Common characteristic assessments of transformation mechanism for substituted phenylurea herbicides by reactive oxygen species (ROSs) during photocatalytic process

Abstract

Substituted phenylurea herbicides, fenuron (fen), isoproturon (iso) and linuron (lin), have been selected as target compounds, and the degradation possibility, kinetics, the contributions of reactive oxidative species (ROSs), and the degradation mechanism have been investigated during photocatalytic process. The results indicate that more than 90% of the three substituted urea herbicides are degraded within 40min. The results from ROSs reveal that surface reactions with photoholes and OH on the surface of TiO2 make major contributions, and BrO3− and S2O82− effectively promote the degradation rates of three substituted phenylurea herbicides. And then the point charges (PCs), frontier election densities (FEDs) and energies have been employed to predict the chemisorption pattern, reaction active sites and direction of reaction, respectively. With the help of calculated data and indentified degradation intermediates, the degradation pathways can be proposed as cleavage of side chain, substitution of chlorine atom and hydroxylated of parent molecules.