Dual-Action Strategy: Unlocking Efficient Lanthanide Remove via Cathodic Deposition and High-Temperature Adsorption Synergy

Efficient removal of lanthanide elements during dry processing of spent nuclear fuel is a critical step. Owing to their high neutron absorption cross-section, these lanthanide elements hinder the transmutation of actinide elements. The conventional molten salt electrolysis method for lanthanide extraction suffers from declining efficiency in later stages and high molten salt costs. To address these challenges, this research puts forward a two-pronged approach combining cathode application with elevated-temperature absorption to effectively extract lanthanides and decontaminate radioactive molten salts. Electrochemical analysis via CV, SWV, and OCP measurements was performed on tin electrodes with target ions. Electrolytic extraction using liquid tin as the cathode demonstrated high efficiency: steady 50 mA electrolysis yielded 96.57% average terbium recovery, while constant potential electrolysis at -1.30 V reached 97.32%. Subsequently, based on these electrolysis experiments, molecular sieves were employed to effectively remove terbium ions, achieving a maximum removal rate exceeding 96.47% within the temperature range of 798 to 873 K. For multicomponent lanthanide systems (comprising holmium(III), neodymium(III), praseodymium(III), terbium(III), and thulium(III)), the molecular sieves maintained high removal rates (ranging from 92.41 to 97.64%). Consequently, the synergistic effect of cathode deposition and high-temperature adsorption resulted in a total terbium removal rate of up to 99.91%, while enabling the recovery of LiCl-KCl molten salt and minimizing secondary waste. This strategy effectively mitigates the high cost and low efficiency issues associated with traditional methods, offering an economically viable, efficient, and eco-friendly alternative for separating lanthanide elements in dry spent nuclear fuel processing.