Synthesis and Characterization of Graphene Oxide/Hydrogel Composites and Their Applications to Adsorptive Removal Congo Red from Aqueous Solution

Abstract

Graphene oxide / (polyvinylpyrrolidone / acrylic acid) composite GO/ (PVP-AAc) was studied as adsorbent for the Congo red dye. The synthesized composites hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR). The process of adsorption of the Congo red (CR) dye on the surface of the GO/ (PVP-AAc) composite has reached equilibrium state within 60 minutes. The rate of adsorption of the dye on the surface was good due to the high surface area characteristic of the surface of the composite. The adsorption kinetics of the dye on the surface of the composite GO/ (PVP-AAc) were studied using of pseudo-first order model and pseudo-second order model. The results indicated that the adsorption process follows the pseudo-second order model. The effects of temperature, ionic strength and pH were also studied. In order to determine the maximum adsorption, the linear forms of isotherm of adsorption were studied, Langmuir, Freundlich, and Temkin equations. Also were studied the thermodynamic functions of the process of adsorption of, Gibbs free energy (ΔG), Entropy (ΔS), and Enthalpy (ΔH).