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Introduction Layered double hydroxides (LHDs) are also known as hydrotalcite like materials or anionic clays. Many LDHs such as hydrotalcite, takovite, carrboydite, reevesite, honessite, pyroaurite, and iowaite occur in nature

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Abstract  

The synergistic effects of zinc oxide (ZnO) with layered double hydroxides (LDH) in ethylene vinyl acetate copolymer/LDH (EVA/LDH) composites have been studied using thermal analysis (TG), limiting oxygen index (LOI), UL-94 tests, and cone calorimeter test (CCT). The results from the UL-94 tests show that the ZnO can also act as flame retardant synergistic agents in the EVA/LDH composites. The CCT data indicated that the addition of ZnO in EVA/LDH system can greatly reduce the heat release rate. The TG data show that the ZnO can increase the thermal degradation temperature and the charred residues after burning.

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In the present study, Mg–Al layered double hydroxide intercalated with nitrate anions (LDH-NO3) was synthesized, modified with the anionic surfactant, sodium lauryl sulfate, and applied for the removal of 152+154Eu from aqueous solutions. Modification of the as-synthesized Mg–Al layered double hydroxide was carried out at surfactant concentration of 0.01 M (the organo-LDH produced denoted LDH-NaLS). The as-synthesized and surfactant-intercalated LDHs were characterized by FT-IR and energy-dispersive X-ray spectroscopy techniques. The effect of some variables such as solution pH, contact time and sorbate concentration on removal of 152+154Eu was investigated. The kinetic data obtained were well fitted by the pseudo-second-order kinetic model rather than the pseudo-first-order model. Intraparticle diffusion model showed that sorption of 152+154Eu proceed by intraparticle diffusion together with boundary layer diffusion. Experimental isotherm data were well described by Langmuir model. Organo-LDH was found to have higher capacity (156.45 mg g−1) for europium than the as-synthesized LDH-NO3 (119.56 mg g−1). Comparing LDHs capacities obtained for Eu(III) in the present work with other sorbents reported in literature indicated that LDHs have the highest capacities. Application of the developed process for removal of 152+154Eu(III) from radioactive process wastewaters was also studied and the obtained results revealed that these LDHs are promising materials for treatment of radioactive wastewaters.

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Introduction Layered double hydroxides consist of positively charged metal hydroxide layers and exchangeable interlayer ions and water molecules. The general formula of these lamellar solids is [M 1− x II M x III (OH) 2 ] x

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Journal of Thermal Analysis and Calorimetry
Authors: Tomohito Kameda, Yuki Fubasami, and Toshiaki Yoshioka

Introduction Mg–Al layered double hydroxide (Mg–Al LDH) is represented by the formula [Mg 1− x 2+ Al x 3+ (OH) 2 ](A n − ) x / n · m H 2 O, where A n − is an anion, such as CO 3 2− or SO 4 2− , and x is the Al/(Mg + Al

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Viorel Chihaia, Karl Sohlberg, Margarita Gabrovska, Rumeana Edreva-Kardjieva, Dorel Crişan, Peter Tzvetkov, Maya Shopska, and Iskra Shtereva

–Al takovite-like layered double hydroxides of different degree of crystallization depending on the Ni 2+ /Al 3+ ratio. A single takovite-like phase was registered only in the sample of the highest nickel loading (Ni 2+ /Al 3+ = 3.0). An excess of aluminum in

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Introduction Layered double hydroxides (LDHs) are layered compounds composed of positively charged metal hydroxide sheets with intercalated anions and water molecules in the interlayer region. They are also known as

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Abstract  

Anionic surfactant and silane modified layered double hydroxides (LDHs) were synthesized through an in situ coprecipitation method. The structure and morphology were characterized by XRD and TEM techniques, and their thermal decomposition processes were investigated using infrared emission spectroscopy (IES) combined with thermogravimetry (TG). The surfactant modified LDHs (H-DS) shows three diffractions located at 1–7° (2θ), while there is only one broad reflection for silane grafted LDHs (H–Si) in this region. The morphologies of the H-DS and H–Si show fibrous exfoliated layers and curved sheets, respectively. The IES spectra and TG curves indicate that alkyl chain combustion and dehydroxylation are overlapped with each other during heating from 373 to 723 K in H-DS and to 873 K in H–Si. Sulfate anion transformation process occurs at 473 K in H-DS and 523 K in H–Si. The derivant of sulfate can exist even above 1073 K. After further decomposition, the metal oxides and the new type of Si–O compounds are formed beginning at around 923 K in silane modified sample.

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Syntheses, structures and properties of nanobiohydrids based on the anions of biologically important organic molecules and various layered double hydroxides (LDHs) are reviewed. Emphasis has been laid on collecting works on the controlled delivery and release of LDH-intercalated pharmaceutically important compounds as well as chemicals used as herbicides.

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Abstract  

The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min−1. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures. The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs. The kinetic parameters (reaction order (n) apparent activation energy (E a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined.

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