Application of FeS-activated persulfate oxidation system for the degradation of tetracycline in aqueous solution

Tetracycline (TC), an antibiotic used to treat bacterial infectious diseases, is easily transferred to environmental matrixes and then sparks environmental concerns. In this study, TC was selected as a target pollutant to investigate the degradation performance of persulfate (PS) based advanced oxidation processes (AOPs) using FeS as the activator (FeS/PS). The results showed that with optimal PS and FeS concentrations of 1 mM and a pseudo-second-order rate constant (k(2)) of 3.45 L mmol(-1) min(-1), 91.39% of TC, was effectively removed within 60 min. From the perspective of degradation rate, apart from CO32-, TC decompositions by FeS/PS were hardly disturbed by the coexistence of different concentrations of Cl-, NO3-, SO42-, and humin acid. The degradation of TC under the O-2 bubbling, N-2 bubbling, and light-proof conditions also had limited effects on these AOPs. In addition, FeS exhibited excellent stability and recyclability when used as a PS activator for TC removal. The PS activated by old FeS and used FeS showed nearly identical performances on TC removal compared with the fresh FeS. It is suggested that homogeneous and heterogeneous reactions are jointly responsible for TC oxidation by FeS/PS. With the contributions of the generated, highly reactive SO4-center dot, and, in particular, center dot OH, TC enabled the mineralization of inorganic products eventually. Therefore, FeS/PS is highly recommended as an alternative AOPs in the future for TC-contaminated wastewater purification.