Catalytic Ozonation for Phenol Removal over Cobalt-doped α-MnO2 Catalyst: Performance and Mechanism

Abstract

In this paper, Cobalt-doped α-MnO2 (i.e., Co-α-MnO2) were synthesized through hydrothermal method. Phenol was employed as targeted pollutants to investigate the catalytic ozonation performance of Co-α-MnO2 in terms of catalytic ability and mechanism. Results showed that that Co doped on α-MnO2 significantly improved the phenol removal increased to 97.47 % after 40 min, which was 16.46 %, 38.92 % higher than that of α-MnO2 catalytic ozonation and single ozonation without catalyst. In order to investigate the effect of Co doping on the physicochemical properties of the catalysts, the synthesized α-MnO2 and Co-α-MnO2 (2% Co/Mn doping ratio) catalysts were characterized by XRD, TEM, BET and XPS techniques, including the phase, morphology, structural properties and dispersity of the surface active species. The larger specific surface area and pore volume, more crystal defect and oxygen vacancy, higher relative content of Mn3+ and adsorbed oxygen (Oads) as well as surface hydroxyl were obtained after Co doping on α-MnO2, which could result in higher catalytic oxidation performance of Co-α-MnO2. The influence of masking agent showed that surface hydroxyl group and active free radicals (•OH and •O2-) were involved in the catalytic ozonation of phenol. This study could help recognize the role of surface hydroxyl groups and active free radicals and demonstrate the contribution of reactive oxygen species (ROS) on phenol removal in Co-α-MnO2 systems.