Effect of non-swelling layers on the dissolution of reduced-charge montmorillonite in hydrochloric acid

Komadel, Peter; Bujdák, Juraj; Madejová, Jana; Šucha, Vladimír; Elsass, Françoise

doi:10.1180/claymin.1996.031.3.04

Cited by 92 publications

(48 citation statements)

References 12 publications

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“…The characteristic band at 915 cm À1 is due to Al À Al À OH stretching in the octahedral layer and the band at 538 cm À1 is due to the Al À O À Si stretching mode. [25,26] For APZ-MMT and AEAcoated APZ-MMT, the characteristic bands of APZ were overlapped in their spectra (Figure 2 A, spectra c and d), thus indicating that the APZ molecules were stabilized in the interlayer space through electrostatic interactions without structural changes. However, after hybridization, the OH stretching peak, which was observed at 3443 cm À1 with pristine MMT, shifted to a lower wavenumber (3428 cm À1 ), owing to the interactions between APZ and MMT, which proceeded through a water-bridging mechanism (Figure 2 B).…”

Section: Resultsmentioning

confidence: 92%

AripiprazoleMontmorillonite: A New Organic–Inorganic Nanohybrid Material for Biomedical Applications

Choi

Choy

et al. 2013

Chemistry A European J

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Poor aqueous solubility and the unpleasant taste of aripiprazole (APZ) have been recurring problems, owing to its low bioavailability and low patient tolerance, respectively. Herein, we prepared a nanohybrid system that was based on a bentonite clay material, montmorillonite (MMT), which could both mask the taste and enhance the solubility of APZ (i.e., APZ-MMT). To further improve the efficacy of this taste masking and drug solubility, APZ-MMT was also coated with a cationic polymer, polyvinylacetal diethylamino acetate (AEA). In vitro dissolution tests at neutral pH showed that the amount of drug that was released from the AEA-coated APZ-MMT was greatly suppressed (<1%) for the first 3 min, thus suggesting that AEA-coated APZ-MMT has strong potential for the taste masking of APZ. Notably, in simulated gastric juice at pH 1.2, the total percentage of APZ that was released within the first 2 h increased up to 95% for AEA-coated APZ-MMT. Furthermore, this in vitro release profile was also similar to that of Abilify®, a commercially available medication. In vivo experiments by using Sprague-Dawley rats were also performed to compare the pharmacokinetics of AEA-coated APZ-MMT and Abilify®. AEA-coated APZ-MMT exhibited about 20% higher systemic exposure of APZ and its metabolite, dehydro-APZ, compared with Abilify®. Therefore, a new MMT-based nanovehicle, which is coated with a cationic polymer, can act as a promising delivery system for both taste masking and for enhancing the bioavailability of APZ.

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Section: Resultsmentioning

confidence: 92%

AripiprazoleMontmorillonite: A New Organic–Inorganic Nanohybrid Material for Biomedical Applications

Choi

Choy

et al. 2013

Chemistry A European J

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“…Collapsed, pyrophyllite-like layers are formed upon nearly complete charge reduction (85-90%) in Li-saturated dioctahedral smectites with an initial layer charge located in the octahedral sheets (Brindley and Ertem, 1971;Ertem, 1972;Lim and Jackson, 1986;BujdSk et al, 1991BujdSk et al, , 1992Komadel et al, 1996). This transformation has been used to distinguish montmorillonite from beidellite (Greene-Kelly, 1953;Schultz, 1969;Lim and Jackson, 1986).…”

Section: Layer Charge Reductionmentioning

confidence: 99%

Methylene Blue Interactions with Reduced-Charge Smectites

Bujdák

2001

Clays and clay miner.

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Abstract--The objective of this work was to prepare series of reduced-charge materials from different parent Li-saturated dioctahedral smectites, to investigate the effects of temperature, chemical composition and charge location in smectites on the charge reduction and to characterize reduced-charge smectites (RCSs) using methylene blue (MB) adsorption. The layer charge decrease, induced by Li fixation, is correlated with the trends in the spectra of MB-RCS dispersions in the visible region (VIS) spectra. Distribution of the negative surface charge of the clay minerals controls the distance between the adsorbed MB cations and thus affects the formation of MB dimers and higher agglomerates. Because each form of MB (monomer, dimer, higher agglomerate, J-aggregates) absorbs light at a different wavelength, the VIS spectra of MB depend sensitively on the charge density at the clay surface. Both cation exchange capacity (CEC) values and spectra of MB-clay dispersions clearly detect extensive reduction of the layercharge density in reduced-charge montmorillonites (RCMs) upon Li-thermal treatment. The extent of charge reduction depends on the temperature of the thermal treatment, as well as on the octahedral charge of the montmorillonite. Reduction of the layer charge proceeds to a much lesser extent for smectites with mainly tetrahedral charge and high Fe content (Fe-rich beidellite and ferruginous smectite). Both CEC data and MB spectra detect only a slight decrease of the layer charge density, which relates to the low octahedral charge of these minerals. Following heating at higher temperatures (120-160~ slightly higher Li fixation is indicated by CEC values; however, no charge reduction is confirmed by MB spectra. Release of protons accompanying Li + fixation in Fe-rich smectites heated at 180 or 200~ was detected in the spectra of MB-clay dispersions and confirmed by potentiometric titrations.

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“…Johnston et al (1992) and Schuttlefield et al (2007) used FTIR to study water interactions and uptake, respectively, onto clay minerals. Komadel et al (1996) monitored HCl and temperature-induced structural changes in reduced-charge montmorillonites via FTIR analyses. Octahedral sheet evolution with progressive kaolinization was studied by Cuadros and Dudek (2006) using mixed kaolinite-smectite samples and transmission FTIR spectroscopy.…”

Section: Phyllosilicatesmentioning

confidence: 99%