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.
Wenli Zhang,Jiqin Li,Ziyang Lu,Yingying Luo,Fei Chen,Pengwei Huo,Jianming Pan,Yongsheng Yan
Magnetic TiO2 nanocomposites with good monodispersity were successfully synthesized via a mild sol–gel method, which were used for removal of salicylic acid (SA) residues from aqueous solution. These as-prepared nanocomposites were extensively characterized by transmission electron microscopy, scanning electron microscope, N2 adsorption–desorption isotherm with the Brunauer-Emmett-Teller method, Fourier-transformed infrared spectra, X-ray diffraction, and vibrating sample magnetometer. These results indicated that magnetic TiO2 nanocomposites possessed the core-shell structure of good dispersibility, excellent chemical stability, and magnetic property (Ms = 22.11 emu/g). According to the results of series experiments, magnetic TiO2 nanocomposites showed fast kinetics and satisfied adsorption capacity for adsorption of SA. Under the optimum experimental condition, the adsorption process followed pseudo-second-order reaction kinetics and Langmuir adsorption isotherm. Moreover, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of SA was a spontaneous and endothermic nature of the process. In addition, magnetic TiO2 nanocomposites were proved to exhibit high catalytic efficiency for photodegradation of SA under visible light irradiation, and the intermediate products of photodegradation were inferred from the mass spectrometry.
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