Testing a mechanistic model. III. The effects of pH on fluoride retention by a soil

N. J. BARROW, A. S. ELLIS

Research output: Contribution to journalArticle

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Abstract

The pH of a soil was altered by incubating it with either lime or acid at 60°C for 1 day. Subsamples were then mixed with fluoride solutions in order to measure the effects of pH on fluoride retention. The results were compared with those previously obtained with phosphate on the same soil. At equal concentration of total fluorine in solution, fluoride retention was greatest at about pH 5.5 and decreased at both lower and higher pH. The decrease at low pH appeared to be caused by the formation of complexes between fluoride and aluminium in solution. As a result, only a small proportion of the total fluorine in solution was present as fluoride ions. At equal concentrations of fluoride ions, fluoride retention decreased with increasing pH. It was shown that this decrease could be explained by decreases in the electrostatic potential of the variable charge materials. The decrease in potential was steeper than that required to describe phosphate retention. This is consistent with the plane of adsorption of fluoride ions being closer to the plane of adsorption of H+ and OH ions.

Original languageEnglish
Pages (from-to)287-293
Number of pages7
JournalJournal of Soil Science
Volume37
Issue number2
DOIs
Publication statusPublished - 1 Jan 1986

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mechanistic models
fluorides
Fluorides
fluoride
Soil
soil
Ions
testing
ions
Fluorine
fluorine
ion
Adsorption
Phosphates
adsorption
phosphate
variable charge
phosphates
liming materials
effect

Cite this

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abstract = "The pH of a soil was altered by incubating it with either lime or acid at 60°C for 1 day. Subsamples were then mixed with fluoride solutions in order to measure the effects of pH on fluoride retention. The results were compared with those previously obtained with phosphate on the same soil. At equal concentration of total fluorine in solution, fluoride retention was greatest at about pH 5.5 and decreased at both lower and higher pH. The decrease at low pH appeared to be caused by the formation of complexes between fluoride and aluminium in solution. As a result, only a small proportion of the total fluorine in solution was present as fluoride ions. At equal concentrations of fluoride ions, fluoride retention decreased with increasing pH. It was shown that this decrease could be explained by decreases in the electrostatic potential of the variable charge materials. The decrease in potential was steeper than that required to describe phosphate retention. This is consistent with the plane of adsorption of fluoride ions being closer to the plane of adsorption of H+ and OH− ions.",
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Testing a mechanistic model. III. The effects of pH on fluoride retention by a soil. / BARROW, N. J.; ELLIS, A. S.

In: Journal of Soil Science, Vol. 37, No. 2, 01.01.1986, p. 287-293.

Research output: Contribution to journalArticle

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