MgAl-layered Double Hydroxide Research Articles

Development of a low carbon binder system based on metakaolin: Focus on corrosion inhibitor-intercalated layered double hydroxides

In this work, MgO-CaO activated blends were produced by using metakaolin (MK). Roles of sodium nitrite (NaNO2) corrosion inhibitor on phase assemblance, micro-structure, and chloride binding of layered double hydroxides (LDH) in the systems were systematically studied. The results showed that the compressive strength in the middle and late stages were increased for 32.78% and 73.74% with the addition of CaO, and pore structure of the MgO-CaO-MK blends was optimized. After the addition of 5% NaNO2, NO2− anions were preferably intercalated into the layers of self-formed MgAl LDH and CaAl LDH. The chloride binding capacity of the samples was stronger than that of cement paste, which was attributed to the generation of more LDH by accelerating hydration of the system.

Selective Covalent Basal Plane Modification as a Probe of Hydroxide Ion Conduction Pathways in Magnesium Aluminum Layered Double Hydroxides.

Understanding ionic conduction in layered double hydroxides (LDHs) is a crucial step towards utilizing them as solid, hydroxide ion-conducting electrolytes in energy conversion applications. We selectively modified the interlayer and external surfaces of MgAl LDHs with tris(hydroxymethyl)aminomethane (TRIS) ligands. By adjusting the concentration of the TRIS surface modifier, the LDH basal plane surfaces could be functionalized everywhere (internally and externally) or only externally. External modification resulted in loss of OH-conductivity compared to pristine LDHs, confirming that external platelet surfaces are the primary ion conduction pathway.

Unraveling of Tectona grandis reduced palladium nanoparticles decorated on Mg-Al layered double hydroxide as an efficient nanocatalyst for cross-coupling reactions and azo dye degradation

An eco-friendly approach for encapsulating active noble metal nanoparticles (NPs) onto inert support materials and utilizing these nanocatalysts with confined approaches is paving the way for betterment. This paper provides a brief explanation for implementing a biogenic protocol for fabricating palladium nanoparticles (Pd NPs) onto Mg-Al layered double hydroxide (Mg-Al-LDH) using Tectona grandis leaves extract (TGLE) as capping and reducing agents to develop Mg-Al-LDH@TGLE Pd nanocatalyst. The structural and chemical features of the developed nanocatalyst are well characterized by different spectroscopic and analytical techniques. Owing to the significance of Pd NPs in cross-coupling reactions, the Mg-Al-LDH@TGLE Pd nanocatalyst was examined for its catalytic performance in the Hiyama and denitrogenative cross-coupling reactions for the formation of biaryls. Further, the nanocatalyst demonstrated great proficiency in the degradation of the azo dye methyl orange (MO). The Mg-Al-LDH@TGLE Pd nanocatalyst gave pronounced results with good stability and selectivity for both reactions with recyclability up to four cycles. This study presents a greener approach avoiding complicated methodologies for support materials and their advances in catalytic reactions.

Optimization of Mg-Al Layered Double Hydroxide Film Preparation and Corrosion Resistance Study on AZ91D Mg Alloy by Multivariate Polynomial Regression Fitting.

Layered double hydroxide (LDH) films have received extensive attention for their unique physical barrier function and ion exchange properties, which make them promising candidates for corrosion protection of magnesium alloys. In this paper, we used the multiple polynomial regression fitting method to establish a regression equation for the electrochemical corrosion resistance with the reaction temperature (T), pH, and reaction time (t) of the Mg-Al LDH film on the AZ91D magnesium alloy. The goodness of fit, confidence, and residual analyses confirmed the high accuracy of the model equation. According to the calculation using the fmincon function, the best corrosion resistance of the prepared samples could be achieved when the parameters are T = 135 °C, pH = 12.0, and t = 15 h. Then, the experimental results showed that the corrosion current density (Icorr) of the obtained LDH film under the above conditions could be 1.07 × 10-7 A/cm2, approximately 3 orders of magnitude lower than the magnesium alloy substrate, after immersion in a 3.5 wt % NaCl solution for 180 h, the surface structure of the LDH film did not change significantly, and the Icorr was still 2 orders of magnitude higher than that of the magnesium alloy substrate. Hence, a synergistic effect equation for the reaction temperature, pH, and reaction time on the corrosion resistance of the LDH film on a magnesium alloy surface prepared by the hydrothermal method was obtained. Moreover, using this equation, we obtained an LDH film with good corrosion resistance and durability, providing theoretical guidance for optimizing the process of preparing the LDH film by the hydrothermal method in practical applications.

Layered Double Hydroxides Reduce the Availability of Cadmium and Lead in Soil and the Content of Cadmium and Lead in Grain

ABSTRACT Layered double hydroxides (LDHs) have excellent immobilization effects on heavy metals (HMs) in water and soil. For the first time in Hunan province, the immobilization effect of Ca-Al LDH (SR-02-02) and Mg-Al LDH (SR-02-03) for the remediation of Cd and Pb was examined in contaminated soils. With treatments of SR-02-02 at 3000 kg/ha(L2–3), the immobilization effect of available Cd and Pb was 54.74% and 20.85%; with treatments of SR-02-03 at 3000 kg/ha(L3–3), the immobilization effect of available Cd and Pb was 68.02% and 26.70%, which showed that Cd, and Pb were gradually solidified into stable oxidizable and residual state. Less HMs were absorbed by rice as a result of the immobilization effect of SR-02-02 and SR-02-03, and the concentration of Cd and Pb in the root, stem, husk, and grain of rice were also significantly reduced. In particular, under the treatment of L2–3, the content of Cd and Pb in grain decreased by 69.13% and 72.67%, respectively; under the treatment of L3–3, the content of Cd and Pb in grain decreased by 80.76% and 100%, respectively. This was because LDHs materials reacted with HMs to form Cd-OH, Pb-OH, CdAl-LDH, and Ca/Mg-O-Pb etc. which reduced the availability of HMs. In conclusion, LDHs material is a promising material for the synergistic remediation of Cd and Pb contaminated soil.

Unfolded graphene riveted on layered double hydroxide as a highly efficient enhancer for the corrosion protective performance of zinc-rich epoxy coatings

The performance enhancement of zinc-rich epoxy coating brought by embedding conventional graphene nanosheets (GNs) is severely restricted due to the inevitable crumpling and folding nature of two-dimensional GNs. Herein, unfolded GNs are riveted on both sides of MgAl-layered double hydroxides (LDHs) via chemical graft method, achieving a novel LDHs/GNs nanocomposites (LGs). Experimental results reveal that, compared with pristine zinc-rich epoxy coatings (ZREs), the cathodic protection duration of LG/ZREs is roughly tripled under an ultra-low loading of net GNs (0.007 wt%), and this performance is even better than 0.2 wt% GNs-embedded ZRE. Compared with conventional GNs with crumpling and folding morphology, unfolded GNs riveted on LDHs perform better in “bridging” the available zinc powders into integrated conductive pathway and twisting the diffusion path of diffusing species in coating matrix.

A new method for preparing Mg-Al-layered double hydroxides coating using supercritical CO2 fluid

A new method for preparing Mg-Al-layered double hydroxides (Mg-Al-LDHs) coating using supercritical CO2 fluid was developed. The morphologies, structures, compositions, and corrosion resistances of the surface coatings were investigated. Unlike traditional methods, the method using supercritical CO2 fluid generated ultrafine nanocrystal coatings with an average size of 30 nm, and a thickness of ca. ∼ 11 μm. The Mg-Al-LDHs coating was mainly composed of C, O, Mg, and Al. Corrosion resistance measurements show that the amount of hydrogen evolution for the nanocrystal LDHs coating was only 0.133 mL·cm−2, the polarisation resistance was 3174.9 Ω·cm2, and the immersion test corrosion grade of 7G. Finally, the formation mechanism of the Mg-Al-LDHs coating under supercritical CO2 fluid was proposed.

A Novel Coating System Based on Layered Double Hydroxide/HQS Hierarchical Structure for Reliable Protection of Mg Alloy: Electrochemical and Computational Perspectives.

Growing research activity on layered double hydroxide (LDH)-based materials for novel applications has been increasing; however, promoting LDH layer growth and examining its morphologies without resorting to extreme pressure conditions remains a challenge. In the present study, we enhance LDH growth and morphology examination without extreme pressure conditions. By synthesizing Mg-Al LDH directly on plasma electrolytic oxidation (PEO)-treated Mg alloy surfaces and pores at ambient pressure, the direct synthesis was achieved feasibly without autoclave requirements, employing a suitable chelating agent. Additionally, enhancing corrosion resistance involved incorporating electron donor-acceptor compounds into a protective layer, with 8-Hydroxyquinoline-5-sulfonic acid (HQS) that helps in augmenting Mg alloy corrosion resistance through the combination of LDH ion-exchange ability and the organic layer. DFT simulations were used to explain the mutual interactions in the LDH system and provide a theoretical knowledge of the interfacial process at the molecular level.

Photocatalytic activity of the biogenic mediated green synthesized CuO nanoparticles confined into MgAl LDH matrix

The global concern over water pollution caused by organic pollutants such as methylene blue (MB) and other dyes has reached a critical level. Herein, the Allium cepa L. peel extract was utilized to fabricate copper oxide (CuO) nanoparticles. The CuO was combined with MgAl-layered double hydroxides (MgAl-LDHs) via a co-precipitation method with varying weight ratios of the CuO/LDHs. The composite catalysts were characterized and tested for the degradation of MB dye. The CuO/MgAl-LDH (1:2) showed the highest photocatalytic performance and achieved 99.20% MB degradation. However, only 90.03, 85.30, 71.87, and 35.53% MB dye was degraded with CuO/MgAl-LDHs (1:1), CuO/MgAl-LDHs (2:1), CuO, and MgAl-LDHs catalysts, respectively. Furthermore, a pseudo-first-order rate constant of the CuO/MgAl-LDHs (1:2) was 0.03141 min−1 while the rate constants for CuO and MgAl-LDHs were 0.0156 and 0.0052 min−1, respectively. The results demonstrated that the composite catalysts exhibited an improved catalytic performance than the pristine CuO and MgAl-LDHs. The higher photocatalytic performances of composite catalysts may be due to the uniform distribution of CuO nanoparticles into the LDH matrix, the higher surface area, and the lower electron and hole recombination rates. Therefore, the CuO/MgAl-LDHs composite catalyst can be one of the candidates used in environmental remediation.

Multifunctional magnetic composite: MgAl-layered double hydroxide, activated carbon and magnetite on removing both different charged-dyes

The activated carbon (AC) prepared from the shells of coconut and palm, and MgAl-layered double hydroxide (MgAl-LDH) were performed as the adsorbent for removing cationic (methylene blue) and anionic (orange II) dyes in water. The precursors of AC, MgAl-LDH and Fe3O4 were mechanically mixed to provide the magnetic composites, which were investigated by XRD, FT-IR, SEM, elemental mapping, BET, VSM, zeta potential and UV–VIS. The composites showed the characteristics and the synergistic effects of AC, MgAl-LDH and Fe3O4 with large specific surface area (320 – 330 m2/g) due to AC and MgAl-LDH, and high magnetization (12.5 – 14.4 emu/g) due to Fe3O4. The composite adsorbents revealed the bifunctional active-surface on removing both methylene blue (qm = 568 – 625 mg/g) and orange II (qm = 518 – 550 mg/g) based on monolayer coverage, and pseudo-second order reaction and spontaneous process. After 5th cycle, the adsorption capacity was reduced just 6.0 – 9.3 % with high performance on the structure and magnetism.

Corrosion Protection of Steel by NO3− and NO2− Intercalated Mg-Al Layered Double Hydroxides in Simulated Pore Solutions of Alkali-Activated Slag

This paper aims to perform a comparative investigation on the corrosion protection of steel in the simulated pore solutions of alkali-activated slag (SH) by NO3− and NO2− intercalated Mg-Al layered double hydroxides (MAL) which were fabricated by the calcination rehydration method. The corrosion potential, electrochemical impedance spectroscopy, potentiodynamic polarization and corrosion condition of steel were measured. Furthermore, changes in the microstructures of NO3− intercalated MAL (MAL-N3) and NO2− intercalated MAL (MAL-N2) before and after the adsorption of chloride ion were observed by X-ray diffraction and Fourier transform infrared spectroscopy. The results show that compared to the simulated concrete pore solution (OPCH), MAL-N3 and MAL-N2 exhibit lower chloride adsorption capacities and better corrosion inhibition effects in SH. The chloride adsorption capacity of MAL-N2 is lower compared with that of MAL-N3 due to the different volumes of intercalated anions. In contrast, MAL-N2 presents superior corrosion inhibition than MAL-N3. Furthermore, the decreases in [OH−] in SH due to the additions of MAL-N3 and MAL-N2 are more prominent than those in OPCH. The different synergistic effects due to the competitive anion-exchanges in the interlayers of NO3− and NO2− intercalated MAL in the two solutions contribute to the above effects.

Synthesis and characterization of new composite from modified silica-coated MnFe2O4 nanoparticles for removal of tetracycline from aqueous solution.

In this study, a new composite from silica coated MnFe2O4 nanoparticles, diethylenetriamine, 3-chloropropyl trimethoxysilane and Mg-Al Layered Double Hydroxide (Mg-Al LDH/DETA/CPTMS/SCNPs) composite was synthesized. The Mg-Al LDH/DETA/CPTMS/SCNPs composite was examined by Fourier transform infrared spectrometer (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA) and Vibrating Sample Magnetometry (VSM). The synthesized composite exhibited magnetic property with a saturation magnetization of 0.40 emu g-1. The Mg-Al LDH/DETA/CPTMS/SCNPs composite was utilized as a successful adsorbent for removal of tetracycline from aqueous solutions. The effect of various operation factors such as initial drug concentration, adsorbent dosage, pH and contact time were investigated. The optimized variable conditions such as adsorbent dose of 60 mg L-1, drug concentration of 100 mg L-1, pH = 7 and contact time 30 min were obtained. For describing the adsorption isotherms, the Langmuir, Freundlich and Temkin adsorption models were utilized. The results indicated that the adsorption isotherm is in good agreement with Langmuir model. According to the Langmuir analysis, the maximum adsorption capacity (qm) of the Mg-Al LDH/DETA/CPTMS/SCNPs composite for tetracycline was obtained to be 40.16 mg g-1. The kinetic studies revealed that the adsorption in all cases to be a pseudo second-order process. The negative value of ΔG° and the positive value of ΔH° showed the adsorption process to be spontaneous and endothermic.

Development of anti-corrosive coating on AZ31 Mg alloy modified by MOF/LDH/PEO hybrids

The self-assembly of hybrid inorganic-organic materials on stationary platforms plays a critical role in improving their structural stability and wide usability. In this work, a novel two-step hydrothermal approach is proposed for synthesizing stable and advanced hybrid coatings on metal-oxide platforms through the surface modification of layered double hydroxide (LDH) films using novel metal-organic frameworks (MOFs). Initially, Mg-Al LDH nanocontainers, grown on a magnesium oxide layer produced through plasma electrolytic oxidation (PEO) of AZ31 Mg alloy substrate, were intercalated with cobalt via an oxidation route, providing the metallic coordination center for the MOF formation. In the subsequent step, a pioneering technique is introduced, utilizing tryptophan as the organic linker for the first time at a pH of 10. The self-assembly of cobalt- tryptophan complex, driven by the strong bonding between electrophilic sites of monomers and nucleophilic sites, facilitated the formation of a MOF network having a cloud-like structure on the surface of MgAl LDH's film. The resulting MOF-LDH encapsulation containers demonstrate exceptional electrochemical stability when exposed to a 3.5 wt.% NaCl solution, surpassing the performance of PEO and pure LDH coatings. This enhanced stability is attributed to the development of a dense top layer and a stable composition within the self-assembled MOF, effectively sealing flaws and preventing the infiltration of corrosive ions into the underlying metallic substrate. The formation mechanism of MOFs on LDH galleries is investigated using density functional theory calculations.

Uncovering thermally activated purple-to-blue luminescence in Co-modified MgAl-layered double hydroxide.

Thermally activated blue-to-purple luminescence of Co-modified nano-sandrose MgAl-layered double hydroxides (LDHs) is concentration dependent, occurring only for MgCoAl-LDH with a molar metal cation concentration of 15% Co. Temperature sweep luminescence spectroscopy between 83 K and 298 K shows that the luminescence is strongest at room temperature, increasing with an activation energy of 1 kJ mol-1 between these temperatures. The luminescence occurs in a broad, but fine-structured band below the conduction band (CB) edge at 3.0 eV after excitation at 5.0 eV.

Mg-Al LDH nanosheets as a nanotechnological tool in agriculture: An exploratory toxicity evaluation study

In this work, we studied the impact of a Mg-Al layered double hydroxide (LDH) nanosheet formulation, a nanoparticle recently recommended for the industry due to its use as a carrier...

Magnetite humic acid-decorated MgAl layered double hydroxide and its application in procion red adsorption

The magnetite humic acid-decorated MgAl layered double hydroxide (MgAl-MHA) was prepared for this investigation. After five adsorption-desorption cycles, MgAl-MHA showed remarkable reusability and an adsorption rate of about 57% without suffering appreciable loss. The MgAl-MHA's magnetic properties further improve the process of adsorption and less the possibility of the surface being harmed. The influence of temperature, initial concentration of procion red, contact time, pH value, and pHpzc on procion red removal percentage of the MgAl-MHA was investigated in detail. The pseudo-second-order kinetic model and the Langmuir isotherm model were well-fitted by the adsorption kinetics and equilibrium adsorption isotherm, respectively. The thermodynamics analysis indicated that procion red adsorption onto the MgAl-MHA was endothermic and spontaneous. Procion red has a maximum adsorption capacity of 192.037 mg/g at 303 K. In light of the findings mentioned above, MgAl-MHA presents a viable adsorbent option with high recyclability and cheap cost for the removal of procion red.

Fabrication of coal-based oxygen-rich porous carbon nanosheets for high-performance supercapacitors

The modification and optimization of porous carbon electrodes is key to achieving high-performance supercapacitors. Oxygen-rich porous carbon nanosheets (OPCNs) with a two-dimensional (2D) structure produced from the solid by-products of the coal industry were prepared by taking advantage of the rigid confinement of 2D MgAl-layered double hydroxides (MgAl-LDH) combined with KOH activation. The influence of carbonization temperature on the microstructure and surface properties of the OPCNs was investigated. The surface morphologies/compositions and surface textures of the prepared OPCNs were observed and analyzed by SEM, TEM, N2 adsorption and desorption, elemental analysis, etc. The optimized carbon sample activated at 700 °C (OPCN-700) had a high oxygen content of 24.4 wt%, a large specific surface area of 2 388 m2 g−1, and good wettability. In addition, the abundant micropores and 2D nanosheet structure of OPCN-700 provide efficient storage and transport for electrolyte ions. Because of this, when used as the electrode for a supercapacitor it has a high specific capacitance of 382 F g−1 at 0.5 A g−1, an excellent rate performance and cycling stability.

In-situ Mg-Al LDH infused lignin-derived laser scribed graphene for facilitated ion transport in flexible supercapacitor application

BackgroundInnovations in the synthesis of hybrid materials have led to technology advancement of the microsupercapacitor. Delaminated layered double hydroxide (LDH) reduces self-agglomeration and increases energy density in graphene-based supercapacitors. The incorporation of delaminated LDH with oil palm lignin derived laser scribed graphene in neutral PAAS/K2SO4 gel electrolyte for flexible microsupercapacitor applications was investigated. MethodVarious concentrations of positively charged sucrose-delaminated Mg-Al LDH nanosheets produced through the coprecipitation method were hybridised with negatively charged oil palm lignin-derived laser scribed graphene (L-LSG) through electrostatic interaction. Significant FindingsHybrid laser scribed graphene developed from delaminated Mg-Al LDH at a concentration of 10 gL−1 (L-LSG/D-MgAl-10) had the largest surface area of 49.335 m2g−1. The incorporation of Mg-Al LDH nanosheets on l-LSG were further validated by FESEM, TEM, XRD, Zeta potential and other characterizations. It also had the highest areal capacitance and energy density, measuring 40 mFcm−2 and 0.00296 mWhcm−2, respectively, at a current density of 0.08 mAcm−2. The fabricated microsupercapacitor has exceptional bending capabilities and capacitance retention of 89.2% after 5000 cycles. In summary, by inducing additional pseudocapacitance, delaminated Mg-Al LDH improved the overall effectiveness of the oil palm lignin derived graphene electrode compared to pristine graphene.

Laboratory and field performance investigation of anti-ultraviolet aging of warm-mixed asphalt concretes

MgAl-Layered double hydroxides (LDHs) is commonly applied to improve the anti-ultraviolet (UV) aging performance of SBS-modified asphalt concretes. However, LDHs elevates the mixing temperature of SBS-modified asphalt, resulting in more energy consumption and more volatile organic compounds (VOCs) emission. The surface-active warm-mixed agent (W-MA) can effectively reduce the viscosity of asphalt binder. This study explored the use of W-MA in LDHs/SBS-modified asphalt binder (LA) and LDHs/SBS-modified asphalt mixtures (LAM) to reduce the mixing temperature and VOCs emission. Firstly, the structural stability of LDHs and the effect of W-MA on viscosity reduction and VOCs emission in LA were studied. Then, the physical properties, UV aging resistance, and optimal LDHs content of warm-mixed LAM were examined. Finally, the performances of the test road applying warm-mixed LAM were investigated. The results demonstrated that the excellent structural stability of LDHs and the application of W-MA could effectively reduce the viscosity of LA and VOCs emission. Warm-mixed LAM exhibited excellent UV aging resistance and high-temperature performance. However, its low-temperature performance and moisture damage resistance performance were slightly lower than warm-mixed asphalt mixtures. The optimal LDHs content in warm-mixed LAM was found to be 3 wt%. The test road showed minor differences in road performance compared to that in the laboratory, and the test road has great anti-UV aging performance.

MODELLING AND OPTIMIZATION OF OXALIC ACID REMOVAL BY LAYERED DOUBLE HYDROXIDE

The main purpose of this study is the investigation of the optimization of the conditions of oxalic acid (OxA) adsorption using layered double hydroxide (LDH), modeling the adsorption with both the response surface methodology (RSM) and an artificial neural network (ANN). Mg-Al LDH was synthesized via the co-precipitation method and characterized by Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffraction (XRD) techniques. The equilibrium time and kinetic model data required to realize the adsorption process design were examined. The process time, initial acid concentration, temperature, and adsorbent dosage as the independent variables were chosen while measuring the percentage of OxA removal. Modeling these results with both RSM and ANN techniques resulted in an ANN model showing a slightly better coefficient of determination than the RSM model. The models yielded consistent results for the optimal conditions of the process.