Manganese-Tunable p-type ZnO Nanoscale for Optimized Photocatalytic Degradation of Terasil Blue from Wastewater

Abstract

Introduction: The present study aimed to investigate the structural, morphological, elemental, optical properties and photocatalytic activity of the bare zinc oxide (ZnO) and Manganese-doped zinc oxide (Mn- ZnO) nanoparticles (NPs) using terasil blue (TB) dye as a model substrate. Materials and Methods: The ZnO and Mn-doped ZnO catalysts were synthesized using the co-precipitation method. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The band energies were measured using ultraviolet-visible (UV-Vis) spectrophotometry. Results: The results obtained from XRD, EDX, SEM, and UV-Vis analyses demonstrated a successful synthesis of bare and Mn-doped ZnO nanoparticles. The diffraction patterns for the synthesized ZnO and Mn-doped ZnO photocatalyts were matched with that of the standard hexagonal wurtzite structure of the standard ZnO catalyst. The average particle size for the ZnO and Mn-doped ZnO catalysts were found to be 23.46 nm and 24.38 nm, and band gap energies of 3.28eV and 3.09eV, respectively. The photocatalytic performance of the Mn-doped ZnO photocatalyst was optimized using box behnken design of response surface methodology under visible light irradiation. The operational parameters involved TB initial concentration, catalyst dosage, initial pH, and irradiation time. The optimum photodegradation efficiency of TB dye removal was achieved at 96.75% of 15mg/L of TB concentration, 0.1g/L of Mn-doped ZnO, pH = 10, and 160 minutes of irradiation time. Moreover the photocatalytic degradation of TB over the Mn-doped ZnO nanoparticles followed the pseudo-first-order kinetics model (k = 0.0254 min-1). Conclusion: Finally, the evaluation of various scavengers confirmed that the photogenerated holes and hydroxyl radicals were the major radicals for the TB photodegradation over the Mn-doped ZnO nanoparticle under visible light irradiation.