Evaluation of membranes containing surface modifying macromolecules: Determination of the chloroform separation from aqueous mixtures via pervaporation

The pervaporation performance of polyethersulfone (PES) membranes prepared by incorporating surface modifying macromolecules (SMMs) was evaluated via experiments with chloroform/water mixtures as the feed. Isolation and chemi cal analysis of the organics in the permeate revealed that the permeate con tained virtually no chloroform. The bulk of the isolated organic compounds was ethanol. This differed from previous reports, which claimed that the or ganic component isolated via gas chromatographic analysis was chloroform (Y . Fang et al., Journal of Applied Polymer Science, 1994, Vol. 54, pp. 1934- 1943; Y. Fang et al., in Proceedings of the Seventh International Conferenc e on Pervaporation. Processes in the Chemical Industry, R. A. Bakish, Ed., Bakish Materials Corporation: Englewood, NJ, 1995, pp 349-362). It was demo nstrated that ethanol, used during the solvent exchange drying step of memb rane preparation, was retained in the membrane and leached out during membr ane use. However, while it was observed that SMMs in PES membranes contribu ted to no enrichment of chloroform, there was a significant depletion of ch loroform achieved in the permeate. The increased separation of chloroform f rom the SMM-modified membranes is hypothesized to be related to the unique fluorinated surface character endorsed within the material by the novel mod ification process. (C) 2000 John Wiley & Sons, Inc.