Electrochemical measurements of diffusion coefficients and activity coefficients for MnCl2 in molten eutectic LiCl-KCl

• Published in: Journal of nuclear materials 2017-09, Vol.493, p.189-199
• Main Authors: Horvath, D., Rappleye, D., Bagri, P., Simpson, M.F.
• Format: Article
• Language: English
• Subjects: Activity coefficient; Activity coefficients; Diffusion coefficient; Electrical measurement; Electrochemistry; Electrodes; High temperature; Lithium chloride; Manganese; Measurement methods; Molten salt; Molten salts; Nuclear fuel reprocessing; Potassium chloride; Potentiometric analysis; Salts; Voltammetry
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2017.06.015

An electrochemical study of manganese chloride in molten salt mixtures of eutectic LiCl-KCl was carried out using a variety of electrochemical methods in a high temperature cell including cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), and open circuit potentiometry. Single step reduction from Mn2+ to Mn(0) was observed on both W and Mo working electrodes. Using a combination of these methods, measurements were made of activity coefficient and diffusion coefficient for MnCl2 in LiCl-KCl as a function of concentration (3.54 × 10−4 to 3.60 × 10−3 mol fraction of MnCl2) at 773K. From OCP measurements, values for activity coefficient varied from 0.014 to 0.0071. Diffusion coefficients varied with concentration and differed based on measurement method (CV, CA, or CP). Based on cyclic Mn(II) ranged from 1.1 to 2.8 × 10−5 cm2/s depending on concentration.