Preparation Of Modified TiO₂ And Study Of Its Photodegradation In Dye Wastewater

In recent years,the excessive discharge of industrial wastewater has led to significant water quality deterioration and severely damaged the ecological environment.Many technologies,such as adsorption,bio-degradation and photo-degradation,are used to treat these waste-water.Among them,photocatalysis technology is considered as the most promising method for treating difficult-to-degrade organics in wastewater due to its high efficiency,low energy consumption and secondary pollution-free.Ti O₂,which has low cost,non-toxicity,high stability and easily adjustable band gap,is the most widely used semiconductor for photocatalytic processes.However,the photocatalytic efficiency of Ti O₂is limited by its narrow visible light response range and higher electron-hole pairs recombination ratio.As MCNOs have good electronic conductivity,saturation magnetization and ultraviolet absorption properties,the author combined MCNOs with Ti O₂to promote the separation of the electron-hole pairs generated upon irradiation.And the presence of O-Ti-C linkages reduced the band gap and further extended the absorption wavelength.In the end,the prepared catalyst recycling was also achieved.The research contents and results of this paper are as follows:（1）Recyclable MCNOs/Ti O₂magnetic composites were successfully prepared by the sol-gel method.The phase composition and micro-morphology of the synthesized composites were characterized by XRD,SEM,FT-IR,XPS,N₂adsorption-desorption and other test methods.The degradation efficiency of the sample was evaluated by degrading rhodamine B（Rh B）.The results showed that the superconductivity of MCNOs in the composite photocatalyst is conducive to the transport of photo-generated carriers.In addition,photocatalytic degradation experiments of Rh B indicated that the optimal ratio of the composites is 7%,in which the photocatalytic degradation efficiency is89%（the concentration of Rh B solution is 10 mg/L and the dosage is 0.7 g/L）.Free radical capture experiments confirmed that holes（h⁺）and hydroxyl radicals（·OH）are the main active substances in the degradation process of Rh B by MCNOs/Ti O₂.Therefore,the high conductivity and good ultraviolet absorption strength of MCNOs have a positive effect on improving the photocatalytic performance of composite materials.（2）Recyclable MCNOs/nano-Ti O₂magnetic composites were successfully synthesized via wet impregnation.XRD,SEM,FT-IR,XPS,N₂adsorption-desorption and other test methods were used to characterize and analyze the phase composition and micro-morphology of the composite photocatalytic material.The degradation efficiency of photocatalysts were evaluated by degrading rhodamine B（Rh B）.The results showed that the grain size of nano-Ti O₂was about 10 nm,and it was tightly supported on the surface of MCNOs by physical action.Photocatalytic degradation experiments of Rh B found that 4%MCNOs/nano-Ti O₂had the best photocatalytic activity and stability.When the solution concentration is 10 mg/L,the optimal dosage is 0.55g/L,and the photocatalytic degradation efficiency is the highest（97.19%）.Free radical capture experiments confirmed that superoxide radicals（·O₂^-）and hydroxyl radicals（·OH）are the main active substances in the degradation of Rh B by MCNOs/nano-Ti O₂.The smaller grain size of nano-Ti O₂is easy to be fully excited to generate more electron-hole pairs.The high conductivity of MCNOs promotes the transfer of photo-generated electrons,so the photocatalytic performance of MCNOs/nano-Ti O₂composites is greatly improved.