Microfluidic synthesized ZIF-67 decorated PVDF mixed matrix membranes for the pervaporation of toluene/water mixtures

Abstract

Compared to traditional methods for removing volatile organic compounds (VOCs), the pervaporation (PV) process using the polymeric membrane is both efficient and cost-effective. In this work, the poly(vinylidene fluoride) (PVDF) polymer was modified by incorporating the hydrophobic ZIF-67 nanoparticles prepared using the microfluidic synthesis method. The prepared ZIF-67 and mixed-matrix membranes (MMMs) were analyzed using different analytical methods such as HRTEM, FESEM, AFM, water contact angle, solvent uptake study, FTIR, XRD, TGA, and UTM. The prepared membranes were tested for toluene/water mixture separation using pervaporation at 30 °C for 150 ppm toluene concentration in the feed solution. Further, the prepared MMMs were tested to study the effect of ZIF-67 filler loading, feed temperature, and feed composition on the total flux, toluene selectivity, and pervaporation separation index (PSI). Adding 3 wt% of ZIF-67 nanoparticles to the PVDF membrane increased the total flux and toluene selectivity from 5.25 to 41.24 L m−2 h−1 (684.8%) and 37.87 to 467.59 (1134.4% increment). The hydrophobicity of ZIF-67, validated by WCA, can be attributed to this significant boost in toluene selectivity. The toluene flux, water flux, and PSI for the optimized membrane were 2.70, 38.53, and 19234 L m−2 h−1, respectively. Also, the optimized MMMs showed stable 200 h of long-term separation performance. The results showed that adding hydrophobic ZIF-67 into the PVDF polymer matrix is an effective process for enhancing the toluene separation efficiency from the aqueous mixtures.