12 research outputs found
Characterization and Applications of Kaolinite Robustly Grafted by an Ionic Liquid with Naphthyl Functionality
Functionalization of the kaolinite (K) interlayer space is challenging. In this work, a new kaolinite-based nanohybridmaterial (K-NI) was successfully synthesized by grafting on the interlayer aluminol surfaces the ionic liquid, 1-(1-methylnaphthyl)-3-(2-hydroxyethyl) imidazolium chloride (NI), using a guest displacement strategy. A substantial increase of the basal spacing (10.8 Ă…) was obtained. This is a grafted derivative of kaolinite possessing one of the largest d-values. Washing in water for several days and other vigorous treatments such as sonication showed a minor effect on the integrity of the material. FTIR and 13C NMR confirmed the conservation of the structure of the ionic liquid after the grafting. Thermal analysis confirmed the presence of grafted material and was used to estimate the abundance of the grafted ionic liquid (0.44 mole per mole of kaolinite structural formula, (Al2Si2O5(OH)4)). By using cyclic voltammetry, the permeability of a film of K-NI for the bulky ferricyanide ions was demonstrated. The accumulation of nitrophenolate anions was effective (maximum capacity of 190 ÎĽmol/g), but was less important than what was expected due to the steric hindrance of the bulky grafted NI. Although the presence of chloride anions reduced the adsorption capacity, the affinity of the modified kaolinite interlayer space for the nitrophenolate anions was demonstrated
Characterization and Applications of Kaolinite Robustly Grafted by an Ionic Liquid with Naphthyl Functionality
Functionalization of the kaolinite (K) interlayer space is challenging. In this work, a new kaolinite-based nanohybridmaterial (K-NI) was successfully synthesized by grafting on the interlayer aluminol surfaces the ionic liquid, 1-(1-methylnaphthyl)-3-(2-hydroxyethyl) imidazolium chloride (NI), using a guest displacement strategy. A substantial increase of the basal spacing (10.8 Ă…) was obtained. This is a grafted derivative of kaolinite possessing one of the largest d-values. Washing in water for several days and other vigorous treatments such as sonication showed a minor effect on the integrity of the material. FTIR and 13C NMR confirmed the conservation of the structure of the ionic liquid after the grafting. Thermal analysis confirmed the presence of grafted material and was used to estimate the abundance of the grafted ionic liquid (0.44 mole per mole of kaolinite structural formula, (Al2Si2O5(OH)4)). By using cyclic voltammetry, the permeability of a film of K-NI for the bulky ferricyanide ions was demonstrated. The accumulation of nitrophenolate anions was effective (maximum capacity of 190 ÎĽmol/g), but was less important than what was expected due to the steric hindrance of the bulky grafted NI. Although the presence of chloride anions reduced the adsorption capacity, the affinity of the modified kaolinite interlayer space for the nitrophenolate anions was demonstrated
Functionalization of synthetic saponite: identification of grafting sites and application for anions sequestration
The present work reports the study of the mechanism of grafting of an alkoxysilane on the surface of a synthetic saponite. XRD and SEM/EDX characterizations confirmed the effective synthesis of the clay mineral with structural formula INTNa0.50TET[Si3.50Al0.50]OCT[Mg3]O10(OH)2. The functionalization of this material in its pristine or acid pre-treated form with a cationic silane (tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride) yielded a nanohybrid organoclay with interesting structural and chemical properties highlighted by 29Si solid state NMR, XRD, FTIR, TGA and electrochemical characterizations. The monodentate and bidentate grafting of the alkoxysilane was observed regardless the starting material was pristine or acid pre-treated saponite. The more significant layer-to-layer distance increase observed after the functionalization of acid pre-treated saponite indicated some interlayer intercalation/grafting of the alkoxysilane. Electrochemical characterization (cyclic voltammetry and electrochemical impedance spectroscopy) showed that the modified clay mineral exhibited anionic exchange property due to the presence of grafted cationic alkoxysilane. This anionic exchange capacity was confirmed when successfully applied for the adsorption of the anionic dye Congo Red. In all cases, the acid pre-treatment tended to improve the anion exchange property of the organoclay
Encapsulation of butylimidazole in smectite and slow release for enhanced copper corrosion inhibition
International audienceButylimidazole (Bim) a well-known copper corrosion inhibitor was encapsulated in its cationic form, in a smectite type clay mineral (Sabga clay mineral (Sg)) by cation exchange of sodium cations located in the interlayer space of the layered clay mineral. Physicochemical characterization (XRD, FT-IR and TGA) revealed that Bim was intercalated (0.48 mmol per gram of hybrid material) in its cationic form. The intercalation was followed by an increase of the layer to layer distance from 11.4 Ă… to 13.9 Ă…. The composite material (Sg-Bim) was then applied as copper corrosion inhibitor in concentrated sodium sulphate solution (0.1 M) and experiments monitored electrochemically. For a given concentration of Sg-Bim, the corrosion potential increased as a function of time. The corrosion inhibition percentages obtained both by corrosion current densities (up to 80.7%) and charge transfer resistance (up to 87.0%) were found to increase with the release time. This confirmed that the clay mineral Sg effectively served as a nanocontainer for the encapsulation of Bim. Moreover, the release of Bim occurred gradually when the organoclay was immersed in concentrated saline solution. Investigations on the effect of temperature on the process confirmed that the action of released Bim against copper corrosion consisted in improving the stability of the Cu2O protecting layer, according to a physisorption mechanism
Molecule-surface recognition between heterocyclic aromatic compounds and kaolinite in toluene investigated by molecular theory of solvation and thermodynamic and kinetic experiments
Molecular recognition interactions between kaolinite and a series of heterocyclic aromatic compounds (HAC) representative of the N- and S-containing moieties in petroleum asphaltene macromolecules are investigated using the three-dimensional reference interaction site model with the Kovalenko-Hirata closure approximation (3D-RISM-KH) theory of solvation and experimental techniques in toluene solvent. The statistical-mechanical 3D-RISM-KH molecular theory of solvation predicts the adsorption configuration and thermodynamics from the 3D site density distribution functions and total solvation free energy, respectively, for adsorption of HAC and toluene on kaolinite. Spectrophotometric measurements show that, among the HAC studied, only acridine and phenanthridine adsorb quantitatively on kaolinite. For these pyridinic HAC, the adsorption results fitted to the Langmuir isotherm in the monolayer domain suggest a uniform monolayer of HAC molecules. The 3D-RISM-KH studies predict that the aluminum hydroxide surface of kaolinite is preferred for HAC adsorption due to strong hydrogen bonding with the pyridinic N atoms, while the rest of the HAC adsorb weaker. Adsorption on the silicon oxide side is weak and delocalized, as evident from the 3D solvation free energy density. Toluene sites effectively compete with non-hydrogen bonding HAC, such as fused thiophenes, for the kaolinite surface. The adsorption enthalpy and phenanthridine-acridine loading ratio are calculated and correlated with the experimentally determined Langmuir constant and adsorption loading. This combined experimental and computational modeling approach is aimed to provide insight into the specific interactions among clays, bitumen, and solvents so as to help accelerate the development of environmentally friendly and efficient desorption systems for nonaqueous extraction of bitumen from Oil Sands, an important unconventional petroleum reserve.Peer reviewed: YesNRC publication: Ye
Adsorption of Indole on Kaolinite in Nonaqueous Media: Organoclay Preparation and Characterization, and 3D-RISM-KH Molecular Theory of Solvation Investigation
Current
oil sand mining operations in the Athabasca basin are predominantly
aqueous-based. Extracts containing large amounts of fines lead to
the formation of stable organoclay suspensions in froths giving lower
yields and greater tailing wastes and making the development of more
efficient extraction methods desirable from both economical and environmental
perspectives. We examine an indole-kaolinite system as a model for
these oil fines and their resistance to washing in nonaqueous solvents.
The prepared organoclays show indole loading exclusively on the external
surface of the clay. Micron-scaled vermicular structures, similar
to natural kaolinite, are observed. Their formation is believed to
be driven by strong adsorbate–adsorbate interactions. Indole
is the primary adsorbate, as solvent adsorption is shown to be minimal
based on both experimental and computational results. Isotherms are
constructed and parameters calculated from linear regression analysis
fitted to the Brunauer–Emmett–Teller equation. Monolayer
quantities calculated match well to the theoretical amount calculated
from surface areas measurements. Washing the organoclays with both
toluene and isopropanol results in a 50% decrease of loaded organic
material, leaving a monolayer equivalent of organic matter. The statistical-mechanical
3D-RISM-KH molecular theory of solvation is employed to perform full
sampling of solvent orientations around a kaolinite platelet and gain
insights into the preferred orientation and adsorption thermodynamics
of indole on kaolinite in toluene and heptane solvents. In its preferred
orientation, indole is hydrogen-bonded to one or two O atoms at the
aluminum hydroxide surface of kaolinite. The calculated solvation
free energy and potential of mean force for adsorption of indole and
solvents on kaolinite in solution yield the increasing adsorption
strength order of heptane < toluene < indole on the aluminum
hydroxide surface. Multilayer adsorption profiles are predicted based
on the integrated three-dimensional distribution functions of indole,
toluene, and heptane
Molecule–Surface Recognition between Heterocyclic Aromatic Compounds and Kaolinite in Toluene Investigated by Molecular Theory of Solvation and Thermodynamic and Kinetic Experiments
Molecular recognition interactions
between kaolinite and a series of heterocyclic aromatic compounds
(HAC) representative of the N- and S-containing moieties in petroleum
asphaltene macromolecules are investigated using the three-dimensional
reference interaction site model with the Kovalenko–Hirata
closure approximation (3D-RISM-KH) theory of solvation and experimental
techniques in toluene solvent. The statistical-mechanical 3D-RISM-KH
molecular theory of solvation predicts the adsorption configuration
and thermodynamics from the 3D site density distribution functions
and total solvation free energy, respectively, for adsorption of HAC
and toluene on kaolinite. Spectrophotometric measurements show that,
among the HAC studied, only acridine and phenanthridine adsorb quantitatively
on kaolinite. For these pyridinic HAC, the adsorption results fitted
to the Langmuir isotherm in the monolayer domain suggest a uniform
monolayer of HAC molecules. The 3D-RISM-KH studies predict that the
aluminum hydroxide surface of kaolinite is preferred for HAC adsorption
due to strong hydrogen bonding with the pyridinic N atoms, while the
rest of the HAC adsorb weaker. Adsorption on the silicon oxide side
is weak and delocalized, as evident from the 3D solvation free energy
density. Toluene sites effectively compete with non-hydrogen bonding
HAC, such as fused thiophenes, for the kaolinite surface. The adsorption
enthalpy and phenanthridine-acridine loading ratio are calculated
and correlated with the experimentally determined Langmuir constant
and adsorption loading. This combined experimental and computational
modeling approach is aimed to provide insight into the specific interactions
among clays, bitumen, and solvents so as to help accelerate the development
of environmentally friendly and efficient desorption systems for nonaqueous
extraction of bitumen from Oil Sands, an important unconventional
petroleum reserve