Fabrication Of High-performance Polyvinylamine Membranes For CO₂ Separation

Highly efficient CO₂ separation plays an important role in CO₂ emisson and purification of energy sources.Among all kinds of separation technologies,membrane separation technology has amounts of advantages such as low fixed investment cost,low energy consumption and small occupied area,thereby having a broad prospect on CO₂ separation.Among various kinds of membrane materials for gas separation,the facilitated transport membranes display excellent CO₂ separation performance due to the revisable reaction between funcational groups and CO₂ molecules.The polyvinylamine（PVAm）is a typical facilitated transport membrane material,but the gas separation performance of PVAm could be limited by its low molecular weight and poor film forming ability.In recent years,in order to further improve the gas separation performance of the PVAm membranes,a large number of mixed matrix membranes（MMMs）have been worldwide developed.However,under high nanoparticles loadings,the interfacial nonselective areas between polymers and porous materials could be easily formed,which leads to a significant decrease of gas permselectivity.In view of the above problems,the molecular weight of PVAm was regulated to enhance the film forming ability and reduce the crystallinity,leading to improving the gas separation performance.The interfacial interaction between the polymer and nanoparticles was strengthened by chemical bridging-crosslinkig method to improve the permselectivity of MMMs.Firstly,on the basis of analyzing the factors affecting free radical polymerization reaction,the PVAm with high molecular weight was successfully synthesized by regulating the concentration of monomer,initiator and polymerization reaction temperature.The PVAm with high molecular weight was coating on the modified polysulfone membrane（mPSf）to fabricate the PVAm/mPSf membranes,which displayed excellent CO₂ permselectivity.The results showed that with increasing the molecular weight of the PVAm,the crystallinity of the PVAm gradually decreased and the amount of effective functional carriers in the PVAm/mPSf membranes progressively increased,thereby obtaining better CO₂ separation performance.Secondly,based on PVAm with high molecular weight as the continuous phase and UIO-66-NH₂ nanoparticles as the dispersed phase,the polymer and nanoparticles were chemical bridging-crosslinked via the macromolecular polyethylene-glycol-diglycidyl-ether（PEGDE）to form MMMs.The results showed that the chemical bridging-crosslinking method can effectively enhance the interfacial interaction between the polymer and nanoparticles,which reduce the interfacial nonselective areas under high nanoparticles loadings.In addition,PEGDE contains amounts of ether oxygen groups that can strengthen the dissolution selectivity of the MMMs.In addition,the pore structure of UIO-66-NH₂ can provid the efficient channels for CO₂ molecular fast passing from feed side to permeate side,enhancing the CO₂ permeability.Therefore,the MMMs perpared by chemical bridging-crosslinking method displayed excellent gas separation performance for CO₂/N₂mixed gases and good stability for the simulated flue gas.