TY - JOUR
T1 - Metachromasy in clay minerals. Sorption of pyronin Y by montmorillonite and laponite
AU - Grauer, Zvi
AU - Grauer, Goldye L.
AU - Avnir, David
AU - Yariv, Shmuel
PY - 1987
Y1 - 1987
N2 - The adsorption of pyronin Y by montmorillonite and laponite has been studied by visible, infrared and X-ray diffraction spectroscopies. The saturation point is much higher in montmorillonite, being 100 and 41 mmol pyronin per 100 g montmorillonite and laponite, respectively. The adsorbed cationic dye is located in the interlayer space. In montmorillonite adsorption leads to metachromasy of the dye and the appearance of a new band at shorter wavelengths than the original band (480 and 545 nm, respectively) even at very small coverages. In laponite, on the other hand, no metachromasy is observed with small amounts of dye. It is observed only when the degree of saturation approaches the saturation point. In montmorillonite the organic cation is oriented with the plain of the rings parallel to the silicate layer. In this parallel orientation π interactions between the oxygen plane of the aluminosilicate and the aromatic dye give rise to metachromasy of the dye. In laponite the plain of the aromatic ring is tilted relative to the silicate layer and π interactions between the oxygen plane and the aromatic dye do not occur. Metachromasy is observed when dimers or aggregates of dye cations are formed in the interlayer space or in the interparticle space of flocs of laponite.
AB - The adsorption of pyronin Y by montmorillonite and laponite has been studied by visible, infrared and X-ray diffraction spectroscopies. The saturation point is much higher in montmorillonite, being 100 and 41 mmol pyronin per 100 g montmorillonite and laponite, respectively. The adsorbed cationic dye is located in the interlayer space. In montmorillonite adsorption leads to metachromasy of the dye and the appearance of a new band at shorter wavelengths than the original band (480 and 545 nm, respectively) even at very small coverages. In laponite, on the other hand, no metachromasy is observed with small amounts of dye. It is observed only when the degree of saturation approaches the saturation point. In montmorillonite the organic cation is oriented with the plain of the rings parallel to the silicate layer. In this parallel orientation π interactions between the oxygen plane of the aluminosilicate and the aromatic dye give rise to metachromasy of the dye. In laponite the plain of the aromatic ring is tilted relative to the silicate layer and π interactions between the oxygen plane and the aromatic dye do not occur. Metachromasy is observed when dimers or aggregates of dye cations are formed in the interlayer space or in the interparticle space of flocs of laponite.
UR - http://www.scopus.com/inward/record.url?scp=37049071765&partnerID=8YFLogxK
U2 - 10.1039/F19878301685
DO - 10.1039/F19878301685
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AN - SCOPUS:37049071765
SN - 0300-9599
VL - 83
SP - 1685
EP - 1701
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 6
ER -