The Cathodic Reduction Processes of SiO2 Impurity in Magnesium Electrolysis

The cathodic reduction of SiO2 in KCl-CaCl2-NaCl-MgCl2 melt was studied using tungsten wires as working electrodes. The results of cyclic voltammetry square wave voltammetry and chronopotentiometry showed that the cathodic deposition of silicon is a quasi-reversible diffusion-controlled reaction, followed by a four electrons transfer step. The results of current reversal chronopotentiometry and thermodynamic data showed that both the silicon deposition and the side reaction between SiO2 and magnesium result in the loss of magnesium and low current efficiency. A 35.2% current efficiency was obtained with the content of SiO2 0.2% at 700 .