Efficient peroxymonosulfate activation by iron-cobalt bimetallic biochar for rapid removal of antibiotic resistant bacteria, antibiotic resistance genes, and ampicillin: The coexisting of free-radical and non-radical pathways

As a typical "One Health" issue, antibiotic resistance has been considered as a worldwide threat to public health. And its spread can be restricted by antibiotics degradation, inactivation of antibiotic resistant bacteria (ARB), and removal of antibiotic resistance genes (ARGs). In this study, iron-cobalt bimetallic biochar (Fe-Co@BC) activated peroxymonosulfate (PMS) system was applied to degrade ampicillin (AMP), inactivate ARB (E. coli DH5α), and remove ARGs (plasmid-encoded blaTEM-1). AMP was degraded efficiently (about 99 %) in the Fe-Co@BC/PMS system within 40 min, and the catalyst still showed good stability after four cycles. Similarly, the Fe-Co@BC/PMS system achieved complete inactivation of ARB (about 107 CFU/mL) within 5 min, and the oxidative damages of ARB were further verified in terms of cell viability, cell membrane integrity, and enzyme activity. The removal efficiency of blaTEM-1 was 3.47 log within 60 min, and the catalyst dose, PMS concentration, initial ARB concentration, pH, and inorganic anions had significant effects on blaTEM-1 removal. The coexistence of non-radical (1O2, electron transfer) and free-radical (SO4−, O2, and OH) pathways in the Fe-Co@BC/PMS system was demonstrated by electron paramagnetic resonance techniques and free radical quenching experiments, with SO4− and 1O2 being the main reactive species. XPS results showed that redox cycles between Co (III)/Co (II) and Fe (III)/Fe (II) were important to the efficient catalytic performance of Fe-Co@BC. Moreover, possible degradation pathway of AMP was proposed according to LC-MS results and density functional theory analysis. The results obtained in this study provide a novel sight on preventing the propagation of antibiotic resistance in aquatic settings.