Green sulfidated iron oxide nanocomposites for efficient removal of Malachite Green and Rhodamine B from aqueous solution.

A green and facile pathway was described using Viburnum odoratissimum leaf extract in the presence of sodium thiosulfate for the synthesis of sulfidated iron oxide nanocomposites (S-Fe NCs) adsorbents. The prepared S-Fe NCs can be used for the efficient removal of Malachite Green (MG) and Rhodamine B (RhB) from aqueous solution. Analytical techniques by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) were applied to understand the morphologies and compositions of S-Fe NCs. The stability of the adsorption capacity on S-Fe NCs was studied. Results from the characterization studies showed that S-Fe NCs were mainly composed of iron oxides, iron sulfides and biomolecules. The S-Fe NCs displayed high adsorption capacity for a wide range of pH values. The Koble-Corrigan isotherm model and Elovich model well described the adsorption process. The maximum adsorption capacity for MG and RhB was 4.31 mmol g-1 and 2.88 mmol g-1 at 303 K, respectively. The adsorption mechanism may be attributed to the electrostatic interaction, the hydrogen bonding, the π-π stacking interactions, the inner-sphere surface complexation or the cation bridging among the S-Fe NCs and dye molecules.