Construction And Application Of Electrically Assisted Wet Air Oxidation Based On MnO_x/GF

Water resource is an important strategic resource in the economic and social development.Efficient and economical treatment of industrial organic wastewater is important to improve the recycling efficiency of water resources.Electro-assisted catalytic wet air oxidation?ECWAO?is a novel development of wet air oxidation?WAO?,by making use of anodic electric field and catalyst to reduce the temperature and pressure of WAO.Manganese oxide is a common catalyst in WAO.Its variable valence and abundant surface oxygen species endow it with excellent catalytic acitivty for oxidation reactions.In this thesis,different manganese oxide catalysts were loaded on graphite felt?GF?,and the composite catalysts were applied to ECWAO system for the degradation of a series of organic pollutants.System efficiencies were systematically compared and mechanism involved in the ECWAO reaction was explored.The main work of the thesis is as follows:MnO₂/GF?MnO_x/GF?composite catalyst was prepared by hydrothermal and pyrolysis method,and its chemical structure was characterized by X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,oxygen programmed temperature desorption?O₂-TPD?and hydrogen programmed temperature reduction?H₂-TPR?.Such a composite catalyst showed excellent catalytic activity in ECWAO reaction.The ECWAO process on MnO₂/GF was able to rapidly degrade a variety of dyes,pharmaceutics and personal care products?PPCPs?under room condition.The congo red,basic fuchsin,neutral red and methylene blue were completely mineralized in 160 min,and the bisphenol A,triclosan and ciprofloxacin were mineralized by 89.9%,81.5%and 65.4%,respectively.Mechanistic study indicated a surface catalyzed non-free radical pathway for the oxidation of organic pollutants by O₂ in the ECWAO process.At this site,O₂ was decomposed into chemosorbed oxygen to combine with BPA to form a transient complex.Subsequently,the transient complex was oxidized in the anode electric field to obtain the final oxidation product.Three different manganese oxides,including MnO₂,Mn₃O₄and MnO,were fabricated on graphite felt.The catalytic behavior of catalysts with different structures in the ECWAO reaction was studied with BPA as a probe contaminant.The chemical composition and structure of manganese oxides were explored by means of XRD and XPS,indicating that the richer the oxygen species on the surface of the catalyst were,the better its catalytic performance was.It was found from O₂-TPD and H₂-TPR that the oxidation ability and oxygen mobility in the three composites were ordered as follows:Mn₃O₄>MnO>MnO₂,in good agreement with their ECWAO catalytic activities.These results are anticipated to provide guideline for the design and manufacture of ECWAO catalysts.