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Crystals
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Layered Double Hydroxides (LDHs)
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Layered Double Hydroxides (LDHs)

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 35559

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Roberto Pizzoferrato

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Guest Editor
Department of Industrial Engineering, Università degli Studi di Roma Tor Vergata, Rome, Italy
Interests: synthesis and characterization of functionalized nanomaterials; layered double hydroxides; carbon-based nanomaterials; optical properties of innovative materials; optical sensors for the detection of heavy metals; hybrid organic/inorganic materials for optical emitters; nonlinear optical materials
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Maria Richetta

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Rome Tor Vergata, 00133 Roma, Italy
Interests: design; additive manufacturing; metals; mechanical properties; characterization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The peculiar properties of layered double hydroxides (LDHs) have progressively drawn the attention of a large part of the scientific community. The main characteristics of LDHs are their ability to capture anionic species (both organic and inorganic) in interlamellar space, and the possibility of blending with other compounds to build up different composites. This is allowed by the sandwich structure of LDHs, similar to the brucite-like architecture, made up of positive charged lamellas interspersed by anions. The lamellas can be separated and recombined to form a variety of LDH-based materials.

In fact, despite their relatively long history, LDHs are still the subject of a significant number of studies regarding their morphology and properties, while several distant fields, ranging from medicine to physics and engineering, show interest in the practical applications of LDHs. To this end, energy was and is spent to sculpt LDHs’ physical and chemical properties, and to design “ad hoc” LDHs for different needs and employments.

We invite investigators to submit papers that discuss the recent developments and results about LDHs and LDH-based materials, with regard to their synthesis, growth mechanism, characterization and applications. In particular, the submission of any study on the possible applications of LDH-based nanomaterials is strongly encouraged. These include, but are not limited to the following: design of surfaces with super hydrophobic properties, anticorrosion coatings, flame-retardants, water waste treatments, biomedical applications, chemical or physical sensors, nanostructured-modified textiles, energy harvesting, conversion, and storage.

The potential topics include, but, again, are not limited to, the following:

  • LDH growth and film deposition by any method (co-precipitation, in situ, electrochemical, etc.)
  • Structure and property characterization (XRD, TEM, SEM, dielectric, piezoelectric, electrical conductivity, EIS, ferroelectric, pyroelectric properties, etc.)
  • Inorganic containers and nanocontainers (drug delivery, UV stabilizer, etc.)
  • Anticorrosion coatings
  • Composite materials and nanomaterials
  • Biocompatibility
  • Antibacterial and osteogenic coatings
  • Advanced electrodes for supercapacitors, water splitting, and so on
  • Photocatalysis and light-induced CO2 reduction
  • Oxygen evolution reduction electrocatalysis
  • Delamination
  • Wastewater remediation
  • Dye removal and heavy-metal filtration

Prof. Dr. Roberto Pizzoferrato
Prof. Dr. Maria Richetta
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

  • layered double hydroxides
  • LDH growth methods
  • microstructure–property relationship
  • functional coatings
  • anticorrosion
  • bioapplications
  • advaced electrodes
  • water splitting
  • carbon dioxide reduction
  • contaminant removal
  • alumina refinement

Published Papers (9 papers)

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Editorial

Jump to: Research, Review

4 pages, 169 KiB  
Editorial
Layered Double Hydroxides (LDHs)
by Roberto Pizzoferrato and Maria Richetta
Crystals 2020, 10(12), 1121; https://doi.org/10.3390/cryst10121121 - 09 Dec 2020
Cited by 8 | Viewed by 2160
Abstract
n/a Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))

Research

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16 pages, 3894 KiB  
Article
Exploring the Wet Mechanochemical Synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al Layered Double Hydroxides from Oxides, Hydroxides and Basic Carbonates
by Brenda Antoinette Barnard and Frederick Johannes Willem Jacobus Labuschagné
Crystals 2020, 10(10), 954; https://doi.org/10.3390/cryst10100954 - 20 Oct 2020
Cited by 10 | Viewed by 3233
Abstract
The synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al layered double hydroxides (LDHs) was investigated with a one-step wet mechanochemical route. The research aims to expand on the mechanochemical synthesis of LDH using a mill designed for wet grinding application. A 10% slurry of [...] Read more.
The synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al layered double hydroxides (LDHs) was investigated with a one-step wet mechanochemical route. The research aims to expand on the mechanochemical synthesis of LDH using a mill designed for wet grinding application. A 10% slurry of solids was added to a Netzsch LME 1 horizontal bead mill and milled for 1 h at 2000 rpm. Milling conditions were selected according to machine limitations and as an initial exploratory starting point. Precursor materials selected consisted of a mixture of oxides, hydroxides and basic carbonates. Samples obtained were divided such that half was filtered and dried at 60 °C for 12 h. The remaining half of the samples were further subjected to ageing at 80 °C for 24 h as a possible second step to the synthesis procedure. Synthesis conditions, such as selected precursor materials and the MII:MIII ratio, were adapted from existing mechanochemical methods. LDH synthesis prior to ageing was successful with precursor materials observably present within each sample. No Cu-Al LDH was clearly identifiable. Ageing of samples resulted in an increase in the conversion of raw materials to LDH product. The research offers a promising ‘green’ method for LDH synthesis without the production of environmentally harmful salt effluent. The synthesis technique warrants further exploration with potential for future commercial up-scaling. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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13 pages, 2803 KiB  
Article
Microwave-Assisted Aldol Condensation of Furfural and Acetone over Mg–Al Hydrotalcite-Based Catalysts
by Alberto Tampieri, Matea Lilic, Magda Constantí and Francesc Medina
Crystals 2020, 10(9), 833; https://doi.org/10.3390/cryst10090833 - 18 Sep 2020
Cited by 13 | Viewed by 3630
Abstract
The depletion of fossil fuel resources has prompted the scientific community to find renewable alternatives for the production of energy and chemicals. The products of the aldol condensation between bio-based furfural and acetone have been individuated as promising intermediates for the preparation of [...] Read more.
The depletion of fossil fuel resources has prompted the scientific community to find renewable alternatives for the production of energy and chemicals. The products of the aldol condensation between bio-based furfural and acetone have been individuated as promising intermediates for the preparation of biofuels and polymeric materials. We developed a protocol for the microwave-assisted condensation of these two compounds over hydrotalcite-based materials. Mg:Al 2:1 hydrotalcite was prepared by co-precipitation; the obtained solid was calcined to afford the corresponding mixed metal oxide, which was then rehydrated to obtain a meixnerite-type material. The prepared solids were characterized by PXRD, ICP-AES, TGA-DSC and N2 physisorption, and tested as catalysts in the aldol condensation of acetone and furfural in a microwave reactor. The performance of the catalysts was assessed and compared; the meixnerite catalyst proved to be the most active, followed by the mixed metal oxide and the as-synthesized hydrotalcite, which has often been reported to be inactive. In all cases, the reaction is quite fast and selective, which makes our protocol useful for rapidly converting furfural and acetone into their condensation products. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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26 pages, 28561 KiB  
Article
Green Synthesis of Hydrocalumite (CaAl-OH-LDH) from Ca(OH)2 and Al(OH)3 and the Parameters That Influence Its Formation and Speciation
by Bianca R. Gevers and Frederick J.W.J. Labuschagné
Crystals 2020, 10(8), 672; https://doi.org/10.3390/cryst10080672 - 03 Aug 2020
Cited by 25 | Viewed by 4473
Abstract
Hydrocalumite is a layered double hydroxide (LDH) that is finding increased application in numerous scientific fields. Typically, this material is produced through environmentally polluting methods such as co-precipitation, sol-gel synthesis and urea-hydrolysis. Here, the hydrothermal green (environmentally friendly) synthesis of hydrocalumite (CaAl-OH) from [...] Read more.
Hydrocalumite is a layered double hydroxide (LDH) that is finding increased application in numerous scientific fields. Typically, this material is produced through environmentally polluting methods such as co-precipitation, sol-gel synthesis and urea-hydrolysis. Here, the hydrothermal green (environmentally friendly) synthesis of hydrocalumite (CaAl-OH) from Ca(OH)2 and Al(OH)3 in water and the parameters that influence its formation are discussed. The parameters investigated include the reaction temperature, reaction time, molar calcium-to-aluminium ratio, the morphology/crystallinity of reactants used, mixing and the water-to-solids ratio. Hydrocalumite formation was favoured in all experiments, making up between approximately 50% and 85% of the final crystalline phases obtained. Factors that were found to encourage higher hydrocalumite purity include a low water-to-solids ratio, an increase in the reaction time, sufficient mixing, the use of amorphous Al(OH)3 with a high surface area, reaction at an adequate temperature and, most surprisingly, the use of a calcium-to-aluminium ratio that stoichiometrically favours katoite formation. X-ray diffraction (XRD) and Rietveld refinement were used to determine the composition and crystal structures of the materials formed. Scanning electron microscopy (SEM) was used to determine morphological differences and Fourier-transform infrared analysis with attenuated total reflectance (FTIR-ATR) was used to identify possible carbonate contamination, inter alia. While the synthesis was conducted in an inert environment, some carbonate contamination could not be avoided. A thorough discussion on the topic of carbonate contamination in the hydrothermal synthesis of hydrocalumite was given, and the route to improved conversion as well as the possible reaction pathway were discussed. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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19 pages, 9970 KiB  
Article
On the Reconstruction Peculiarities of Sol–Gel Derived Mg2−xMx/Al1 (M = Ca, Sr, Ba) Layered Double Hydroxides
by Ligita Valeikiene, Marina Roshchina, Inga Grigoraviciute-Puroniene, Vladimir Prozorovich, Aleksej Zarkov, Andrei Ivanets and Aivaras Kareiva
Crystals 2020, 10(6), 470; https://doi.org/10.3390/cryst10060470 - 02 Jun 2020
Cited by 16 | Viewed by 2588
Abstract
In this study, the reconstruction peculiarities of sol–gel derived Mg2−xMx/Al1 (M = Ca, Sr, Ba) layered double hydroxides were investigated. The mixed metal oxides (MMO) were synthesized by two different routes. Firstly, the MMO were obtained directly by [...] Read more.
In this study, the reconstruction peculiarities of sol–gel derived Mg2−xMx/Al1 (M = Ca, Sr, Ba) layered double hydroxides were investigated. The mixed metal oxides (MMO) were synthesized by two different routes. Firstly, the MMO were obtained directly by heating Mg(M)–Al–O precursor gels at 650 °C, 800 °C, and 950 °C. These MMO were reconstructed to the Mg2−xMx/Al1 (M = Ca, Sr, Ba) layered double hydroxides (LDHs) in water at 50 °C for 6 h (pH 10). Secondly, in this study, the MMO were also obtained by heating reconstructed LDHs at the same temperatures. The synthesized materials were characterized using X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM). Nitrogen adsorption by the Brunauer, Emmett, and Teller (BET) and Barrett, Joyner, and Halenda (BJH) methods were used to determine the surface area and pore diameter of differently synthesized alkaline earth metal substituted MMO compounds. It was demonstrated for the first time that the microstructure of reconstructed MMO from sol–gel derived LDHs showed a “memory effect”. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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9 pages, 5052 KiB  
Article
Layered Double Hydroxides for Remediation of Industrial Wastewater from a Galvanic Plant
by Anna Maria Cardinale, Cristina Carbone, Sirio Consani, Marco Fortunato and Nadia Parodi
Crystals 2020, 10(6), 443; https://doi.org/10.3390/cryst10060443 - 30 May 2020
Cited by 24 | Viewed by 2863
Abstract
Owing to their structure, layered double hydroxides (LDHs) are nowadays considered as rising materials in different fields of application. In this work, the results obtained in the usage of two different LDHs to remove, by adsorption, some cationic and anionic pollutants from industrial [...] Read more.
Owing to their structure, layered double hydroxides (LDHs) are nowadays considered as rising materials in different fields of application. In this work, the results obtained in the usage of two different LDHs to remove, by adsorption, some cationic and anionic pollutants from industrial wastewater are reported. The two compounds MgAl-CO3 and NiAl-NO3 have been prepared through a hydrothermal synthesis process and then characterized by means of PXRD, TGA, FESEM, and FTIR spectroscopy. The available wastewater, supplied by a galvanic treatment company, has been analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES), resulting as being polluted by Fe(III), Cu(II), and Cr(VI). The water treatment with the two LDHs showed that chromate is more efficiently removed by the NiAl LDH through an exchange with the interlayer nitrate. On the contrary, copper and iron cations are removed in higher amounts by the MgAl LDH, probably through a substitution with Mg, even if sorption on the OH− functional groups, surface complexation, and/or precipitation of small amounts of metal hydroxides on the surface of the MgAl LDH could not be completely excluded. Possible applications of the two combined LDHs are also proposed. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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17 pages, 3428 KiB  
Article
Curcumin Incorporation into Zn3Al Layered Double Hydroxides—Preparation, Characterization and Curcumin Release
by Octavian D. Pavel, Ariana Şerban, Rodica Zăvoianu, Elena Bacalum and Ruxandra Bîrjega
Crystals 2020, 10(4), 244; https://doi.org/10.3390/cryst10040244 - 26 Mar 2020
Cited by 9 | Viewed by 3526
Abstract
Curcumin (CR) is a natural antioxidant compound extracted from Curcuma longa (turmeric). Until now, researches related to the incorporation of CR into layered double hydroxides (LDHs) were focused only on hybrid structures based on a MgxAl-LDH matrix. Our studies were extended towards the [...] Read more.
Curcumin (CR) is a natural antioxidant compound extracted from Curcuma longa (turmeric). Until now, researches related to the incorporation of CR into layered double hydroxides (LDHs) were focused only on hybrid structures based on a MgxAl-LDH matrix. Our studies were extended towards the incorporation of CR in another type of LDH-matrix (Zn3Al-LDH) which could have an even more prolific effect on the antioxidant activity due to the presence of Zn. Four CR-modified Zn3Al-LDH solids were synthesized, e.g., PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) and RZn3Al-CR(Et) (molar ratio CR/Al = 1/10, where P and R stand for the preparation method (P = precipitation, R = reconstruction), while (Aq) and (Et) indicate the type of CR solution, aqueous or ethanolic, respectively). The samples were characterized by XRD, Attenuated Total Reflectance Fourier Transformed IR (ATR-FTIR) and diffuse reflectance (DR)-UV–Vis techniques and the CR-release was investigated in buffer solutions at different pH values (1, 2, 5, 7 and 8). XRD results indicated a layered structure for PZn3Al-CR(Aq), PZn3Al-CR(Et), RZn3Al-CR(Aq) impurified with ZnO, while RZn3Al-CR(Et) contained ZnO nano-particles as the main crystalline phase. For all samples, CR-release revealed a decreasing tendency towards the pH increase, and higher values were obtained for RZn3Al-CR(Et) and PZn3Al-CR(Et) (e.g., 45% and 25%, respectively at pH 1). Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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Review

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39 pages, 7408 KiB  
Review
Effect of LDHs and Other Clays on Polymer Composite in Adsorptive Removal of Contaminants: A Review
by Maleshoane Mohapi, Jeremia Shale Sefadi, Mokgaotsa Jonas Mochane, Sifiso Innocent Magagula and Kgomotso Lebelo
Crystals 2020, 10(11), 957; https://doi.org/10.3390/cryst10110957 - 22 Oct 2020
Cited by 32 | Viewed by 4693
Abstract
Recently, the development of a unique class of layered silicate nanomaterials has attracted considerable interest for treatment of wastewater. Clean water is an essential commodity for healthier life, agriculture and a safe environment at large. Layered double hydroxides (LDHs) and other clay hybrids [...] Read more.
Recently, the development of a unique class of layered silicate nanomaterials has attracted considerable interest for treatment of wastewater. Clean water is an essential commodity for healthier life, agriculture and a safe environment at large. Layered double hydroxides (LDHs) and other clay hybrids are emerging as potential nanostructured adsorbents for water purification. These LDH hybrids are referred to as hydrotalcite-based materials or anionic clays and promising multifunctional two-dimensional (2D) nanomaterials. They are used in many applications including photocatalysis, energy storage, nanocomposites, adsorption, diffusion and water purification. The adsorption and diffusion capacities of various toxic contaminants heavy metal ions and dyes on different unmodified and modified LDH-samples are discussed comparatively with other types of nanoclays acting as adsorbents. This review focuses on the preparation methods, comparison of adsorption and diffusion capacities of LDH-hybrids and other nanoclay materials for the treatment of various contaminants such as heavy metal ions and dyes. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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26 pages, 4086 KiB  
Review
Morphology, Thermal Stability, and Flammability Properties of Polymer-Layered Double Hydroxide (LDH) Nanocomposites: A Review
by Mokgaotsa Jonas Mochane, Sifiso Innocent Magagula, Jeremia Shale Sefadi, Emmanuel Rotimi Sadiku and Teboho Clement Mokhena
Crystals 2020, 10(7), 612; https://doi.org/10.3390/cryst10070612 - 14 Jul 2020
Cited by 61 | Viewed by 7144
Abstract
The utilization of layered nanofillers in polymer matrix, as reinforcement, has attracted great interest in the 21st century. This can be attributed to the high aspect ratios of the nanofillers and the attendant substantial improvement in different properties (i.e., increased flammability resistance, improved [...] Read more.
The utilization of layered nanofillers in polymer matrix, as reinforcement, has attracted great interest in the 21st century. This can be attributed to the high aspect ratios of the nanofillers and the attendant substantial improvement in different properties (i.e., increased flammability resistance, improved modulus and impact strength, as well as improved barrier properties) of the resultant nanocomposite when compared to the neat polymer matrix. Amongst the well-known layered nanofillers, layered inorganic materials, in the form of LDHs, have been given the most attention. LDH nanofillers have been employed in different polymers due to their flexibility in chemical composition as well as an adjustable charge density, which permits numerous interactions with the host polymer matrices. One of the most important features of LDHs is their ability to act as flame-retardant materials because of their endothermic decomposition. This review paper gives detailed information on the: preparation methods, morphology, flammability, and barrier properties as well as thermal stability of LDH/polymer nanocomposites. Full article
(This article belongs to the Special Issue Layered Double Hydroxides (LDHs))
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