Photocatalytic Degradation of a Water Soluble Herbicide by Pure and Noble Metal Deposited Nanocrystalline Films

We present the photocatalytic degradation of a water soluble sulfonylurea herbicide: azimsulfuron in the presence of titania nanocrystalline films. Efficient photodegradation of herbicide was achieved by using low-intensity black light tubes emitting in the Near-UV. The degradation of the herbicide follows first-order kinetics according to the Langmuir-Hinshelwood model. Intermediate products were identified by the LC-MS-MS technique during photocatalytic degradation. In order to increase photodegradation rate of the herbicide, we examined the effect of titania modification by depositing noble metals at various quantities and valence states. The presence of platinum at neutral valence state and optimum concentration induced higher photodegradation rates while silver-modified titania exhibited similar photocatalytic rates with those obtained with pure nanocrystalline TiO2 films. Finally, the effect of initial pH value was also examined. Acidic or alkaline media were unfavorable for azimsulfuron photodegradation.