Electrospun ZnFe-Prussian blue analog nanofiber filters for rapid preconcentration and efficient removal of Cs+ and 137Cs from seawater

Abstract

Radioactive cesium (137Cs), a long-lived (half-life: 30.2 years) and highly mobile fission product, poses environmental and health risks owing to its bioaccumulation. Its trace levels in seawater necessitate a rapid, selective, and field-deployable method for both removal and preconcentration for analysis. Herein, electrospun polyacrylonitrile nanofibers (EnFs) incorporated with ZnFe-Prussian blue analogs (ZnFe-EnFs) were developed as solid-phase adsorbents for the efficient removal of 137Cs from seawater. Two composites, ZnFe(B)-EnF and ZnFe(W)-EnF, were synthesized and characterized. Batch adsorption tests confirmed high Cs+ affinity, indicating that the adsorption process followed the Langmuir model; ZnFe(B)-EnF exhibited a higher maximum adsorption capacity (1.48 mmol g−1), whereas ZnFe(W)-EnF enabled faster adsorption kinetics, stronger binding affinity, and greater tolerance against competing ions and high ionic strength. Dynamic multistage filtration at 60 mL min−1 resulted in complete Cs+ removal from 10 to 15 L of Cs+-spiked deionized water, whereas filtration of natural seawater resulted in high but less reproducible removal efficiencies owing to channeling and clogging. The filtration of contaminated water containing ultratrace-level Cs+ (0.49 μM) resulted in complete Cs+ removal under environmentally realistic conditions. The desorption of Cs+ by circulating NH4NO3 enabled >80 % Cs+ recovery without structural degradation, supporting the stable reuse of composites across multiple adsorption–desorption cycles. ZnFe(W)-EnF simultaneously adsorbed and desorbed both Cs+ and 137Cs from seawater. These findings highlight the dual purpose of ZnFe-EnFs—particularly ZnFe(W)-EnF—as efficient adsorbents for the removal of 137Cs and practical materials for the rapid preconcentration and monitoring of 137Cs in marine environments.