Synthesis and Characterization of Bi2O3-SnO2 Type-II Heterojunction Nanostructure with Tunable Band Edge Modulation for Enhanced Visible-Light-Driven Photocatalytic Water Purification

Abstract

In this study, wastewater tainted with dyes presents a significant environmental problem that calls for effective and reusable photocatalysts to remove pollutants under visible light. The purpose of this work is to create and describe a BiO₃–SnO₂ heterojunction nanocomposite for the photocatalytic degradation of Rhodamine B (RhB) and Methyl Orange (MO). This work is interesting since it evaluates the composite's degradation performance toward two distinct dyes in addition to the impacts of catalyst dose and starting dye concentration, reaction kinetics, reactive species, and reusability. The BiO₃–SnO₂ system's potential for visible light-assisted dye removal and its appropriateness for additional wastewater treatment research are both shown by this comprehensive study. XRD, FTIR, UV–Vis spectroscopy, FE-SEM, EDX, and TGA were used to characterize the nanocomposite, which was created utilizing solution-phase precipitation and a wet-chemical sol-gel approach. The optical band gap was determined to be 2.55 eV, and FTIR showed distinctive Bi–O and Sn–O vibrations at 620 and 540 cm⁻¹, respectively. Bi, Sn, and O contents of 18.5, 60.5, and 21.0 weight percent, respectively, were verified by EDX. At an ideal catalyst dose of 0.75 g/L, the composite under visible light irradiation achieved 94% RhB degradation and 88% MO degradation in 120 minutes. Scavenger studies revealed the significant contribution of hydroxyl radicals (•OH), and the degradation followed pseudo-first-order kinetics. The composite maintained a claimed degradation efficiency of 87.1% after five reuse cycles. These results highlight the potential of BiO₃–SnO₂ nanocomposite as a reusable photocatalyst for the treatment of wastewater polluted with dyes using visible light.