Efficient degradation of tetracycline by persulfate activation with Fe, Co and O co−doped g−C3N4: Performance, mechanism and toxicity

In this work, the porously thin layered Fe, Co and O co − doped g − C3N4 (FCOCN) was synthesized as persulfate (PS) activator for tetracycline (TC) degradation. The characterization demonstrated that Fe, Co and O doping could boost the specific surface area and modulate the electronic structure of g − C3N4. With addition of PS, the FCOCN2 exhibited the maximum TC removal efficiency of 90.1 % after 120 min reaction, and the kinetic constant was 2.67 times that of pure g–C3N4. Meanwhile, the removal ratio of total organic carbon and reaction stoichiometric efficiency of PS could reach to 68.6% and 5.2%, respectively. When the addition of catalyst and PS were 0.6 g/L and 10.5 mM, respectively, the lower pH and TC concentration, as well as higher temperature were conducive to degradation reaction with activation energy at 23.88 kJ.mol−1. As indicated by work function, a lower internal electronic excitation energy barrier enhanced electron transfer, so the active species of •O2−, 1O2, SO4•−, SO5•− and •OH could be favorably generated on over metal (II/III) redox shuttles, electron − rich O/N and electron–deficient C active sites. The quantitative structure − toxicity relationship prediction of intermediates and the acute toxicity experiment showed that the toxicity of water treated for 60 min to V. fischeri, E. coli and B. subtilis was significantly reduced. Moreover, after five consecutive degradation cycles, the removal efficiency of TC still remained at 72.7%. Besides, even in matrices of tap water, river water, municipal wastewater and medical wastewater, the elimination proportion of TC by FCOCN2/PS were 90.0%, 88.6%, 74.0% and 81.5%, respectively. Hence, the FCOCN2/PS system may be a promising alternative for highly effective treatment of antibiotic contained wastewater and environmental protection.