Purification of Magnesium Using Molten Salt

摘要

Some impurity elements, such as Fe, Cr and Ni are said to debase Mg metal in corrosion resistivity so that their level must keep very low for some purposes. Because primary product of Mg metal does not answer this criterion, the purification procedure of Mg metal are desired. The electrorefining process in molten salt should be promising for this purpose. In this study, electrochemical behaviors of Fe, Cr and Ni have been investigated in molten salt systems as a basic study on electrorefining of Mg metal. The mixture of MgCl_2, CaCl_2 and NaCl was mainly used as molten salt bath. The electrochemical behaviors of FeCl_2, CrCl_3 and NiCl_2 were examined by voltammetry, and the electrochemical dissolutions of these metals were examined. Potentio-static electrolysis was carried out at various electrolytic conditions, and the electrodeposit on the cathode and residue of the anode were analyzed. The results indicated that these elements could be eliminated from magnesium metal easily by electrorefining process in molten salts. Chemical distribution of elements between Mg metal and molten salts has been also examined to clarify the interaction between Mg metal and molten salts. The behaviors of main ingredients of molten salts were investigated, and those of some alloying elements were discussed.