ANS:A - solvent extraction

Solvent extraction, also known as liquid-liquid extraction, is a separation process used to separate components from a liquid mixture based on their relative solubilities in two immiscible liquids. It is commonly used in chemical and biochemical industries for the purification of compounds, extraction of metals, and removal of impurities. The solvent extraction process typically involves the following steps:

1. Selection of Solvents: Two immiscible solvents are chosen based on their ability to selectively dissolve different components of the mixture. One solvent is typically water-immiscible (organic solvent), while the other is water-miscible (aqueous phase).
2. Contacting the Phases: The liquid mixture containing the desired component(s) is mixed or agitated with the chosen solvent(s). This creates intimate contact between the two phases, allowing for mass transfer of the solutes between the phases.
3. Partitioning of Components: Each component in the mixture partitions between the two solvent phases based on its solubility in each solvent. The component of interest (solute) transfers from one phase (the feed phase) to the other phase (the extracting phase) based on its partition coefficient, which is the ratio of its concentrations in the two phases.
4. Separation: After sufficient contact time, the two solvent phases are allowed to separate into distinct layers based on their immiscibility and differences in density. The solute of interest is now concentrated in one of the solvent phases, while the unwanted components remain in the other phase.
5. Recovery: The solvent phase containing the concentrated solute is separated from the other phase using methods such as decantation, centrifugation, or phase separation. The solute can then be recovered from the solvent phase through further processing, such as evaporation or precipitation.

Solvent extraction offers several advantages, including high selectivity, efficiency, and flexibility in process design. It can be used to separate a wide range of compounds, from organic molecules to metal ions, depending on the choice of solvents and process conditions. However, solvent extraction also has limitations, such as the need for careful solvent selection, potential environmental concerns, and the generation of waste solvents.