Uptake of fluoride and borate ions from aqueous solution by magnesium-aluminum oxide

Toshiaki Yoshioka, Tomohito Kameda, Motoya Miyahara, Miho Uchida, Tadaaki Mizoguchi, Akitsugu Okuwaki

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Magnesium-aluminum oxide (Mg-Al oxide), which was prepared by the thermal decomposition of a hydrotalcite-like compound, was found to take up fluoride and borate ions in low concentrations in aqueous solution. The degree of fluoride and borate removal increased with the quantity of Mg-Al oxide and temperature. When Mg-Al oxide with a Mg/Al molar ratio of 4.0 was added to 1 mM NaF or H 3BO3 solution at five times the stoichiometric amount, the degree of fluoride and borate removal at 60°C for 1 h reached 92.8 and 95.7%, respectively. The fluoride and borate concentrations decreased from 20 and 10 mg L_1 to 1.4 and 0.5 mg L_1, respectively. Borate was thought to be removed from the solution via combination of the Mg-Al oxide and orthoborate ion, i.e., H2BO3- produced with increasing pH. The fluoride and borate removal reactions could be described as first-order for the fluoride and borate concentrations. The apparent activation energies for the fluoride and borate removal were 33.8 and 51.2 kJ mol -1, respectively, indicating that the reaction proceeded under chemical reaction control. The apparent activation energy for borate removal was higher than that for fluoride removal, indicating that the combination of H2BO3- with Mg-Al oxide was more difficult than that of the fluoride ion. This was attributable to the lower charge density of H2BO3- compared to the fluoride ion.

Original languageEnglish
Pages (from-to)928-933
Number of pages6
JournalFresenius Environmental Bulletin
Volume16
Issue number8
Publication statusPublished - 2007

Keywords

  • Apparent activation energy
  • Borate
  • Fluoride
  • Hydrotalcite-like compound
  • Magnesium-aluminum oxide
  • Uptake

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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