CHARACTERIZATION AND PERVAPORATION OF CHLORINATED HYDROCARBON-WATER MIXTURES WITH FLUOROALKYL METHACRYLATE-GRAFTED PDMS MEMBRANE

It is desirable to enhance the selectivity of a polydimethylsiloxane ( PDMS) membrane for chlorinated hydrocarbons. In this study, the PDMS m embranes were improved by graft polymerization of 1H,1H,9H-hexadecaflu orononyl methacrylate (HDFNMA), which has the effect of increasing the selectivity for chlorinated hydrocarbons. The PDMS membrane and HDFNM A were irradiated simultaneously by a Co-60 source. The grafted membra nes had a microphase-separated structure, that is, a separated structu re of PDMS and grafted HDFNMA. In the grafted PDMS membrane, a great s eparation performance for a TCE-water mixture was shown due to the int roduction of the hydrophobic polymer, poly(HDFNMA). For the permeation of the grafted PDMS membrane, the permeability of molecules in the PD MS phase was significantly great, and that in the poly(HDFNMA) phase w as too low to affect the whole permeation of the grafted PDMS membrane directly. However, the permeation of molecules at the inter face of p oly(HDFNMA) and PDMS played an important role because poly(HDFNMA) had a much stronger affinity for TCE than water. At a low feed concentrat ion of the TCE solution, the diffusivity of TCE molecules must be much lower than that of water due to the larger molecular size of TCE. At a high concentration of TCE solution, TCE was sufficiently sorbed into the membrane so that the diffusion of water was prevented by TCE mole cules; in turn, the permselectivity of TCE was increased significantly . (C) 1999 John Wiley & Sons, Inc.