Highly efficient removal of ionic dyes in aqueous solutions using magnetic 3D reduced graphene oxide aerogel supported nano zero-valent iron

This study aims to develop three-dimension reduced graphene oxide aerogel supported nano zero-valent iron (rGOA-nZVI) by hydrothermal and liquid phase reduction approach and applies it to the removal of two typical dyes, methylene blue (MB) and methyl orange (MO) from aqueous solutions. The obtained magnetic rGOA-nZVI composites were characterized by scanning electron microscopy (SEM), atomic force microscopy, Brunauer-Emmett-Teller, X-ray diffraction and Fourier transform infrared spectroscopy, and its removal efficiencies for MB and MO from aqueous solutions were evaluated. The removal processes of MB and MO could be completed within 30 min, which were well described by the pseudo-second order kinetic model. The rGOA-nZVI nanocomposites exhibited remarkable performance for the removal of MB (the maximum adsorption amount, <i>q</i>_max = 3918 mg/g) and MO (<i>q</i>_max = 667 mg/g) in a wide pH range (pH 1.0-10.0). Furthermore, rGOA-nZVI is stable and recyclable with high dye removal efficiencies (> 90%) after five cycles. The removal mechanisms were demonstrated with SEM and XRD analyses before and after MB and MO removal. This study showed that rGOA acts as an excellent carrier for nZVI, and the rGOA-nZVI nanocomposites are efficient materials for the advanced treatment of dye wastewater over a wide pH range.