An overview of the Liquid liquid Extraction Technique

Liquid liquid Extraction is a more specific term used in place of solvent extraction terminology. The solvent Extraction is a broader term which involves the extraction of solvent from one liquid medium to other liquid medium without affecting the chemical and physical properties of the targeted solvent. The process of extraction is based upon the difference in the chemical properties of the solvent present in the given sample. Whereas. The physical properties do not affect the process of extraction.

The mechanism involves contact of a solution with a solvent that is immiscible with the original solvent. The solvent is soluble on the addition of the solute in the solution which leads to the formation of two phases of a solution based upon the varying densities present in the solution. The solute having more affinity for the solvent is chosen to be medium for the separation of the solute to ensure the mass transfer from solution to the solvent. As the solute has been transferred to the solvent, further separation of the solvent and the solute will required to extract the original form of the solute.   

The design of liquid liquid extraction consists of the two input and two output streams. The two input streams consist of outlet for the feed solution and the solvent. The outlet hole will expel the separate solvent and the raffinate (solution separated from the solute). Further separation of the output stream is required to extract the pure form of the solute.

The key parameters affecting the extraction process involve operating temperature, operating pressure, feed flow rate, solvent composition, temperature and pressure of the entering streams.  To ensure an effective separation all components should be in liquid media. The extraction process largely depends on the component chemical properties. The process will be adversely affected if the components present in the solution will vaporize altogether. The process will stop if large amount of components vaporizes at the same time. The extreme temperature will affect the process. The extraction process carried at the ambient temperature and pressure is the ideal one.  An extraction column is basically of three different types.

Contacting columns are the most common liquid liquid extraction column used in industries. The column come fitted with the structured packaging material such as tray, plates or spray which enhances the surface area to mix the two solutions effectively. It operates on the counter current mechanism developed in the column to drive the extraction process.  The Structured Packings has gained a number of applications in industries like petroleum, hydrometallurgical, pharmaceutical, and nuclear industries.        

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Created on Dec 31st 1969 18:00. Viewed 0 times.

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