Removal of sulfadiazine from water by a three-dimensional electrochemical system coupled with persulfate: Enhancement effect of ball-milled CuO-Fe3O4@biochar

The CuO-Fe3O4@biochar (CFB) composite, synthesized via an eco-friendly mechanical ball milling, was employed as a particle electrode in a three-dimensional (3D) electrochemical reactor to investigate its efficiency in removing sulfadiazine (SD) from antibiotic wastewater. The study revealed that the addition of 5 g/L CFB into the 3D electrochemical system significantly enhanced SD removal, achieving a removal rate of 96.2 % compared to 33.5 % in a two-dimensional system, under optimal conditions of pH 7, persulfate concentration of 4 mM, and current density of 8 mA/cm2. The CFB particle electrode demonstrated superior catalytic activity compared to CuB, FeB, and CuFe particle electrodes. The ball milling process effectively reduced the agglomeration of CuO and Fe3O4, thereby increasing the active sites of the particle electrodes. The SD displayed remarkable removal efficiency across a broad pH spectrum ranging from 2 to 9. Scavenging experiments and electron paramagnetic resonance techniques suggested that SD removal primarily occurred via a non-radical pathway involving singlet oxygen (1O2). The synergistic effect between bimetallic ions and the reduction reaction at the cathode accelerated the cycling of Fe2+/Fe3+ and Cu+/Cu2+, thereby promoting PDS activation. Additionally, the positively charged surface of CFB facilitated contact with PDS through electrostatic attraction. The E-CFB-PDS system demonstrated excellent efficiency in removing antibiotics, and its stability and reusability make it a promising approach for treating organic pollutant wastewater.