Interlayer Space Of Vermiculite Research Articles

Vermiculite modified with alkylammonium salts: characterization and sorption of ibuprofen and paracetamol

In this work, the clay mineral vermiculite (VT) was treated using the bromide form of quaternary alkylammonium salts—ethylhexadecyldimethylammonium (EHDDMAB), hexadecyltrimethylammonium (HDTMAB), tetradecyltrimethylammonium (TDTMAB) and tetrabutylammonium (TBAB), in order to obtain the organo-vermiculites (OVT) named as VT-EHDDMA, VT-HDTMA, VT-TDTMA and VT-TBA, respectively. These sorbents and the precursor VT were characterized using several techniques which allowed to infer the intercalation of the alkylammonium salts in the interlayer space of VT, except VT-TBA, and these materials were evaluated as sorbents for ibuprofen and paracetamol. VT and OVT presented no significant interactions with paracetamol and sorbed less than 10% of the initial concentration. On the other hand, two OVT sorbents demonstrated high efficiency in the sorption of ibuprofen, and the maximum percent removal was higher than 92% for VT-EHDDMA and VT-HDTMA, with a maximum sorption capacity of 52 ± 2 mg g−1 (VT-EHDDMA) and 54 ± 2 mg g−1 (VT-HDTMA), whereas 16 ± 2 mg g−1 was observed for VT. These results suggest that the low-cost OVT could be considered as appropriate sorbent for ibuprofen removal from aqueous medium, and probably as a promising sorbent for drugs of a wide polarity range, with neutral, acid and basic characteristics.

Hydroxy-interlayered minerals in the Holocene paleosol on the southernmost Loess Plateau, China

The presence and formation of hydroxy-interlayered minerals in the Holocene paleosol at the Wugong profile on the southernmost Chinese Loess Plateau were investigated by examining the < 1 μm and 1–2 μm clay fractions of the 50–150 cm horizon by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Prior to the analyses free Al and Fe phases were removed by dithionite-citric-bicarbonate (DCB) extraction. XRD patterns were obtained with air-dried, Mg-saturated, Mg-saturated with glycerol solvation (Mg-glycerol) and K-saturated and heated at 110, 250, 350, 450 and 550 °C samples both before and after hydroxy-interlayered materials removal by sodium citrate extraction. The absorption bands at 3699 and 3430 cm− 1 in the FTIR spectra of both sub-fractions indicated the presence of hydroxy-interlayered minerals. The K-saturated and heated XRD patterns confirmed this by the progressive collapse of the 1.4 nm reflection to a 1.0 nm reflection. After removal of the hydroxy-interlayered materials no obvious increase of the relative XRD intensity of the 1.8 nm reflection in Mg-glycerol pattern was observed and the 1.4 nm reflection exhibited a stronger collapse to 1.0 nm after K-saturation and increasing temperature treatment. This indicated that the hydroxy-interlayered minerals in the Holocene paleosol were mainly composed of hydroxyl-interlayer vermiculite. The hydroxyl-interlayer vermiculite was formed by the polymerization of Al/Fe-hydroxy materials within the interlayer space of vermiculite. Shoulder-like reflection at 1.2 nm in the K-550 °C pattern of the 1–2 μm fraction indicated a higher degree of Al/Fe-hydroxylation in the coarse fraction than in the fine fraction, which was consistent with the lower extractable Al and Fe in the coarse fraction. The reflection at 1.38 nm in the K-550 °C pattern could be interpreted as pedogenic chlorite. Thus, transformation of vermiculite into hydroxy-interlayered vermiculite and finally into a chlorite-like mineral (pedogenic chlorite) has occurred in the Holocene paleosol on the southernmost Chinese Loess Plateau.

Experimental evidence of the contrasting reactivity of external vs. interlayer adsorption sites on swelling clay minerals: The case of Sr2 +-for-Ca2 + exchange in vermiculite

The potential contrasting reactivity of external (edge and basal) and interlayer adsorption sites is studied by investigating the Sr2+-for-Ca2+ exchange in three different size fractions (0.1–0.2, 1–2, and 10–20μm) of vermiculite. For a given equivalent fraction of Sr2+ in solution, the obtained experimental adsorption isotherms showed that the equivalent fraction of adsorbed Sr2+ on the solid decreased with decreasing particle size.Using a combination of bulk chemistry, X-ray diffraction profile modeling of 00ℓ reflections and morphological data, the interlayer site compositions were found to be independent of the vermiculite size fraction for a given chemical composition of the solution and without any preference between Ca2+ and Sr2+ cations. The lack of selectivity of both of these cations for interlayer adsorption sites [log Kint.(Ca2+/Sr2+)=0] is supported by molecular simulation results indicating that Ca2+ and Sr2+ have similar interactions with the clay surface and water molecules in the interlayer space of vermiculite. In contrast, external adsorption sites exhibited a clear preference for Ca2+ cations [−2.5<log Kext.(Ca2+/Sr2+)<−1.0]. The two-site model (i.e., interlayer and external adsorption sites), which is constrained by the relative amounts of both types of sites derived from morphological analysis, is found to well interpret experimental ion-exchange experiments.The two-site ion-exchange model derived from this study represents a morphology-constrained model with clear evidence of contrasting reactivity between external and interlayer adsorption sites. This model can be used to improve our understanding and prediction of the behavior of Sr2+ cations in contaminated soils with a wide range of particle sizes.

Ultrasound assisted preparation of chitosan–vermiculite bionanocomposite foams for cadmium uptake

The objective of this work was the development of functional bionanocomposites based on the intercalation of the cationic biopolymer chitosan in natural or in organically modified vermiculite samples under experimental conditions involving ultrasound irradiation. The resulting materials were processed as macroporous foams with the aim to apply them in the removal of Cd(II) ions from aqueous solution. Physicochemical characterization confirmed the intercalation of chitosan into the interlayer space of vermiculite, causing the exfoliation of VU layers in those bionanocomposites. They were processed as foams by means of freeze-drying resulting in materials that show interconnected elongated macropores with average diameter around 150–200μm, and the material in the cell walls exhibited a tendency to organize in parallel planes. The adsorption equilibrium data of Cd(II) on the bionanocomposite foams, carried out in batch mode, was interpreted with the Langmuir, Freundlich and Prausnitz–Radke (P–R) isotherm models, and the P-R isotherm showed the best fit to the experimental data. The adsorption capacity was increased by raising the solution pH, which most likely favors a chelation mechanism between the chitosan chains and the Cd(II) cations. The chitosan–vermiculite bionanocomposites with the highest chitosan content showed exceptionally high adsorption capacity values, at least three times higher than those of the individual components.

Adsorption Properties of Vermiculite with In Situ—Immobilized Polyaniline with Respect to Cr(VI), Mo(VI), W(VI), V(V) and P(V) Anions

Immobilization of a polyaniline (PANI) on a natural vermiculite surface immediately after polymer formation (in situ immobilization) has been performed. The adsorption properties of the modified adsorbent with respect to Cr(VI), Mo(VI), W(VI), V(V) and P(V) anions were studied. We found differences in physicochemical properties of clay samples using isotherms of nitrogen adsorption, X-ray diffraction and Fourier transform infrared spectroscopy. The experiments showed intercalation of PANI molecules into the inter-layer space of vermiculite. Adsorption isotherms and kinetics of adsorption were measured for the anionic form of ‘d’ metals of Groups V and VI in the Periodic Table from aqueous solutions by the static method. The results indicated that the synthesized composite had a high adsorption capacity with respect to Cr(VI) and Mo(VI) anions in acidic medium through the formation of dichromate anions (Cr2O72-) and an equilibrium mixture of molybdate (MoO42-) and polymolybdates ([Mo6O21]6-, [Mo7O24]6-). T...

Synthesis and Electrical Conductivity Measurement of Polyaniline / Vermiculite Nanocomposites

A series of polyaniline/vermiculite nanocomposites was synthesized. The interlayer space of vermiculite was initially increased by the insertion of dioctadecyl dimethyl ammonium bromide, and then the aniline monomers were inserted into the interlayer space of vermiculite replacing dioctadecyl dimethyl ammonium cations. The polyaniline/vermiculite nanocomposites materials were prepared via in situ polymerization of the aniline monomers in the interlayer space of vermiculite. The as-synthesized polyaniline/vermiculite nanocomposite materials were characterized by X-ray diffraction analysis, infrared spectroscopy, and electrical conductivity measurement. The results indicated that the vermiculite was peeled off into the polyaniline. The introduction of vermiculite nanosheets showed a beneficial effect on the electrical conductivity of polyaniline.

Terahertz Time-Domain Spectroscopy of Selected Layered Silicates

AbstractMicaceous layer silicate clay minerals are attractive materials for applications involving non-linear optics because of their low cost and ability to form well ordered, platy aggregates, but such applications require precise knowledge of the dielectric behavior of the clay. The purpose of the present study was to use Terahertz time-domain spectroscopy (THz-TDS) to determine the dielectric properties of certain cleavable layered clay minerals, including muscovite, vermiculite, phlogopite, and biotite. The samples were characterized by X-ray diffraction and Fourier transform infrared spectroscopy as well as chemical analysis by Energy dispersive X-ray spectroscopy. The THz frequency window investigated was the far-infrared region of 3.3 to ∼40.0 cm−1 corresponding to 0.1 and 1.2 THz, respectively. The samples were selected so that the hydrated form of the interlayer cation, e.g. Mg2+ present in the interlayer gallery of vermiculite, could be compared to species such as phlogopite, biotite, and muscovite with the dehydrated form of interlayer cations such as K+ or Na+. The frequency-dependent complex index of refraction of these natural materials was determined to vary between 2.50 and 2.80. The presence of water in the interlayer space of vermiculite was reflected in the detection of increased values of the absorption index in comparison with the muscovite, phlogopite, and biotite.

PENGARUH VALENSI KATION DALAM RUANG-ANTAR LAPISAN VERMIKULIT TERHADAP PEMBENTUKAN DAN KARAKTERISTIK KIMIA ALUMINIUMHIDROKSIVERMIKULIT

Aluminumhydroxy-smectite (AHS), known also as pillared clay, has some specific characteristics such as wide specific surface area, high basal spacing, and stable at significant high temperature. The AHS was produced from smectite and polymer aluminumhydroxy. In the industrial sector, this product can be used as cracking-catalyst, absorber, and molecular sieve up to 500°C. A similar product can be constructed from vermiculite, and the aluminumhydroxy-vermiculite (AHV) is predicted to have better thermal stability than AHS due to a higher charge density of vermiculite that adsorbs more aluminumhydroxy than that of smectite.Related to the above background the objectives of the research were to study the effects of cation valence in the interlayer space of vermiculite using Li and Ml ions in the formation process and the chemical characteristics of AHV. Li and Mg-vermiculites with different particle sizes are reacted with polymer aluminum-hydroxy' at 100 °C temperature. Solution of 2% Locron was used as a source of aluminum-hydroxy. The products were characterized by chemically and mineralogica/~v. The chemical characteristic includes total chemical analysis, whereas the mineralogical characteristic comprises basal spacing identification that was measured with an X-ray diffractometer (XRD). The results indicated that the AHV produced from Li-vermiculite showed peaks of 1.86 nm and 1.41-1.45 nm with increasing intensity of the 1.86 nm peaks as the particle size was finer. The AHV produced from Mg-vermiculite showed only a peak of 1.45 nm, whereas the 1.84 nm peak can on~v be identified as a shoulder. The AHV with a peak of 1.86 nm (AHV-I.86) can keep its basal spacing to 1.68 nm after 3 hours of heating at a temperature of 700°C, whereas the AHV-I.45 nm shrinkages to 1.10/0.98 nm at the same treatments. Chemical analysis showed that the inter/oyer space of the AHV-I.86 consists of more aluminum-hydroxy than that of the AHV-I.45. Ratio o(OH/AI o(the interlayer aluminum-hydroxy in the AHV-1.86 was 2.57, whereas that of the AHV-1.45 was 2.40.&#x0D; Keywords: Aluminum hydroxy-smectite, aluminumhydroxy-vermiculite, a pillared clay, polymer aluminumhydroxychloride, smectite. vermiculite

Solubilization of toluene in surfactant bilayers formed in the interlayer space of vermiculite

The solubilization of toluene into a cationic surfactant bilayer previously intercalated into the interlayer space of a vermiculite has been studied. Two cationic surfactants with different chain-lengths were used individually and mixed to prepare the intercalated vermiculites, which were characterized by X-ray diffraction. The intercalated complexes swelled to different extents when immersed in toluene and this has been related to the hydrophobicity and structural disorder in the interlamellar space.

Analysis of protein-labeling solutions ( 99mTc) by zonal electrophoresis

The potential contrasting reactivity of external (edge and basal) and interlayer adsorption sites is studied by investigating the Sr2 +-for-Ca2 + exchange in three different size fractions (0.1–0.2, 1–2, and 10–20 μm) of vermiculite. For a given equivalent fraction of Sr2 + in solution, the obtained experimental adsorption isotherms showed that the equivalent fraction of adsorbed Sr2 + on the solid decreased with decreasing particle size.Using a combination of bulk chemistry, X-ray diffraction profile modeling of 00ℓ reflections and morphological data, the interlayer site compositions were found to be independent of the vermiculite size fraction for a given chemical composition of the solution and without any preference between Ca2 + and Sr2 + cations. The lack of selectivity of both of these cations for interlayer adsorption sites [log Kint.(Ca2 +/Sr2 +) = 0] is supported by molecular simulation results indicating that Ca2 + and Sr2 + have similar interactions with the clay surface and water molecules in the interlayer space of vermiculite. In contrast, external adsorption sites exhibited a clear preference for Ca2 + cations [− 2.5 < log Kext.(Ca2 +/Sr2 +) < − 1.0]. The two-site model (i.e., interlayer and external adsorption sites), which is constrained by the relative amounts of both types of sites derived from morphological analysis, is found to well interpret experimental ion-exchange experiments.The two-site ion-exchange model derived from this study represents a morphology-constrained model with clear evidence of contrasting reactivity between external and interlayer adsorption sites. This model can be used to improve our understanding and prediction of the behavior of Sr2 + cations in contaminated soils with a wide range of particle sizes.