Study On Photoelectrocatalytic Degradation Of Organophosphorus Pesticides By Pt-TiO₂ Nanotubes

TiO₂ nanotubes electrode is fabricated by anodic oxidation method. FESEM and XRD results indicate that the top-opened TiO₂ nanotubes are well aligned and organized into high-density uniform with length ranging in size from 300 to 400 nm. As the 350℃annealed sample crystallized in the anatase phase, which is in good photocatalytic activity. Then nano-Pt coating is deposited on the TiO₂ naotubes by constant current electrodecomposition with the chloroplatinic acid as electrolyte. Pt-TiO₂ nanotubes electrode remain tube-like structure and anatase, TiO₂ nanotubes appearance shape and structural performance are not affected by Pt. Electrochemical test results show that the Pt-TiO₂ nanotubes electrodes have higher photoelectrocatalytic performancehan TiO₂ nanotubes electrodes.In quartz glass reactor, the photoelectrocatalytic degradation of DDVP in aqueous solutions as well as the effect factors such as bias potential, concentration of DDVP, the initial pH value in solution, different parameters Photoelectric and the volume of H₂O₂ are investigated. The DDVP degradation first-order kinetic constant and photoconversion efficiency using Pt-TiO₂ nanotubes electrodes are compared to that of using TiO₂ nanotubes electrodes in the same condition. The comparison of photocat-alysis, electrocatalysis and photoelectrocatalytic degradation efficiency is also evaluated. The interimproducts arealso deduced. The result indicates that the photocatalysis and the electrochemical process have a significant synergic effect on the degradation of DDVP. The photoelectrocatalysis of DDVP is enhanced when increasing bias potential, reduce DDVP concentration,at pH 6 and add H₂O₂. This result indicated that the kinetic constant of PEC degradation of DDVP and photocon version efficiency on Pt-TiO₂ nanotubes electrode is 1.7 times of photocatalysis degradation, 35.5 higher than that of electrocatalysis degradation.The Photoelectrocatalytic dichlorvos comparison with triazophos using Pt-TiO₂ nanotubes electrodes is investigated. The result shows that the degradation rate of DDVP is higher than the complex structure of triazophos. Some intermediate product such as trichlorfon, trimethyl phosphate, formic acid and acetic acid, and other substances are the photoelectrocatalytic process of products.