Study On Sono-photo Synergistic Catalysis Performance Of TiO₂-based Catalytic Materials

With the progress of human society,dealing with the problem of environmental pollution and reducing the behavior of environmental pollution are the key issues to be solved in the 21st century.Therefore,it is necessary to develop cheap,pollution-free,good performance of photocatalytic materials,and explore more efficient technologies to treat sewage.In numerous semiconductor photocatalyst,titanium dioxide（TiO₂）with catalytic activity,nontoxic,cheap are used as the main research object.The wide band gap and low quantum efficiency of TiO₂make its constraints in practical applications.Doped TiO₂technology is adopted to improve the catalyst activity.At present,the commonly used sewage treatment technology includes biological technology,chemical technology and physical technology,but these technologies have their own disadvantages.Photocatalytic reaction and ultrasonic oxidation are two advanced oxidation technologies,which can degrade organic pollutants into non-toxic small molecules,water and carbon dioxide by using strong oxidizing hydroxyl radicals produced in the reaction process.The key of ultrasonic degradation reaction lies in the cavitation effect,and ultrasonic cavitation and hydraulic cavitation can promote each other,so they have better degradation effect of organic pollutants than single ultrasonic-mechanical stirring.Although advanced oxidation technology has some effects on wastewater treatment,it does not result in absolute degradation and complete mineralization of organic pollutants.Therefore,it is possible to use ultrasonic combined with photocatalysis technology to degrade organic pollutants in water,and explore the synergistic effect of ultrasonic and photocatalysis and find the optimal conditions for sono-photo synergistic catalysis.The main contents and conclusions of this paper are as follows:TiO₂ powders were prepared by sol-gel method,and nitrogen-doped titanium dioxide（N-TiO₂）powders were prepared by high temperature solid phase method.Their photocatalytic degradation of rhodamine B（Rh B）solution was investigated.According to the ultrasound-mechanical stirring degradation reaction of rhodamine B,the optimal reaction conditions of ultrasound were selected as follows:mechanical speed 400r/min,ultrasonic water level 720 mL and rhodamine B 50 mL.The effects of the amount of anhydrous ethanol and glacial acetic acid on photocatalytic activity were investigated for titanium dioxide prepared by sol-gel method with tetrabutyl titanate as main raw material.The obtained pure titanium dioxide powder was characterized by XRD,SEM,UV-Vis and so on.The results showed that the crystal structure of the prepared pure titanium dioxide powder was anatase crystal.The prepared TiO₂is smaller than the usual band gap of anatase nano-TiO₂,resulting in the red shift of wavelength,which greatly promotes the catalytic degradation process.The prepared TiO₂ powder was degraded by pure photocatalytic reaction and non-in-situ ultrasonic method,and the optimal compositions were as follows:2 mL of anhydrous ethanol and 4.5 mL of glacial acetic acid.Synergistic effect of ultrasonic and photocatalysis indicates that the photocatalytic reaction plays a major role.N-TiO₂ powders with different N/Ti molar ratios were prepared by high temperature solid phase method with urea as nitrogen source.The obtained powders were characterized by XRD,SEM,UV-Vis and XPS.The results showed that the pure TiO₂and N-TiO₂ powders are mixed crystals of anatase and rutile type,and the particle size of N-TiO₂will increase with the increase of the ratio of N/Ti.The redshift by doping N can improve the visible light absorption of TiO₂photocatalyst.The best component for N-TiO₂ powder was obtained by photocatalytic degradation of rhodamine B:the molar ratio of urea to titanium dioxide was 13:1.The optimal N-TiO₂ powder was degraded by ultrasonic alone or ultrasonic combined with photocatalytic degradation of rhodamine B,and it was found that the acoustic-photocatalytic degradation rate was the best.