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

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

There was carried out the modelling of counter-current extraction of zirconium by ninety-percent tributylphosphate of (from) the solution which contains 120 g/dm³ of ZrO₂, 12.6 g/dm³ of HfO₂ and 4.1 mole/dm³ of HNO₃. The countercurrent mode was carried out with introduction of HNO₃ into the centre of cascade in a quantity equivalent to a quantity of zirconium extracted to organic phase. Total content of zirconium in organic phase amount to 80–90 g/dm³ and their segregation coefficients vary in a 5–7 limit. Modelling was carried out at 6 stages of counter-current washing of organic phase saturated by zirconium and hafnium with solution containing 3.0 mole/dm³ of HNO₃ with phases proportionate as O:W = 7:1. The received zirconium extract contains <0.01% (mass.) of hafnium. Possibility of HNO₃ recirculation in cells of a counter-current cascade is examined. It is shown that at the washing stage it is possible to use the HNO3 solution with concentration of 0.1–0.5 mole/dm³ instead of 3–4 mole/dm³. The proposed process was tested on centrifugal extractors. It was shown that the system output in such a case comes to 75–100% of nominal (test) productiveness of the extractors. The zirconium and hafnium separation schematic technology diagram with extraction, washing and re-extraction stages was offered. At the first stage zirconium is extracted by tributylphosphate solution. The received organic phase is washed by solution containing 0.1–0.5 mole/dm³ of HNO₃ with phases proportionate as O:W = 7:1. It is found that being extracted from concentrated solutions, each kilo of zirconium requires 2.4 times less inserted HNO₃ per cascade.

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