Study On The Effect And Mechanism Of Cobalt Manganese Spinel For Catalytic Peroxymonosulfate Oxidation Of Triclosan

Peroxymonosulfate-advanced oxidation technology(PMS-AOP)has received more and more attention as an emerging technology for chemical oxidation of organic contaminants in wastewater treatment.Recently,cobalt-based materials have been widely investigated for PMS activation.However,the disadvantages such as the resolution of cobalt ions and the limiting step of Co2+/Co3+ redox reaction still need to be resolved.Besides,the traditional radical reaction is easily quenched by the coexisting substances in the water,reducing the utilization rate of PMS.In this study,spinel-type cobalt-manganese oxide was synthesized and used as PMS catalyst to degrade triclosan(TCS)with radical reaction and nonradical reaction.The eff-iciency and mechanism of the Co2Mn1O4/PMS reaction system was further investigated.This provides the theoretical support for the development of eff-icent heterogeneous catalysts of PMS.The main research results of this study were shown as follow:(1)Spinel-type oxide Co2Mn1O4 catalyst was synthesized through facile solution-based oxidation-precipitation method and exhibited spherical nanoparticles at around 10nm diameter.The specific surface area of Co2Mn1O4 was 110.1 m2 g-1,and the cobalt and manganese in the spinel coexist in the form of multivalent states of Co2+/Co3+ and Mn2+/Mn3+/Mn4+,respectively.(2)Co2Mn1O4 used as effective PMS activator exhibited excellent TCS degradation efficiency up to 0.1225 min-1 within 30 min.Moreover,as PMS dosages and catalyst loading increased,the efficiency of catalytic degradation for TCS in Co2Mn1O4/PMS process increased.More importantly,Co2Mn1O4/PMS process can be used in wide range of pH(6-9)and slightly impacted by coexisting ions,such as Ca2+,Mg2+,C1-,SO42-,NO3-.(3)Response surface method(RSM)was also employed to model and optimize the degradation of TCS by Co2Mn1O4/PMS process.Sensitivity analysis indicated that the influence of operation factors was of the following order:catalyst dosage>PMS concentration>initial pH.It was found that 95.2%TCS was removed completely within 120s in the optimal conditions at pH 7.6,[PMS]0=179.6 mg L-1,[Co2Mn1O4]=177.1 mg L-1.(4)Multi-reaction experiments were conducted utilizing radical quenching experiments,electron paramagnetic resonance,cyclic voltammetry and X-ray photoelectron spectroscopy Sulfate radicals(SO4·-)and singlet oxygen(1O2)were unveiled to be the dominant reactive oxygen species(ROS)in Co2Mn1O4/PMS system.It was demonstrated that the reversible redox properties of Co2Mn1O4 catalyst improved the synergistic effects of Co and Mn.Additionally,the generation of 1O2 might not only promote the TCS removal rate directly,but also facilitate the metal redox cycle in spinel structure(5)The result of GC-MS analysis indicated that inermediates,2-chloro-1,4-benzoquinone,2,4-dichlorophenol,2-chloro-1,4-hydroquinone,2-chloro-5-(2,4-dichlorophenoxy)-1,4-benzenediol,would be generated in the Co2Mn1O4/PMS/TCS system.Accordingly,the degradation pathways of TCS in Co2Mn1O4/PMS system were proposed,which involved the breakage of ether bond and cycloaddition reaction.Based on the toxicity result by ECOSAR software,the overall toxicity in Co2Mn1O4/PMS process tended to be less toxic.