Use of square wave voltammeter for online monitoring of O2− concentration in molten fluorides at 600 °C

•The practical O2− concentration is measured in the FLINAK melts.•The linear equation between peak current density and O2− concentration is established by using square wave voltammeter (SWV).•The solubility product of ZrO2 was measured as (5.532–6.327) × 10−7 mol3/kg3 through SWV.

The total concentrations of oxide and oxygenated anions in FLINAK melts were detected by using LECO oxygen detector and ion chromatography, respectively. The practical O2− concentration was measured by subtracting the concentration of oxide in oxygenated anions from the total concentration of oxide. Square wave voltammeter (SWV) was then applied to determine the electrochemical behavior of O2− in FLINAK melts at 600 °C, which revealed that the process of oxidation from O2− to oxygen was controlled by diffusion. The quantitative relation between O2− concentration and peak current density was also established. The solubility product of ZrO2 was measured as (5.532–6.327) × 10−7 mol3/kg3 through SWV.