Nanoscale Zerovalent Iron Grafted with Graphene Oxide: A Dye Adsorption Study

Abstract

Methylene blue (MB) removal from aqueous solutions were studied using nanoscale zero valent iron/graphene oxide (nZVI/GO) composites, which were synthesized. Nanoscale zero valent iron (nZVI) and graphene oxide (GO) were used for comparison. It was followed by Fourier-transform infrared spectroscopy (FTIR) analysis and followed by Scanning electron microscope analysis (SEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis for sample characterization. The variable in this case included the initial concentration of MB, which was varied from 200, 250, and 300 mg/L and the contact time, which was varied between 0–90 min. The pH and mass of adsorbent was kept constant at 7 and 0.5 g respectively. Outcomes were indicative that the highest removal of MB was at 92.75% for nZVI/GO composite at 200 mg/L of MB. The experimental data was fitted on to the Langmuir, Freundlich and BET adsorption isotherm models which gave R² > 0.95. This can be attributed to high favorability of adsorption taking place in many layers. The nZVI/GO adsorbent would follow the pseudo-first-order kinetic model showing an R² value of 0.99, 0.94, and 0.93 for from 200, 250, and 300 mg/L of MB, respectively. Furthermore, Boyd's external diffusion equation model was applied to calculate the external diffusion. The finding indicated high external diffusion with R² > 0.99. The results from this paper are attributed to the simplistic generation of nZVI/GO composite and its effect on the removal of MB from aqueous solution. The significance of this study would be that nZVI/GO composites have been only recently being experimented for dye removal and are proving to be an extremely efficient form of adsorption according to recent studies.