Spherical mesoporous TiO2 fabricated by sodium dodecyl sulfate-assisted hydrothermal treatment and its photocatalytic decomposition of papermaking wastewater

Spherical mesoporous TiO 2 particles were prepared by a facile hydrothermal treatment using titanium oxysulfate (TiOSO 4 ) with sodium dodecyl sulfate (SDS) as the structure-directing agent. The structure and morphology of the as-prepared TiO 2 particles were characterized by X-ray diffraction, transmission electron microscopy , field emission scanning electron microscopy , dynamic light scattering , Fourier transform infrared spectroscopy , and N 2 adsorption–desorption isotherms. The results indicate that the as-synthesized TiO 2 particles have spherical mesoporous structures. Moreover, the crystal phase of the particles was the only anatase structure. This finding was attributed to the presence of sulfate ion (SO 4 2   − ), which inhibited the anatase–rutile phase transformation and improved the crystallinity of TiO 2 during TiOSO 4 hydrolysis. The spherical mesoporous TiO 2 materials have very high surface areas, and the mesopores have narrow pore size distributions . In the degradation of papermaking wastewater under ultraviolet light irradiation , the prepared TiO 2 particles exhibited high photocatalytic activity compared with the commercial Degussa P25. The effects of various parameters such as catalyst dosage, solution pH, and irradiation time on the photocatalytic activity of the fabricated TiO 2 powders are discussed. At the optimum dose of 1.0   g   L −   1 TiO 2 at pH   4, the particles prepared using an SDS:TiOSO 4 molar ratio of 0.6 exhibited the highest photocatalytic activity, achieving 83.6% COD Cr removal rate in 12   h and 100% chroma removal rate in 8   h.