Optimization Of Photocatalytic Properties For Nano-TiO₂

Nano-TiO₂ which is superior in photocatalytic performance has become one ofthe suitable materials for degradation of toxic organic compounds. However it isdifficult to put nano-TiO₂ in practical use because of its low quanta efficiency, lowadsorption for organic compounds, uneasy to recycle etc.. Thus studies of nano-TiO₂focus mainly on its load technology and performance optimization.In this dissertation nano-TiO₂ is prepared by sol-gel method and calcined atdifferent temperatures in air and nitrogen atmosphere respectively. The effects ofpreparation conditions (calcinations atmosphere, calcinations temperature andduration) of nano-TiO₂ on its crystal phase, mean diameter, absorb wavelength, surfacecomposition and crystallinity were studied. The prepared nano-TiO₂ was used tophotocatalytically degrade methylene blue.The results show that TiO₂ calcined at 300℃ in air is anatase, at 400℃ is themixture of anatase and rutile, at 550℃ is rutile;TiO₂ calcined at 300℃ and 400℃ innitrogen are both anatase, at 550℃ is mainly rutile with a few anatase. The meandiameter of TiO₂ calcined in nitrogen is smaller than that calcined in air. Under thesame condition, the absorb wavelength of TiO₂ calcined in nitrogen is red shifted,with the maximum absorb wavelength around 435nm for TiO₂ calcined in nitrogen at550℃ for 4h. It is shown that calcining in nitrogen can decrease the crystallinity of TiO₂,increase the oxygen and nitrogen contents on TiO₂ and improve its light absorptionproperty.Nano-TiO₂ calcined at 300℃ in air and nitrogen atmosphere for 2h were used tophotocatalytically degrade methylene blue. Results show that the nano-TiO₂ calcinedin nitrogen has better photocatalytic properties, the photocatalytic degradationvelocity is higher and the degradation rate is up to 98%.