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

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    Ion-exchange has been frequently used for the treatment of perchlorate (ClO<sub>4</sub><sup>–</sup>), 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 ClO<sub>4</sub><sup>–</sup>. After the resin was saturated with ClO<sub>4</sub><sup>–</sup> in an adsorption mode, it was possible to fully decompose the adsorbed ClO<sub>4</sub><sup>–</sup> into nontoxic Cl<sup>–</sup> by the catalytic function of the Pd catalysts under H<sub>2</sub> atmosphere. It was demonstrated that prewetting the ion-exchange resin with ethanol significantly accelerate the decomposition of ClO<sub>4</sub><sup>–</sup> due to the weaker association of ClO<sub>4</sub><sup>–</sup> with the ion-exchange sites of the resin, which allows more facile access of ClO<sub>4</sub><sup>–</sup> to the catalytically active Pd-resin interface. In the presence of ethanol, >90% of the adsorbed ClO<sub>4</sub><sup>–</sup> could be decomposed within 24 h at 10 bar H<sub>2</sub> and 373 K. The ClO<sub>4</sub><sup>–</sup> adsorption-catalytic decomposition cycle could be repeated up to five times without loss of ClO<sub>4</sub><sup>–</sup> adsorption capacity and selectivity
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