Photoassisted degradation of a herbicide derivative, dinoseb, in aqueous suspension of titania.

The titanium dioxide (TiO(2)) photoassisted degradation of herbicide dinoseb has been examined in aqueous suspensions under UV light irradiation. The degradation kinetics were studied under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and light intensity as well as in presence of electron acceptors such as hydrogen peroxide, potassium bromate, and potassium persulphate under continuous air purging, and the degradation rates were found to be strongly influenced by these parameters. The Degussa P25 was found to be more efficient photocatalyst as compared to other photocatalysts tested. Dinoseb was found to degrade efficiently in acidic pH and all the electron acceptors studied enhanced the degradation rate. The results manifested that the photocatalysis of dinoseb followed pseudo-first-order kinetics. A qualitative study of the degradation products generated during the process was performed by GC-MS, and a degradation mechanism was proposed.

Semiconductor-mediated Photocatalyzed degradation of a herbicide derivative, chlorotoluron, in aqueous suspensions.

The photocatalytic degradation of a herbicide derivative, chlorotoluron [3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 1], has been investigated in aqueous suspensions of titanium dioxide (TiO2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the model compound was investigated under different conditions such as type of TiO2, pH, catalyst concentration, substrate concentration, temperature, and in the presence of different electron acceptors such as hydrogen peroxide (H2O2), potassium persulfate (K2S2O8), and potassium bromate (KBrO3) besides molecular oxygen. TiO2 Degussa P25 was found to be a more efficient photocatalyst for the degradation of the model compound as compared with other photocatalysts. The degradation products were analyzed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed.