Synthesis and Characterization of Sulfonated Magnetic Graphene-Based Cation Exchangers for the Removal of Methylene Blue from Aqueous Solutions

This article describes the synthesis, characterization, and performance of graphene-based magnetic cation exchangers as low-cost nanoadsorbers for the removal of methylene blue from aqueous solutions. The structure and surface morphology of the nanoadsorbers were characterized by X-ray diffraction, Fourier transform infrared, Raman, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, vibrating sample magnetometry, and thermogravimetric analysis. The effect of pH, incubation time, saturated adsorption capacities, and adsorption isotherms and kinetics on the adsorption of the sulfonated magnetic graphene oxide (SMGO) cation exchanger has been systematically studied. A comparative analysis of the samples was conducted with graphene oxide, sulfonated graphene oxide, and magnetic graphene oxide. Kinetic studies showed that adsorption followed a pseudo-second-order model, while the estimated maximum adsorption capacity using the Langmuir nonlinear isotherm was 246.47 mg g–1. Multiple regeneration and reuse experiments indicated that the SMGO performance remained above 80% after seven cycles of removal of cationic pollutants from aqueous solutions that could be applied to wastewater treatment