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 H-2 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 H-2 and 373 K. The ClO4- adsorption-catalytic decomposition cycle could be repeated up to five times without loss of ClO4- adsorption capacity and selectivity.