Echinops kebericho Aqueous Root Extract Assisted Green Synthesis of Zinc Oxide Nanoparticles for Photocatalytic Degradation of Methylene Blue

Wastewater treatment from industrial effluents is a global problem. Searching for environmentally safe and green technology is in the utmost interest of the scientific community. Especially organic pollutants, due to their difficulty to biodegrade, have posed a problem to human health and the aquatic environment. Hence, we reported plant extract-mediated synthesis of zinc oxide nanoparticles (ZnO NPs) in this study for photocatalytic degradation of methylene blue (MB) under sunlight irradiation. Echinops kebericho root extract was used as a reducing and stabilizing agent during the synthesis of ZnO NPs. The presence of phenolics, tannins, flavonoids, terpenoids, and alkaloids was qualitatively confirmed in the aqueous root extract of the plant under study. These secondary metabolites have a high potential in facilitating capping and stabilizing effects on the formation of ZnO nanostructures. Powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the crystal structure and chemical bond of ZnO NPs, respectively. The XRD patterns showed the formation of pure phase hexagonal wurtzite ZnO NPs with an average crystal size of 14.67 nm. The photocatalytic degradation efficiency of ZnO NPs (80 mg) to remove 10 mg/L of MB dye was found to be 92.2% at pH=10 and 120 min contact time under direct sunlight irradiation. Therefore, ZnO NPs synthesized using E.kebericho were potential photocatalysts for the degradation of MB from wastewater for at least three cycles.