Ion Exchange Characteristics of Palladium and Rhodium from a Simulated Radioactive Liquid Waste

Abstract

Radioactive high-level liquid waste contains significant quantities of platinum group metals (PGM) such as palladium (Pd(II)), rhodium (Rh(III)) and ruthenium (Ru(III)). In this study, batch and column experiments were carried out to investigate the ion exchange characteristics of Pd(II) and Rh(III), including the effects of the ionic group of ion exchangers, solution temperature, and the concentration of nitric acid by various ion exchangers such as IRN 78 and Dowex 1x8. The elution characteristics of Pd(II) and Rh(III) by various eluents were also examined. The anion exchangers such as Dowex 1x8 with the ionic functional group of quaternary methyl ammonium had a higher adsorption capacity than anion exchangers such as IRN 78 with the amine group for the adsorption of Pd(II) from nitric acid solution. The cation exchanger, Dowex 50W, with the sulfonic group shows significantly strong Rh adsorption at a diluted nitric acid solution. The optimal nitric acid concentration by anion exchange resins was shown to be in 2–3 M for the adsorption of Pd(II) and Rh(III). The adsorbed Pd(II) and Rh(III) were effectively eluted out by 0.5M thiourea and 0.1 M nitric acid mixed solution and 6 M HC1 solution, respectively.

KEYWORDS:

• palladium
• Rhodium
• ion exchange
• adsorption
• separation
• resin
• elution
• high-level radioactive waste
• nitric acid