Nitrogen-rich penicillin residue biochar for activation of peroxymonosulfate for an efficient degradation of tetracycline and its dual-pathway mechanism

Abstract

Advanced oxidation processes based on peroxymonosulfate (PMS) are effective methods for treatment of organic contaminants. Catalysts have a key role in these processes. In this study, we employed a novel penicillin residue-derived nitrogen-rich biochar to activate PMS for tetracycline (TC) degradation. Experimental results indicate that the removal rate reached its maximum (86.2%) within 20 min under the optimal conditions. In addition, after five cycles, the removal efficiency decreased only slightly. A combined analysis of the physical structure and chemical properties with chemical scavengers, electron paramagnetic resonance, and electrochemical tests confirmed that the catalyst had a dual role. Nitrogen doping and CO groups on the catalyst acted as active sites, which could produce superoxide radicals (O2•-) and singlet oxygen (1O2). The catalyst can also act as an electron transfer mediator to enhance the degradation process. Liquid chromatography–mass spectrometry (LCMS) was used to reveal the intermediates of TC degradation, potential degradation pathways are proposed, and the toxicity of the intermediates was analyzed. This research provides an effective strategy for the treatment of tetracycline and new approach to adequately remove antibiotic residues.