Extraction

Extraction is a separation process used to separate a substance from a mixture by selectively distributing it into one phase (the extract) based on solubility differences. It is widely used to isolate, purify, or concentrate compounds. In its simplest form, an immiscible solvent is added to a solution, the target species partitions between the two liquid phases, and the phases are separated.

In chemical engineering, common extraction methods include liquid-liquid extraction, solid-phase extraction, and accelerated solvent extraction. Liquid-liquid extraction relies on two immiscible liquids and the partition coefficient of solute between them, followed by solvent recovery and reuse. Solid-phase extraction uses a porous solid sorbent to retain analytes while washing away impurities; the target compounds are later eluted with a suitable solvent. Soxhlet extraction offers continuous contact between solid samples and fresh solvent, efficient for solids with low solubility. More recent approaches include supercritical fluid extraction, typically using supercritical CO2, which enables efficient extraction with minimal solvent residues and tunable solvating power.

Other contexts: in geology and economics, resource extraction refers to harvesting or removing raw materials such as minerals, oil, and gas from the earth, with environmental and social impacts. In information processing, data extraction is the automatic retrieval of structured data from unstructured text or documents, often as part of data mining or knowledge engineering.

Applications span pharmaceuticals, food and beverage, cosmetics, environmental monitoring, and laboratory analysis. Key considerations include solvent choice, selectivity, yield, energy use, waste handling, and safety. Advances seek greener solvents, efficient phase separation, and automation.