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

Magnetic lanthanum doped TiO 2 (Fe 3 O 4 /SiO 2 /La-TiO 2 , referred to magnetic La-TiO 2 ) and undoped magnetic TiO 2 (Fe 3 O 4 /SiO 2 /TiO 2 , referred to magnetic TiO 2 ) hybrid microspheres with uniform magnetic cores (Fe 3 O 4 /SiO 2 ) were synthesized and characterized in this work. The results indicate that the photoactivity of the magnetic La-TiO 2 is much higher than that of the magnetic TiO 2 for the degradation of 2,4,6-trichlorophenol (10   μM) under UV–visible light irradiation ( λ   ⩾   340   nm). The initial degradation rate ( R 0 , μM/min) for the photodegradation of 2,4,6-trichlorophenol (10   μM) in a 2   g/L magnetic La-TiO 2 dispersion is 0.45   μM/min, which is 1.8 times larger than the value obtained in a 2   g/L magnetic TiO 2 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 TiO 2 particularly magnetic La-TiO 2 , would be an effective catalyst for the treatment of solutions polluted with chlorophenols.