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

Kazushige Nagashima, Suguru Orihashi, Yoshitaka Yamamoto, Masayoshi Takahashi

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)10147-10153
Number of pages7
JournalJournal of Physical Chemistry B
Volume109
Issue number20
DOIs
Publication statusPublished - 2005 May 26
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Encapsulation of saline solution by tetrahydrofuran clathrate hydrates and inclusion migration by recrystallization'. Together they form a unique fingerprint.

Cite this