Adsorption and Photocatalytic Degradation of Methylene Blue on TiO 2 Thin Films Impregnated with Anderson-Evans Al-Polyoxometalates: Experimental and DFT Study.

In this work, we fabricated a TiO 2 thin film, and the same film was modified with an Anderson aluminum polyoxometalate (TiO 2 -AlPOM). Physical-chemical characterization of the catalysts showed a significant change in morphological and optical properties of the TiO 2 thin films after surface modification. We applied the kinetic and isothermal models to the methylene blue (MB) adsorption process on both catalysts. The pseudo-second order model was the best fitting model for the kinetic results; qe (mg/g) was 11.9 for TiO 2 thin films and 14.6 for TiO 2 -AlPOM thin films, and k 2 (g mg -1 min -1 ) was 16.3 × 10 -2 for TiO 2 thin films and 28.2 × 10 -2 for TiO 2 -AlPOM thin films. Furthermore, the Freundlich model was suitable to describe the isothermal behavior of TiO 2 , K F (5.42 mg/g), and 1/ n (0.312). The kinetics of photocatalytic degradation was fitted using the Langmuir-Hinshelwood model; k ap was 7 × 10 -4 min -1 for TiO 2 and 13 × 10 -4 min -1 for TiO 2 -AlPOM. The comparative study showed that TiO 2 thin films reach a 19.6% MB degradation under UV irradiation and 9.1% MB adsorption, while the TiO 2 -AlPOM thin films reach a 32.6% MB degradation and 12.2% MB adsorption on their surface. The surface modification improves the morphological, optical, and photocatalytic properties of the thin films. Finally, the DFT study supports all the previously shown results.