Performance and mechanism of carbamazepine removal by FeS-S2O82− process: experimental investigation and DFT calculations: Fid-Bau Portal

Performance and mechanism of carbamazepine removal by FeS-S₂O₈²⁻ process: experimental investigation and DFT calculations

Long, Xuejun / Luo, Jun / Zhong, Zhenxing / Zhu, Yanxu / Zhang, Chunjie / Wan, Jun / Zhou, Haiyan / Zhang, Beiping / Xia, Dongsheng

Abstract

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.