Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 2

The decomposition of eudialyte concentrate was studied by means of sorption conversion in the 2 mass % solution of sulphuric acid. It was shown that eudialyte decomposes at a temperature of 80 ^оC with the formation of silica gel, while silica sol is formed at 20 ^оC. The efficiency of the sorption of refractory rare elements by the sorbent in the mode of silica sol formation increased in comparison with the mode of silica gel formation from 52.5 to 89.4 for zirconium, from 60.1 to 89. 2 for hafnium, from 7.4 to 85.1 for niobium, from 0 to 67.1 for tantalum, from 27.6 to 80 for titanium, respectively, with the provision of a high degree of extraction of rare earth elements (REE) - 82.9 %, including REE of yttrium and medium groups up to 86-89 %. The major part of the losses of niobium, tantalum, titanium and REE is determined by their inclusion in loparite and other accessory minerals that are untreatable under the studied conditions. It is assumed that a substantial increase in the sorption of rare elements of IV and V groups at 20 ^оC (in comparison with the results obtained at 80 ^оC) is due not only to the formation of silica sol but also to a decrease in the hydrolysis of the cations of these metals with the formation of their forms that are not sorbed by the sulphocationite. The features of decomposition of the eudialyte concentrate by the low-concentrated solutions of nitric and sulphuric acids were compared. The reasons providing the formation of silica sol during the low-temperature sulphuric decomposition of eudialyte are discussed. It is stressed that the studied method may be the basis of an efficient technology of eudialyte concentrate processing because the application of this method results in a decrease in acid consumption by a factor of 3-5 in comparison with traditional acid procedures. As a consequence, the amount of liquid wastes subjected to utilization is reduced, the effective specific radioactivity of the silica residue and the consumption of energy resources decrease.