Treatment of Water Contaminated with Radiocesium Using Novel Complexes between Prussian-Blue and Bivalent Transition Metal Hydroxides

A variety of technologies are applied to the decontamination of radiocesium from water using inorganic adsorbents such as zeolites, Prussian blue (PB) and its analogues. However, these adsorbents are difficult to apply. Although zeolites work as good adsorbents for cesium (Cs) in freshwater, their adsorption ability is extremely low in seawater and fly ash extracts with a high salt concentration. In contrast, PB and its analogues maintain their selective adsorption ability for Cs even in water containing salts, but a high level of cyan remains in the treated water. In this study, we introduce a new technology that utilizes complexes between PB and hydroxides of transition metals (PB-X) for the decontamination of Cs from water and report results of demonstration tests on simulated seawater and fly ash extract. Furthermore, the excellent results of the PB-X method applied to the extracts from fly ash contaminated with radiocesium (more than 8000 Bq/kg) are also shown. It has been proved that radiocesium activities are not only below the detection limit (<10 Bq/kg) and the content of cyan can be controlled under the regulation value of tap water in the water treated with PB-X.