Authors:A. Nasser, M. Gal, Z. Gerstl, U. Mingelgrin, and S. Yariv
The adsorption of the tertiary aromatic amide alachlor by Na-montmorillonite and Al-polyhydroxy-montmorillonite was investigated
by DTA, XRD, SEM and Thermo-FTIR Spectroscopy. This molecule is adsorbed into the interlayer space of the montmorillonite,
replacing interlayer water. In this organo-clay complex the interlayer water forms hydrogen bonds with N or O atoms of the
tertiary amide group. Samples which were aged during six months degraded by hydrolysis to give mainly secondary amide. This
reaction was catalysed by Al-polyhydroxy-montmorillonite more than by Na-montmorillonite.
Polyvinyl chloride (PVC)/organic-montmorillonite composites were prepared by melt intercalation. Their structures and properties
were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC) and mechanical testing. The results
showed that PVC chains could be intercalated into the gallery of organically modified montmorillonite to form exfoliated PVC/organic-montmorillonite
nanocomposites, and the glass transition temperatures of PVC/organic-montmorillonite composites were lower than that of neat
PVC. However, the tensile strength, and both the Izod type and Charpy notched impact strengths of PVC/organic-montmorillonite
nanocomposites were fitted with the linear expressions: t=535.07-6.39Tg, sI=378.76-4.59Tg and sC=276.29-3.59Tg, respectively.
Reduced charge montmorillonites (RCM) were prepared by the thermal treatment of lithiumsaturated montmorillonite. Samples
prepared by mild thermal treatment with lithium contained more water sorbed than the original montmorrilonite. When RCMs were
prepared, part of the lithium cations reacted with hydroxyl groups in the octahedral sheet and released protons, which reacted
with the structure. Acid treatment probably enhanced the surface area. which was reflected in the amount of water sorbed.
Deprotonation of hydroxyl groups was proved by the measurements of the ignition loss. The heating of lithium saturated montmorillonite
at higher temperatures brough about the collapse of the interlayers and a decrease in the amount of water sorbed.
Authors:J. Martucci, A. Vázquez, and R. Ruseckaite
Model gelatin/montmorillonite (Ge/MMt) composites were obtained for a variety of unmodified clay concentrations and in the
absence of additives, with the main goal of evaluating the effect of the morphologies developed on the composites thermal
Morphologies turned form partially exfoliated to exfoliate/intercalated and eventually agglomerated with increasing clay loading,
as was observed by atomic force microscopy. Formulations containing 3–10 mass% montmorillonite resulted in an enhancement
of composites thermal stability due to stabilizing interactions between co-components, such as strong hydrogen-type bonds,
in agreement with the partially exfoliated/intercalated morphologies. Higher clay concentrations showed lower stabilizing
effect in agreement with the agglomerated structures developed and the less effective interactions between co-components.
Authors:V.L. Soares, R. Nascimento, V. Menezes, and L. Batista
Montmorillonite was modified with octadecyltrimethylammonium chloride, under different reaction conditions, as evidenced by
TG and XRD. TG curves presented two degradation peaks (295 and 395C). At low salt concentrations, only the 395C-degradation
appeared, which increased with reaction time to the limit of 9 g of salt/100 g of clay. The second peak presented a limit
at 17/100 m/m of salt/clay ratio. XRD analysis confirmed clay organic modification as the basal distance increased, showing greater reaction
time effect than the salt mass effect, and with only one d-spacing. This suggested that an intercalation complex was formed
but also that octadecyltrimethylammonium was adsorbed on the external surfaces of clay particles.
Authors:Vera Soares, L. Batista, and Rosane San Gil
incorporated into montmorillonite (MMT) though the controlled formation of
Mg(OH)2 followed by calcination. The evidence for Mg2+
in MMT before calcination was concluded from TG curves where two different
temperature ranges for Mg(OH)2 dehydroxylation suggested that the location
of Mg2+ at its internal and external surfaces.
FTIR by diffuse reflectance technique of calcined sample showed a typical
MgO band. XRD indicated a decrease in structural order and no collapse of
clay structure. The organic compounds adsorption to MMT modified with MgO
as suggested by increased degradation temperatures occurred at internal and
external clay surfaces besides in an area formed probably by MgO and MMT layers.
Authors:D. Chen, J. Zhu, P. Yuan, S. Yang, T. Chen, and H. He
A series of anion-cation surfactants modified organoclays are prepared by incorporating both cationic surfactant, hexadecyltrimethylammonium
bromide (HDTMAB), and anionic surfactant, sodiumdodecyl sulfonate (SDS), to montmorillonite. The added amounts of surfactant
varied from 0.2 to 4.0 CEC of the used montmorillonite, similar to those reported in literature. A combination of elemental
analysis, X-ray diffraction and thermogravimetric analysis is used in the characterization of the resulting organoclays. The
experimental results show that anionic surfactants can not be intercalated into the montmorillonite whereas they can be loaded
onto cationic modified montmorillonite, resulting in a further increase of organic carbon content of the resulting organoclays.
This study demonstrates that SDS can be intercalated into montmorillonite interlayer space through the interaction with HDTMAB
rather than by ion exchange. The intercalation of SDS results in an increase of the basal spacing of the resulting organoclays
when comparing with HDTMAB modified montmorillonite and higher decomposition temperature of the intercalated surfactants when
comparing with them in bulk state. These new insights are of high importance in the application of organoclays in the fields
of remediation of polluted water and synthesis of clay based nanocomposites.
Authors:E. Morillo, J. Pérez-Rodríguez, C. Real, and P. Sánchez-Soto
In the present investigation, DTA and TG techniques were used to study the thermal behaviour of montmorillonite treated with
solutions of the pesticide aminotriazole (AMT), in nitrogen flow. These techniques have been complemented by mass spectrometry of the evolved gases (EGA-MS).
AMT is adsorbed in the interlamellar space of montmorillonite as a cation. Results obtained in this study show that this provokes
a shift of the dehydroxylation peak of montmorillonite to lower temperatures than those of the untreated clay. Montmorillonite
protects the adsorbedAMT, delaying its first decomposition step, and catalysesAMT final decomposition at lower temperatures.
The DTA curve of montmorillonite-AMT mechanical mixture differs from the sum of those of the clay mineral and the pesticide heated individually. Montmorillonite
dehydroxylation occurs at lower temperature, indicating a complex formation betweenAMT and the mineral during the heating process. However the DTA of the mixture is different from that of the complex previously
studied, indicating that in the complex obtained by heating the physical mixtureAMT is adsorbed as neutral molecule or as a product of its decomposition.
Authors:Z. Yermiyahu, Anna Kogan, I. Lapides, I. Pelly, and S. Yariv
The blue organo-clay color pigment (OCCP) naphthylazonaphthylammonium-montmorillonite was synthesized from the white naphthylammonium-montmorillonite
by treating with NaNO2, the azo colorant being located in the interlayer space. The following effects on the basal spacing of naphthylazonaphthylammonium-and
naphthylammonium-clay were investigated: (1) the amount of naphthylammonium loading the clay, (2) the amount of NaNO2 used for the staining, (3) aging of the preparation suspension and (4) thermal treatment. Samples were heated at 120, 180,
240, 300 and 360°C and diffracted by X-ray. During aging, some of the dye decomposed.
Samples, after one day aging, were investigated by DTA. During the dehydration stage both organo-clays gradually decomposed,
the naphthylammonium-clay at 120°C and the OCCP at 180°C. That fraction of organic matter, which did not escape, was air-oxidized
at above 200°C and charcoal was obtained. The appearance and size of the DTA exothermic peaks depended on the amount of organic
matter, which did not escape and this depended on the total amount of organic matter in the DTA cell. DTA proved that naphthylammonium
reacted with NaNO2 to form OCCP.
Authors:I. Pastre, I. do Nascimento Oliveira, A. Moitinho, G. de Souza, E. Ionashiro, and F. Fertonani
The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using
thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray
diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct
TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ
was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly
associated to the substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed
on the surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results
confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated.
The experimental results confirm the formation of the composites in agreement with the method used in the preparation.