Synergistic Integration of Ion-Exchange and Catalytic Reduction for Complete Decomposition of Perchlorate in Waste Water

Abstract

Ion-exchange has been frequently used for the treatment of perchlorate (ClO₄^–), but disposal or regeneration of the spent resins has been the major hurdle for field application. Here we demonstrate a synergistic integration of ion-exchange and catalytic decomposition by using Pd-supported ion-exchange resin as an adsorption/catalysis bifunctional material. The ion-exchange capability of the resin did not change after generation of the Pd clusters via mild ethanol reduction, and thus showed very high ion-exchange selectivity and capacity toward ClO₄^–. After the resin was saturated with ClO₄^– in an adsorption mode, it was possible to fully decompose the adsorbed ClO₄^– into nontoxic Cl^– by the catalytic function of the Pd catalysts under H₂ atmosphere. It was demonstrated that prewetting the ion-exchange resin with ethanol significantly accelerate the decomposition of ClO₄^– due to the weaker association of ClO₄^– with the ion-exchange sites of the resin, which allows more facile access of ClO₄^– to the catalytically active Pd-resin interface. In the presence of ethanol, >90% of the adsorbed ClO₄^– could be decomposed within 24 h at 10 bar H₂ and 373 K. The ClO₄^– adsorption-catalytic decomposition cycle could be repeated up to five times without loss of ClO₄^– adsorption capacity and selectivity