Study On The Degradation Of Congo Red Wastewater By Heterogeneous Catalytic Ozonation Using Metal Oxide/3D Graphene Composite As Catalyst

The purpose of this study is to develop a new catalyst of high efficiency supported metal oxide,to build a heterogeneous catalytic ozonation system to solve the problem of difficult degradation of dye wastewater treatment technology.Three-dimensional graphene（3D GN）is an ideal catalyst carrier materialh because of its unique electron transfer characteristics,porous three-dimensional network structure,larger specific surface area and easy to separate and recycle.The heterogeneous ozonation reaction catalysts of three-dimensional graphene supported Fe₃O₄,Mn3O4,CeO2 and Co3O4 metal oxide are successfully prepared by in-situ oxidation-reduction method.The catalysts prepared under different conditions are characterized by XRD,SEM,EDS,TEM,FT-IR,thermal weight,specific surface area and zero charge point test.The catalytic activity is investigated in detail by using Congo red dye wastewater as the target to determine the optimum preparation conditions of the catalyst.On this basis,the catalyst prepared in the optimum conditions is used in catalytic ozonation degradation of Congo red wastewater.And using single factor experiment and response surface analysis to explore the optimal process conditions and its reaction mechanism.The results of the experiment are as follows:（1）The characterization results show that the expected catalysts are successfully prepared in this paper.The loading of metal oxide,the concentration of graphite oxide and ultrasonic time have a certain effect on the morphology and microstructure of the surface of the catalyst and the dispersion and form of active component,thus affecting the catalytic activity of the catalyst.（2）The catalysts have higher catalytic activity with 40% Fe₃O₄ as the active component and the concentration and andultrasonic time of graphite oxide was 2.0mg/mL and 1.5 h,respectively.The Fe₃O₄/3D GN catalyst prepared in the optimal condition has high catalytic activity and stability because of the 3D GN has a synergistic catalytic action and a unique porous structure,connects with Fe₃O₄ in the way of the chemical bond and will promote the uniform distribution of nano particles.（3）Using the catalyst dosage,ozone dosage,initial pH and Congo red dye concentration as the experimental factors,and establishing the two order polynomial regression model by the CODCr removal rate as the response value.The order of the effects of various factors are as follows: catalyst dosage > ozone dosage > Congo red concentration > pH.The optimum conditions are: the dosage of catalyst and O3 are1.81 g/L and 33 mg/min respectively,the initial solution pH is 7.22 and concentration is 749.38 mg/L,the theory removal rate of CODCr can reach 73.9%.The experimentalresults show that the relative error is only 0.64%,which shows that the model is feasible.（4）The removal rate of CODCr decreased 42.58% after 120 min in addition of the tert butyl alcohol hydroxyl,while in the ozone system only decreased about 7%,indicating that the system is main of ·OH radical degradation mechanism.UV-Vis wavelength scanning and GC-MS test results show that the ·OH is generated in heterogeneous catalytic ozonation system with the Fe₃O₄/3D GN,will attack the benzene ring and naphthalene ring and accelerate the ring opening reaction,and then increase the dye mineralization rate.