Alicyclic Polyimide/SiO(2) Mixed Matrix Membranes for Water/n-Butanol Pervaporation

Alicyclic polyimides (PIs) have excellent properties in solubility, mechanical strength, thermal property, etc. This study developed two types of alicyclic PI-based mixed matrix membranes (MMMs) for water/n-butanol pervaporation application, which have never been investigated previously. The fillers were hydrophilic SiO(2) nanoparticles. The synthesized PI was mixed with SiO(2) nanoparticles in DMAc to make the casting solution, and a liquid film was formed over PET substrate using doctor blade. A dense MMM was fabricated at 80 °C and further treated via multi-stage curing (100–170 °C). The prepared membranes were characterized by FTIR, TGA, FE-SEM, water contact angle, and solvent swelling. The trends of pure solvent swelling effects agree well with the water contact angle results. Moreover, the pervaporation efficiencies of alicyclic PI/SiO(2) MMMs for 85 wt% n-butanol aqueous solution at 40 °C were investigated. The results showed that BCDA-3,4′-ODA/SiO(2) MMMs had a larger permeation flux and higher separation factor than BCDA-1,3,3-APB/SiO(2) MMMs. For both types of MMMs, the separation factor increased first and then decreased, with increasing SiO(2) loading. Based on the PSI performance, the optimal SiO(2) content was 0.5 wt% for BCDA-3,4′-ODA/SiO(2) MMMs and 5 wt% for BCDA-1,3,3-APB/SiO(2) MMMs. The overall separation efficiency of BCDA-3,4′-ODA-based membranes was 10–30-fold higher.