Gudisa Chala - Department of Applied Chemistry, School of Applied Natural Science, Adama Science and Technology University, P. O. Box ۱۸۸۸, Adama, Ethiopia.
Tegene Zeleke - Department of Applied Chemistry, School of Applied Natural Science, Adama Science and Technology University, P. O. Box ۱۸۸۸, Adama, Ethiopia.

In this study, we report the synthesis of magnetite (Fe۳O۴) nanoparticles using Catha Edulis plant leaf extract as bioreducing agents and investigation of its efficiency as an adsorbent for hexavalent chromium Cr(VI) removal from aqueous solutions. The synthesized NPs were characterized using X-ray diffraction (XRD) spectroscopy, Fourier Transforms Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Ultraviolet-visible (UV-Vis) spectroscopy, and thermal analysis (TGA-DTA). The XRD result revealed that the phase structure of Fe۳O۴ NPs was cubic face-centered with crystallite sizes of ۱۲.۱ nm, ۱۴ nm, and ۹ nm for metal to plant extract ratios of ۱ : ۱, ۲ : ۱, and ۱ : ۲  respectively. UV-Vis DRS analysis confirmed band gap energy of synthesized NPs was in the range ۲.۰-۲.۵ eV. Batch adsorption experiments were carried out to evaluate the effect of different parameters such as pH (۳-۱۰), adsorbent dose (۲۵۰mg/L – ۱۲۵۰mg/L), initial concentration of adsorbate (۲۰mg/L - ۶۰mg/L), and contact time (۳۰-۱۲۰ min) on adsorption efficiency of the NPs at room temperature. The study revealed that the synthesized magnetite adsorbent exhibited  Cr (VI) removal efficiency of about ۹۸.۶% at optimized conditions of adsorbent dose of ۱۰۰۰ mg/L, pH ۵, initial concentration of Cr(VI) ۲۰ mg/L, and contact time of ۶۰ min. The experimental data were best fitted to the Freundlich adsorption isotherm model (R۲ = ۰.۹۸۳۴۱). Moreover, the mechanism of adsorption was in good agreement with pseudo ۲nd order kinetics (R۲ = ۰.۹۸۱۸۸). The results suggested that the biosynthesized Fe۳O۴ nanoparticles have the potential for the removal of hexavalent chromium ions from aqueous solutions.

Adsorption Isotherm, Antibacterial activity, Catha Edulis, Green synthesis, Magnetite NPs