Liquid–liquid extraction (LLE), also known as solvent extraction or partitioning, is a separation technique used to isolate compounds or metal complexes based on their differing solubilities in two immiscible liquids, typically water and an organic solvent. In this process, the target solute transfers from the original liquid phase into the solvent phase due to favorable solubility and chemical affinity.
The efficiency of LLE depends on two key factors: solvent selection and mass transfer. An ideal solvent should selectively dissolve the desired solute, remain immiscible with the feed phase, and be easily recoverable for reuse. Proper mixing between the two phases enhances mass transfer, allowing the solute to move efficiently from one phase to another.
After extraction, the system separates into two layers: the extract (solute-rich solvent) and the raffinate (remaining feed). LLE is widely used in chemical, pharmaceutical, and environmental industries for purification and recovery processes.
