A novel ceramic-supported polymer membrane for pervaporation of dilute volatile organic compounds

A novel asymmetric ceramic-supported polymer (CSP) pervaporation membrane was developed using free-radical graft polymerization of polyvinyl acetate (PVAc) onto a porous tubular silica substrate. The resulting membrane was characterized by pervaporation removal of trichloroethylene (TCE) and chloroform from dilute aqueous solutions. PVAc was chosen since it has a high affinity for TCE and chloroform and a low affinity for water, thus making the membrane permselective toward these solutes. This study has shown, for the first time, that pervaporation is possible even with a large substrate starting pore size (similar to 500 Angstrom) and where the active separation phase is a macromolecular layer of terminally anchored chains. Performance of the CSP membrane was assessed at various hydrodynamic conditions and feed concentrations. Resistance of the PVAc/CSP membrane was found to be negligible compared with the concentration boundary layer resistance. The enrichment factor, defined as the ratio of total solute concentration in the permeate to that in the feed, increased with polymer graft yield. For a,given graft yield, the enrichment factor approached an asymptotic plateau value, as the tube-side Reynolds number was increased due to increased water flux in response to the rise in transmembrane pressure. Preliminary analysis suggests that the CSP pervaporation membrane performance could be substantially increased by optimizing reaction conditions to produce a higher polymer graft density. (C) 1999 Elsevier Science B.V. All rights reserved.