Synthesis of highly water selective copolymer membranes for pervaporative dehydration of acetonitrile

Abstract

Pervaporative dehydration of highly concentrated (90–99.9%) acetonitrile needs a chemically resistant membrane having high water selectivity. Crosslinking is the usual practice of controlling excessive swelling in solvent and increasing selectivity of a hydrophilic membrane at the cost of flux. A membrane prepared from a copolymer of acrylonitrile and itaconic acid would be chemically resistant due to its acrylonitrile moiety and also hydrophilic due to the presence of bicarboxylic itaconic acid in its structure. Further, crosslinking is not required for preparing this copolymer membrane. Thus, in the present work several hydrophilic membranes were prepared by copolymerizing acrylonitrile (AN) and itaconic acid (IA) at varied molar ratios depending on their relative reactivity ratios. The structure of the copolymer was characterized by FT-IR, XRD and TG-DTA. The membranes prepared with an AN: IA molar ration of 15:1, 12:1 and 10:1 and noted as PANIA1, PANIA2 and PANIA3, respectively showed optimum properties, viz., mechanical stability, flux and selectivity. Thus, for 99wt% acetonitrile in feed at 30°C, these membranes showed a thickness normalized flux of 1.7, 1.8 and 1.9kgμm/m2h and a high water selectivity of 459, 429 and 409, respectively.