Degradation of amitrole by excitation of iron(III) aquacomplexes in aqueous solutions

The induced degradation of amitrole (3-amino-1,2,4-triazole or aminotriazole) by excitation of iron(III) aquacomplexes was investigated under irradiation at λ=365 nm. The process mainly involved the predominant monomeric species of iron(III), namely Fe(OH)2+, which leads to the formation of hydroxyl radicals upon excitation in the UV-Vis region. Competitive reactions experiments using nanosecond laser flash photolysis were undertaken for the determination of the second-order rate constant for the reaction of amitrole with hydroxyl radical. A value of 1.5×109 mol−1 l s−1 was obtained. The quantum yield of amitrole disappearance upon irradiation of the mixture amitrole/iron(III) increased with increasing oxygen concentration and was found to be independent on iron(III) and amitrole concentration. The high performance liquid chromatography (HPLC) analyses showed the formation of two main photoproducts: 5-hydroxy amitrole and urazole (2-aminothiazole). The latter product accumulated in the solution while the former rapidly disappeared with the irradiation time. Efficient mineralisation of the solutions was obtained by artificial as well as by sunlight irradiations.