I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Kola Science Center RAS, Apatity, Russia:

L. G. Gerasimova, Chief Researcher, e-mail: gerasimova@chemy.kolasc.net.ru
A. I. Nikolaev, Deputy Director, Head of Laboratory of Chemistry and Technology of Raw Materials of Refractory Rare Metals
V. B. Petrov, Senior Researcher
Yu. G. Bychenya, Production Engineer

We investigated the decomposition of perovskite nitric acid concentrate with ammonium bifluoride as the initiating agent. Introduction of 2–3% (wt.) of NH₄HF₂ during the concentrate grinding provides a more intense degradation of mineral grains, due to the high activity of the reagent. The obtained effect leads to the rate increasing and decreasing of perovskite decomposition duration by 2.5–3 times. However, the completeness of the decomposition is not achieved. The maximum degree of the decomposition does not exceed 80%. The precipitate is basically represented by titanium hydroxide in admixture with hydroxides of niobium, tantalum and iron (III). Due to the fine particles, undecomposed perovskite is distributed throughout the volume of the precipitate, complicating its separation with hydroclassification. Increasing the amount of inputed ammonium bifluoride (up to 3% (wt.)) increases the perovskite decomposition degree. It changes the ratio of the phases included in the formed precipitate. According to the data of the X-ray phase analysis of precipitates, titanium phase is represented by titanium dioxide of rutile and anatase modification, wherein the rutile content increases with increasing of ammonium bifluoride addition, which indicates its structural transformation. Calcium, thorium and rare earth elements during the interaction of concentrate with nitric acid are leached in the liquid phase, forming a stable system. The additive of fluorinecontaining component does not have a significant effect on their extraction from the concentrate.

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