Nanodisperse ZIF-8/PDMS hybrid membranes for biobutanol permselective pervaporation

Abstract

Alcohol-permselective membranes may play an increasingly important role in bioalcohol production. Developments for this membrane mostly involve hybrid membranes. Obtaining high compatibility and nanodispersion of inorganic nanoparticles in the polymer matrix is the key to fabricating hybrid membranes with high pervaporation performance. In this study, a homogeneous, nanodisperse ZIF-8/PDMS membrane was prepared by repeated immersion of a polysulfone supporting membrane in a dilute ZIF-8/PDMS suspension and subsequent removal of defects using a concentrated PDMS solution. To improve the nanoscale dispersion of ZIF-8, the nascent ZIF-8 suspension was directly dispersed in a PDMS solution without drying. This procedure avoids aggregation and redispersion of ZIF-8 nanoparticles after forming a powder. Analyses confirmed that the ZIF-8/PDMS dispersion effectively diminished aggregation between nanoparticles and led to the formation of a well-dispersed ZIF-8/PDMS membrane. A homogeneous and thin ZIF-8/PDMS permselective layer was obtained by adjusting the preparation conditions. The prepared ZIF-8/PDMS membrane exhibited a high separation factor (52.81) and high flux (2800.5 g m⁻² h⁻¹) in the separation of 5.0 wt% n-butanol–water solution at 80 °C. By comparing the powder-dispersed ZIF-8/PDMS hybrid membrane with the suspension-dispersed ZIF-8/PDMS membrane, we found that the latter showed much higher performance in butanol separation. Therefore, the nanodisperse ZIF-8/PDMS membrane has great potential applications for in situ recovery of biobutanol.