Complete degradation of perchlorate using Pd/N-doped activated carbon with adsorption/catalysis bifunctional roles

Abstract

Although perchlorate (ClO4-) has a detrimental effect on human health, there have been only limited solutions for its complete degradation due to its extraordinary chemical stability. Physical adsorption using activated carbons and ion-exchange resins can provide fast, economic methods for perchlorate removal, but energy-efficient and environmentally benign ways for the disposal and regeneration of perchlorate-saturated adsorbents should be developed. Here we demonstrated an integrated process synergistically combining the strengths of physical adsorption and catalytic degradation by using 0.1 wt.% Pd on N-doped activated carbon (Pd/N-AC) as an adsorption/catalysis bifunctional material. During the perchlorate adsorption from polluted water, the N-doped carbon surface provides increased number of adsorption sites for perchlorate compared to pristine carbon surface. After the carbon is saturated with perchlorate, the perchlorate concentrated on the carbon surface can be fully decomposed into non-toxic chloride (Cl-) by the catalytic function of supported Pd in H-2 atmosphere. Notably, the N-doped carbon surface and adsorbed water synergistically enhance the catalytic decomposition rate of perchlorate. As a result, Pd/N-AC showed complete perchlorate decomposition even at very mild condition (333 K). The perchlorate adsorption/catalytic decomposition cycle could be repeated up to five times without loss of perchlorate adsorption capacity.