Separation and purification of rare earth elements are selectively carried out by utilizing the distribution ratio of certain components in the aqueous phase in the organic phase. One of the important methods for the separation and purification of rare earth elements. The continuous organic phase formed by the extractant and the organic solvent is brought into sufficient contact with the aqueous phase containing the separated rare earth elements without being miscible with each other (ie, mixed thoroughly with a clear solution) so that the rare earth components are not equal in both phases Distribution of rare earth elements to achieve the rare earth elements of the solvent extraction process and Purification purposes.
The process includes the selection of extraction system, the selection of extractors and extraction methods, the determination of extraction and separation process conditions, the implementation of extraction and stripping processes, and the post-treatment of various solutions after separation (see Solvent Extraction). Extraction of a single-stage and cascade of points, in order to obtain high-purity products are usually cascaded extraction. Cascade extraction there are cross-flow, co-flow, countercurrent, fractionation, reflux and other forms. Since the 1970s rare earth extraction and separation to fractional extraction mainly supplemented by other processes. Extractant, extraction system and process conditions are mainly determined by the separation of A, B two components (or two elements) separation factor βA / B size:
Where DA is the partition ratio of component A in two phases; DB is the partition ratio of component B in two phases, CA (0), CA (a) is the concentration of component A in equilibrium organic and aqueous phases, CB (0), CB (a) is the concentration of the B component in the equilibrated organic and aqueous phases. The size of βA / B indicates the advantages and disadvantages of the separation of A and B components. The larger the βA / B value, the better the separation effect, ie, the higher the selectivity of the extractant. If DA = DB, βA / B = 1, then the two components of A and B can not be separated by this extraction system. The size of β is related to the atomic number of rare earth elements and the extraction system.
The application of new extractants and advances in extraction theory and process research all strongly promote the development of rare earth separation and purification technologies. Solvent extraction technology has become the main means of separation and purification of rare earth elements, with which it has been possible to separate and purify each rare earth element from the raw materials of a variety of rare earth components. Cascade extraction theory provides the theoretical basis for the optimal design of the extraction process and has been widely used in the production of rare earth extraction and separation.
Article from NdFeB Industry Network