Effect of hydrothermal treatment on structural and photocatalytic properties of TiO2 synthesized by sol–gel method

TiO2 nanoparticles have been prepared by sol–gel precipitation and further hydrothermal treatment. In this way, the effect of the hydrothermal treatment on the structural properties and photocatalytic activity of sol–gel synthesized catalysts has been investigated. These catalysts have been produced by hydrolysis of a mixture of isopropanol–titanium tetraisopropoxide (iPrOH–TiiP). The prepared photocatalysts were characterized by means of X-ray diffraction (XRD), surface area analysis (BET), transmission microscopy (TEM), thermogravimetric analysis (TG), scanning electron microscopy (SEM) analysis, diffuse reflectance, sedimentability analysis and aggregate size study. Besides, the structural evolution with the temperature of the photocatalysts treated or not hydrothermally was studied. It was observed that the calcination produces approaching between the characteristics of both sets of photocatalysts.The photocatalytic activity of the obtained photocatalysts was investigated, using phenol as a model pollutant. The calcination temperature is the most remarkable factor that can affect the ultimate photocatalytic activity of the prepared photocatalysts. However, the hydrothermal treatment previous to calcination led to obtain photocatalysts which exhibit larger photocatalytic activity than their homologous photocatalysts without hydrothermal treatment. The obtained photocatalyst TiO2ht600 exhibits the same photocatalytic activity per surface area than the commercial TiO2 Degussa P25 but with much faster sedimentability.

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► TiO2 has been prepared by sol–gel precipitation and further hydrothermal treatment.
► The hydrothermal treatment previous to calcination affects the structure evolution of the starting materials.
► The hydrothermal treatment leads to obtain better photocatalysts.
► TiO2ht600 exhibits high photocatalytic activity for different pollutants tested.
► TiO2ht600 is removed from solution by gravity sedimentation in only 2 h.