How does solvent extraction works?

1 Answer
Oct 29, 2015

Answer:

Solvent extraction partitions a solute across two immiscible solvents; typically water and diethyl ether (this is one such example; I could use water and methylene chloride, or water and hexanes).

Explanation:

Solvent extraction relies on the relative solubility of a solute in the 2 immiscible solvents. Given the above system, uncharged, organic species will be more soluble in the organic phase, and ionic substances will remain in the aqueous phase.

Given a couple of extractions with fresh solvent, the aqueous phase will retain little if any organic solute. Such solute has been concentrated (partitioned!) in the organic phase. Typically the organic phase is quite volatile: compare the volatility of diethyl ether versus water. The diethyl ether, being quite volatile, may be removed by suction, and the crude organic solute may thus be concentrated and purified (by recrystallization or distillation).