A metal-free electro-Fenton process with peroxymonosulfate addition and dual cathodes for efficient water decontamination

Metal ion leaching and catalytic efficiency decline are inevitable in the Fe-based electro-Fenton (EF) process. Herein, a metal-free EF process was proposed utilizing a system with one anode and two cathodes including an air-diffusion cathode (ADC) and a commercial graphite felt cathode. In the presence of peroxymonosulfate (PMS), this system produced and activated H 2 O 2 while generating reactive oxygen species (ROS). The dual-cathode system demonstrated superior performance, achieving a carbamazepine (CBZ) removal rate constant of 0.0511 min −1 , which is 1.2 times higher than the single ADC cathode system (0.0424 min −1 ). Additionally, the CBZ removal efficiency was increased by 29% at pH = 3 and 21% at pH = 5, respectively. The dual-cathode system also resulted in a significant reduction in energy consumption (219 kWh/kg total organic carbon), which is only 65% and 36% of the energy used by the single ADC cathode system and electrochemical PMS activation system, respectively. In the dual-cathode system, 1 O 2 , •OH, and SO 4 • − were identified, with SO 4 • − might working as a medium to activate H 2 O 2 and generate more ROS. Furthermore, the tailed UV combination effectively removed nearly 100% of CBZ and discharged zero H 2 O 2 , reducing environmental impact. Overall, this work not only provides a green H 2 O 2 production and utilization strategy without metal catalysts but also offers an efficient and low residual oxidant pollutant remediation technology.