Prussian blue immobilized on covalent organic polymer-grafted granular activated carbon for cesium adsorption from water

Technologies for removing radioactive waste in the form of ¹³⁷Cs, released during nuclear power plant accidents, are essential. Prussian blue (PB) is a pigment with a face-centered cubic structure that can selectively adsorb cesium. However, due to its very small size (5–200 nm), PB can be found in water as a fine powder and it is difficult to separate its disposal to the water system. Thus, in this study, PB was immobilized on granular activated carbon (GAC), normally used for water treatment, to facilitate its recovery after usage. The GAC surface was grafted with a covalent organic polymer (COP) to improve its stability and prevent PB desorption. The COP-grafted GAC immobilized approximately twice as much PB as the ungrafted one; its cesium adsorption capacity was over three times higher and the PB stability was excellent. The effects of pH and water matrix were investigated using samples of both artificial and actual river water. Moreover, a continuous column experiment was conducted to evaluate the applicability of the proposed material in water treatment system in a form of GAC column.