| Aqueous separation technology plays a very important role in the nuclear fuel cycle.In order to improve the utilization of resources,reduce the threat of radioactive and toxic nuclides to the environment and promote the sustainable development of nuclear energy,it is of great significance to develop more efficient separation methods and materials.The solvent impregnated absorbent material combined with the high selectivity of traditional liquid-liquid extraction and the simple operation of adsorption,has a broad application prospect in the field of radiochemical separation.Graphene aerogel?GA?is a kind of three-dimensional graphene architecture material with superhydrophobic,low density,high porosity,chemical stability and robust mechanical strength.It has great application potential as the matrix of solvent impregnated material.In this work,the GA was used as matrix material to prepare the GA based-solvent impregnated adsorbent?GA-SIA?.The immobilization of organic extractant on GA was investigated.The adsorption and separation of metal ions from aqueous solution by GA-SIA were studied.Furthermore,the radiochemical separation method based on GA-SIA was also developed.For the preparation of GA-SIA,first,graphene oxide?GO?was prepared from flake graphite by improved Hummers method,then the GA was fabricated from GO through sol-gel method employing ethylenediamine as a reducing agent.Subsequently,GA-SIA was prepared by impregnating organic solvent into GA.The GO and GA were characterized by atomic force microscope?AFM?,Raman spectroscopy?Raman?,Fourier transform infrared spectrum?FT-IR?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscope?SEM?and contact angle analysis technology.The impregnation rate and load capacity of GA for organic solvents were examined,the stability of GA-SIA in acid solution as well as the removal method of organic solvents from GA-SIA were also studied.The results revealed that the GO was obtained with well striping degree?single or partly three layers of stacked GO nano films?and high quality.GA is a kind of ultralight(pore size around 20-50?m,pore rate>99.8%,and density of 4.5 mg·cm-3)and superhydrophobic?contact angle>150°?material with three-dimensional network structure.It possesses high impregnation rate(reach to40.7 g·g-1·s-1)and high load capacities?2-3 orders of magnitude larger than that of similar adsorption material?for organic solvents.The organic solvent loaded on GA-SIA can be removed by mechanical squeezing and combustion due to the good compression elasticity and chemical stability of GA,thus realize the reuse of GA.The specific selectivity of GA-SIA depends on the impregnated organic extractant.So,the modular design of GA-SIA can conveniently be realized by selecting different extractant according to target ions.In this work,first,Tri-n-butyl phosphate?TBP?and N,N,N',N'-tetraoctyldiglycolamide?TODGA?were chosen as function extractants to prepare the corresponding GA-SIA?GA-TPB and GA-TODGA respectively?.The adsorption behavior of U and Th on GA-TBP and GA-TODGA were studied.The results showed that the adsorption efficiency of GA-TBP and GA-TODGA for U and Th depends on the extractant concentration and feed solution acidity,following the law of distribution ratio.The saturated adsorption capacity of GA-TBP and GA-TODGA for U and Th were 316.3 and 66.8 mg·g-11 respectively,higher than the similar adsorption materials.In addition,the desorption of metal ions from GA-SIA was also studied,and the reusability of GA-SIA was proved by adsorption-desorption cycle test.Considering the modular design and excellent adsorption performance of GA-SIA,aiming at the separation of typical metal ions in high-level liquid waste?HLLW?,two separation strategies based on GA-SIA were proposed in this work.In the“packet”strategy,GA-DMHMP,GA-DCH18C6,and GA-TODGA were prepared with different selectivity,to realize the group separation of Th/U,Sr and RE metal ions respectively.In“one-pot”strategy,the GA-TODGA was employed as absorbent to removal most of the metal ions in HLLW to greatly reduce the radioactive level of wastewater due to the excellent extraction ability of TODGA for Th,U,Sr and RE.Compared with the traditional HLLW treatment method,the process operation based on GA-SIA is simple,and has a good application prospect.In conclusion,because of the excellent organic solvent loading performance of GA,the solvent impregnated adsorption material which imploying GA as matrix material possesses some attractive characteristics,including simple preparation and operation,modular designable function,excellent metal ions adsorption performance,reusability and so on.According to different demand,the GA-SIA with high selectivity and efficiency can be obtained quickly,quantity,and modularly for the radioactive metal ions treatment.Compared with the traditional aqueous separation technology,the GA-SIA method can provide several advantages,such as simple operation process,high processing efficiency,and less secondry waste,consequently has good application prospect in the field of radiochemical separation. |
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