Extraction of Zirconium from Its Oxide during Electrolysis of the KF-AlF3-Al2O3-ZrO2 Melts

Zirconium is one of the widely demanded materials, while the existing methods of its production are multistage and energy-intensive. The paper proposes a method for extracting zirconium from its oxide by electrolysis of low-temperature oxide-fluoride melt KF-AlF3-Al2O3-ZrO2 with a temperature of 750 degrees C. For this purpose, the potentials for the electroreduction of zirconium and aluminum ions on a glassy carbon electrode have been determined by means of voltammetric methods. It was shown that the electroreduction of aluminum ions in the KF-AlF3-Al2O3 melt occurs at a potential more negative than -0.05 V relative to the aluminum electrode with the formation of a cathode peak in the potential range from -0.18 to -0.2 V. With the addition of 1 wt % of ZrO2, cathode current on the voltammogram begins at a potential more negative 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 the addition of ZrO2 by means of square-wave voltammetry. It has been suggested that, because of the lower bond energy, 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. At a graphite cathode potential of -0.1 and -0.3 V relative to the aluminum electrode, the electrolysis of the KF-AlF3-Al2O3-ZrO2 melt was carried out, and the elemental and phase composition of the obtained deposits was determined by X-ray phase analysis, scanning electron microscopy, and energy dispersive microanalysis. It was shown that, at a potential of -0.1 V, a deposit with 98.5-99.5 wt % zirconium can be obtained. This indicates a reliable possibility of selective extraction of zirconium by the proposed method.

Automated summary

This study proposes a method for extracting zirconium from its oxide by electrolysis, resulting in the reliable selective extraction of zirconium with high weight percentage from the KF-AlF3-Al2O3-ZrO2 melt.