Metachromasy in clay minerals. Sorption of pyronin Y by montmorillonite and laponite

Abstract

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 montmorilionite, 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 n interactions between the oxygen plane of the aiuminosilicate 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 n 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. '.-.I 500 550 600 650

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

“…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.…”

Influence of the Layer Charge and Clay Particle Size on the Interactions between the Cationic Dye Methylene Blue and Clays in an Aqueous Suspension

“…Since then, interactions between organic molecules and clay particles in aqueous suspension have been extensively studied (2)(3)(4)(5)(6)(7)(8). These studies arose because of the interest in the use of clay minerals as an adsorption medium in applications like wastewater treatment (9,10), image fixation (11,12), and pesticide and herbicide dispersion media (13)(14)(15).…”

Interactions between C.I. Basic Blue 41 and aluminosilicate sorbents

“…For instance, at 125 mmol dye/100 g montmorillonite, the basal spacing reaches 1.80 nm, possibly due to a double sandwichtype dye layer. In an earlier study [27], however, the 0.85-nm interlayer was attributed to a single layer of the dye. Actually, the dye molecules may adopt a different orientation, tending to tilt with respect to the clay basal surface so that as many of them as possible can be arranged in the available space.…”