Synthesis of Graphene Oxide and Functionalized Graphene Oxide Using Improved Hummers Method for the Adsorption of Lead from Aqueous Solutions

One of the most important environmental challenges in the world is environmental pollution with toxic and dangerous heavy metals, which causes various environmental effects. Lead is a heavy metal that can be removed in a variety of methods. In this study, graphene oxide adsorbent was prepared by modified Hummers method and functionalized with aminomethyl phosphonic acid and its application for the adsorption of lead ions from aqueous solutions in a batch sorption process was investigated. The effect of several batch adsorption parameters such as contact time, pH, adsorbent dose, initial concentration and temperature were investigated. The kinetic data were analyzed by Pseudo-first-order, Pseudo-second-order and Double- exponential kinetic models. The results showed that experimental data was fitted well by Pseudo-second-order kinetic model. The Freundlich and Langmuir isotherm models were applied to describe the equilibrium data. The maximum adsorption capacity of lead ions with graphene oxide and functionalized-graphene oxide adsorbents was found to be 187.80 and 209.41 mg/g at a pH of 2.0 and temperature of 45 ºC, respectively. Furthermore, the graphene oxide and functionalized-graphene oxide adsorbents were regenerated by HCl/HNO3 solution and the adsorption capacity did not change remarkably after seven adsorption-desorption cycles.