New decontamination tool expected to help Fukushima cleanup

The Research Institute for Sustainable and Environmental Technology of Waseda University (RISET; Shinjuku Ward, Tokyo; Director: Prof. Masahiko Matsukata) and AZMEC Inc. (Headquarters: Mino City, Gifu Prefecture; President: Takenori Shoda) have successfully developed a new material for adsorbing radioactive elements such as cesium and strontium. An inexpensive and highly durable adsorbent, Catenaccio PA is a huge innovation over existing materials. With the Fukushima Daiichi Nuclear Power Station still facing the question of how to tackle the heavily contaminated discharge water at the plant, this highly versatile adsorbent, which is not only able to treat large volumes of contaminated water but which can also be used in other applications such as interim storage facilities for radioactive waste, is expected to have a far-reaching impact.

Traditional adsorbents for radioactive elements have been extremely expensive (costing tens of thousands of yen per kilogram); natural zeolite, by contrast, is low in cost but its adsorption performance is poor, and it also has been known to break down and lose effectiveness in highly alkaline environments such as ash. Catenaccio PA, however, is an inorganic polymer-based adsorbent made from silica and aluminum. As its raw materials are extremely low in cost (around 600 yen per kilogram) it is very easy to manufacture. It also has excellent acid resistance and alkali resistance. In addition, it can be used in interim storage facilities for long periods of time, lasting for at least 30 years before replacement is necessary.

RISET developed this material after its attention was drawn to the cation exchange capacity (CEC) of geopolymer, an inorganic substance which is used as a substitute for cement. Noting the material's CEC level, the researchers decided to make use of this feature. Catenaccio PA is expected to make a significant contribution towards improved safety not only through its use in the treatment of contaminated water from nuclear power plants but also in preventing radiation leaks from interim waste storage facilities currently being planned.

Test method: A liquid solution containing cations 0.1mol/L was prepared for each type. The inorganic polymer-based adsorbent was then added at a liquid-to-solid ratio of 500:1. After three hours, the solution was stirred and an adsorbency test performed. After the solids had been collected through filtration and cleaned with purified water, an EDS analysis was done to investigate the post-adsorbency test composition.