Liquid Membranes

Liquid membrane technology offers a novel membrane separation method in which the separation is affected by the solubility of the component to be separated rather than by its permeation through pores, as in conventional membrane processes. The component to be separated is extracted from the continuous phase to the surface of the liquid membrane, through which it diffuses into the interior liquid phase.

The liquid membrane can be created in an emulsion or on a stabilizing surface of a permeable support (e.g., polymer, glass, or clay) as shown in Figure 3.8.14. The advantage of an emulsion is the large specific surface.

Figure 3.8.15 is a simplified diagram of a continuous emulsion liquid extraction process. The emulsion is prepared in the first stage of the process (water in oil [W/O] emulsion) by the emulgation of the inner liquid phase I in an organic phase II. In the permeation stage, the emulsion is dispersed into the continuous phase to be treated to form a water/oil/water (W/O/W) emulsion in which the mater-

Green Coffee Beans

Green Coffee Beans

Degassing

FIG. 3.8.13 A typical supercritical extraction process for coffee decaf-feination.

Degassing

FIG. 3.8.13 A typical supercritical extraction process for coffee decaf-feination.

TABLE 3.8.3 MAIN MEMBRANE SEPARATION PROCESSES: OPERATING PRINCIPLES AND APPLICATION

Separation

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