Photodegradation of diuron on titania and zinc oxide

Photocatalytic degradation of diuron was investigated in the presence of zinc oxide and titanium dioxide as photocatalysts. The photocatalysts were synthesized via sol-gel method with an addition of ammonia at the content of 0%, 7%, and 28% by mass. The powder obtained was characterized by various techniques. The photocatalytic degradation of 10 ppm diuron aqueous solution was conducted in a batch photo-reactor. The solution was periodically sampled to monitor the concentration of diuron via HPLC. The decrease of total organic carbon as a result of mineralization of diuron was also observed during the degradation process. It is found that the activity of photocatalysts increase when the ammonia content is increased. Zinc oxide has higher performance in degradation and mineralization of diuron than titanium dioxide, regardless of much lower surface area. The degradation of diuron on zinc oxide is about 98% within 6 hours, while that achieved on titanium dioxide is only 45%. The degradation generated several intermediates. The intermediates species were identified by LC-MS. Degradation of diuron produces different degradation products depending on pH of the solution, wavelength of UV-radiation, and type of photocatalyst. Several degradation intermediates are generated by reactions of hydroxyl radical attacking to several sites of diuron structure during the photocatalytic degradation process.