Incorporating ZIF-71 into poly(ether-block-amide) (PEBA) to form mixed matrix membranes for enhanced separation of aromatic compounds from aqueous solutions by pervaporation

As important chemical intermediates, phenol and aniline are common aromatic contaminants in relevant industrial wastewater that have drawn increasing attention due to their wide existence and high toxicities. In this work, zeolitic imidazolate framework (ZIF-71) crystals were incorporated into poly(ether-block-amide) (PEBA) to form mixed matrix membranes (MMMs) for the pervaporative removal of phenol and aniline from their aqueous solutions. The physiochemical properties of the MMMs were characterized with FTIR, XRD, SEM, EDX, and contact angle measurements. The pervaporation performance of the prepared MMMs at different ZIF-71 contents and operating temperatures was investigated. The ZIF-71 crystals showed good compatibility with PEBA polymer, and defect-free MMMs were produced at a ZIF content of as high as 28.6 wt%. The membrane became more hydrophobic and less flexible with an increase in the ZIF-71 loading, and water permeability was reduced significantly, whereas the permeability of the aromatic components was largely unaffected (phenol) or slightly lowered (aniline) because of the preferential sorption/diffusion of the aromatic solutes within the inner ZIF-71 channels, resulting in increased solute enrichment (or selectivity). At a feed concentration of 6,000 ppm and temperature of 60 degrees C, the ZIF-71/PEBA MMM with a ZIF-71 content of 28.6 wt% displayed a separation factor of 50 and 70 for phenol/water and aniline/water separations, respectively, which demonstrated the excellent potential of ZIF-71/PEBA MMMs as organophilic membranes for pervaporative extraction where the concentrated permeate stream could readily undergo a phase separation to augment the overall separation when the permeate concentrations reached the solubility limit.