Preparation Of Mixed Matrix Membrane Incorporated With Low-dimensional Nanomaterial For CO₂ Separation

The global warming and frequent occurrence of extreme weather caused by the greenhouse effect have become a hot issue of global concern.The control and reduction of greenhouse gas emissions such as CO₂ are highly valued by governments and scientific communities around the world.Membrane technology is one of the most promising capture technologies,which requires high permeability and selectivity for CO₂ separation membrane materials.This study aimed at developed the high performance mixed matrix membranes?MMMs?.The multiple functionalized low-dimensional nanomaterials are designed as the dispersed phase to prepare high-performance MMMs.The CO₂ transport channels were constructed in the MMM by adjusting the arrangement of the fillers and optimizing the interface morphology,for improve the CO₂ separation performance of the membrane.The details are as follows:?1?The polyaniline decorated halloysite nanotubes?PANI-d-HNTs?were incorporated into sulfonated poly?ether ether ketone??SPEEK?to fabricate mixed matrix membranes?MMMs?,which contained multilayer hollow and tubular structure for high efficient CO₂/N₂ separation.ATR-FTIR and SEM result showed that the strong interfacial interaction between PANI-d-HNTs and SPEEK.The effects of PANI-d-HNTs content and feed pressure were systematically investigated using CO₂ and N₂ pure gas.Moreover,the CO₂/N₂?20/80 vol%?mixed gas separation performance also were investigated.At testing temperature of 25°C and feed gas pressure of 1 bar,MMMs containing 0.9 wt%PANI-d-HNTs loading exhibited superior long-term performance stability,and the CO₂separation performance maintained high CO₂ permeability of 1250 Barrer with CO₂/N₂selectivity of 82.9 for mixed gas over 120 h,surpassing the Robeson's upper bound reported in 2008.This was attributed to that PANI-d-HNTs with multilayer hollow and tubular structure can be used as high-speed CO₂ facilitated transport channels,in which the closely arranged secondary amino groups could readily react with CO₂ to facilitate transport in MMMs.?2?The sulfonated poly?ether ether ketone?with in-situ doped carbon dots?SPEEK-CDs?were blended with PVA to fabricate SPEEK-CDs-PVA/PSf mixed matrix composite membranes,which the porous polysulfone?PSf?as a support layer.The formation of relatively loose organic-inorganic crosslinked network among the CDs,PVA and SPEEK,as confirmed by ATR-FTIR and SEM analysis,resulted in incresed swelling resistance and thermal stability.The effects of feed pressure and operating temperature were systematically investigated using CO₂/N₂?20/80 vol%?mixed gas.At testing temperature of25°C and feed gas pressure of 1 bar,the SPEEK-CDs-PVA/PSf membrane?SPEEK-CDs-0.5:PVA=80:20?exhibited high CO₂ separation performance,with a CO₂permeance of 110 GPU and CO₂/N₂ selectivity of 92.9 for mixed gas;higher than the literature reported SPEEK-based gas separation membrane.This was attributed to that the formation of CO₂-philic transport channels by the channel-like assembly of the CDs,in which the sulfonic acid groups grafted on the surface of the CDs by esterification was used as CO₂ transport sites to facilitate transport in membranes.In addition,SPEEK-CDs-PVA/PSf membrane exhibited excellent plasticization resistance,good temperature adaptability and long-term operation stability over 200 h.?3?The branched polyethylenimine decorated halloysite nanotubes?PEI-HNTs?were incorporated into polyvinylamine?PVAm?to fabricate PVAm-PEI-HNTs/PSf mixed matrix composite membrane,which the porous polysulfone?PSf?as a support layer.ATR-FTIR characterization results showed that the good interfacial compatibility between PEI-HNTs and PVAm.The effects of PEI-HNTs content,feed pressure and the thickness of coating layer were systematically investigated using CO₂ and N₂ pure gas.Moreover,the CO₂/N₂?20/80 vol%?mixed gas separation performance also were investigated.At testing temperature of 25°C and feed gas pressure of 1 bar,PVAm-PEI-HNTs/PSf membranes with1 wt%PEI-HNTs-3 exhibited the optimal CO₂ permeance of 228 GPU and CO₂/N₂selectivity of 143.0 for mixed gas,respectively.When compared with the PVAm/PSf membrane,they were 2.17 and 2.52 times higher,respectively.This was attributed to that the PEI-HNTs with internal honeycomb structure can be used as stable limited-domain facilitated transport channels,in which the interlaced amino groups in dendritic PEI could readily react with CO₂ to facilitate transport in MMMs and avoided the“waiting effect”.PVAm-PEI-HNTs/PSf membranes exhibited long-term operation stability over 200 h.