National University of Science and Technology MISiS, Moscow, Russia:

V. I. Pak, Postgraduate Student, Department of Non-Ferrous Metals and Gold, e-mail: pak_vyacheslav@mail.ru
S. S. Kirov, Associate Professor, Department of Non-Ferrous Metals and Gold, Candidate of Technical Sciences, e-mail: kirovss@list.ru
O. I. Mamzurina, Department of Non-Ferrous Metals Science, e-mail: mamzur309@mail.ru
A. Yu. Nalivayko, Senior Lecturer, Department of Non-Ferrous Metals and Gold, Candidate of Technical Sciences, e-mail: nalivaiko@misis.ru

This paper examines the regularities of crystallization of aluminum chloride hexahydrate from the hydrochloric acid solutions resultant from leaching of Russian kaolin clays. This technique is based on reduced solubility of aluminium chloride combined with increased concentration of solvent attained through the introduction of hydrogen chloride gas. Values of the crystallization induction period have been determined in relation to certain processing regimes. Following a series of tests, it was found that the use of isothermal regime led to an 8-minute shorter induction period. Relationships were established between the concentrations of aluminium and chlorine in the system and the process time. Chlorine dissolution rates have been determined. They are 61% for isothermal regime, and 46% for polythermal regime. The authors looked at how different processing regimes impacted the degree of aluminum chloride hexahydrate crystallization (i.e. deposition rate). The maximum crystallization degree of 97% was attained in isothermal regime. The authors looked at how different processing regimes influenced the rate of aluminum chloride hexahydrate crystallization. A mathematical model of the AlCl₃·6H₂O crystallization was built to help predict the process efficiency when being a part of the proposed technique. The obtained data were used to calculate the process activation energy referring to aluminium chloride hexahydrate crystallization. For the given conditions, the activation energy is 6 kJ/mol, which may indicate a diffusion process.

1. Brichkin V. N., Sizyakov V. M., Oblova I. S., Fedoseev D. V. Industrial synthesis of finely-dispersed aluminum hydroxide in processing of aluminic raw materials. Tsvetnye Metally. 2018. No. 10. pp. 45–51.
2. Medvedev V. V., Akhmedov S. N., Sizyakov V. M., Lankin V. P., Kiselev A. I. Hydrogarnet-based processing of bauxites as a modern alternative to the Bayer sintering process. Tsvetnye Metally. 2003. No. 11. pp. 58–62.
3. Layner A. I., Eremin N. I., Layner Yu. A., Pevzner I. Z. Alumina industry. Moscow : Metallurgiya, 1978. 344 p.
4. Suss A. G., Damaskin A. A., Senyuta A. S., Panov A. V., Smirnov A. A. The influence of the mineral composition of low-grade aluminum ores on aluminium extraction by acid leaching. Light Metals. 2014. pp. 105–109.
5. Al-Zahrani A. A., Abdul-Majid M. H. Extraction of Alumina from Local Clays by Hydrochloric Acid Process. Journal of King Saud University – Engineering Sciences. 2009. Vol. 20, No. 2. pp. 29–41.
6. Lima P. A., Angelica R., Neves R. Dissolution kinetics of Amazonian metakaolin in hydrochloric acid. Clay Minerals. 2017. No. 1. pp. 75–82.
7. Regina O. Ajemba, Okechukwu D. Onukwuli. Kinetic Model for Ukpor Clay Dissolution in Hydrochlorlc Acid Solution. Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS). Scholarlink Research Institute Journals. 2012. No. 3. pp. 448–454.

8. Balmaev B. G., Kirov S. S., Pak V. I., Ivanov M. A. Kinetics of hightemperature hydrochloric leaching of kaolin clays of east-siberian deposits in laboratory conditions and pilot plant tests. Tsvetnye Metally. 2018. No. 3. pp. 38–45. DOI: 10.17580/tsm.2018.03.06.
9. Demopoulos G. P., Li Z., Becze L., Moldoveanu G., Cheng T. C., Harris B. New Technologies for HCl Regeneration in Chloride Hydrometallurgy. World of Metallurgy – ERZMETALL. 2008. Vol. 61, No. 2. pp. 89–98.
10. Brown C. J., Olsen D. R. Regeneration of hydrochloric acid pickle liquors by crystallization. Proceedings of the Third International Symposium on Iron Control in Hydrometallurgy held in Montreal. Montreal, Canada. 2006. pp. 831–843.
11. Shebarshova I. M., Levashova E. V., Taranin I. V., Laskov S. A., Kleshchev E. G. The practice of adopting the process of fluidized bed hydrochloric acid regeneration. Stal. 2013. No. 9. pp. 96–98.
12. Levinskiy M. I., Mazanko A. F., Novikov I. N. Chlorine hydride and hydrochloric acid. Moscow : Khimiya, 1985. 160 p.
13. Ivanov M. A., Pak V. I., Nalivayko A. Yu. et al. Potential use of the Russian high-silicon aluminium raw materials in alumina production. Bulletin of the Tomsk Polytechnic University. 2019. No. 3. pp. 93–102.
14. Guo Y., Lv H., Yang X., Cheng F. AlCl₃·6H₂O recovery from the acid leaching liquor of coal gangue by using concentrated hydrochloric inpouring. Separation and Purification Technology. 2015. Vol. 151. pp. 177–183.
15. Cheng H., Zhang J., Lv H., Guo Y., Cheng W., Zhao J., Cheng F. Separating NaCl and AlCl3·6H2O crystals from acidic solution assisted by the non-equilibrium phase diagram of AlCl₃ – NaCl – H₂O(–HCl) salt-water system at 353.15 K. Crystals. 2017. Vol. 7, Iss. 8. pp. 244–251.
16. Kogan V. B., Fridman V. M., Kafarov V. V. Reference book on solubility. Moscow – Leningrad : Izdatelstvo Akademii nauk SSSR, 1962. 1961 p.
17. Tikhonov V. N. The analytical chemistry of aluminium. Moscow : Nauka, 1971. 266 p.
18. Voldman G. M., Zelikman A. N. The theory of hydrometallurgical processes. Moscow : Intermet Inzhiniring, 2003. 464 p.
19. Balmaev B. G., Kirov S. S., Ivanov M. A., Pak V. I. Filtration process modeling for aluminium-bearing hydrochloric acid pulp. Tsvetnye Metally. 2017. No. 10. pp. 63–68. DOI: 10.17580/tsm.2017.10.07.
20. Yuan M., Qiao X., Yu J. Phase equilibria of AlCl₃ + FeCl₃ + H₂O, AlCl₃ + CaCl₂ + H₂O, and FeCl₃ + CaCl₂ + H₂O at 298.15 K. Journal of Chemical and Engineering Data. 2016. Vol. 61, Iss. 5. pp. 1749–1755.
21. Layner Yu. A. Comprehensive processing of aluminium raw materials with acids. Moscow : Nauka, 1982. 208 p.
22. Glikin A. E., Kryuchkova L. Yu., Sinay M. Yu., Gille P., Shneider J. Mass crystallization of isomorphous compounds. RMS Annual Session combined with the Fedorov Session 2012. Conference. Russian Mineralogical Society. Available at: http://www.minsoc.ru/viewreports.php?cid=988&rid=1435
23. Kekin P. A. Crystallization of calcium carbonate in industrial water systems: PhD dissertation. Moscow, 2017.
24. Burdin I. V., Poylov V. Z. The kinetics of polythermal crystallization of carnallite. Herald of Kazan Technological University. 2006. No. 3. pp. 13–19.
25. Brichkin V. N., Kurtenkov R. V., Fedoseev D. V. Kinetic regularities of hydrometallurgical processes involving a gas phase and how they influence the choice of process parameters. Proceedings of Irkutsk State Technical University. 2016. No. 3. pp. 97–104.
26. Protodiakonov M. M., Teder R. I. Methods for rational design of experiments. Moscow : Nauka, 1970. 74 p.
27. Malyshev V. P. Probabilistic-deterministic representation. Karaganda : Gylym, 1994. 370 p.
28. Lanovetskiy S. V. The physics and chemistry behind crystalline hydrates of magnesium and manganese nitrates and their oxides: Doctoral dissertation. Kazan, 2014.
29. Linnikov O. D., Rodina I. V., Grigorov I. G., Polyakov E. V. Kinetics and mechanism of spontaneous crystallization of potassium nitrate from its supersaturated aqueous solutions. Crystal Structure Theory and Applications. 2013. No. 2. pp. 16–27.