Adsorption of cesium from aqueous solution by Japanese cedar charcoal and improvement by immobilization of Prussian blue

In Fukushima, decontamination work has been continuing at various places, and zeolite is mainly used for the removal of radioactive cesium from the contaminated water generated by decontamination operation. Zeolite has a problem in the selectivity of cesium in water and also has a disadvantage that volume reduction is difficult. On the other hand, carbonized products (charcoal) can be reduced in volume through combustion by only leaving ash. This paper introduced that when Prussian blue is added to Japanese cedar (Cryptomeria japonica) charcoal carbonized at 400degC, it shows cesium adsorption performance superior in selectivity. When the carbonization temperature of cedar is raised from 400degC to 1000degC, the BET specific surface area and total pore volume increase. In a model cesium chloride aqueous solution, the cesium adsorption performance of a carbonized product with a lower carbonization temperature of 400degC is higher than that of activated carbon. When cations such as sodium derived from seawater coexisted in the aqueous solution, cesium adsorption performance of cedar charcoal drastically decreased. Adsorption performance recovered significantly when Prussian blue was incorporated to carbonized cedar. The product carbonized at 400degC that carries Prussian blue was the best. In the future, research is required to make this product available at the site of decontamination. (A.O.)