Degradation 2,2',4,4'-Tetrabromodiphenyl Ether by Activated Peroxymonosulfate Using Magnetic Biochar Supported α-MnO2

Abstract

Polybrominated diphenyl ethers(PBDEs) are potentially harmful to human health and the ecological environment. It is, therefore, of great significance to develop efficient, economic, and environmentally-friendly advanced oxidation systems for their effective degradation. Here, a magnetic biochar supported manganese dioxide composite(α-MnO2/MWB) synthesized by hydrothermal methods was used as a catalyst to activate peroxymonosulfate(PMS) in the degradation of 2, 2', 4, 4'-tetrabrominated diphenyl ether(BDE-47). The prepared materials were characterized by SEM, XRD, FT-IR, and BET. The results showed that α-MnO2/MWB had the best catalytic performance, and the highest degradation efficiency reached 94% under optimal conditions(α-MnO2/MWB mass ratio=1:2, catalyst dosage=0.05 g·L-1, PMS concentration=5 mmol·L-1, BDE-47 concentration=1 mg·L-1). The effect of initial pH on the system was not distinct, while chloride ions(Cl-) and humic acid(HA) inhibited the degradation of BDE-47. In comparison, nitrate ions(NO3-) and bicarbonate ions(HCO3-) had no notable effect on the degradation. SO4-· and·OH were the key free radicals in the degradation of BDE-47 in this system, with SO4-· being dominant. As showed by the XPS characterization of the materials before and after the reaction, a change in the valence states of Mn and Fe was the main reason for the activation of PMS. It was also revealed that α-MnO2/MWB composites maintained high catalytic performance after being reused up to four times.