A high-efficiency diffusion process in carbonized ZIF-8 incorporated mixed matrix membrane for n-butanol recovery

Abstract

The diffusion process is the rate-limiting step for n-butanol recovery from diluted aqueous solution, which can be improved by incorporating hydrophobic nanoparticle into the polymer matrix. However, the micropore structure of zeolitic imidazolate framework-8 (ZIF-8) in the commonly applied ZIF-8-based mixed matrix membrane (MMM) could hardly meet the diffusion demand of the penetrant molecules. Herein, ZIF-8-derived nanoporous carbon (ZNC) with larger pore diameter and pore volume was prepared to replace ZIF-8 in conventional MMM in order to improve the diffusion process. An increase of 68.7% in n-butanol permeability of ZNC/PDMS MMM with 3 wt% of particle loading was obtained compared with ZIF-8/PDMS MMM. Coupled with the good compatibility between ZNC and PDMS, ZNC was homogeneously dispersed in PDMS matrix. As a result, a n-butanol permeability of 109,583 Barrer and a n-butanol/water selectivity of 4.47 were obtained for n-butanol recovery from 1.5 wt% n-butanol/water solution at 55 °C, which were increased by 145.4% and 17.6%, respectively, compared with the pure PDMS membrane. Overall, the ZNC-filled PDMS membrane shows promising in effective separation of n-butanol in realistic applications.