Synthesis of graphene oxide and its application for the adsorption of Pb⁺² from aqueous solution

Lead (Pb) ion is a heavy metal ion contaminant in geochemical systems, and has non-repairable harmful effects due to their high toxicity. They create severe threats to human health and ecological balance. Therefore, it is highly needed to remove Pb ions from contaminated water/aqueous media. In this study, graphene oxides (GOs) were prepared using “Hummers” and “improved” methods for studying the effect of processing parameters on the as-prepared GO. The processing parameters such as purification and drying process; and the effect of un-reacted graphite flakes (UGFs) on the thermal stability of GO were investigated. The as-prepared GOs were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and Raman spectroscopy. Further, we applied the as-prepared GO for the removal of Pb ions (Pb²⁺) from aqueous solution. The adsorption measurements were conducted through atomic absorption spectroscopy (AAS). The batch adsorption experiments were carried out to study the effect of initial concentration, contact time, and temperature on the adsorption of Pb²⁺ from aqueous solution onto the GO. It was found that the Pb²⁺ adsorption on GO increased with increase in the initial concentration of Pb²⁺. A maximum adsorption of 120 mg/g took place at initial concentration of 60 mg/L Pb²⁺. The adsorption studies recorded a relatively rapid uptake of Pb²⁺ by GO and followed pseudo-second-order kinetic model. The results indicated a significant potential of GO as an adsorbent for Pb²⁺ removal.