Photo-induced enhancement of radioactive 137Cs removal by adsorption on Prussian blue analogues

Prussian blue analogue (PBA) has been received great attention as a material for radioactive Cs removal because of its high Cs ion adsorption efficiency. In this study, we synthesized PBA with three different transition metal ions (Ni(II), Co(II), and Fe(II) for NiFe-PBA, CoFe-PBA, and FeFe-PBA, respectively) and adjusted their particle sizes and surface areas by controlling the amount of stabilizing agent. They also composited with TiO₂ and then compared the efficiencies of Cs ion adsorption under dark or UV light. The larger the surface areas and the smaller the particle size, the better the Cs ion adsorption, and the NiFe, NiFe-TiO₂ and FeFe-TiO₂ showed additional Cs ion adsorption under UV light irradiation. In particular, NiFe has an adsorption capacity of about 0.8 mmolg^-1 and 1.7 mmolg^-1 under dark and UV light, respectively, which is a result of about twice the increase in the adsorption capacity by UV light irradiation. In addition, the NiFe-TiO₂ nanocomposite shows adsorption capacities of about 0.45 mmolg^-1 and 1.5 mmolg^-1 under dark and UV light, respectively, which is a result of about three times the increase in the adsorption capacity by UV light irradiation. Photo-induced additional adsorption on NiFe showed even with radioactive ¹³⁷Cs adsorption. This enhanced Cs ion adsorption of NiFe happens due to photoinduced charge transfer in NiFe molecular, which leads to additional adsorption of Cs ions. This is very meaningful result because it is first study of photo-induced additional removal of Cs on PBAs.