Liquid Membranes
A liquid membrane (LM) is literally a membrane made of liquid. It consists of a liquid phase (e.g. a thin oil film) existing either in supported or unsupported form that serves as a membrane barrier between two phases of aqueous solutions or gas mixtures.
One of the benefits of using a liquid membrane is that LMs are highly selective, and, with the use of carriers for the transport mechanism, specific molecular recognition can be achieved. LMs are relatively high in efficiency, and as such, are being looked into for industrial applications. The major problem restricting widespread application is stability: liquid membranes require stability in order to be effective, and if they are pushed out of the pores or ruptured in some way due to pressure differentials or turbulence, then they just do not work.
There are 2 basic types of liquid membranes - the Emulsion Liquid Membrane (ELM) and the Immobilized Liquid Membrane (ILM), also called a Supported Liquid Membrane.
An ELM can be visualized as consisting of a "bubble within a bubble". The inner most bubble is the receiving phase, and the outer bubble is the separation "skin" containing the carriers. Anything outside the bubble is the source phase. In an ELM set-up there would be huge numbers of these bubbles, such as shown schematically in the Figure