Reaction Mechanism of Linuron Degradation in TiO2 Suspension under Visible Light Irradiation with the Assistance of H2O2

The application of TiO2/H2O2/Vis (visible light) process for the aqueous degradation of linuron (LNR) has been investigated. The performance of TiO2/H2O2/Vis process has been compared with other processes such as TiO2/H2O2 in the dark, TiO2/Vis, and H2O2/Vis in terms of LNR decay. The result showed that more than 70% LNR could be decomposed in the TiO2/H2O2/Vis. The degradation mechanism of LNR by TiO2/H2O2/Vis process has been verified through investigation of the effects of various radical scavengers on the performance of this system, monitoring the generation of photocurrent, and comparing the intermediates and decay pathways of LNR by UV-TiO2 and TiO2/H2O2/Vis processes with 16 and 17 intermediates identified, respectively. It has been revealed that demethoxylation and demethylation through alkylic-oxidation is the major mechanism of LNR degradation while dechlorination (hydroxylation at the chlorine site) and direct hydroxylation on the benzene ring is minor in both processes. Mineralization and release of chlorine and nitrogen have been also studied.