Folding/aggregation of graphene oxide and its application in Cu2+ removal.

Graphene oxide (GO) can be aggregated by Cu(2+) in aqueous solution with a huge Cu(2+) absorption capacity. The Cu(2+) causes GO sheets to be folded and also to form large aggregates that were characterized by confocal microscopy and atomic force microscopy. The folding/aggregation is most likely triggered by the coordination between GO and Cu(2+). The equilibrium Cu(2+) concentrations and equilibrium absorption capacity of GO were measured to estimate the maximum absorption capacity of GO for Cu(2+) and the absorption model. GO has a huge absorption capacity for Cu(2+), which is around 10 times of that of active carbon. Representative results are presented and the implication to Cu(2+) removal is discussed.