Green Synthesis of ZnO Materials and Investigation of Methylene Blue Degradation under Ultraviolet Light

Abstract

Toxic dyes represent a critical environmental issue that requires effective treatment due to their direct and indirect impacts on human health. In this experimental study, ZnO nanomaterials were successfully synthesized via a green approach, and several influencing parameters - including stirring temperature, calcination temperature, and calcination time - were systematically investigated, resulting in superior degradation efficiency toward Methylene blue (MB) and the establishment of an optimized synthesis procedure. The phase structure and material properties of ZnO were characterized using X - ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and UV-Vis light absorption analysis in photocatalytic processes, providing information on particle size, crystalline phase, optical band gap energy, and photocatalytic performance. The results show that the studied parameters significantly affect the characteristics and photocatalytic efficiency of ZnO. Specifically, they show that the ZnO nanomaterials had an average crystal size ranging from 35-40 nm. The ZnO sample at 450 °C showed relatively uniform spherical particles with high porosity, evenly dispersed on the material surface. The band gap energies of the material ranged from 3.19-3.26 eV, which was lower than the Eg of typical ZnO (3.37 eV). The photocatalytic efficiency of MB degradation achieved by the material calcined at high temperatures from 450–700 °C was higher than that of ZnO material calcined at low temperatures. The highest photocatalytic efficiency of MB degradation was achieved by the ZnO sample calcined at 450 °C, reaching 80.85% after 90 minutes under UV-Vis light irradiation, with the highest degradation rate constant of 0.0187 min⁻¹.