Persulfate oxidation of tetracycline, antibiotic resistant bacteria, and resistance genes activated by Fe doped biochar catalysts: Synergy of radical and non-radical processes

To reduce the adverse effects of antibiotics and antibiotic resistance genes (ARGs) in the environment, this study employed iron-loaded biochar (Fe-LBH) as an activator in a persulfate (PDS) oxidation system to degrade tetracycline (TC), inactivate antibiotic resistant bacteria (ARB), and remove ARGs. TC was removed efficiently (more than 85%) in the Fe-LBH-PDS system within 30 min, which was higher than that in the pristine biochar-PDS system (15.5%). The Fe doping amount in biochar, PDS, and catalyst dose significantly affected TC degradation. Furthermore, the Fe-LBH-PDS system inactivated 60.4% of ARB (Pseudomonas aeruginosa HLS-6) within 60 min. The removal efficiencies of ARGs (sul1 and sul2) and intI1 were 0.05–0.60- and 1.54–2.74 log2-fold, respectively. Fe (II) and oxygen functional groups (e.g., -C-OH and -C = O) were verified as the reactive sites for PDS activation. In addition, according to the results of electron paramagnetic resonance (EPR) and radical quenching experiments, the radical pathway dominated by [rad]OH and the non-radical pathway dominated by singlet oxygen (¹O₂) play synergistic roles in the Fe-LBH-PDS oxidation process. These findings provide a possible application of Fe-LBH-PDS for TC degradation and hindering antibiotic resistance dissemination in wastewater treatment practice.