No. 359: Developing a technology to reduce the volume of contaminanted soil is under way (November 23, 2011)

Toshiba developed a technology to dissolve cesium in contaminated soil with the help of oxalic acid solution used to cleanse metal products. The research team put a soil sample collected from the Fukushima area into oxalic solution and confirmed that the cesium concentration decreased by one digit. If the cesium concentration is reduced below the standard specified by the government, the soil can be returned to nature. Mineral substances adsorb cesium dissolved in the oxalic acid solution, and the solution can be reused for the purification treatment. Nippon Steel Engineering is developing the same kind of technology. The company combines acid and alkali to dissolve cesium, and uses a chemically treated special cloth to adsorb cesium.

A professor of Tokyo Institute of Technology opened up the prospect of separating cesium by a combined usage of iron blue ferric ferrocyanide for pigment and a precipitation agent. If his technology succeeds in returning about one cubic meter of pool water to the environment, the residual is estimated at about 2 kg. Cesium bonds with clay inside the soil. Focusing on this fact, Konoike is trying to commercialize the technology to wash away contaminated soil to separate clay. The research team predicts that the amount needed to be buried in drums will be reduced to 20-30% of the contaminated soil, and substances other than clay can be returned to nature. The amount of contaminated soil and wastes is estimated at 3,100 cubic meters in the disaster-stricken area, and it is urgent to establish the volume reduction technology.