Study On Preparation And CO₂/N₂Permselectivity Of PANI-PVAm/PS Nanocomposite Membrane

CO₂capture is one of the most important subjects about energy and environment.Fixed carrier membrane is a kind of promising gas separation membrane for CO₂capture. However, fixed carrier membrane for CO₂capture is in an early developmentstage, its performance is not very high due to few membrane materials and thedifficulty in structure control of membrane. In this paper, polyaniline （PANI）nanoparticles with various morphologies were added to the fixed carrier membranematerial polyvinylamine （PVAm） and a series of new membranes with remarkablehigh CO₂/N₂permselectivity were developed.Polyaniline nanofibers, netlike polyaniline nanofibers and polyaniline nanosheetswere prepared by chemical oxidative polymerization. The PANI-PVAm/polysulfone（PS） nanocomposite membranes were prepared by solution blending. Severaltechniques were employed to characterize the structure of the membrane.Thepermselectivity of nanocomposite membranes was investigated by the pure CO₂andN₂gases and gas mixture containing20vol.%CO₂and80vol.%N₂. The resultsdemonstrate that the inclusion of the PANI nanoparticles to PVAm increases the gasCO₂/N₂permeance of the membranes due to chain packing disruption of PVAmthereby decreasing crystallinity of the membrane and increasing free volume of themembrane; PANI nanoparticles have good CO₂permeance; PANI nanoparticles haveN₂barrier property and the PANI nanosheets due to high aspect ratio have the betterN₂barrier property than other PANI nanoparticles; the PANI nanoparticles werededoped by a reaction of PANI nanoparticles with PVAm; the increased free volumeof PANI nanoparticles by the reaction of PANI nanoparticles with PVAm was moreconducive to CO₂permeance through the PANI nanoparticles.The effect of dopant species of PANI on the performance of the PANI-PVAm/PSnanocomposite membranes was investigated. It was found that dopant with small sizeof hydrated ion was more conducive to CO₂/N₂selectivity.The effect of doping/dedoping process of PANI nanoparticles on structure andperformance of the nanocomposite membrane was investigated. The resultsdemonstrated that the microstructure of the membrane can be tuned by doping/dedoping process of PANI nanoparticles and thus good CO₂/N₂permselectivity of the nanocomposite membranes was obtained.The gas transport characteristic in PANI-PVAm/PS membranes was analysed,which indicated that the characteristic is beneficial for improving the CO₂/N₂separation performance of the membranes.