| Both energy depletion and environment pollution problems are becoming more and more serious to people in the world. Up to now, extensive studies have been performed for the treatment of wastewater, and many kinds of water treatment methods have been developed. Among these methods, adsorption is an ideal method for the treatment of wastewater due to its large removal ability, short reaction time, easy operation,and low cost. In recent years, due to its versatility in optical, electrical, and photochemical properties, TiO2 has been used in many different applications, including photocatalysts, sensors, photovoltaics, biomaterials, photocatalysts, solar cells, etc. In addition,mesoporous TiO2 is a promising adsorbent for its high surface area and large pore volume. On the other hand, extensive studies on the adsorption properties of mesoporous TiO2 have not been performed so far.In this paper, mesoporous TiO2 was synthesized and its adsorption capacities for several pollutants in industrial wastewater were investigated, so as to provide a more reliable theoretical data for the treatment of wastewaters.Mesoporous TiO2 was synthesized by hydrothermal method using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template with Ti(SO4)2 as Ti precursor, effects of different reaction conditions on the photocatalytic performance for methyl orange of the samples were discussed and its adsorption capacities for Cr(Ⅵ), and F- were investigated for the first time. The as-prepared mesoporous TiO2 are non-regular spherical particles and they possess a mesoporous structure with a pore diameter of 5.2 nm, pore volume of 0.33 cm3·g-1, and a surface area of 161.2 m2·g-1. When calcined at 400°C, the sample shows a surface area of 134.4 m2·g-1 and a pore diameter of 4.5 nm, and possess the best photocatalytic activity.The adsorption capacity of mesoporous TiO2 for Cr(Ⅵ) is considerably higher than that of non-mesoporous TiO2; the adsorption rate of Cr(Ⅵ) on the mesoporous TiO2 fits well with the Bangham equation. In the low concentration region, the adsorption capacity for Cr(VI) linearly increases with the increase of initial concentration of Cr(VI); and then the increase is retarded in the high concentration region. The maximum adsorption capacity of the mesoporous TiO2 for Cr(VI) is determined to be 33.9 mg·g-1.The adsorption ability of mesoporous TiO2 for is obviously superior to non-mesoporous TiO2. The adsorption capacity for methyl orange decreases with temperature incresment, showing that the adsorption of methyl orange on mesoporous TiO2 is exothermic. However, the adsorption for methyl orange is slightly influenced by pH of the solutions. The methyl orange adsorption data can be well depicted using Langmuir and Freundlich isotherms and the maximum adsorption capacity is estimated to be 454.5 mg·g-1 from Langmuir isotherm. The study on adsorption mechanism suggests that methyl orange is adsorbed on mesoporous TiO2 via electrostatic attraction and hydrogen bond formation.Compared to non-mesoporous TiO2, the mesoporous TiO2 exhibits better removal ability for F- with the maximum adsorption capacity of 27.0 mg·g-1. When the initial concentration of F- is 10 mg·L-1, the adsorption percentage of F- reaches as high as 90%, and the concentration of F- in treated water decreases to a value that is quite lower than the standard for drinking water. |
