Removal of Pb2+ Ions from Aqueous Solutions by Modified Magnetic Graphene Oxide: Adsorption Isotherms and Kinetics Studies

Graphene oxide based nano-composites have attracted huge attention for wastewater treatment specially removal of heavy metals. This paper reports adsorption of Pb2+ onto modified magnetic graphene oxide with chitosan and cysteine (GO/Fe3O4/Chi/Cys). To study the adsorbent morphology, Field Emission Scanning Electron Microscope (FE-SEM) and Fourier Transform Infrared Spectrometer (FTIR) were used in different stages of surface modification. In order to reveal the nature of sorption process, linear forms of different adsorption isotherms such as Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich were studied. Experimental data were fitted well by Langmuir model with a maximum monolayer coverage capacity (qmax) of 86.21mgg⁄. Prediction of qmax from Langmuir model was in good agreement with maximum empirical adsorption capacity (qexp=85.4mgg⁄). Various types of kinetic models such as pseudo-first-order, pseudo-second-order, Elovich, and intra particle diffusion were investigated to determine characteristic parameters in the adsorption process. The kinetic studies showed that pseudo-second-order model represents the adsorption process better than others due to its high correlation coefficient (R2=0.9996). Therefore, the adsorption process is chemisorption.