Efficient regeneration/reuse of graphene oxide as a nanoadsorbent for removing basic Red 46 from aqueous solutions

Abstract

The main purposes of this study were to synthesize graphene oxide (GO) nanoadsorbent, investigate the adsorption of Basic Red 46 (BR46), evaluate the isotherms and kinetics of the adsorption process, and study the regeneration/reuse of the GO in four cycles by microwave irradiation. First, the GO was synthesized using Hummers' method. Second, the adsorption process of BR46 as a cationic dye onto GO was studied. For this aim, four parameters including contact time, initial solution pH, adsorbent dose, and initial dye concentration were evaluated. The optimum values of the parameters were as follows: contact time = 30 min, initial solution pH = 11, adsorbent dose = 0.4 g/L, and initial dye concentration = 150 mg/L. Third, the adsorption process was well fitted to Langmuir equilibrium model (qm = 370.4 mg/L) and the pseudo-second order kinetic model. Finally, the GO were regenerated/reused in four cycles and their characteristics were studied by Brunauer, Emmett and Teller (BET), scanning electron microscopy (SEM), Fourier Transform-Infrared Spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. Furthermore, regeneration and step stripping efficiency of the GO were evaluated, indicating a downward trend in the adsorption capacity of the GO, but still a competitive nanoadsorbent for adsorption of synthetic dyes comparing to other studies.