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

Catalytic activation of different oxidants including peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (HO) 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 > HO/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.