Efficiency of Moso Bamboo Charcoal and Activated Carbon for Adsorbing Radioactive Iodine

Preventing radioactive pollution is a troublesome problem but an urgent concern worldwide because radioactive substances cause serious health-related hazards to human being. The adsorption method has been used for many years to concentrate and remove radioactive pollutants; selecting an adequate adsorbent is the key to the success of an adsorption-based pollution abatement system. In Taiwan, all nuclear power plants use activated carbon as the adsorbent to treat radiation-contaminated air emission. The activated carbon is entirely imported; its price and manufacturing technology are entirely controlled by international companies. Taiwan is rich in bamboo, which is one of the raw materials for high-quality activated carbon. Thus, a less costly activated carbon with the same or even better adsorptive capability as the imported adsorbent can be made from bamboo. The objective of this research is to confirm the adsorptive characteristics and efficiency of the activated carbon made of Taiwan native bamboo for removing (131)I gas from air in the laboratory. The study was conducted using new activated carbon module assembled for treating (131)I-contaminated air. The laboratory results reveal that the (131)I removal efficiency for a single-pass module is as high as 70%, and the overall efficiency is 100% for four single-pass modules operated in series. The bamboo charcoal and bamboo activated carbon have suitable functional groups for adsorbing (131)I and they have greater adsorption capacities than commercial activated carbons. Main mechanism is for trapping of radioiodine on impregnated charcoal, as a result of surface oxidation. When volatile radioiodine is trapped by potassium iodide-impregnated bamboo charcoal, the iodo-compound is first adsorbed on the charcoal surface, and then migrates to iodide ion sites where isotope exchange occurs.