Effects of solvent and ionic liquid properties on ionic liquid enhanced polysulfone/SAPO-34 mixed matrix membrane for CO2 removal

The poor compatibility between polymeric matrix and inorganic filler in mixed matrix membrane (MMM) generates interfacial defects that reduce the gas selectivity. In this work, the defects in polysulfone (PSf)/silicoaluminophosphate (SAPO)-34 zeolite mixed matrix membrane was post-treated using three types of ionic liquid with CO2 affinity. The effects of solvent (methanol and ethanol) and ionic liquid used in modification on membrane properties and CO2 removal was studied. The presence of ionic liquid in the modified MMM was confirmed in Fourier-transform infrared spectroscopy analysis. The CO2/N-2 selectivity of the MMM was enhanced more than 700% after being treated using 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim] [BF4]) ionic liquid solution in methanol. The solvent polarity could affect the solubility and mobility of ionic liquid during modification. When 1-ethyl-3-methyl imidazolium bis(tri-fiuoromethylsulfonyl)imide ([emim] [Tf2N]) ionic liquid was used, the CO2/N-2 selectivity and CO2 permeance could be further increased to 44.9 and 7.19 GPU, respectively.