Development of novel blend poly (Ethylene Glycol) / Poly(Ethersulfone) polymeric membrane using N-Methyl-2-Pyrollidone and dimethylformamide solvents for facilitating CO2/N2 gas separation

Abstract Carbon dioxide (CO2) emissions have been the main cause for anthropogenic climate change. To meet the growing demand for CO2 removal, membrane separation technology using blend membranes is a promising and attractive alternative. Recently, blend membranes consisting of glassy and rubbery polymers has risen in popularity for the gas separation industry due to its ability to effectively minimise trade-off between selectivity and permeability. In this study, glassy poly(ethersulfone) (PES) is blended with rubbery poly(ethylene glycol) (PEG) using a mixture of n-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF) solvents. Compatibility of PES, PEG, NMP, and DMF within the casting solution was studied using the Hansen solubility parameter (HSP) ternary diagram. Moreover, compatibility of different weight ratio of NMP/DMF solvents (45/15, 40/20, 30/30, 20/40, and 15/45) with respect to the 20/20 PEG/PES polymer blend was investigated based on its relative affinity values. Additionally, single-gas permeation test was used to evaluate the performance of the synthesized PEG/PES blend membranes towards CO2/nitrogen (N2) separation. Scanning electron microscopy, contact angle, and attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analysis were conducted to analyse the membrane morphology, wettability, and functional groups, respectively. Based on the HSP ternary diagram, PES, PEG, NMP, and DMF were predicted to be miscible in the casting solution. Blends are also deemed more compatible with higher DMF fraction due to the decreasing relative affinity values with increasing DMF fraction. According to the results, NMP/DMF solvent concentration was optimized at 20/40 NMP/DMF having obtained the highest CO2/N2 selectivity of 1.36 ± 0.01 and CO2 permeance of 6277.45 ± 11.0 GPU. On that regard, the enhanced CO2/N2 gas separation performance of the PEG/PES blend membrane can potentially have an important contribution to CO2 separation processes in the industry in order to decrease emissions and minimize the risk of climate change.