Solvent extraction is
employed to separate compounds based on the differences in the relative solubilities in two immiscible
liquids. More conveniently, it can be described as the separation/extraction of
a substance from a mixture by preferentially dissolving the substance to
be extracted in a suitable solvent. It is usually chosen when a soluble compound needs to be separated from an
insoluble compound or a complex matrix. LLE or Solvent Extraction is widely used in the production of fine organic
compounds, the processing of perfumes, the production of vegetable oils and
biodiesel, and in related industries. Immiscible
liquids refers to liquids do not mix and instead separate into layers. These properties
are utilized for separation
of Organic
compounds that exhibit physical property of
greater solubility in organic solvents, and these solvents
are often found to be immiscible in water. These
Organic compounds can be easily be extracted in aqueous
form by the addition of benzene, chloroform etc. These
are then collected after they settle into two layers and
the non-aqueous layer is removed. After
distillation the purified compound is obtained.
Commonly referred to as Liquid–liquid extraction
(LLE), Solvent Extraction is preferred when
substances like edible oils need to be separated or
extracted based on the differences in relative
solubilities in two different immiscible liquids. The transfer occurs due
to different chemical potentials. This occurs when the overall system of protons and
electrons constituting the solutes and the solvents have
greater stability of configuration and
exhibit lower free energy after completion. The solvent
thus produced then is obviously enriched in the solute(s) and is referred
to as extract. The depleted feed solutions usually termed as the definite. The solvent extraction plants are used where oil is
extracted from oil seeds like soybean, sunflower, cottonseed, other oil seeds
and oil cakes like mustard cake, groundnut cake and rice bran. In such solvent extraction, it's
advantageous to do extraction in successive stages using smaller lots of
solvents rather doing extraction once using the entire lot.
