Preparation Of Mesoporous TiO₂Composite Photocatalyst And Photocatalytic Activity Of Dye Waste Water

TiO₂as a catalyst with excellent photocatalysis performance is widely used in the field ofenvironmental protection. It has characteristics of innocuity, high catalytic activity, highoxidation capability, good stability, corrosion resistance, easy preparation and use. In recentyears, the proportion of dye wastewater in water environmental hazards has increased and it ismore difficult to degrade. Therefore, researching the new and high catalytic activityTiO₂-based photocatalyst, discussing its photocatalytic activity under visible light and findingthe reaction mechanism have been got more and more attention. Not only it is for theprotection of the safety to human life, but also it used to reduce the organic pollution has veryimportant significance.In this dissertation, mesoporous TiO₂composite photocatalyst and the composites withFe doping, N doping and Fe-N co-doping had been prepared by sol-gel method. A series ofcomposites were characterized by scanning electron microscope techniques （SEM）, X-raydiffraction （XRD），Fourier transform infrared spectroscopy（FT-IR）, etc. The photocatalyticactivities of composites and the influencing factors were evaluated by the photocatalyticdegradation of methylene blue. Some results are as follows.（1） Mesoporous silica SBA-15as a carrier of catalyst was selected and the mesoporous TiO₂composite photocatalyst had been prepared by sol-gel method. The experimental resultsshowed that the mesoporous TiO₂composite material of1.0g SBA-15and calciningtemperature at750℃had higher photocatalytic activity, good recycling and stablemesoporous structure. XRD results showed that TiO₂/1.0gSBA-15-750℃was a mixedcrystal of anatase and rutile.（2） The optimal experiment to choose the best of doping dosage and calcination temperature,the composites with Fe doping, N doping and Fe-N co-doping had been prepared by sol-gelmethod. The results of characterization and photochemical catalysis experiment showed thation doped TiO₂could improved the photocatalytic activity of the composites. Especially, thephotocatalytic activity of mesoporous TiO₂composite photocatalyst with4.0%Fe-0.5%Nco-doping was the best. The degradation rate of methylene blue was95%. Compared undopedTiO₂/SBA-15photocatalyst， the photocatalytic activity of4.0%Fe-0.5%N co-doping photocatalyst increased by17.58%.（3） The one-order reaction of photocatalytic decomposing methylene blue with compositephotocatalyst have been builded. The results showed that the reaction kinetics of degradationmethylene blue were described as one-order reaction and R2were greater than0.97. Inaddition，The reaction rate constant（K） of composites with ion doped was higher thanundoped TiO₂/SBA-15photocatalyst, and the reaction rate constant（K） of composites withFe-N co-doping was the highest as0.023min-1.（4） To decompose methylene blue as the goal，the photocatalytic influence factors of solutioninitial concentration and pH had been researched. The experimental results showed that thedegradation rate of methylene blue had an obvious improvement in the acidic conditions whenfrom pH=2to pH=4. However，composite materials had a very high adsorption capacity at thealkaline conditions and the adsorption degradation rate of methylene blue could reach morethan80%. With the initial concentration of methylene blue increased gradually from5mg/L to25mg/L, the photocatalytic degradation rate of methylene blue decreased from99.9%to89.9%.（5） Discuss the mechanism of the photoeatalysis degradation of methylene blue by usingmes-oporous TiO₂composite photocatalyst with Fe-N co-doping. The reason that ion dopingmakes band gap of the composite materials decreases may be due to the formation of a newimpurity band. UV-Vis results showed that the response range of composite photocatalystextended from400nm to600nm. Moreover，combined with the data of Vis-UV Spectroscopycould find that the absorption peak at662nm disappeared after the120min photocatalyticreaction. The result showed that methylene blue solution was degraded completely.These results may be helpful to design and construct mesoporous TiO₂photocatalystwhich is used to decompose dye wastewater with high activity. These researches providevaluable information for the optimization of TiO₂photocatalyst and discussion on thephotocatalytic degradation mechanism. For the further research on the treatment of dyewastewater offered new idea and scientific information.