Degradation of aqueous ketoprofen by heterogeneous photocatalysis using Bi2S3/TiO2–Montmorillonite nanocomposites under simulated solar irradiation

Abstract The photocatalytic degradation of Ketoprofen (KP), 2-(3-benzoylphenyl)-propionic acid was studied under near UV–Vis irradiation (NUV-Vis) using supported photocatalysts. Bi 2 S 3 /TiO 2 -montmorillonite (Bi 2 S 3 /TiO 2 -Mt) photocatalysts were synthesized using a two- step ion exchange and impregnation method, and characterized using different techniques: Fourier transform infrared spectra (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and photo-electrochemistry. Successful intercalation of TiO 2 and Bi 2 S 3 in the montmorillonite (Mt) was carried out, and the corresponding energy diagram for the Bi 2 S 3 /TiO 2 heterojunction has been proposed. The resulting Bi 2 S 3 /TiO 2 -Mt nanocomposites were able to degrade KP under NUV–Vis irradiation. KP photodegradation was monitored by HPLC. The kinetics of photocatalytic transformation followed the Langmuir-Hinshelwood kinetic model. Pseudo-first-order kinetics adequately fitted the experimental data (t ½ ca. 17 min at pH 11, t ½ ca. 44 min at pH 3. 0.5 g·L −1 Bi 2 S 3 /TiO 2 (25/75)-Mt nanocomposite). Factors affecting the kinetics of the process, such as the different Bi 2 S 3 /TiO 2 ratio and initial pH solution have been discussed. KP photoproducts were identified using HPLC-MS, and the corresponding reaction mechanism has been proposed. Photodegradation of KP over Bi 2 S 3 /TiO 2 -Mt nanocomposites under NUV-Vis irradiation starts with the decarboxylation of KP and subsequent hydroxylation by HO • and oxidation by HO • and other reactive oxygen species (ROS) leads to the formation of photoproducts. TiO 2 and Bi 2 S 3 intercalated in the montmorillonite are cheap and efficient nanocomposites for the abatement of persistent organic pollutants (POP), such as KP, using NUV-Vis light.