Electrochemical activation of peroxymonosulfate by 3D printed blue TiO2 nanotube arrays reactive electrochemical membrane for efficient degradation of acetaminophen

Electrocatalytic technology (EC) is a promising strategy for peroxymonosulfate (PMS) activation due to its environmental safety and energy conservation. Herein, 3D printed blue TiO2 nanotube arrays (3DP-BTNAs) reactive electrochemical membranes (REM) were designed as anode and cathode in EC and EC/PMS systems. EC/PMS system displayed superior performance for acetaminophen (ACT) degradation and detoxication. The ACT degradation in EC/PMS system was 3.70 times faster than that in EC system. Quenching experiments suggested that singlet oxygen (1O2) mediated nonradical pathway was responsible for ACT degradation in EC/PMS system, while hydroxyl radical (•OH) was the predominant reactive oxygen species (ROS) in EC system. Our study first provided direct evidence that PMS activation on cathode was mainly triggered by superoxide radical (O2•-). PMS was reduced by O2•- derived from O2 reduction on cathode, and subsequently converted into ROS for organics oxidation. However, PMS tended to adsorb on anode and formed 3DP-BTNAs-PMS* complex for organics degradation. The influencing factors (e.g., PMS dosage, flow rate) on ACT degradation in EC/PMS system were evaluated, and the obtained optimal kinetic constant and lowest energy consumption were 0.135 min−1 and 0.27 Wh/L, respectively. In addition, eight degradation products were identified and possible degradation pathways of ACT were proposed to be the cleavage of C-N bonds and benzene ring. This study is dedicated to the rational design of highly porous REM material by 3DP technology for wastewater treatment and the in-depth mechanism of PMS activation over BTNAs electrode in EC/PMS system.