Dip-coated copper hexacyanoferrate/graphitic carbon nitride (CuHCF/g-C3N4) composite films for efficient electrochemical cesium-137 removal

• CuHCF/g-C 3 N 4 films synthesized for efficient 137 Cs removal from wastewater. • Optimal composite ratio (2:1) achieved up to 75% cesium removal efficiency. • Adsorption driven by ESIX and ion exchange with synergistic material interaction. • Cs + adsorption fits pseudo-second-order kinetics and Freundlich isotherm model. The issue of radioactive 137 Cs contamination associated with electric arc furnace dust (EAFD) remains a considerable global concern. In this study, copper hexacyanoferrate/graphitic carbon nitride (CuHCF/g-C 3 N 4 ) composite films were synthesized via a hydrothermal method at different weight ratios of 1:1, 2:1, and 1:2, followed by dip-coating to obtain uniform and stable films with enhances active sites for adsorption. Adsorption mechanisms were identified as electrically switched ion exchange (ESIX) combined with ion exchange processes, facilitated by the synergistic interaction between the two components. Electrochemical adsorption experiments were performed using real wastewater containing an initial concentration of 137 Cs at 1,000 Bq·L -1 , under the optimal conditions of pH 7, 25 °C, applied potential between +1.5 to −0.5 V, scan rate 0.2 mV⋅s -1 and 120 min. The removal efficiencies ( %R ) were observed to be 52%, 41%, 48%, 75%, and 45% for CuHCF, g-C 3 N 4 , CuHCF/g- C 3 N 4 (1:1), CuHCF/g-C 3 N 4 (2:1), and CuHCF/g-C 3 N 4 (1:2) composites, respectively. Further optimization identified the CuHCF/g-C 3 N 4 (2:1) composite as the most effective, achieving %R values of up to 70–75% when tested with real wastewater containing 137 Cs concentrations in the range of 800–20,000 Bq·L -1 , demonstrating strong potential for practical applications. The adsorption behavior of Cs + followed a pseudo-second-order kinetic model and fit well with the Freundlich isotherm, indicating multilayer heterogeneous adsorption. Overall, these results demonstrate that CuHCF/g-C 3 N 4 composite films offer a promising, efficient, and environmentally sustainable solution for the removal of radioactive cesium from contaminated wastewater.