Abstract This paper summarizes recent results obtained on chemical modifications of smectites. These include replacement exchangeable cations with protons, a process connected smectite autotransformation – attack protons the layers and liberation central atoms from octahedral tetrahedral sheets, causing modification acid sites particles. More severe occur during dissolution in inorganic acids, when are dissolved threedimensional amorphous silica is formed. The negative charge can be...

Abstract Visible to near-infrared (NIR) reflectance spectra and mid-IR transmittance are presented here for a collection of dioctahedral smectites. Analysis the structural OH vibrations is performed by comparing NIR combination overtone bands with fundamental stretching bending absorption features in region. Second derivatives used determine actual band centres, which often shifted slightly spectral continuum or spectra. New have been identified near 4170 4000 cm –1 nontronite tetrahedral...

Interaction of methylene blue (MB) with reduced charge Li−montmorillonites (RCM) in the aqueous suspensions was investigated using visible absorption spectroscopy. Dye cation agglomeration and protonation at clay surface depended very sensitively on layer density. With increasing reduction, content agglomerates MB cations decreased favor monomers protonated form MB. Lower negative density basal induces a greater distance between neighboring sorbed surfaces, which suppresses dye...

Abstract The JP (Jelšový Potok, Slovakia) and SWy-1 (Wyoming, USA) montmorillonites were treated in 6 m HCl at 95°C. rates of dissolution tetrahedral octahedral Al (Al tet oct ) are comparable. Aluminium the sheets was also identified both untreated samples by 29 Si MAS NMR spectroscopy. About 12% total found to be bound quartz. Traces undecomposed montmorillonite a small amount three-dimensional SiO 4 framework reaction product decomposition. Three different types structural units...

Abstract The hydroxyl stretching region of two montmorillonites (SW y-1 , Crook County, Wyoming, USA, and JP, Jelšový Potok, Slovakia) a ferruginous smectite a-1 Grant Washington, USA) have been analysed using decomposition curve-fitting. positions integrated intensities component bands were correlated with the nearest cationic environment OH groups, populations octahedral sheet calculated. differences between coefficients obtained those from chemical analyses 0.07 or less. This method...

Abstract Octahedral Fe(III) in the crystal structures of three different smectites was reduced to Fe(II) by actively growing microorganisms indigenous clay. The were SWa‐1 ferruginous smectite from Grant County, Washington; API 33a, Garfield Nontronite; and 25, Upton montmorillonite. Bacterial growth supported incubating clay suspensions at room temperature a nutrient broth solution consisting peptone beef extract. Some samples first sterilized (by autoclaving), then seeded with bacteria...

The < 2 µm fractions of Cheto (Arizona, USA) and Jelšový Potok (Slovakia) montmorillonites have been treated with 1 mol dm–3 H2SO4 for periods up to 6 h at 95 °C. materials obtained were investigated by X-ray fluorescence (XRF), diffraction (XRD), infrared (IR) spectroscopy, 29Si 27Al magic-angle spinning (MAS) NMR spectroscopy. Both clays partially decomposed under the conditions utilized, but montmorillonite, which contained a higher proportion octahedral magnesium, was more susceptible...

Abstract Mechanically-prepared binary mixtures of two dioctahedral smectites (of different chemical compositions) with kaolinites (with amounts structural defects) were studied by infrared (IR) spectroscopy to verify the ability IR detect small individual components in mixtures. The same samples analysed X-ray diffraction (XRD) transmission and reflection geometries compare sensitivities these techniques. Infrared is suitable for detecting kaolinite smectite-rich but not sensitive smectite...

Abstract A series of reduced-charge montmorillonites (RCM), prepared from the same parent Li-montmorillonite (Jelšový Potok, Slovakia) by heating at various temperatures (105–210°C) for 24 h, was treated with 6 m HCl 95°C periods up to 30 h. Reaction solutions obtained were analysed Al, Fe, Mg and Li solid reaction products investigated FTIR spectroscopy. Both analyses provided evidence that extent dissolution decreased increased amounts fixed within montmorillonite structure, i.e....

The reduction of structural Fe in smectite may be mediated either abiotically by reaction with chemical reducing agents or biotically various bacterial species. effects abiotic on clay surface chemistry are much better known than the biotic reduction, and differences between them still need investigation. purpose present study was to compare dithionite (abiotic) bacteria (biotic) nontronite structure as observed variable-temperature Mössbauer spectroscopy. Biotic accomplished incubating...

Five layered silicates in which the octahedral sheet contained differing amounts of Al, Mg, Fe, and Li were acid leached using concentrations treatment temperatures selected to produce materials was depopulated a controlled, stepwise (yet comparable) manner. SAz-1 JP are dioctahedral smectites with compositions rich Mg respectively. SWa-1 is ferruginous smectite ST an iron-rich beidellite. The fifth mineral trioctahedral hectorite contains almost exclusively Mg. Brønsted acidity catalytic...