Adsorption of the herbicide terbuthylazine by a soil from the Jezreel Valley was investigated by thermo-IR-spectroscopy. The
adsorption took place mainly by the clay mineral montmorillonite. The adsorbed molecule was hydrogen bonded via the aniline
groups to water molecules which were coordinated to the exchangeable metallic cations. When the sample was thermally treated
at 115°C interlayer water was evolved, part of the herbicide decomposed and the other part became directly coordinated to
the exchangeable metallic cations. The decomposition product contained a CO group.
An intense blue organo-clay color pigment was obtained by adding naphthyl-1-ammonium chloride to a Na-montmorillonite aqueous
suspension followed by treatment with sodium nitrite. This treatment resulted in the synthesis of the azo dye 4-(1-naphthylazo)-1-naphthylamine
adsorbed onto the clay. The pigment was subjected to thermo-XRD-analysis and the diffractograms were curve-fitted. Heating
naphthylammonium-montmorillonite at 360°C resulted in the evolution of the amine at temperatures lower than those required
for the formation of charcoal and consequently the clay collapsed. On the other hand, heating the pigment at 360°C resulted
in the conversion of the adsorbed azo dye into charcoal. The clay did not collapse, thus proving that the azo dye was located
inside the interlayer space. Before the thermal treatment a short basal spacing in the pigment compared with that in the ammonium
clay (1.28 and 1.35 nm, respectively) indicated stronger surface π interactions between the clayey O-plane and the azo dye
than between this plane and naphthylammonium cation. The amount of dye after one aging-day of the synthesis-suspension increased
with [NaNO2]/[C10H7NH3] ratio but did not increase with naphthylammonium when the [NaNO2]/[C10H7NH3] ratio remained 1. After 7 and 56 aging days it decreased, indicating that some of the dye decomposed during aging.
Transition metal montmorillonites were saturated with benzidine (BEN) and heated gradually to 200°C, in a vacuum cell supported
by KBr windows. IR spectra were recorded before and after the thermal treatment and at various temperatures during this treatment.
X-ray diffractions were recorded before and after the thermal treatment. Hg clay shows properties similar to those of Mg and
Ca clays. In the interlayer BEN is bound to Hg through a water molecule bridge, either by proton accepting (typeA) or by proton donation (typeB). Some BEN is also protonated (typeD). Initially typeA predominates, but after the thermal treatment, when the film is rehydrated, the amounts of typesB andD increase. With Mn-, Co-, Ni-, Zn- and Cd-montmorillonite a direct coordination of the benzidine by the dehydrated metallic
cation is obtained (typeC), in addition to small amounts of typesA,B andD. During the thermal treatment water is evolved and associationsA andB are completely transformed toC. At elevated temperatures the following associations were identified in trace amounts, ammonium-amine, BEN bound to non-structured
water, hydrophobic adsorbed BEN and BEN bound to the oxygen plane (typesE, F, H andJ, respectively). During the thermal treatment of Co and Cd clays some of the benzidine was oxidized, probably to semiquinone
and quinoidal cation.
Li-, Na-, K-, Rb- and Cs-montmorillonites were saturated with benzidine, these organo-clay complexes heated under vacuum to
200°C and IR spectra recorded at various temperatures. Benzidine is mostly bound to interlayer cations through water molecules,
except in Cs-clay where bonding to hydrophobic water and to water molecules which are hydrogen bonded to the oxygen plane
predominates. During the thermal treatment water is lost and alkali, cations coordinate directly with benzidine. In Cs-, and
to some extent also in Rb- and K-montmorillonite, benzidine is oxidized to semiquinone and quinoidal cation during the thermal
Montmorillonite and Laponite loaded with
different amounts of tributylammonium cations (TBAH+),
up to 40 and 30 mmol, respectively, per 100 g clay, were studied by thermo-XRD-analysis.
TBAH-smectites heated at 300 and 420°C exhibited basal spacings of 1.30
and 1.24 nm, attributed to smectite tactoids with low- and high-temperature-stable
monolayer charcoals, respectively in the interlayers. DTA-EGA and TG of the
TBAH-smectites showed four stages of mass loss labeled A, B, C and D. Stage
A below 250°C, accompanied by an endothermic DTA peak, resulted from the
dehydration of the clay. Mass loss stages B, C and D, at 250–380, 380–605°C
and above 605°C, respectively, accompanied by exothermic DTA peaks, were
due to three oxidation steps of the organic matter. In mass loss stage B (first
oxidation step) mainly organic hydrogen was oxidized to H2O whereas carbon
and nitrogen formed low- and high-temperature-stable charcoals. In stages
C and D (second and third oxidation steps) low- and high-temperature- stable
charcoals were oxidized, respectively. Dehydroxylation of the smectites occurred
together with the second and third oxidation steps. Thermal mass loss at each
step was calculated from the TG curves showing that in montmorillonite the
percentage of high-temperature-stable charcoal from total charcoal decreased
with higher TBAH+ loadings of the clay whereas
in Laponite this percentage increased with higher loadings of the clay.
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.
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.