Intercalation Of Organic Anions Research Articles

Fe(III)‐Based Layered Double Hydroxides Carrying Model Naproxenate Anions: Compositional and Structural Aspects

AbstractIn this work, Al cation was gradually replaced by FeIII in the composition of Layered Double Hydroxides (LDH) and systematically investigated for LDH application as drug carriers, ultimate aiming to improve their biointegration. The incorporation of FeIII into LDH layers, as well the intercalation of organic anions in the iron‐based materials, is challenging. Several studies approach the intercalation of non‐steroidal anti‐inflammatory drugs such as anionic naproxen (NAP) into Al‐LDH. Thus, NAP was applied here as a model drug for the study of compositional and structural aspects of novel FeIII‐LDH carriers envisaging to shed light on the intercalation of other carboxylate drugs into these materials. LDH of general [M2FeyAl(1‐y)(OH)6]An− compositions (MII=Mg or Zn; An−=anion of charge n) were investigated using two synthetic methods for NAP intercalation. Full X‐ray diffraction profile refinement and a crystal‐geometrical reasoning were used to strengthen the results interpretation. Unlike coprecipitation, in which probably NAP complexation with FeIII hinders LDH‐NAP self‐assembling, topotactic ion exchange demonstrated to be a potential approach.

Innovative membrane containing iron-based layered double hydroxide intercalated with phyto therapeutic diterpenoid

This work developed an innovative membrane based on the high-performance PEBAX®2533 (PEBA) block copolymer and particles of iron-based layered double hydroxide (LDH) (Mg4FeAl layer composition) intercalated with phytotherapeutic abietate anions (ABI); both guest and host species are active in the promotion of wound healing. The presence of conjugated double bonds in the ABI structure promotes chemical reactions confronting its stability. Hence, LDH can protect the phytochemical species and promote its modified release. Aiming the development of wound dressings, LDH-ABI particles were immobilized in a biocompatible polymer (PEBA) by simple casting method. All samples were characterized by X-ray diffraction (XRD), vibrational (infrared and Raman) spectroscopies, thermogravimetry analysis coupled to mass spectrometry (TGA-MS), elemental chemical analyses and, in the case of polymer composites, by mechanical tests. Although the intercalation of organic anions into iron-based LDH materials is challenging, ABI intercalation was successful and using one-pot method (coprecipitation at constant pH value), according to XRD data. Additionally, spectroscopic techniques indicated the integrity of the ABI chemical structure after intercalation. The sodium abietate (NaABI) salt and the PEBA_NaABI membrane were also prepared to evaluate the effect of LDH in the formulations. In vitro release assays in saline solution at 32 °C showed the release (or solubilization) of around 3 and 5 wt./wt% of the ABI amount from LDH and salt, respectively, after 10 h. Comparatively, ABI release from the PEBA_Mg4FeAl-ABI and PEBA_NaABI formulations was improved to 20 and 22 wt%, respectively. The improvement in ABI release profiles from the membranes was related to the decrease in particles aggregation and improved media permeation. LDH particles released bioactive Mg2+ cations in the saline solution and, unlike NaABI particles, also improved the mechanical performance of the polymer. Thus, PEBA_Mg4FeAl-ABI showed promising as a component of wound dressings.

The Sorption of Iodine by Modified Layered Double Hydroxides from Aqueous Solutions: Effects of Intercalation Groups and Cationic Ratio

Layered double hydroxides (LDHs) have been considered as one of promising sorbents to treat radioactive iodine contaminated soil. In the study, we investigate the effects of intercalation anions and cationic ratio of LDHs on the sorption of iodine from aqueous. The results from kinetic and isotherm sorption experiments showed that intercalation of organic anions (e.g., SDBS, SDS) and higher Mg:Al ratio (e.g., 4:1) have a benefit for the sorption of iodine. The sorption affinity (L·kg−1) of iodine with LDHs followed the order: SDS (604.5) > SDBS (528.2) > Cl− (514.2) > CO3 2- (461.8) > SO4 2- (311.4) and 4:1 (2912) > 3:1 (514.2)> 2:1 (281.2). It seems that the intercalation of SDBS and SDS provide additional aromatic structures, which is responsible to the specific binding between aromatic carbon with iodine.

Layered Double Hydroxides/Multiwalled Carbon Nanotubes-Based Composite for High-Temperature CO2 Adsorption

Layered double hydroxides (LDH)-derived mixed metal oxides (MMO) are considered as promising solid sorbents for CO2 capture in the temperature range of 350–500 °C. Accordingly, they find potential applications in the sorption enhanced water–gas shift process and in removal of CO2 from hot flue gas/syngas. Numerous strategies have been explored to improve the CO2 capture property of LDH-derived MMO under the conditions of intended applications. These strategies include novel sorbents by replacement of cations and intercalation of organic anions on Mg–Al LDH, development of LDH-based hybrid/composite materials, optimization of synthesis conditions to control particle size, and method development for different types of alkali impregnation. The present work involves synthesis of a Mg–Al LDH/multiwalled carbon nanotubes (MWNTs) composite and explores its applicability for CO2 capture under dry conditions. Additionally, K2CO3 is impregnated onto the composite to study the effect of alkali promotion. The K2CO3-promoted Mg–Al LDH/MWNT composite exhibited a fresh adsorption capacity of 1.12 mmol g–1 at 300 °C under a total pressure of 1 bar. The enhanced CO2 sorption capacity of composites in comparison with their pristine counterparts can be attributed to improved particle dispersion. Further, the K2CO3-promoted Mg–Al LDH/MWNT composite shows an average working capacity of 0.81 mmol g–1 over 10 cycles in the temperature range of 300–400 °C. The deactivation model provides excellent predictions of the experimental CO2 breakthrough curves obtained with various sorbents. The values of model parameters are comparable with those reported in the literature.

Intercalation of amino acid containing chiral dicarboxylic acid between Mg–Al layered double hydroxide

Layered double hydroxide (LDH) is a class of ionic lamellar solids with positively charged layers with two types of metallic cations and exchangeable hydrated gallery anions. The intercalation of organic anions, namely N,N′-(pyromellitoyl)-bis-l-α-amino acids diacid, into Mg–Al LDHs was studied for the first time. Chiral diacid monomers were synthesized in high yield from the reaction between pyromellitic dianhydride and different natural amino acids (l-isoleucine, S-valine, l-leucine, and l-phenylalanine) in refluxed acetic acid. The anion exchange appeared to be the most effective method; all examined organic anions were intercalated successfully by this way in Mg–Al host structures. The structures of supramolecular chiral materials were characterized using Fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. Thermogravimetry analysis results showed that there were five mass loss steps during the thermal decomposition of the hybrid materials. These optically active pillars create a chiral environment and they could be used in chiral field.

Synthesis, structure and morphology of organic layered double hydroxide (LDH) hybrids: Comparison between aliphatic anions and their oxygenated analogs

Intercalation of organic anions is an important aspect of layered double hydroxide (LDH) chemistry in the development of polymer–LDH composites. In the research, we intercalated short and lengthy straight-chain organic anions with the carbon number up to 50 into the interlayer of MgAl and ZnAl-LDHs. We also noted that the packing mode of the straight-chain organic species and the basal spacing are somewhat predictable. In most cases, the hydrocarbon chain (or oxygenated) is packed in an anti-parallel inter-penetrating style at an angle of around 55°. Only when the hydrocarbon chain contains 14–18 carbons and the supplied amount of the organic anion is more than the anion exchange capacity, a so-called bi-layer packing mode is also observed. Due to the variety in the structure and property of organic hydrocarbon chains, the organo-LDH crystallites show various morphologies, where the hydrophobic forces are expected to play an important role in determining the crystallite shape.

Intercalation of colored organic anions into insulator host lattices of layered double hydroxides

Colored organic anions such as tetra (4-carboxyphenyl)porphyrin (TPP-C), tetra(4-sulfonatophenyl)porphyrin (TPP-S), tetracarboxyphthalocyaninato cobalt (TPC-C) and others were intercalated into the Mg Al and Zn Al layered double hydroxides (LDHs). After the intercalation of organic anions, interlayer spacing of the LDHs increased to 7.8–30.7 Å depending on the amounts of intercalated anions and the sizes of these anions. The amounts of intercalated organic anions reached 48–100% of the exchange capacity of the Zn Al LDH. Absorption maxima of TPP-C and TPP-S intercalates were from 439 to 445 nm and longer than 414 to 420 nm, respectively, of TPP-C and TPP-S alone in solvents.