What is the principle of extraction?

Extraction, also known as solvent extraction or liquid-liquid extraction (as distinguished from solid-liquid extraction, that is, leaching), also known as extraction (often used in petroleum refining industry). It is a mass transfer and separation process that uses liquid extractant to treat immiscible two-component or multi-component solutions to realize component separation. This is a widely used unit operation. Based on the principle of similar compatibility, there are two kinds of extraction methods: liquid-liquid extraction, in which a component in a liquid mixture is separated by a selected solvent. The solvent must be immiscible with the extracted mixed solution, have selective solubility, have good thermal stability and chemical stability, and have little toxicity and corrosiveness. For example, benzene is used to separate phenol from coal tar; Separating olefins from petroleum fractions with organic solvents; Extraction of Br2 from water with carbon tetrachloride. Solid-liquid extraction, also known as leaching, is to separate the components in the solid mixture with solvents, such as leaching sugar from beets with water; Soak soybean oil in soybean with alcohol to increase oil yield; The effective components in traditional Chinese medicine are leached with water to make fluid extract, which is called "leaching" or "leaching". Although extraction is often used in chemical experiments, its operation process does not change the chemical composition (or chemical reaction) of the extracted substance, so the extraction operation is a physical process. Extraction is one of the methods used to purify and purify compounds in organic chemistry laboratory. By extraction, the desired compound can be extracted from a solid or liquid mixture. The commonly used liquid-liquid extraction is introduced here.