Prepared And Applied Graphene Based Anodes For Electrochemical Oxidation Of Printing And Dyeing Wastewater

In order to find an efficient and environmentally friendly method for the treatment of dye wastewater,this paper focuses on the degradation of organic compounds in wastewater by electrochemical oxidation.Different proportion of graphene and titanium dioxide（GN-TiO₂）composite electrodes and activated carbon eletrodes with Pt or not were prepared.Graphene oxide and all electrodes were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）,thermal stability analysis（TGA）,field emission electron scanning electron microscopy（FESEM）,energy dispersive spectroscopy（EDS）,element distribution scanning spectroscopy（Mapping）and Fourier transform infrared spectroscopy（FTIR）.The morphology,composition and crystal form of activated carbon electrode and graphene based composite electrodes were studied.The typical azo dye RBk5 was used as the target pollutant in the electrochemical oxidation experiments.The results showed that:（1）Graphene oxide（GO）was successfully prepared by modified Hummers method with the advantages of few layers and thin thickness.The surface of GO contains a large number of oxygen-containing groups so that interlayer spacing of the carbon atom become larger than before and the hydrophilicity of GO was enhanced.Therefore,TiO₂ could be uniformly distributed in the GO Suspension.GN-TiO₂ composites were synthesized by high temperature and high pressure hydrothermal method.TiO2 and GN were combined by covalent bonds,so the GN-TiO₂ composites were stable.（2）Different proportion of graphene and titanium dioxide GN-TiO₂ composites were prepared by hydrothermal method.Adhesive was prepared with polyvinylidene fluoride（PVDF）,polymethyl methacrylate（PMMA）and N,N-dimethylacetamide（DMAC）.GN-TiO₂composite electrodes were prepared by coating the GN-TiO₂ composite uniformly on the conductive carbon fabric with adhesive.The results of field emission scanning electron microscopy（FESEM）showed that it had little effect on the morphology of electrodes’surface with Pt loaded or not.（3）The effect of pH on the electrochemical oxidation of RBk5 dye wastewater with a concentration of 10ppm by GN-TiO₂（1:4）electrode was investigated.It found that The degradation efficiency was 94.8%with the reaction equilibrium time of 50 minutes when the pH was 6.6（ie,the pH was not adjusted）.And the degradation efficiency was only 6.6%when pH=3.When pH increased to 10,the degradation efficiency of RBk5 decreased to 85.3%,and the reaction equilibrium time prolonged to 210min.It can conclude that pH plays an important role in the electrocatalytic performance of the electrode.（4）The optimum technological conditions of graphene based electrochemical treatment of RBk5are as follows:anode GN-TiO2（1:4）,pH=6.6,initial concentration of RBk5 was 10 ppm,current density was 2.5 mA·cm^-2,the reaction time was 50 min,the degradation efficiency of RBk5 was 94.8%,and the current efficiency and energy consumption were 54.05%and14.8kWh/kg,respectively.what’s more,there were high degradation efficiencies for RBk5 dye wastewater with the initial concentrations of RBk5 below 20 ppm.（5）The reaction kinetics was fitted at different current densities,which was in accordance with the pseudo-first-order reaction.When the current density increased 3 times,the reaction rate constant only increased 2.3 times,indicating that the current efficiency of electrochemical oxidation degradation of RBk5 decreased with the increase of current density.