A novel technique ofin situphase-shift interferometry applied for faint dissolution of bulky montmorillonite in alkaline solution

Abstract

The effect of alkaline pH on the dissolution rate of bulky aggregated montmorillonite samples at 23• 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 0.78 nm in water for opaque material, but was limited to 6.6 nm for montmorillonite due to the transparency of the montmorillonite crystal. Normal dissolution velocities as low as 1 × 10 −4 to 1 × 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.

Direct Transmission Electron Microscopy Visualization of the Cement Reaction by Colloidal Aggregation of Fumed Silica

“…The observed rate difference might be related to ambient conditions such as the pH or the amounts of aqueous SiO 2 and Ca 2+ surrounding the silica spheres. Similar observations have been performed by interferometry on dissolving calcite in pure water in the presence and absence of flow . However, calcite does not swell and simply undergoes formation of etch pits under these conditions.…”

“…Similar observations have been performed by interferometry on dissolving calcite in pure water in the presence and absence of flow. 14 However, calcite does not swell and simply undergoes formation of etch pits under these conditions. In situ TEM observations detected both expansion, as a result of diffusion of water into the solid through hydration, and void formation through release of solute into water through dissolution.…”

Surface-specific measurements of olivine dissolution by phase-shift interferometry

“…Phase-shift interferometry provides nanoscale resolved measurements of ultra-slow growth and dissolution of minerals (e.g., van Driessche et al 2011) with a detection limit of <10 -5 nm/s, depending on the stability of the machine, light wavelength and refractive index of the solution or mineral (e.g., Ueta et al 2013). This technique has the benefit of a larger lateral area of study than that of other in situ experimental methods such as atomic force microscopy (AFM) and can be used to obtain long-term measurements of dissolution and growth (see e.g., Green and Lüttge 2006).…”

Interferometric Probing of Physical and Chemical Properties of Solutions: Noncontact Investigation of Liquids

“…Refractive index (86) Concentration (104) Growth or dissolution (74)(75)(76) Growth or dissolution (77) Diffusion coefficient (62) used a Fizeau interferometer with a laser as light source to investigate the film thickness of a liquid wetting the wall of a rectangular microchannel when the channel is emptied. Their results confirmed that a model applied to circular tubes (63) can also be applied to rectangular channels in order to describe the layer thickness during outflow.…”