PROBLEM TO BE SOLVED: To provide a method to separate and remove radioactive cesium from discharge water which contains radioactive cesium to eliminate the possibility the discharge water contains cyanide to release the water to the environment.SOLUTION: Discharge water containing radioactive cesium is allowed to come into contact with ferric ferrocyanide so that the ferric ferrocyanide absorbs the radioactive cesium. Alkali is added to aqueous dispersion of the ferric ferrocyanide which contains absorbed radioactive cesium to reach pH10 or more to resolve the ferric ferrocyanide to release the absorbed radioactive cesium. The aqueous solution containing radioactive cesium ion is brought into contact with zeolite so that the zeolite absorbs the radioactive cesium. After separating the zeolite from the liquid containing colloid of Fe(OH)3 along with ferrocyanic ion and sulfuric ion, the zeolite is subjected to storing processing.
