title: Selection of active phase of MnO2for catalytic ozonation of 4-nitrophenol.
abstract: Catalytic ozonation is a highly effective method in wastewater treatment, and MnO2materials are widely recognized as active heterogeneous catalysts in this process. Many works reported the progress in active MnO2synthesis, but the active phase is rarely systematically studied. In this paper, all six phases of MnO2(α-, β-, δ-, γ-, λ- and ε-) were synthesized by facile methods. Their catalytic activities in ozonation of 4-nitrophenol (4-NP) were evaluated and correlated with the physicochemical properties obtained from X-ray Diffraction (XRD), transmission electron microscopy (TEM), physical adsorption and cyclic voltammetry (CV) analysis. α- MnO2was found to be the most active catalyst in 4-NP degradation at neutral pH. MnO2with low average oxidation state (AOS) showed stronger oxidation/reduction peaks in CV characterization, which benefited catalytic decomposition of ozone to generate active species. Superoxide radical was confirmed as the main oxidizing species, along with singlet oxygen and ozone molecule oxidation in bulk solution and little contribution of oxidation on the MnO2surface. Mn2+leaching happened during catalytic ozonation, but its catalytic role is negligible. This result may give rise to the preparation of new active MnO2catalysts.
authors.affiliation: Beijing Engineering Research Center of Process Pollution Control, Division of Environmental Engineering and Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Faheem
authors.initials: F
authors.lastname: Nawaz
authors.affiliation: Beijing Engineering Research Center of Process Pollution Control, Division of Environmental Engineering and Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Cao
authors.affiliation: Beijing Engineering Research Center of Process Pollution Control, Division of Environmental Engineering and Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China. Electronic address: ybxie@ipe.ac.cn.
authors.forename: Yongbing
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Beijing Engineering Research Center of Process Pollution Control, Division of Environmental Engineering and Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jiadong
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Beijing Engineering Research Center of Process Pollution Control, Division of Environmental Engineering and Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.affiliation: University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zahid Ali
authors.initials: ZA
authors.lastname: Ghazi
mesh_terms: D000327:Adsorption; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D017895:Manganese Compounds / Q000737:chemistry*; D008956:Models, Chemical; D009596:Nitrophenols / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D017895:Manganese Compounds; D009596:Nitrophenols; D010087:Oxides; C027424:manganese oxide; D010126:Ozone; C024836:4-nitrophenol
keywords: 4-Nitrophenol; Active phase; Average oxidation state; Catalytic ozonation; MnO(2)