Migration Behavior of U(VI) in Tuff

Abstract

AbstractAdsorption coefficient and penetration behavior of U(VI) in Itado tuff were measured. The migration behavior of U(VI) in the tuff was discussed.Adsorption coefficient of U(VI) was measured by a batch method using a wafer specimen and a powder specimen in pH region from 2 to 7. Adsorption coefficient was 17000 m1/g at the pH value of 5.5.Penetration behavior of U2− (VI) in Itado tuff was studied as a function of pH, concentration of CO32− and temperature by contacting the rock specimen with U(VI) solution. The concentration profile and fractional amount of U(VI) penetrating into the rock specimen Mt/M were measured. The penetration behavior of U(VI) was seen to be diffusion accompanied by adsorption/desorption process. In the pH region from 3 to 4, it is likely that the penetration process of U(VI) is not sufficiently reversible but is competitive process consisting of diffusion and adsorption. In the pH region above 6, penetration depth was very thin because of both large adsorption coefficient and large adsorption rate constant.The sectioning method was found to have an advantage to see the penetration behavior directly. But in the pH region from 6 to 7, the method has a shortage that diffusion coefficient, and adsorption and desorption rate constant could not be determined, because of small penetration depth of U(VI). From this point of view, the measurement of the fractional amount of penetration as a function of time should be carried out as well as that of concentration profile.