Degradation of tetracycline in water by biochar supported nanosized iron activated persulfate

Biochar supported nanosized iron (nFe(0)/BC) was synthesized and used as a persulfate (PS) activator to degradation tetracycline (TC). The influence of the initial pH values, PS and nFe(0)/BC dosage, initial TC concentration, and coexist anions were investigated. In the nFe(0)/BC-PS system, TC could be effectively removed at various pH values (3.0-9.0). The degradation efficiency of TC (100 mg/L) was 97.68% using nFe(0)/BC (0.4 g/L) and persulfate (1 mM) at pH 5.0. Coexisting ions (HCO₃^- and NO₃^-) had an inhibitory effect on TC degradation. The removal of TC could be fitted by a pseudo-second-order model. Electron-Spin Resonance (ESR) analysis and scavenging tests suggested that sulfate radicals (SO₄·^-) and hydroxyl radicals (HO·) were responsible for TC degradation. Details of the advanced oxidation process (AOP)-induced degradation pathways of TC were determined based on liquid chromatography mass-spectrometry (LC-MS) analysis. The nFe(0)/BC could still maintain 86.38% of its original removal capacity after five cycles. The findings of this study proved that nFe(0)/BC can be applied to activate PS for the treatment of pollution caused by TC.