Textural, structural and morphological evolution of mesoporous 3D graphene saturated with methyl orange dye during thermal regeneration

Abstract

This work aims to evaluate the performance of 3D graphene as the reusable adsorbent of synthetic dyes. For this, the behavior of 3D graphene samples in the adsorption of methyl orange (MO) dye from aqueous solutions as well as the thermal regeneration of the 3D graphene saturated with dye at various temperatures of 300–700 °C was studied. The 3D graphene before and after being thermally regenerated was characterized by various techniques including electron microscopy, thermal analysis, nitrogen adsorption, X-ray diffraction (XRD) and Raman spectroscopy. A simple heat treatment process was employed as a low cost and fast regeneration strategy, resulting in efficient recovery of the 3D graphene, with a remarkable structural and morphological stability over the whole adsorption and thermal regeneration process. Thermal regeneration proved to be an efficient process to remove the MO content adsorbed on the exhausted 3D graphene, providing an adsorption capacity equals to 77–94% of the original 3D graphene for the samples regenerated at different temperatures. The decomposition of MO was further investigated by thermal analysis and liquid chromatography- mass spectrometry demonstrating that the dye is decomposed below 300 °C, leaving inorganic salts behind.