摘要

The effect of alkaline pH on the dissolution rate of bulky aggregated montmorillonite samples at 23 degrees C was investigated for the first time by using an enhanced phase-shift interferometry technique combined with an internal refraction interferometry method developed for this study. This technique was applied to provide a molecular resolution during the optical observation of the dissolution phenomena in real time and in situ while remaining noninvasive. A theoretical normal resolution limit of this technique was 0.78nm in water for opaque material, but was limited to 6.6nm for montmorillonite due to the transparency of the montmorillonite crystal. Normal dissolution velocities as low as 1 x 10(-4) to 1 x 10(-3) nm/s were obtained directly by using the measured temporal change in height of montmorillonite samples set in a reaction cell. The molar dissolution fluxes of montmorillonite obtained in this study gave considerably faster dissolution rates in comparison to those obtained in previous investigations by solution analysis methods. The pH dependence of montmorillonite dissolution rate determined in this study was qualitatively in good agreement with those reported in the previous investigations. The dissolution rates to be used in safety assessments of geological repositories for radioactive wastes should be obtained for bulky samples. This goal has been difficult to achieve using conventional powder experiment technique and solution analysis method, but has been shown to be feasible using the enhanced phase-shift interferometry.

  • 出版日期2013-7-1