Supported liquid membranes driving force

Figure 20.2 Different types of membrane contactors, (a) stripper/ scrubber, driving force difference of concentration (b) liquid-liquid extractors, driving force difference of concentration (c) removal of volatiles/gases from liquids, driving force difference of partial pressures (d) direct contact membrane distillation, driving force difference of partial pressures (e) supported liquid membranes, driving force difference of concentrations.

Facihtated transport can take place in both hquid and polymer membranes. Liquid membranes combine extraction and stripping, which are generally carried out in two separate steps in conventional processes such as solvent extraction, into one step. A one-step liquid membrane process provides the maximum driving force for the separation of a target species, leading to the best cleanup and recovery of the species (Ho and Sirkar, 1992). There are two types of hquid membranes (1) emulsion liquid membranes (ELMs) and (2) supported liquid membranes (SLMs). ELMs, first invented by Li (1968), have been reviewed extensively (Ho and Li, 1992 Ho and Sirkar, 1992). 

Vaccum membrane distillation, such as any membrane distillation process, is a thermally driven process in which a feed solution is bought into contact with one side of a microporous membrane and a vacuum is created on the opposite side to create a driving force for transmembrane flux (Figure 19.8). The microporous membrane only acts as a support for a vapor-liquid interface, and does not affect the selectivity associated with the vapor-liquid equilibrium [76]. 

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