Special Issue "Advanced Applications of Layered Double Hydroxides"

A special issue of ChemEngineering (ISSN 2305-7084).

Deadline for manuscript submissions: 31 October 2019.

Special Issue Editor

Prof. Dr. Vicente Rives
E-Mail Website
Guest Editor
GIR-QUESCAT, Department of Inorganic Chemistry, University of Salamanca, Salamanca, Spain
Interests: : heterogeneous catalysts; nanocomposites (e.g., flame retardants); soil water remediation; controlled release of drugs; adsorption of organics and of inorganics; mixed oxide precursos for ceramics

Special Issue Information

Dear Colleagues,

Layered double hydroxides have received outstanding attention from scientists and technologists in the last few decades because of their easy preparation, low price and versatile applications. These extend to a broad range, including heterogeneous catalysts, catalyst precursors, catalyst supports, anion scavenging, water remediation, controlled delivery of drugs and other chemicals, adsorption of organic and inorganic anions, nanocomposites (both as stabilizers or for flame retardant purposes as well), inorganic pigments precursors, as electrodes in electrochemistry, photochemical reactions in the interlayer, as antacids in medicine, stabilization of biomolecules, etc. Updating of these applications will be undoubtedly of interest for all scientists involved in the above-mentioned fields, and new applications, probably unforeseen in the last few years, will probably turn up.

Given your reputed experience in the study of layered double hydroxides and the outstanding impact of your previous publications in this field, we would very much appreciate your contribution in this field in this Special Issue of ChemEngineering. Although it is mainly focused on advanced applications, papers reviewing and updating already known applications, as well as novel synthetic routes, are also welcome.

Prof. Dr. Vicente Rives
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydrotalcite
  • layered double hydroxide
  • LDH
  • mixed oxides
  • basic catalysis
  • catalyst supports
  • nanocomposites
  • anion scavenging

Published Papers (10 papers)

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Research

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Open AccessArticle
High-Power Ultrasonic Synthesis and Magnetic-Field-Assisted Arrangement of Nanosized Crystallites of Cobalt-Containing Layered Double Hydroxides
ChemEngineering 2019, 3(3), 62; https://doi.org/10.3390/chemengineering3030062 - 04 Jul 2019
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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Open AccessFeature PaperArticle
Investigation of Thermal Behavior of Layered Double Hydroxides Intercalated with Carboxymethylcellulose Aiming Bio-Carbon Based Nanocomposites
ChemEngineering 2019, 3(2), 55; https://doi.org/10.3390/chemengineering3020055 - 01 Jun 2019
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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Open AccessArticle
Nanohybrid Layered Double Hydroxides Used to Remove Several Dyes from Water
ChemEngineering 2019, 3(2), 41; https://doi.org/10.3390/chemengineering3020041 - 19 Apr 2019
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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Open AccessArticle
The Formation of Layered Double Hydroxide Phases in the Coprecipitation Syntheses of [Ni0.80Co0.15](1−x)/0.95Alx(OH)2(anionn)x/n (x = 0–0.2, n = 1, 2)
ChemEngineering 2019, 3(2), 38; https://doi.org/10.3390/chemengineering3020038 - 09 Apr 2019
Abstract
This study investigates the synthesis of [Ni0.80Co0.15](1−x)/0.95Alx(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 [Ni0.80Co0.15](1−x)/0.95Alx(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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Open AccessArticle
Layered Double Hydroxides for the Catalytic Isomerization of Linoleic Acid to Conjugated Linoleic Acids (CLAs)
ChemEngineering 2019, 3(1), 30; https://doi.org/10.3390/chemengineering3010030 - 10 Mar 2019
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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Open AccessArticle
Synthesis of Chalcone Using LDH/Graphene Nanocatalysts of Different Compositions
ChemEngineering 2019, 3(1), 29; https://doi.org/10.3390/chemengineering3010029 - 09 Mar 2019
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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Open AccessArticle
Reactivity and Heavy Metal Removal Capacity of Calcium Alginate Beads Loaded with Ca–Al Layered Double Hydroxides
ChemEngineering 2019, 3(1), 22; https://doi.org/10.3390/chemengineering3010022 - 01 Mar 2019
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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Open AccessArticle
Layered Double Hydroxide Sorbents for Removal of Selenium from Power Plant Wastewaters
ChemEngineering 2019, 3(1), 20; https://doi.org/10.3390/chemengineering3010020 - 22 Feb 2019
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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Open AccessArticle
Controlling the Synthesis Conditions for Tuning the Properties of Hydrotalcite-Like Materials at the Nano Scale
ChemEngineering 2018, 2(3), 31; https://doi.org/10.3390/chemengineering2030031 - 13 Jul 2018
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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Open AccessFeature PaperReview
Preparation of Layered Double Hydroxides toward Precisely Designed Hierarchical Organization
ChemEngineering 2019, 3(3), 68; https://doi.org/10.3390/chemengineering3030068 - 01 Aug 2019
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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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Heavy metal removal by alginate beads loaded with Ca Al layered double
hydroxides

  Abstract: Ca-Al layered double hydroxides (Ca-Al-LDHs) present large heavy metal removal capacity, but their application restricted by its high reactivity and the difficult separation from the remediated media. Here
we propose the inclusion of these solids in calcium alginate (CaAlg) beads to improve their performance. Ca-Al LDHs prepared by coprecipitation at variable pH were included in alginate beads with a 0.05 Ca-Al LDH/CaAlg ratio were prepared. The acid base reactivity of the obtained beads was compared to that of pure CaAlg beads and the impact on the removal od Cu^2+ , used as a prove heavy metal ion, was assessed.

 Author: Ricardo Rojas y Delgado

2. Title: Morphosyntheses of layered double hydroxides

Abstract: Due to the wide range of application, the preparation of layered double hydroxides (LDHs) with varied composition and particle size have been reported extensively.  The synthetic method is based on the precipitation from solution.  While the dissolution and re-precipitation under hydrothermal condition is also regarded as a pathway to obtain LDHs.  In addition, solid-state reactions (mechanochemical reactions) have also been applied to prepare LDHs.  Applicable LDHs and their intercalates are limited for each synthetic method.  The available particle size and size distribution are dependent on the the synthetic means as well as the detailed conditions.

Post-synthetic hybridization of LDHs has also been done by means of the reactions in solution (at the solid-liquid interfaces) and in the solid-state.  LDHs containing a wide variety of guest anions have been obtained so far.

In the present review, the preparation of LDHs by several different synthetic methods will be summarized to discuss the possible correlation between the synthetic methods and the materials characteristics.

Author: Makoto OGAWA

3. Title: Layered double hydroxides for the catalytic isomerization of linoleic acid to conjugated linoleic acids (CLAs)

Abstract: The term conjugated linoleic acid (CLA) is used to designate the whole of dienoic conjugated isomers in position and geometry of linoleic acid (LA, cis-9, cis-12-octadecadienoic acid). Linoleic acid has double bonds located on carbons 9 and 12, both in the cis configuration whereas CLA has either the cis or trans configuration or both located along the carbon chain. Over years, some studies showed that a small number of unsaturated fatty acids present interesting biomedical and nutritional properties, thus demonstrating their potential application as functional foods. Specifically, the cis-9, trans-11-CLA isomer (c9, t11-CLA) has been proposed as a potential anti-tumour agent while the trans-10, cis-12-CLA isomer (t10, c12-CLA) affects the regulation of lipids (cholesterol) and body mass.

The aim of this work is to study the role of catalyst basicity on the isomerization of linoleic acid by testing several layered double hydroxides synthesized with different cations and different M2+/M3+ ratios.

Author: María Pilar Salagre Carnero

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