Metachromasy in clay minerals. Sorption of acridine orange by montmorillonite

Cohen, Richard L.; Yariv, S.

doi:10.1039/f19848001705

Cited by 68 publications

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“…This result suggests that most MB molecules can exist as monomers on the clay in suspensions of low loading. Similar effects were also reported for planar acridine orange (Cohen and Yariv, 1984) and pyronin Y (Grauer et al, 1987), both of which resemble MB in molecular shape. The adsorption of CV in saponite produced a slight metachromasy similar to that observed for MB.…”

Section: Effect Of Synthetic Saponite On Absorption Spectra Of Cationsupporting

confidence: 63%

Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer

Iwasaki

2000

Clays and clay miner.

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Abstract--The basal spacings of complexes of saponite with five cationic dyes, 1,1 '-diethyl-2,2'-cyanine, crystal violet, methylene blue, l, 1 '-diethyl-2,2'-carbocyanine, and 1,1 '-diethyl-2,2'-dicarbocyanine, varied with degree of saturation of each dye. At low loading of dye to saponite, each cationic dye showed nearly the same absorption spectrum in the UV-visible region as that of its dilute aqueous solution, whereas the spectrum changed distinctly at high loading. With increasing degree of dye loading, the absorption band shifted to longer wavelength for 1,1'-diethyl-2,2'-cyanine (J band) and to shorter wavelength for the others (D, H bands). On the basis of the basal spacing of each respective dye-clay complex, the orientation of the intercalated dye molecules is proposed as follows: the major plane of the cationic dye lies horizontal to the 2:1 layer surface at low loading. With increasing loading, the dye molecules interact with adjacent dye molecules and orient vertically to the 2:1 layer at high loading near the cation-exchange capacity.

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Section: Effect Of Synthetic Saponite On Absorption Spectra Of Cationsupporting

confidence: 63%

Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer

Iwasaki

2000

Clays and clay miner.

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“…As a result of this rc interaction, band ct, which is due to it ~ 7t* transition, is perturbed and is replaced by band [3. This was shown to occur during the adsorption of AO by montmorillonite which is a dioctahedral smectite and gains its charge mainly from octahedral substitutions, but to a small extent also from tetrahedral substitutions (Cohen & Yariv, 1984). Now we show that metachromasy also occurs during the adsorption of AO by saponite.…”

mentioning

confidence: 68%

“…Based on the XRD results which are described later, and on the observations obtained using montmorillonite (Cohen & Yariv, 1984), it is suggested that monomeric cations in the first region are located in the interlayer space, parallel to the silicate layers, forming n interactions with Yariv, 1995). From the location of band ct two different types of clay-dye association can be inferred.…”

Section: Effect Of Na-saponite On the Absorption Spectrum Of Aomentioning

confidence: 99%

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Metachromasy in clay-dye systems: the adsorption of acridine orange by Na-saponite

Garfinkel-Shweky

Yariv

1997

Clay miner.

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The adsorption of the cationic dye acridine orange (AO) by Na-saponite and the colloidal properties of the aqueous suspension were investigated by visible spectroscopy and XRD. The organic cation is adsorbed by the mechanism of cation exchange. When small amounts of the dye are adsorbed, the system contains small tactoids and is peptized. At this stage the dye penetrates into the interlayer space and most of it undergoes metaehromasy due to interactions between the aromatic entity and the oxygen plane of the clay. When greater amounts of AO are adsorbed, the clay platelets flocculate to form book-house floes which, with excess AO, are transformed into card-house floes. At this stage metachromasy results from the aggregation of the dye in the interparticle space of the floes, in addition to the n interactions with the oxygen plane. In excess AO, the clay is gradually peptized. At this stage the dispersed clay platelets form small tactoids with monomeric AO in the interlayer space and at the same time adsorb dimerie and polymeric AO cationic species at the solidliquid interface.The adsorption of metachromic dyes by the trioctahedral smectite-like phase 'Laponite' and the effects of adsorption on the electronic absorption and emission spectra of the clay-dye suspension have been studied by several investigators (Avnir et al., 1986; Cenens & Schoonheydt, 1988;Cenens et al., 1990;Endo et al., 1986Endo et al., , 1988Grauer et al., 1984; Viaene et al., 1987; Tapia Estevez et al., 1994).It was shown in previous publications that the mechanism of the Laponite flocculation in the presence of aromatic organic cations can be studied from the visible spectra of clay suspensions to which metachromic dyes were added (Yariv et al., 1990). The following spectroscopic features were applied for the study of the colloid behaviour of Laponite during the adsorption of acridine orange [AO, I 3,6 -bis (dimethylamine) acridine hydrochloride] (Garfinkel-Shweky & Yariv, 1995).(1) The molar extinction coefficient of the dye decreased with increasing size of absorbing particles. A decrease in absorbance of bands ct or 13 was an indication of flocculation, whereas an increase in absorbance indicated peptization of the clay particles. (2) The maximum of band ~t, which in an aqueous solution appears at 490 nm, showed a red shift when the monomeric cationic dye was located in the interlayer space. Thus a shift of band et to longer wavelengths in the spectrum of the claydye suspension was an indication of the presence of taetoids in peptized systems or book-like assemblages in flocculated systems. (3) The maximum of band ~t was located at ~< 490 nm when the peptized clay contained single platelets. (4) Band 13 appeared when the clay was flocculated, indicating that AO dimers were present in the interparticle space of the floes.Saponite is a trioctahedral smectite with tetrahedral substitutions of A1 for Si. Since this mineral is rare in comparison to montmorillonite, only a little work has been done on the adsorption of organic matter...

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“…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. The same observation and interpretation was put forward for acridine orange (Cohen and Yariv, 1984). Grauer et al (1984), however, did not detect metachromasy with rhodamine 6G because the C6HsCOOC2H 5 substituent of rhodamine 6G hampered an efficient interaction between the oxygens and the 7r electrons (the formulae of the dyes are given in Figure 1).…”

Section: Introductionmentioning

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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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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Metachromasy in clay minerals. Sorption of acridine orange by montmorillonite

Cited by 68 publications

References 0 publications

Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer

Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer

Metachromasy in clay-dye systems: the adsorption of acridine orange by Na-saponite

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

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