Study On Catalytic Ozonation Towards Oxalic Acid Degradation Based On Metal Doped OMS-2

Ozone?O₃?,as a robust oxidizing agent?E⁰ = 2.07 eV?,can react with variety class of organic compounds through direct and/or indirect reactions.In order to improve the better utilization of O₃,achieve higher pollutant efficiency and mineralization rate,reduce reaction time,heterogeneous catalytic ozonation has attracted an increasing research concentration.So far,various catalyst categories including metal oxides,metals on supports,activated carbons,and minerals,have been widely utilized in catalytic ozonation processes.Amongst,manganese oxides?MnO_x?exhibited efficient catalytic ozonation activity towards organic pollutants.Manganese oxide octahedral molecular sieve?OMS-2?is a specific of MnO_x with a one dimensional tunnel structure composed of [MnO⁶] octahedral chains,which are corner-connected to form 4.6 × 4.6 ? tunnels.The porous structure and the multivalent Mn make the OMS-2 become an interesting material in various application of catalytic oxidation.In this study,different metal?including Cu and Ag?have been doped into OMS-2 to promote its catalytic performance,a series of M-OMS_x-T composites under different M/Mn ratios and hydrothermal temperatures were successively synthesized by the hydrothermal-calcination method and used for catalytic ozonation towards oxalic acid?OA?degradation.The XRD,BET,XPS,and etc.characterizations revealed the chemical composition,bond structure and morphologies of as-prepared M-OMS_x-T composites.And the effects of catalyst dosage,initial OA concentration,solution p H,and etc.on OA degradation were systematically evaluated in order to investigate the applicability of M-OMS_x-T composites.The results indicated the Cu-OMS0.5-140 achieved the optimum catalytic activity with 97.3% of OA degradation efficiency and 98.8% of mineralization rate in 30 min.Similarly,Ag-OMS0.2-180 composites obtained 99.7% of OA degradation efficiency and 79.6% of mineralization rate?30 min?.The metal?Cu and Ag?doping would change the specific surface area and chemical bonds,and promote the transformation of multivalent metals and the generation of oxygen vacancies.Furthermore,hydroxyl radical,superoxide radical,and singlet oxygen were identified as the major reactive oxygen species and the catalytic mechanism for OA degradation enhancement was also elucidated.Meanwhile,the M-OMS_x-T composites showed excellent stability and reusability for contaminant degradation during multiple consecutive cycles.Overall,as the efficient,stable,and recyclable ozonation catalysts,the M-OMS_x-T composites could be the promising alternative materials for water purification.