Extraction of zirconium from its oxide during the electrolysis of KF–AlF₃ –Al₂O₃ –ZrO₂ melts

   Zirconium is one of the most commonly used materials, while the existing methods of its production are multi-stage and energy-intensive. The paper proposes a method for extracting zirconium from its oxide by KF–AlF₃ –Al₂O₃ –ZrO₂ low-temperature oxide-flu-oride melt electrolysis with a temperature of 750 °C. For this purpose, voltammetric methods were used to determine potentials of the electrochemical reduction of zirconium and aluminum ions on a glassy carbon electrode. It was shown that the electrochemical reduction of aluminum ions in the KF–AlF₃ –Al₂O₃ melt occurs at a more negative potential than –0.05 V relative to the aluminum electrode with the cathode peak formation in the potential range from –0.18 to –0.2 V. With the addition of 1 wt.% of ZrO₂ , cathode current growth on the voltammogram begins at a more negative potential than 0 V, and the cathode peak is formed at a potential of about –0.1 V. Similar results were observed in the study of the cathode process in the KF–AlF₃ –Al₂O₃ melt with and without ZrO₂ added by means of square wave voltammetry. It was suggested that zirconium-containing electroactive ions are discharged at a potential that is 0.05–0.08 V more positive than the discharge potential of aluminum-containing ions due to the lower bond energy. At a graphite cathode potential of –0.1 and –0.3 V relative to the aluminum electrode, the KF–AlF₃ –Al₂O₃ –ZrO₂  melt electrolysis was carried out, and the elemental and phase composition of deposits obtained was determined by X-ray phase analysis, scanning electron microscopy and energy dispersive microanalysis. It was shown that the 98.5 –99.5 wt. % zirconium deposit was obtained at a potential of –0.1 V. This indicates a reliable possibility of selective zirconium extraction using the proposed method.

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