The Reaction of Fluoride With Soils and Soil Minerals

Abstract

The reaction of sodium fluoride solution with soils and soil minerals at constant pH has been assessed as a possible single-value characteristic in the classification of soils, particularly those containing significant amounts of poorly ordered inorganic material. A suitable method involves reaction of the soil or clay at 25 "C with 0 . 8 5~ sodium fluoride at pH 6.8, the amount of OH-released after 25 min being taken as the single-value characteristic.There was a statistically significant correlation between the amount of OHreleased and the amount of alumina extracted with cold 5 per cent sodium carbonate solution from both freely drained and poorly drained Scottish soils. The multiple correlation coefficients were improved for freely drained soils by including the dithionite-extracted ferric oxide and the silica soluble in 5 per cent sodium carbonate solution. The procedure is not suitable for surface soils, because of interference by organic matter, or for carbonate-containing soils unless carbonate is removed.Introduction SOME studies of the reaction between fluoride solutions and clay minerals have indicated disruption of the mineral structure and the formation of new compounds such as cryolite (Semmens and Meggy, 1966) or soluble fluoroaluminate complexes (Huang and Jackson, 1965), whereas others suggest that only an adsorption reaction occurs Bower

Organic Anion Adsorption on Aluminum Hydroxides: Spin Probe Studies

“…method. The reactive hydroxyl contents of the minerals are 2775, 64, and 48 mmole/100 g, respectively, as measured by the fluoride-reaction method described by Perrott et al (1976). The very high hydroxyl value obtained for noncrystalline alumina reflects the partial dissolution of this material in NaF.…”

Fluoride sorption and mineral stability in an Alberta soil interacting with phosphogypsum leachate

“…Under the present study conditions both aluminum fluoride and fluorophlogopite were quite under-saturated, but the IAP levels for fluorite were closer to equilibrium, ranging from 2.1to-3.6. Elrashidi and Lindsay (1986b) from Elrashidi and Lindsay (1985); for fluorite from Farr and Elmore ( (Lindsay 1979;Sposito 1989 (Perrott et al 1976), mineral impurities (Kittrick 1966) and/or F-catalyzed dissolution (Zutic and Stumm 1984 …”

“…The amount of OH released through F adsorption has been positively correlated with the release of Al from various phyllosilicates and amorphous aluminum hydroxides suggesting degradation of the mineral structure (Huang and Jackson 1965;Perrott et al 1976). Zutic and Stumm (19g4) observed an exceptional increase of dissolution rate of amorphous hydrous alumina in the presence of F (> l0-6 M) in acid solutions (pH 3--6).…”

Structure of Some Allophanes from New Zealand

“…The measurement of OH released from the sample by the reaction with NaF (0.85 M, pH 6.8, 25 min, 25~ followed the procedure of Perrott et al (1976). The measurement of acidity using Hammett indicators has been described by Henmi and Wada (1974).…”