Liquid–liquid extraction (LLE) also known as solvent extraction, is a method to separate compounds based on their relative solubility in two different immiscible liquids, usually water and an organic solvent.
It consists of transferring one (or more) solute(s) contained in a feed solution to another immiscible liquid (solvent).
In a liquid-liquid extraction unit, a liquid stream (carrier) containing the component(s) to be recovered (solute) is fed into an extractor, where it contacts a solvent. The two liquids must be immiscible or only slightly miscible; this allows them to form a dispersion, with one liquid dispersed as droplets in the other.
Liquid–liquid extraction is a separation process which is based on the different distribution of the components to be separated between two liquid phases.
It depends on the mass transfer of the component to be extracted from a first liquid phase to a second one. Liquid–liquid extraction is the separation method of choice where distillation fails, e.g., for azeotropic mixtures or temperature-sensitive components.
Type of liquid-liquid extraction methods: