Résumé
The photocatalytic degradation of 3-[3,4-(dichlorophenyl)-1-methoxy-1-methylurea] (Linuron), which is oneof phenylurea herbicides, has been studied using natural iron oxide(NIO) as a heterogeneous catalyst in the presence of H2O2 under variousconditions. The characterization of this catalyst revealed that NIO has amixed elemental composition and consists mainly of iron oxide(alpha-Fe2O3). This powder contains hematite as iron source and itsdissolution provides Fe3+ cations for the Fenton-like reaction insolution. The degradation rate was strongly influenced by pH, initialconcentrations of H2O2, amount of NIO particles and type of irradiation(artificial or natural sunlight). An initial Linuron concentration of4.0 x 10(-5) mol L-1 was completely degraded after 45 min under theoptimum conditions. The decrease of chemical oxygen demand (COD) as aresult of mineralization of the herbicide was observed i.e., 99.99% ofthe initial concentration of Linuron and over 80% of COD were removedafter 6 h under our experimental conditions. The degradation of Linuronis mainly due to the formation of hydroxyl radicals as confirmation bythe use of 2.0% of isopropanol as an HO center dot scavenger. Thedecomposition of Linuron gave eight main intermediate products, and adegradation mechanism is suggested on the basis of these identifiedintermediates. The use of NIO is interesting; because in addition to itscatalytic effect, its high density enables an easy solid-liquidseparation, making it a versatile material for environmentalapplications. (C) 2015 Elsevier B.V. All rights reserved.