The Fabrication And Qas Separation Performance Of Graphene Oxide Supported Ionic Liquid Membrane

The large amount of greenhouse gas emissions,dominated by carbon dioxide?CO₂?has made global warming a serious challenge for all mankind.At present,efficient enrichment of carbon dioxide is considered to be an effective way to reduce its impact and achieve resource recycling.Membrane separation technology is one of the potential strategies for efficient CO₂ capture and enrichment.With the discovery of two-dimensional layered materials,the unique ultra-thin structure and other excellent properties provide a basis for the construction of highly efficient ultra-thin separation membranes.However,the separation performance of the membranes constructed by pure two-dimensional materials needs to be improved.Ionic liquid is an emerging green solvent,which can selectively dissolve CO₂,but traditional ionic liquid-based membrane has low separation performance and poor stability.Here,we take graphene oxide,a typically two-dimensional layered material,as the separation membrane skeleton and confine ionic liquid into the two-dimensional nanochannel of graphene oxide membrane,to make graphene oxide supported ionic liquid membrane?GO-SILM?.The properties of the nanoconfined ionic liquid has changed,which significantly improves the CO₂ separation performance.On the base of GO-SILM,we apply an external electric field to change the distribution of nanoconfined ionic liquid in the two-dimensional space to further improve CO₂ separation performance.Combined with theoretical simulation,the corresponding separation mechanism is explained.The main results achieved are as follows:?1?GO-SILM was prepared from graphene oxide/1-butyl-3-methylimidazole tetrafluoroborate?[BMIM][BF₄]?dispersion by vacuum filtration and applied to CO₂separation.It was found that[BMIM][BF₄],nanoconfined in the two-dimensional nanochannel of graphene oxide membrane,played a key role in CO₂ separation.This composite separation membrane had better CO₂ separation performance than graphene oxide membrane and pure[BMIM][BF₄].?2?In order to study the universality of the idea mentioned in?1?,two-dimensional mica nanosheets were used instead of graphene oxide to prepare corresponding composite separation membranes.The difference was that we prepared pure mica membrane by vacuum filtration first,and then using capillary force to confine ionic liquid into the nanochannel constructed by two-dimensional mica nanosheets to prepare two-dimensional mica supported ionic liquid membrane?M-SILM?.The resultant membrane also had excellent CO₂ separation performance.?3?As ionic liquid was composed of anion and cation,which would directionally move under an electric field,and the spatial distribution of ionic liquid was changed,we applied an electric field on GO-SILM to observe the change of CO₂ separation performance,and the GO-SILM was prepared by the capillary embedding method,described in?2?.The results showed that the electric field could significantly improve CO₂ separation performance,but the extent of improvement under positive electric field was different from negative electric field.Combined with theoretical simulation,we discussed its mechanism.?4?In order to further expand the application of this idea,we dispersed a certain amount of AgBF₄ in[BMIM][BF₄],and prepared graphene oxide supported AgBF₄/[BMIM][BF₄]dispersion membrane?Ag-IL-GOM?by capillary embedding method.Since AgBF₄ could interact with olefins,it could be used as the carrier of facilitated transport of ethylene.The Ag-IL-GOM effectively separated ethylene from ethane,and its performance was better than most similar membranes.