Fabrication of magnetic graphene oxide nanocomposites functionalized with a novel chelating ligand for the removal of Cr(VI): Modeling, optimization, and adsorption studies

In this study, the performance of magnetic graphene oxide (GO-Fe3O4) functionalized with 2-mercaptobenzothiazole (MBT) chelating ligand was investigated as a new adsorbent for the adsorption of Cr(VI) from aqueous solutions. The magnetic graphene oxide functionalized with chelating ligand of the 2-mercaptobenzothiazole (GFM) was freshly synthesized via a two-stage process, and characterized by energy dispersive X-ray (EDAX), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM) images and thermogravimetric analysis (TGA). The composition effect of independent input factors and one dependent output response was investigated using a central composite design under response surface methodology (RSM). The full second-order model indicated a model well-fitted with the experimental data. The optimum operating points giving maximum Cr(VI) removal (94.02) included pH, 6.79; adsorbent dosage, 2.98 g L-1; contact time, 118.6 min; and Cr(VI) concentration, 4.41 mg L-1. Based on the reported results, magnetic graphene oxide functionalized with 2-mercaptobenzothiazole (GFM) chelating ligand indicated best fit with the Langmuir model. The kinetic models followed the pseudo-first-order model. The thermodynamic studies indicated that the sorption of Cr(VI) onto GFM was endothermic and spontaneous.