Selective electrosorption of Cs(I) from high-salinity radioactive wastewater using CNT-interspersed potassium zinc ferrocyanide electrodes

Abstract

The management of ¹³⁷Cs-containing radioactive wastewater from the Fukushima nuclear accident (FNA) has garnered significant attention due to the challenge of its safe disposal. The presence of co-existing Na⁺ ions severely impedes Cs⁺ removal, exacerbating the costs associated with radioactive wastewater treatment. Recently, capacitive deionization (CDI) technology has demonstrated significant potential in this field. However, its application is limited by the lack of suitable electrode materials that exhibit high Cs⁺ selectivity. In this study, we developed a composite of carbon nanotubes (CNT) interspersed potassium zinc ferrocyanide (KZnFC-CNT), which was pre-activated via an electrochemical method, to serve as a CDI cathode for the selective electrosorption of Cs⁺ ions from saline radioactive wastewater. The KZnFC-CNT electrodes exhibited a maximum electrosorption capacity of 392.75 ​mg ​g⁻¹, with the highest electrosorption rate of 11.21 ​mg ​g⁻¹ ​min⁻¹. Furthermore, these electrodes exhibited remarkable selectivity, achieving a selectivity factor of 138.2 for Cs⁺ over Na⁺ in a Na⁺: Cs⁺ molar ratio of 100 : 1. X-ray diffraction, electrochemical analysis, and theoretical simulations revealed that the selective electrosorption of Cs⁺ is primarily governed by the ion exchange process between Cs⁺ and Na⁺ ions, as well as lattice phase transformations in KZnFC. This study presents an effective approach for the treatment of cesium-containing radioactive wastewater with high salinity.