Enhanced removal of tetracycline via advanced oxidation of sodium persulfate and biochar adsorption

Advanced oxidation of antibiotic tetracycline (TC) is becoming an accessible and efficient technology. The removal of TC from the complex wastewater needs to be lucubrated. In this study, a TC removal system involving degradation and adsorption was established. TC degradation was accomplished by enhanced advanced oxidation via the addition of sodium persulfate (SP) and biochar into simulated wastewater containing Mn2+ and TC wastewater. The adsorption of TC and its derivatives was removed by biochar. The results indicate that the optimized reaction parameters were 3.0 g/L of biochar prepared at 600 °C (B600) and 400 mg/L of SP under acidic condition, and the removal percentage of TC was 87.48%, including 74.23% of degradation and 13.28% of adsorption; the anions Cl−, NO3−, and H2PO4− had negligible effects on the removal of TC in this Mn2+/B600/SP system. The system also functioned well with an aqueous solution with a high chemical oxygen demand (COD) concentration. Electron paramagnetic resonance (EPR) analysis indicated that ·OH and SO4− free radicals were present in the Mn2+/B600/SP system. Based on the testing and analysis results, a removal mechanism and potential TC degradation pathway for this system were proposed. TC can be degraded by ·OH and SO4− via three degradation pathways. Mn2+ can be precipitated as MnO2, and a part of the TC and its derivatives can be adsorbed on the biochar surface. The Mn2+/B600/SP system also performed satisfactorily for a complex aqueous solution with various cations and antibiotics.