| Abstract: | ● Synergistic removal of carbamazepine (CBZ) was obtained in the FeS-S2O82– process. ● SO4?? and ?OH were identified as the main radicals in the FeS-S2O82– process. ● Heterogeneous oxidation would be dominant first, followed by homogeneous reaction. ● Degradation pathway of CBZ was well elucidated by experiments and DFT calculations. As persulfate (S2O82–) is being increasingly used as an alternative oxidizing agent, developing low-cost and eco-friendly catalysts for efficient S2O82– activation is potentially useful for the treatment of wastewater containing refractory organic pollutant. In this study, the degradative features and mechanisms of carbamazepine (CBZ) were systematically investigated in a novel FeS- S2O82– process under near-neutral conditions. The results exhibited that CBZ can be effectively eliminated by the FeS-S2O82– process and the optimal conditions were: 250 mg/L FeS, 0.5 mmol/L S2O82–, and pH = 6.0. The existence of Cl? (1 and 50 mmol/L) has little influence on the CBZ elimination, while both HCO3? and HPO42? (1 and 50 mmol/L) significantly suppressed the CBZ removal in the FeS-S2O82– process. CBZ could be degraded via a radical mechanism in the FeS-S2O82– process, the working radical species (i.e., SO4?? and ?OH) were efficiently formed via the promoted decomposition of S2O82– by the surface Fe2+ on the FeS and the dissolved ferrous ions in solution. Based on the identified oxidized products and Fukui index calculations, a possible degradation pathway of CBZ was speculated. More importantly, a two-stage oxidation mechanism of CBZ elimination was speculated in the FeS-S2O82– process, the activation of S2O82– by the surface-active Fe(II) of FeS dominated in the initial 5 min, while homogeneous oxidation reactions played more essential parts than others in the following reaction stage (5–60 min). Overall, this study demonstrated that the FeS-S2O82– process is capable of removing CBZ from water efficiently. |
