Removal efficiency and mechanism of bio-treated coking wastewater by catalytic ozonation using MnO2 modified with anionic precursors

In this paper, MnO2 catalyst were firstly prepared and modified by four kinds of anionic precursors (i.e., NO3-, AC-, SO42- and Cl-) through redox precipitation method. After that, bio-treated coking wastewater (BTCW) was prepared and employed as targeted pollutants to investigate the catalytic ozonation performance of prepared-MnO2 catalyst was investigated and characterized by the removal efficiencies and mechanism of the prepared bio-treated coking wastewater (BTCW), which was employed as the targeted pollutants. Specifically, the effects of specific surface area, crystal structure, valence state of Mn element and lattice oxygen content on catalytic activity of MnO2 materials were characterized by BET, XRD and XPS, respectively. Results showed that COD of BTCW could be removed 47.39% under MnO2-NO3- catalyst with 2 h reaction time, which was much higher than that of MnO2-AC- (3.94%), MnO2-SO42- (12.42%), MnO2-Cl- (12.94%) and pure O3 without catalyst (21.51%), respectively. So, MnO2-NO3- presented the highest catalytic performance among these catalysts. The reason may be attributed to a series of better physiochemical properties including the smaller average grain, the larger specific surface area and active groups, more crystal defect and oxygen vacancy, higher relative content of Mn3+ and adsorbed oxygen (Oads) than that of another three catalysts.