organic solutions was also studied using low ionic strength alkaline solutions (NaCN at 50 degrees C or NaOH at 40 degrees C).