Activated carbon as effective cathode material in iron-free Electro-Fenton process: Integrated HO electrogeneration, activation, and pollutants adsorption.

Major challenges for effective implementation of the Electro-Fenton (EF) water treatment process are that conventional efficient cathodes are relatively expensive, and HO activation by Fe may cause secondary pollution. Herein, we propose a low-cost activated carbon/stainless steel mesh (ACSS) composite cathode, where the SS mesh distributes the current and the AC simultaneously supports HO electrogeneration, HO activation, and organic compounds (OCs) adsorption. The oxygen-containing groups on the AC function as oxygen reduction reaction (ORR) sites for HO electrogeneration; while the porous configuration supply sufficient reactive surface area for ORR. 8.9 mg/L HO was obtained with 1.5 g AC at 100 mA under neutral pH without external O supply. The ACSS electrode is also effective for HO activation to generate ‧OH, especially under neutral pH. Adsorption shows limited influence on both HO electrogeneration and activation. The iron-free EF process enabled by the ACSS cathode is effective for reactive blue 19 (RB19) degradation. 61.5% RB19 was removed after 90 min and 74.3% TOC was removed after 720 min. Moreover, long-term stability test proved its relatively stable performance. Thus, the ACSS electrode configuration is promising for practical and cost-effective EF process for transformation of OCs in water.