Magnesium-aluminum Layered Double Hydroxide Research Articles

Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation

A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.

RETRACTED: Construction of self-repairing polyethersulfone membrane with high density hydrophilic microregions by two dimensional restricted channels for enhanced dyes/salts selective separation

Based on the dye/salts separation efficiency and membrane injury caused by serious pollution of dye/salts wastewater, this study constructed a 2D tight ultrafiltration membrane that could both solve the membrane injury problem and improve the dye/salts separation efficiency, the compatibility of good self-healing performance and penetration performance by 2D material magnesium-aluminum Layered double hydroxide (MgAl-LDH). The self-repairing of physical injury was achieved through the swelling effect of AMPS-PAN, this property was proved by permeate flux, the retention performance of salts in dye/salts solution, the comparison of scanning electron microscope (SEM), and the mechanical strength after physical injury. The healing of chemical injury occured through the reaction of CC and polyethersulfone chain breakage, which was confirmed by X-ray photoelectron spectroscopy (XPS), permeate flux, the retention performance of salts in dye/salts solution, and mechanical property. The high separation efficiency of dye/salts was achieved through 2D material MgAl-LDH, which was proved by separation selectivity ɑ. The compatibility of good self-healing performance and penetration performance was obtained by 2D material MgAl-LDH, which was proved by the penetration and self-healing performance. Morever, the membrane illustrated excellent both permeability and dye/sals separation efficiency, just like the permeate flux, the retention performance of sodium sulfate in methyl blue/sodium sulfate solution, the retention performance of Na2SO4 in methyl blue/Na2SO4 solution, the retention rate of methyl blue were 99.1 L/m2h, 12.5%, 7.9%, 97.7%, respectively. The results of pollution index and contact angle also proved that the membrane had anti-pollution performance.

A flame-retardant wood-based composite with magnesium–aluminium layered double hydroxides for efficient daytime radiative cooling

The incorporation of magnesium–aluminium layered double hydroxide (MgAl-LDH) nanoflakes into delignified wood sawdust is effective in providing simultaneous passive daytime radiative cooling and flame-retardant properties.

Impedance spectroscopy of solids for monitoring the adsorption kinetic of chromate ions from aqueous solution by a synthesized clay

The adsorption kinetic of chromate ions from aqueous solution was monitored by analyzing the electrical response of the adsorbent at various contact times. This process was also monitored by XRD and FTIR which confirmed the retention of chromate ions on the absorbent surface. The adsorbent used was a synthesized clay based on nitrate intercalated magnesium–aluminum layered double hydroxide (LDH). The adsorption kinetic of chromates was found to follow a pseudo-second order model. Through the contact time dependence, it was found a good correlation between the adsorbed quantity of chromates and the electrode-sample interface conductivity of the adsorbent, which showed a quasi-symmetry achieved by a plateau leading to a same equilibrium time of 60 min. A similar result was observed for the percentage removal of chromates and the relative change in capacitance of the electrode-sample interface of the adsorbent that exhibited a same maximum rate of approximately 93 %.

Enhancing adsorption capacity of magnetic magnesium-aluminum layered double hydroxide by surface modification with sodium dodecyl sulfate for efficient removal of organic contaminants

A magnetic magnesium-aluminum layered double hydroxide (Mag-MgAl) was prepared, and its surface was modified using surfactant sodium dodecyl sulfate (SDS) and utilized as adsorbents for antibiotic ciprofloxacin (CIP) and dyes ponceau red (PR) and methylene blue (MB). Mag-MgAl/SDS demonstrated twice the adsorption capacity for CIP compared to Mag-MgAl, confirming that the surface modification by SDS aided the adsorption capacity. At pH 3.5, Mag-MgAl removed CIP and PR, attributed to electrostatic effect and hydrogen bonding, whereas it did not interact with MB. Conversely, Mag-MgAl/SDS successfully removed both MB and CIP, suggesting that SDS micelles acted as nanoreactors attracting cationic contaminants. The PR removal efficiency was low, possibly due to electrostatic repulsion. A binary dye system adsorption assessment was performed by mixing MB and PR aqueous solutions with Mag-MgAl and Mag-MgAl/SDS as selective adsorbents. Mag-MgAl removed around 80% of PR and 45% of MB, whereas Mag-MgAl/SDS removed less than 40% of PR and 80% of MB. SDS remains adsorbed on the surface of Mag-MgAl/SDS after the adsorption process of CIP, MB, or PR. The inversion in the affinity for the target molecules suggests that the surface of the composite can be adjusted to modulate the behavior of the adsorbent toward organic contaminants.

Dental material based on poly(methyl methacrylate) with magnesium-aluminum layered double hydroxide (MgAl-LDH) on bio-silica particles

The MgAl-LDH@SiO2 particles are prepared by the coprecipitation of LDH on silica originating from plants. Particles are of submicron size and are well dispersed in the matrix. Composites consisting of PMMA reinforced with MgAl-LDH@SiO2 particles have improved hardness and resistance to viscoelastic deformation, as tested by microhardness measurements.

Synthesis of High-Crystallinity Mg-Al Hydrotalcite with a Nanoflake Morphology and Its Adsorption Properties for Cu2+ from an Aqueous Solution

A magnesium–aluminum-layered double hydroxide (Mg-Al LDH) with a nano-lamellar morphology was prepared by using a homogeneous precipitation and hydrothermal method, and a calcination product (Mg-Al LDO) of the Mg-Al LDH was also obtained in this work. The XRD, TEM, SEM, FTIR, N2 ad/desorption, and TG-DTG techniques were employed to characterize the microstructures, morphologies, and thermostability levels of these two materials in detail. The results showed that both the Mg-Al LDH and Mg-Al LDO had mesoporous structures and nanoplate morphologies, with diameters of 50~200 nm. The Mg-Al LDH was transformed into Mg-Al LDO at 773 K in an air atmosphere. The adsorption properties of the Mg-Al LDH were investigated systematically with a copper chloride solution as a simulated waste. The experimental results demonstrated that the pH value of the solution had an obvious influence on its Cu2+ adsorption capacity, and the optimal pH value was approximately 5.0. The adsorption kinetics results showed that the Mg-Al LDH had a rapid adsorption rate, and the equilibrium adsorption capacity was 62.11 mg/g. Additionally, the Cu2+ adsorption could be commendably described using a pseudo-second-order model, demonstrating that the adsorption behavior is regulated by chemical sorption. The adsorption thermodynamic results indicated that the adsorption process was spontaneous at temperatures above 318 K. Moreover, the ΔG0 values decreased as the temperature was raised, which indicated that a higher temperature can cause a greater impetus for Cu2+adsorption. In addition, the positive values of the ΔH0 indicated that the Cu2+ adsorption was endothermic, and the positive ΔS0 values revealed an increase in the confusion at the solid–liquid interface of the adsorbent.

The effect of Zr(IV) addition on the phosphate removal properties of MgAl-LDH

Recovery of phosphate from wastewater represents a sustainable alternative to phosphate rock, a limited resource. Magnesium aluminum layered double hydroxides (MgAl-LDH), are promising sorbents due to their high phosphate removal capacity by anion-exchange (26–124 mgP/g). Furthermore, an increased sorption capacity has been reported by the addition of zirconium (Zr(IV)) into the LDH lattice. However, ambiguity exists especially in relation to the incorporation of Zr and the stability of the MgAl-LDH. To understand how Zr(IV)-addition affects the phosphate sorption properties (both capacity and mechanism) on the atomic level, solid state multi-nuclear NMR spectroscopy was combined with complimentary characterization techniques to study a series of MgAl-LDH with Zr to Al ratios of 1:9 and 1:1, which had the Mg to (Al + Zr) ratio fixed at 2:1. The LDH were synthesized by coprecipitation and subsequently aged or hydrothermally treated to improve the crystallinity (particle size). No evidence of Zr(IV) incorporation in the LDH was observed, instead Zr was present as Zr(IV)-hydroxide (X-ray amorphous) and crystalline Zr(IV) oxide after aging and hydrothermal treatment, respectively. The segregation of Zr(IV) and resulting lower Al content in the MgAl-LDH decreased the phosphate sorption capacity from 45 to 54 to 16–20 mgP/g. Zr (hydr)oxide impurities removed <3 mgP/g. Moreover, 31P MAS NMR spectroscopy quantified that the MgAl-LDH contributed to <62% of the total P removal capacity.

Smart Inhibition Action of Amino Acid-Modified Layered Double Hydroxide and Its Application on Carbon Steel.

Surface impregnation of concrete structures with a migrating corrosion inhibitor is a promising and non-invasive technique for increasing the lifetime of existing structures that already show signs of corrosion attack. The main requirement for inhibitors is their ability to diffuse the rebar at a sufficient rate to protect steel. The use of smart nanocontainers such as layered double hydroxides (LDH) to store corrosion inhibitors significantly increases efficiency by providing an active protection from chloride-induced corrosion. The addition of LDH to reinforced mortar can also improve the compactness and mechanical properties of this matrix. Here, we report the synthesis of a magnesium-aluminum LDH storing glutamine amino acid as a green inhibitor (labeled as Mg-Al-Gln), which can be used as a migrating inhibitor on mortar specimens. The corrosion behavior of the specimens was determined via electrochemical techniques based on measurements of corrosion potential and electrochemical impedance spectroscopy. A cell containing a 3.5% NaCl solution was applied to the mortar surface to promote the corrosion of embedded rebars. The specimens treated with Mg-Al-Gln presented an improved corrosion protection performance, exhibiting an increase in polarization resistance (Rp) compared to the reference specimens without an inhibitor (NO INH). This effect is a consequence of a double mechanism of protection/stimuli-responsive release of glutamine and the removal of corrosive chloride species from the medium.

Effect of modified MgAl-LDH coating on corrosion resistance and friction properties of aluminum alloy

The in-situ growing approach was utilized in this article to construct the magnesium–aluminum layered double hydroxide (MgAl-LDH) film on the surface of a 1060 aluminum anodized film. To improve the corrosion resistance and friction qualities of aluminum alloy, the MgAl-LDH coating was treated using stearic acid (SA) and thiourea (TU). The aluminum substrate and anodized aluminum film layer corroded to varying degrees after 24 h of immersion in 3.5% (mass) NaCl solution, while the modified hydrotalcite film layer continued to exhibit the same microscopic morphology even after being immersed for 7 d. The results show that the synergistic action of thiourea and stearic acid can effectively improve the corrosion resistance of the MgAl-LDH substrate. The tribological testing reveals that the hydrotalcite film layer and the modified film layer lowered the friction coefficient of the anodized aluminum surface substantially. The results of the simulations and experiments demonstrate that SA forms the dense LDH-TU interlayer film layer by exchanging NO3– ions between TU layers on the one hand and the LDH-SA film layer by adsorption on the surface of LDH on the other. Together, these two processes create LDH-TU-SA, which can significantly increase the substrate's corrosion resistance. This synergistically modified superhydrophobic and retardant hydrotalcite film layer offers a novel approach to the investigation of wear reduction and corrosion protection on the surface of aluminum and its alloys.

Intercalation and separation of isomeric nitrophenols using the anionic clay, Mg2Al(OH)6(CO3)0.5·nH2O and the structurally related layered hydroxy salt, Ni3Zn2(OH)8(CH3COO)2·mH2O

Intercalative sorption of isomeric nitrophenolates (NP) was investigated in two different layered hydroxide materials - anionic clay, magnesium aluminium layered double hydroxide (MgAl-LDH) through reconstructive mechanism and the structurally related layered hydroxy salt, Ni3Zn2(OH)8(CH3COO)2·mH2O (NiZn-LHS) through ion-exchange. Intercalation of NP isomers was confirmed by powder X-ray diffraction and infrared spectroscopy. The NP uptake by the layered hydroxide materials was quantified by high performance liquid chromatography. Both the layered hydroxide materials exhibit selective intercalation from the nitrophenolate mixtures. The order of preference is 4-NP > > 2-NP > 3-NP in MgAl-LDH and 4-NP > 2-NP > > 3-NP in NiZn-LHS. The bias in intercalation could be attributed to (1) the concentration of the phenolate ions influenced by the pKa of the isomer and (2) extent of H-bonding of the nitro group of the isomer with the hydroxide slabs. The 4-isomer with lower pKa and better H-bonding with the adjacent hydroxide slabs is preferentially intercalated. The anionic clays can be used to sorb out nitrophenols as well as separate them from their mixtures.

Efficient and Superstable Mineralization of Toxic Cd2+ Ions through Defect Engineering in Layered Double Hydroxide Nanosheets

Water and soil pollution caused by toxic cadmium ions (Cd2+) is a serious threat to animals, plants, and human health. Discovering low-cost mineralizers which can efficiently and stably immobilize Cd2+ ions is therefore imperative for wastewater treatment and soil remediation. In this work, we report the successful development of a novel mineralizer for Cd2+ ion capture. A magnesium–aluminum layered double hydroxide (MgAl-LDH) with a monolayer structure (MgAl-mono) was first prepared and then calcined at 350 °C for 4 h to produce a defective MgAl-mono-350. MgAl-mono-350 offered a very high Cd2+ removal capacity (1385.5 mg/g at 25 °C) and the ability to reduce the concentration of Cd2+ in aqueous solution from 100 ppm to less than 50 ppb in 15 min (meeting the discharge standard of industrial wastewater). Detailed characterization and computational studies revealed that MgAl-mono-350 possessed abundant oxygen defects, thereby enabling superstable mineralization of Cd2+ via isomorphous substitution process,and the Cd2+ ions are immobilized in the generated CdAl-LDH structure. MgAl-mono-350 also offered outstanding selectivity for Cd2+ ions over other common ions. This work demonstrates the potential of defect-engineered LDH materials for the selective removal of heavy metals from polluted water.

Intercalation and Separation of Isomeric Nitrophenols Using the Anionic Clays, Magnesium Aluminium Layered Double Hydroxide and Nickel Zinc Layered Hydroxy Salt

Intercalation and Separation of Isomeric Nitrophenols Using the Anionic Clays, Magnesium Aluminium Layered Double Hydroxide and Nickel Zinc Layered Hydroxy Salt

Enhanced Bactericidal Effect of Calcinated Mg-Fe Layered Double Hydroxide Films Driven by the Fenton Reaction.

Osteogenic and antibacterial abilities are the permanent pursuit of titanium (Ti)-based orthopedic implants. However, it is difficult to strike the right balance between these two properties. It has been proved that an appropriate alkaline microenvironment formed by Ti modified by magnesium-aluminum layered double hydroxides (Mg-Al LDHs) could achieve the selective killing of bacteria and promote osteogenesis. However, the existence of Al induces biosafety concerns. In this study, iron (Fe), an essential trace element in the human body, was used to substitute Al, and a calcinated Mg-Fe LDH film was constructed on Ti. The results showed that a proper local alkaline environment created by the constructed film could enhance the antibacterial and osteogenic properties of the material. In addition, the introduction of Fe promoted the Fenton reaction and could produce reactive oxygen species in the infection environment, which might further strengthen the in vivo bactericidal effect.

Synthesis and selenate removal of magnesium–aluminum-layered double hydroxide particle using magnesium oxide

Synthesis and selenate removal of magnesium–aluminum-layered double hydroxide particle using magnesium oxide

Design and fabrication of enhanced corrosion-resistant LDH-Zn-G/Ni dual-layer structural coatings on magnesium alloys

A particular dual-layer structure of reinforced anti-corrosion magnesium aluminum-layered double hydroxide - Zn-G/Ni coating (LDH-ZGN), grown in situ the magnesium aluminum-layered double hydroxide coating (LDH) on the surface of the magnesium alloy, and a Zn-G/Ni composite coating was deposited on the LDH coating by low-pressure cold gas spraying (LPCGS). The LDH-ZGN was characterized by XRD, XPS, SEM, EDS, etc. The coating's corrosion protection and enhancement effect were explored through the electrochemical test of polarization curve, EIS, and coating immersion test. LDH-ZGN exhibited excellent corrosion resistance, mainly attributed to the synergy between reduced graphene oxide (rGO) and magnesium aluminum-layered double hydroxides (MgAl-LDH) and the enhancement effect of the coating under the particular dual-layer structure. • Build a dual-layer structural coating on the surface of the Mg alloy. • The cooperation of MgAl-LDH and rGO improves corrosion resistance. • rGO and Ni synergistically enhance the protective effect of the LDH-ZGN coating.

Enhanced Corrosion and Wear Resistance of LA43M Magnesium-Lithium Alloy with Magnesium-Aluminum Layered Double Hydroxide Coating

Enhanced Corrosion and Wear Resistance of LA43M Magnesium-Lithium Alloy with Magnesium-Aluminum Layered Double Hydroxide Coating

Poly(L-lactic acid)/poly(ethylene oxide) based composite electrospun fibers loaded with magnesium-aluminum layered double hydroxide nanoparticles

Two types of MgAl layered double hydroxide nanoparticles, MgAl LDH, at Mg:Al ratio of 2:1 and 3:1were prepared and used as inorganic fillers to improve the mechanical properties of poly(lactic acid)/poly(ethylene oxide) (PLA/PEO) electrospun composite fibers. Their detailed structural characterization was performed using X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) techniques. Spectroscopic, thermal, mechanical, and morphological properties of the electrospun composite fibers, and cell proliferation on their surface, were examined. XRD and TEM analyses showed that the LDH nanoparticles were 50 nm in size and the Mg:Al ratio did not affect the average spacing between crystal layers. Fourier transform infrared (FTIR) and thermal analyses (TA) revealed the compatibility of the filler and the polymer matrix. The nanoparticles considerably improved the mechanical properties of the electrospun mats. The tensile strength and elongation at break values of the composite samples increased from 0.22 MPA to 0.40 MPa and 12.2 % to 45.66 %, respectively, resulting from the interaction between LDH and the polymer matrix. Scanning electron microscopy (SEM) and MTT analyses demonstrated that the electrospun composite fibers supported the SaOS-2 cells attachment and proliferation on the fiber surfaces, along with their suitable cytocompatibility.

Novel Magnetic Molecularly Imprinted Polymer (MMIP) Based on a Magnesium-Aluminum Layered Double Hydroxide for the Selective Dispersive Micro-Solid-Phase Extraction (SPE) of Fenitrothion with Analysis by Ion Mobility Spectrometry

A novel magnetic molecularly imprinted polymer (MMIP) based on magnesium-aluminum layered double hydroxide was synthesized and employed for the selective dispersive micro-solid phase extraction of fenitrothion prior to its determination using ion mobility spectrometry. The characterization of the prepared MMIP was performed using x-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, vibrating sample magnetometry, and field emission scanning electron microscopy (FE-SEM). The adsorption capacity of magnetic layered double hydroxide modified with molecularly imprinted polymer (mag-LDH@MIP) was 24.0 mg g−1. The factors affecting extraction efficiency were optimized. Using the optimized conditions, the developed method provided favorable linearity (5.0–200.0 μg L−1), a low limit of detection (1.1 μg L−1), and a high preconcentration factor (67). The values for the intra- and inter-day relative standard deviation (n = 5) for fenitrothion were 3.3 and 4.5%, respectively. This developed method was successfully employed to determine trace quantities of fenitrothion in food and water.

Adsorption of Chromate Ions by Layered Double Hydroxide-Bentonite Nanocomposite for Groundwater Remediation.

Herein, magnesium/aluminum-layered double hydroxide (MgAl-LDH) and bentonite (BT) nanocomposites (LDH–BT) were prepared by co-precipitation (CP), exfoliation–reassembly (ER), and simple solid-phase hybridization (SP). The prepared LDH–BT nanocomposites were preliminarily characterized by using powder X-ray diffractometry, scanning electron microscopy, and zeta-potentiometry. The chromate adsorption efficacies of the pristine materials (LDH and bentonite) and the as-prepared nanocomposites were investigated. Among the composites, the LDH–BT_SP was found to exhibit the highest chromate removal efficiency of 65.7%. The effect of varying the LDH amount in the LDH–BT composite was further investigated, and a positive relationship between the LDH ratio and chromate removal efficiency was identified. The chromate adsorption by the LDH–BT_SP was performed under various concentrations (isotherm) and contact times (kinetic). The results of the isotherm experiments were well fitted with the Langmuir and Freundlich isotherm model and demonstrate multilayer chromate adsorption by the heterogeneous LDH–BT_SP, with a homogenous distribution of LDH nanoparticles. The mobility of the as-prepared LDH–BT_SP was investigated on a silica sand-filled column to demonstrate that the mobility of the bentonite is dramatically decreased after hybridization with LDH. Furthermore, when the LDH–BT_SP was injected into a box container filled with silica sand to simulate subsurface soil conditions, the chromate removal efficacy was around 43% in 170 min. Thus, it was confirmed that the LDH–BT prepared by solid-phase hybridization is a practical clay-based nanocomposite for in situ soil and groundwater remediation.