Optimization of Fe3O4 nanoparticles loading on reduced graphene oxide nanosheets for the efficient removal of aqueous p-nitroaniline and Cr(VI)

Title : Optimization of Fe3O4 nanoparticles loading on reduced graphene oxide nanosheets for the efficient removal of aqueous p-nitroaniline and Cr(VI)

Abstract:

Herein, we demonstrate the hydrothermal synthesis of a Fe₃O₄ /RGO nanocomposite with an optimized Fe₃O₄ loading of 27% for the adsorptive removal of 4-nitroaniline (4-NA) and Cr(VI) from wastewater. X-Ray Diffraction and Raman analysis confirm the formation of inverse spinel Fe₃O₄ nanocrystals. FESEM and TEM imaging display quasi-homogeneous dispersion of Fe₃O₄ nanoparticles (average crystallite size=10.67 nm) anchored onto the surface of RGO nanosheets. BET analysis confirms the existence of microporous networks in the nanomaterial. Notably, the material possesses a high specific surface area (192.8 m²/g), which facilitates adsorption of toxic pollutants. Goniometry verified the hydrophilicity of the composite (left and right contact angles are determined to be 10.9° and 11.2°, respectively). The adsorption kinetics are determined based on batch adsorption experiments, conducted with a fixed adsorbent dosage of 0.25 g/L at 30°C. Adsorption equilibrium for 4-NA and Cr(VI) systems are achieved in 4 h and 6.5 h respectively, following pseudo-second-order kinetics. The nanocomposite demonstrates an excellent maximum adsorption capacity of 264.21 mg/g for 4-NA and 324.56 mg/g for Cr(VI) at pH=2 and 303 K. XPS analysis of the spent samples suggest that the adsorption of 4-NA is predominantly physical and is governed by an extensive electrostatic attraction and π-π interactions between 4-NA molecules and the RGO moiety. Mechanistically, adsorption of Cr(VI) is primarily achieved through chemical routes, viz-a-viz chelation, and partial reduction to Cr(III) catalyzed by nanocrystalline Fe₃O₄. Room temperature magnetization plot (M-H curve) shows that the material possesses a saturation magnetization of 18.4 emu/g, which facilitates rapid and efficient separation of the adsorbent from aqueous solution post adsorption using an external magnet. The optimized nanocomposite is found to be chemically and morphologically stable for reuse up to 4 cycles for both 4-NA and Cr(VI) without any significant loss of adsorption capacity or leaching of iron above its maximum permissible limit in potable water.

Keywords: p-Nitroaniline; Chromium; Reduced Graphene Oxide; Magnetite; Adsorption; Regeneration

Biography:

Mr. Sourav Halder studied Chemical Engineering at Indian Institute of Technology, Kharagpur, India and graduated Bachelors and Masters in Chemical Engineering in 2021. He then joined the research group of Dr. Bhaskar Bhaduri at IIT Kharagpur in the same year. He is currently undertaking his PhD degree under Dr. Bhaduri’s supervision. He has published 2 research articles in SCI (E) journals.