(666a) Fundamental Study of Water Transport in Polyvinylidene Fluoride (PVDF) Derived Carbon Molecular Sieve (CMS)

The molecular transport in porous spaces is an essential area of research in industrial separations, catalysis, and geology. Transport of water-organic mixtures under high-loading conditions is often encountered in industrial separation applications such as purification of produced water, solvent recovery from water-organic mixtures, and various biorefinery separations. Carbon molecular sieves (CMS) are a useful and promising membrane material for studying the fundamentals of molecular transport, as these materials are chemically and thermally stable in addition to having a tunable pore size distribution. The study of organic solvent transport in carbon molecular sieve membranes has been previously investigated. However, there is a dearth of data on water transport in these small pore CMS systems. In this work, we investigated the sorption, diffusion, and permeation behavior of water in polyvinylidene fluoride (PVDF) derived CMS (PVDF-CMS) of various pore size distribution. The water sorption and diffusion coefficients are compared with an exemplary organic compound, p-xylene. The comparison shows how hydrophilicity and molecular size of permeate (kinetic diameter of water and p-xylene are 2.65Å and 5.85Å, respectively) affect the transport behavior in CMS with its ultra-micropore size in a range of 5Å – 7Å. Understanding the fundamentals of how pure water and organic solvent transport in CMS will further be used for exploring how water-organic mixtures transport in CMS membrane.