Encapsulation of saline solution by tetrahydrofuran clathrate hydrates and inclusion migration by recrystallization

Kazushige Nagashima, Suguru Orihashi, Yoshitaka Yamamoto, Masayoshi Takahashi

研究成果: Article査読

17 被引用数 (Scopus)

抄録

Encapsulation of saline solution as an impurity in tetrahydrofuran clathrate hydrates grown in a stoichiometric solution with 3 wt% NaCl and the release of a saline solution during melting along with inclusion migration by hydrate recrystallization during annealing are studied using a directional growth apparatus in combination with a Mach-Zender interferometer. Interferometric observation revealed that the salt concentration increased locally in the solution near the growth interface. The time evolution of salt concentration in the solution was in accordance with the numerical results obtained from the diffusion equation for salt, assuming perfect rejection of salt by the hydrate. However, after the interfacial pattern developed into a serrated pattern (periodical array of trough and crest), the salt concentration in the solution ceased to increase, deviating from the theoretical value. This indicates that the saline solution was encapsulated by the growth hydrate. On the other hand, upon melting of the slowly grown hydrate, the salt concentration near the interface was observed to be locally high at the location of the trough during growth, whereas it was dilute at the location of the growth crest. Furthermore, when the hydrate was annealed under an applied temperature gradient, the inclusions (encapsulated saline solution) in the hydrate migrated toward the bulk solution and were finally expelled by hydrate recrystallization. The migration speed of the inclusions increased with a larger temperature gradient. By melting the sample over a sufficiently long anneal time, the melt was determined to be completely desalinated.

本文言語English
ページ(範囲)10147-10153
ページ数7
ジャーナルJournal of Physical Chemistry B
109
20
DOI
出版ステータスPublished - 2005 5月 26
外部発表はい

ASJC Scopus subject areas

  • 物理化学および理論化学
  • 表面、皮膜および薄膜
  • 材料化学

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