What is chelating extractant
Release time:
2023-08-04
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The chelating extractants used in hydrometallurgy are mainly acidic chelating extractants, including hydroxyketone extractants, hydroxyaldehydes extractants, and quinoline extractants.
Hydroxyl ketone extractants and hydroxyaldehyde extractants belong to the group of hydroxamic compounds. Hydroxime molecules contain hydroxyl groups (- OH) and oxime groups (=C=NOH), and due to the presence of carbon nitrogen double bonds (C=N) that cannot rotate freely in the structure of the oxime molecule, there are cis trans isomers. The two hydroxyl groups on the same side of the double bond are cis, while those on the opposite side are trans. The content of cis and trans formulas is generally around 1/7. Hydroxoxime extraction of metals is achieved through the chelation of hydroxyl oxygen atoms and oxime nitrogen atoms with metal ions. Therefore, only trans isomers can extract metal ions. In the cis isomer, two OH groups are on the same side and cannot extract metals due to the formation of intramolecular hydrogen bonds.
The hydroxyl group on the oxime benzene ring can ionize hydrogen ions and show acidity, while the hydroxyl group on the oxime group has a weak ability to ionize hydrogen ions. The acidity of hydroxyl oximes containing phenolic hydroxyl groups will be enhanced. Hydroxoxime compounds have strong chelating ability towards copper metal ions, making them extractants for copper. Lix63, Lix64N, Lix65N, Lix70N, Lix984 and other hydroxyketoxime extractants have high selectivity for copper ions and are special extractants for copper. Hydroxyoxime extractant is also a special extractant for copper, and 5-nonylsalicylaldoxime is an important extractant for this type of extractant, abbreviated as P1 or P50. Its performance in extracting copper is better than that of hydroxyketoxime extractants.
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