Improved photodegradation and detoxification of 2,4,6-trichlorophenol by lanthanum doped magnetic TiO2

Magnetic lanthanum doped TiO2 (Fe3O4/SiO2/La-TiO2, referred to magnetic La-TiO2) and undoped magnetic TiO2 (Fe3O4/SiO2/TiO2, referred to magnetic TiO2) hybrid microspheres with uniform magnetic cores (Fe3O4/SiO2) were synthesized and characterized in this work. The results indicate that the photoactivity of the magnetic La-TiO2 is much higher than that of the magnetic TiO2 for the degradation of 2,4,6-trichlorophenol (10 mu M) under UV-visible light irradiation (lambda >= 340 nm). The initial degradation rate (R-0, mu M/min) for the photodegradation of 2,4,6-trichlorophenol (10 mu M) in a 2 g/Lmagnetic La-TiO2 dispersion is 0.45 mu M/min, which is 1.8 times larger than the value obtained in a 2 g/L magnetic TiO2 dispersion. The activities of these two catalysts decreased after seven cycles use, probably due to the reduction of surface hydroxyl groups and reaction sites. Carboxylate acids and Cl- were detected as advanced oxidation products. Thus, after 120 min of degradation, the treated 2,4,6-trichlorophenol solution showed no toxicity to HeLa cells. The results clearly demonstrate that the magnetic TiO2 particularly magnetic La-TiO2, would be an effective catalyst for the treatment of solutions polluted with chlorophenols. (C) 2014 Elsevier B.V. All rights reserved.