Magnesium-aluminum Hydrotalcite Research Articles

Three dimensional porous magnesium aluminum hydrotalcite material doped with TiO2 and Al2O3 for fluoride removal

At present, the increasingly serious fluorine pollution in water is an enormous threat to human health, therefore, a three-dimensional porous magnesium aluminum hydrotalcite material doped with TiO2 and Al2O3 that can be used as defluorination material was synthesized by a green hydrothermal method and a series of comprehensive fluoride adsorption experiments were conducted in this study. The adsorption material has an ideal adsorption effect on fluoride due to its porous structure and various strong interactions with fluoride. The results of batch adsorption experiments indicate that the maximum adsorption capacity can reach up to 100.69 mg·g−1. Meanwhile, it can be applied in a wide pH range (3–10) and has strong resistance to the effect of coexisting anions. In addition, we explored the adsorption mechanism through DFT calculation, and found that electrostatic attraction, ion exchange, hydrogen bonding and chemisorption were the main adsorption mechanisms. Based on the above advantages, the adsorbent has a good application potential.

Preparation and mechanism of tartaric acid-intercalated hydrotalcite retarder for oil-well cement

In view of the existing problems of retarding agents, such as abnormal cementing of cement slurry, slow development of cement strength, low strength, poor thermal stability and excessive retarding, etc. In this study, tartaric acid-intercalated hydrotalcite (Mg/Al-TA-LDH) was prepared by ion exchange between tartaric acid and magnesium–aluminium hydrotalcite (Mg/Al-CO3-LDH). The results show that Mg/Al-CO3-LDH and Mg/Al-TA-LDH have typical structural characteristics of hydrotalcite. The interlayer spacing of Mg/Al-TA-LDH after intercalation is larger than that of Mg/Al-CO3-LDH prior to intercalation. Measurements of the thickening time and thickening curve of oil-well cement show that the slow release of tartaric acid has a retarding effect on the oil-well cement slurry mixed with the tartaric acid-intercalated hydrotalcite retarder, the effect is stable, and the thickening curve is stable and shows right-angle thickening. Based on the compressive strength test of oil-well cement, the strength increases gradually with the addition of 0.3%–1.0 % Mg/Al-TA-LDH promoting the development of 1 d and 3 d strength of stone cement. When the dosage of Mg/Al-TA-LDH is 1.0%, the 1 d and 3 d strength of stone cement is higher than that of pure cement, and the 3 d strength of stone cement is increased by 99.6%. The development of 7 d strength was inhibited, but the late strength development was still higher than that of pure cement, and the 14 d strength was 33.3% higher than that of pure cement. Tartaric acid-intercalated hydrotalcite can increase the thickening time of oil well cement through the release of tartaric acid, and can significantly improve the compressive strength of oil well cement through the seed promotion effect of hydrotalcite material.

Enhanced adsorption of chlorogenic acid polyphenol by layered double hydroxide modified with sodium dodecyl sulfate

Polyphenols are a class of organic contaminants highly present in wastewater from industrial and agro-industrial processes. Adsorptive processes are employed to remove contaminants from effluents without the generation of by-products. Among the challenges in removal is the search for adsorbents that have affinity and favor the interaction with the contaminant. In this sense, this paper aimed to evaluate a layered double hydroxide modified with sodium dodecyl sulfate as an adsorbent material of the chlorogenic acid polyphenol. Carbonated magnesium-aluminum hydrotalcite was the layered double hydroxide employed for modification at different sodium dodecyl sulfate contents. The results showed that the modification with 50% w w-1 sodium dodecyl sulfate increased the adsorptive capacity of the modified layered double hydroxide from 0.030 mg g-1 to 2.3 mg g-1 after 24 hours of contact with the polyphenol. Thus, the use of sodium dodecyl sulfate for surface modification of layered double hydroxide indicated positive results that favor the application of the modified material in the removal of polyphenols.

Preparation of sustained-release-type citric-acid-intercalated hydrotalcite and its application in oil-well cement

To address the problems of poor thermal stability and over-retarding of cement slurry by retarders, as well as the sensitivity to citric acid (CA) dosage and poor early strength of cement treated with hydroxycarboxylic acid retarders, CA-intercalated magnesium aluminium hydrotalcite (Mg/Al-CA-LDH, henceforth called CAIH) with a sustained-release effect was prepared by an anion exchange reaction between CA and magnesium aluminium carbonate layered double hydroxide (Mg/Al-CO3-LDH). The prepared CAIH exhibited good crystallinity and high thermal stability, and 39.92% CA could be inserted in the composite. Evaluation of the thickening and compressive strength of oil-well cement showed that the addition of CAIH effectively maintained the fluidity of the cement slurry and improved its early compressive strength. Furthermore, because of the seed effect of hydrotalcite and the microrelease of CA in CAIH, the synergistic effect of hydrotalcite and CAIH can promote the setting of oil-well cement: the effect was stable and the thickening curve was stable, indicating right-angle thickening.

Molybdate intercalated magnesium aluminium hydrotalcite as a potential catalyst for the oxidation of cinnamyl alcohol

Molybdate intercalated magnesium aluminium hydrotalcite as a potential catalyst for the oxidation of cinnamyl alcohol

Study on preparation and slow release properties of Magnesium-Al hydrotalcite with alanine intercalation

The precursors of Mg-Al hydrotalcite (Mg/Al-LDHs-NO3) were prepared by low saturation coprecipitation method (constant pH method). In addition, alsine-intercalated magnesium-aluminum hydrotalcite (LDHs-Ala) was synthesized by low saturation coprecipitation (constant pH) and nucleation/crystallization isolation methods when the pH value was higher than the isoelectric point of alanine. The release properties of alanine intercalated hydrotalc in simulated gastric fluid (hydrochloric acid solution with pH=1.5) and intestinal fluid (phosphate solution with pH=7.4) were measured by spectrophotometer in vitro. The results showed that LDHs-Ala had good slow-release properties in simulated intestinal fluid and gastric fluid in vitro. Then sodium alginate was used to coated alanine intercalated hydrotalc for slow release in simulated intestinal fluid and simulated gastric fluid. It can be concluded that the coated intercalated hydrotalc has a low slow release rate in gastric fluid, but has a good slow release performance in simulated intestinal fluid. It can be concluded that the coated intercalated hydrotalc is expected to be a intestinal targeted release agent, which can be applied in biomedicine.

Effect of magnesium aluminum hydrotalcite on the properties of CAC-bonded castables

To improve the volume stability of CAC-bonded high Al2O3-based castables with higher MgO content, magnesium aluminum hydrotalcite (MAT) was added as the MgO-bearing precursor to prepare CAC-bonded high Al2O3-based castables. The influence of MAT level on the properties of castables, i.e., physical, and thermo-mechanical properties, strengths, volumetric stability and slag corrosion resistance, was investigated. Results indicated that the volumetric stability of castables containing MAT was increased, whereas the castable strength was lowered, due to the favored pore formation from MAT decomposition in castable matrices. The increased porosity, however, did not decrease the slag corrosion resistance of CAC-bonded castables.

Influence of magnesium-aluminum hydrotalcite on the microstructure and mechanical properties of magnesia castables

The stability of the thermo-mechanical properties of magnesia castables is critical for both the service life of castables and the steel cleanliness. In this study, simultaneous use of magnesium-aluminum hydrotalcite and hydratable alumina was determined to improve the mechanical strength and volume stability of magnesia castables. Hydrotalcite was decomposed to magnesium aluminate spinel and reactive MgO below the medium temperature, which accelerated sintering reactions in magnesia castables and further promoted the formation of spinel and forsterite at high temperature. Suitable volume stability was presented as a consequence of the improved sinterability. The thermo-mechanical properties of magnesia castables were also enhanced. A modified three-dimensional microstructure with the fewer and smaller pores in this optimized magnesia castable at the same time was verified by X-ray micro-computed tomography technology. A correlation analysis identified bending strength and compressive strength of castables having the strongest relationship with the spatial porosity and the number of pores in a diameter range of 0.3–0.5 mm.

Microstructure, corrosion resistance, and antibacterial properties of an Ag/Mg-Al layered double hydroxide coating synthesized in situ on biomedical Mg-Zn-Ca alloy

A one-step hydrothermal treatment was used to deposit a nano silver-loaded magnesium-aluminum hydrotalcite (Ag/Mg-Al) layered double hydroxide (LDH) coating onto the surface of a Mg-Zn-Ca alloy to improve the corrosion resistance and antibacterial properties of magnesium alloys for biomedical applications. The effect of experimental parameters such as temperature and time on the microstructure, compositions, and corrosion resistance of the Ag/LDH coating during the hydrothermal treatment was investigated to optimize the preparation process. Additionally, the in vitro degradation performance, antibacterial performance and biocompatibility of the coating were evaluated to determine the optimal preparation condition. The results show that when the LDH–NO 3 – coating is prepared at 110 °C for 10 h, the constituting silver particles (dimensions, 10–30 nm) are obtained, while the corrosion current density and the corrosion rate decrease to 4.41 μA/cm 2 and 0.27 mm/year, respectively. The antibacterial experiment demonstrates that the coating effectively inhibits the reproduction of Escherichia coli while offering remarkable biocompatibility.

Photocatalytic Degradation of Composites with Magnesium Aluminum Hydrotalcite Derived Metal Oxides and g-C3N4

The remove of the organic pollutants in water plays an important role on the environmental protection, thus photocatalysis, as an effective method, has been attained much attention to deal with this problem. In this paper, a composite of g-C3N4 and Mg–Al hydrotalcite derived metal oxides was prepared by simple co-precipitation methods followed by calcination. The effective adsorption-photocatalysis synergic effect and highly efficient removal of organic pollutants from water under simulated sunlight irradiation was found in the presence of fabricated metal oxide nanocomposites. The photocatalytic degradation rate of methylene blue reached 97.3% within 1 h under visible light, and the degradation rate constant was 0.0432 min−1, which is 3.6 times that of g-C3N4. Though characterization analysis, more active sites are exposed to absorb more organic pollutants on the mater surface in the presence of the open hierarchical structures of composite materials, and the "face to face" contact structure between 2D materials is formed to promote the separation of electrons and holes. The photocatalytic degradation was stable in the recycling process of the catalyst. In addition, the photocatalytic degradation mechanism of the catalyst was explained by free radical scavenging experiment. The material provides an effective method for removing organic pollutants in water, and has broad application prospects.

Fabrication and characterization of flame‐retardant and smoke‐suppressant of flexible polyurethane foam with modified hydrotalcite

AbstractThe hydrotalcite has been chemically modified by using the ion exchange method to insert dihydrogen phosphate between the carbonate‐type magnesium–aluminum hydrotalcite layers. And then, the effect of modified hydrotalcite on the flame retardancy and smoke suppression properties of flexible polyurethane foam (FPUF) has been investigated using limiting oxygen index (LOI) method, cone calorimeter test (CONE), smoke density chamber, flue gas analyzer, and scanning electron microscope (SEM). The current indicated that the LOI of flame‐retardant modified FPUF was increased to 25.4%. And the peak heat release rate (PHRR) and total heat release (THR) of the samples were decreased by 74.9 kW/m2 and by 9.7 MJ/m2, respectively. Additionally, the total amount of flue gas produced by combustion was reduced by 157.7 m2/m2, and the maximum concentration of carbon monoxide (CO) gas decreased from 51.3 to 23.8 mg/m3. Based on these data, it can be found that the hydrotalcite modified by dihydrogen phosphate intercalation had an excellent flame‐retardant and smoke‐suppressant effect, and 15% of modified hydrotalcite was the most appropriate amount during the combustion process of the modified FPUFs.

Functional group hydrogenation of cinnamaldehyde to hydrocinnamyl alcohol over nickel-ruthenium containing hydrotalcite

Functional group hydrogenation of α-β unsaturated aldehydes to fine chemicals is a potential process in organic synthesis. In this study, we demonstrate the complete functional group hydrogenation of cinnamaldehyde (CAL) to hydrocinnamyl alcohol (HCOL) over magnesium aluminium hydrotalcite (MAHT) having bimetallic nickel/ruthenium (1.3% Ni and 0.74% Ru) species (MANR–HT). The catalyst shows complete conversion of CAL with 97.5% selectivity of HCOL at 150 °C and 1 MPa H2 pressure. The synergic effect of bimetallic Ni/Ru and basicity of the HT material facilitated the high catalytic activity of MANR–HT in the CAL hydrogenation. The catalyst also demonstrated comparable activity even after several runs.

Thermal stability changing caused by chromium (iii) in the carbonated magnesium-aluminum hydrotalcite

There are several purposes for investigating hydrotalcite clays and one of them is due to its importance as an anionic adsorbent and ion exchanger, which make them capable of removing various pollutants from water. The most common hydrotalcite structure is based on double lamellar hydroxide of magnesium and aluminum, containing carbonate anions in the interlayer space. However, it is common to investigate the co-substitution of aluminum with other trivalent cations, especially transition metal cations, due to their binding properties. In this work, it was investigate the co-substitution of chromium (III) and aluminum in a sample of magnesium-aluminum carbonated hydrotalcite, comparing it with the same composition without this co-substitution. Thermal stability, crystallinity and morphology were investigated, showing that chromium contributes to the adsorptive capacity at low temperature.

Preparation of Magnesium-Aluminum Hydrotalcite by Mechanochemical Method and Its Application as Heat Stabilizer in poly(vinyl chloride).

The traditional methods for preparing magnesium aluminum layered double hydrotalcite (Mg2Al-CO3LDHs) in industry include coprecipitation and hydrothermal methods. Both these methods have the disadvantages of high preparation cost and complicated water washing process. Using Mg(OH)2, Al(OH)3, and CO2 as raw materials in this work, the Mg2Al-CO3 LDHs are successfully prepared by mechanochemical method, which solves the shortcomings of traditional preparation method and realizes the conversion and utilization of CO2 resource. The prepared Mg2Al-CO3 LDHs are evaluated as a heat stabilizer in poly(vinyl chloride) (PVC). The result indicates that, when 2.4 phr Mg2Al-CO3 LDHs, 0.3 phr ZnSt2, and 0.3 phr of zinc acetylacetonate are added to the PVC, the thermal stability time of PVC can reach 190 min, which is better than PVC containing commercial Mg2Al-CO3 LDHs. Meanwhile, its processing performance is basically the same as the PVC containing commercial Mg2Al-CO3 LDHs.

Preparation of Uniform Highly Dispersed Mg–Al-LDHs and Their Adsorption Performance for Chloride Ions

Two-dimensional flaky magnesium-aluminum hydrotalcite (Mg-Al-LDHs) with uniform particle size distribution and high dispersion was prepared by the super-gravity rotating bed. The samples were chara...

Gallic and salicylic acid-functionalized Mg/Al hydrotalcite as highly effective materials for reductive adsorption of AuCl4−

Two materials as the functionalization products of magnesium aluminum hydrotalcite (Mg/Al HT) with gallic and salicylic acids have been prepared and their application to effectively remove AuCl4− has been examined. Functionalization was carried out through immobilization in which deprotonated carboxyl group of gallic and salicylic acids was the responsible functional group for the immobilization. Immobilization of both acids was optimum at pH 5.0 and matched better in Langmuir isotherm model than the Freundlich one with capacity of immobilization was 7.22 and 7.18 × 10−4 mol/g for galic and salicylic acids, respectively. In spite of both acids were immobilized at comparable amount, but gallic-acid-functionalized Mg/Al HT (Mg/Al-GA HT) had higher ability in removing AuCl4− than the salicylic-acid-functionalized Mg/Al HT (Mg/Al-SA HT). The removal capacity of Mg/Al-GA HT and Mg/Al-SA HT for AuCl4− at temperature 25 °C was 3.10 and 2.08 × 10−4 mol/g and it was 8.16 and 5.47 time-fold higher than that of Mg/Al HT. The removal of AuCl4− by Mg/Al-GA HT and Mg/Al-SA HT was exothermic and involved OH group and this functional group was responsible for not only the adsorption of AuCl4− but also reduction of AuCl4− to Au metal.

Highly efficient Nb2O5 catalyst for aldol condensation of biomass-derived carbonyl molecules to fuel precursors

Aldol condensation is of significant importance for the production of fuel precursors from biomass-derived chemicals and has received increasing attention. Here we report a Nb2O5 catalyst with excellent activity and stability in the aldol condensation of biomass-derived carbonyl molecules. It is found that in the aldol condensation of furfural with 4-heptanone, Nb2O5 has obviously superior activity, which is not only better than that of other common solid acid catalysts (ZrO2 and Al2O3), more importantly, but also better than that of solid base catalysts (MgO, CaO, and magnesium-aluminum hydrotalcite). The detailed characterizations by N2 sorption/desorption, NH3-TPD, Py-FTIR and DRIFTS study of acetone adsorption reveal that Nb2O5 has a strong ability to activate the C=O bond in carbonyl molecules, which helps to generate a metal enolate intermediate and undergo the nucleophilic addition to form a new C–C bond. Furthermore, the applicability of Nb2O5 to aldol condensation is extended to other biomass-derived carbonyl molecules and high yields of target fuel precursors are obtained. Finally, a multifunctional Pd/Nb2O5 catalyst is prepared and successfully used in the one-pot synthesis of liquid alkanes from biomass-derived carbonyl molecules by combining the aldol condensation with the sequential hydrodeoxygenation.

Preparation of CNTs/MgAl-LDHs Composites and their Adsorption Properties for Chloride Ions

Magnesium-aluminum hydrotalcite and carbon nanotube composites (CNTs/MgAl-LDHs) were prepared by one-step hydrothermal method using magnesium nitrate, aluminum nitrate and carbon nanotubes as raw materials and urea as precipitant. The samples were characterized by SEM, XRD, BET and other methods. The adsorption properties of CNTs/MgAl-LDHs on chloride ions and the factors affecting the adsorption of chloride ions were studied. The results show that the prepared CNTs/MgAl-LDHs exhibit a three-dimensional honeycomb structure with a specific surface area of 103.019 m2/g, which is larger than the specific surface area of MgAl-LDHs of 84.344 m2/g. The results showed that the optimal adsorption conditions were: adsorption temperature was 45°C, the pH value was 8, the adsorption time was 100 min, the Cl- concentration was 0.01 M (584 mg/L), and the adsorbent concentration was 1.0 g/L. CNTs/MgAl-LDHs has the best adsorption performance for chloride ions. The maximum adsorption capacity is 75.58 mg/g. The adsorption isotherms and adsorption kinetics are consistent with the Langmuir isotherm model and the quasi-secondary kinetic model.

Morphological and Structural Analyses in Carbonated Magnesium-Aluminum Hydrotalcites Co-Substituted with Iron III

Magnesium-aluminum hydrotalcites can be co-substituted with others trivalent cations, such as iron III in aluminum site, which can be a promising way to modify the properties of that synthetic adsorptive material. In the present work, hydrotalcite containing 5 mol% iron III in co-substitution to the aluminum was prepared by precipitation process and compared with no co-substituted sample along the temperature of calcination at 100 and 500 oC for 4 hours. The calcined samples were characterized by simultaneous TG/DTA, X-ray Diffraction and nitrogen adsorption-desorption techniques. The iron (III) insertion showed positive results in order to provide more stable structure against high temperatures of calcination, which was observed by lesser structural decomposition of rhombohedral hydrotalcite and a more mesoporous structure.

The Effect of Iron (III) Co-Insertion in Magnesium-Aluminum Hydrotalcites Obtained by Precipitation Method at pH 11

Hydrotalcite are anionic clay material presenting LDH arrangement and high porosity and specific areas, which make it a good adsorbent for pollutant species in water. Besides that, that material type can be used as catalyst or catalyst support in several industrial processes. The most common compositions is based on metallic mix hydroxide with high content of magnesium, but their adsorptive properties arise from aluminum replacement in layer structure. The present work presents the synthesis of carbonated magnesium-aluminum hydrotalcite through the precipitation method in order to investigate the co-insertion of iron (III) in aluminum site. It was found the iron (III) co-inserted samples obtained at 100 and 200 oC for 4 hours present no substantial harming in relation to the common magnesium-aluminum composition. All of the samples presented high porosity and specific area, becoming an alternative anionic adsorptive.