Adsorption and degradation of some psychiatric drugs by sol-gel synthesized titania-based photocatalysts: influence of tungsten and sodium content

Mesoporous anatase nanopowders were doped with 0.05−0.5 mol% of W6+, in order to obtain more efficient photocatalyst than TiO2 Degussa P25 in the degradation of amitriptyline (AMI) under simulated solar irradiation (SSI). Dominant XRPD peaks were ascribed to anatase phase, with additional peaks which could correspond to brookite, TiO2 bronze and sodium titanate, Na2Ti9O19. The Raman scattering measurements have confirmed anatase as dominant phase, with broad Raman feature at ~270 cm−1 possibly related to Ti–O–Na stretching vibration. All W-doped nanopowders have shown enhanced adsorption and higher efficiency in photodegradation of AMI in comparison to TiO2 Degussa P25 under the same conditions. The catalyst doped with 0.4 mol% of W6+, which has shown the highest efficiency in degradation of AMI under SSI, has also been tested in degradation of alprazolam (ALP). The effect of substrate type (AMI and ALP), catalyst loading, and initial substrate concentration on photocatalytic degradation using SSI was examined. The identification of the species responsible for the photocatalytic degradation of AMI and ALP by the catalyst doped with 0.4 mol% of W6+ was performed in the presence of various scavengers under SSI. The major role in degradation of AMI may be attributed to hydroxyl radicals, whereas superoxide anion radicals, singlet molecular oxygen and hydroxyl radicals contribute to degradation of ALP.