Application Of 3D Graphene-based Macroscopic In Radionuclide Separation And Enrichment From Aqueous Solutions

Domestic energy supply mainly relies on the coal-fired power,which is high contamination and high emission.In recent years,everyone around the world advocated the sustainable development.It means people should meet their requirements,both current generation and future generations.It is an urgent task to optimize our country energy supply construction.As a clean energy,nuclear power is a great tool to solve the serious energy crisis.China has the biggest civilian nuclear power development plan on a global scale.For all environmental problems of vigorously developed nuclear power,are slowly coming into public focus.Radioactive waste water produced in many aspects of the nuclear energy development and utilization.Properly treatment of waste liquid has great significance to development of nuclear energy.In this dissertation,graphene successfully composite with gelator(chitosan or ethylene imine polymer)in the forms of graphene monolithic macroscopic morphology and used to the radioactive wastewater's treatment as adsorbent.The effect of solution pH values,contact time,initial concentration,ionic strength and other factors were studied.The interaction mechanism between metal cations and the hydrogel was clarified by using fourier transformation infrared(FT-IR),extended X-ray absorption fine spectroscopy(EXAFS),and X-ray photoelectron spectroscopy(XPS)characterizations.The main results of this dissertation were described as follows:(1)Graphene oxide-chitosan composite hydrogel has been successfully synthesized and used to separation and enrichment of uranium,europium,and thorium.The hydrogel had excellent mechanical properties.The adsorption capacity for U(VI),Eu(III)and Th(IV)amounts to 384,220,136 mg/g respectively.The surface innersphere complexation of metals by oxygen-and nitrogen-containing functional groups plays dominant roles in adsorption.The material has better selectivity in removing lanthanide and actinide and the efficiency of extraction of uranium from seawater is very high.(2)Graphene oxide-ethylene imine polymer composites hydrogel were successfully synthesized and used to separation and enrichment of uranium and Rhenium.The maximum adsorption capacities of U(VI)on the GO-PEI hydrogel at pH 5.0 were 629 mg/g and Re(VII)on the GO-PEI at pH 3.5 were 458.89 mg/g.U(VI)adsorption was attributed to the inner-sphere surface complexation with amino,hydroxy and residual carboxyl groups of GO-PEI in the acidic condition and hydrolysis precipitation in alkaline conditions.Re(VII)adsorption was ascribed to the anionexchange mechanism occurring on the protonated amino groups of PEI.The material has better selectivity in removing uranium and the application potential of GO-PEI for uranium harvesting from seawater is highlighted,which is also important for the environmental management and sustainable development of nuclear energy.