Catalytic oxidation of sulfachloropyridazine by MnO 2 : Effects of crystalline phase and peroxide oxidants

Catalytic activation of different oxidants including peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (H O ) and ozone (O ) by MnO for degradation of sulfachloropyridazine (SCP) was investigated and the effects of different crystalline phases of MnO including nanowire α-MnO , nanorod β-MnO , nanofiber γ-MnO , and nanosphere δ-MnO on catalytic ozonation of SCP were also studied. The SCP degradation and total organic carbon removal indicated that the oxidation efficiency of the peroxide oxidants followed an order of O /MnO > PMS/MnO > PDS/MnO > H O /MnO . In catalytic ozonation, SCP degradation rate constants of different MnO phases followed an order of δ-MnO > α-MnO > γ-MnO > β-MnO . Electron paramagnetic resonance (EPR) suggested that hydroxyl radicals (·OH) and singlet oxygen ( O ) might be more significant for SCP degradation than sulfate (SO ) and superoxide (·O ) radicals. Radical competition experiments demonstrated that O and ·OH contributed to 63.16% and 28.07%, respectively, for the catalytic ozonation of SCP. It was also found that more oxygen vacancies, specific surface area and exposure of MnO edges could facilitate the activation of O for O and ·OH productions and SCP degradation. The degradation pathways of SCP could mainly follow the cleavage of S-C or S-N bond and dechlorination, accompanied by hydroxylation and oxidation.