Preparation of High-Purity Magnesium from Electrolytically Produced Crude Magnesium via Vacuum Distillation

Metallic Mg is an important strategic metal and its properties are greatly affected by impurities. Silicothermic reduction and electrolysis are the most used approaches to prepare metallic Mg. The products of these processes need to be further refined to obtain high-purity Mg metal. However, previous research has mainly focused on refining the crude Mg (CM) produced via silicothermic reduction, whereas no in-depth investigations have been conducted on refining the CM produced via electrolysis. Here, vacuum distillation was used to refine electrolytically produced CM. The content and morphological characteristics of the impurity elements in CM were studied via glow discharge mass spectrometry, mineral dissociation analysis, and electron probe microanalysis. The effect of different distillation temperatures and times on the quality of the refined Mg was investigated. The results show that the main impurity elements are Al, Fe, Si, Ti, Cr, S, Cl, and Ni. The content of impurities, such as Si, Al, Fe, Ni, Ti, and Cr, in the refined Mg is significantly reduced at a temperature of 1023 K and a time of 120 min, and the purity of the refined Mg reaches 99.99%, which meets the Mg9999 national standard for primary Mg ingots in China (GB/3499-2011).