Department of Chemistry

URI for this collectionhttps://rps.wku.edu.et/handle/987654321/2335

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Green Synthesis of Fe-doped zinc oxide Nanoparticle for Removal of Methylene blue dye from Aqueous Solution
(Wolkite University, 2025-01-10) Wondimlebesku Delelegn Haile
In this study, Zinc oxide (ZnO) and iron-doped zinc oxide (Fe-doped ZnO) nanoparticles were synthesized using a green sol–gel method, utilizing Justicia Adhatoda plant leaf extract as a reducing agent. The aim was to investigate the potential of these nanoparticles as adsorbents for the removal of methylene blue dye, a toxic effluent commonly found in wastewater from textile industries. The synthesized materials were thoroughly characterized using various techniques: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and UV-visible (UV-VIS) spectroscopy. XRD analysis confirmed that both ZnO and Fe-doped ZnO nanoparticles exhibited a hexagonal wurtzite crystal structure, with good crystallinity and phase purity. The average particle sizes were found to be 24 nm for pure ZnO and 20 nm for Fe-doped ZnO, indicating that doping with iron slightly reduced the particle size. FT-IR analysis revealed key absorbance peaks corresponding to functional groups from the plant extract, confirming the involvement of the plant's organic compounds in the nanoparticle synthesis. The UV-VIS results showed a shift in the absorption spectra of Fe-doped ZnO nanoparticles, with the maximum absorption wavelength moving from the ultraviolet (UV) region to the visible range, indicating enhanced optical properties due to iron doping. The adsorption performance of the ZnO and Fe-doped ZnO nanoparticles was evaluated under various conditions. The optimum removal efficiency for ZnO nanoparticles was achieved at pH 9, with an adsorbent dose of 20 mg, a contact time of 45 minutes, and an initial dye concentration of 5 mg/L, resulting in a dye removal efficiency of 95.23%. For Fe-doped ZnO nanoparticles, the same conditions led to a higher removal efficiency of 99.52%. The adsorption kinetics followed the pseudo-second-order model, suggesting chemisorption as the primary mechanism of dye removal. Furthermore, the study demonstrated the recyclability of the synthesized nanocomposites, showing that they could be effectively used for more than five cycles without significant loss in efficiency. These findings suggest that the green-synthesized ZnO and Fe-doped ZnO nanoparticles are promising, eco-friendly adsorbent materials for wastewater treatment, particularly for removing hazardous dyes like methylene blue, and could be applied in sustainable, cyclic water purification processes.