Liquid Membrane Processes:

The procedure as well as the mechanism included in separation using liquid membranes is briefly outlined before. As it is through now familiar, a membrane is easy a barrier among two phases and if one elements of a mixture moves by the membrane faster than the other, separation is accomplished. A membrane is essentially described on its separating performance and not necessarily it should be a solid. Liquids which are immiscible along with the source (feed) and receiving (product) phases could also be used as membranes. Different solutes will have different solubilities and diffusion coefficients in a liquid. A product of the diffusivity and the solubility is called as the permeability coefficient that is proportional to the solute flux. The differences in the permeability coefficients generate a separation among solutes at constant driving force (concentration difference). Since the diffusion coefficients in liquids are classically orders of magnitude higher than in solid matrices, a larger solute flux could be acquired with liquid membranes. Further, the solute flux could be enhanced through adding a nonvolatile complexing agent (carrier) to the liquid membrane. This carrier could selectively and reversibly react along with the solute. This reversible reaction gives a means of enhancing the solute flux and improving the selectivity at the similar time.

Liquid membranes are encountered within three general configurations. In a bulk liquid membrane (BLM), an associative thick layer of immiscible liquid is used to separate the source and the receiving phases. To gives thinner liquid membrane, the liquid could be impregnated in the pores of a microporous membrane. This configuration is known as an immobilised or supported liquid membrane (ILM or SLM). In the third configuration that possesses the largest interfacial areas, the getting phase is emulsified in an immiscible liquid membrane. The emulsion liquid membrane (ELM) is also called as liquid surfactant membrane. The emulsion liquid membrane is then dispersed in the feed solution and the solute transport takes place from the feed phase to the internal getting phase.