Preparation and characterization of ZIF-8 and ZIF-67 incorporated poly(vinylidene fluoride) membranes for pervaporative separation of methanol/water mixtures

Metal–organic frameworks (MOFs) are made up of metal centers and organic binders with larger surface area and distinct pore structures. Particularly significant advancement in MOF membranes has been achieved in three different directions: preparation of MOF membranes with larger surface area, improving the membrane performance by surface modification, and its usage with added features. However, its significance has not been completely known and concluded yet. MOF membranes are used in a variety of membrane-based separation like gas permeation, nanofiltration, pervaporation, membrane distillation, etc. This research aims to synthesize MOFs (ZIF-8 and ZIF-67) and MOF membranes (ZIF-8/PVDF and ZIF-67/PVDF) and used them in the pervaporative separation of the methanol/water mixture. MOFs and MOF membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetry analysis. Methanol/water mixtures were be used to study the performance of the prepared membranes. A study on the process parameters such as temperature (40, 45, 50, and 55°C), feed pressure (4, 8, 12, and 16 psi), and feed composition (10%, 20%, 30%, and 40% of water) was carried out to examine the effect of each process parameters for pure membrane. In contrast, Taguchi screening design was used to screen the most influential process variable. The optimized conditions based on Taguchi screening method were 55°C, 12 psi, and 40 %vol of water in feed. The obtained total flux of 425 L/m²h was observed for M3 membrane. As feed temperature increased, the total flux of all three membranes was increased.