Sequential removal of radioactive Cs by electrochemical adsorption and desorption reaction using core-shell structured carbon nanofiber–Prussian blue composites

¹³⁷Cs is harmful to human health and the environment; hence, research on new techniques and development of materials for removing from contaminated water have attracted attention. Herein, we demonstrate that core-shell structured Prussian blue–carbon nanofiber (PB–CNF) composites, synthesized by electrodeposition, can be used to effectively remove radioactive ¹³⁷Cs via electrochemical adsorption/desorption. PB nanoparticles with thicknesses of tens of nanometers were electrochemically formed on the CNF core with a diameter of approximately 100 nm; the exact weight of PB on CNF was 2.75 mg/cm². The PB–CNF electrodes more efficiently adsorbed and desorbed the Cs ions than the existing PB–FTO electrode and PB–commercial carbon cloth. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed that the Cs ions removed from the solution were adsorbed on PB rather than on CNF. X-ray photoelectron spectroscopy analysis confirmed that the oxidation state of iron in PB changes depending on the Cs ion adsorption and desorption reaction. Cycling experiments of electrochemical adsorption and desorption using PB–CNF showed that radioactive ¹³⁷Cs and non-radioactive Cs ions can be continuously removed from radioactive wastewater and accumulated in a specific solution. These results imply that the PB–CNF composite can efficiently remove radioactive Cs and significantly reduce secondary radioactive waste. Moreover, the composite is reusable and can aid the establishment of a low-cost alternative Cs removal process.