SnO2-BiVO4 mixed catalyst: Characterization and kinetics study of the photodegradation of phenazopyridine

Abstract

Abstract In this work, SnO2 and BiVO4 nanoparticles (NPs) were synthesized hydrothermally and coupled mechanically (SB sample). The samples were briefly characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. A nano dimension was obtained for the coupled SB sample from the PXRD and SEM results. The EDX analysis results agreed with the SnO2:BiVO4 mole ratio of 1:3 in the coupled system. This coupling enhanced the absorption properties of SnO2 and decreased the PL intensity. The coupled catalyst showed a boosted photocatalytic activity towards phenazopyridine (PZP) in an aqueous solution concerning the single components. The photocatalytic activity depended on the change in the SnO2:BiVO4 mole ratio and the best efficiency was achieved for the 1:3 value Higher PZP degradation extent was achieved in SB dose of 0. 5 g L−1, C PZP of 10 ppm at pH 7.2, and the irradiation time of 60 min. The PZP photodegradation kinetics obeyed the Hinshelwood model for apparent first-order kinetics with a k-value of 6.28 × 10−3 min−1 (a t 1∕2 -value of 110.4 min). A k-value of 6.91 × 10−3 min − 1 ( t 1∕2 -value of 110.3 min) was also obtained when the photodegraded solutions were subjected to the COD experiment. The HPLC analysis confirmed that about 90% of PZP molecules were degraded during the applied conditions. The SB catalyst also retained about 83% of its initial photocatalytic activity after three successive runs.