Recovery of palladium(II) and gold(III) from diluted liquors using the resin duolite GT-73

The adsorption of Pd(II) and Au(III) on the Duolite GT-73 has been investigated. The results obtained in chloride media showed a higher adsorption for Au(III) (0.58 +/- 0.03 mmol/g resin) than for Pd(II) (0.262 +/- 0.015 mmol/g resin); however, the adsorption for Pd(II) is faster. The influence of several variables such as the hydrochloric acid concentration in both metals adsorption and the addition of thiocyanate and dioxan in the study of Pd(II) has also been considered. None of the variables tested result in an improvement of the resin capacity of the metal considered, only a slightly higher adsorption for Pd(II) is observed for a HCl concentration of 0.01 M. The adsorption of Pd(II) has also been carried out in the nitrate medium, in this case the experiments were limited by the low solubility of Pd(II) in this medium (HNO3=1.0 M). The metal adsorption found was 0.35 mmol/g resin. Acidified thiourea or sodium thiocyanate solutions as well as a hydrochloric acid solution were used for the elution of the metals, the concentrated thiourea at high acidity being the most effective one for Pd(II) as well as for Au(III). In general, the greater both the concentration of thiourea and the acidity of the solution, the easier the elution of the two metals. On the other hand, Cu(II) was readily eluted by hydrochloric acid, in contrast elutions of Au(III) and Pd(II) are less easy. Separation of Pd(II) and Au(III) from Ni(II) and Cu(II) aqueous solutions by using Duolite GT-73 is discussed. Separation of metal mixtures was carried out at different pH to improve the selective adsorption. (C) 1999 Elsevier Science B.V. All rights resented.