Classification of extractants
Release time:
2023-08-04
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There are various types of extractants, and there is no unified classification method. Considering that it is a type of organic compound, it is usually divided into neutral extractants, acidic extractants, and alkaline extractants based on the proton theory according to the acidity and alkalinity of organic compounds; In addition, there is a type of extractant that is mostly proton acids and usually has the properties of chelating agents, so it is classified as chelating extractants.
Neutral organic compounds such as alcohols, ethers, ketones, esters, amides, thioethers, sulfoxides, and crown ethers are neutral extractants. In this category of esters, carboxylic esters (such as ethyl acetate) and phosphonic esters (such as tributyl phosphate) are also included, which are generally neutral in water.
Carboxylic acid, sulfonic acid, and organophosphorus (phosphonic) acid are acidic extractants that exhibit acidity in water and can ionize hydrogen ions.
Primary amine, secondary amine, tertiary amine, and quaternary amine are alkaline extractants. These organic amines can add hydrogen ions to water, indicating alkalinity. Their alkalinity is generally stronger than inorganic ammonia, while quaternary amine has strong alkalinity.
Chelating extractants are a type of organic compounds that contain two or more coordination atoms (or functional groups) in the extractant molecule, and can form a chelating ring with the central ion. The molecules of hydroxamic compounds contain both hydroxyl (- OH) and oxime group (=NOH). For example, the molecules of 8-hydroxyquinoline and its derivatives (Kelex100, etc.) contain both acidic phenolic hydroxyl groups and basic nitrogen atoms.
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