High surface area and mesoporous graphene/activated carbon composite for adsorption of Pb(II) from wastewater

Since lead is a carcinogenic and non-biodegradable substance, its removal from water is of vital importance. Of all different removal pollutants techniques the adsorption is a promising method to remove Pb(II). The choice of adsorbent is a key factor to carry out this process efficiently. As already the adsorption of Pb(II) onto different porous materials have been studied, however the adsorption properties of graphene/activated carbon composite (GAC) to metal ions have not been reported yet. In this work, GAC was synthesized from graphene oxide and glucose. The samples were characterized by X-ray diffraction, Raman spectroscopy, SEM image and N2 adsorption–desorption isotherms. The GAC possessed high surface area (2012 m2/g), large pore volume (1.61 cm3/g) and mesopore structure. To study the adsorption behavior of Pb(II) on GAC, effects of solution pH, GAC dosage and stirring speed were examined. Afterwards the adsorption isotherms and kinetics of the GAC for removal of Pb(II) were studied by different models. The GAC was found to follow the pseudo-second order kinetic model better than the pseudo-first order. In addition it was understood that the intraparticle diffusion which studied by the Weber–Morris equation addressed the mechanism of the adsorption properly. Since the adsorption isotherm experimental data was fitted better by Langmuir model than Freundlich, the Pb(II) adsorption on the GAC is mainly homogeneous and monolayer. Finally, the maximum adsorption capacity of Pb(II) was measured up to 217 mg/g, which is higher than many other adsorbents.