Preconcentration of U(vi) ions on few-layered graphene oxide nanosheets from aqueous solutions (vol 41, pg 6182, 2012)

Graphene oxide nanosheets have attracted multidisciplinary attention due to their unique physicochemicalproperties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using amodified Hummers method and were characterized by TEM, AFM, Raman spectroscopy, XPS, FTIRspectroscopy, TG–DTA and acid–base titrations. The prepared few-layered graphene oxide nanosheetswere used as adsorbents for the preconcentration of U(VI) ions from large volumes of aqueous solutions asa function of pH, ionic strength and temperature. The sorption of U(VI) ions on the graphene oxidenanosheets was strongly dependent on pH and independent of the ionic strength, indicating that thesorption was mainly dominated by inner-sphere surface complexation rather than by outer-sphere surfacecomplexation or ion exchange. The abundant oxygen-containing functional groups on the surfaces of thegraphene oxide nanosheets played an important role in U(VI) sorption. The sorption of U(VI) on grapheneoxide nanosheets increased with an increase in temperature and the thermodynamic parameters calculatedfrom the temperature-dependent sorption isotherms suggested that the sorption of U(VI) on grapheneoxide nanosheets was an endothermic and spontaneous process. The maximum sorption capacities (Qmax)of U(VI) at pH 5.0 ± 0.1 and T = 20 °C was 97.5 mg g−1, which was much higher than any of thecurrently reported nanomaterials. The graphene oxide nanosheets may be suitable materials for theremoval and preconcentration of U(VI) ions from large volumes of aqueous solutions, for example, U(VI)polluted wastewater, if they can be synthesized in a cost-effective manner on a large scale in the future.