Coagulation of aqueous graphene oxides in presence of metal cations.

With the extensive use of graphene oxide (GO) in research and application, the negative impact of water-soluble graphene oxide on the environment has to be considered. It is significant to find a suitable method to remove GO from water. In this study, sulfates were used as the coagulants for GO removal. The experimental results showed that cations as Mg²⁺, Al³⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Mn²⁺ interacted with GO and GO would agglomerate then. However, low-concentration Na⁺, K⁺ and SO₄^2– did not show any coagulation capacity. The temperature, equilibrium time and the initial concentration of cations and GO would affect the coagulation capacities. Among the selected sulfates, aluminum sulfate, calcium sulfate and copper sulfate had higher coagulation capacities, which were 4,772; 1,149 and 1,451 mg/g, respectively. In addition, the metallic cations mentioned were easy to obtain, so they were promising coagulants for the elimination of GO from water. [ABSTRACT FROM AUTHOR]