MgAl-layered Double Hydroxide Research Articles

Robust, sustainable cellulose composite aerogels with outstanding flame retardancy and thermal insulation

Robust and sustainable cellulose composite aerogels were prepared by incorporating MgAl-layered double hydroxide (MgAl-LDH) as green nanofillers and flame retardants. Two series of aerogels combining MgAl-CO3 LDH (MA-C) and MgAl-H2PO4 LDH (MA-P) were achieved, in which both MA-C and MA-P were uniformly dispersed in cellulose substances. The cellulose composite aerogels with 1.8 wt% of MA-C (denoted as CAC) and MA-P (denoted as CAP) displayed excellent mechanical properties, increased by 2.6 and 2.8 times compared with neat cellulose aerogels (CA), respectively. The peak of heat release rate (PHRR) of CAC and CAP reduced by 41 % and 50 % compared with the neat one, respectively, demonstrating the outstanding flame retardancy. The reduction in smoke production ratio (SPR) was 79 % for CAC and 75 % for CAP, respectively, indicating enhanced smoke suppression performance. Therefore, the high performance flame-retardant cellulose composite aerogels exhibit an application prospect in green advanced engineering field.

Fe/Co-chalcogenide-stabilized Fe3O4 nanoparticles supported MgAl-layered double hydroxide as a new magnetically separable sorbent for the simultaneous spectrophotometric determination of anionic dyes

Magnesium-aluminum layered double hydroxide (MgAl-LDH) supported on Fe3O4–SiO2 which stabilized and modified by CoS-FeS chalcogenide was prepared and characterized by FT-IR, XRD, FE-SEM, EDS and, VSM analysis. Subsequently, this prepared material was applied in a dispersive solid-phase extraction (DSPE) system for simultaneous preconcentration and determination of trace levels of disulfine blue (DSB) and bromocresol green (BCG) anionic dyes from aqueous solutions which method was followed by UV–vis spectrophotometry detection. Central composite design (CCD) was applied to optimize the contribution of operational parameters including pH, sorbent dosage, sonication extraction time, type, volume and eluent concentration on system performance. Under optimized conditions, detection and quantification limits were obtained to be 0.033 mg L−1 and 0.109 mg L−1 for DSB and 0.037 and 0.123 mg L−1 for BCG, respectively, as well as, good linearity was obtained. This novel and interesting extraction approach seem to be fast and efficient procedure for the extraction of anionic dyes from aqueous samples. The kinetics and the adsorption isotherms of dyes reveal their rapid adsorption, following a with a pseudo-first-order kinetics and Freundlich adsorption isotherm model.

Sol-Gel Synthesis and Characterization of Coatings of Mg-Al Layered Double Hydroxides.

In this study, new synthetic approaches for the preparation of thin films of Mg-Al layered double hydroxides (LDHs) have been developed. The LDHs were fabricated by reconstruction of mixed-metal oxides (MMOs) in deionized water. The MMOs were obtained by calcination of the precursor gels. Thin films of sol–gel-derived Mg-Al LDHs were deposited on silicon and stainless-steel substrates using the dip-coating technique by a single dipping process, and the deposited film was dried before the new layer was added. Each layer in the preparation of the Mg-Al LDH multilayers was separately annealed at 70 °C or 300 °C in air. Fabricated Mg-Al LDH coatings were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was discovered that the diffraction lines of Mg3Al LDH thin films are sharper and more intensive in the sample obtained on the silicon substrate, confirming a higher crystallinity of synthesized Mg3Al LDH. However, in both cases the single-phase crystalline Mg-Al LDHs have formed. To enhance the sol–gel processing, the viscosity of the precursor gel was increased by adding polyvinyl alcohol (PVA) solution. The LDH coatings could be used to protect different substrates from corrosion, as catalyst supports, and as drug-delivery systems in medicine.

MgAl-layered double hydroxide flower arrays grown on carbon paper for efficient electrochemical sensing of nitrite

In this work, MgAl-layered double hydroxide nanosheets arrays in-situ grown on commercial carbon paper (MA-LDH/CP) have been successfully fabricated via a facile one-pot hydrothermal method, which shows a hierarchical flower-like structure. The as-prepared MA-LDH/CP is used as a free-standing electrode for electrochemical detection of nitrite in aqueous media, showing high sensitivity with a low detection limit of 0.03 μM, and good anti-interference to other species. Moreover, it exhibits outstanding electrochemical stability without any deactivation in almost two months. The superior performance of MA-LDH/CP for nitrite determination is attributed to the 3D hierarchical architecture of MA-LDH nanolayers and a large number of exposed surface sites, which facilitate the electron transfer and nitrite adsorption.

High-performance asymmetric supercapacitor based on 1T-MoS2 and MgAl-Layered double hydroxides

In this work, carbon fiber clothes (CFC) supported 1T phase MoS2 anode material is synthesized through a one-pot hydrothermal method. The CFC-MoS2 composites has high specific capacitance of 1485.08 F g−1 at the current density of 2 A g−1, and the 54% of initial capacitance can be remained at the current density reached to 15 A g−1. The 87.5% of initial capacitance can be harvested even at the ceaseless cycled for 10,000 cycles at 4 A g−1. In addition, the MgAl layered double hydroxides and graphene oxide (MgAl-LDH-GO) cathode composite material is synthesized. The MgAl-LDH-GO cathode exhibits high specific capacitance (1208.50 F g−1 at 1 A g−1) and long cycle life (76.9% retention during 10,000 cycles). Finally, we successfully assemble the CFC-MoS2//MgAl-LDH-GO asymmetric supercapacitor. It has high energy density of 326.54 Wh kg−1 at power density of 1500 W kg−1, and the energy density can be remained at 279.56 Wh kg−1 even the power density reach to 12 kW kg−1. This excellent performance satisfied the current demand of the high power and energy density. Thus, the lightweight (<0.25 mg/cm2), ultrathin (<0.8 mm), and the favourable electrochemical performance make it suitable for the next generation energy storage device.

Adsorption performance and mechanistic study of heavy metals by facile synthesized magnetic layered double oxide/carbon composite from spent adsorbent

To reuse the spent magnetic MgAl-layered double hydroxide after humic acid adsorption, this work provided a simple calcination method to prepare the magnetic layered double oxide/carbon (Mag-LDO/C) nanocomposite. The characterization results indicated the Mag-LDO/C was a carbonaceous composite with a large number of functional groups and superparamagnetic property. Then the adsorption performance of Mag-LDO/C for heavy metals was studied by batch experiments. The Mag-LDO/C exhibited excellent removal efficiencies for Cd(II), Pb(II), and Cu(II) with maximum adsorption capacities of 386.1, 359.7, and 192.7 mg/g, respectively. The batch sorption data were studied by the pseudo-second-order kinetic equation and the Langmuir isothermal model, and they matched well. According to the zeta potentials, X-ray diffraction patterns, and X-ray photoelectron spectra of Mag-LDO/C after heavy metals adsorption, the interaction mechanisms were ascribed to the precipitation, surface complexation, and electrostatic attraction. After reaction, the solid-liquid separation of Mag-LDO/C could quickly achieve using a magnet. Additionally, the Mag-LDH/C exhibited excellent adsorption capacities in various simulated wastewater and well sorption recyclability, proving the valuable applications of Mag-LDO/C synthesized from spent adsorbent for metal ions removal in actual water environment.

Efficient antimicrobial properties of layered double hydroxide assembled with transition metals via a facile preparation method

Mg2+ in MgAl-layered double hydroxides nanoparticles was substituted with different divalent transition metal ions (MAl-LDHs, M: Mg2+, Cu2+, Ni2+, Co2+, and Mn2+) via a facile method to be used as antibacterial agents. The phase structural and morphological characterizations of MAl-LDHs were investigated by XRD, FTIR spectroscopy and TEM. The results have shown that all of MAl-LDHs had typical layered structures except MnAl-LDH which contained Mn3O4 phases. Particular morphology of MnAl-LDH with ellipsoids, spherical and rod-like structure and CuAl-LDH with rod-like shape existed. IC50 (the concentrations providing 50% antibacterial activity) values of CuAl-LDH, NiAl-LDH, CoAl-LDH, and MnAl-LDH in broth dilution tests were ∼800-1500 μg/mL. Dosages of CuAl-LDH, CoAl-LDH, and MnAl-LDH with >10 mm inhibition zone in disk diffusion tests were ∼150–300 μg/disk. Antibacterial mechanism of MAl-LDHs may be attributed to the synergistic factors including effected surroundings, surface interactions, morphology of particles, ROS and metal ions. The results indicate a facile method to synthesis LDHs based effective antibacterial agents with the potential application in the area of water treatment and antibacterial coating.

Corrosion protection of steel by Mg-Al layered double hydroxides in simulated concrete pore solution: Effect of SO42-

This paper aims to evaluate the effect of SO42− ions on the corrosion protection of steel by Mg-Al layered double hydroxides (LDHs), which was synthesized by traditional co-deposition method. The results show that the presence of SO42− ions greatly affects the uptake amount of Cl- ions. The prepared Mg-Al LDHs has an obvious corrosion inhibition effect on steel. With the increase of SO42− content, the steel corrosion is initially decreased and then increased. The microstructure characterization demonstrates the uptake of Cl- and SO42− on Mg-Al LDHs, which mainly contribute to the corrosion inhibition of LDHs.

Synthesis of a novel dual layered double hydroxide hybrid nanomaterial and its application in epoxy nanocomposites

Ease of undesirable agglomeration and low efficiency are two problems that highly restrict the application of MgAl-layered double hydroxides (MgAl-LDH) as suitable flame retardants for epoxy resins. Herein, a new strategy that chose MOFs as the precursor to connect two different LDHs into a hybrid nanomaterial is reported. Nanosheets of NiCo-layered double hydroxides (NiCo-LDH) with multidimensional nanostructures were uniformly anchored on the surface of MgAl-LDH slabs. This led to a better dispersion and stronger interaction within the epoxy matrix, resulting in enhanced strength of the char layers, and also enabled synergistic flame retardant effect to the epoxy nanocomposite, when compared to the case of the unmodified epoxy. The sample passed V-0 rating in UL-94 test and its peak of heat release rate was reduced by 66.7% in cone calorimeter test with the addition of only 2.5 wt% of as-prepared flame retardant. Besides, due to the unique structure of the nanofiller, the mechanical properties of the nanocomposite were only slightly impacted. This is the first report on the synthesis of a dual LDH hybrid nanomaterial, which moreover, improved the flame retardancy of epoxy nanocomposite even when added in relatively low amounts.

Phosphorus recycling from urine using layered double hydroxides: A kinetic study

Layered double hydroxides (LDH) are anionic clay minerals that have the potential to recycle phosphate (P) from urine and may yield efficient P fertilisers. The efficient P recovery requires P uptake to be relatively fast, ensuring small adsorption columns to reduce process costs. This study assesses the kinetics of P adsorption and desorption of three phase-pure MgAl LDH with varying Al content and a phase-pure ZnAl LDH, all prepared by coprecipitation. The adsorption kinetics (0–24 h) in agitated suspension showed that 90% of the capacity is reached within 5 h, with similar rate constants for model solution as for synthetic urine. The LDH with low Al content maintain structural properties during adsorption, while crystallinity reduces for LDH with high Al content. The combination of XRD analysis, speciation modelling and kinetic information suggest that P uptake by LDH includes a fast step of ligand exchange, followed by slower step of anion exchange in the interlayer. The latter process dominates in LDH with high Al content whereas the former dominates the LDH with low Al content. The XRD analysis and speciation modelling furthermore suggests precipitation as an additional P removal mechanism. The P desorption (0–2 weeks) showed that >95% of P could be desorbed from MgAl-LDH whereas only 51% of adsorbed P is desorbed from the ZnAl LDH. Continuous flow pilot-scale adsorption columns with pelletized MgAl LDH granules (1 mm diameter) recovered >70% of urine-P at residence times of only 1 min, up to point of 70% of exchange capacity beyond which the recovery decreased. These results show that the LDH technology for P recovery is efficient to recycle P into high potential fertilisers.

In-situ growth of layered double hydroxide films on biomedical magnesium alloy by transforming metal oxyhydroxide

Layered double hydroxide (LDH) films have been widely used for corrosion protection and medical applications. The most common synthesis methods for in-situ growth of LDH films on magnesium (Mg) alloys are hydrothermal treatment and steam coating. However, both the methods are mainly used for preparing MgAl LDH films and have limitations to in-situ fabricate other Mg-based LDH films which are suitable for biomedical application. Herein, a novel synthesis strategy for in-situ growth of LDH films on Mg alloys is proposed. Firstly, amorphous ferric oxyhydroxide (FeOOH) film was developed on Mg-Nd-Zn-Zr (JDBM) alloy by electrodeposition technique. Then, the as-prepared FeOOH films were transformed into MgFe LDH film via hydrothermal treatment in water. In the LDH formation process, Mg2+ would enter into amorphous FeOOH and replace the Fe3+ quickly to form LDH. The thickness of the LDH films can be easily controlled by adjusting electrodeposition time. Electrochemical tests and cells culture experiments indicated that the as-prepared MgFe LDH films improved corrosion resistance and biocompatibility of JDBM alloy. In addition, MgMn LDH can also be prepared from amorphous manganese oxyhydroxide (MnOOH) via this newly developed two-step method. The present work provides a new strategy for preparation of LDH films on Mg alloys surface.

Simultaneous Removal of Phosphate and Nitrate on Calcined Mg-Al Layered Double Hydroxides

Simultaneous Removal of Phosphate and Nitrate on Calcined Mg-Al Layered Double Hydroxides

Preparation and Characterization of Mg/Al/Fe Hydrotalcite with Superb Absorption Capacity toward Congo Red

Mg/Al/Fe layered double hydroxide (MAF-LDH1) was prepared by solvothermal method with the sodium dodecyl sulfate as the template, and the ethanol system was benefit to growth of sample. The nature in the resulting MAF-LDH was investigated by X-ray diffraction, field emission scanning electron microscopy, Fourier transformed infrared spectra, thermogravimetric analysis, and N2 adsorption-desorption. The morphology of MAF-LDH1 is petal-like with the size of 400–500 nm and the thickness about 10–20 nm. The adsorption performance of the samples was evaluated by absorption of the Congo red (CR) solutions. Compared with Mg/Al layered double hydroxide (MA-LDH), the maximum adsorption capacities of the MAF-LDH1 samples were 943.4 mg/g which was greatly enhanced. Furthermore, after seven cycling tests, the adsorption performance was still up to 90%. Theoretical calculation results revealed that the adsorption process was spontaneous and followed the pseudo-second-order kinetic model and Freundlich model. This work provides a promising alternative strategy to enhance the adsorptive properties of hydrotalcite-like materials.

The Impact of Magnesium-Aluminum-Layered Double Hydroxide-Based Polyvinyl Alcohol Coated on Magnetite on the Preparation of Core-Shell Nanoparticles as a Drug Delivery Agent.

One of the current developments in drug research is the controlled release formulation of drugs, which can be released in a controlled manner at a specific target in the body. Due to the diverse physical and chemical properties of various drugs, a smart drug delivery system is highly sought after. The present study aimed to develop a novel drug delivery system using magnetite nanoparticles as the core and coated with polyvinyl alcohol (PVA), a drug 5-fluorouracil (5FU) and Mg–Al-layered double hydroxide (MLDH) for the formation of FPVA-FU-MLDH nanoparticles. The existence of the coated nanoparticles was supported by various physico-chemical analyses. In addition, the drug content, kinetics, and mechanism of drug release also were studied. 5-fluorouracil (5FU) was found to be released in a controlled manner from the nanoparticles at pH = 4.8 (representing the cancerous cellular environment) and pH = 7.4 (representing the blood environment), governed by pseudo-second-order kinetics. The cytotoxicity study revealed that the anticancer delivery system of FPVA-FU-MLDH nanoparticles showed much better anticancer activity than the free drug, 5FU, against liver cancer and HepG2 cells, and at the same time, it was found to be less toxic to the normal fibroblast 3T3 cells.

In Situ Nanoassembly of Mg-Al Layered Double Hydroxide on Polyester Fabric Surface: Mechanism, Tunable Wettability, and Boosted Thermal Features

In this study, nanosheets of Mg-Al layered double hydroxide (LDH) were introduced on the polyester fabric surface through the conventional coprecipitation method with further hydrothermal treatment at various temperatures (80, 100, and 120 °C). The in situ growth mechanism of Mg-Al LDHs in the vertical direction in an alkaline synthesis bath along with polyester fabric hydrolysis was discussed. Different analyses including X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric (TG) analysis, UV–visible, and Fourier transform infrared (FTIR) spectroscopy were utilized to characterize the synthesized nanosheets. Furthermore, vertical wicking, static contact angle, tensile strength, air permeability, bending, and burning length of fabric samples were investigated. The results showed successful synthesis of Mg-Al LDH nanosheets on the fabric surface with tunable wettability and boosted thermal features. Interestingly, there is no adverse effect on the ph...

Mg-Al layered double hydroxide as an electrolyte membrane for aqueous ammonia fuel cell

Mg-Al layered double hydroxide (LDH) intercalated with CO32−, an anionic clay mineral, is applied for aqueous ammonia fuel cells as an electrolyte. PtRu/C and Pt/C are used for the anode and the cathode catalysts, respectively. Pelletized Mg-Al LDH powder is used as an electrolyte. The fuel cell works from room temperature to 80 °C with 50% of relative humidity of the air, and the power density increases with an increase in the cell temperature. This indicates that Mg-Al LDH allows the fuel cell working at rather high temperatures compared with cell using typical organic polymer anion exchange membranes.

Corrosion resistance of a self-healing rose-like MgAl-LDH coating intercalated with aspartic acid on AZ31 Mg alloy

Intercalating corrosion inhibitor into protective coating with lamellar structure is an effective approach to get high corrosion resistance or a self-healing protection for metallic substrates. In present work, aspartic acid (ASP), an environmental friendly corrosion inhibitor was explored to insert into the MgAl-layered double hydroxides (MgAl-LDHs) on AZ31 magnesium alloys by a simple one-step hydrothermal method. The effect of growth time on the structure, morphology, composition and corrosion resistance of MgAl-ASP-LDHs and the self-healing ability of the scratched MgAl-ASP-LDHs samples were systemically investigated. Owing to the corrosion inhibition of ASP ions and their larger specific surface area to entrap aggressive anionic species such as Cl−, the MgAl-ASP-LDHs were found to have better corrosion resistance than MgAl-NO3−-LDHs. Resulting from the largest ratio of pore coverage and the three-dimensional rose flaky nanostructure, the MgAl-ASP-LDHs hydrothermally grown for 12 h has the best corrosion resistance. Due to the synergistic effect between ASP and laminate structure of LDHs, the MgAl-ASP-LDH coatings exhibit a good self-healing ability.

Development the sorption behavior of nanocomposite Mg/Al LDH by chelating with different monomers

Methacrylic acid, acetonitrile, dimethylsulfoxide and 1,4 dioxane intercalated Mg–Al layered double hydroxide (LDH) was made by the use of coprecipitation and the chelation techniques. The elimination of strontium, nitrate, and borate in polluted solution was scrutinized. The adsorption of Sr2+, NO3−, and B4O72− on methacrylate intercalated Mg–Al LDH (methacrylic acid (MAA)-Mg-Al LDH) proved that the adsorption process was spontaneous and increased randomness in the system. The equipped LDHs were performed by HNMR, scanning electron microscopy (SEM), thermogravemitric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS). It was established that different monomer types could intercalate inside an interlayer of the Mg–Al LDH. Methacrylic acid-intercalated Mg–Al LDH can effectively adsorb strontium, nitrate, and borate in aqueous solutions more effectively than other prepared LDHs. The dependability of the (MAA)-Mg-Al LDH was premeditated by iterating consecutive adsorption/desorption cycle.

HALS intercalated layered double hydroxides as an efficient light stabilizer for polypropylene

The thermal stability and migration resistance of light stabilizers are vital for their applications in plastics. Herein, a novel nano organic–inorganic hybrid light stabilizer with high thermal stability and low solubility was prepared by intercalating a synthesized hindered amine light stabilizer (HALS) with UV absorption capability into the interlayer galleries of MgAl layered double hydroxides (LDH) through co-precipitation method. The prepared HALS–LDH was characterized by XRD, FT–IR, SEM, TG–DTA and UV–vis, and was incorporated into the matrix of polypropylene (PP) via solvent casting method to prepare LDH/PP composite for light stability test. It was found that the synthesized HALS was successfully intercalated into the interlayer galleries of MgAl–LDH, forming an organic–inorganic hybrid material HALS–LDH with a mean size of 63 nm. HALS–LDH nanosheets were evenly dispersed in the matrix of PP, and the addition of HALS–LDH can retard the thermal decomposition of PP. Moreover, the incorporation of HALS–LDH significantly improved the light stability of PP and reduced the photo degradation of PP by about 83.2%. Therefore, the prepared novel HALS–LDH has potential application in the field of PP as an efficient and promising light stabilizer.

Uptake of heavy metal ions in layered double hydroxides and applications in cementitious materials: Experimental evidence and first-principle study

The uptake mechanism of heavy metal ions in layered double hydroxides (LDHs) is investigated in this paper via solid-solution exchange experiments and first principle study. The uptake capacities of C-LDHs for heavy metal ions from solutions are experimentally investigated and the structures of LDHs doped with various heavy metal ions are revealed. The doped structures of LDHs are further re-established with first principle calculations. The results show that Cu2+ or Cr3+ ions are immobilized in the form of isomorphic substitution for Mg2+ and Al3+ in the plate of the layered structure, respectively, during reconstruction of calcined LDHs, forming a non-stoichiometric structure. The structure of the Cu2+ doped LDHs is identified as [Mg2+(1−x)(1−z)Cu2+(1−x)zAl3+x(OH)2] An−x/n·yH2O, where z is the molar ratio of Cu2+ to Mg2+. The structure of Cr3+ doped LDHs is identified as [Mg2+1−x Cr3+xzAl3+x(1−z)(OH)2] An−(x+z)/n·yH2O, where z is the molar ratio of Cr3+ to Al3+. The Cu2+ or Cr3+ ions in the hardened cement paste modified with calcined Mg-Al LDHs as immobilizing admixture can be efficiently removed from the pore solution and chemically stabilized in the structure of LDHs.