Electrochemical Investigation of Moisture Byproducts in Molten Calcium Chloride

Abstract

Residual water in molten CaCl2 reacts to form different byproducts, such as HCl, which can impact the corrosivity of the salt and efficiency of electrochemical operations, such as electrolytic oxide reduction and electrorefining. The ability to detect and quantify these byproducts electrochemically can provide feedback on the efficacy of vacuum drying and other purification methods, as well as the impact of these byproducts on process operations. An electrochemical signal’s association with the production of H2 is verified and characterized using cyclic voltammetry (CV) and residual gas analysis. CV estimated a 2-electron exchange process associated with H2 production. CV detected trace quantities of an oxidized species containing hydrogen in the salt on the order of 10 ppm. Different salt handling methods were compared for their impact on the hydrogen electrochemical signal. It was found that 30 min of exposure of CaCl2 in a beaker to low-humidity air (<20%) had minimal impact on the H2 production signal.