Interlayer Space Of Montmorillonite Research Articles

Dynamics of Water Confined in Clay Minerals

Ultrafast infrared spectroscopy of the O–D stretching mode of dilute HOD in H2O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li+ and Ca2+) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 ps in the case of Li+ cations with two water pseudolayers (2.2–2.3 ps in the case of Ca2+ cations) and to 4.7 ps in the case of Li+ cations with one water pseudolayer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudolayers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observatio...

Thermal, spectral, and diffraction properties of Co-exchanged montmorillonite with 2-, 3-, and 4-hydroxyphenol

The influence of the 2-, 3-, and 4-OH phenols on the type of interaction with Co-exchanged montmorillonite and thermal properties of these materials were studied. The results of XRD, IR, and thermal (TG, DTG) analysis show that organic species are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20–700 °C of studied samples with 2- and 3-hydroxyphenol proceeds in three steps (the release of adsorbed H2O molecules, combustion/desorption of protonated hydroxy phenols and dehydroxylation), while the sample with 4-hydroxyphenol decompose in four steps (the new peak at ~222 °C corresponds to directly coordinated organic species). The effect of different position of the hydroxyl groups on the phenol ring on the thermal decomposition is evident.

Montmorillonite intercalated by conducting polyanilines

Structure and conductivity of nanocomposite conducting polymer/montmorillonite have been investigated for samples prepared by the polymerization of aniline hydrochloride with ammonium peroxodisulfate in aqueous suspension of montmorillonite. Samples were characterized by combination of X-ray powder diffraction (XRPD), IR spectroscopy and electrical conductivity measurements. Structure analysis based on combination of molecular modeling and experiment (XRPD and IR spectroscopy) revealed the structure of nanocomposite, including the interlayer structure of montmorillonite, and helped to understand the processes during nanocomposite preparation. Partial intercalation of polyaniline oligomers into the interlayer space of montmorillonite led to the large inhomogeneity of interlayer structure, which results in dramatic decrease of the electrical conductivity of nanocomposite in comparison with pure polyaniline.

Advances in Research on Adsorption Characteristics of Alkylammonium in Montmorillonite Inter-Layer Space

Adsorption Characteristics and controlling methods of long-chain alkyl ammonium cations in montmorillonite interlayer space are theoretic evidence of the montmorillonite/alkylammonium complexes in the process of preparation. This paper summarizes the advances in research on adsorption characteristics of alkyl ammonium in montmorillonite inter-layer space.

Advances in Research on Adsorption Characteristics of Alkylammonium in Montmorillonite Inter-Layer Space

Adsorption Characteristics and controlling methods of long-chain alkyl ammonium cations in montmorillonite interlayer space are theoretic evidence of the montmorillonite/alkylammonium complexes in the process of preparation. This paper summarizes the advances in research on adsorption characteristics of alkyl ammonium in montmorillonite inter-layer space.

Intercalation assembly, characterization and luminescent properties of novel composite material, Tb(III) complex-montmorillonite

Tetrapodal ligand L (2, 2, 2', 2'-tetra[N-benzyl-N-phenyl (acetamide)-2-oxymethyl] n-butyl ether) and complex [TbL] (ClO4)3 are synthesized. The complex ion with tetrapodal ligand L, [TbL]3+ is intercalated into the interlayer space of montmorillonite (MMT) by ion exchanging. The obtained luminescent supramolecular composite material, [TbL]3+-MMT is characterized by elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroseopy. At the same time, the luminescent properties of the material are also studied. The results show that the intercalated material with regular layered structure and the interlayer spacing (d001) approximate to the diameter of the complex ion arranged in the interlayer space of the MMT in the formation of a monolayer emit characteristic green emission of Tb3+ strongly under the excitation of ultraviolet light. It is also found that the relative luminescence intensity, the luminescence monochromatic index and the light stability of the intercalated material are distinctly improved after the [TbL]3+ has been intercalated into the MMT. And the excitation wavelength of the complex is modulated till the red shift occurs in the composite material.

Ca (2,2′-Bipyridine)<sub>3</sub>]<sup>2+</sup>-Intercalated Montmorillonite: An Application as Potentiometric Sensor

This article involves the use of [Ca (2,2′-bipyridine)3]2+-intercalated montmorillonite as a potentiometric sensor to measure anions in aqueous solution. The [Ca (2,2′-bipyridine)3]2+-intercalated montmorillonite was prepared by modification of an in situ solid-solid reaction, between natural Ca (II)-montmorillonite and 2,2′-bipyridine at a molar ratio 1:3. The formation of [Ca (2,2′-bipyridine)3]2+- in the interlayer space of montmorillonite was confirmed by powder X-ray diffraction (XRD) and the existence of 2,2′-bipyridine was confirmed by the C:N ratio of the product compared with that of the 2,2′-bipyridine molecule. The potentiometric sensor was constructed by mixing [Ca (2,2′-bipyridine)3]2+-intercalated montmorillonite with artificial graphite, polytetrafluoroethylene (PTFE) and carboxymethylcellulose (CMC) in an appropriate ratio. It was found that the sensor had higher sensitivity to S2- rather than other anions, graphs of log [S2-] vs voltage (mv) gave a slope 30.0 which was closed to theoretical value, 29.5. Activity of the [Ca (2,2′-bipyridine)3]2+ sensor was verified by using sensor made from Ca (II)-montmorillonite as a reference. Reproducibility and precision of the electrode were also determined.

Thermogravimetric analysis of different molar mass ammonium cations intercalated different cationic forms of montmorillonite

Different cationic forms of montmorillonite, mainly K-, Na-, Ca- and Mg-montmorillonites were intercalated in this study via ion exchange process with mono-, di-, and triethanolammonium cations. The developed samples were characterized by TG, XRD, and CHNS techniques. Thermogravimetric study of ammonium-montmorillonites shows three thermal transition steps, which are attributable to the volatilization of the physically adsorbed water and dehydration, followed by the decomposition of the intercalated ammonium cations and dehydroxylation of the structural water of the modified clay, respectively, while untreated and cationic forms of montmorillonite showed only two decomposition steps. The type of ammonium cation has affected both desorption temperature (Position) and the amount of the adsorbed water (intensity). XRD results show a stepwise change in the crystallographic spacings of montmorillonite with the molar mass of ammonium cation, reflecting a change in the structure of the clay. CHNS data confirm the intercalation of ammonium cations into the interlayer space of montmorillonite and corroborate the effect of the molar mass of ammonium cation on the amount adsorbed by the clay.

Thermal properties of montmorillonite–polyaniline nanocomposites

Various polymer materials incorporated into the interlayer spaces of montmorillonite (MMT) has received a great dealofattention in the research field of clay-polymer nanocomposites. This is due to the dramatic enhancements in physical properties, such as thermal and mechanical properties, of such nanocomposites compared to their parent materials. Inthis paper, the thermal behavior of montmorillonite-polyaniline nanocomposites is analyzed in a wide range of temperatures (30–1000°C) by the thermogravimetric analysis (TGA) and by differential scanning calorimetry (DSC). Inair, the thermal degradation of polyaniline (PANI) (chemically polymerized) starts at 255°C, whereas that in Na+-intercalated MMT-polyaniline and in Ce(IV)-intercalated MMT-polyaniline nanocomposites start at 290 and 330°C, respectively. This improvement in the thermal stability of PANI in the nanocomposites is attributed to the presence of polyaniline in the nano-scaled MMT interlayer spaces in a high aspect ratio where the MMT layers are acting as barriers protecting PANI from degradation. XRD, SEM, and FT-IR data support this conclusion. Better stability of polyaniline in Ce(IV)-intercalated MMT may be due the formation of ordered well-aligned polymer only within the inter-galleries of MMT with a high aspect ratio. In the case of Na+-MMT-polyaniline nanocomposites the polymer is present within the interlayer spaces as well as in the exfoliate form and hence lower thermal stability of polyaniline when compared to that in Ce(IV)-intercalated nanocomposites.

Removal of methyl orange from aqueous solutions using a bentonite modified with a new gemini surfactant

Glycol bis-N-cetylnicotinate dibromide (designated as GN16-1-16), a new cationic gemini surfactant, was prepared and used to modify bentonite. Bentonite modified with commercial cetyltrimethylammonium bromide (CTMAB) was also prepared for comparison purposes. FTIR and XRD revealed that both surfactants successfully intercalated into the bentonite layers. The basal spacing was 2.65 nm for GN-Bt (the bentonite modified by GN16-1-16) and 2.14 nm for C-Bt (the bentonite modified by CTMAB), indicating that GN16-1-16 was more efficient than CTMAB in expanding the interlayer space of montmorillonite. The optimum reaction time and temperature in the modification were 1 h and 30 °C for GN16-1-16 and 3 h and 70 °C for CTMAB. The GN16-1-16 reacted with bentonite faster than CTMAB. The decoloration rate and the COD removal of methyl orange (MO) solution were 99.02% and 90.62% for GN-Bt and 80.12% and 75.49% for C-BT. Therefore, GN-Bt was more effective than C-Bt to remove MO from aqueous solution. However, the efficiency of GN-Bt decreased rapidly at pH > 6, which might be due to the hydrolysis of the ester groups in GN16-1-16 molecule under alkaline environment.

Preparation and Characterization of Polyacrylonitrile-Metal-O-MMT Nanocomposites

Polyacrylonitrile-metal-O-montmorillonite nanocomposites were prepared by means of in situ polymerization. The Na-montmorillonite was modified by quaternary ammonium salt after the exchange of its interlayer cations with Ni2+. Infrared spectra and X-ray powder diffraction were employed to characterize the obtained polyacrylonitrile-metal-O-montmorillonite. The results of FTIR show that metal-O-montmorillonite has been concerned with the polymerization of PAN. The result of X-ray powder diffraction shows that the inserting of the acrylonitrile monomer can enlarge the interlayer space of montmorillonite. It is also shown that the polyacrylonitrile-metal-O- montmorillonite nanocomposites have been synthesized. The thermal stability of PAN /MMT is better than that of pure PAN.

Co(II)-exchanged montmorillonite with ethylenediamine, trimethyl- and tetramethyl-ethylenediamine and their thermal decomposition

The influence of different steric properties of ethylenediamine (EDA), trimethylenediamine (TrMeEDA) and tetraethylenediamine (TeMeEDA) on the type of interactions with Co(II)-exchanged montmorillonite and thermal decomposition of these materials were studied. The results of X-ray diffraction (XRD), thermogravimetry (TG), derivative thermogravimetry (DTG) and spectral analysis shows that the studied ethylenediamines are intercalated into the interlayer space of montmorillonite. Thermal decomposition at 20–500 °C of studied samples with EDA proceeds in three steps (the release of chemosorbed amines, coordinated EDA and dehydroxylation) while the sample with TrMeEDA and TeMeEDA in five steps (also release the protonated forms). The effect of different steric properties of individual diamines is evident.

Simultaneous Intercalation of Two Quaternary Phosphonium Salts Into Montmorillonite

AbstractIntercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites.Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montmorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed — the proportional influence of individual components was found to be more prominent.

Sorption of dissolved mercury (II) species on calcium-montmorillonite: an unusual pH dependence of sorption process

In this paper, the special sorption properties of mercury(II) on calcium-montmorillonite is shown. Mercuric hydroxide (Hg(OH)2) produced by the hydroly- sis of mercuric ions is fairly soluble, solubility is 3.2 9 10 -4 mol/dm 3 . As a result, indifferently of the usual behavior of other hydroxides, it remains in the aqueous solution. The sorption properties are determined by the fact: there is no precipitation at higher pH values. Mont- morillonite contains permanent as well as pH-dependent charges, so the cation exchange on the permanent changes, in the interlayer space of montmorillonite and the sorption of neutral mercuric hydroxide molecules can be studied simultaneously. So, two interfacial processes of the same substance, namely the ion exchange of hexahydrate mer- curic(II) ions and the sorption of neutral mercuric hydroxide molecules, can be studied in the same system.

Polymeric Fe/Zr pillared montmorillonite for the removal of Cr(VI) from aqueous solutions

Four kinds of pillared montmorillonites were prepared by intercalating poly-hydroxyl iron, poly-hydroxyl iron/zirconium with different Fe/Zr molar ratios (4/1, 1/1) and poly-hydroxyl zirconium into the interlayer space of sodium-saturated montmorillonite (Na-Mt) via ion-exchange, termed Fe-Mt, Fe/Zr 4:1-Mt, Fe/Zr 1:1-Mt and Zr-Mt, respectively. The obtained materials were characterized by X-ray fluorescence (XRF) spectra, X-ray diffraction (XRD) spectra, Fourier transform infrared (FTIR) spectra, point of zero charge measurement and BET analysis. Batch experiments were conducted to investigate the adsorption behavior of Cr(VI) on selected samples. The results showed that the equilibrium uptake of Cr(VI) was highly pH-dependent with an optimal pH range of 3.0–6.0. The kinetics of Cr(VI) adsorption could be described well by the Pseudo-second-order model. The Langmuir adsorption isotherm provided the best correlation of the equilibrium data, and the estimated maximum equilibrium uptake of Cr(VI) of Fe/Zr 4:1-Mt was 22.35 mg/g at pH 3.0, 25 °C, higher than those of other three samples. Also, the thermodynamic parameters demonstrated that the process of Cr(VI) adsorption onto pillared montmorillonites was spontaneous and exothermic in nature. The presence of phosphate, sulphate and tartrate inhibited markedly the adsorption of Cr(VI), whereas nitrate, chlorate and acetate exhibited no significant effect on Cr(VI) adsorption. The analyses combining characterization results with adsorption data revealed that the removal mechanisms of Cr(VI) by these pillared montmorillonites mainly involved electrostatic interaction and ion-exchange. Overall, the regeneration of Fe/Zr-Mt could be achieved using NaOH solution, enabling a promising application for removing Cr(VI) from aqueous solution.

Formation of ZnS and CdS in the interlayer spaces of montmorillonite

Two types of semiconductor particles, ZnS and CdS, were formed in the interlayer spaces of montmorillonite by solid–solid reactions between Zn(II)- or Cd(II)-montmorillonite and Na 2S at ambient temperature. The formation of the intercalation compounds was confirmed by powder XRD, TG–DTA and TG–MS. The in situ formation of ZnS and CdS nanoparticles in the interlayer spaces of montmorillonite was proved by UV–visible and photoluminescence spectroscopy. The diffuse reflectance absorption spectra of ZnS and CdS-montmorillonites exhibited the absorption onset at 345 and 541 nm, confirming the formation of ZnS and CdS nanoparticles in the interlayer spaces. The ZnS or CdS luminescence band at 583 nm for ZnS-montmorillonite or 529 nm for CdS-montmorillonite was weak due to the presence of quenching impurities in montmorillonite.

Antimicrobial properties of tetracycline and minocycline-montmorillonites

The antimicrobial activity of adsorption complexes of antibiotics from the tetracycline family on sodium and calcium montmorillonite was evaluated for their use in human and veterinary medicine. Tetracycline (TC) and minocycline (MC) adsorption on Patagonian montmorillonite was studied as a function of pH using batch experiments, X-ray diffraction (XRD) and IR spectroscopy. The adsorption was high at low pH and decreased continuously as pH increased. Adsorption of MC was higher than adsorption of TC. TC and MC were intercalated into the interlayer space of montmorillonite as deduced from the increase of the basal spacing. IR spectroscopy suggested that NHR 3 + and other polar groups were directly involved in the interaction with montmorillonite. The antimicrobial activity, measured by inhibition tests, was maintained by the antibiotics after adsorption on montmorillonite, whereas unreacted montmorillonite did not show any antibacterial activity. The excellent activity shown by the TC and MC complexes provides a promising field of application, in particular for the formulation of topical products.

Structure and thermal behaviour of polyhedral oligomeric silsesquioxane modified montmorillonite

This paper reports the structure of polyhedral oligomeric silsesquioxane (POSS)–octaammonium in the interlayer space of montmorillonite. The ion exchange reaction was conducted with a large excess of POSS and yielded which was investigated by EDX, XRD, FTIR and TGA coupled with GC/MS. All eight aminopropyl groups of cubic POSS were flexible enough to interact with the negative sites on montmorillonite yielding an alignment of the POSS in the interlayer space. POSS–MMT complex was calcinated and characterized by XRD. Since the basal spacing did not change, the calcinated MMT was supposed to be stabilized by polyhedral oligomeric silsesquioxane pillars. This kind of open and stable pillared structure can be useful for many applications such as new supports for catalysis.

Nanoscale organic/inorganic hybrids based on self-organized dendritic macromolecules on montmorillonites

This article is intended to investigate the aspects regarding the nanoscale organic/inorganic hybrids base on dendritic molecules, and the issues that arises from the use of self-assembly approach upon layered templates for the construction of functional materials. A facile synthesis of polyurea(urethane)/malonamide dendrons (from generation one, G1, to generation three, G3) with phenyl rings (P), decyl groups (D), or azo chromophores (disperse red 1; DR1) in the exterior was developed first. The dendrons consisting of secondary amine functional group in the focal point were successfully introduced into the interlayer space of montmorillonite (MMT) to prepare a series of dendron/MMT nanohybrids that reveal intercalated and exfoliated morphology. We were able to explore the possibility of obtaining the layer spacing up to 126 Å via embedding various dendrons into the silicate interlayers, and to investigate the intercalating effects of different molecular sizes and shapes. These results indicate that organic/inorganic nanohybrids resulting from the association of dendrons and inorganic clay minerals can be contributed by a direct self-assembly of hydrophobic dendrons in the layered confinement. Through embedding the void-rich dendritic molecules into interlayers, these new organic/inorganic layered nanohybrids might possess potential applications for nano-containers, nano-reactors, electro-optical materials, etc.

Facile synthesis and catalytic properties of titanium containing silica-pillared clay derivatives with ordered mesoporous structure through a novel intra-gallery templating method

Facile synthesis of titanium containing silica-pillared clay derivatives with ordered mesoporous structure from a novel intra-gallery templating route is successfully established. The ordered mesoporous titanium containing silica-pillared clay materials obtained by a surfactant-directed assembly of silica species in the interlayer space of natural montmorillonite, are characterized by a mesoporous structure with uniform pores (2.7 nm) between the layers. These results indicate that surfactant plays a decisive role in pore formation, because it acts as a micelle-like template during the hydrolysis of organic precursor. The main titanium species was tetrahedrally coordinated in the gallery silica framework. The increase of Ti content leads to a gradual reduction of quality of pore structure and of the pore volumes. Up to a Ti loading corresponding to Si/Ti = 20 the titanium is mainly tetracoordinated and the highest conversions of cyclohexene with anhydrous tert-butylhydroperoxide are obtained, with excellent selectivity for the epoxide. However, a further increase of Ti content to Si/Ti of 10 and 5, leads to an undesirable decrease of conversion and selectivity.