Preparation And Separation Performance Of CO₂ Fixed Carrier Composite Membrane

Membrane separation technology is considered as a green and environmental method to separate CO2,making it one of the focus of scientific research.The key point of obtaining a separation membrane with high separation performance is to choose suitable membrane materials.Herein,PS was used as supporting layer,the mixture of PVA and PVI was used as separating layer,and ZIF-8 nanoparticles and metal ions were used as additive to prepare a series of fixed carrier composite membranes.The permeation selectivity of these composite membranes in CO2/N2 gas system was studied.The investigation of PVI-PVA/PS fixed carrier composite membranes:PVA has good membrane formation performance and gas separation performance.The molecular chain of PVI has imidazole groups which can interact with CO2 that facilitates the transfer of CO2 molecules in the membrane.A mixed solution of two polymers was prepared for the fabrication of the PVI-PVA/PS fixed carrier composite membranes.The results show that when the solid content is 4%,the mass ratio of PVA to PVI is 7:3,the CO2 permeance is about 11 GPU,and the selectivity of CO2/N2 is up to 73 at a pressure of 1 bar.The investigation of ZIF-8-PVI-PVA/PS fixed carrier composite membranes:ZIF-8 nanoparticles were added to PVI-PVA membrane solution to investigate the effect of the mass content of ZIF-8 nanoparticles on the separation performance of ZIF-8-PVI-PVA/PS composite membrane.The N atom in the ZIF-8 nanomaterials has a great binding effect on CO2,which can make the composite membrane have screening effect.The results show that when the solid content of the coating liquid is 4%,the mass ratio of PVA to PVI is 7:3,and the mass fraction of ZIF-8 is 0.05%,the CO2 permeance is about 10 GPU,and the selectivity of CO2/N2 is up to 114 at a pressure of 1 bar.The investigation of Mg2+-PVI-PVA/PS fixed carrier composite membranes:metal ions can bond with OH-in PVA in a coordination bond.There are many imidazole rings in the PVI polymer chain which have a strong coordination function with metal ions.Magnesium salt was added to PVI-PVA membrane solution to prepare Mg2+-PVI-PVA/PS fixed carrier composite membrane,so as to enhance the gas separation performance of the composite membrane.The results showed that the CO2 permeance was 12 GPU and the separation factor of CO2/N2 was 183 at a pressure of 1 bar.Besides,the influence of Cu2+ on the permeation selection performance of the composite membrane was also investigated.The results showed that the CO2 permeance was 10 GPU and the separation factor of CO2/N2 was 130.