Simultaneous Elimination of Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes by Different Fe-N Co-Doped Biochars Activating Peroxymonosulfate: The Key Role of Pyridine-N and Fe-N Sites

Abstract

Coexistence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in environment pose a potential threat to public health. In our study, a novel advanced oxidation process for simultaneously removing ARGs and ARB by two kinds of iron and nitrogen-doped biochar based on rice straw (FeN-RBC) and sludge (FeN-SBC) was developed. All viable ARB (about 108 CFU mL-1) was inactivated in the FeN-RBC/ peroxymonosulfate (PMS) system within 40 min and did not regrow after 48h even in real water samples. Flow cytometry identified 96.7% of dead cells in FeN-RBC/PMS system, which verified the complete inactivation of ARB. Complete inactivation of ARB was associated with disruption of cell membranes and intracellular enzymes related to the antioxidant system. Whereas live bacteria ( about 200 CFU mL-1) remained after FeN-SBC/PMS treatment. Intracellular and extracellular ARGs (tetA and tetB) were efficiently degraded in the FeN-RBC/PMS system. The produced active species mainly including •OH, SO4•- and Fe (IV) and electron transfer played crucial roles in satisfactory disinfection effect of FeN-RBC/PMS. In comparison with FeN-SBC, the better catalytic performance of FeN-RBC was primarily attributed to more reactive active sites (such as C=O group and Fe-N sites), pyridine-N and Fe0 content. Density functional theory calculations indicated the greater adsorption energy and Bader charge, more stable Fe-O bond, more easily broken O-O bond in FeN-RBC/PMS, which demonstrated the stronger electron transfer capacity between FeN-RBC and PMS. To encapsulate, our study provided an effective and reliable method for the simultaneous removal of ARGs and ARB in water.

Keywords: Antibiotic-resistant bacteria, Antibiotic resistance genes, Peroxymonosulfate, N-doped Biochar, Zero-valent iron