Preparation And Application Of Iron-manganese Composite Oxide Ozone Catalysts

The high concentration organic wastewater produced by coal chemical enterprises is not only increasing in output,but also can not be effectively treated by conventional biochemical treatment process,which results in serious environmental pollution.Heterogeneous catalytic ozonation technology is considered as an effective method for advanced treatment of coal chemical wastewater because of its strong oxidation and no secondary pollution,but the traditional single valence metal oxide catalyst has low electron transfer efficiency and low hydroxyl radical production.Transition metal composite oxides has various valence states of metal ions,which can improve electron transfer efficiency,catalytic activity and hydroxyl radical yield.To this end,this paper selects FeMnto synthesize composite oxides as catalyst of ozone,because they have multiple valence states and easy to get.From two aspects of preparation conditions and process parameters to build the efficient ozone heterogeneous catalytic oxidation system,that laid a foundation for the engineering application of Fe-Mn composite oxides catalyst.The main research contents are as follows:Using FeSO₄·7 H₂O and MnSO₄·H₂O as precursors,magnetic powder catalysts for Fe-Mn composite oxides were synthesized by co-precipitation-aging-roasting technology.The effects of roasting temperature,ratio of Fe/Mn and roasting time on the activity of Fe-Mn composite oxides were investigated.When the calcination temperature was 500?,the molar ratio of Fe to Mn was 1:1,and the calcination time was 4 h,the catalyst had the best activity,the TOC removal rate reached 39.68%,and the reaction rate constant reached 7.49×10^-3 min^-1.The results of XRD,SEM and BET showed that the catalyst particles were uniformly distributed in the shape of spikes and sheets,interwoven with each other.The specific surface area was 46.67m² g^-1,the average pore volume was 0.16 cm³ g^-1,and the average pore size was 2.52 nm.The main groups were Fe₃O₄ and Mn₃O₄ with magnetic properties.Using p-chlorophenol(4-CP)as model reactant under optimal preparation conditions as catalyst,constructing a batch catalytic ozonation system.The influencing factors of heterogeneous catalytic ozonation and its degradation mechanism was discussed.The results showed that the optimal process conditions were as follows:ozone dosage of 12 mg min^-1,catalyst dosage of 0.8g L^-1,water temperature of 25?,initial pH=9,the TOC removal rate could reach 46.9%.At the same time,through the investigation of FeMnO_xcatalytic effect and stability,the introduction of tert-butyl alcohol inhibitor,confirmed that FeMnO_x is the main way to produce hydroxyl radical.Finally,with FeMnO_x as the active component,a supported catalyst was designed by comparing different substrates,supporting modes and the best impregnation concentration,constructing a continuous catalytic ozone oxidation system,which was applied to the advanced treatment of secondary biochemical effluent in coal chemical industry.The results show that when the impregnation solution concentration is 0.4 mol L^-1 and the ozone dosage is 24 mg min^-1,the hydraulic retention time is 20 min and the initial pH is 9,the COD removal rate of the wastewater is as high as 67%.