Green synthesis of magnetite nanoparticles using Catha edulis plant leaf extract for removal of hexavalent Chromium from aqueous solution

In this study, we report the synthesis of magnetite (Fe3</sub>O4</sub>) 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 Fe3</sub>O4</sub> NPs was cubic face-centered with crystallite sizes of 12.1 nm, 14 nm, and 9 nm for metal to plant extract ratios of 1 : 1, 2 : 1, and 1 : 2  respectively. UV-Vis DRS analysis confirmed band gap energy of synthesized NPs was in the range 2.0-2.5 eV. Batch adsorption experiments were carried out to evaluate the effect of different parameters such as pH (3-10), adsorbent dose (250mg/L – 1250mg/L), initial concentration of adsorbate (20mg/L - 60mg/L), and contact time (30-120 min) on adsorption efficiency of the NPs at room temperature. The study revealed that the synthesized magnetite adsorbent exhibited  </sub>Cr (VI) removal efficiency of about 98.6% at optimized conditions of adsorbent dose of 1000 mg/L, pH 5, initial concentration of Cr(VI) 20 mg/L, and contact time of 60 min. The experimental data were best fitted to the Freundlich adsorption isotherm model (R2</sup> = 0.98341). Moreover, the mechanism of adsorption was in good agreement with pseudo 2nd</sup> order kinetics (R2 </sup>= 0.98188). The results suggested that the biosynthesized Fe3</sub>O4</sub> nanoparticles have the potential for the removal of hexavalent chromium ions from aqueous solutions.