Due to the potential for an uncontrolled release of radionuclides with high levels of radioactivity, it is important to develop strategies for selective adsorption of cesium ions and minimizing the final waste volume. In this work, we demonstrate a novel strategy to fabricate a composite adsorbent immobilizing potassium copper hexacyanoferrate (KCuHCF) in electrospun nanofibers. Transition metal hexacyanoferrates (MHCF) have been extensively studied for removal of cesium, since it has a unique crystal structure for selective insertion of alkali-ions with high adsorption capacity. However, it is necessary to immobilize them to the support for practical application, due to their too small particle size and high water-dispersibility. Thus, we immobilized KCuHCF nanoparticles to the nanofiber membrane through in-situ crystallization to evenly distribute the nano-adsorbents and expose them to the support surface. The supporting nanofiber matrix was fabricated through an electrospinning technique with poly(vinyl alcohol) (PVA) and sodium alginate mixture, and the anionic carboxylate functionality on the alginate effectively coordinated with Cu2+ precursor ions for subsequent synthesis of KCuHCF. The amount of anionic functionality of alginate was controlled by varying the mixing ratio of PVA, and it affected the amount of the KCuHCF content and the uniformity of the composite. The textural characterization was conducted through electron microscopy and spectroscopic analyses, and as a result, well-dispersed KCuHCF particles on the surface of the nanofibrous membrane were confirmed with the optimal PVA/alginate ratio. The composite showed a high cesium adsorption capacity of 114 mg g-1, and it exhibited superior selectivity for cesium with distribution coefficients on the order of 104-105 mL g-1 under seawater and groundwater conditions that containing large amounts of competitive coexisting cations. In addition, it showed rapid cesium uptake kinetics not only in a batch system, but also in the membrane filtration experiment. Under the pressure of 2 bar, efficient decontamination of cesium ions was achieved by removing 180 mg g cesium per 1 m2 with a high flux of about 170 L m-2 h-1. Thus, in-situ immobilization of KCuHCF on the surface of electrospun nanofibers could achieve rapid and selective removal of cesium ions. This immobilization strategy and adsorptive filtration method could be a practical alternative in the radionuclide treatment system.

Potassium copper hexacyanoferrate impregnated on electrospun nanofibers for selective removal of cesium ions

ACS Spring Meeting 2021

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