PHOTOCATALYIC DEGRADATION OF DIURON ON TITANIUM DIOXIDE IN MICROREACTOR

Abstract

Photocatalytic degradation of diuron in a microreactor was investigated by using Degussa P25 titanium dioxide as photocatalyst. In this work, photocatalytic degradation of 10-ppm diuron aqueous solution was conducted in a 250 μm-thick micro-channel coated with titanium dioxide thin film. Due to a short mass transfer distance and negligible loss in light intensity by absorption, the photodegradation is significantly enhanced by using the microreactor. The solution was periodically sampled to monitor the concentration of diuron by using high performance liquid chromatography (HPLC) while the intermediates products were identified by using chromatography with mass spectroscopy (LC-MS/MS). The increase in residence time resulted in the increased. The degradation of diuron by 63% was achieved after passing through the reactor for 15 minutes. The effect of thickness of the micro-channel was also investigated. The degradation generates several intermediate products. Several degradation intermediates are generated by reactions of hydroxyl radical attacking at different sites of diuron structure during the photocatalytic degradation. There are 3 main reaction pathways, including dehalogenation of aromatic ring, hydroxylation of the aromatic ring and demethylation. In addition, the intermediate products that are formed under exposure of light and those are formed without light were investigated.