Physico-Chemical Aspects of Cryolite Production Technology from Kaolin Clays of the Chashma-Sang Deposit and its Experimental Tests

Abstract

The purpose of the article is to study the physico-chemical and technological aspects of obtaining desulfated cryolite from an aluminum sulfate solution produced during the sulfation of kaolin clays from the Chashma-Sang deposit. Experiments have been carried out to obtain cryolite from an aluminum sulfate solution and test it in industrial conditions. It was found that, at room temperature for 15 minutes and with a dosage of sodium fluoride up to 100 % of the stoichiometric amount, the extraction rate of cryolite reaches more than 96 %. However, relatively fine particles of cryolite are formed at room temperature, which prolongs the filtration process and causes the absorption of a significant amount of sodium sulfate. This makes filtration impractical for practical use. Therefore, it is recommended that filtration be carried out at temperatures above 85 °C to avoid the formation of fine particles and reduce the amount of absorbed sodium sulfate. The filtration process was investigated using a conventional laboratory filtration apparatus and a vacuum-assisted filtration system, depending on temperature, in order to determine the filtration rate and desulphurization of cryolite. It was found that when employing a vacuum filtration apparatus and increasing the temperature between 25 and 85 °C, the removal of sodium sulphate from the cryolite composition increased significantly (from 11.2 % to 0). The cryolite filtration time was reduced from 34 to 10 minutes. According to the results of chemical analysis, the parameters of the resulting desulphated cryolite met the regulatory requirements specified in GOST 10561--80 for artificial technical cryolite. X-ray diffraction analysis determined that the product resulting from the interaction of aluminium sulfate and sodium fluoride solutions corresponded to the mineral cryolite (Na₃AlF₆), which was confirmed by chemical analysis results. After filtration of the cryolite, the liquid component was evaporated in order to obtain primarily sodium hydrosulfate and sulfate (as confirmed by X-ray diffraction analysis)

The work was carried out with the financial support of JSC "Tajik Aluminium Company"

Please cite this article in English as:

Naimov N.A., Mirsaidov U.M., Murodiyon A., et al. Physico-chemical aspects of cryolite production technology from kaolin clays of the Chashma-Sang deposit and its experimental tests. Herald of the Bauman Moscow State Technical University, Series Natural Sciences, 2024, no. 6 (117), pp. 88--102 (in Russ.). EDN: ACLYGP

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