Heterogeneous light-induced transformation of 2,6-dimethylphenol in aqueous suspensions containing goethite

Abstract The transformation of 2,6-dimethylphenol (DMP) photoinduced by goethite (α-FeOOH) in aqueous suspension has been investigated under monochromatic irradiation. The disappearance of DMP was efficient upon irradiation of goethite-DMP suspension at 365, 436 and 546 nm although the photodissolution of goethite was not observed. Oxygen has a very important role: the rate of DMP disappearance increased with the oxygen concentration in the goethite-DMP suspension. The involvement of OH radicals has been ruled out because of the non-influence of isopropanol used as a scavenger. The identified photoproducts (DMP dimer, dimethylbenzoquinone, ring opening photoproducts) are strongly in favor of the formation of the radical dimethylphenoxyl. The mechanism of DMP degradation may involve a photocatalytic process in which DMP directly reacts with positive holes, the electron being trapped by oxygen.