Hydrometallurgy belongs to chemical metallurgy, and the whole process is mostly carried out in solution and solvent. For example, the decomposition of rare earth concentrate, the separation and extraction of rare earth oxides, rare earth compounds and single rare earth metal are all chemical separation processes such as precipitation, crystallization, redox, solvent extraction and ion exchange.
Organic solvent extraction is widely used now, which is a general process for industrial separation of high-purity single rare earth elements. Hydrometallurgical process is complex and the product purity is high, so the finished products produced by this method are widely used.
Pyrometallurgy has simple process and high productivity. Rare earth pyrometallurgy mainly includes preparation of rare earth alloy by silicothermic reduction, preparation of rare earth metal or alloy by molten salt electrolysis and preparation of rare earth alloy by metal thermal reduction. The same characteristic of pyrometallurgy is that it is produced at high temperature.
Rare earth minerals mainly exist in the earth's crust in the form of minerals, and there are three main types: rare earth minerals, as the basic constituent elements of minerals, exist in the mineral lattice in the form of ionic compounds, which constitute the necessary components of minerals. This mineral is usually called rare earth mineral.
As impurity elements of minerals, rare earth minerals are dispersed in rock-forming minerals and rare metal minerals in the form of isomorphic replacement. These minerals can be called minerals containing rare earth elements, such as apatite and fluorite, which are adsorbed on the surfaces or particles of some minerals in ionic state.
Extended data:
Rare earth is a lanthanide element in the periodic table of chemical elements (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium).
According to the similarities and differences of physical and chemical properties, it can be divided into light rare earth group (La ~ Mo), medium rare earth group (Sm ~ Dy) and heavy rare earth group (Holmium ~ Lutetium plus scandium and yttrium).
More than 250 kinds of rare earth minerals have been discovered, of which about 50 ~ 60 kinds are of industrial value. The most important rare earth minerals are bastnaesite, monazite, xenotime, ion-adsorbed rare earth minerals and Feuerite.
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