Liquid membrane separation consists of two steps: extraction and counter-extraction, but the extraction and counter-extraction in solvent extraction are carried out in steps, and the coupling between them is realized by external equipment; whereas the extraction and counter-extraction in liquid membrane separation process occur on both sides of the liquid membrane interface, and the extraction and counter-extraction are carried out simultaneously, with the solute extracted from the feed liquid phase into the membrane phase and diffused to the other side of the membrane phase, and then counter-extracted into the receiving phase. The extraction and counter-extraction are completed within one stage, thus realizing the "internal coupling" of extraction and counter-extraction. The "internal coupling" of liquid membrane transfer breaks the chemical equilibrium inherent to solvent extraction, so the liquid membrane separation process is a non-equilibrium mass transfer process. Liquid membrane separation also combines the advantages of effective removal of matrix interference in the dialysis process, so the liquid membrane can achieve both separation and concentration effects.

Characteristics of Liquid Membrane Separation

1. Liquid membrane separation is a non-equilibrium mass transfer process, extraction and counter-extraction can be carried out simultaneously to achieve separation and concentration at the same time.
2. The diffusion coefficient in liquid membrane is larger than that of solid membrane, and different carriers can be added according to different separation systems, and in some cases, convective diffusion exists in liquid membrane, so even solid membrane with thickness of micron level, its mass transfer rate is not comparable to that of liquid membrane.
3. The inner phase and outer phase are mutually or partially soluble, while they are not mutually soluble with the membrane phase, which can reduce the loss of membrane phase.
4. Low reagent consumption, the mobile carrier fits the solute on one side of the membrane and releases the solute on the other side of the membrane.
5. Good selectivity. Solid membranes tend to be selective only for the separation of a certain class of ions or molecules, and have poor performance for the separation of other specific ions or molecules.

Liquid Membrane Separation Testing

BOC Sciences offers specialized liquid membrane separation testing for the separation of natural products. The liquid membrane process has the advantages of high separation speed, high efficiency, good selectivity, simple equipment, and small footprint, making it an advantage in extracting and concentrating solutes from dilute solutions.

Liquid Membrane Preparation

Preparation of emulsion membrane - The emulsion membrane preparation equipment is a stirring tank with thermostat control and speed measurement. After controlling the temperature to a specified value, membrane solvent, surfactant and other components are added to the stirring tank, and carrier is added to make a certain ratio of membrane phase solution, then stirred, a certain amount of internal phase reagent is added, and the emulsion membrane is made by high-speed stirring.

Preparation of support liquid film - The most common method is to saturate a porous polymer membrane with a solution of dissolved carrier.

Liquid Film Extraction

Emulsion membrane - The emulsion is mixed thoroughly with the separated liquid to extract the components to be separated into the inner phase of the membrane, and then the emulsion is separated from the treated liquid using extraction equipment such as a mixing clarifier and a turret.

Support liquid membrane - The separation process is similar to the general solid membrane, but the emulsion making, extraction and emulsion breaking cannot be cyclic, and the liquid membrane phase will be lost due to dissolution and loss during the operation, so the liquid membrane should be renewed regularly.

Breaking the Emulsion

The purpose of breaking the emulsion is to break the emulsion droplets and separate the membrane phase and the internal phase, the membrane phase is used to recycle the emulsion, and the internal phase reagents can be further recovered or reprocessed.

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