Activity of Nanosized Titania synthesized by thermal decomposition of Titanium-N-Butoxide for photocatalytic degradation of phenylurea herbicides

Abstract

Anatase titania was synthesized by thermal decomposition of titanium (IV) n-butoxide in organic medium, i.e. 1,4-butanediol, toluene and mineral oil. Physical properties of titania were characterized by XRD, SEM, TEM and BET surface area techniques. Anatase titania was formed at temeperature of 270 ํC in an autoclave without contamination of other phases. Amorphous phase and agglomeration was decreased with an increase in temperature synthesis. Crystallinity of titania was improved by calcination at high temperature. Titania synthesized in 1,4-butanediol showed higher crystallinity and less agglomeration than that synthesized in toluene and mineral oil. Photocatalytic degradation of phenylurea herbicides (PUHs), i.e. diuron, isoproturon and linuron, was used to investigate catalytic activity of the synthesized titania. The calcined titania exhibited higher activity than uncalcined titania, which can be explained by the increased crystallinity. Titania synthesized in 1,4-butanediol showed higher activity than that synthesized in toluene and mineral oil, because of higher crystallinity and lower degree of agglomeration. Chemical structure and stability of PUH affected the rate of degradation. The higher activity and less stability of structure of isoproturon give higher rate of degradation than that diuron and linuron. Degradation intermediates of PUH generated intermediates during photocatalytic process, which were formed by reaction of hydroxyl radical attacking to several sites of phenylurea structure. Oxidation at uretic group was found to be the main reaction.