Physicochemical and Energy Impact on the Process of Leaching of a Eudialyte Concentrate

• Published in: Doklady earth sciences Vol. 505; no. 2; pp. 534 - 542
• Main Authors: Chanturiya, V. A., Minenko, V. G., Samusev, A. L., Koporulina, E. V., Kozhevnikov, G. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-08-2022; Springer; Springer Nature B.V
• Subjects: Alkaline leaching; Aluminum; Decomposition; Earth and Environmental Science; Earth Sciences; Feldspars; Gels; Grain size; Hydrochloric acid; Hydrochloric acid leaching; Hydroxides; Leaching; Mineralogy; Minerals; Nitric acid; Nitric acids; Potassium; Pregnancy; Pregnant women; Rare earth elements; Rare earth metals; Recovery; Residence time; Silicates; Silicon; Sodium; Sodium hydroxide; Solid phases; Ultrasonic processing; Weight loss; Zirconium; silicon; eudialyte; alkaline decomposition; rare earth elements; acid leaching; kinetics; zirconium
• ISSN: 1028-334X; 1531-8354
• DOI: 10.1134/S1028334X22080062

The results of an experimental study of alkaline decomposition of eudialyte concentrate when exposed to physicochemical and energy impacts prior to the subsequent acid leaching to recover zirconium and rare earth elements (REEs) into a pregnant solution are presented. The parameters of the alkaline decomposition of the eudialyte concentrate were experimentally optimized to achieve a recovery of silicon into the solution of up to 22.9% (concentrate grain size, 63 μm; temperature, 130
o
C; residence time, six hours; sodium hydroxide concentration, 40%; solid phase fraction, 10%). The morphology of the main minerals of the eudialyte concentrate after acid and alkaline leaching is described. Potassium feldspar grains experienced the most intense alkaline leaching, which was accompanied by the enrichment of the pregnant solution in elements such as K, Al, and Si, while most of the cake particles are free from silicate gel. The possibility of intensifying the alkaline decomposition of the eudialyte concentrate through the use of ultrasonic treatment, providing an increase in the recovery of silicon by 2.5–5.3%, was established. The subsequent acid leaching of the cake left after alkaline decomposition of the eudialyte concentrate leads to a decrease in the volume of silicate gel in the pregnant solution by a factor of 1.1–1.4 from 66.5 to 61.8% (nitric acid solution) and 48.5% (hydrochloric acid) compared to conventional acid leaching. At the same time, an intensification of the dissolution process of the eudialyte concentrate is observed: the weight loss of the sample increases from 60 to 68% when using hydrochloric acid and 78.9% when using a nitric acid solution; the total recovery of Zr increases from 76.9 to 86.1 and 90.8%, of that of REEs, from 79.6 to 88.5 and 92.6%, when using hydrochloric and nitric acid, respectively.