Enhanced Photocatalytic Degradation of Methyl Red Dye with Bismuth-Doped ZnO: Kinetics, Mechanistic and Re-cyclability Aspects

Abstract

This study highlights the synthesis and characterization of bismuth-doped zinc oxide (Bi-ZnO) through sol-gel methodology. The synthesized catalyst was characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Ultraviolet-Visible spectroscopy (UV/Vis). Later on, it was employed for the photocatalytic degradation of methyl red dye (MR) in simulated water samples. The XRD spectra showed that it possesses hexagonal wurtzite structure. FTIR results revealed alterations in vibrational frequencies at 1450, 2350 and 3400 cm^-1, SEM analysis indicated slab-like morphology with distinct edges and faces. The smaller particles have rod-like morphology with irregular shapes and sizes. The mean particle size was found to be 45.0 ± 3.1 nm. The multi-point BET surface area was found to be 4.68 m²/g while the pore size was found to be 205.923 nm. Maximum dye degradation, at 200 ppm dye concentration, 400 mg catalyst dose, pH 4, 30 °C after 60 min, was found to be 63% which increased to 95% upon the addition of K₂S₂O₈ and H₂O₂ to the reaction mixture. The degradation of MR followed pseudo-first-order-kinetics. R² value was found to be 0.93266. The value of k₁ was found to be 3.46 × 10^-3 min^-1. These findings indicates that Bi-ZnO is an effective photocatalyst for the degradation of MR.

Keywords: Bi-ZnO; K2S2O8 and H2O2; Methyl red dye; Photocatalytic degradation.