Insights Into The Roles Of Metal Ion For Peroxymonosulfate Activation By Manganese Oxides

In recent years,advanced oxidation technologies based on the activation of peroxymonosulfate（PMS）has received more and more attention on the treatment of organic pollutants due to its strong oxidizing ability,wide pH range,and no secondary pollution.Manganese oxides exhibit several advantages such as low toxicity,high abundance,diverse valence states,with are beneficial for PMS activation.However,the catalytic performance of manganese oxides is low at neutral and alkaline pH conditions.In order to improve the efficiency of manganese oxide-activated PMS to degrade pollutants,this thesis constructed a bimetallic manganese oxide synergistically activated PMS system with Ca²⁺and Cu²⁺respectively,and discussed its degradation effect and mechanism.The specific research contents of the paper are as follows:（1）The addition of Ca²⁺into Mn₂O₃/PMS system significantly improved the degradation efficiency of several pollutants.The degradation rate of Acid Orange 7（AO7）was significantly accelerated as high as 4 times than that without the addition of Ca²⁺under neutral pH conditions,but the activation energy did not decrease.Comparing the degradation rates of different substrates,it was found that the lower the p Ka value of the substrate,the more obvious the promotion effect of Ca²⁺.By the characteristion of XPS,ATR-FTIR,open circuit potential,and PMS decomposition,inhibitor experiments,as well as EPR analysis,it was believed that the complexation of Ca²⁺on the surface of Mn₂O₃promotes the decomposition of PMS and accelerates the redox cycle of Mn（III）/Mn（IV）,which will improve the pollutant degradation efficiency.（2）Cu-doped Mn₃O₄nanowire catalyst was prepared for PMS activation.The degradation rate constant of 2,4-dichlorophenol（2,4-DCP）by the Cu-Mn₃O₄activated PMS system was 22.4 times than that with the pure Mn₃O₄.By the detection with XPS,H₂-TPR analysis,it was believed that Cu replaced Mn atoms in Mn₃O₄lattice to form Cu-O-Mn bond;EPR,electrochemical experiments and inhibitor analysis confirmed that Cu-doped Mn₃O₄was beneficial for the electron transfer between the catalyst and the PMS,which accelerated the degradation of the pollutants.