Stability of fluoride complex with silica and its distribution in natural water systems

Chemical Geology
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Abstract

Fluoride reacts with silicic acid to form SiF2−6. A fluoride electrode was used to obtain an equilibrium constant of 1030.18 for the reaction:Si(OH)06+ 6F−+4H+=SiF2−6+ 4H2O at 25°C

Although there may be some experimental evidence for existence of traces of species containing less than six F ions per silicon (n = 6), the species SiF2−6 predominates for n values from about 0.1 to 6.

Silicic-acid complexing with fluoride is important only in solutions which have rather low pH and low concentrations of other cations which compete with silicon for fluoride. Computations for cold volcanic condensates from Hawaii indicate that for some samples much of the silicon is complexed by fluoride as SiF2−6. However, in most cooled acidic natural water samples Al and Fe are more important than Si in complexing fluoride.

Publication type Article
Publication Subtype Journal Article
Title Stability of fluoride complex with silica and its distribution in natural water systems
Series title Chemical Geology
DOI 10.1016/0009-2541(78)90047-5
Volume 21
Issue 3-4
Year Published 1978
Language English
Publisher Elsevier
Description 18 p.
First page 239
Last page 256
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