| In order to meet the requirements of a green global village and the new progress of ecological civilization in the 14th Five-Year Plan,China needs to vigorously develop new types of clean energy represented by nuclear power.Uranium is one of the main fuels for nuclear power plants,but a large amount of uranium-containing waste water is inevitably produced in uranium mining,nuclear fuel manufacturing and spent fuel reprocessing.Therefore,separation,enrichment and treatment of uranium from waste water are essential to improve the efficiency of uranium use and environmental protection.Graphene nanoribbons(GNRs)is a new type of carbon nanomaterials that have the excellent properties of both carbon nanotubes and graphene,and it is currently widely used in the study of radionuclide adsorption and separation.However,There still are some disadvantages in the utilization of graphene nanoribbons as adsorbents,such as difficulty in solid-liquid separation and poor selectivity,and the adsorption mechanism has not been systematically studied.In view of this,ton the basis of preparing Graphene Oxide Nanoribbons(GONRs)by Tour's method,the inorganic,and organic modification method were used to prepare three composites that were beneficial to improve the selection and solid-liquid separation ability of GONRs.And their structure,morphology and properties were characterized.On the basis of these,some factors which influenced the adsorption behavior of the three materials on U(?)were systematically studied,such as the p H,the amount of adsorbent,contact time,initial uranium concentration and temperature,and the adsorption mechanism of the three materials on U(?)was explained.The main progress made in the thesis was as follows:(1)Graphene nanoribbon/chitosan(GONRs/CTS)membrane composites were prepared by gelatin copolymerization of chitosan(CTS)onto GONRs surface.The maximum adsorption capacity of U(VI)on GONRs/CTS was 320 mg/g,which was higher than that of graphene nanobelts and chitosan.The adsorption process was affected by p H,endothermic and spontaneous,and had good regeneration performance.(2)Graphene nanoribbons/manganese dioxide(GONRs/Mn O2)granular composites were prepared by hydrothermal loading Mn O2 onto the surface of GONRs.The maximum adsorption capacity of GONRs/Mn O2 for U(VI)could reach 345 mg/g.The adsorption process was monolayer chemical adsorption.Higher temperature was favorable for the adsorption process and had good regeneration performance.(3)Polyamidoxime/graphene nanoribbon(PAO/GONRs-A)gel composite was prepared by solvothermal polymerization and its adsorption behavior on U(VI)was investigated.It is found that the synthesized aerogels had a three-dimensional net porous structure with a specific surface area of 494.9 m2/g and good thermal stability.The adsorption process of U(VI)on PAO/GONRs-A conformed to Langmuir model,internal diffusion model and quasi second-order kinetic model.The maximum adsorption capacity and selectivity were 589.05 mg/g and65.23%respectively,indicating that the adsorption performance of U(VI)on PAO/GONRs-A was greatly improved after functionalization of amidoxime.XPS analysis and DFT calculation showed that the adsorption mechanism of PAO/GONRs-A with U(VI)was to form stable complex UO2(PAO)2(H2O)3,while UO22+was connected with PAO/GONRs-A by a large number of functional groups containing N and O.The organic and inorganic modification of graphene nanoribbons by hydrothermal method,gel copolymerization and solvothermal polymerization were established through this study,and three kinds of graphene nanoribbon composites which were highly adsorbed on uranium and were easy to separate from solid-liquid were obtained,such as GONRs/CTS,GONRs/Mn O2and PAO/GONRs-A.Besides,the adsorption mechanism of the new materials on U(VI)was revealed and it was found that PAO/GONRs-A had high adsorption capacity and selectivity for U(VI)and was expected to be used for selective separation and recovery of uranium in different aqueous media containing uranium. |
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