Enhanced wastewater treatment via direct electrocatalytic activation of hydrogen peroxide in divided cells with flow-through electrode and bipolar membrane

Abstract

Although the activation of H2O2 by electro-generated atomic hydrogen (H*) on Pd to produce hydroxyl radical (OH) has been considered promising in wastewater oxidation, low apparent reaction kinetic constant (kobs) around 0.15∙h−1 still restricted its application, being only suitable for μg∙L−1-level decontamination. Application of water treatment containing mg∙L−1-level pollutants requires a significant increase of kobs. Herein, we introduced a 316L fiber felt as the cathode to electrocatalytic activate H2O2 in the flow-through reactor for wastewater treatment. Using recently developed μm-scale metal fiber electrode, both the diffusion of H2O2, the generation of surface-adsorbed active species of H*, stabilization of intermediate, and the mass transfer of pollutants could be enhanced in flow-through reactor. A kobs of 1.93∙h−1 of mineralization to 30 mg∙L−1 benzoic acid, being 12.8 times over previously reports, had been reached at pH 3.0, which was the most robust direct electrocatalytic activation of H2O2 accordingly up to now. The activation intermediate of OH was demonstrated by DMPO in-situ trapping and electron spin resonance measurement which guaranteed mineralization of contaminations. It was also demonstrated a balance of pH 3.0 by bipolar membrane during 180 min, which guaranteed a stable kobs during long time electrolysis. Strategies reported in this study promote electrocatalytic activation of H2O2 to be practically applicable and support further development for green water oxidation of water containing higher concentration contaminants.