Enhanced Electroreductive Removal of Bromate by a Supported Pd–In Bimetallic Catalyst: Kinetics and Mechanism Investigation

In this work, the electroreductive removal of bromate by a Pd 1 –In 4 /Al 2 O 3 catalyst in a three-dimensional electrochemical reactor was investigated. A total of 96.4% of bromate could be efficiently reduced and completely converted into bromide within 30 min under optimized conditions. On the basis of the characterization results and kinetics analysis, a synergistic effect of Pd and In was observed, and Pd 1 –In 4 /Al 2 O 3 had the highest reaction rate constant of 0.1275 min –1 (vs 0.0413, 0.0328, and 0.0253 min –1 for In/Al 2 O 3, Pd/Al 2 O 3, and Al 2 O 3 ). The results of electron spin resonance and scavenger experiments confirmed that both direct electron transfer and indirect reduction by atomic H* were involved in the bromate removal process, while the direct reduction played a more important role. Moreover, the introduction of In could increase the zeta potential of Pd 1 –In 4 /Al 2 O 3, facilitating bromate adsorption and its subsequent reduction on the catalyst. Finally, a reaction mechanism for bromate reduction by Pd 1 –In 4 /Al 2 O 3 was proposed based on all the experimental results.