Enhanced electro-Fenton oxidation by introducing three-phase interface with simultaneous optimization of O2 and pollutant transfer for effective tetracycline hydrochloride removal

Abstract

Mass transfer plays a dominating role in electro-Fenton (EF) system, where the transportations of gaseous O2 and dissolved pollutant were difficult to simultaneously optimize when using conventionally hydrophilic or hydrophobic electrodes (HIE/HOE). To overcome this difficulty, three-phase interface (TPI) was successfully introduced into sandwich electrode (SE) via an asymmetrical wettability design of hydrophilic catalyst on both sides of three-dimensional hydrophobic substrate. With the help of TPI in SE body, the rapid gaseous O2 transfer process led to the best OH generation of 536.4 μM, over 9 times than HIE (59.4 μM) with dissolved-O2 transfer limitation. Meanwhile, due to a large electrochemically-active area from hydrophilic catalyst layer, more exposed sites at SE surface could availably electro-adsorb 32.0% tetracycline hydrochloride (TC), ∼3.7 times than HOE with TC transfer restriction. Thanks to simultaneous optimization of O2 and pollutant transfer processes, the TPI-rich SE achieved an excellent TC mineralization of 68.0% (removal of 93.3%), far more than 9.3% of HIE and 14.7% of HOE. Therefore, this study paved an ingenious approach to mitigate two-phase (gas/liquid) transfer limitation in EF system for effective organic pollutants degradation.