Enhanced adsorption of cadmium ions by 3D sulfonated reduced graphene oxide

A novel adsorbent 3D sulfonated reduced graphene oxide (3D-SRGO) aerogel with porous structure, large surface area, excellent hydrophilicity and high adsorption capacity was developed for cadmium Cd(II) ions removal from water. Kinetic data reveal that the cadmium adsorption was rapid in the beginning followed by a slower adsorption process, nearly 93% adsorption can be achieved within 20 min. The cadmium adsorption isotherm was well described by the pseudo second-order kinetic model. The calculated adsorption capacity of this adsorbent for cadmium by Langmuir model was 234.8 mg/g at pH 6.0. The thermodynamic parameters indicated that the adsorption reaction of Cd(II) ions on the 3D-SRGO was a spontaneous process. XPS and Ft-IR analyses reveal cation exchange process was an important mechanism for cadmium removal by the 3D-SRGO. Filtration experiments revealed that the membranes fabricated by 3D-SRGO could quickly remove Cd(II) ions from the aqueous solutions. Regeneration tests showed that HNO3 solution at pH = 0.3 can desorb 97.23% cadmium from the cadmium ion-loaded 3D-SRGO. Findings of this study demonstrate the potential utility of the 3D-SRGO as a very effective adsorbent for cadmium removal from contaminated water. (C) 2014 Published by Elsevier B.V.