Investigation Of Multiscale Hierarchical Structure And Multiple Interactions In Membranes Utilizing Adhesivity Of Dopamine

To achieve the aim of improving the separation performance of gas separation mixed matrix membranes?MMMs?, three types of gas separation MMMs has been prepared based on the oxidative polymerization and surface modification properties of dopamine?DA?.Due to the self-assemble property of DA, the polar groups DA bearing could form hydrogen bonds with the hydroxyl?—OH? in polyvinyl alcohol?PVA?, which completed the physical crosslinking procedure of PVA. A series of DA-PVA/polyethersulfone?PES? nanohybrid hydrogel composite membranes were prepared by casting DA-PVA blending solution onto PES substrate. The effects of different DA concentration and self-assemble reaction time on the physical and chemical properties of PVA matrix were investigated, including hydrophilcity, water content, thermal stability and fraction free volume etc. The separation performance of DA-PVA/PES membranes was tested under humidified CO₂/CH4 binary gas mixture. The optimal separation property of DA-PVA/PES membrane was obtained with a CO₂ permeability of 16.7 GPU and a CO₂/CH4 selectivity of 43.2, 97.67 % and 143.85 % compared with PVA/PES membrane performance respectively. Considering both characterization and separation performance, the gas transfer model in DA-PVA/PES membranes was proposed.The catechol group in polydopamine?PDA? could fix small molecules with amine?—NH2? blocking. Utilizing tetraethylenepentamine?TEPA? as facilitated transport carriers of CO₂, PDA/TEPA particle was prepared via covalently binding TEPA onto PDA nanospheres. Elemental analysis?EA? indicated that loading amount of TEPA was 11.86 wt%. And the SEM image of PDA/TEPA particles showed the particle had a homogeneous size of 180²20 nm. Incorporating PDA/TEPA particles into Pebax? MH 1657 to fabricate Pebax-PDA/TEPA hybrid membranes and testing membrane separation performance under humidified CO₂/CH4 binary gas mixture. The optimal separation property of Pebax-PDA/TEPA?5? membrane was obtained with a CO₂ permeability of 450.36 Barrer and a CO₂/CH4 selectivity of 27.53, 97.09 % and 148.49 % compared with neat Pebax membrane performance respectively. Besides, the effects of feed pressure and operation temperature on Pebax-PDA/TEPA?5? membrane separation performance were investigated.Due to the properties of chelating reaction and electroless metallization with metal ions DA possessed, silver-containing Janus nanoparticles were synthesized by adhering silver onto polydopamine nanosphere and then were embedded in Pebax? MH 1657 polymer matrix to fabricate mixed matrix membranes for CO₂ capture. The Janus nanoparticle was composed of a polydopamine nanosphere?⁸0 nm? with plenty of catechol-chelated Ag+ ions and a catechol-reduced metallic Ag nanoparticle?²0 nm? epitaxially growing from the surface of the polydopamine nanosphere. The highly loaded Ag+ ions?58.41 wt% of total Ag content? served as CO₂ facilitated transport carriers and thereby endowed the membrane with CO₂ facilitated transport ability, and meanwhile the inorganic metallic Ag nanoparticle can interfere the polymer chain packing and optimize the membrane free volume characteristics therefore affect the diffusion behavior of gas molecules. The membrane separation performance for pure gas?CO₂, CH4, and N2? and binary gas mixtures?CO₂/CH4 and CO₂/N2? of the Janus nanoparticle-incorporated Pebax membrane was investigated. An anti-tradeoff effect was achieved by incorporation of the silver-containing Janus nanoparticles. The best separation performance of the Janus-incorporated Pebax membrane for pure gas was obtained with a CO₂ permeability of 150 Barrer and a CO₂/gas selectivity of 26.3 for CO₂/CH4 and 72.5 for CO₂/N2, i.e., 83%, 42% and 39% higher than those of neat Pebax membrane, respectively.