Removal of radioactive iodine and cesium species from rainwater by a pot-type water purifier, and chemical and physical analysis of radioactive components in rainwater

摘要

A pot-type water purifier captured 98% of the nonradioactive iodine and iodide when an ion-exchange resin and activated carbon were used. Approximately 93.8% of ~(131)I, 74 to 84.5% of ~(134)Cs, and 75 to 81.1% of ~(137)Cs in rainwater were captured after six repeated purifications using the purifier. The remaining 6.2% of ~(131)I was not removed by isotope exchange with nonradioactive I~(-) or by reduction to I~(-) using Na_(2)S_(2)O_(4). Approximately 19% of ~(131)I, 40% of ~(134)Cs, and 33% of ~(137)Cs were adsorbed on the silica gel. Analysis of the removal rates of 73% for the mixed ion exchange resin, 59% for the silver ions, and 18% for the silver nanoparticle-bound clay indicated that the content of ~(131)I adsorbed particles components was 23%. The concentration ratio of radioactive components in rainwater decreased from 5.9 to 1.4 upon ultrafiltration with a YM-1 membrane filter, indicating that a soft aggregation of the aerosol occurred. The IP and γ-ray spectrum analysis of the filter produced a cottonlike image of ~(131)I. Analysis of the TEM image and its electron diffraction pattern indicated the aggregation of a small fraction of the SiO_(2) aerosol. The coagulation of radioactive components in rainwater using I-adsorbed SiO_(2) nanoparticles may be due to the exchange of the ~(131)I isotope with I in I-SiO_(2) and the adsorption of ~(134)Cs~(+) and ~(137)Cs~(+) on the surface of SiO_(2) or the precipitation of the ~(131)I-adsorbed aerosol and ~(134)Cs- and ~(137)Cs-adsorbed aerosols.