| Titanium dioxide (TiO2) nanomaterial is one of the functional materials that have been developed in recent years. Owing to its excellent properties such as non-toxic, large specific surface area, adjustable surface acidity, good photocatalytic activity, good thermal conductivity, good dispersibility, good chemical stability, and anti-ultraviolet ability, the TiO2nanomaterial is widely used in environmental protection, catalysis, optics, battery energy and so on. For TiO2nanoparticles, one of the key factors which determine their physical and chemical properties is specific surface area; therefore, the study of preparation methods for TiO2nanoparticles with high specific surface area is becoming one of the intense research subjects in material science.In addition, TiO2nanoparticles with high specific surface area can be used as very good adsorbents in the field of wastewater treatments. It is known that most of the previous studies are focused on photocatalytic properties of TiO2nanoparticles. On the other hand, up to now, extensive studies on the adsorption properties of TiO2nanoparticles have not been performed in view of application to water treatment. Especially, there were few reports in which TiO2nanoparticles are used as adsorbents for heavy metal ions and organic pollutants. In this paper, TiO2nanoparticles with high specific surface area were successfully synthesized by two kinds of methods, and their adsorption properties were studied.(1) A series of TiO2samples with high specific surface area have been synthesized by a hydrothermal method in the mild condition using tetrab-utyl titanate as precursor. The synthesized samples were characterized by X-ray powder diffraction (XRD), N2adsorption-desorption (BET), transmission electron microscopy (TEM),scanning electron microscopy (SEM), EDS, infrared spectroscopy (IR) and ultraviolet visible absorption spectroscopy (UV-vis). The results show that the water-dispersible TiO2nanoparticles with average particle size of3-4nm can be obtained by this method. The synthesized TiO2nanoparticles are composed of anatase and brookite, and their specific surface area is as high as416.6m2/g.The adsorbed percentages of Congo red, orange â…¡ and methyl orange on TiO2nanoparticles reach>80%, and the adsorption rates of these dyes fit well with pseudo-second-order kinetics equation. Both Langmuir and Freundlich adsorption isotherms can be used to describe the adsorption behavior of three dyes on TiO2nanoparticles. The maximum adsorption capacities for Congo red, orange II and methyl orange are estimated to be280.1mg/g,151.5mg/g and130.7mg/g, respectively.TiO2nanoparticles also exhibit a good removal ability for Cr (VI) with the maximum adsorption capacity of47.9mg/g. The adsorption rate of Cr(VI) fits well with pseudo two order kinetics, and the adsorption data can be depicted using Freundlich adsorption isotherm model.(2) High specific surface area TiO2particles have also been synthesized by the modified Stober Method, using tetrabutyl titanate as precursor and triethylamine as catalyst. The samples were characterized by XRD, BET, SEM, EDS, IR and UV-vis. The results show that the synthesied samples are amorphous TiO2with the maximum specific surface area of342m2/g. The amorphous TiO2exhibits good adsorption ability for Congo red with the maximum adsorbed percentage of87.6%. Freundlich adsorption isotherm can better describe the adsorption of Congo red on the amorphous TiO2, and the maximum adsorption capacity is estimated to be242.7mg/g. |
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