STABILIZATION OF SUPPORTED LIQUID MEMBRANES BY GELATION WITH PVC

This article describes the gelation by PVC of supported liquid membran es (SLMs) for nitrate removal using a quaternary ammonium salt as carr ier. Untreated SLMs with this carrier are very unstable. To improve th eir stability, the LM-phase was gelled with polyvinyl chloride as gel- forming polymer. Both homogeneous gelations of the LM-phase as well as the application of an interfacial gel layer are described. In all cas es, no improvement of the stability could be observed. For both types of gelation, the initial nitrate flux decreased while the flux after 1 day of degradation was almost zero. The flux decrease is the result o f a decrease of the the diffusion rate of carrier complex as a result of the presence of the gel network and the thickness of the applied ge l layer. The absence of any stability improvement might indicate that the loss of LM-phase from these membranes is due to dissolution of car rier or membrane solvent and not a result of emulsion formation only. (C) 1997 John Wiley & Sons, Inc.