Permeability Of Amino Functionalized Nanoporous Single-layer Graphene And Modified Graphene Oxide Membranes

Under the new situation of the rapid development of nuclear power,a safe and effective disposal method of spent fuel generated is not only a great challenge for the nuclear and energy industry,but also one of the key factors affecting the sustainable development of nuclear power in China.The separation of actinides and lanthanides from high-level radioactive waste is an important project in the field of separation science and radiochemistry.Within the common separation methods for metal ions including adsorption,precipitation,ion exchange and membrane separation,membrane separation has attracted much attention due to its advantages of good selectivity,no phase transition,strong adaptability and low energy consumption.Two-dimensional graphene materials have been widely applied in biomedical,energy,sea water desalination,membrane separation and other fields for its excellent physical and chemical properties.Three kinds of membrane materials containing graphene were prepared in this work,and their performances in selective separation of metal ions were explored.Amino-functionalized PET nanoporous single-layer graphene membrane（NSGM-A）was prepared by the amino modification of nanoporous single-layer graphene（NSG）with different radiation fluxes.Both NSG and NSGM-A were characterized by SEM,Raman and EDS.The results show that NSG was successfully transferred and modified into NGSM-A.The study reveals that the permeance of lanthanide and actinide ions is proportional to the radiation flux and the charge number.Oxygen-containing groups around the nanopores have strong electrostatic attraction to the high valence cation,adsorbing the high valence ions to the periphery of the nanopores,so that the exchange with H⁺and infiltration can be easily realized.Amino groups on the NSGM-A can chelate UO₂²⁺,reducing the permeance of UO₂²⁺and making the separation effect between UO₂²⁺and other ions more significant.For the isovalent lanthanide elements La³⁺,Eu³⁺and Lu³⁺,which are difficult to be separated,the separation capability is also better than non-modified NSG membranes.Dopamine-covered graphene oxide（GO-25,GO-80 and GO-120）composite membranes were prepared by vacuum filtration and heat treatment at 25℃,80℃and120℃respectively.SEM,FTIR,Raman and XRD were used to characterize the structure of the composite films.Dopamine-covered substrates can effectively improve the stability of composite membranes.The layer spacing of the GO membrane can be changed by heat treatment.Studying the permeation capacity for the composite membrane with ions in the same main group or period,it is found that the radii of hydrated ions and the interval between layers affect the permeation flux.The permeation flux increases as the radius of hydration ions increases,valence state of the metal ions increases,or interlayer spacing of the membrane decreases.In different acidity and ionic systems,GO-120 is found to have the strongest separation capacity.In addition,the adsorption behaviors of K⁺,Ca²⁺and Fe³⁺onto the composite membrane were also investigated.By determining residual ions in the composite membranes,the influence of metal ions in layer spacing and Na⁺permeability was identified.Porous GO was prepared by combustion method,and then acrylic acid was polymerized with porous GO to obtain high-strength porous GO membrane（HPGO）.TEM,SEM,FTIR and XPS were used to characterize the membranes,showing that the membranes have stable layered structure.The permeability of alkali and alkaline earth metals was studied.By comparing the separation factors with GO membrane,it is found that HPGO has better separation effect to the metal ions than GO membrane.