The degradation of Monuron (3-(4-chlorophenyl)-1, 1-dimethylurea) photoinduced by Fe (III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe (OH) 2+, the most photoreactive species in terms of OH radical formation. These OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe (III)-hydroxy complex in aqueous solution, for the ...