The Photo Catalytic Degradation Of Chlorpyrifos By REE-doped Nano-TiO₂

The common way of degradation of organophosphorus pesticide is biochemical dilution treatment which poses series of problem, such as high diluted multiple, overload, unstable running and secondary pollution. However, in the action mode of photo-catalysis, light triggers catalyst to produce photo-generated electron cavity that further forms strong oxidative OH with H2O and OH-, which indiscriminately and totally degrade pollutants into H2O,CO2,PO43- etc. without the secondary pollution.Semiconductor catalyst of TiO2 is well-concerned due to the characterization of its own high-activity, great stability and no harms to human. Nevertheless, we still face some challenges need us to focus on, the low responsiveness of TiO2 to less than 375nm wavelength of ultraviolet severely reduce utilization of solar. Therefore, altering of responsiveness of TiO2 to visible light in wavelength and reduction of combination of photo-generated electron and cavity contributes to improvement of solar utilization.In our study, preparations of nano-TiO2 and mixture of tombarthite and nano-TiO2 were obtained by Sol-Gel method, degradation of Chlorpyrifos with these two preparations was determined by HPLC after exposure to light. Results were concluded as follows:Using HPLC to detect Chlorpyrifos showed there was favorable linear correlation about it(R2:0.9947 and fortified recovery:85.2-103.1%) and it can be detected rapidly, hence, HPLC is suitable for detection of Chlorpyrifos.The result showed that nano-TiO2 can obviously enhance the photocatalytic degradation speed of Chlorpyrifos. Added nano-TiO2, the degradation speed of Chlorpyrifos increased 12.1% in average under natural light, increased 16.5% in average under ultraviolet visible light. The REE-doped nano-TiO2 can improve the catalytic activity ,especially doped La have the best effects. The La-doped nano-TiO2 was compared with pure TiO2, the photocatalytic degradation speed of Chlorpyrifos increased 6.1% in average under natural light, increased 15.2% in average under ultraviolet visible light. Moreover, with the same photocatalyst, compared the degradation effects with different concentration Chlorpyrifos found that he degradation effects of Chlorpyrifos decreased with the concentration of Chlorpyrifos increased.Field experiment found that when the effective ingredient content of Chlorpyrifos were 48g/mu, the degradation effects of Chlorpyrifos with La-doped nano-TiO2 increased significantly after 3h and 6h. After 3h the degradation rate increased 26.5% compared with non-photocatalyst, increased 9.2% compared with pure TiO2. After 6h the degradation rate increased 33.1% compared with non-photocatalyst, increased 14.9% compared with pure TiO2.