Flexible Ion Adsorption Electrodes Using Natural Zeolite and Rice Husk Charcoal for FEM-EK Treatment

Abstract

The Fukushima Daiichi nuclear power plant accident happened after the devastating earthquake in the Pacific coastal area of Japan on 11 March 2011. After the accident, radioactive materials spread out over a wide area in Japan. Radioactive materials were retained on soil surfaces, causing environmental problems. Among the radioactive materials, cesium (137Cs) has a long half-life of 30.2 years, and it remains near the surface soil; therefore, it is necessary to remove soil contaminated by 137Cs. The contaminated soil layer of inhabited areas in Fukushima was already removed before April 2020. However, the remediation method of Cs with other radioactive materials needs further study, as the large quantity of contaminated soil is not easy to preserve. Electrokinetic (EK) treatment is one of the soil remediation technologies that utilizes EK phenomena at the interface between contaminated soils by transferring ions from the soil. We have developed a new type of EK method in which a cathode is placed on the surface of the soil and an anode is place inside the soil. By applying DC voltage in between the electrodes, the Cs ions can be removed from the contaminated soil. The removed Cs ions are gathered near to the cathode, and if the cathode can adsorb the Cs ions, then only the cathode needs to be preserved, solving the problem of storing a large amount of soil. We have been working to prepare a new type of cathode that can be effective in adsorbing Cs ions and at the same time easier to store and handle. We used natural zeolite and rice husk charcoal (kuntan) to prepare this electrode, which showed good potential for adsorbing Cs ions. The electrode showed flexibility, which is helpful for storing it in the same way as pasture rolls. However, the experiments were conducted in the laboratory with non-radioactive Cs; field experiments and observations are needed for practical applications of this method, as well as the new electrodes.