Ball milling Fe3O4@biochar cathode coupling persulfate for the removal of sulfadiazine from water: Effectiveness and mechanisms

This study used biochar as the substrate of the electrodes, and a simple synthetic process (ball milling) was adopted to prepare the Fe3O4 @biochar cathode enhanced coupled system of electrochemistry-potassium per -sulfate to achieve the efficient removal of sulfadiazine. Studies showed that the cracking temperature of biochar and the iron-to-carbon mass ratio determined the catalytic performance of cathodes. In addition, ball milling increased the surface functional groups of biochar and promoted the dispersion of Fe3O4 on biochar, leading to increased active sites on the Fe3O4 @biochar cathode surface. It was found that SDZ and TOC removal rates reached 95.3% and 86.9% in the coupled system of electrochemical-persulfate with SDZ concentration of 10 mg/ L, initial pH0 of 7, PDS concentration of 4 mM, current density of 30 mA/cm2, and electrode plate spacing of 4 cm. Also, this system showed excellent removal of sulfadiazine in actual water bodies. The quenching experi-ments and electron paramagnetic resonance spectra revealed that free radicals and non-radicals were involved in removing sulfadiazine, with free radicals (SO4 center dot-) being the dominant pathway. Four main degradation pathways were proposed based on the intermediates of sulfadiazine. In conclusion, Fe3O4 @biochar cathode enhanced coupled system of electrochemical-persulfate could be regarded as an efficient cleaning technology to provide a method for the removal of intractable organic pollutants.