Insight into electroreductive activation process of peroxydisulfate for eliminating organic pollution: Essential role of atomic hydrogen

Abstract

Electrochemically activating peroxydisulfate (PDS) can eliminate organic pollution using electron as activator without the involvement of byproducts. Notwithstanding, the process suffered from long hydraulic retention time, and the activation regime remained unclear. Herein, using Pd/Al2O3 catalyst as particle electrode for initiating PDS oxidation in the cathodic cell can degrade various organic pollutants with varying the kinetic constants from 0.0256 min−1 to 0.0645 min−1, which were at least 5-fold higher than that in previous studies. The reactive oxygen species were determined to be SO4•–/•OH. These radicals were readily formed from the single-electron reduction of PDS by electro-induced atomic hydrogen (indirect reduction mechanism), while direct two-electron transfer from electro-generated H2 to PDS consumed its oxidation capacity without yielding radical due to the higher energy barrier. Revealing the mechanism of electrochemically unleashing the oxidative power of PDS into SO4•– can rationalize the design of scalable electrode for PDS-based water purification.