Metachromasy in Clay Minerals. Part I. Sorption of Methylene‐Blue by Montmorillonite

Yariv, S.; Lurie, Deborah

doi:10.1002/ijch.197100070

Cited by 55 publications

(31 citation statements)

References 19 publications

(31 reference statements)

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“…The presence of dimers even at small loadings was explained by the hypothesis that special sites existed that had a strong preference for dimers. Yariv and Lurie (1971) also observed metachromasy of MB on Wyoming bentonite. Because the observed d(001) value was only 13.5 ~, they ascribed the metachromasy to the interaction of the lone pair of electrons of the surface oxygens with the ~r electrons of the dye.…”

Section: Introductionmentioning

confidence: 80%

“…Thus, the simple theory fully explains the metachromatic effect of dye adsorption on clays in terms of dimerization and trimerization on the surface, exactly as was explained for solution. Ascribing metachromasy to 7r-electron interactions ofMB + with the surface oxygens, as Yariv and Lurie (1971) did, cannot account for the richness of the spectra that were obtained.…”

Section: Dimers and Trimersmentioning

confidence: 92%

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Visible Spectroscopy of Methylene Blue on Hectorite, Laponite B, and Barasym in Aqueous Suspension

Cenens

1988

Clays and clay miner.

309

203

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Abstract--The absorption spectra of methylene blue ion exchanged on hectorite, Laponite B, Barasym, or sepiolite in dilute aqueous suspensions show the presence of the monomer, the protonated monomer, the dimer, and the trimer. Due to conformational differences, the absorption band maximum of the monomer with respect to its maximum in aqueous solution is red shifted when it is adsorbed on the external surface and blue shifted when it is adsorbed on the interlamellar surface. The availability of the interlamellar surface for methylene blue as a function of the type of clay and/or the counterion present thereby can be probed. The results indicate that 0.6-0.7% of the cation-exchange capacity of Barasym consists of acid sites capable of protonating methylene blue. Counterions of low hydration energy were found to induce a small number of similar sites in hectorite and Laponite B; hence, these sites must be situated on the external surface. Dimers formed on external surfaces show one absorption band. Dimers formed on the interlamellar surface of hectofite yield spectra having two absorption bands. The trimer was formed only at the external surface. With increasing loading of the clays, the spectra of methylene blue showed metachromasy. The metachromatic behavior can be fully explained by dye aggregation, which is the result of its concentration on the surface. No 7r-electron interaction with the surface oxygens need be invoked.

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Section: Introductionmentioning

confidence: 80%

Section: Dimers and Trimersmentioning

confidence: 92%

Visible Spectroscopy of Methylene Blue on Hectorite, Laponite B, and Barasym in Aqueous Suspension

Cenens

1988

Clays and clay miner.

309

203

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“…The orientation of MB cations parallel to the surface, frequently reported in the literature (e.g. Hang and Brindley, 1970;Brindley and Thompson, 1970;Kahr and Madsen, 1995;Yariv and Lurie, 1971;Gessner et al, 1994;Cenens and Schoonheydt, 1988;Schoonheydt and Heughebaert, 1992), would not enable such agglomeration. The size of a MB cation is about the same as the average area per negative layer charge of one electron in smectites (Bujd~fk and Komadel, 1997;Bujdftk et al, 1998).…”

Section: Interaction Of Methylene Blue With Claysmentioning

confidence: 94%

Methylene Blue Interactions with Reduced-Charge Smectites

Bujdák

2001

Clays and clay miner.

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Abstract--The objective of this work was to prepare series of reduced-charge materials from different parent Li-saturated dioctahedral smectites, to investigate the effects of temperature, chemical composition and charge location in smectites on the charge reduction and to characterize reduced-charge smectites (RCSs) using methylene blue (MB) adsorption. The layer charge decrease, induced by Li fixation, is correlated with the trends in the spectra of MB-RCS dispersions in the visible region (VIS) spectra. Distribution of the negative surface charge of the clay minerals controls the distance between the adsorbed MB cations and thus affects the formation of MB dimers and higher agglomerates. Because each form of MB (monomer, dimer, higher agglomerate, J-aggregates) absorbs light at a different wavelength, the VIS spectra of MB depend sensitively on the charge density at the clay surface. Both cation exchange capacity (CEC) values and spectra of MB-clay dispersions clearly detect extensive reduction of the layercharge density in reduced-charge montmorillonites (RCMs) upon Li-thermal treatment. The extent of charge reduction depends on the temperature of the thermal treatment, as well as on the octahedral charge of the montmorillonite. Reduction of the layer charge proceeds to a much lesser extent for smectites with mainly tetrahedral charge and high Fe content (Fe-rich beidellite and ferruginous smectite). Both CEC data and MB spectra detect only a slight decrease of the layer charge density, which relates to the low octahedral charge of these minerals. Following heating at higher temperatures (120-160~ slightly higher Li fixation is indicated by CEC values; however, no charge reduction is confirmed by MB spectra. Release of protons accompanying Li + fixation in Fe-rich smectites heated at 180 or 200~ was detected in the spectra of MB-clay dispersions and confirmed by potentiometric titrations.

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“…It has been shown by Yariv and Lurie (1971) that electrons of positively charged aromatic compounds (e.g. methylene blue) may interact with the oxygen sheet of montmorillonite.…”

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confidence: 99%