Liquid extraction

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Extraction

Solvent Extraction is a process that separates components in a matrix by contact with another liquid. Typical extractions include, liquid-solid extractions, liquid-liquid extractions and Supercritical extractions. Separation is based on the compounds’ physical and chemical properties. Extraction is well used within the perfume industry to separate aromatic compounds from hydrocarbon mixtures in petrochemical operations using high boiling polar solvents.

History

Solvent extraction is an old practice done for years. It is the main process in perfume development and it is also used to obtain dyes from various sources.

Modern use has made this process an essential practice in scientific laboratories. in 1872 Berthelot and Jungfleisch introduced the concept of the partition coefficient. Followed by an introduction in phase equilibrium by Gibbs. Many of these advances occurred as the chemical industry grew as well.

Further research and improvements to the process affected the commercial applications. Due to the advantages of solvent extraction various chemical treatment methods for refining coal tar products and mineral oil were replaced.

Design and Operation

Liquid-Liquid Extraction

Liquid-liquid extraction is a process for separating the components of a liquid (the feed) by contact with a second liquid phase (the solvent). The process takes advantage of differences in the chemical properties of the feed components, such as differences in polarity and hydrophobic/hydrophilic character, to separate them. Stated more precisely, the transfer of components from one phase to the other is driven by a deviation from thermodynamic equilibrium, and the equilibrium state depends on the nature of the interactions between the feed components and the solvent phase. The potential for separating the feed components is determined by differences in these interactions.

SuperCritical Extraction

Supercritical extractions are possible with the use of supercritical fluids. A supercritical fluid has a pressure and temperature above its critical point. These fluids display unique characteristics that enable then to be used as solvents. The density of these fluids are relatively high, and consequently they have high solvation power.

Separation is achieved by decreasing the pressure or increasing the temperature of the mixture that leaves the extraction column.

Solvent Selection for Liquid Extraction

Selectivity: How effective a solvent is dependent on the solution being separated and the concentration of solutes present in the solutions. The ratio of ratios, the separation factor, or selectivity, β, is analogous to the relative volatility of distillation. E and R are equilibrium phases, C and A are solutions being separated. Failed to parse (syntax error): {\displaystyle β= (wt fraction C in E )/(wt fraction A in E)/(wt fraction C in R)/(wt fraction A in R) = }

Applications

This section should discuss how the process is used in practice.

Examples

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