Enhanced solar photodegradation of reactive blue dye using synthesized codoped ZnO and TiO2

Abstract

The rapidly growing textile industry produces various textiles, which has led to significant water pollution due to the discharge of dyes and chemicals. In this study, TiO2 doped ZnO photocatalyst was synthesized and characterized to determine the morphology and composition (scanning electron microscopy, SEM&EDX), optical properties (ultraviolet–visible diffuse reflectance spectroscopy, UV DRS), functional groups (Fourier Transform Infrared spectroscopy), and crystal structure (X-ray diffraction). The photocatalysts were used to photodegrade reactive blue dye in aqueous solution (1–3 mg/L) under natural sunlight. The SEM showed agglomerated granular particles, with increased agglomeration and smaller particle size for lab-synthesized TiO2 (TZT) compared to commercial TiO2 (TZC). The EDX results confirmed the presence of only Ti, Zn, and O in both photocatalysts, signifying the presence of ZnO and TiO2 and the absence of contamination. The UV DRS revealed a reduction in band gap from 3.6eV (ultraviolet light region) to 3.02eV (visible light region). At a dye concentration of 1 mg/L, 0.03 mg of photocatalyst, and a pH of 5, under sunlight, the degradation efficiencies were 86.9% for ZnO, 91% for TZC, and 100% for TZT. The rate constants (k) were 0.01203, 0.01511, and 0.08261 min-1 for bare TiO2, TZC, and TZT, respectively. The photocatalysts were recovered and reused over five consecutive cycles without significant reduction in performance, thus confirming the stability and durability of the TiO2-ZnO photocatalysts (TZT and TZC). The lab-synthesized photocatalysts demonstrated superior performance (100% degradation) and the utilization of natural sunlight which is green energy contributes to a clean and sustainable environment.