Abstract
In this paper a comparative study on adsorption behavior of methyl blue, a mutagenic anionic dye molecule onto magnetic Fe3O4 nanopowder and reduced graphene oxide (rGO)–Fe3O4 nanocomposites was carried out. Both the nanomaterials were synthesized by facile method and characterized by X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM) analysis. rGO–Fe3O4 nanocomposite shows maximum adsorption capacity with 75.15mmol/g for methyl blue dye molecule which is higher than compared to Fe3O4 nanopowder (61.459mmol/g). The kinetics of adsorption were studied at pH 5 and four different temperatures namely 18, 25, 30 and 35°C. The kinetic data were analyzed with six different kinetic models and pseudo second-order (linear) kinetic model was found to be the best fit model for our adsorption experiment. In order to investigate the nature of electrostatic interaction of the dye molecule with both the adsorbent materials, adsorption isotherm experiments were carried out at pH 5 and 25°C. The thermodynamic parameters, including Gibbs free energy (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were calculated for the adsorption process. The reusability of the both the adsorbents were also established and found that rGO–Fe3O4 nanocomposites shows better reusability with 81.43% dye adsorption in 3rd cycle than that of Fe3O4 nanopowder (49.3%). The dissolution of Fe from the both adsorbent in water was also investigated at different pH of the medium. The mechanism of adsorption process was studied by DRIFT spectroscopy which indicates electrostatic interaction between the dye molecule and the adsorbent materials.
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