Graphene Oxide Sorption Capacity toward Elements over the Whole Periodic Table: A Comparative Study

Water pollution is a worldwide environmental problem. Wastewater from industrial processes, surface and ground waters can all contain various metal ions, such as toxic Hg²⁺, Pb²⁺, Cd²⁺, Cu²⁺, As³⁺, Sb³⁺, Bi³⁺, and so on. Consequently, efficient methods for removing impurities from such waters are in high demand. Since the large surface area of graphene oxide can make this material suitable for the uptake of various metal ions, we investigated its sorption capacity. The detail knowledge of sorption for various ions on graphene oxide surface is also crucial for graphene doping and purification. The surface sorption allowed synthesis of materials for catalysis with homogeneous distribution of catalytic active sites. The Hummers and Hoffman's (permanganate and chlorate) methods were used to prepare two graphene oxides with different surface chemistry for investigation of sorption capacity across most of the ions within the periodic table. The sorption capacity was evaluated by XRF and ICP-OES, XPS, XRD, and SEM-EDS. Both Hummers and Hoffman's graphene oxides showed significant differences in sorption capacity toward various ions. For the majority of tested metal ions, our results showed that the Hummers graphene oxide had much higher sorption capacity than Hoffman's graphene oxide. Several trends within sorption capacity across the periodic table can be observed indicating a strong influence of ion electronic structure and coordination ability as well as its acidity and redox properties on its sorption on graphene oxide surface.