Preparation,Characterization Of Two Graphene Membrances And Separation Performances For UO₂²⁺,Eu³⁺ And Th⁴⁺

The selective separation of metal ions is always the research hotspot in nuclear and radiochemistry.Common separation methods are solvent extraction,ion exchange,precipitation,etc.Membrane separation was paid attention for its non-phase change,energy saving,economical and practical advantages.Graphene is an ideal membrane material,which is a two-dimensional networked material developed in recent years.Two kinds of graphene membranes,monolayer nanoporous graphene and graphene oxide membranes,are used in this paper.The metal ions in one side of the membrane go through functional layer to another side of membrane,and theirs passage rate will have difference for their binding abilities with functional group of membrane.The various factors influencing the passage of metal ions were studied.1.The monolayer graphene composite membrane was prepared by PET nuclear track membrane and monolayer nanoporous graphene?MNPGM?.PET nuclear track membrane and nanoporous graphene are all generated by the bombardment of the heavy ion accelerator.PET nuclear track membrane is etched by alkali and the hole will appear,that are the ions transfer channels which does not interfere with the ion penetration.The holes were characterized by means of TEM,SEM,Raman spectroscopy and other means.The hydroxyl and carboxyl groups were found near the pore where the graphene was irradiated by the photoelectron spectroscopy.These 1 nm diameter graphene pores and their surrounding oxygen groups are considered to have selective sieving capabilities for metal ions.The rate of passing membrane was related to the ionization radius,the ionic valence state,the H⁺ concentration of liquid and the applied electric field.It was found that the rate of Eu³⁺ through MNPGM was higher than that of UO₂²⁺ in acidic solution.The addition of DC electric field could significantly increase the permeation rate of high valence ion and expand the difference of the ion permeation rate.To the same valence of lanthanide metal ions,alkali metal ions,transition metal ions,the permeation rate depends on their hydration ion radius while it cannot be affected by the DC electric field.Temperature also affects the ion permeation rate and separation performance,the rate of metal ions through the membrane increase with temperature increase.It is also found that NO₃^-and organic molecules cannot pass through the MNPGM membrane.2.Another kind of functional separation membrane,graphene oxide?GO?,reduced grachene?RGO?and amino functionalized graphene?AFGO?,is prepared.The difference of ion permeation rate through the three membranes depends on the difference of binding force between metal ions and the membrane.It is found that Eu³⁺ and UO₂²⁺;K⁺,Ca²⁺ and Fe3+ can be separated by GO from the mixed components.RGO is prepared by reducting a large number of oxygen groups on the GO layer and leads to further narrowing the nanometer pores between the RGO layers.RGO has higher separation effect of different mixed ions compared with GO.AFGO is obtained by modifying GO with ethylenediamine.The separation between UO₂²⁺ and Th⁴⁺,Th⁴⁺ and Eu³⁺ are achieved for the help of O and N on the amide groups.