The reagents used in extractive metallurgy of rare earths include extractant, diluent and salting-out agent.
(1) Extractant
Extractant refers to a reagent that can combine with the extract (such as metal ions) and enables the extract to be extracted into the organic phase. In the separation of rare earths, the choice of extractant is mainly determined by the extraction and separation factors of metal ions, the distribution ratio and the physical properties of the extractant itself. Commonly used rare earth extractants can be divided into oxygen-containing extractants, phosphorus extractants, amine extractants and integrated extractants according to their composition and structural characteristics.
Phenols, carboxylic acid compounds, alcohols, ether ketones, and ester compounds are all oxygen-containing extractants. The common oxygen-containing extractants in extractive metallurgy of rare earths include naphthenic acid, etc.
Phosphorus-based extractants are divided into neutral phosphorus-based extractants and acidic phosphorus-based extractants. Neutral phosphorus-based extractants are all alkyl and phosphine oxides, all of which contain phosphoryl (P-0) in their molecules. Commonly used neutral phosphorus extractants in rare earth separation are TBP, P350 and so on. The acidic phosphorus extractant is obtained by replacing three or part of the hydroxyl groups in the phosphoric acid molecule with alkyl groups and alkoxy groups to obtain alkyl phosphoric acid, alkyl phosphonic acid and alkyl phosphonate. The molecule contains an acidic OH group, which can extract rare earths by cation exchange. It also contains a P-0 group directly coordinated with the metal to coordinate with rare earth ions, so the extraction ability is particularly strong. Although both P-0 and P-O can be combined with rare earths, the latter is more capable. Typical extractants are P204, P507 and P229, among which P204 and P507 are widely used in rare earth production. The amine compounds used as extractants include primary amine, secondary amine, tertiary amine and quaternary ammonium salt, etc., and their molecular weight is required to be between 250 and 600. If the molecular weight is too low, it is soluble in water easily, and if the molecular weight is too high, the extraction capacity will be affected. Therefore, it is not suitable for molecular weight of the extraction of rare earth metallurgy to be too low or too high. The common amine extractant in the separation of rare earths is N1923, etc.
Rare earth ions are extracted by forming electrically neutral integrants. There are many types of integrative extractants. However, due to the high price of integrative agents, they are only used in analysis and are rarely used in industry.
(2) Diluent
Diluent refers to a solvent that does not chemically interact with the extract during the extraction process, but only changes the physical properties of the organic phase. It only acts as a solvent and does not change the chemical properties of the organic phase, so it is also called an emotional solvent. In fact, there are very few solvents that do not work at all. In the choice of diluent, first of all, it must be insoluble in water. In addition, the extractant is required to be highly dispersed into a solution in the diluent, and a certain degree of solubility is required to ensure the extraction capacity of the organic phase. The common diluent in rare earth separation is kerosene or sulfonated kerosene.
The separation equipment of solvent extraction method includes mixing and clarification tank, centrifugal extractor and so on.
The above shows two kinds of reagents of the extractive metallurgy of rare earths. If you have any questions and needs, please feel free to consult us.