Mg-Al LDH Research Articles

Preparation and tribological properties of PAI/PTFE@Mg-Al LDH polymer-based solid self-lubricating materials

PAI/PTFE composites with 1 %, 2 %, 3 %, 4 % and 5 % of Magnesium aluminum hydrotalcite (Mg-Al LDH) particles were prepared by DC electric field-assisted hot-pressing sintering. The friction and wear properties of the composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water contact angle and UMT-5 friction and wear tests. The effect of the amount of Mg-Al LDH particles added on the physical properties and friction and wear properties of the composites were analyzed. Experimental results showed that the friction and wear properties of PAI/PTFE composite films can be improved by adding appropriate Mg-Al LDH particles. Among them, The PAI/PTFE polymer based solid lubrication containing 3 % Mg-Al LDH has the best friction coefficient and wear amount, the average friction coefficient is 0.0962 and the wear extent is 1.47×10−5 g. The improved tribological properties of the composite films are mainly due to the excellent mechanical properties of Mg-Al LDH and the good lubrication properties of PTFE.

Determination of methyl parathion and fenitrothion on a Mg-Al layered double hydroxide/poly-m-amino-benzenesulfonic acid film-coated glassy carbon electrode (Mg-Al LDH/p-m-ABSA/GCE)

A novel nonenzymatic electrochemical sensor with high sensitivity for detecting organic phosphate (OPS) in medicinal herbs was fabricated based on a Mg-Al layered double hydroxide (Mg-Al LDH) nanocomposite glassy carbon electrode (GCE) modified with a poly-m-amino-benzenesulfonic acid (p-m-ABSA) film. Depositing Mg-Al LDH nanocomposites onto the surface of the p-m-ABSA composite resulted in an effective electrical response by increasing the electrode surface area and enhancing the electron transfer process, so the electrocatalytic activity was significantly enhanced. The research illustrated that the fabricated sensor (Mg-Al LDH/p-m-ABSA/GCE) exhibited strong affinity, high sensitivity, and selectivity towards methyl parathion (MP) and fenitrothion (FNT). Scanning electron microscopy (SEM) was used to characterize the surface morphology of the modified electrode and showed that the p-m-ABSA film and a few p-m-ABSA nanoparticles were coated on the surface. The surface area of the electrode was further enlarged by Mg-Al LDH owing to their layered nanostructure. Under optimal conditions, the anodic current had a linear relation equal to 0.1∼20.0 µM MP and 0.01∼50.0 µM FNT, with detection limits (S/N = 3) of 33.0 nM MP and 3.5 nM FNT, respectively. Furthermore, Mg-Al LDH/p-m-ABSA/GCE was successfully used for the detection of MP and FNT in Astragalus and Magnolia medicinal herb samples.

Regulating Desolvation Activation Energy and Zn Deposition via a CTAB-Intercalated Mg-Al-Layered Double-Hydroxide Protective Layer for Durable Zn Metal Anodes.

While aqueous Zn-ion batteries (AZIBs) are widely considered as a promising energy storage system due to their merits of low cost, high specific capacity, and safety, the practical implementation has been hindered by the Zn dendrite growth and undesirable parasitic reactions. To address these issues, a unique hydrophobic-ion-conducting cetyltrimethylammonium bromide-intercalated Mg-Al-layered double-hydroxide protective layer was constructed on the Zn anode (OMALDH-Zn) to modulate the nucleation behavior and desolvation process. The hydrophobic cetyl group long chain can inhibit the hydrogen evolution reaction and Zn corrosion by repelling water molecules from the anode surface and reducing the desolvation activation energy. Meanwhile, the Mg-Al LDH with abundant zincophilic active sites can modulate the Zn2+ ion flux, enabling the dendrite-free Zn deposition. Benefiting from this interfacial synergy, a long cycle life (>2300 h) with low and stable overpotential (<18 mV at 1 mA cm-2) and excellent Coulombic efficiency (99.4%) for symmetrical and asymmetrical batteries were achieved. More impressively, excellent rate performance and long cyclic stability have been realized by OMALDH-Zn//MnO2 batteries in both coin-type and pouch-type devices. This low-cost, simple, and high-efficiency coordinated modulation method provides a reliable strategy for the practical application of AZIBs.

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.

Determination of Sb(V) in water samples via solid-phase extraction based on Mg–Al layered double hydroxide sorbents prior to ICP-MS

Solid-phase extraction (SPE) is an effective method for detecting trace metals. Mg-Al-layered double hydroxide (Mg-Al LDH) materials as an effective adsorbent for SPE because of its large anion exchange capacity, high yield and low cost. A new method was developed for detecting Sb(V) with SPE coupled with inductively coupled plasma mass spectrometry. Mg-Al LDH was synthesized via a simple coprecipitation method and characterized using scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometry, and X-ray photoelectron spectroscopy. Factors affecting the Sb(V) extraction efficiency, such as the eluent type and volume, solution pH, loading flow rate, sample volume, adsorbent weight, and salt concentration, were optimized. Under optimal conditions, the SPE method exhibited good linearity (R2 ≥ 0.999) in the range of 0.1–100 µg L−1 with a limit of detection equal to 0.017 µg L−1, good repeatability and reproducibility, and intraday and interday relative standard deviations of 1.84% and 1.48%, respectively. Furthermore, the method was applied to determine traces of antimony in drinking water and bottled water, and findings revealed recoveries between 82.7%–92.1%.

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.

Simultaneous determination of trace amounts of dopamine and uric acid in human plasma samples with novel voltammetric biosensor (GCE/Ppy/DEA MIP) following the thin film-µSPE method based on electrospun nanofibers

In order to achieve the aim of this study, i.e., simultaneous measurement of trace amounts of dopamine (DA) and uric acid (UA) following their preconcentration, a novel sorbent with high performance was prepared. Hence, herein, poly vinyl chloride/Mg-Al layered double hydroxide (PVC/Mg-Al LDH) electrospun nanofibers were synthesized for the thin film- micro solid phase extraction (TF-µSPE) and then, simultaneous extraction of trace amounts of DA and UA was done. Finally, DA and UA were determined simultaneously from two different human plasma samples; afterwards, glassy carbon electrode/Poly pyrrole/diethylamine (DA, UA) molecularly- imprinted polymer (GCE/Ppy/DEA (DA, UA) MIP) electrochemical biosensor was constructed. The synthesis confirmation of PVC-Mg-Al LDH electrospun nanofibers was accomplished by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR). In addition, the GCE/Ppy/DEA MIP and GCE/Ppy/DEA (non-imprinted polymer) NIP nanocomposites were characterized with field emission-scanning electron microscopy (FE-SEM). PVC, as a polymer with a large surface area and high porosity, is an appropriate candidate in the sorbent preparation process with electrospinning. The flexible interlayer region is accessible to various anionic and polar molecular species. Adding Mg-Al LDH led to an extensive surface area of electrospun nanofibers. In the case of Ppy and DEA MIP as GCE surface modifiers, Ppy increased the electroactive sites, leading to the high conductivity of the electrochemical biosensor. Besides, DEA MIP has high selectivity and sensitivity. Optimization of impressive factors on the extraction procedure was conducted by one at-time (OAT) method, and optimum conditions for the construction of electrochemical biosensor were attained with experimental design (design-expert 12.0 software). According to the optimum conditions, the wide linear range was obtained 76.6–268.1 µg mL−1 for DA and 84.1–378.2 µg mL−1 for UA with R2≥ 0.96, low detection limits ranged from 22.3 µg mL–1 for DA and 24.8 µg mL−1 for UA based on S/N = 3 and large enrichment factors. The intra-day (n = 3) and inter-day (n = 3) RSDs% were obtained in the span of 5.3% − 6.1% for DA and 4.0% − 5.6% for UA. Eventually, the efficiency of the TF-µSPE-voltammetric biosensor method was evaluated for the measuring of DA and UA in human plasma samples with satisfactory recoveries (90.2%–99.7%).

Pd@MgAl LDH/2-ThCA: A sustainable, active and recyclable nanocatalyst system for the rapid and efficient catalytic reduction of organic pollutants

Catalytic reduction of toxic pollutants such as nitroaromatics and organic dyes found in water/wastewater by heterogeneous nano-structured metallic catalysts is a promising method for wastewater treatment. The need for effective and reusable catalyst systems is recently increasing due to the soaring water pollution. For this purpose, in this study, a newly Pd@MgAl LDH/2-ThCA catalyst system was successfully developed by depositing palladium nanoparticles onto a modified MgAl LDH support, characterized and then used to eliminate these contaminants in the presence of NaBH4. Catalytic applications indicated that Pd@MgAl LDH/2-ThCA catalyst efficiently reduced 2-nitroaniline (2-NA), 4-nitrophenole (4-NP), 4-nitroaniline (4-NA), and 4-nitro-o-phenylenediamine (4-NPDA) with rate constants of 0.011 s−1, 0.0075 s−1, 0.017 s−1, and 0.02 s−1, respectively. Additionally, Pd@MgAl LDH/2-ThCA successfully degraded methyl orange (MO) and rhodamine B (RhB) with rate constants of 0.019 s−1 and 0.015 s−1, respectively. Furthermore, it was found that methylene blue (MB) was immediately degraded by Pd@MgAl LDH/2-ThCA. Reusability tests revealed that Pd@MgAl LDH/2-ThCA maintained its activity/stability after the 5 successive cycles, verifying its practical application potential. This paper reveals that Pd@MgAl LDH/2-ThCA is an effective, sustainable, and alternative catalyst system for the treatment of toxic environmental pollutants.

Insights into the adsorption of lead ions by Mg-Al LDH doped activated carbon composites: Implications for fixed bed column and batch applications

In this study, we developed granular activated carbon-doped Mg-Al LDH composites (MgAl@AC) with an Mg:Al molar ratio of 3:1 using the co-precipitation method. The MgAl@AC was characterized using FE-SEM, BET-SA, TGA, XRD, and FT-IR, before and after lead adsorption. Through fixed-bed column and batch adsorption methods, we evaluated the impact of pH, adsorbent amount, initial Pb(II) concentration, temperature, duration of contact, and presence of competing ions, on the adsorption capacity of MgAl@AC. The MgAl@AC demonstrated a maximum Langmuir adsorption capacity of 94.6 mg/g for Pb(II). Through characterizing the Pb(II)-loaded material, the ion exchange, inner-sphere complexation, and electrostatic attraction were identified as the potential mechanisms of Pb(II) adsorption by MgAl@AC. The Yoon-Nelson and Clark models fit the breakthrough curve well, suggesting that adsorption occurs in surface and pore diffusion-controlled manners. Our findings indicated that MgAl@AC had excellent adsorption capacity, good selectivity, and fast kinetics, highlighting its potential for water treatment applications.

Self-repairing functionality and corrosion resistance of in-situ Mg-Al LDH film on Al-alloyed AZ31 surface

A novel Mg-Al LDH film was in-situ prepared hydrothermally in an alkaline aqueous solution on an Al-alloyed AZ31 substrate. The structural, chemical and functional characteristics of the film were explored by means of scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), polarization curve, AC impedance and salt immersion tests, respectively. The anti-corrosion results indicated that the Mg-Al LDH film on the Al-alloyed AZ31 surface could effectively protect the AZ31 from corrosion attack even after 90 days of immersion in 3.5 wt.% NaCl solution. The protection performance is surprisingly better than most of the reported coatings on Mg alloys. More interestingly, when the Mg-Al LDH film was scratched, the exposed Al-alloyed surface might gradually release metal ions and re-generate dense LDH nano-sheets in the corrosive environment to inhibit the further corrosion there, exhibiting a self-repairing behavior. The combination of the benign long-term protection and desirable self-repairing performance in this new process of surface-alloying and LDH-formation may significantly extend the practical application of magnesium alloys.

A novel smart coating with hexacyanoferrate intercalated layered double hydroxides nanoadditive for early detection of carbon steel corrosion

The detection of corrosion at early stages could increase the service life of metal-based infrastructures in a cost-effective manner. Despite the recent progress in “smart” self-reporting corrosion sensing coatings, the development of environmentally friendly systems appropriate for steel substrate used in offshore applications remains a relevant challenge. In this study, a novel smart corrosion sensing coating, based on hexacyanoferrate intercalated Mg-Al LDH nanoadditive, was developed, aiming at the detection of early-stage corrosion of carbon steel. The detection mechanism is based on the ability of hexacyanoferrate ions to react with iron cations generated during the corrosion process, giving rise to a colorimetric signal, while LDH carriers provide a controlled release of active ions under corrosion conditions. The sensing nanoadditive was embedded into a commercial pigment-free water-based acrylic polyurethane coating. The nanomaterial was characterized structurally (XRD) and morphologically (STEM). The compatibility of the additive with the polymer formulation and its influence on the resulting coating performance was investigated in terms of rheological behavior, structure (FTIR), morphology (SEM/EDS), thermal (TGA, DSC) and mechanical (adhesion, hardness) properties. The corrosion protection ability of the coating was evaluated via EIS, while the sensing functionality was analyzed by visual analysis of the surface. The developed coating successfully detects early-stage corrosion of steel substrate at a lab scale, in conditions relevant to the use of metallic structures in offshore applications, demonstrating a correlation between the level of material degradation and the spectroscopic signal associated with the presence of the LDH functional nanoadditive. Furthermore, the observed decrease in coating barrier properties, caused by the presence of LDH, was overcome by the subsequent development of a multilayer coating system. Two different topcoats (epoxy- and polyurethane-based) were surveyed for this purpose, showing an improvement in the coating barrier properties without influencing the corrosion detection functionality of the sensing layer. The results were successfully validated by standard salt spray tests. The multilayer approach opens up the possibility to model coatings with different characteristics for various operating conditions.

ВЛИЯНИЕ УСЛОВИЙ РЕГИДРАТАЦИИ НА СТРУКТУРНО-ПОВЕРХНОСТНЫЕ СВОЙСТВА ВОССТАНОВЛЕННЫХ СЛОИСТЫХ ДВОЙНЫХ ГИДРОКСИДОВ МАГНИЯ И АЛЮМИНИЯ

The results of studies to determine the effect of rehydration conditions on the structural and surface properties of reduced layered double hydroxides of magnesium and aluminum are presented. It is shown that the samples obtained by the reduction of the heat-treated initial Mg-Al LDH for 2 hours (regardless of the medium used) have specific surface area indicators (both total and external) that do not differ from the original LDH sample, and their specific pore volume increases by 1.3–1.5 times (from 0.121 to 0.159–0.183 cm3/g).

Production of renewable fuel from CO2 by Co3O4/Cr doped MgAl–LDH p-n heterojunction catalyst

Converting CO2 into renewable fuel via photocatalysis is of significance to solving the energy crisis and climate change. However, the limited electron transfer in single catalysts always limits the reduction reaction. In this work, a p-n heterojunction was constructed between Cr doped MgAl–LDH (abbreviated as LDH) and Co3O4 for visible-light-driven fuel production. Since LDH and Co3O4 both have the sufficient potentials to drive CO2 photoreduction, the constructed type-II heterojunction is more favorable for electron utilization efficiency. The optimal Co3O4/LDH heterojunction exhibited the highest CO evolution rate of 7.42 μmol•g−1•h−1 and a CO selectivity of 90.5% with TEOA as sacrificial agent. The further characterizations highlight that the addition of Co3O4 greatly improves the light absorption and the heterojunction effectively promotes the reverse migration of electrons and holes. This work investigates and verifies the designed type-II heterojunction based on MgAl–LDH, which has the guidance for the design of heterojunction catalysts and promotes the practical application of MgAl–LDH in photocatalytic region.

Enhanced Carbon Monoxide Electroreduction to &gt;1 A cm−2 C2+ Products Using Copper Catalysts Dispersed on MgAl Layered Double Hydroxide Nanosheet House‐of‐Cards Scaffolds

AbstractCu catalysts are most apt for reducing CO(2) to multi‐carbon products in aqueous electrolytes. To enhance the product yield, we can increase the overpotential and the catalyst mass loading. However, these approaches can cause inadequate mass transport of CO(2) to the catalytic sites, which will then lead to H2 evolution dominating the product selectivity. Herein, we use a MgAl LDH nanosheet ‘house‐of‐cards’ scaffold to disperse CuO‐derived Cu (OD‐Cu). With this support‐catalyst design, at −0.7 VRHE, CO could be reduced to C2+ products with a current density (jC2+) of −1251 mA cm−2. This is 14× that of the jC2+ shown by unsupported OD‐Cu. The current densities of C2+ alcohols and C2H4 were also high at −369 and −816 mA cm−2 respectively. We propose that the porosity of the LDH nanosheet scaffold enhances CO diffusion through the Cu sites. The CO reduction rate can thus be increased, while minimizing H2 evolution, even when high catalyst loadings and large overpotentials are used.

Enhanced Carbon Monoxide Electroreduction to >1 A cm-2 C2+ Products Using Copper Catalysts Dispersed on MgAl Layered Double Hydroxide Nanosheet House-of-Cards Scaffolds.

Cu catalysts are most apt for reducing CO(2) to multi-carbon products in aqueous electrolytes. To enhance the product yield, we can increase the overpotential and the catalyst mass loading. However, these approaches can cause inadequate mass transport of CO(2) to the catalytic sites, which will then lead to H2 evolution dominating the product selectivity. Herein, we use a MgAl LDH nanosheet 'house-of-cards' scaffold to disperse CuO-derived Cu (OD-Cu). With this support-catalyst design, at -0.7 VRHE , CO could be reduced to C2+ products with a current density (jC2+ ) of -1251 mA cm-2 . This is 14× that of the jC2+ shown by unsupported OD-Cu. The current densities of C2+ alcohols and C2 H4 were also high at -369 and -816 mA cm-2 respectively. We propose that the porosity of the LDH nanosheet scaffold enhances CO diffusion through the Cu sites. The CO reduction rate can thus be increased, while minimizing H2 evolution, even when high catalyst loadings and large overpotentials are used.

A simple approach to fabricate protective coatings on the surface of AZ91 alloy and its corrosion resistance

In this paper, the corrosion resistant coatings were fabricated on AZ91 Mg alloy by steam treatment using deionized water as a steam source. The treatment temperature was maintained at 150 ℃, while the treatment time was varied at 3, 6 and 9 h. The results showed that relatively dense steam coating can be formed on the surface of AZ91 alloy by steam treatment for 3-9 h, and the phase structure of steam coating was mainly composed of Mg(OH)2 and contained AlO(OH) and Mg-Al LDH. With the extension of the steam treatment time, the better the corrosion resistance of the steam coating, and the corrosion current density was as low as 10-7~10-8 A·cm-2, which was 3-4 orders of magnitude lower than AZ91 Mg alloy substrate (~10-4 A·cm-2).

Preparation of mixed matrix membranes by layered double hydroxides of amino acid intercalation and Pebax for ameliorated CO2 separation

CO2 capture, storage and utilization has been acknowledged as an important strategy for climate change mitigation. 2D materials have great advantages in gas separation due to their high aspect ratio and nano-sized thickness, such as LDH with tunable interlayer ions. In this work, 12-Aminododecanoic acid was incorporated as an intercalator between MgAl LDH layers and used as filler for the preparation of mixed matrix membranes (MMMs). Amino and carboxyl groups in amino acids could be used to enhance the performance of CO2 gas separation by quadrupole moment effect and increasing the layer spacing. The XRD pattern showed an increase in the layer spacing, while the characteristic peaks of amino and carboxyl groups were observed in the FTIR pattern and the initial characteristic peaks did not disappear, indicating that the amino acids were successfully intercalated into the LDH layer. The experimental results indicated that MMMs with 5 wt% 12AA-LDH achieved CO2 permeability of 92.57 Barrer and CO2/N2 selectivity of 50.8, which increasing by 125 % and 17 %, compared to pristine Pebax membranes. It could be observed that 2D materials can be used in gas separation by cross-linking and intercalation to preparing high performance separation membranes.

Hydration and phase conversion of MgO-modified calcium aluminate cement

This study evaluated the hydration and phase conversion of MgO-modified calcium aluminate cement (CAC). MgO was used to replace CAC at various dosages (0, 5, 10, 15, and 20 wt%) and the samples were exposed to a 60 °C atmosphere to expedite the conversion of the hydration products in CAC after curing initially at 20 °C. Microstructural analysis was carried out before and after expedited curing using various characterization techniques. During the initial curing, MgO can suppress the phase conversion, hindering the formation of stable phases (i.e., C3AH6 and AH3). After 28 days of expedited curing, a phase conversion can occur, with metastable phases converted to stable phases, due to which a strength reduction can be observed in all samples. Nevertheless, the development of hydrotalcite in samples modified with MgO could lessen the degree of the compressive strength loss. The addition of MgO can maintain the structural integrity before exposure by suppressing the conversion of metastable hydrates and after exposure through the formation of an Mg-Al LDH tetrahedral Al network as a secondary hydration product, maintaining the strength after exposure.

Enhanced bifunctional adsorption of anionic and cationic pollutants by MgAl LDH nanosheets modified montmorillonite via acid-salt activation

A novel H+ and Cl− intercalated montmorillonite@MgAl LDH (MMT-N) nanocomposite was prepared by a one-step hydrothermal method following acid-salt treatment. The MMT-N prepared by the advanced modification method contains low CO2–3contamination, high specific surface area, and high porosity. By enhancing the ion exchange of montmorillonite and LDH, efficient removal of anionic and anionic dyes was achieved without the introduction of another cation contamination. The adsorption kinetics of methyl orange (MO) and methylene blue (MB) are in accordance with the pseudo-second-order model, and the maximum adsorption amounts of methylene blue and methyl orange reached 815.998 mg g−1 and 399.836 mg g−1, respectively. The coefficient of determination (R2) and the corrected Akaike Information Criterion (AICc) revealed that the adsorption isotherm data of MO and MB on MMT-80 fitted well with Freundlich isotherm, signifying that the adsorption process was dominated by chemisorption. And the adsorption of MO and MB by MMA-80 was endothermic and exothermic, respectively. The “intercalation-split mechanism” and “ion exchange” mechanisms of MO and MB in MMA-80 were also investigated. This study provides an efficient method for the synthesis of high-performance bifunctional adsorbents for cationic and anionic pollutants and offers potential applications for practical wastewater purification.

Исследование процессов термического разложения и регидратации Mg-Al СДГ, полученных методом твердофазного синтеза

Mg-Al LDH samples of Mg4Al2(OH)12CO33,85HO composition were obtained by solid-phase synthesis. It was found that as a result of heat treatment with subsequent rehydration, synthesized Mg-Al LDH samples are reduced to the composition Mg4Al2(OH)12CO33HO, regardless of the medium and duration of treatment. It has been shown that rehydration in NaHCO3 solutions contributes to an increase in the crystallite sizes of Mg-Al LDH samples being recovered, which is not observed when Mg-Al LDH is reduced in an aqueous medium. An increase in the duration of hydration in NaHCO3 solutions leads to an increase in the crystallites of Mg-Al reduced LDH, which is not observed during rehydration in an aqueous medium.