Due to extremely low solubility in conventional magnesium electrolyte, MgO tends to attach to cathode and causes cathodic passivation, which will dramatically lower current efficiency of magnesium electrolysis. In this paper, NdCl3 or LaCl3 was added to conventional magnesium electrolyte to increase MgO solubility. We investigated the effects of NdCl3 or LaCl3 content, the form of MgO, and temperature on the dissolution rate of MgO and on MgO solubility. MgO solubility increased with increasing MgCl2 content of CaF2 content in MgCl2 -KCL-NaCL-CaCl2-CaF2 melt, the maximum being only 0.145% by weight in the above melt with 30% MgCl2 by weight. Both MgO solubility and dissolution rate increased with increasing NdCl3 concentration in MgCl2-NaCl-KCl-NdCl3 (15% by weight) melts can reach about 3.0 wt % at 780 C. Raising temperature from 700 to 800 C can slightly increase the MgO solubility and dissolution rate. Addition of LaCl3 to the MgCl2-NaCl-KCl-CaCl2-LaCl3 melt also improved MgO solubility, but it took more time (about 60 minutes) to achieve equilibrium between MgO and LaCl3 in the melt. Formation of the stable NdOCl compound examined by XRD analysis indicated that MgO can react with NdCl3 in chloride melts.
Li, Bing; Li, Jun; Chen, Jinzhong; and Yu, Jianguo
"Solubility of MgO in chloride melts containing NdCl3 or LaCl3,"
Natural Resources and Environmental Issues:
Vol. 15, Article 43.
Available at: http://digitalcommons.usu.edu/nrei/vol15/iss1/43