scholarly journals Layer Charge Characteristics of 2:1 Silicate Clay Minerals

1994 ◽  
Author(s):  
S. A. Boyd ◽  
W. J. Farmer ◽  
W. F. Jaynes ◽  
G. Lagaly ◽  
D. A. Laird ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Layer Charge ◽  
Silicate Clay

scholarly journals Effect of slope aspect on transformation of clay minerals in Alpine soils

Clay Minerals ◽  
2007 ◽  
Vol 42 (3) ◽  
pp. 373-398 ◽  
Author(s):  
M. Egli ◽  
A. Mirabella ◽  
G. Sartori ◽  
D. Giaccai ◽  
R. Zanelli ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Soil Profile ◽  
Water Flux ◽  
Layer Charge ◽  
Slope Aspect ◽  
X Ray Diffraction ◽  
The South ◽  
Octahedral Sheet ◽  
The North ◽  
Low Charge

AbstractTwo soil profile sequences on paragneiss debris in the Val di Rabbi (Northern Italy) along an altitude gradient ranging from 1200 to 2400 m a.s.l. were studied to evaluate the effect of aspect on the weathering of clay minerals. All the soils had a coarse structure, a sandy texture and a low pH. Greater weathering intensities of clay-sized phyllosilicates (greater content of smectites) were observed in soils on the north-facing slope. On the south-facing slope, smectite was found only in the surface horizon of the soil profile at the highest altitude. Hot citrate treatment of north-facing soils revealed the presence of low-charged 2:1 clay minerals, the expansion of which was hindered in the untreated state by interlayered polymers. However, the hot citrate treatment encountered some problems with the samples of the south-facing soils: as confirmed by Fourier transform infrared spectroscopy, the hot citrate treatment was unable to remove all interlayer Al polymers. The 2:1 phyllosilicates were not expanded by ethylene glycol solvation in several samples, although thermogravimetric analyses indicated the presence of clay minerals with interlayer H2O. At the same time, the collapse of clay minerals to 1.0 nm following K-saturation was evident. Theoretically, this should indicate that 2:1 phyllosilicates had no evident substitution of trioctahedral cations (Mg2+, Fe2+) by dioctahedral cations (Al3+ and Fe3+). X-ray diffraction analysis of the d060 region and determination of the layer charge of clay minerals by the long-chain (C18) alkylammonium ion, however, did not confirm this. A transformation from trioctahedral to dioctahedral species was observed and low-charge clay minerals (ξ ~0.30) were identified in the surface horizons of the south-facing sites. In the south-facing soils, the podzolization process was less pronounced because of a lower water flux through the soil and probably less complexing organic molecules that would remove the interlayer polymers. Besides the eluviation process, clay minerals underwent a process of ionic substitutions in the octahedral sheet that led to the reduction of the layer charge. This process was more obvious in the north-facing sites.

Influence of KBr conditioning on the infrared hydroxyl-stretching region of saponites

Clay Minerals ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 439-445 ◽  
Author(s):  
M. Pelletier ◽  
L. J. Michot ◽  
O. Barrès ◽  
B. Humbert ◽  
S. Petit ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Clay Minerals ◽  
Diffuse Reflectance ◽  
Layer Charge ◽  
Tetrahedral Sheet ◽  
Stretching Vibration ◽  
Sheet Charge

AbstractIn order to assess the influence of tetrahedral sheet charge on the hydroxyl-stretching vibration in clay minerals, a series of synthetic Na-saponites, with increasing layer charge, was studied by infrared (IR) spectroscopy. When recorded after KBr dilution either in transmission or diffuse reflectance, the IR spectra exhibit a component at ~3710 cm-1, the intensity of which increases linearly with increasing layer charge. When experiments are carried out without any dilution of the samples, this component is not observed, suggesting a Na+/K+ exchange upon mixing of the sample with KBr. The spectra obtained for K-saponite confirm this exchange. This shows that the dilution procedure can lead to serious misinterpretations of IR spectra in the OH-stretching region.

Determination of layer-charge density of expandable 2:1 clay minerals in soils and loess sediments using the alkylammonium method

Clay Minerals ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 291-300 ◽  
Author(s):  
G. Rühlicke ◽  
E. A. Niederbudde
Keyword(s):  
Charge Density ◽  
Clay Minerals ◽  
Adsorption Properties ◽  
Layer Charge ◽  
Basal Spacing ◽  
Adsorption Method ◽  
Resolution Electron ◽  
Fine Clay ◽  
High Resolution Electron Micrographs

AbstractThe alkylammonium adsorption method for the determination of layer-charge density was slightly modified and applied to mixtures of expandable clay minerals (i.e. predominantly 18 Å minerals after glycerol sorption) from two loess samples and two soils (Haplaquept and Aquentic Chromudert) having different K-adsorption properties. The layer-charge density of the so-called 18 Å minerals from these sediments and soil samples varied between −0·23 and −0·85 per formula unit, which suggested the presence of different amounts of vermiculite within the 18 Å minerals. The amounts of these vermiculites were related to K-fixing and K-buffering properties of the different samples. High-resolution electron micrographs of vermiculites saturated with tetradecylammonium exhibited a basal spacing of 25 Å. It was confirmed, that the alkylammonium ions in the interlayers of the vermiculites formed a paraffin-type structure. In the fine clay from the loess samples an interstratification of vermiculite and illitic layers was observed.

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