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 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.