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CHLORIDE PROCESSING OF THE ZIRCON PRODUCT FOR SEPARATION OF RARE-EARTH ELEMENTS

Madali Naimanbayev

Abstract

A promising source of Rare-Earth Metals (REM) is the mine refuses of Obukhov deposit?s zircon concentrate, which contain 3.53% of the sum of REM oxides. Chlorination is an effective method for transferring metals from crude ore to chlorides convenient for subsequent separation, purification and production of marketable products. The advantage of such method is absence of sewage and discharge of harmful substances into the atmosphere, which is an effective measure for environmental protection. The paper performs a review of existing methods of chlorination of various types of raw materials containing rare and Rare-Earth Elements using various chlorinating agents. Based on the analysis of the revealed schemes of plants for chlorination process study, a laboratory-scale plant was set up to perform experiments on zirconium intermediate stocks chlorination process in the melt, allowing to observe the temperature regime of process, as well as to collect the exhaust gases. According to X-ray diffraction analysis, it is established that the main phase of the mine refuses of zircon concentrate is ZrSiO4 zircon; titanium is present as TiO2 rutile. The presence of Fe2O3 hematite and SiO2 quartz is established. The results of thermal analysis for detection of phases containing REM are presented. Conduction of physical and chemical studies of the phase composition of the mine refuses of zircon concentrate showed that most of the Rare-Earth Metals are bound to phosphates and smaller part is bound to iron and tungsten. Based on the analysis of the scientific and technical literature, alkali-metal chlorides (potassium chloride and ammonium chloride), a mixture of alkali and alkaline-earth metal chlorides (carnallite) were chosen as the chlorinating agent. Usage of carnallite as a chlorinator at a process temperature of 750°C allow to achieve an increase in degree of chlorination compared with use of potassium chloride, from 18.13% to 44.11%, and to reduce losses of the REM with exhaust gases. The study of chlorination process of zirconium concentrate mine refuses with various chlorinating agents showed that the carnallite is optimum chlorinator, which provides high process indices.

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DOI resolver: doi.org/10.5593/sgem2019/1.3/s04.095

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