2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation on WO₃-TiO₂-SBA-15 nanostructured composite

A current environmental problem is the uncontrolled use of various pesticides that are harmful to the environment and public health. The herbicide 2,4-D is widely used, making it a vector of contamination for aquatic bodies, air, soil, and biomass. In recent decades, researchers have studied remediation of this compound in the environment. In this work, WO₃ and TiO₂ were supported on SBA-15 molecular sieve by the in situ anchoring (ISA) method, with different molar percentages of WO₃ in relation to the oxide content: X = 25%, 50%, and 75%. The W-Ti-S (X) samples were characterized by XDR, XRF, Raman, FTIR, diffuse reflectance of UV-vis, and adsorption and desorption of N₂. SBA-15 mesoporous structure was not destroyed even after the incorporation of the oxides. XRD analyses associated with Raman result found a predominance of the anatase phase for titanium oxide, and the FRX showed low incorporation of nanoparticles. Photocatalytic tests indicated that the catalytic activity depends on WO₃ and TiO₂ content, although all W-Ti-S (X) samples exhibited similar TOF value. The W-Ti-S (25) sample had the highest photocatalytic activity, 76% herbicide photodegradation under ultraviolet irradiation, at 270 min. The analysis of the catalytic cycles indicated that W-Ti-S (25) keeps out 70% of photocatalytic activity in the fourth catalytic cycle. In addition, the W-Ti-S (25) catalytic activity under direct sunlight irradiation was similar to that under artificial UV irradiation.