Factors affecting extraction equilibrium

There are both internal factors and external factors that affect the extraction balance. The internal factors are mainly the characteristics of the extracted (or separated) object and the extractant used, and the external factors include the extraction process conditions and operating conditions.

Composition of extractant and extraction system

(1) Extractant

Extractant is the most critical factor to determine the extraction balance "extraction solvent is the heart of the solvent extraction process" thus highlighting the importance of extractant selection and determination. The general principles of extractant selection have been discussed before, and specific analysis should also be carried out from the extractor when determining the extractant for a specific extraction object. In the selection of extractant should carefully analyze the structural characteristics of the extraction object and the relationship between the structure of the extractant and its extraction performance, so as to reduce blindness, of course, further screening tests of the extractant are still necessary.

(2) diluent

The dielectric constant of the diluent is related to the extraction distribution of the vegetable. For most extractants, the extraction capacity decreases with the increase of the dielectric constant of the diluent, but the opposite is true for the extractants of the subcompounds. There are two main factors of action of diluent: one is the interaction between diluent molecules and extractant molecules; Another point is the interaction between the diluent molecules and the raffinate molecules. If the diluent molecules interact with the extractant and the extract molecules in the same way, the effects of the diluent on the extraction distribution balance is not small, on the contrary, the effect will be very significant. It should be noted that the composition of the diluent has an effect on the extraction distribution, and the relative content of aromatics and alkanes in the diluent has a more significant effect on the metal extraction.

(3) The concentration of extractant

Obviously, the extraction distribution of the extract will increase with the increase of the extractant concentration in the organic phase, but the extractant concentration must be determined by comprehensive consideration of various factors.

(4) Saturation of extractant

In the process of reactive extraction, due to the combination of extracted molecules and extraction molecules, the free molecules of the extractant are reduced, resulting in the decline of extraction ability. In the extraction of antibiotics due to their low concentration in the feed solution.