Accelerated H2O2 generation and chloride utilization in heterogeneous electro-Fenton process for mariculture wastewater treatment

• Nitrogen and oxygen doped hierarchical porous carbon spheres are synthesized. • PCS achieves a high H 2 O 2 selectivity of 92.8 % and a yield of 2655 mmol g −1 h −1 . • PCS-based HEFP enables the rapid degradation of tetracycline of 99.4 % within 2 min. • Exceeded 98 % efficiency is achieved with energy consumption of only 158.3 W h g −1 . The development of seawater compatible heterogeneous electro-Fenton technology offers significant advantages in addressing environmental concerns. It not only enables the degradation of antibiotics in seawater aquaculture wastewater, thereby reducing marine environmental pressure, but also maximizes the utilization of natural electrolytes present in seawater, facilitating more efficient resource management. Herein, we propose a nitrogen and oxygen doped hierarchical porous carbon sphere, which achieves a high H 2 O 2 selectivity of 92.8 % and a yield of 2655 mmol g −1 h −1 (at pH 8 and −0.3 V vs. RHE). A heterogeneous electro-Fenton system was constructed by integrating PCS with Fe@N-C by using seawater as the electrolyte, enabling the rapid degradation of tetracycline with an efficiency of 99.4 % within 2 min. A systematic analysis of the conversion mechanisms and roles of reactive chlorine species and reactive oxygen species in antibiotic degradation was concluded, which can be categorized into three distinct stages: (i) cathodic reduction and hydrogen peroxide activation (producing OH, 1 O 2 , HO 2 / O 2 − ), (ii) anodic oxidation (producing OCl − ), and (iii) combined action of anodic and cathodic active species (including Cl, Cl 2 − , ClO). Additionally, using a dual-electrode, membrane-free flow cell, the removal rates of various antibiotics, including sulfamethoxazole, norfloxacin, and chloramphenicol, exceeded 98 %, with a minimal energy consumption of only 158.3 W h g −1 (catholyte flow rate: 10 mL min −1 , current density: 10 mA cm −2 ). This work presents a novel and environmentally sustainable strategy for the efficient treatment of seawater aquaculture wastewater, advancing the development of eco-friendly water purification technologies.