The highly efficient adsorption of Pb(II) on graphene oxides: A process combined by batch experiments and modeling techniques

In this study, graphene oxide (GO) was synthesized and characterized by SEM, TEM, XPS, FTIR spectra, Raman and Zeta potential. The characterization results showed that GO displayed a variety of oxygen containing functional groups such as hydroxyl, epoxy, carbonyl and carboxyl groups. The adsorption of Pb(II) on GO was investigated by batch and modeling techniques. The adsorption kinetics indicated that the adsorption of Pb(II) on GO can be fitted by a pseudo-second-order kinetic model very well. The adsorption process of Pb(II) on GO was independent of ionic strength at a wide pH range from 2.0 to 11.0, revealing that inner-sphere surface complexation dominated the Pb(II) adsorption on GO at pH 2.0-11.0. The maximum adsorption capacity of GO for Pb(II) calculated from Langmuir model was 125.0 mg/g at pH 5.5 and 298 K. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption of Pb(II) on GO was an endothermic and spontaneous process. The pH-dependent and isothermal adsorption data of Pb(II) on GO can be satisfactorily fitted by surface complexation modeling with mononuclear and monodentate complexes (SOPb+ species) and binuclear and bidentate complexes ((SO)2Pb2(OH)3− species). Given the high adsorption performance of GO, it should display potential application in water purification.