Preparation Of Graphene Composites And Application Of Electrochemical Heterogeneous Catalytic Treatment Of Wastewater

Various sewage containing dyes,halogenated organic matter,nitrogenous organics and other harmful substances are difficult to treat and seriously threaten the natural environment.So it is urgent to carry out the research on the degradation of organic pollutants in sewage.Heterogeneous electro-Fenton method and complex polarity three-dimensional electrode method are new sewage treatment technologies,which can make organic matter in sewage degrade efficiently.Moreover,among the numerous catalysts,graphene’s own wrinkles and structural defects can provide a large number of active sites for the degradation of pollutants,thus improving the electrocatalytic oxidation ability of the composites.Based on these,we have prepared manganese dioxide/graphene（MnO₂/Gh）,iron trioxide-manganese dioxide/graphene（Fe₃O₄-MnO₂/Gh）heterogeneous electro-Fenton catalyst and tin dioxide-Y molecular sieve/graphene（SnO₂-Y/Gh）for electrocatalytic treatment of organic matter in wastewater.MnO₂/Gh hybrids were synthesized by redox method.The MnO₂ is evenly distributed on graphene.When the initial concentration of KMnO₄ is low,γ-MnO₂ is formed.As the concentration of KMnO₄ increases,it gradually changes toδ-MnO₂.Its morphology changed from flake to flower globula.And the MnO₂/Gh has certain thermal stability.Applied to the degradation of methylene blue in heterogeneous electro-Fenton systems,the catalytic effect ofδ-MnO₂/Gh is better than that ofγ-MnO₂/Gh in heterogeneous systems.The removal rate of methylene blue can reach 100%and the removal rate of COD can reach 89.61%by MnO₂/Gh-0.8 heterogeneous electro-Fenton system under the optimal conditions,which is about 40.93%and 48.68%higher than the traditional electrocatalytic reaction,respectively.And the removal process of COD is in accordance with the first-order reaction kinetic model.The removal rate of TOC can reach 72.2%,and methylene blue is effectively mineralized,and the·OH quenching experiments demonstrated that the reaction mainly occurres on the surface of the catalyst.Stability of the catalyst were studied.The results showed that the MnO₂/Gh-0.8 still had good catalytic performance after 5 cycles.The magnetic Fenton catalyst Fe₃O₄-MnO₂/Gh was prepared by hydrothermal method.The spherical Fe₃O₄ and rod-like MnO₂ are evenly distributed on the surface and interlayer of graphene and have a certain magnetic properties.The efficient degradation of chloroacetic acid was achieved in the Fe₃O₄-MnO₂/Gh heterogeneous electro-Fenton system under the synergistic action of Fe₃O₄ and MnO₂.The TOC removal rate can reach 80.68%under the optimum reaction conditions.The degradation process conforms to the first-order reaction kinetics model,and the conversion of organochlorine is as high as 98%.After 5 cycles,the catalyst still maintains a high activity,and the iron dissolution amount is small,so the catalyst has high stability.The SnO₂-Y/Gh composites were prepared by hydrothermal synthesis.The rutile structure of SnO₂ nanoparticles and FAU structure of molecular sieves closely combined on the surface and interlayer of graphene.The SnO₂-Y/Gh as particle electrode was applied to the fluidized three-dimensional electrode system to degrade urotropine wastewater.Under the optimum reaction conditions,the removal rate of urotropine reaches 86.78%,and the degradation efficiency is obviously higher than that of the two-dimensional system.The removal process of COD conforms to the first-order kinetic equation.After 5 cycles utilization,the removal rate of the COD was only 8.21%lower than that of the first.