Zn Al LDH Research Articles

Preparation and multiple applications of integrated Zn-Al layered double hydroxide@polydopamine nanocomposites

The preparation and application of inorganic-organic hybrid nanomaterials is a hot research topic at present. Herein, we combined Zn-Al layered double hydroxide (Zn-Al LDH) with mesoporous polydopamine (MPDA) to prepare two integrated Zn-Al LDH@MPDA nanocomposites under the modification of linker (1,3,5-benzoyl chloride (TMC) or (3-aminopropyl) trimethoxysilane (APTMS)), namely Composite T (modified by TMC) and Composite A (modified by APTMS), which were then evaluated for dye adsorption, adriamycin hydrochloride (DOX) loading, photothermal conversion experiment, and antibacterial test. The characterization results showed that MPDA can be successfully loaded on Zn-Al LDH with the modification of the two linkers, but the specific surface area, pore-volume, average pore size, and electronegativity of Composite T were all higher than those of composite A, thus being more advantageous in adsorption of cationic dye. Composite T possesses a high loading capacity for DOX, whose loading efficiency and encapsulation efficiency are 478.3% and 95.7%, respectively. In addition, Composite T also shows a high photothermal conversion efficiency of 27.9%. Furthermore, Composite T exhibits excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococus aureus (S. aureus). Therefore, the designed Zn-Al LDH@MPDA nanocomposites would be a promising candidate for a myriad of industrial application fields.

Novel In2S3/Zn–Al LDHs composite as an efficient visible-light-driven photocatalyst for tetracycline degradation

Hexagonal Zn–Al hydrotalcite (Zn–Al LDHs) has become a research hotspot in the field of photocatalysis due to efficient photocatalytic performance, low cost and non-toxicity. In this research, In2S3/Zn–Al LDHs composites were firstly synthesized by one-pot method with InCl3 and TAA as raw materials. The crystalline structure, surface morphology, chemical composition, together with optical properties of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FT-IR), UV–Vis diffuse reflectance spectrometry (DRS), and Photoluminescence spectra (PL). The photocatalytic performance of the composite photocatalyst was investigated by degradation of tetracycline (TC) under visible-light irradiation. The photochemical properties and cyclic stability of the photocatalyst were further explored. Experimental results display that the photocatalytic efficiency of In2S3/Zn–Al LDHs (1:2) was remarkably superior to that of pure In2S3 and Zn–Al LDHs. In2S3/Zn–Al LDHs (1:2) composite showed high photocatalytic activity for TC degradation (92.2% within 30 min). The modification of Zn–Al LDHs by In2S3 prompted the separation of photogenerated electron-hole pairs and thus improved the photocatalytic performance. It can be inferred that the efficient photocatalytic performance of In2S3/Zn–Al LDHs composites could remove many hazardous pollutants in wastewater.

Mechanochemically prepared Zn–Al LDH precursor for rare earth elements recovery

The ionic rare earth elements (REEs) was mainly recovered by in-situ leaching process. The concentration of rare earth ions in the leaching solution after long-term leaching process would be too low for traditional precipitation process for REEs recovery. The adsorption process was ideal for the low concentration REEs recovery. In this study, Zn–Al LDH precursor were successfully synthesized by mechanochemical method for the adsorption of REEs (including La−, Eu3+ and Er3+). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron energy spectrometer (XPS), and Zeta potential test was applied for adsorption mechanism illustration. The maximum adsorption capacity of the Zn–Al LDH precursor for La3+, Eu3+ and Er3+ reached 492 mg/g, 346 mg/g, and 1154 mg/g which was significantly higher than other types of adsorbents. The adsorbed REEs on the Zn–Al LDH was hard to be desorbed. The Zn–Al LDH precursor after REEs adsorption could be directly used as high content REEs resources for further process.Therefore, the Zn–Al LDH precursor could be a promising adsorbent for REEs recovery in practical application.

“Smart” nanosensors for early detection of corrosion: Environmental behavior and effects on marine organisms

Corrosion is an environmental and economic global problem. “Smart” or stimuli-responsive colorimetric nanosensors for maritime coatings have been proposed as an asset to overcome the limitations of the current monitoring techniques by changing color in the presence of triggers associated with the early stages of corrosion. Layered double hydroxides (Zn–Al LDH; Mg–Al LDH) and silica mesoporous nanocapsules (SiNC) were used as precursor nanocarriers of active compounds: hexacyanoferrate ions ([Fe(CN)6]3-) and phenolphthalein (PhPh), respectively. Additionally, the safer-by-design principles were employed to optimize the nanosensors in an eco-friendly perspective (e.g., regular vs. warm-washed SiNC-PhPh; immobilization using different carriers: Zn–Al LDH-[Fe(CN)6]3- vs. Mg–Al LDH-[Fe(CN)6]3-). Therefore, the present study aims to assess the environmental behavior in saltwater and the toxic effects of the nanosensors, their nanocarriers, and the active compounds on the marine microalgae Tetraselmis chuii and the crustacean Artemia salina.Briefly, tested compounds exhibited no acute toxic effects towards A. salina (NOEC = 100 mg/L), apart from SiNC-PhPh (LC50 = 2.96 mg/L) while tested active compounds and nanosensors caused significant growth inhibition on T. chuii (lowest IC50 = 0.40 mg/L for SiNC-PhPh). The effects of [Fe(CN)6]3- were similar regardless of the nanocarrier choice. Regarding SiNC-PhPh, its toxicity can be decreased at least twice by simply reinforcing the nanocapsules washing, which contributes to the removal (at least partially) of the surfactants residues. Thus, implementing safe-by-design strategies in the early stages of research proved to be critical, although further progress is still needed towards the development of truly eco-friendly nanosensors.

Mechanochemical homodisperse of Bi2MoO6 on Zn-Al LDH matrix to form Z-scheme heterojunction with promoted visible-light photocatalytic performance

In this work, a Z-scheme Bi2MoO6/Zn-Al LDH heterojunction photocatalyst with excellent visible light responsiveness was fabricated via a two-step mechanochemical ball-milling process, where amorphous Bi2MoO6 particles were homodispersed upon the surface of lamellar LDH matrix. BPA was selected as the targeted organic contaminant to quantitatively evaluate the photocatalytic capacity of Bi2MoO6/Zn-Al LDH, in which the optimal 30 wt%Bi2MoO6/LDH exhibited a degradation rate of 96% within 300 min, over 9.25 and 18.5 times higher than that of individual pristine Bi2MoO6 and LDH, respectively. The crystal structure, microtopography, interfacial physicochemical interaction, optical and electrochemical properties of as-fabricated hybrids were systematically evaluated, and the DFT theoretical calculation was used to confirm the electronic structural characteristics in the Bi2MoO6/LDH heterojunction. A possible photocatalysis reaction mechanism was interpreted through ESR where the major manner of •O2– proved the Z-scheme electron migration within matched band levels.

Thermal Degradation Kinetics Analysis of Ethylene-Propylene Copolymer and EP-1-Hexene Terpolymer.

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of the ethylene-propylene copolymer and ethylene-propylene-1-hexene terpolymer and its nanocomposite with ZnAL LDH sheets. The 1-hexene dosing during the in-situ process influenced the product yield and immensely affected the thermal stability of the resultant polymer. One milliliter 1-hexene in-situ addition increased the product yield by 170 percent, while the temperature at 10 percent weight loss in TGA was dropped by about 60 °C. While only 0.3 weight percent ZnAL LDH addition in the terpolymer improved the thermal stability by 10 °C. A master plot technique and combined kinetics analysis (CKA) were deployed to access the thermal degradation mechanism of the synthesized polymers.

Reconstruction of the ZnAl Mixed Oxides Into the Layered Double Hydroxide Catalysts Active in the Aldol Condensation of Furfural: The Role of ZnO Particles.

A memory effect is the ability to restore the original, lamellar layered double hydroxide structure. Herein, we have described 1) the changes in the structural and basic properties of ZnAl mixed oxides during their transformation into ZnAl-reconstructed LDHs (RE-LDHs); 2) the extraordinary properties of ZnAl RE-LDHs compared to the original ZnAl LDHs; and 3) the changes of basic properties during the interaction of ZnAl RE-LDHs with atmospheric CO2. Aldol condensation was selected as probe reaction to prove the catalytic potential of ZnAl RE-LDHs. We have described a target method for preparing ZnAl RE-LDHs with a large number of basic sites. ZnAl RE-LDHs possess significantly higher furfural conversion in the aldol condensation of furfural than MOs. The structural, textural, and basic properties of the studied materials were described by temperature-programmed analysis, X-ray diffraction, N2 adsorption, temperature-programmed desorption of CO2, and in-situ diffuse reflectance spectroscopy.

NMR Crystallography Reveals Carbonate Induced Al-Ordering in ZnAl Layered Double Hydroxide.

Layered double hydroxides (LDHs) serve a score of applications in catalysis, drug delivery, and environmental remediation. Smarter crystallography, combining X-ray diffraction and NMR spectroscopy revealed how interplay between carbonate and pH determines the LDH structure and Al ordering in ZnAl LDH. Carbonate intercalated ZnAl LDHs were synthesized at different pH (pH 8.5, pH 10.0, pH 12.5) with a Zn/Al ratio of 2, without subsequent hydrothermal treatment to avoid extensive recrystallisation. In ideal configuration, all Al cations should be part of the LDH and be coordinated with 6 Zn atoms, but NMR revealed two different Al local environments were present in all samples in a ratio dependent on synthesis pH. NMR-crystallography, integrating NMR spectroscopy and X-ray diffraction, succeeded to identify them as Al residing in the highly ordered crystalline phase, next to Al in disordered material. With increasing synthesis pH, crystallinity increased, and the side phase fraction decreased. Using 1 H-13 C, 13 C-27 Al HETCOR NMR in combination with 27 Al MQMAS, 27 Al-DQ-SQ measurements and Rietveld refinement on high-resolution PXRD data, the extreme anion exchange selectivity of these LDHs for CO3 2- over HCO3 - was linked to strict Al and CO3 2- ordering in the crystalline LDH. Even upon equilibration of the LDH in pure NaHCO3 solutions, only CO3 2- was adsorbed by the LDH. This reveals the structure directing role of bivalent cations such as CO3 2- during crystallization of [M2+ 4 M3+ 2 (OH)2 ]2+ [A2- ]1 ⋅yH2 O LDH phases.

Decorated Mn-ferrite nanoparticle@Zn–Al layered double hydroxide@Cellulose@ activated biochar nanocomposite for efficient remediation of methylene blue and mercury (II)

An innovative magnetic nanocomposite was designed and fabricated by the functionalization and support of magnetic Mn-ferrite nanoparticle (MnFe2O4) with layered double hydroxide (Zn-Al LDHs) on cellulose and activated grapes stalks-derived biochar (AGB) (MnFe2O4@Zn-Al LDHs@Cel@AGB), to incorporate active functionalities and fantastic features with the aim to explore its feasibility for removal of harmful cationic species as methylene blue dye (MB) and mercury ions from wastewater. Structural, composition, morphological, surface area, adsorption performance of the fabricated nanocomposite toward both MB and Hg(II) and reusability were also investigated. The results referred that 10 mg ofthe nanocomposite exhibited 97.4% and 84.0 % removal efficiency of 10mgL-1 MB dye and 0.1 mol L-1 Hg(II) at 25 and 30 min contact times, respectively. Adsorption isotherms and kinetics of the two pollutants (MB and Hg(II)) were both governed by the pseudo-second-order equation with possible participation of intraparticle diffusion mechanism.

Enhanced CO2 capture from methane-stream using MII -Al LDH prepared by microwave-assisted urea hydrolysis

In this study, layered double hydroxide [MII-Al LDH (MII = Mg/Zn)] were used as selective CO2 adsorbents from methane stream. It prepared by microwave (MW) assisted homogenous precipitations via urea hydrolysis. The LDH structures and the type of intercalated anions were confirmed by the X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermal analysis (DSC and TGA), and elemental analysis, and scanning and transmission electron microscopes (SEM and TEM) imaging. The results indicated that; the LDH morphology and the intercalated anions (carbonate and urea species) were dependent on MW power, time, and MII type. The predominant urea species were carbamate and isocyanate for Mg-Al LDH and Zn-Al LDH, respectively. The efficiencies of the LDH were tested towards CO2 capture from methane stream using dynamic flow system under atmospheric pressure. Effect of temperature and adsorption/desorption cycles were studied. The best CO2 adsorption capacities obtained at (30 °C) were 3.25, and 2.47 mmol g−1 for Mg-Al-LDH and Zn-Al LDH, respectively. Whereas, those for the calcined LDH (at 550 °C) were 2.96 and 2.29 mmol g−1 for Mg-Al-LDO and Zn-Al LDO, respectively. The results revealed the role of the intercalated urea derived anions type in enhancing the LDH adsorption properties to selectively capture CO2 from methane stream.

Enhanced photocatalytic degradation of organic dyes from aqueous environment using neodymium-doped mesoporous layered double hydroxide

Neodymium-doped Zn–Al layered double hydroxide (Nd/Zn-Al LDH) with excellent photocatalytic activity was prepared by a one-step hydrothermal method. The morphology and physicochemical properties of as-synthesized photocatalysts were well analyzed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), UV-diffuse reflectance spectroscopy (UV-DRS), and Brunauer-Emmett-Teller (BET) surface analysis. Doping Nd3+ into Zn–Al LDH enhances the overall catalytic activity of the nanocomposite, like better electron–hole pair separation, increase in interplanar distance, fast electron transfer, and large surface area. The as-prepared nanocomposite shows excellent degradation of three different dyes under visible light irradiation. The degradation efficiency of these dyes follows the order of Congo red > rose Bengal > fast green. Furthermore, liquid chromatography-mass spectrometry (LC-MS) was employed to propose a possible photocatalytic degradation pathway for Congo Red and Rose Bengal dyes by Nd/Zn–Al LDH. With the help of radical trapping experiments, it is revealed that during the photoexcitation process, the primary reactive intermediates are hydroxyl radicals.

Investigating the role of the morphology of the Zn-Al LDH on the adsorption of humic acid from aqueous solutions.

Flake Zn-Al layered double hydroxides (FLDHs) and microspheres of LDH (MLDHs) were fabricated with a simple hydrothermal method to investigate the role of the morphology of Zn-Al LDH for humic acid (HA) adsorption from synthetic solutions and natural water. The effect of process variables, i.e. contact time, initial concentration of HA, pH, and competitive ions on the adsorption was investigated. HA removal mechanism was also studied. The two adsorbents exhibited different adsorption behaviors for HA in the presence and absence of background ions, which may be highly correlated with the various adsorption mechanisms involved. Comparison of the HA removal capacity of these two adsorbents implies the superior adsorption capability of FLDH for removal of HA from synthetic solutions (9.5 mg/g), while the adsorption capacity of MLDH was higher for natural organic matters present in natural water samples containing co-existing ions (8.9 mg/g). The pseudo-second-order kinetics model and Longmuir isotherm model could adequately interpret the HA adsorption process for the studied adsorbents. Both LDHs exhibited good regeneration and recycling abilities.

Novel Anti-Inflammatory and Wound Healing Controlled Released LDH-Curcumin Nanocomposite Via Intramuscular Implantation, In-Vivo Study

One of the most common problems in wounds is delayed healing and complications such as infection. Therefore, the need for novel materials accelerates the healing of wounds especially abdominal wounds after surgery besides high efficiency and safety is mandatory. The rate of wound healing, anti-inflammatory and biocompatibility of Zn-Al LDH alone and loaded with Curcumin was screened via in-vivo assays through intramuscular implantation in rat abdominal wall with intact peritoneum cavity. The implanted drugs were formed through Curcumin loaded into LDH of Zn-Al with drug release of 56.78 ±1.51% within 24 h. The synthesized nanocomposite was characterized by thermal analysis, X-ray diffraction, Field emission scanning microscopy, high resolution transmission electron microscope and BET surface area. The integrity of blood circulation, inflammatory signs, wound healing rate, capacity of tissue integration, antigenicity and composite biocompatibility, auto fluorescence ability of collagen bundles and the tensile strength of the muscle were assessed histopathologically after 7 and 30 days post-implantation. Excellent wound healing ability was achieved with shortest length between the wound gap edges and higher tensile strength of the muscle. Besides emit florescence very well followed by good healing and tensile muscles strength in Curcumin while very low strength with scar formation in Curcumin-Zn/Al-LDH in both acute and chronic wound. No signs of inflammation in Curcumin & Zn-Al LDH. No vessels obstruction or bleeding observed in both Zn/Al-LDH and Curcumin more than nanocurcumin and control which examined through candling. Good healing & infiltrated immune cells in same groups through histopathological examination. This work supports the anti-inflammatory, wound healing and biocompatibility of both LDH and Curcumin with living matter, increasing their biomedical applications in this era with safety and increasing efficacy with prolonged drug release.

Microwave-assistant synthesis of Tartrazine/layered double hydroxide nano-hybrids with high photoluminescent properties: Influence of microwave energy

The present article provides a fast and simple method to improve the photoluminescence properties of Tartrazine/Zn–Al-LDH and Tartrazine/Mg–Al-LDH. The suggested hybrids have been synthesized by the intercalation of Tartrazine dye into the Zn–Al-LDH and Mg–Al-LDH using a microwave-assisted method. The obtained products were characterized by several techniques such as X-ray diffraction pattern (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric (TGA), and field emission-scanning electron microscopy (FE-SEM). The obtained results confirm the successfully preparation of Tartrazine/Zn–Al-LDH and Tartrazine/Mg–Al-LDH. The photoluminescence spectroscopy (PL) of Tartrazine/Zn–Al-LDH and Tartrazine/Mg–Al-LDH nano-hybrids showed a blue-shift at photoluminescence emission (at the green region) in comparison with pure dye. Also emission intensity improved compared to the pure dye and similar hybrids which preparation using the co-precipitation method (Tartrazine/Zn–Al-LDH-c and Tartrazine/Mg–Al-LDH-c) due to their high crystallinity and uniform nanoplate size. Besides, the results show that, the prepared hybrids exhibited high stability against UV irradiation. Accordingly, the intercalation of dye into the LDHs using the microwave method, not only improved the photoluminescence properties but also increased the photo-stability of the hybrids.

Synergistic photocatalytic-adsorption removal effect of NiFe2O4-Zn-Al mixed metal oxide composite under visible-light irradiation

Today, the photocatalytic process in visible light has become one of the most attractive water treatment fields. We prepared a NiFe2O4-MMO composite with Zn-Al LDH and NiFe2O4 that have good photocatalytic properties in visible light. Structural studies on the samples were performed by X-ray diffraction pattern (XRD) analysis and scanning electron microscopy (FE-SEM). Also, diffusion reflection spectroscopy (DRS) analysis was used to evaluate the optical properties of the samples. In this study, the mechanisms of adsorption and photocatalytic processes were investigated. The kinetics of adsorption and photocatalytic processes was also evaluated. The rate of the photocatalytic process is higher than the rate of the adsorption process, so the surface of the photocatalyst is not saturated. As a result, the adsorption process increases the efficiency of the photocatalytic process, which indicates the synergistic effect of adsorption-photocatalytic to improve the process of removal of organic pollutants from contaminated water.

Long-term dissolution and transformation of ZnO in soils: The roles of soil pH and ZnO particle size

The ongoing use of ZnO nanoparticles (NPs)-associated commercial products results in large release of ZnO NPs into soils and has prompted systematic investigation regarding their fractionation and fate in soils. To date, little information is available about the long-term dissolution and transformation of ZnO NPs in different soils. The distribution and speciation of Zn in two different soils (i.e., Red soil (RS) and Wushantu soil (WS)) treated with either ZnO NPs or bulk ZnO were elucidated by combining soil incubation study with synchrotron-based techniques. Results revealed that ZnO NPs and bulk ZnO were almost dissolved after 1 day, indicating their rapid dissolution upon entering RS (pH-acidic). Rapid dissolution of ZnO NPs was also observed even in WS (pH- circumneutral). The solubilized Zn2+ released from ZnO particles was completely transformed into stable forms (e.g., Zn−Al LDH, Zn−OM, and Zn(OH)2) and Zn-Al LDH was the dominant species in WS after incubation for 360 days. A majority of solubilized Zn2+ released from ZnO particles was also transformed into Zn−Al LDH precipitate in RS. The findings of this study facilitate a better understanding of the fate of ZnO in soils, which could be leveraged for remediation of ZnO-polluted soils.

Poly(methyl methacrylate) intercalated layered double hydroxide film with enhanced alkaline corrosion resistance for aluminum alloy AA6061

The oriented growth of Zn-Al LDH film perpendicular to the surface of AA6061 substrate was confirmed by scanning microscopy image and X-ray diffraction pattern. The LDH film achieved a complete surface coverage on the AA6061 substrate and exhibited strong corrosion resistance in NaOH solution (pH of 13). Furthermore, a preparation protocol for poly(methyl methacrylate) (PMMA)-LDH composite film was demonstrated. LDH film intercalated only with PMMA but not polyurethane demonstrated greatly enhanced alkaline corrosion resistance, showing a more positive corrosion potential and reduced corrosion current by four orders of magnitude in electrochemical polarization spectroscopy. The enhancement in corrosion resistance by PMMA intercalation could be attributed to the increasing compactness in the LDH film and increasing hydrophobicity.

Correlating the Photophysical Properties with the Cure Index of Epoxy Nanocomposite Coatings

Transparency is a crucial factor in developing functional and decorative thin films and coatings, but incorporation of nanoparticles into organic resins for improving their properties quite often makes them opaque. In this work, photophysical properties of epoxy/layered double hydroxide (LDH) nanocomposite coatings were correlated with the dispersion state of LDH in the epoxy resin. The quality of solid epoxy network was assessed in terms of the Cure Index (CI) in relation to the transparency of the films containing 0.1, 0.5, 0.7, 1.0, and 3.0 wt% Mg–Al–LDH and Zn–Al–LDHs. At high loadings, direct transmittance (YDirect) decreased, while the light scattering in the coatings improved with respect to the neat epoxy. The highest Zn–Al–LDH loading (3.0 wt%) slightly deteriorated the transparency (YDirect = 93.3), but it was still higher than that of epoxy nanocomposite containing 0.5 wt% Mg–Al–LDH (YDirect = 89.8). A Good label was assigned to the epoxy nanocomposites containing up to 1.0 wt% Zn–Al–LDH, while epoxy/Mg–Al–LDH nanocomposites were Poor in terms of the CI labeling when Mg–Al–LDH content was more than 0.1 wt%. An increase of about 28 °C in the Tg value after the addition of 0.1 wt% Zn–Al–LDH indicated that Zn–Al–LDH can make strong the interaction between the epoxy matrix and nanoplatelets. However, decrease in the Tg of the epoxy/Mg–Al–LDH nanocomposites was a signature of the weak interactions between the Mg–Al–LDH nanoplatelets ‎and epoxy matrix due to inappropriate dispersion. In general, it was revealed for the first time that the CI enables correlating the chemical crosslinking with the photophysical properties of the epoxy/LDH nanocomposites.

Removal of strontium by in situ electrochemical synthesis of Zn–Al LDHs using a bidirectional pulse method

The Sr2+ removal rate is 99.26%, and the energy consumption of the reaction process is 5.01 kW h m−3.

ZnAl–LDH-induced electroactive β-phase and controlled dielectrics of PVDF for a high-performance triboelectric nanogenerator for humidity and pressure sensing applications

An eco-friendly ZnAl–LDH–PVDF composite material is demonstrated for realizing high-performance TENG via control of dielectric properties and β-phase of PVDF for simultaneous sensing of pressure and humidity in self-powered way.