Dissolution Rates of Amorphous Silica in Highly Alkaline Solution

Yuichi Niibori, Masahisa Kunita, Osamu Tochiyama, Tadashi Chida

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Cement is an essential materials to construct the subsurface radioactive waste disposal system. However, cementitious materials alter the groundwater pH to highly alkaline condition about 13. To comprehend the effect of such a hyperalkaline condition on the repository surroundings, this study focused on the dissolution rates of amorphous silica at [NaOH] = 10-1 mol·dm-3. The used samples were three kinds of pure commercial silica and a natural silica scale which was obtained from inside wall of the hot-water pipe of a geothermal power plant. The observed dissolution rates were interpreted with using the model, which assumed that the particle sizes decrease with the progress of dissolution. Moreover, due to the particle size distribution anticipated in the natural silica scale, this analysis assumed it contained particles with various initial diameters. In the results, (1) all pure silica samples and at least 60 wt% of the silica scale showed good agreement of the activation energy of the dissolution in the range of 77 through 88 kJ·mol-1 in the highly alkaline solution, (2) these rate constants were of the order of 10-8-10-7 mol·m-2·s-1 at around 310K and were definitely larger than those already reported for quartz, (3) the specific surface area based on BET method was revealed to be an important factor to give the main difference in the dissolution rates between the synthetic silica and the natural silica.

Original languageEnglish
Pages (from-to)349-357
Number of pages9
Journaljournal of nuclear science and technology
Volume37
Issue number4
DOIs
Publication statusPublished - 2000 Jan 1

Keywords

  • Activation energy
  • Alternation
  • Amorphous silica
  • Dissolution rate
  • Highly alkaline solution
  • Kinetics
  • Radioactive waste disposal
  • Radioactive wastes
  • Repository system
  • Silica gel
  • Silica scale
  • Solidification
  • Temperature dependence
  • Waste processing
  • pH value

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering

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