| Uncontrolled emission of carbon dioxide(CO2) has been identified as an important contribution to global warming, thus causing a great threat to the existence of human being. Therefore, it is really urgent to explore some novel CO 2 capture technology. Membrane technology has been considered as an affordable, green, and potential separation technique for CO2 capture and separation. Poly(ethylene oxide)(PEO) has attracted significant scientific interests due to the dipole–quadrupole interaction between CO2-philic units of ethylene oxide(EO) and CO2 molecules. However, the high tendency of crystallization of tranditional PEO-based membranes has greatly limited the transport performance, which should be restrained effectively because PEO is a semicrystalline polymer of which the crystalline domain is impermeable for gases. In this study, cross-linked PEO membranes are synthesised by utilizing the amino functional PEO and epoxy functional PEO with low molecular weight. Subsequently, low-molecular-weight poly(ethylene glycol)(PEG) is deliberately incorporated into synthesized swellable PEO membranes via a facile post-treatment strategy for enhancing the gas transport properties of PEO membranes. In addition, graphene oxide/PEO composite membranes are prepared to improve the mechanical properties of PEO membranes. The physicochemical properties and gas transport properties of coss-linked PEO membranes are studied. The gas transport properties and mechanism of PEO membranes immersed into PEG solution are studied in detail.Cross-linked PEO membranes were synthesized by thermol cross-linking reaction between epoxy functional PEO and amino functional PEO with different molecular weights. The physicochemical properties have been determined by Fourier Transform Infrared Spectroscopy, 13 C solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy and X-ray diffraction. The tendency of crystallization of PEO was restrained and the amorphous structure at room-temperature of cross-linked PEO membranes was confirmed. PEO membrane(HCM) prepared by amino functional PEO(Mw = 2000 g/mol) exhibits better gas transport properties than that of PEO membranes(LCM) prepared by amino functional PEO(Mw = 600 g/mol) due to the higher fractional free volume, which is benefitial for the gas difffusion process. The CO2 permeability of HCM is 280 Barrer(35 oC, 10atm), while the CO2/H2, CO2/N2 and CO2/CH4 selectivity are 9.3, 48 and 16.7, respectively.Low-molecular-weight PEG was deliberately incorporated into synthesized swellable PEO membranes to improve the gas transport properties of PEO membranes. The effect of PEG molecular weight on gas transport properties was determined. The end groups of PEG could strongly affect gas transport properties according to the results, and the excellent gas transport properties can be achieved by using Polyethyleneglycol dimethyl ether(PEGDME). The Tg values decrease and fractional free volume increase with increasing PEG loading, which is benefit for improving gas diffusion process. The highest CO2 permeability is 1716 Barrer, while CO2/H2 and CO2/N2 selectivities are 12.5 and 53.Graphene oxide(GO) with vast xygen-containing groups is prepared by modified Hummer method and GO/PEO composite membranes are synthesized by incorporating GO into the PEO cross-linked structure. The physicochemical properties of GO/PEO composite membranes are studied, indicating that GO is involved in the cross-linked reaction, leading to the favorable interface bonding between GO and PEO. The mechanical properties of GO/PEO composite membranes are improved significantly due to the incorporation of GO, especially, the tensile modulus increases by 368%. Higher gas permeability can be obtained when GO content reached 1.0 wt.%. The gas transport performance is further improved by impregnating GO/PEO composite membranes into PEGDME-water solution. The highest CO2 permeability of impregnated GO/PEO membrane is1405 Barrer, CO2/H2 and CO2/N2 selectivities are 10.9 and 43, respectively. |
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