Preparation Of Modified GO/PVAm Membrane By Adjusting GO Interlayer Spacing For CO₂ Separation

CO₂ is one of the main gases that cause the greenhouse effect.How to economically and effectively capturing the CO₂ has become a topic of concern in China even the whole world.More and more attention has been paid on CO₂ membrane separation technology because of its advantages of energy saving and environmental protection.Development of high performance membrane materials is the key to large-scale commercialization of membrane separation technology.In order to develop the CO₂ separation membrane with excellent performance,the interlayer spacing of graphene oxide?GO?was controlled by chemical modification method.The GO/PVAm?polyvinylamine?mixed matrix membranes?MMMs?were prepared by adding the modified GO into the PVAm and the gas separation performance of the membrane was investigated.The mechanism of the gas transfer in the membrane was studied.This work is divided into the following two parts:?1?In this part,the composite material of ZIF-8@GO-NH₂ was synthesized by ZIF-8 nanoparticles in situ growth between the adjacent layers of aminated graphene oxide,i.e.,in the basic environment which at the presence ofethylenediamine,by adding the solutions of zinc nitrate hexahydrate and 2-methylimidazole into the aminated graphene oxide dispersion.ZIF-8@GO-NH₂ was added into the solution of PVAm to obtain a uniform casting solution and then was coated on the polyether sulfone?PES?support layer after defoaming.The MMMs was prepared by dry phase inversion method.The structure of the composites was characterized by Fourier transform infrared?FTIR?,X-ray diffraction?XRD?and N2 adsorption-desorption isotherms,the results show that the ZIF-8 and EDA was successfully loaded onto GO.The CO₂ separation performance of MMMs was tested by pure gas?CO₂ and N₂?.The results showed that: ZIF-8 can preferentially adsorb CO₂ because the microporous effect of ZIF-8,which could increase the solubility selectivity of CO₂.Aminated graphene oxide with the amino carriers can be dispersed more easily in PVAm,not only disrupting the accumulation of polymer chains,but also increasing the CO₂ reaction selectivity.The effect of ZIF-8@GO-NH₂ content in MMMs was investigated,when the content of ZIF-8@GO-NH₂ in PVAm was 2wt%,the CO₂ permeance was 108 GPU and the CO₂/N₂ selectivity was 129?at 1 bar?.In addition,the performance of the MMMs was studied under different operating conditions,such as feed gas pressure,temperature,the dry and wet state of feed gas and the pH value.?2?In order to further explore the effect of the interlayer spacing on the CO₂ separation performance,the composite material?P-GO?of GO was synthesized by introducing the low molecule PVAm.Then P-GO with differentinterlayer spacing was added into the solution of PVAm to obtain a uniform casting solution and then was coated on the polyether sulfone?PES?support layer after defoaming.The MMMs was prepared by dry phase inversion method.The structure of the composites was characterized by FTIR,XRD,showing the low molecule PVAm was successfully intercalated in GO and the interlayer spacing of GO increases with the increase of PVAm content.The structure of the MMMs was characterized by ATR-FTIR and XRD.The results showed that with the increased layer spacing of P-GO,and the crystallinity of the MMMs was decreased,which indicates that the free volume of MMMs was increased.The CO₂ separation of MMMs was investigated by pure gas?CO₂ and N2?.The results show that the CO₂ permeance increased with the increased of P-GO layer spacing,which have more free volume.When the content of P-GO-2?layer spacing 15.4 ??was 0.5 wt%,the CO₂ permeance of the P-GO-2/PVAm mixed matrix membrane is 217 GPU and the CO₂/N₂ selectivity is 132 at 1 bar.In addition,the CO₂ separation performance of the MMMs was studied under different conditions,such as feed gas pressure,temperature,the dry and wet state of feed gas,the pH value and feed gas flow rate.