Influence of tungsten on the anatase-rutile phase transition of sol-gel synthesized TiO2 and on its activity in the photocatalytic degradation of pesticides

Abstract : In the present study, titanium dioxide and tungsten-modified titanium dioxide photocatalysts were synthesized by sol–gel method. Structural and morphological characterization has been carried out by using X-ray powder diffraction (XRD), FT-IR spectroscopy, BET surface area and transmission electron microscopy (TEM) coupled to the energy dispersive spectroscopy (EDX). The adsorption and photocatalytic performances were investigated using two chlorophenoxy herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4- dichlorophenoxy) propionic acid (2,4-DP) as models of organic pollutants in water. The obtained results show that addition of tungsten to the sol-gel preparation of TiO2 delayed the conversion of anatase to rutile phase. Further increase in tungsten loading apparently stabilized the anatase phase from transformation into inactive rutile. It is also found that, tungsten doped TiO2 exhibited a remarkable enhancement of the photocatalytic activity compared with the unmodified TiO2 for the photodegradation of the two selected organochlorines herbicides.