Electrochemical Enrichment of Radioactive 137Cs using MCDI for Rapid Monitoring in Marine Environments

The growing reliance on nuclear energy to attain carbon neutrality underscores the critical necessity for advanced environmental radioactivity monitoring. Currently, determining ¹³⁷Cs levels in marine environments typically exceeds four days, creating a pressing need for efficient, high-throughput pretreatment systems for rapid analysis. In this study, we developed a membrane-capacitive deionization (MCDI) cell specifically designed for the electrochemical enrichment of Cs, utilizing nickel hexacyanoferrate (NiHCF) as the electrode material due to its high selectivity and redox characteristics. NiHCF electrodes were fabricated via electrospraying and casting methods, followed by comprehensive characterization using SEM, BET/BJH, TGA, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results demonstrated that electrosprayed coatings achieved significantly higher adsorption/desorption efficiency than cast coatings, a superiority attributed to their highly porous structure which facilitates interfacial electrochemical reactions. To address the challenge of ion interference in seawater - where competing cations cause rapid electrode saturation and hinder Cs migration - a pulsed voltage application method was introduced. This approach periodically refreshes the electrode surface, increasing the frequency and duration of Cs migration and subsequently enhancing adsorption efficiency by up to 90%. Furthermore, the performance was validated using a large-scale MCDI cell. These findings suggest that this technology is a promising pretreatment method for the rapid analysis of ¹³⁷Cs in real seawater, contributing significantly to the advancement of environmental radioactivity monitoring.