Selective Separation and Concentration of Gold (III), Platinum (IV) and Palladium (II) by Macroreticular Hydrophobic Resin Loaded with Trioctylamine

Abstract

New ion-exchange resins for the selective adsorption of noble metal ions are prepared by loading trioctylamine (TOA) onto macroreticular hydrophobic resins. The prepared resins reveal adsorption characteristics similar to those for the commercial anion-exchange resins, whereas their elution processes are entirely different from those of the commercial resins, i. e., gold(III), platinum(IV) and palladium(II) are readily adsorbed on the present resins as anionic chloro complexes, and easily liberated from the resins as ion pairs with protonated TOA by elution with 4-methyl-2-pentanone.
The adsorption characteristics of the resins for those noble metal ions have been studied. The adsorption efficiency of the present resin is closely related to the specific surface area and hydrophobic property of the resin matrix and also the amount of TOA loaded. The optimal adsorption efficiency is obtained by the treatment of XAD-7 with 1 mmol (g-resin)^-1 of TOA. The distribution coefficients of the resin for gold(III), platinum(IV)and palladium(II) are 10^4.6, 10^3.6 and 10^3.2, respectively, in 1 mol·dm^-3 HCI solution.
The selective recovery of gold and platinum from the acid-leaching solution s of industrial scraps has been demonstrated by means of the column operation. The breakthrough capacities for gold and platinum are approximately 62 g (kg-resin)^-1 and 37 g (kg-resin)^-1, respectively. Excess amount of other common metal ions including aluminum(III) and copper (II) have not been adsorbed on the resin, and immediately leaked out of the column.