Preparation Of Two-Dimension Materials/Pebax Hollow Fiber Composite Membranes For CO₂ Separation

The“greenhouse effect”is a global climate.As the most important greenhouse gas,CO₂ brings many harms to the environment.Therefore,it is very important to find economical and efficient CO₂ separation methods.Compared with the traditional CO₂separation methods,the membrane separation method has the advantages of low energy consumption,simple operation,friendly environment,and small footprint,etc.,and is one of the most promising CO₂ separation technologies.The mixed matrix membranes have the advantages of easy processing and good film-forming performance of polymer membrane and good stability of inorganic membrane,which have become the research focus in these years.In this paper,we selected porous PVDF hollow fiber membranes as the based membranes,PTMSP or PDMS with high gas permeability as the isolation layer,commercial pebax with specific adsorption of CO₂ as the polymer matrix,and two-dimensional materials grapheme oxide?GO?and titanium carbide?MXene?as the inorganic filler.By changing the concentrations of two-dimensional materials to regulate the structures of the membranes,which constructed the relatively regular gas channels.In this experiment,Dip-coating method was used to prepare two-dimensional materials/Pebax hollow fiber composite membranes,which was applied to the separation of CO₂/N₂.The composite membranes have good mechanical properties and long-term operation stability.The main research contents are as follows:?1?GO-Pebax/PTMSP/PVDF hollow fiber composite membranes are prepared by Dip-coating method and applied to the separation of CO₂/N₂.When the concentration of Pebax was 3 wt%,the concentration of GO was 0.1 wt%and the withdraw speed was 0.3 cm/s,the gas separation performance of composite membrane was the best.At this time,the CO₂ permeance was 413.3 GPU,and the selectivity was 43.2.Compared with the pure Pebax membrane,the CO₂ permeance increased by 88%and the selectivity remained basically unchanged.The good interfacial compatibility between GO and Pebax enabled GO to be arranged in a parallel and orderly manner in the membrane,and relatively regular layer channels are constructed,and which increased the CO₂ permeance.Meanwhile,the 0.35 nm layer d-spacing is contribute to separation of CO₂/N₂.?2?In order to improve the gas separation performance of the composite membrane,MXene-Pebax/PDMS/PVDF hollow fiber composite membrane was prepared by using another new two-dimensional material called MXene.When the concentration of MXene was 0.05 wt%,the gas separation performance of composite membrane was the best.The CO₂ permeance was 476 GPU.On the one hand,MXene has a better interface interaction than GO in Pebax matrix due to the large number of homogeneous end groups on the surface of MXene.On the other hand,GO sheets are usually more flexible,which leaded to higher stacking efficiency and thus formed narrow layer channels.In contrast,MXene sheets are more rigid,larger in size,and easier to achieve orderly stacking,thus which formed more stable and regular channels that are not easily deformed.In order to further improve the selectivity of the composite membrane,polyethylene glycol diacrylate?PEGDA?containing a large number of EO segments was added into this experiment.When the concentration of PEGDA was 4.5 wt%,the CO₂ permeance of the composite membrane was 568 GPU,and the selectivity was 58.2,which was significantly improved compared with the previous one.