UV/visible-light photocatalytic degradation of organic dyes using ZnO nanomaterials

Abstract

In this study, ZnO nanomaterials were synthesised via a hydrothermal method and characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM)/high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), analysis and diffuse reflectance spectroscopy (DRS). The obtained ZnO exhibited a wurtzite structure, high crystallinity, mesoporosity, a large specific surface area of 107.17 m²/g, and a band gap of 3.19 eV. Photocatalytic performance was comparatively evaluated under visible and UV irradiation using methylene blue (MB) and Rhodamine B (RhB) as model dyes. ZnO achieved >90-98% degradation, with consistently faster kinetics under UV irradiation and MB degrading faster than RhB. Pseudo-first-order fits yielded k(MB)=0.027 min^-¹ (Vis) vs 0.076 min^-¹ (UV) and k(RhB)=0.024 min^-¹ (Vis) vs 0.066 min^-¹ (UV), linking structureproperty features to light-dependent activity. These results establish a clear UV/Vis comparison and underscore the applicability of hydrothermal ZnO for wastewater treatment under practical illumination.