One-pot hydrothermal synthesis of hematite-reduced graphene oxide composites for efficient removal of malachite green from aqueous solution

Abstract

The facile one-pot synthetic route to prepare a 3D graphene composition of hematite (α-Fe₂O₃)–reduced graphene oxide (rGO) hybrid materials has been reported. The α-Fe₂O₃–rGO materials exhibit excellent capacity to remove malachite green (MG) from water. The pristine suspension of graphene oxide (GO) from the Hummers method mixed with FeCl₃ and urea in the solution, is in situ transformed into α-Fe₂O₃–rGO composites under hydrothermal conditions. The morphology and structure of the α-Fe₂O₃–rGO composites are characterized using transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoemission spectroscopy, Fourier transform-infrared spectroscopy, etc. It is found that α-Fe₂O₃ nanoparticles with cubic shapes and particles with the cubic side of 10–30 nm are uniformly distributed on the graphene layer. The application of α-Fe₂O₃–rGO materials for the removal of MG from the aqueous solutions is investigated. The Langmuir model is found to fit well with the experimental isotherm data, with a maximum adsorption capacity of 438.8 mg g⁻¹ for MG dye. The MG adsorption process is controlled by the pseudo-second-order rate model. The excellent capacity of α-Fe₂O₃–rGO to remove MG from water is ascribed to the synergetic adsorptive effect between α-Fe₂O₃ and rGO. The research provides an attractive adsorbent for removing the hazardous materials from wastewater.