Enhanced degradation of 2,6-dimethylphenol by photocatalytic systems using TiO assisted with HO and Fe(III).

In this study, several photocatalytic degradation systems were investigated using 2,6-dimethylphenol (2,6-DMP) as a model compound. Highly reactive species are formed in four systems, Fe(III), TiO, TiO/HO and TiO/Fe(III) where complete degradation of 2,6-DMP was achieved under UV radiation. Photodegradation of the 2,6-DMP has been described by pseudo-first order kinetic model in the presence of TiO. In UV/TiO-HO system, the addition of HO in the TiO suspension improves the degradation rate of 2,6-DMP from 70% to 100% for a HO concentration of 10 M in 3 h. In homogeneous system, HO and Fe can be generated by the irradiation of Fe(III) solution. The speciation of Fe(III) obtained from Visual MINTEQ soft showed the formation of several species and Fe(OH) were the most predominant and active species in a pH range of 2.5-3.5. At a low concentration of TiO (30 mg L), an important positive effect due to the iron addition has been shown in TiO/Fe(III) system, the entrance of metallic ions at different concentrations enhanced the photocatalytic activity of TiO. A degradation percentage of 90% was achieved in the UV/TiO-Fe(III) system under optimal conditions against 57% in UV/TiO system. Strong synergistic effect was observed in the UV/TiO-HO binary system. On the basis of literature, a pathway for 2,6-DMP degradation was proposed. The mechanism of degradation of the 2,6-DMP did not involve only HO radicals, an interaction of Fe(III) in the excited state with 2,6-DMP occurred giving rise to the formation of 2,6-dimethylphenoxyl radical.