Mechanisms Of Peroxymonosulfate Activation With Manganese Oxyhydroxide Catalyst For Removal Of 2,4-dichlorophenol In Water

With the development of industrial and agriculture,2,4-dichlorophenol?2,4-DCP?wastewater brings a great harm to the environment and human beings.In recent years,the new advanced oxidation technology has a broad application prospect in the treatment of organic pollutants.The key to advanced oxidation technology application is looking for highly efficient,stable and environmentally friendly catalyst.Manganese oxyhydroxide?MnOOH?has many characteristics of excellent catalysts,but the effect of its morphology on catalytic activity has little research.In addition,the heterogeneous catalytic system has the disadvantages of being difficult to recover and low mass transfer efficiency.However,the membrane technology can effectively improve these drawbacks.Therefore,this paper firstly synthesizes three different morphologies?nanowires,multi-branches,nanorods?MnOOH by hydrothermal method to construct MnOOH/PMS system.In order to explore the effect of morphology on the catalytic activity and the mechanism of PMS activation,XRD,SEM,FT-IR,XPS,BET,CV,Zeta potential,hydroxyl density and other characterization techniques were used.Then,the optimal morphology of the catalytic performance was selected,and the MnOOH catalytic membrane/PMS system was constructed.The system was finally analyzed for the activation mechanism and evaluated industrial application potential.The main conclusions are as follows:?1?In this paper,The MnOOH?nanowire,multi-branched,nanorod morphology?catalyst was successfully prepared by hydrothermal method,and MnOOH/PMS system was constructed.Compared with other manganese oxides?MnO₂,Mn₃O₄,Mn₂O₃?,MnOOH exhibited the highest catalytic activity.At the same time,the catalytic properties of MnOOH/PMS systems with different morphologies were investigated.The optimal catalytic performance of nanowire MnOOH/PMS system was determined.The reaction rate was 0.017 min^-1,which was significantly better than multi-branched MnOOH/PMS system(0.085 min^-1)and nanorod MnOOH/PMS system(0.0033 min^-1).?2?In order to further explore the influence of morphology on catalytic performance,the physicochemical properties of the catalyst were analyzed by BET,CV,Zeta potential and hydroxyl density characterization techniques,indicating positive zeta potential,large specific surface area and reduction potential separation,high content of surface hydroxyl sites affect the catalytic performance of MnOOH.Among them,Zeta potential may have the greatest influence on the catalytic activity of MnOOH with different morphologies.It was revealed that there are four kinds of active oxygen in the reaction system:·OH,SO₄·^-,O₂·^-and ¹O₂.It was finally determined that the high content of MnOH⁺on the surface of nanowires resulted in the highest content active oxygen of MnOOH/PMS system by XPS,quenching and ESR experiments.?3?In order to solve the mass transfer efficiency and improve the secondary pollution problem,the MnOOH catalytic membrane was successfully prepared by vacuum filtration,and the MnOOH catalytic membrane/PMS system was constructed.In the membrane reactor system,by exploring the optimal conditions,it was found that the MnOOH catalytic membrane had the best activation effect at a solid-water ratio of 0.1 g/L and a molar ratio of pollutant to PMS of 3:1.At 120 min,2,4-DCP removal rate exceeded 99%and the TOC removal rate reached 83%.?4?In order to further explore the reaction mechanism and application potential of the catalytic membrane.The FT-IR,XPS,hydrophilicity and other characterizations were tested,indicating that 2,4-DCP was adsorbed to the organic membrane interface by hydrogen bonding,thereby accelerating the reaction process with reactive oxygen species?·OH,SO₄·^-,O₂·^-,¹O₂?and achieving synergistic adsorption and oxidation.Through the test of Mn ion elution,pollution resistance and four-cycle experiment,it is shown that MnOOH membrane has good stability and application potential.