Abstract
Abstract In this piece of research, we have synthesized titanium dioxide (TiO 2 ) powders from titanium tetrachloride (TiCl 4 ) as an inorganic precursor by applying the sol–gel method. The effect of the calcination temperature in the range 400–800 °C on the photocatalytic performance of TiO 2 nanoparticles was studied. The samples were characterized by TEM, BET surface area measurement, DRS and XRD. They were then used for the photodegradation of two model pollutants – phenol and formic acid – under exposure to UV-A radiation. Despite the fact that the adsorption of both phenol and formic acid on the various TiO 2 nanomaterials followed the Langmuir model, their degradation kinetics followed the Langmuir–Hinshelwood model. The results emphasized a strong increase in the adsorption and in the photocatalytic activity with the TiO 2 calcined at 600 °C which was nearly 1.5 times higher than that of TiO 2 -P25 in the case of formic acid. For the degradation of phenol, TiO 2 -600 had a similar activity as TiO 2 P25. This is related to their tendency to degrade the intermediate products than the phenol itself. A formal mechanism scheme of phenol degradation has been proposed. The maximum photocatalytic efficiency was reached with the sample calcined at a temperature of 600 °C, while a further increase in temperature depleted the photocatalytic response. The highest photocatalytic activity of the sample calcined at 600 °C can be attributed to the improvement of the crystallization and the optimal anatase/rutile ratio (96/4).
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