Home – Home – Jornals – Chemistry for Sustainable Development 2023 number 4

The results of studies on the development of technologies for the utilisation of silica sols formed during eudialyte concentrate processing by means of sorption conversion are presented. As promising areas, the following directions have been proposed and studied: additional extraction of valuable metals from silica sols by sorption with sulphocationite; silica sol separation into silica-enriched silica gel and silica-depleted acid solution by successive freezing and thawing of the initial silica sol; the use of silica contained in silica sols to obtain wollastonite. The percentage of rare metals that can be absorbed by sulphocationite from silica sols obtained at a temperature of 80°C - the optimum temperature for the decomposition of eudialyte concentrate by sorption conversion - is found to be (%) 58.6-70.3 Ti, 46-50 Zr, 24.7-29.9 Hf, 23.5-34.7 Nb, while sodium remains in silica sol. The low degree of filling of the sorption exchange capacity of the sulphonic cation exchanger allows it to be additionally saturated in the process of sorption conversion. It is shown that the concentration of SiO₂ reached 33.0 g/L in silica gels obtained by successive freezing and thawing of silica sols. The specific effective radioactivity of silica gels is low, which allows them to be used in the production of civil building materials. Acid solutions depleted in silica, the volume of which was 72.5-81.2 % of the volume of the initial silica sols, contain up to (%) 78.3 Ti, 56 Zr, 45.1 Hf, 76.4 Nb, 92.2 Na, 100 Th, 100 U, and only 1.1-3.6 SiO₂. Such solutions after additional strengthening are suitable for reuse for the decomposition of eudialyte concentrate. The possibility of obtaining wollastonite from silica sol based on nitric acid solution without the use of autoclave equipment has been experimentally proven. The ways of regeneration of the mother liquor obtained after precipitation of the wollastonite precursor are discussed.