L. M. Delitsyn, V. A. Sinelshchikov, R. V. Kulumbegov.
ABSTRACT
Despite the growing demand for rare-earth products, there are no enterprises in Russia that process natural raw materials and meet the needs of industry. The main amount of rare earth elements (REE) > 95% is purchased abroad, while the unique Tomtorskoye field is located on the territory of the Russian Federation, in which the REE content ranges from 15 to 40%. The study of phase transformations in melts of the monazite – NaF system was carried out in order to obtain data that can be used in the development of technology for processing monazite raw materials and rare earth ores of the weathering crust of the Tomtorskoye field. When melting Tomtor monocyte ores, two immiscible melts are formed: silicate and phosphate-salt, in which up to 85% of REE is concentrated. According to its physical and chemical properties, the phosphate-salt melt of the liquation melting of the ore-NaF system is almost identical to the melt of the monazite – NaF system. In the melt of the monazite – NaF system, as a result of chemical reactions, double phosphate-Na3Ln[PO4]2 and fluoride phosphate – Na2Ln[PO4]F2 are crystallized, which are easily dissolved in a weak solution of nitric acid. Oxalates and REE hydroxides were obtained from nitrogen-phosphoric acid filtrates.
KEY WORDS:
salt melts, monazite, DSC analysis, double salt of REE and Na, fluoride phosphate of REE and Na, sodium fluoride, crystallization, REE oxalates, REE hydroxides
DOI: 10.31857/S0235010621050029