Zn-Al Layered Double Hydroxides Research Articles

The composite of ZnSn(OH)6 and Zn–Al layered double hydroxides used as negative material for zinc–nickel alkaline batteries

A series of Zn–Al layered double hydroxides (LDHs) and ZnSn(OH)6 composites were successfully synthesized by hydrothermal method. The characteristic diffraction peaks of composites analyzed by X-ray diffraction (XRD) display that Zn–Al LDHs have been coupled with ZnSn(OH)6, among which the composite containing 10% ZnSn(OH)6 shows the best crystallinity. Besides, scanning electron microscopy (SEM) was conducted to observe the crystal morphologies. The electrodes were carried out by electrochemical measurements such as cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), and cycling performance. The results suggest that the discharge specific capacity of composite containing 10% ZnSn(OH)6 is basically kept at 354 mAh g−1 with a capacity retention rate about 98.3% after 800 cycles. Meanwhile, the CV measurement manifests that this material has the smallest redox peak potential difference (0.31 V) than that of others. And the electrode reaction of composite containing 10% ZnSn(OH)6 occurs easily because the EIS test implies that its charge transfer resistance has been declined by 11.57 Ω cm2, accompanied by the ohmic resistance decreasing by 0.48 Ω cm2. The findings mentioned above can be attributed to the high electron mobility and electrical conductivity of ZnSn(OH)6. All the results show that the electrode of LDHs with 10% ZnSn(OH)6 has quite outstanding electrochemical performances when used as the negative material for zinc–nickel alkaline batteries.

Pyrolysis kinetics of ZnAl LDHs and its calcined products for H2S removal

This paper reports the calcined products of the hydrotalcite-based ZnAl-layered double hydroxides (LDHs) for H2S removal. The thermal behavior of ZnAl LDHs was investigated by thermogravimetry–differential scanning calorimetry (TG–DSC) and thermogravimetry–mass spectrum (TG–MS). The activation energies were estimated by the Kissinger method and Flynn–Wall–Ozawa (FWO) method. To clarify the physical and chemical transformation during pyrolysis, the initial sample (ZnAl LDHs) and its pyrolysis products calcined at several different temperatures were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope. The results show that there are two major stages of the thermal decomposition of ZnAl LDHs: Stage I with an intense endothermic peak at 196 °C in DSC curve is ascribed to the removal of water (both the physically absorbed water and the interlayer water) and a small loss of CO2. Stage II with a broad endothermic peak is due to the decomposition of the carbonate anions and a little part of dehydroxylation from brucite-like sheets. The activation energies calculated by the Kissinger and FWO method are 110.7 and 112.8 kJ mol−1 of stage I and 94.3 and 98.1 kJ mol−1 of stage II, respectively.

Outerly functionalized and non-functionalized boron clusters intercalated into layered hydroxides with different modes of binding: materials for superacid storage.

Two binary boron hydrides (NH4)2B10H10 and Na2B12H12 and mono- and dicarboxy p- and m-carboranes (namely, 1-(COOH)-closo-1,7-C2B10H11, 1,12-(COOH)2-closo-1,12-C2B10H10 and 1,7-(COOH)2-closo-1,7-C2B10H10) were intercalated into ZnAl-layered double hydroxides (ZnAl-LDH) and into Zn5(OH)8(NO3)2·2H2O. The formed compounds were characterized using elemental analysis, thermogravimetry analysis, X-ray powder diffraction, infrared spectroscopy and solid state NMR. All the intercalated boron compounds are present in the interlayer space of the layered hosts as anions. It is presumed that in the case of B10H102-, B12H122- and 1,12-(COO)2-closo-1,12-C2B10H102-, the guest molecules form a monolayer, whereas in the case of 1-(COO)-closo-1,7-C2B10H111- and 1,7-(COO)2-closo-1,7-C2B10H102- a bilayer arrangement is more probable. In the case of 1,7-(COO)2-closo-1,7-C2B10H102-, the guest molecules are strongly interdigitated resulting in lowering of the interlayer distance. Two different modes of binding were found. Whereas the carboxylate derivatives of p- and m-carboranes are bonded through classical hydrogen bonds, the corresponding parent borane anions interact with the host structures by mainly dihydrogen bonding. In effect, both kinds of hydrogen bonding are mainly of an electrostatic nature. The dihydrogen bond is detected, e.g. in crystal engineering, and represents a driving force for interactions of boranes with biomolecules. Since the latter dicarboxylic acids were found to be superacids, their interactions with the host structures should be stronger than in the case of the benzoic and terephthalic acid intercalates.

Improved Visible-Light-Induced Photocatalytic Performance of ZnAl Layered Double Hydroxide by Incorporation of Ni2.

NiZnAl layered double hydroxides (LDH) with Ni/Zn/Al ratios ranging from 0.1/2/1 to 1/2/1 were papered by coprecipitation. The prepared samples were characterized by multiple techniques including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse-reflectance spectroscopy (UV-vis DRS). The incorporation of Ni2+ into the brucite sheets preserves the layered structure of ZnAl LDH. The doped Ni2+ serves as the photogenerated charges separator and improves the visible light photocatalytic activity of ZnAl LDH at a reasonable content. A degradation mechanism based on the hydroxyl radical as the active species was proposed.

Mg-Al and Zn-Al Layered Double Hydroxides Promote Dynamic Expression of Marker Genes in Osteogenic Differentiation by Modulating Mitogen-Activated Protein Kinases.

The effect of LDH samples comprised of chloride anions intercalated between positive layers of magnesium/aluminum (Mg-Al LDH) or zinc/aluminum (Zn-Al LDH) chemical composition on pre-osteoblast performance is investigated. Non-cytotoxic concentrations of both LDHs modulated pre-osteoblast adhesion by triggering cytoskeleton rearrangement dependent on recruiting of Cofilin, which is modulated by the inhibition of the Protein Phosphatase 2A (PP2A), culminating in osteoblast differentiation with a significant increase of osteogenic marker genes. The alkaline phosphatase (ALP) and bone sialoprotein (BSP) are significantly up-modulated by both LDHs; however, Mg-Al LDH nanomaterial promoted even more significance than both experimental controls, while the phosphorylations of mitogen-activated protein kinase (MAPKs)- extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinase (JNK) significantly increased. MAPK signaling is necessary to activate Runt-related transcription factor 2 (RUNX2) gene. Concomitantly, it is also investigated whether challenged osteoblasts are able to modulate osteoclastogenesis by investigating both osteoprotegerin (OPG) and Receptor activator of nuclear factor kappa-ligand (RANKL) in this model; a dynamic reprogramming of both these genes is found, suggesting LDHs in modulating osteoclastogenesis. These results suggest that LDHs interfere in bone remodeling, and they can be considered as nanomaterials in graft-based bone healing or drug-delivery materials for bone disorders.

Comparison of adsorption and desorption of phosphate on synthesized Zn-Al LDH by two methods in a simulated soil solution

Abstract Zinc aluminum layered double hydroxides (LDH) with Zn/Al molar ratios of 2 and 3 were synthesized by general (Zn 2G -Al, Zn 3G -Al) and modified (Zn 2M -Al, Zn 3M -Al) urea hydrolysis methods. The effects of time, pH, selectivity and initial phosphorous concentration were investigated on phosphate uptake by synthesized LDH in a simulated soil solution. Moreover, phosphate desorption from studied LDH was evaluated. Based on the results, nitrate containing Zn-Al LDH were synthesized by both methods. However, the presence of carbonate ion in the interlayer space of Zn 3G -Al was recorded. The kinetics experiments indicated that the pseudo-second order model well described phosphate uptake on all LDH. The lowest uptake (1.09 mmol g − 1 ) was observed for Zn 3G -Al likely due to Zn/Al molar ratio, the presence of carbonate in the interlayer space and incomplete phosphate intercalation mechanism. Phosphate adsorption isotherms of LDH were in agreement with Freundlich model. Although phosphate uptake decreased in the presence of other anions, the highest selectivity especially in the pure nitrate containing LDH were measured for phosphate anion. Phosphate uptake declined with increasing the pH from 6 to 8. The amounts of phosphate desorption from prepared LDH were between 23.2 and 36.3% suggesting that synthesized LDH may have potential to be used as a slow release phosphate fertilizer in soils.

Photocatalytic efficiency of ZnAl-layered double hydroxide on degradation of a cationic dye under UV and solar radiation

UV and solar radiation photocatalytic degradation of basic dye Rhodamine B (RhB) using ZnAl-layered double hydroxide photocatalyst was investigated. ZnAl-layered double hydroxide (ZA4-HT) with a molar ratio of 4:1 was synthesized from zinc and aluminum salts by co-precipitation methods, followed by heat treatment at 500 °C (CZA4). Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) revealed that after heat treatment of ZA4-HT, the pristine structure collapsed resulting in ZnO particles and ZnAl2O4 spinel. The discoloration rate of RhB was lower than 8% through direct photolysis. The calcined ZA4-HT showed high photocatalytic efficiency with a discoloration rate of about 100% after 90 min exposure time to UV or sunlight radiation. The optimal catalyst loading was found to be 1 g/L and the discoloration time increased with the dye concentration. The photodiscoloration and the photodegradation kinetics data were described by pseudo-first-order and Langmuir–Hinshelwood models. The reusability study of the calcined material showed a stable efficiency after four successive uses.

Synthesising methods of layered double hydroxides and its use in the fabrication of dye Sensitised solar cell (DSSC): A short review

The layered double hydroxides (LDH) which are anionic clay substances comprising of stacked cationic layers and interlayer anions. The cationic sheets contain octahedral structure consisting the divalent and trivalent ions in the center and hydroxyl bunches in the corners, gathered by three bonding with the neighbouring octahedra on every side of the layer. The ratio between the quantity of cations and OH− ions is 2:1, so a positive charge shows up on the layer because of the presence of trivalent cations. The interlayer space gives the compensation anions and water molecules, assuring a balanced out layered structure. The LDH materials were successfully synthesised from magnesium, aluminium, zinc and chromium chloride salts utilizing the co-precipitation technique. A Zn-Al LDH was researched as a potential sorbent material. This article reviews the recent advances in the preparation and intercalation of layered double hydroxides and its application in the fabrication of Dye Sensitized Solar Cell (DSSC).

Phenol adsorption using Aliquat 336 functionalized Zn-Al layered double hydroxide

Abstract Phenolic compounds, which are important substances in industry, are mainly derived from coal liquefaction oil, coal tar, and petroleum, and also from biomass via pyrolysis. Phenol is considered a pollutant in the environment due to its toxicity and carcinogenic effect, therefore the removal of phenols from waters before discharge is a necessary requirement. It was found that phenol compounds could be successfully separate from various samples using extraction with ionic liquids (ILs). Several studies were done on phenol removal using layered double hydroxides (LDH) due to their efficiency to adsorb and/or intercalate anionic compounds. The present paper reports the studies regarding the phenol removal using ionic liquid functionalized Zn4Al-LDH. In this way are combined the advantageous of the IL with the properties of the LDH. As IL was used Aliquat 336 - methyl mixed tri-alkyl ammonium chloride. Two methods for the functionalization of the Zn4Al LDH with IL were studied: the impregnation of the IL onto the Zn-Al LDH using the ultrasonication method and the co-precipitation. From the extensive characterization of the obtained adsorbent through SEM and EDX, RX, FTIR, BET and TGA analysis was put in evidence that the functionalization of the Zn4Al-LDH with the Aliquat 336 was realized. Equilibrium, and kinetic studies were applied in order to determine the efficiency of the studied adsorbents in the removal process of phenol from aqueous solutions. Both, the LDH and the studied IL, contribute to the increasing of the adsorption capacity of the obtained adsorbent in the removal process of phenol from aqueous solutions due to their synergic effect. Comparing the maximum adsorption capacities develop by the studied adsorbent with the adsorption capacities developed by other similar adsorbent material, reported in literature, it can be conclude that Zn4Al layered double hydroxide functionalized with Aliquat 336 is an efficient adsorbent. The maximum adsorption capacities developed by the studied adsorbents are in the following order: IL-Zn4Al > Zn4Al-IL > Zn4Al.

Enhancement of active anticorrosion via Ce-doped Zn-Al layered double hydroxides embedded in sol-gel coatings on aluminum alloy

Ce-doped Zn-Al layered double hydroxide (LDH) nanocontainer was synthesized by a co-precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods were used for the characterization of the LDH nanocontainer. The anticorrosion activity of the LDH powders embedded in a hybrid sol-gel coating on aluminum alloy 2024 was investigated by electrochemical impendence spectroscopy (EIS). The results showed that Ce (III) ions were successfully incorporated into LDHs layers. The sol-gel coating modified with Ce-doped Zn-Al LDHs exhibited higher anticorrosion behavior compared with both unmodified and Ce-undoped LDHs containing coatings, which proved the applicability of Ce-doped LDHs in delaying coating degradation and their potential application as nanocontainers of corrosion inhibitors in self-healing coatings.

Transparent nanocomposite coatings based on epoxy and layered double hydroxide: Nonisothermal cure kinetics and viscoelastic behavior assessments

Abstract Layered double hydroxide (LDH) has a particular place in clay family because of its flame retardant action. The nanoplatelet-like structure of LDH makes possible development of polymer composites with cationic or anionic nature structures in which macromolecules are positioned in between nanoplatelet galleries. In this work, neat epoxy and its transparent nanocomposite coatings with sodium dodecylbenzene sulfonate (SDBS)-modified LDHs; Mg-Al and Zn-Al LDHs, were prepared and their cure kinetics and viscoelastic behavior were tracked through nonisothermal calorimetric and dynamic mechanical analyses. The higher progression of crosslinking in the epoxy network was observed for epoxy/Zn-Al LDH nanocomposites, while activation energy of cure reaction took a higher value for Mg-Al LDH-incorporated systems. Moreover, epoxy/Mg-Al LDH system revealed higher value of storage modulus and glass transition temperature thanks to larger galleries of Mg-Al nanoplatelets. Network formation in the presence of SDBS-modified Zn-Al LDH nanoplatelets was facilitated due to the action of Zn metal as an adduct with a lone-pair of oxygen atom of epoxy leading to an enhanced epoxy ring-opening. Viscoelastic behavior of transparent coatings containing Zn-Al LDH and Mg-Al LDH was studied through temperature-sweep test at various frequencies to compare the results of calorimetric and thermo-mechanical analyses.

Investigation of the dye-sensitized solar cell designed by a series of mixed metal oxides based on ZnAl-layered double hydroxide

In this paper, the anode materials for dye-sensitized solar cell (DSSC) were prepared by a facile calcination method using the ZnAl-layered double hydroxide (LDH) as a precursor. The ZnAl-LDHs with different molar ratios (Zn:Al = 2, 4, 6, 8) were prepared by the urea method and the mixed metal oxides (MMO) were prepared by calcining the LDHs at 500 °C. A series of cells were assembled by the corresponding MMOs and different dyes (N3 and N719). The basic parameters were investigated by X-ray diffraction, scanning electron microscope, thermogravimetric and differential thermal analysis, nitrogen sorption analysis and UV–Vis absorption spectrum. The photovoltaic performance of DSSCs was measured by electrochemical method. It could be seen that ZnAl molar ratios and different dyes had great influence on the efficiency of DSSC. The efficiency improved explicitly with increasing ZnAl molar ratio and the DSSC made of N3 showed better efficiency than that of N719. The best efficiency of N3 conditions reached 0.55% when the ratio of ZnAl-LDH precursor was 8:1.

Synthesis, characterization and catalytic activity of tungstocobaltate-pillared ZnAl-layered double hydroxide

Tungstocobalate (Co III W 12 O 40 5- ) intercalated ZnAl-layered double hydroxide (ZnAl-CoW 12 ) was prepared via rehydration of calcined ZnAl-LDH under N 2 atmosphere. Characterization by chemical analysis together with powder XRD, FT-IR, TG-DTA and UV-VIS DRS provided evidence of intercalation of Co III W 12 O 40 5- (58 wt. %) in the interlayer of LDH. The catalytic activity of ZnAl-CoW 12 was evaluated for hydrogen peroxide mediated decolourisarion of methyl orange and oxidation of benzaldehyde to benzoic acid under varying reaction conditions. ZnAl-CoW 12 was found effective for both the reactions and stable under the experimental conditions for repetitive use without any noticeable decrease in activity.

Comparative Evaluation of Synthetic Routes and Antibacterial/Antifungal Properties of Zn–Al Layered Double Hydroxides Containing Benzoate Anion

Abstract With variation in synthetic routes, properties of the as-obtained products also vary. Three synthetic routes are opted such as coprecipitation (CP), ion exchange (IE), and rehydration (RH) to form an antibacterial/antifungal composite of Zn–Al layered double hydroxide with benzoate (BZ) anion in the interlayer space. X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectrum, and thermogravimetric analyses are used to characterize the samples. In case of composite obtained by CP route, the molecular arrangement of the BZ anion is bilayer with both the molecules are arranged along their y-axis. Similarly, in case of IE route, the arrangement is also bilayer but the molecules are arranged along the y-axis of one molecule and along the x-axis of another. In the RH route, the arrangement is monolayer. The three novel nanocomposites showed different performance in terms of liberation factor and antibacterial activity toward both Gram-positive (Staphylococcus au...

Orientation of Organic Anions in Zn-Al Layered Double Hydroxides with Enhanced Antibacterial Property

Abstract Layered double hydroxide (LDH)-based nanocomposites, fabricated by interacting LDHs with organic anions, are an emerging and active area in healthcare, environmental remediation, catalysis, and storage. Ciprofloxacin, sulfanilamide, and oxazolidinone, which exhibit antibacterial activity, are successfully intercalated in Zn-Al LDHs through anion exchange method. Synthesis of the precursor was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM). Intercalation was successfully evaluated from XRD data. It has been found that both the nature and position of aromatic ring substituents effect the value of the basal distance and the host–guest hydrogen bond network. Evidence on interactions of intercalated anions with the inorganic layer has been confirmed from Fourier transform infrared absorption spectroscopy. Morphology of composites was studied by field emission scanning electron microscopy, and thermal stability was studied by thermogravimetry and differential thermal analy...

Photo-induced properties of photocatalysts: A study on the modified structural, optical and textural properties of TiO2–ZnAl layered double hydroxide based materials

Heterogeneous photocatalytic oxidation technologies, based on the free-radical reaction initiated by a light irradiation of photocatalyst surface, are promising methods for water and air purification, being one of overwhelming concerns in the scientific community regarding the challenges of exponential environmental pollution increase. Mixed oxides derived from ZnAl containing layered double hydroxides (LDH) without or with doping agents (Fe, Sn and Ti) have been recently implemented as efficient and environmental-friendly materials in the photodegradation process of organic compounds in aqueous media. Considering both, the progress in the synthesis of photoactive LDH and evident drawbacks of classical methods, the study is focused on the development of an innovative, simple and cost effective synthesis method of TiO2 containing ZnAl LDH based photocatalysts with improved overall photocatalytic and antibacterial performances in water purification processes. In order to elucidate the relationship between the functional material properties developed in TiO2 impregnation process and photo-induced catalytic and antibacterial activity, comprehensive studies encompassed structural (XRD), textural (low temperature nitrogen adsorption), electronic properties (diffuse reflectance spectroscopy) and morphology (SEM) of developed TiO2-ZnAl LDH based materials, as well as the XPS study of the most active photocatalysts, in correlation to photo-induced catalytic activity (Methylene Blue degradation) and antibacterial activity (Gram-negative E. coli and Gram-positive bacterium S. aureus as indicator strains). The results confirmed that innovative impregnation method using base solution enables favorable interactions among active phases promoting the synergetic effect and complex interactions between the TiO2 (3 mas%) and ZnAl mixed oxides, enhancing photocatalytic activity to the level almost equal to TiO2, simultaneously improving the overall antibacterial performance.

Metallophthalocyanine intercalated layered double hydroxides as an efficient catalyst for the selective epoxidation of olefin with oxygen

Varied metallophthalocyanine intercalated layered double hydroxides (LDHs) as bifunctional hybrid catalysts for selective epoxidation have been prepared and characterized. Systematic characterizations suggested the successful intercalation of the metallophthalocyanines into the interlayer of ZnAl LDHs. The synthesized hybrid exhibited excellent catalytic activity in the selective epoxidation of various olefins through O2/isobutaldehyde system. The basicity of the hybrid benefits to the selectivity of epoxide, and the bifunctional roles of the catalyst in the reaction have been discussed and verified by a series of controlled experiments. On the basis of obtained results, a probable mechanism of the epoxidation by the hybrid has been proposed and detailedly investigated. Under the catalysis of metallophthalocyanines intercalated LDHs in the presence of O2/isobutaldehyde, the production of epoxide undergoes two reaction paths. And two types of intermediates, namely acylperoxy radical and peroxyacid, are formed in the reaction, and the former is predominant.

In-situ growth of ZIF-8 on layered double hydroxide: Effect of Zn/Al molar ratios on their structural, morphological and adsorption properties

In-situ growth of Zeolite imidazolate frameworks (ZIFs) on layered double hydroxides (LDHs) to form porous composites is a promising and challenging strategy to develop materials for separation application. Herein, the Zn-Al LDH with different Zn/Al molar ratios was prepared and used as matrix for the growth of ZIF-8 on its surface. The resulting composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physisorption, thermogravimetric (TG), scanning electron microscope (SEM) and elemental analysis followed by testing for AsV removal from aqueous solution. Results showed that ZIF-8 could form on the surface of LDH with different Zn/Al molar ratios. At low Zn/Al molar ratios, the morphology and surface area of the ZIF/LDH composites and the content of ZIF-8 in the composites were little affected by the Zn/Al molar ratio. With increasing Zn/Al molar ratio, ZIF-8/LDH exhibited a lower surface area, which resulted from reduced content of ZIF-8 caused by impurities generated in the LDH matrix. All ZIF-8/LDH samples showed high AsV adsorption capacity, which was significantly higher than that of pure LDH or ZIF-8.

Visible light-emission from Eu-doped ZnAl layered-double hydroxide

Abstract We report on the evolution of the emission and chemical properties of Eu-doped ZnAl-Layered double hydroxide (LDH) with variation of Eu doping concentration during the hydrothermal growth. With increasing Eu source concentration, the morphologies of the ZnAl-LDHs became denser and more closely packed while maintaining the thickness of each plate. As the Eu source concentration increased to 10 wt%, specific emission from the doped Eu 3+ ions was enhanced in the photoluminescence spectra. However, the peak intensity decreased when the concentration increased further to 20 and 30 wt%. X-ray photoelectron spectroscopy results showed an abnormal increase of the Eu 2+ /Eu 3+ ratio in the LDHs with increasing Eu source concentration, which suppressed the emission from the Eu 3+ electronic transitions.

Synthesis and characterization of Zn-Al layered double hydroxide nanofluid and its application as a coolant in metal quenching

The current study comprises of the synthesis and characterization of Zn-Al layered double hydroxide (LDH) nanofluid for use as a potential coolant in the steel industry. Coprecipitation method was used in the preparation of Zn-Al LDH nanoparticles by using the nitrate salts of Zn, Al and Na, in the ratio of 2:1:2. The nanofluids were characterized based on their particle size, stability, surface tension, thermal conductivity and viscosity. TEM analysis revealed that the nanoparticles were needle-shaped with an average particle size of 45.61nm and aspect ratio of 7.3. Different concentrations of the nanofluid, from 40ppm to 240ppm, were used to analyze the effect of particle concentration on the enhancement in thermal conductivity and viscosity. Stability analysis of the nanofluid exhibited good results, even without any stabilizer. An optimum cooling rate of 125°C/s was obtained for a nanofluid concentration of 160ppm, which is 1.29 times when compared to water.