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