National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Moscow, Russia:

A. V. Valkov, Professor, Deputy Head of General Chemistry Chair, e-mail: ale11534@yandex.ru

This article shows the investigation of peculiarities of preparation and stability of concentrated solutions of zirconium (hafnium) nitrates, containing 100–350 g/dm3 of zirconium (hafnium) and 2–6 mol/dm³ of nitric acid. There were found the optimum conditions of concentrated nitrate solutions preparation, using initial zirconium (hafnium) salt processing by sodium or ammonium hydroxide with further dissolution in nitric acid (temperature  40–50 ^оC). The following initial solution parameters are recommended for extraction: concentration of zirconium (hafnium) oxide in water phase, equal to 150–180 g/dm³; concentration of nitric acid, equal to 2–4 mol/dm³. Organic phase capacity is increased to 90 g/l, and consumption of nitric acid for preparation of initial solution is reduced by 4–5 times. There was defined the selectivity of zirconium and hafnium separation with extraction of 90–100% of tributyl phosphate. Depending on zirconium and nitric acid concentration, the separation coefficient of zirconium and hafnium is changed within 6–16. Counter-current extraction requires water phase acidification for compensation of nitric acid reduction during zirconium transition into organic phase.

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