Designing an extractor is usually a fine balance between capital and operating costs. Also, the solvent should be easily recoverable for recycle. The desired properties of solvents are a high distribution coefficient, good selectivity towards solute and little or no miscibility with feed solution.
Selectivity can be defined as the ability of the solvent to pick up the desired component in the feed as compared to other components. The distribution coefficient (m) or partition coefficient for a component (A) is defined as the ratio of concentration of a A in extract phase to that in raffinate phase.
The distribution coefficient and selectivity are the most important parameters that govern solvent selection. Once the functional group is identified, possible solvents can be screened in the laboratory. Robbins (1) presents a table showing Organic-Group interactions from which one can identify the desired functional group(s) in the solvent for any given solute. Solvents differ in their extraction capabilities depending on their own and the solute's chemical structure.
0 kommentar(er)
