The Effect of Concentration on PES/NMP System on Flat Sheet Membrane Fabrication and its Performance for CO2 Gas Separation

Carbon dioxide (CO2) capture utilising membrane technology have become the interest of research due to its low carbon footprint, feasible fabrication process and scalability in its operation. In this study, anisotropic polyethersulfone (PES) membrane was fabricated at various concentration ranging from 20 wt% to 35 wt% without the use of any additives. This study revealed that the finger-like structure disappeared with increased polymer dope concentration which was associated with increased viscosity of the dope solution. Moreover, the surface porosity of the membrane also virtually reduced with increased PES concentration as observed with the SEM images. The pure gas permeation test was also consistent with the observed morphology of the membrane. Membrane made with 20 wt% of PES dope solution exhibits the highest gas permeance which was 154.9 GPU at 2 bar while the CO2/nitrogen (N2) and CO2/methane (CH4) ideal selectivity was close to that of Knudsen’s selectivity value. With increased PES concentration, the CO2 gas permeance reduced drastically accompanied by enhancement on the CO2/N2 and CO2/ CH4 ideal selectivity. The critical concentration of PES dope solution obtained by plotting the PES dope concentration against viscosity was 29.4 wt%. With critical concentration of the dope solution, the CO2 permeance was recorded to be 8.1 GPU while the CO2/N2 and CO2/CH4 ideal selectivity were recorded to be 2.13 and 1.48, respectively at the pressure of 2 bar.