Preparation Of Graphene-nitrogen-doped Titanium Dioxide/Nickel Foam Composite Film And Its Photoelectric Oxidation Synergistic Degradation Of Organic Wastewater

Organic wastewater has low biological oxygen demand（BOD）,poor biochemical purification ability,variable quantity,contains some toxic substances,and is not easily decomposed by activated sludge.It is a kind of refractory organic wastewater.Multiple advanced oxidation coupling technologies with synergistic effects are emerging technologies to solve refractory high-concentration organic wastewater.In this thesis,Ti O₂-supported foamed nickel cathode（Ti O₂-Ni）was prepared by using nickel foam with good conductivity as the substrate and titanium dioxide as the support.Under UV light,using Fe as the anode,the simulated organic wastewater methyl orange aqueous solution was degraded by photo-oxidation and electro-Fenton oxidation.First,anatase titanium dioxide particles（Ti O₂）and graphene-modified titanium dioxide（Gr-Ti O₂）particles were prepared by sol-gel method and supported on the surface of nickel foam（F-Ni）to prepare Ti O₂/F-Ni and Gr-Ti O₂/F-Ni composite films.Nitrogen-doped titanium dioxide（N/Ti O₂）was prepared by nitrogen doping.The properties of nitrogen-doped titanium dioxide（N/Ti O₂）and titanium dioxide in the degradation of methyl orange aqueous solution were studied.The results show that due to the increased specific surface area of graphene in the Gr-Ti O₂/F-Ni film,which promotes the adsorption,the degradation performance is significantly better than that of Ti O₂/F-Ni;N/Ti O₂ shows better performance under UV light irradiation.Under visible light,the kinetic coefficient is 0.018 min^-1,indicating that it also has high catalytic performance in the visible light range,while Ti O₂has almost no effect on methyl orange under visible light.Second,graphene-supported nickel foam（Gr/F-Ni）electrodes were prepared by electrochemical exfoliation-deposition method.Using the prepared Gr/F-Ni as the cathode and the iron sheet as the anode,the electro-Fenton reaction was used to degrade methyl orange in water.The results show that Gr/F-Ni exhibits relatively excellent catalytic activity,four-electron selectivity and relative stability.The optimal degradation conditions are as follows:when 4%graphene is loaded on 14cm² nickel foam,the electrocatalytic degradation efficiency is the highest when the electrification voltage is 10V,and the degradation kinetic coefficient is 1.15*10^-2 min^-1.Finally,nitrogen-doped titania-graphene/nickel foam（N/Ti O₂-Gr/F-Ni）is prepared by electrochemical method and impregnation method.Using N/Ti O₂-Gr/F-Ni as the cathode and iron as the anode,methyl orange was catalyzed to degrade under visible light and electrification.For the degradation of methyl orange,due to the synergistic effect of visible light degradation and electro-Fenton oxidation,the degradation rate of methyl orange is significantly higher than that of N/Ti O₂ and Gr/F-Ni,and the degradation rate of methyl orange（MO）increased with a kinetic coefficient of 0.087 min^-1.The analysis confirms that the addition of Gr/Ni reduces the coupling between the recombination process of photogenerated carriers and the separation ability of the electron-hole pair itself under the condition of electrification,which enhances the catalytic ability of titanium dioxide.The addition of N/Ti O₂ also accelerats the electron transfer process,and the acceleration of the two-electron transfer process results in the generation of more peroxide ions,which in turn accelerats the electro-Fenton reaction process.