Synthesis Of Modified Graphene Materials And Study On Enrichment Of Uranium

Due to the vigorous development of nuclear energy and the wide application of nuclear technology,the human demand for uranium resources is increasing.The development and recycling of uranium resources has become a necessary step in the development of nuclear energy.Seawater is rich in uranium resources,about 4.5 billion tons.However,the uranium concentration is only 3.3 ppb,which makes seawater uranium extraction extremely expensive.How to extract uranium from seawater easily,quickly and economically has become a challenge for researchers in various countries.On the other hand,with the rapid development of nuclear energy applications,a large amount of uranium-containing wastewater needs to be treated and recovered to reduce the depletion of uranium resources.Graphene oxide(GO)is chemically exfoliated from graphite.It possesses both a two-dimensional planar structure and is rich in polar oxygen-containing groups.In this work,two modified graphene oxide materials are prepared,which can be applied to uranium extraction from seawater and uranium recovery from radioactive waste streams.In this paper,we developed a kind of composite microspheres(GO/ZIF-8@SA)composed of GO,ZIF-8,and sodium alginate.SEM and Mapping were used to determine the surface morphological characteristics and elemental composition of GO/ZIF-8@SA.The doping concentration of elements in the microspheres was measured by EDS.The presence of ZIF-8 in the microspheres and the successful preparation of the target materials were confirmed using XRD,FT-IR and XPS.From the adsorption experiments,it can be seen that GO/ZIF-8@SA not only has an ultrahigh adsorption capacity of 1897 mg/g for U(VI)in uranium-spiked seawater,but also has an extremely excellent U(VI)selectivity even in the presence of multiple competing ions.More innovative thing is,due to the addition of SA,the volume of GO/ZIF-8@SA can expand elastically with the adsorption of U(VI),and there is a mathematical relationship between the volume expansion rate and the adsorption capacity of uranium.The adsorption capacity of GO/ZIF-8@SA to uranium can be quantified by the variation of its volume with in a range.The swollen microspheres can be easily salvaged from the seawater through a mesh sieve,which greatly simplifies the solid-liquid separation step in the adsorption process and reduces the energy required for the separation.GO/ZIF-8@SA solves the problem of low adsorption capacity and poor selectivity of adsorbents for uranium in complex seawater environments,and has great potential for application in seawater uranium extraction.In this paper,elements N,P and S were combined with graphene oxide,three heteroatom-doped nanoporous graphene materials were prepared by combustion method.Three nanoporous graphene membranes,N-NPGM,P-NPGM and S-NPGM,were prepared by vacuum filtration method.They were characterized by SEM,XRD,FT-IR,XPS,and BET,and the characterization results showed that N-NPGM,P-NPGM,and S-NPGM contain both nanopores and the corresponding heteroatoms.In this paper,the retention performance study of uranium was carried out and compared for the three membranes.Not only the effects of permeate concentration,acidity,and driving fluid acidity on the retention performance of uranium were explored,but also the selectivity of N-NPGM,P-NPGM,and S-NPGM were investigated.The results showed that all three membranes had excellent retention of uranium,with N-NPGM having the best uranium retention effect.The three nanoporous graphene membranes showed specific retention of uranyl ions when multiple interfering ions were present in the solution.They allow the passage of monovalent ions with small diameters,while heavy metals such as uranyl ions are retained with almost 100% retention.This means that uranyl ions and other high-valence ions in radioactive wastewater can be trapped by nanopore membranes containing heteroatoms,therefore satified with discharge standards,enriching uranium while cleaning the wastewater.