Preparation of Graphene <i>via</i> Thermal Reduction and Its Adsorption Capacity for Heavy Metal Pb²⁺

Abstract

Graphene(GR) was obtained by reduced graphite oxide(GO) by instantaneous heating. Thermal reduced graphene was used to adsorb heavy metal Pb2+ ions in water to study the effect of adsorption time and pH value on the adsorption. The results show that the pH value greatly affects the adsorption capacity of graphene. When pH value is higher than 7, the adsorption capacity obviously increases. And the equilibrium reaches within five minutes. The analysis by scanning electron microscope (SEM) and transmission electron microscope (TEM) shows that graphene flake is very thin and with less layers. Experimental data are fitted by Langmuir and Freundlich adsorption isotherms model. According to the Langmuir adsorption isotherms model, the maximum theoretical adsorption capacity of Pb2+ is 86.5mg/g, the correlation coefficient R2 is 0.9982, and Langmuir constant KL is equal to 10.7. The Langmuir model agrees well with experimental data. It demonstrates that the adsorption reaction is a fast single molecular layer chemical process. The adsorption kinetics is better fitted to the pseudo-second-order kinetic model.

Keywords

• thermal reduction
• graphene
• adsorption capacity
• heavy metal Pb²⁺