Solvent extraction has always proved itself very helpful as a recovery method for many
components. It is a method of separating compounds on the basis of their solubility in two
different immiscible liquids like water and organic compound. We can also say that it's a
method of separating a compound which is soluble in an immiscible or a partially
immiscible liquid which gives you a desired compound either in the form of a solute or in a
form of a residue. This forms different layers which facilitates the separation of
The simplest solvent extraction
examples may be derived from
water and organic compounds.
For example: Benzene is non
polar and is immiscible in water
as the polarity of water is very
high. So, if we want to separate
benzene from a liquid which
contains a component that
dissolves in water, then we can
mix it with water and the
separated layer will be benzene.
Solvent extraction is also widely used in the petrochemical refining
industries. Extracted petroleum has lots of impurities and therefore it
cannot be used for any purposes. Hence, this extraction is used to purify the
product. Special solvent is introduced in the petroleum which reacts with
the impurities and either settles them down or keep them floating. Then the
impurities can be easily separated and pure petroleum is further packed for
The solvent should be able to dissolve at least one component to a large
extent than the rest of the components in the mixture.
The reaction taking place should be stable and irreversible. Reversible
reactions can bring back the dissolved components in their previous form
and the extraction will not be completed successfully.
The compound formed after the reaction should be easily separated from
the extracted compound so that it can be reused.
The density of the compound should be different from the required
component to help the separation readily.
It should be inexpensive and cost-effective.
The solvent should not be toxic or corrosive as it can harm the extraction
Condition under which the reaction or the extraction process takes place
also affects the separation. Temperature and pH play a very important role
in separating components. So it is very necessary to maintain the
temperature and pH of the compound during the extraction process.
Pressure does not affect the reaction much, as most of the solvent
extractions are carried out under the atmospheric pressure. Other factors
may be precipitation of solids, vapor pressure, etc. Apart from these factors,
residence time is also important in the reactions like metals separation or
short life components like antibiotics.
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