Sol–gel fluorinated TiO2–clay nanocomposite: study of fluor-titanium interaction on the photodegradation of phenol

摘要

Abstract We investigated the effect of fluorination of a nanocomposite photocatalyst on phenol photodegradation. We synthesized a new photocatalyst (SG750, SBET?=?16.58 m2 g?1) by a sol–gel route, using titanium (IV) tetrabutoxide- and pyrophyllite-type clay, respectively, as precursor and support. The samples were characterized by FTIR, XRD, BET, SEM and DRS UV–Vis techniques. A fluorinated photocatalyst (F-SG750, SBET?=?13.32 m2g?1) was synthesized with properties unlike other fluorinated photocatalysts reported in the literature. The results obtained prove that, contrary to other investigations in which the generation of free hydroxyl radicals (·OHfr) was increased with the fluorinated photocatalysts, in F-SG750 it resulted from the generation of surface hydroxyl radicals (·OHsf), which considerably increased. Consequently, the title photocatalyst gave rise to a higher photodegradation rate constant of phenol (kapp) than SG750. The response surface methodology (RSM) was used to optimize the operational parameters in the phenol photodegradation under UV light with F-SG750 based on the composite central design (CCD). Optimal operational parameters were found to be a solution pH of 5, photocatalyst amount of 2.5?gL?1, hydrogen peroxide concentration of 8?mmol.L?1, temperature of 40?°C. Operating at optimized parameters, total degradation, 91 mineralization and non-toxicity were found, at 50?mgL?1 phenol during 2?h of degradation.