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15 pages, 3015 KiB

Open AccessArticle

Porous Layered Double Hydroxide/TiO₂ Photocatalysts for the Photocatalytic Degradation of Orange II

by Rodrigue Djeda, Gilles Mailhot and Vanessa Prevot

ChemEngineering 2020, 4(2), 39; https://doi.org/10.3390/chemengineering4020039 - 10 Jun 2020

Cited by 11 | Viewed by 3814

Abstract

Layered Double Hydroxide (LDH)/TiO₂ nanocomposites with photocatalytic properties were synthesized by both impregnation and the direct coprecipitation of LDH matrices using a colloidal suspension of TiO₂ nanoparticles. While the two methods led to an efficient TiO₂ nanoparticle immobilization, the direct [...] Read more.

Layered Double Hydroxide (LDH)/TiO₂ nanocomposites with photocatalytic properties were synthesized by both impregnation and the direct coprecipitation of LDH matrices using a colloidal suspension of TiO₂ nanoparticles. While the two methods led to an efficient TiO₂ nanoparticle immobilization, the direct coprecipitation allowed us to tune the amount of immobilized TiO₂ within the materials. The LDH/TiO₂ nanocomposites obtained were deeply characterized by chemical analysis (ICP-AES), Powder X-ray diffraction (XRD), Fourier Transformed Infra-Red (FTIR), Thermogravimetric analysis (TGA), and High-Resolution Transmission Electron Microscopy (HRTEM). Clearly, the immobilization of TiO₂ by direct coprecipitation promoted a modification of the textural properties and a net increase in the surface area. The crystallized TiO₂ nanoparticles can be distinctly visualized by HRTEM at the surface of the layered material. Several parameters, such as the nature of the chemical composition of LDH (ZnAl and MgAl), the method of immobilization and the amount of TiO₂, were shown to play a crucial role in the physicochemical and photocatalytic properties of the nanocomposites. The photocatalytic efficiency of the different LDH/TiO₂ nanocomposites was investigated using the photodegradation of a model pollutant, the Orange II (OII), and was compared to a pure TiO₂ colloidal solution. The degradation tests revealed that the nanocomposite obtained from MgAl LDH at a low MgAl LDH/TiO₂ ratio was the most efficient for the photodegradation of OII leading to complete mineralization in 48 h. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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19 pages, 3432 KiB

Open AccessArticle

Effect of Chain Length and Functional Group of Organic Anions on the Retention Ability of MgAl- Layered Double Hydroxides for Chlorinated Organic Solvents

by Karen Maria Dietmann, Tobias Linke, Raquel Trujillano and Vicente Rives

ChemEngineering 2019, 3(4), 89; https://doi.org/10.3390/chemengineering3040089 - 28 Nov 2019

Cited by 12 | Viewed by 3079

Abstract

Nowadays, the contamination of groundwater and soils by chlorinated organic solvents is a severe and worldwide problem. Due to their swelling properties, Layered Double Hydroxides (LDHs) are potentially excellent compounds to retain chlorinated organic solvents from aquifers. By intercalating organic anions, the polarity [...] Read more.

Nowadays, the contamination of groundwater and soils by chlorinated organic solvents is a severe and worldwide problem. Due to their swelling properties, Layered Double Hydroxides (LDHs) are potentially excellent compounds to retain chlorinated organic solvents from aquifers. By intercalating organic anions, the polarity of the interlayer space can be changed from hydrophilic to hydrophobic, enhancing the adsorption of chloro-organic molecules onto the alkyl chains of intercalated organic anions. In this study, organically modified LDHs were synthesized and their efficiency was tested in batch experiments with three different chlorinated organic solvents, namely trichloroethylene, 1,1,2-trichloroethane and trichloromethane (chloroform), to examine the influence of the chain length and the functional group of the intercalated organic anion upon the retention ability of a LDH due to different electronic interactions and different sizes of the interlayer space. All synthesized and used samples were characterized using powder X-ray diffraction, thermal analysis coupled with mass spectrometry and Fourier-transform infrared spectroscopy; freshly synthesized materials were additionally analyzed regarding their particle size distribution and specific surface area. Results of the batch experiments showed that only LDHs with intercalated long-chain organic anions could be efficient adsorbents for the removal of chlorinated organic solvents from contaminated water. A selective efficiency towards 1,1,2-trichloroethane and trichloromethane can be proposed for these reactants. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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12 pages, 13186 KiB

Open AccessArticle

High-Power Ultrasonic Synthesis and Magnetic-Field-Assisted Arrangement of Nanosized Crystallites of Cobalt-Containing Layered Double Hydroxides

by Andrei N. Salak, Daniel E. L. Vieira, Irina M. Lukienko, Yuriy O. Shapovalov, Alexey V. Fedorchenko, Elena L. Fertman, Yurii G. Pashkevich, Roman Yu. Babkin, Aleksandr D. Shilin, Vasili V. Rubanik, Mário G. S. Ferreira and Joaquim M. Vieira

ChemEngineering 2019, 3(3), 62; https://doi.org/10.3390/chemengineering3030062 - 4 Jul 2019

Cited by 10 | Viewed by 3821

Abstract

High-quality stoichiometric Co₂Al–NO₃ and Co₂Al–CO₃ layered double hydroxides (LDHs) have been obtained by precipitation followed by anion exchange, both high-power-sonication assisted. Application of high-power ultrasound has been demonstrated to result in a considerable acceleration of the crystallization [...] Read more.

High-quality stoichiometric Co₂Al–NO₃ and Co₂Al–CO₃ layered double hydroxides (LDHs) have been obtained by precipitation followed by anion exchange, both high-power-sonication assisted. Application of high-power ultrasound has been demonstrated to result in a considerable acceleration of the crystallization process and the anion-exchange reaction. Two independent approaches were used to form bulk and 2-D samples of Co₂Al–NO₃ with the oriented crystallites, namely uniaxial pressing of deposits from sonicated LDH slurries and magnetic field-assisted arrangement of LDH crystallites precipitating on glass substrates. A convenient way of preparation of semi-transparent compacts with relatively big blocks of oriented crystallites have been demonstrated. Thin dense transparent films of highly-ordered crystallites of Co₂Al–NO₃ LDH have been produced and characterized. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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17 pages, 4285 KiB

Open AccessFeature PaperArticle

Investigation of Thermal Behavior of Layered Double Hydroxides Intercalated with Carboxymethylcellulose Aiming Bio-Carbon Based Nanocomposites

by Vagner R. Magri, Alfredo Duarte, Gustavo F. Perotti and Vera R.L. Constantino

ChemEngineering 2019, 3(2), 55; https://doi.org/10.3390/chemengineering3020055 - 1 Jun 2019

Cited by 23 | Viewed by 5084

Abstract

Carboxymethylcellulose (CMC), a polymer derived from biomass, was intercalated into layered double hydroxides (LDH) composed by M²⁺/Al³⁺ (M₂Al-CMC, M = Mg or Zn) and evaluated as precursors for the preparation of biocarbon-based nanocomposites by pyrolysis. M₂Al-CMC [...] Read more.

Carboxymethylcellulose (CMC), a polymer derived from biomass, was intercalated into layered double hydroxides (LDH) composed by M²⁺/Al³⁺ (M₂Al-CMC, M = Mg or Zn) and evaluated as precursors for the preparation of biocarbon-based nanocomposites by pyrolysis. M₂Al-CMC hybrids were obtained by coprecipitation and characterized by X ray diffraction (XRD), vibrational spectroscopies, chemical analysis, and thermal analysis coupled to mass spectrometry. Following, pyrolyzed materials obtained between 500–1000 °C were characterized by XRD, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Above 600 °C, Raman spectra of all samples showed the presence of graphitic carbon, which plays a role in the degree of crystallinity of produced inorganic phases (for comparison purposes, M₂Al-CO₃ materials were investigated after calcination in the same experimental conditions). XRD patterns of Mg₂Al-CMC pyrolyzed between 600–1000 °C showed poorly crystallized MgO and absence of spinel reflections, whereas for Zn₂Al-CMC, it was observed well crystallized nanometric ZnO at 800 °C, and ZnAl₂O₄ and γ-Al₂O₃ phases at 1000 °C. Above 800 °C, the carbothermic reaction was noticed, transforming ZnO to zinc vapour. This study opens perspectives for nanocomposites preparation based on carbon and inorganic (mixed) oxides through precursors having organic-inorganic interactions at the nanoscale domain. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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16 pages, 2037 KiB

Open AccessArticle

Nanohybrid Layered Double Hydroxides Used to Remove Several Dyes from Water

by Karima Abdellaoui, Ivana Pavlovic and Cristobalina Barriga

ChemEngineering 2019, 3(2), 41; https://doi.org/10.3390/chemengineering3020041 - 19 Apr 2019

Cited by 20 | Viewed by 4406

Abstract

For the preparation and characterization of several layer double hydroxides (LDH) with inorganic interlayer anions (carbonate and nitrate) and nanohybrids, two organo-LDHs were studied in detail. The dodecylbenzene sulfonate (DBS) was used as an organic interlayer anion to modify the hydrophilic nature of [...] Read more.

For the preparation and characterization of several layer double hydroxides (LDH) with inorganic interlayer anions (carbonate and nitrate) and nanohybrids, two organo-LDHs were studied in detail. The dodecylbenzene sulfonate (DBS) was used as an organic interlayer anion to modify the hydrophilic nature of the interlayer. The aim of the modification of the layered double hydroxides (LDH) was to change the hydrophilic character of the interlayer to hydrophobic with the purpose of improving its ability to adsorb several (anionic and cationic) dyes from water. These compounds have been used as adsorbents of amaranth (Am), diamine green B (DGB) and brilliant green (BG) dyes. Adsorption tests were conducted using variable pH values, contact times and initial dye concentrations (adsorption isotherms) to identify the optimum conditions for the intended purpose. Adsorbents and adsorption products were characterized by several physicochemical techniques. The results of the adsorption tests showed that the organo-LDH nanohybrids could be efficient adsorbents in the removal of studied dyes from water. Thus, it can be concluded that nanohybrids studied in this work might act as suitable supports in the design of adsorbents for the removal of a wide spectrum of dyes with the aim of reducing the adverse effects on water resources. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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14 pages, 6422 KiB

Open AccessArticle

The Formation of Layered Double Hydroxide Phases in the Coprecipitation Syntheses of [Ni_0.80Co_0.15]_(1−x)/0.95Al_x(OH)₂(anionⁿ⁻)_x/n (x = 0–0.2, n = 1, 2)

by Aaron Liu and J. R. Dahn

ChemEngineering 2019, 3(2), 38; https://doi.org/10.3390/chemengineering3020038 - 9 Apr 2019

Cited by 15 | Viewed by 5437

Abstract

This study investigates the synthesis of [Ni_0.80Co_0.15]_(1−x)/0.95Al_x(OH)₂ (x = 0–0.2) materials by coprecipitation to understand the formation of layered double hydroxide (LDH) phases as influenced by Al content and synthesis route. [...] Read more.

This study investigates the synthesis of [Ni_0.80Co_0.15]_(1−x)/0.95Al_x(OH)₂ (x = 0–0.2) materials by coprecipitation to understand the formation of layered double hydroxide (LDH) phases as influenced by Al content and synthesis route. Two routes were compared: the first method dissolved all the metal reagents into one solution before addition into the reaction vessel, while the second dissolved Al into a separate NaOH solution before simultaneous addition of the Ni/Co and Al solutions into the reaction vessel. The synthesized materials were characterized by Scanning Electron Microscopy, X-ray Diffraction, Inductively Coupled Plasma-Optical Emissions Spectroscopy and Thermogravimetric Analysis to understand the formation of LDH phases as influenced by Al content and synthesis method. It was found that as Al content increased, the amount of LDH phase present increased as well. No significant difference in LDH phase presence was observed for the two synthesis methods, but the morphologies of the particles were different. The method containing all the metals in one solution produced small particles, likely due to the continuous nucleation of Al(OH)₃ disrupting particle growth. The method containing the separate Al in NaOH solution matched the morphology of the material with no Al, which is known to form desired large spherical particles under continuously stirring tank reactor synthesis conditions. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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12 pages, 4610 KiB

Open AccessEditor’s ChoiceArticle

Layered Double Hydroxides for the Catalytic Isomerization of Linoleic Acid to Conjugated Linoleic Acids (CLAs)

by Xavier Cardó, Pilar Salagre and Yolanda Cesteros

ChemEngineering 2019, 3(1), 30; https://doi.org/10.3390/chemengineering3010030 - 10 Mar 2019

Cited by 2 | Viewed by 3022

Abstract

Several hydrotalcite-type compounds with different divalent (Mg²⁺, Ni²⁺, Cu²⁺, Zn²⁺) and trivalent (Al³⁺, Cr³⁺) cations and different ratio compositions were tested for the isomerization of linoleic acid in order to study [...] Read more.

Several hydrotalcite-type compounds with different divalent (Mg²⁺, Ni²⁺, Cu²⁺, Zn²⁺) and trivalent (Al³⁺, Cr³⁺) cations and different ratio compositions were tested for the isomerization of linoleic acid in order to study their role on the obtention of specific conjugated linoleic acids (CLAs) with anticarcinogenic and nutritional properties. This is a complex reaction due to the high number of possible isomers of linoleic acid together with the significant competition of the isomerization reaction with other secondary undesired reactions. All catalysts showed very high conversions of linoleic acid, but condensation products were mainly obtained, especially for the hydrotalcite-type compounds with higher Mg/Al ratios due to their higher Brønsted basicity and for the catalysts with higher Ni²⁺ content or with the presence of Cu²⁺, Zn²⁺ in the layers because of the influence of the higher acidity of these cations on the Brønsted basicity of the hydroxides. The best results were achieved for the catalysts with Mg/Al ratio around 2.5–3, resulting in 29–38% of selectivity to the identified CLAs. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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17 pages, 7216 KiB

Open AccessArticle

Synthesis of Chalcone Using LDH/Graphene Nanocatalysts of Different Compositions

by Mayra G. Álvarez, Dana G. Crivoi, Francesc Medina and Didier Tichit

ChemEngineering 2019, 3(1), 29; https://doi.org/10.3390/chemengineering3010029 - 9 Mar 2019

Cited by 15 | Viewed by 7534

Abstract

Layered double hydroxides (LDH) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they are generally agglomerated, inducing weak accessibility to the active sites. In the search for improving dispersion and accessibility of the active sites and for controlling [...] Read more.

Layered double hydroxides (LDH) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they are generally agglomerated, inducing weak accessibility to the active sites. In the search for improving dispersion and accessibility of the active sites and for controlling the hydrophilic/hydrophobic balance in the catalysts, nanocomposite materials appear among the most attractive. In this study, a series of nanocomposites composed of LDH and reduced graphene oxide (rGO), were successfully obtained by direct coprecipitation and investigated as base catalysts for the Claisen–Schmidt condensation reaction between acetophenone and benzaldehyde. After activation, the LDH-rGO nanocomposites exhibited improved catalytic properties compared to bare LDH. Moreover, they reveal great versatility to tune the selectivity through their composition and the nature or the absence of solvent. This is due to the enhanced basicity of the nanocomposites as the LDH content increases which is assigned to the higher dispersion of the nanoplatelets in comparison to bulk LDH. Lewis-type basic sites of higher strength and accessibility are thus created. The nature of the solvent mainly acts through its acidity able to poison the basic sites of the nanocatalysts. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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13 pages, 2835 KiB

Open AccessArticle

Reactivity and Heavy Metal Removal Capacity of Calcium Alginate Beads Loaded with Ca–Al Layered Double Hydroxides

by Andres Borgiallo and Ricardo Rojas

ChemEngineering 2019, 3(1), 22; https://doi.org/10.3390/chemengineering3010022 - 1 Mar 2019

Cited by 12 | Viewed by 4023

Abstract

Layered double hydroxides (LDHs) present multiple applications due to their versatility and reactivity. Thus, Ca–Al LDHs with Friedel’s salt structure (HC) have been proposed as heavy metal scavengers due to their buffering capacity at basic pHs. Nevertheless, the control of the reactivity of [...] Read more.

Layered double hydroxides (LDHs) present multiple applications due to their versatility and reactivity. Thus, Ca–Al LDHs with Friedel’s salt structure (HC) have been proposed as heavy metal scavengers due to their buffering capacity at basic pHs. Nevertheless, the control of the reactivity of LDHs such as HC is necessary to optimize their applications. Here, the reactivity of an HC prepared by a coprecipitation method was modified by its inclusion in calcium alginate (CaAlg) beads prepared by ionic gelation. The obtained beads (CaAlg/HC) showed good dispersion of the HC particles in the alginate matrix and were used to test the acid base reactivity and heavy metal uptake capacity compared with pure CaAlg beads and HC powder separately. The pH buffering capacity of CaAlg beads was enriched by the inclusion of HC that, in turn, was modulated in its reactivity. Thus, the HC dissolution times changed from mere seconds for the powder to tens of minutes when enclosed in the beads in a kinetic profile determined by the diffusive step. On the other hand, Cu²⁺ uptake capacity of CaAlg/HC beads combined the Cu(OH)₂ precipitation capacity of HC with the complexation capacity of alginate, reaching good affinity and capacity for the obtained beads. Nevertheless, the precipitation of the hydroxide was produced outside the bead, which would induce the addition of an additional separation step to produce an acceptable Cu²⁺ elimination. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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24 pages, 4663 KiB

Open AccessArticle

Layered Double Hydroxide Sorbents for Removal of Selenium from Power Plant Wastewaters

by Man Li, Tanzil Chowdhury, Andrea N. Kraetz, Hangkun Jing, Andrew Dopilka, Lisa M. Farmen, Shahnawaz Sinha and Candace K. Chan

ChemEngineering 2019, 3(1), 20; https://doi.org/10.3390/chemengineering3010020 - 22 Feb 2019

Cited by 12 | Viewed by 4412

Abstract

Selenium is an essential trace element but is increasingly becoming a contaminant of concern in the electric power industry due to the challenges of removing solubilized selenate anions, particularly in the presence of sulfate. In this work, we evaluate granulated layered double hydroxide [...] Read more.

Selenium is an essential trace element but is increasingly becoming a contaminant of concern in the electric power industry due to the challenges of removing solubilized selenate anions, particularly in the presence of sulfate. In this work, we evaluate granulated layered double hydroxide (LDH) materials as sorbents for selenium removal from wastewaters obtained from a natural gas power plant with the aim to elucidate the effect of competing ions on the sorption capacities for selenium removal. We first present jar test data, followed by small-scale column testing in 0.43 inch (1.1 cm) and 2 inch (5.08 cm) diameter testbed columns for the treatment of as-obtained cooling tower blowdown waters and plant wastewaters. Finally, we present field results from a pilot-scale study evaluating the LDH media for treatment of cooling tower blowdown water. We find that despite the high levels of total dissolved solids and competing sulfate ions, the selenium oxoanions and other regulated metals such as chromium and arsenic are successfully removed using LDH media without needing any pre-treatment or pH adjustment of the wastewater. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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15 pages, 3039 KiB

Open AccessArticle

Controlling the Synthesis Conditions for Tuning the Properties of Hydrotalcite-Like Materials at the Nano Scale

by Raquel Trujillano, Inés González-García, Alvaro Morato and Vicente Rives

ChemEngineering 2018, 2(3), 31; https://doi.org/10.3390/chemengineering2030031 - 13 Jul 2018

Cited by 21 | Viewed by 4645

Abstract

Three series of layered double hydroxides (LDH) with a hydrotalcite-like structure and composition corresponding to [Mg₄Al₂(OH)₁₂(CO₃)]·3H₂O have been prepared from a common batch by applying three different aging procedures, namely, stirring at room [...] Read more.

Three series of layered double hydroxides (LDH) with a hydrotalcite-like structure and composition corresponding to [Mg₄Al₂(OH)₁₂(CO₃)]·3H₂O have been prepared from a common batch by applying three different aging procedures, namely, stirring at room temperature, hydrothermal treatment, and microwave-hydrothermal treatment. It has been found that the tested properties of the samples (mainly related to their crystallinity) are considerably improved by using the microwave-hydrothermal treatment. Shorter times are also evinced than in the other two aging treatments; however, if the microwave-hydrothermal treatment is too far extended, incipient destruction of the particles is observed. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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Review

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22 pages, 8293 KiB

Open AccessFeature PaperReview

Preparation of Layered Double Hydroxides toward Precisely Designed Hierarchical Organization

by Rattanawadee (Ploy) Wijitwongwan, Soontaree (Grace) Intasa-ard and Makoto Ogawa

ChemEngineering 2019, 3(3), 68; https://doi.org/10.3390/chemengineering3030068 - 1 Aug 2019

Cited by 65 | Viewed by 11635

Abstract

Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities for a wide range of materials’ applications including adsorbent, catalyst and its support, ceramic precursor, and drug carrier. In order to satisfy the requirements for [...] Read more.

Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities for a wide range of materials’ applications including adsorbent, catalyst and its support, ceramic precursor, and drug carrier. In order to satisfy the requirements for the detailed characterization and the practical application, the preparation of LDHs with varied composition and particle morphology has been examined extensively. The versatility of the preparation methods led LDHs with varied composition and micro/macroscopic morphology, which makes the application of LDHs more realistic. In the present review article, synthetic methods of LDHs are overviewed in order to highlight the present status of the LDHs for practical application. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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