The mechanochemical solid-state adsorption of the cationic dye crystal violet (CV) by montmorillonite was investigated by XRD and simultaneous DTA-TG. Solid CV was ground with the clay for 5 min and four different varieties of CV mechanochemically treated clay were investigated. X-ray and DTA data were compared with those of CV-montmorillonite obtained from an aqueous suspension. X-ray and DTA studies of a ground mixture and a ground mixture heated at 110°C suggest that the mechanochemical adsorption of organic cations takes place on the external surfaces of the clay. The study of a ground mixture washed with water, and washed with water and acetone reveal that water is essential for the penetration of CV into the interlayer space.
Authors:A. Landau, A. Zaban, I. Lapides, and S. Yariv
The mechanochemical solid-state adsorption of the cationic dye rhodamine-6G (R6G) by montmorillonite was investigated by XRD
and simultaneous DTA-TG. Five different mixtures of R6G and montmorillonite were investigated. They contained 10, 20, 35,
50 and 100 mmol R6G per 100 g clay. The solid R6G was ground with the clay for five minutes. Mixtures were ground both in
the absence of water (dry grinding) and with the adding of drops of water periodically, (wet grinding). There were no differences
between samples obtained by wet or dry grinding. X-ray and DTA data were compared with those of R6G-montmorillonite obtained
from aqueous suspensions. The mechanochemical products were different from those obtained from aqueous suspensions. The X-ray
and DTA studies suggest that the mechanochemical adsorption of organic cations takes place on the external surfaces of the
clay whereas in suspensions the adsorption takes place into the interlayer space. In the latter case the final stages of oxidation
occur in temperatures higher than those of the neat dye whereas in the former they occur at lower temperatures.
Montmorillonite (M) saturated with H+,Li+,Na+,K+,Rb+,Cs+,NH4+,Mg2+,Ca2+,Sr2+,Ba2+,Mn2+,Co2+,Cu2+,Al3+ and Fe3+ were dry-ground with urea (U) in mass ratios U/M between 0.1 and 2.0 in an agate mortar and diffracted by X-ray. Extensive swellings occurred with H-, Li-, Na-, di-and trivalent
cation-clays, suggesting the formation of urea-montmorillonite intercalation complexes. Mechanochemically treated samples
were heated at different temperatures up to 375°C. The rise in temperature was accompanied by a decrease in the basal spacing.
There was a correlation between the results of the thermo-XRD-analysis and the fine structures of the urea-montmorillonite
complexes described in the literature. Five stages in the basal spacing vs. temperature curves were identified. In the first stage (at 150°C) the decrease was due to dehydration. In the second stage
(175°C) this dehydration was accompanied by some thermal intercalation of excess urea. The other stages (at 225, 325 and 375°C)
were associated with the degradation of urea and the condensation of the degraded species to polymeric products. At 375°C
Li-, Na-, K-NH4-, Mh-, Co- and Cu-montmorillonite collapsed, indicating that urea was evolved. The other urea-clay complexes did not collapse
due to intercalated polymers formed by the degradation products of urea.
The alumina-dye composites were prepared by treating the basic alumina with the water solutions of Reactive Red 120 (RR 120)
and Reactive Blue 15 (RB 15) dyes. The bands of low intensities in the 1400–1600 cm−1 region and at 783 cm−1 in the IR spectra of these composites point out that the dye species is bound weakly to the surface. In the case of mechanochemical
adsorption of dye molecules, the asymmetric and symmetric S(=O)2 and the S-O-C stretching bands together with the vibrations of aromatic ring revealed that dye types under dry conditions
interacted effectively with alumina surface. After the heating of the alumina dye complexes in the temperature range 150–350°C,
the intensities of the IR and XRD peaks for adsorbed types decreased. The endothermic peaks over 200°C and the bigger total
mass losses for the alumina-dye composites can be ascribed to the decomposition of dye species retained by the alumina surface.
The mass losses on TG curves of the alumina-dye complexes up to ∼800°C exhibit the removal of black residues occurred by decomposition
of first adsorbed products. The thermal analysis data also point out that the water molecules bonded strongly to the alumina
surface and dye types compete to accommodate at the surface active sites.
Authors:Shmuel Yariv, Mikhail Borisover, and Isaak Lapides
peak appeared in the CO 2 evolution curve above 600 °C indicating the presence of small amounts of HTSC in the interlayer space. DTA–TG curves of R6G-MONT obtained by mechanochemicaladsorption in a dry system did not show any exothermic reaction above
. The effect of mechanochemical treatments on clay minerals and the mechanochemicaladsorption of organic materials onto clay minerals . J Mater Synth Process. 2000 ; 8 : 223 – 33 http://dx.doi.org/10.1023/A:1011320328102