A Comparative Study of Tin Electrorefining in Molten LiCl–KCl–CaCl₂: Experimental Two-Electrode Current Control and Theoretical Three-Electrode Potential Control

Molten salt electrorefining is a mature technology for metal recovery, yet conventional current‑controlled, two‑electrode operation provides limited electrochemical selectivity and restricted insight into electrode‑specific behavior. In this work, a simplified model is developed to compare current‑controlled two‑electrode electrorefining data with a potential‑controlled three‑electrode electrorefining simulation using tin in molten LiCl–KCl–CaCl₂ as a surrogate for plutonium processing. The model examines anodic and cathodic limitations under fixed‑potential operation and evaluates implications for selectivity, efficiency, and runtime relative to experimentally demonstrated two‑electrode performance. Results indicate that independent potential control enables operation closer to thermodynamic selectivity limits, with the potential to suppress impurity oxidation and co‑deposition. However, cathodic mass‑transfer limitations are predicted to constrain throughput, leading to longer runtimes compared to current‑controlled operation. These findings highlight a fundamental tradeoff between selectivity and throughput and establish a quantitative framework for assessing the viability of three‑electrode control strategies in molten salt electrorefining systems.