Highly efficient removal of Pb(II) ion from aqueous phase using surface-modified graphene: equilibrium and kinetic study

A novel surface-modified graphene (SMG) was employed as an adsorbent for the removal of Pb(II) from aqueous solution at room temperature (295 +/- 5 K). The SMG was prepared from graphene (G) via oxidation method using concentrated nitric acid. scanning electron microscopy, thermogravimetric analysis, Brunauer, Emmett, and Teller, and Fourier transform infrared spectroscopy were used to characterize the produced adsorbent. Batch adsorption experiments were carried out under different operating conditions; pH (2-7), adsorbent dosage (4-32 mg), and contact time (5-240 min). The maximum Pb(II) adsorption was obtained at a pH of 6, adsorbent dose of 20 mg after 100 min at 298 K. Surface of the SMG had more oxygen functionalities and higher surface area compared with the G, thereby resulting in enhanced removal of Pb(II), significantly. Pseudo-second-order kinetic model fitted the results better than pseudo-first-order and intra-particle diffusion models. Redlich-Peterson, Freundlich, and Langmuir isotherm models fitted very well the equilibrium results. The SMG was a superior adsorbent for Pb(II) with a maximum adsorption capacity of 140 mg/g. Therefore, it can be concluded that SMG can be effectively used to remove heavy metals from waste and domestic water.