Study On The Adsorption Performance Of Graphene Oxide Based Hydrogels As Adsorbents For Uranium

With the continuous development of society economy, the increasingly serious energy and environment problems, the importance of alternative energy sources is emphasized by the increasing demand for a reduction in carbon emissions. Nuclear power is considered as a feasible solution to the global energy problem caused by exhaustion of fossil fuel. China is lack of uranium resources. The largest source of uranium in seawater has attracted increasing attention. In this work, graphene oxide based hydrogels as adsorbents for uranium were synthesized as adsorbents for recovery of uranium from nuclear waste and seawater, showing their potential application in nuclear fuel and mitigation of nuclear pollution.Interconnected 3D porous structure rGO hydrogel (rGH) and rGO/TiO2 hydrogel (GTH)were successfully synthesized by hydrothermal reduction. The results characterized by SEM,TEM, XRD and FT-IR illustrated that graphite oxide was reduced to the reduced graphite oxide under high temperature and high pressure, forming as-prepared rGH and GTH with porous structure. The uranium (Ⅵ) adsorption was analyzed as functions of the following parameters: solution pH value, temperature and contact time. The results show that hydrogen and hydroxyl ions have little effects to the adsorption of uranium by rGH and GTH when pH was ranging from 5 to 10; after combining with TiO2, the maximum adsorption capacity of GTH was larger than that of rGH. The adsorption process of rGH and GTH were both well fitted with pseudo-second-order kinetics. The experimental data followed Langmuir isotherms.The thermodynamic parameters of uranium (Ⅵ) adsorption onto rGH and GTH showed the process were endothermic and spontaneous in nature.A novel graphene oxide/amidoxime hydrogel was successfully synthesized by directly mixing the dispersions of both components via electrostatic assembly. IDAN containing multiple nitrogen and hydroxyl bound with the -COOH or -OH groups onto GO sheets by hydrogen-binding or acid-base-type electrostatic attraction, forming an assembly of GO nanosheets into hydrogels. The results characterized by SEM, TEM, XRD and BET illustrated that GAH has a 3D porous structure. The results characterized by FT-IR and XPS showed that GAH contained amino-oxime groups. Graphene oxide/amidoxime hydrogel (GAH) exhibits a promising adsorption performance for uranium from various aqueous solutions including simulated seawater. The adsorption process was well fitted with pseudo-second-order kinetics.The maximum sorption capacity was evaluated as 398.41 mg/g at pH 6.00 according to Langmuir isotherms. In the presence of high concentrations of competitive ions and simulated seawater with different concentrations of uranium (VI), GAH exhibited high affinity and selectivity for uranium (VI),showing potential for capturing uranium from seawater.