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In this study, the three phase mixed matrix membranes comprising Pebax®1657, PEG-200 and MIL-53(AL) nanoparticles were evaluated for CO2 gas separation. The effect of various PEG-200 and MIL-53(AL) concentration within the pebax polymeric matrix on the structure, gas permeability, and selectivity of the membranes was investigated. To study the cross-sectional morphology, crystallinity and thermal properties of the synthesized membranes, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were utilized, respectively. Fourier transform infrared (FT-IR), was also carried out to identify the formation of the chemical bonds in the membrane. SEM images demonstrated a uniform cross-section and admissible dispersion of nanoparticles. The results of the thermal analyses indicated an increase in crystallinity and Tg in presence of MIL-53 particles. Permeation of pure gases (i.e., CO2, CH4) through the prepared neat Pebax®1657, the blended Pebax/PEG-200 and the Pebax/PEG-200/MIL-53(AL) mixed matrix membrane was measured at the pressure of 2–10 bar and temperature of 30 °C. The results showed that at the pressure 10 bar, the CO2 gas permeation from 133.36 barrer in pure membrane increased to 311.7 barrer (134%) in a membrane containing 10%wt MIL-53.
 

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Research subject: Selectivity and permeability are the major parameters of polymeric membranes in gas separation process. Hence, nowadays in order to improve aforementioned parameters, modification and enhancement issues for such membrane have been highly noticed.
Research approach: In this study, in order to improve the performance of polymeric membranes, the two-component blend membranes containing Pebax^®1657 and PVA were synthesized for CO₂ separation. The effect of different PVA concentrations within the Pebax matrix on structure, morphology and gas separation properties of resultant membranes was investigated. The chemical bonds, crystallinity and cross-sectional morphology studied through, Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), and were utilized.
Main results: The results of the thermal analysis indicated an increase in crystallinity and also glass transition temperature in presence of 5 – 15 wt.% PVA, while the membrane crystallinity decreased by increasing the PVA content up to 20 wt.%. FESEM images demonstrated a uniform cross-section without any cracks and defects for neat Pebax membrane but by adding PVA to Pebax matrix, appeared cracks and cave structures on the cross- section of blend membranes. The CO₂/CH₄ separation performance of membranes was measured using a constant volume set up at 30°C and feed pressure of 2, 6 and 10 bar. The obtained results revealed that the CO₂ permeability in blend membranes improved as the PVA content increased within the membrane. The best obtained CO₂ permeability was 204.64 Barrer which gained by Pebax/PVA (20wt.%) at feed pressure of 10 bar. Moreover, the highest selectivity of CO₂/N₂ for blend membrane with 15 wt.% of PVA was about 100.21 at 10 bar and 30°C.