Enhancement of cesium adsorption on Prussian blue by TiO2 photocatalysis: Effect of the TiO2/PB ratio

Abstract

The expanding nuclear industry requires the effective elimination of radioactive wastes generated by nuclear power plant operation and nuclear disasters. Herein, we demonstrate that TiO2 photocatalysis can significantly increase the Cs+ adsorption capacity of Prussian blue (PB), revealing that in PB/TiO2 composites, Cs+ ions are adsorbed exclusively on PB. Cs+ adsorption capacity equaled 0.09 mmol gcomposite−1 (in the dark) and 0.75 mmol gcomposite−1 (under UV light irradiation) for the composite with a PB:TiO2 mass ratio of 5:5, being maximal at a PB:TiO2 mass ratio of 7:3, and the mechanism of photocatalytic Cs+ adsorption enhancement was elucidated and discussed. This enhancement was suppressed by high PB contents (i.e., low TiO2 contents) because of the concomitant suppression of photogenerated electron transfer from TiO2 to PB and was also hindered by the presence of K+ and Na+. However, the Cs+ adsorption capacity of PB/TiO2 at high K+ concentrations under UV light irradiation was still almost twice as high as that observed in the dark. The increase of Cs+ adsorption capacity upon irradiation was ascribed to the concomitant reduction of PB by photogenerated electrons transferred from TiO2. Thus, the present study provides a new direction for the development of next-generation technologies for radioactive Cs removal from contaminated water.