Saint-Petersburg Mining University, Saint-Petersburg, Russia:

V. N. Brichkin, Head of Metallurgy Department, Doctor of Technical Sciences, e-mail: Brichkin_VN@ pers.spmi.ru
A. T. Fedorov, Postgraduate Student of the Department of Metallurgy, e-mail: s185005@stud.spmi.ru

Target processing of aluminum ores with increased potassium content is well known in the world practice and at different stages of development of alumina production technology was associated with the use of the most available and preferable raw materials, including leucites, alunites, nepheline syenites and close to them urtite minerals. Currently, we can talk about a renaissance of interest in potassium-containing raw materials due to the gradual depletion of reserves and the impoverishment of traditional aluminum-containing raw materials against the high demand for and cost of the soda-potash products, potassium fertilizers, aluminum hydroxide, alumina, and materials based on them. This study used theoretical and experimental methods of research, including calculations of the equilibrium composition of aluminate solutions in the Na₂O – K₂O – Al₂O₃ – H₂O system based on the additivity principle and experimental study of indicators and regularities of hydrolysis of aluminate solutions on aluminum hydroxide seed (decomposition), depending on the mole fraction of K2O in alkaline aluminate solution. It was found that the degree of decomposition of aluminate solutions in the Na₂O – K₂O – Al₂O₃ – H2O system has a violation in the monotonicity of its change with the appearance of a special point at the mole fraction of K₂O equal to 0.33, the presence of which can be explained by a change in the process mechanism due to a change in the ionic composition of the aluminate solution. The correlation between the degree of decomposition of aluminate solutions and the value of the average median particle diameter of the resulting aluminum hydroxide precipitate was shown, indicating a close relationship between the growth processes of crystallization and the hydrolytic decomposition mechanism in general, as well as their dependence on the ionic composition of aluminate solutions. The effect of transition of supersaturated (metastable) aluminate solutions into the area of unsaturated compositions has been established, which is of theoretical significance for understanding the mechanism of decomposition of potassium-bearing aluminate solutions and of practical importance for creating an effective technological cycle for the processing of aluminum-bearing raw materials based on the Na₂O – K₂O – Al₂O₃ – H₂O system.

The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577-П of April 28 2021 of grant for fundamental scientific research and exploratory scientific research.

1. Bronevoi V. А., Lankin V. P. State and Possible Directions of Development of Raw Material Base of Russia Aluminium Industry. Tsvetnye Metally. 2001. No. 3. pp. 49–54.
2. Laikishev N. P., Layner Y. А., Rokhlin L. L. Development of Scientific Basis and Technology to Process Aluminium-Containing Feedstock and Materials, Based on Aluminium, at the Baikov Institute of Metallurgy and Materials, RAS. Tsvetnye Metally. 2001. No. 12. pp. 69–74.
3. Syziakov V. M., Nasyrov G. Z. Efficient Methods for Complete Processing of Non-Bauxite Aluminium-Containing Raw Materials. Tsvetnye Metally. 2001. No. 12. pp. 63–69.
4. Nasyrov G. Z., Pivovarov V. V., Dantsig S. Ya., Nemets N. V., Lipin V. A., Golyshev V. A. New Technologies for Complex Processing of Alkali Aluminosilicate and Alunite Ores Into Alumina and Chemical Products. Tsvetnye Metally. 1997. No. 4. pp. 32–35.
5. Alekseev A. I. Complex Processing of Apatite-Nepheline Ores Based on the Creation of Closed-Loop Process flow Sheets. Journal of Mining Institute. 2015. Vol. 215. pp. 75–83.
6. Sizyakov V. M. Chemical and Technological Mechanisms of a Alkaline Aluminum Silicates Sintering and a Hydrochemical Sinter Processing. Journal of Mining Institute. 2016. Vol. 217. pp. 102–112.
7. Xie Yanli. Zhao Qun, Lu Zhenan, Bi Shiwen. Study on the Effect of K₂O on Seed Precipitation in Sodium Aluminate Liquors. Light Metals. 2006. pp. 159–163.
8. Xie Yanli, Zhao Qun, Lu Zhenan, Bi Shiwen. Study on Negative Effect of K₂O on Precipitation of Gibbsite. Light Metals. 2005. P. 219–222.
9. Teslia V. G., Volokhov Y. А., Sizyakov V. M. Effect of the Ionic Environment Of Alkaline Solutions Of Sodium And Potassium Aluminate On The Deposition Kinetics Of Aluminum Hydroxide. Russian Journal of Applied Chemistry. 1984. Vol. 591. pp. 534–539.
10. Anikeev V. I., Ananieva N. N., Kotlyagin Е. G., Yeremeev D. N. Agglomeration of Aluminum Hydroxide Crystals During Decomposition of Aluminate Solution Obtained During Nepheline Processing. Tsvetnaya Metallurgiya. 2003. No. 3. pp. 27–31.
11. Teslia V. G., Siziakov V. M., Volokhov Y. A. Influence and Mechanism of Different Impurities Action on to the Process of Al(Oh)₃ Crystallization From the Aluminate Liquors. Travaux. ICSOBA. Athens. 1999. Vol. 26, Iss. 30. pp. 157–167.
12. Siziakov V. M., Smirnov М. N., Panasko G. А. Obtaining Aluminum Hydroxide by Twisting of Aluminate Solutions in Complex Processing of Nepheline-Containing Raw Materials by Sintering Method. Trudy VAMI. 1978. No. 100. pp. 84–90.
13. Alekseev A. I., Kononchuk O. O., Goncharova M. V., Hippmann S., Bertau M. Recovery of CaCO₃ from the Nepheline Sludge of Alumina Production. Chemie Ingenieur Technik. No. 4, 2019. pp. 494–501.
14. Skaarup S. B., Gordeev Y. A., Volkov V. V. Dry Sintering of Nepheline – A New More Energy Efficient Technology. Light Metals. 2014. pp. 111–116.
15. 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.
16. Sizyakov V. M., Bazhin V. Yu., Sizyakova E. V. Investigation of Possibility for Using Nephelinelime Mixtures to Replace Bauxite. Metallurgist. 2015. No. 11. pp. 28–35.
17. Rimkevich V. S., Pushkin A. A., Girenko I. V. Complex Processing of Alkaline Aluminosilicates by the Fluoride-Ammonium Method. Obogashchenie Rud. 2020. No. 4. pp. 27–34. DOI: 10.17580/or.2020.04.05
18. Gorbunova Ye. S., Zakharov V. I., Alishkin А. R. All-Round Chemical-Dressing Technology for Processing of Rischorrites. Obogashchenie Rud. 2011. No. 4. pp. 12–16.
19. Kozyreva L. V. Korobeinikov А. N., Menshikov Y. P. New Variety of Ultracalium Rocks in the Khibiny Massif. New in the Mineralogy of the Karelo-Kolskiy Region. Petrozavodsk: KarNC USSR Academy of Sciences, 1990. pp. 116–129.
20. Antropova I. G., Alekseeva E. N., Budaeva A. D., Dorzhieva O. U. Thermochemical Concentration of Ultra-Potassium Aluminosilicate Raw Materials (Synnyrite) Using Magnesium-Containing Additives of Natural Origin. Obogashchenie Rud. 2018. No. 6. pp. 14–19. DOI: 10.17580/or.2018.06.03
21. Antropova I. G., Alekseeva E. N., Budaeva A. D. Integrated Processing Method for Synnyrite with Production of Alumina and Potassium Sulfate. Journal of Mining Science. 2019. Vol. 55. No. 6. pp. 1007–1012.
22. Xi Ma, Jing Yang, Hongwen Ma, Changjiang Liu. Hydrothermal Extraction of Potassium from Potassic Quartz Syenite and Preparation of Aluminum Hydroxide. International Journal of Mineral Processing. 2016. Vol. 147. pp. 10–17.

23. Shuangqing Su, Hongwen Ma, Xiuyun Chuan, Biya Cai. Preparation of Potassium Sulfate and Zeolite NaA from K-Feldspar by a Novel Hydrothermal Process. International Journal of Mineral Processing. 2016. Vol. 155. pp. 130–135.
24. Kitler I. N., Lainer Y. А. Solubility Isotherms in the Na₂O – K₂O – Al₂O₃ – H₂O System at 20, 60 and 95^о. Proceedings of Baikov Institute of Metallurgy and Materials Science, USSR Academy of Sciences. Мoscow: Nauka, 1967. pp. 191–194.
25. Chizhikov D. М., Kitler I. N., Lainer Y. А. Solubility Isotherms of the К₂O – Аl₂O₃ – Н₂O System. Proceedings of the Third All-Union Conference on Chemistry and Technology of Alumina. Erevan: NTI SNH, 1964. pp. 333–342.
26. Leiteisen М. G., Vinogradova Т. I. Calculated Density of Sodium-Potassium Aluminate-Alkali Solutions at Temperature 25 ^оС. Proizvodstvo glinozema. Trudy VAMI. 1975. No. 91. pp. 128–129.
27. Sipos P., Schibeci M., Peintler G., Maya P. M., Hefter G. Chemical Speciation in Concentrated Alkaline Aluminate Solutions in Sodium, Potassium and Caesium Media. Interpretation Of The Unusual Variations Of The Observed Hydroxide Activity. Dalton Transactions. 2006. Iss. 15. pp. 1858–1866.
28. Sizyakov V. M., Litvinova T. E., Brichkin V. N., Fedorov A. T. Modern Physicochemical Equilibrium Description in Na₂O – Al₂O₃ – H₂O System and its Analogues. Journal of Mining Institute. 2019. Vol. 237, Iss. 3. pp. 298–306.
29. Brichkin V. N., Litvinova T. E., Vasilyev V. V., Fedorov A. T. Calculation of the Ionic Composition of Aluminate Solutions. TRAVAUX 48, Proceedings of the 37^th International ICSOBA Conference and XXV Conference “Aluminium of Siberia”, Krasnoyarsk, Russia, 16–20 September, 2019. pp. 359–364.