Zn-Al Hydrotalcite Research Articles

Zn–Al Hydrotalcites and Magnetic Zn–Al Hydrotalcites for Efficient Phosphate Remediation and Recovery

Zn–Al Hydrotalcites and Magnetic Zn–Al Hydrotalcites for Efficient Phosphate Remediation and Recovery

ZnAl/ZnSn(OH) composite photocatalyst for emerging contaminants degradation in water

Layered double hydroxides (LDH) are a versatile group of lamellar inorganic solids with a brucite-like structure similar to hydrotalcite that has undergone multiple improvements to be applied in various fields such as carbon dioxide sequestration, catalysis, drug delivery, energy conversion, and storage, as well as environmental remediation. It is then that this material becomes interesting for its application in water treatment since it has various practical features, e.g. tunable structure, excellent thermal stability, memory effect, high specific surface, high dispersion and regenerative viability. By taking advantage of this versatility, in this research work, the synthesis and characterization of ZnAl hydrotalcite modified with Sn through the coprecipitation method is reported. The presence of hydrotalcite ZnAl, and Zinc hydroxystannate phases were observed in the X-ray diffraction spectra. In the same way, it was possible to observe through the SEM micrographs the morphology associated with the union of both phases; i.e. lamellar and microcubic. In the bandgap energy measurement, the shift of the hydrotalcite value is observed as well as the appearance of another signal of zinc hydroxystannate species. The obtained materials were evaluated for the photocatalytic degradation of acetaminophen to 20 ppm under UV light. ZnAl/ZnSn(OH)6 composite showed better efficiency in the paracetamol degradation under UV light. Additionally, studies of the variation of ZnAl/ZnSn(OH)6 ratio and pH values of the solution were carried out, achieving photodegradation efficiency > 95 %, after 60 min of irradiation, using 0.15 g of ZnAl/ZnSn(OH)6 photocatalyst at pH= 6. The reusability was evaluated by testing the material in photodegradation cycles.

Remarkable adsorption capacity of Cu2+-doped ZnAl layered double hydroxides and the calcined materials toward phosphate

In this study, Cu2+ was doped into ZnAl hydrotalcite by one-step urea homogeneous hydrolysis to produce ZnAlCu ternary hydrotalcite (ZnAlCu-1%-LDH). After that, it was roasted to obtain ZnAlCu layered trimetallic oxide (ZnAlCu-1%-LDO). The Jahn-Teller effect of Cu2+ is able to distort the ZnAlCu, thus increasing the hydrotalcite layer spacing and specific surface area. The influence of Cu2+ doping on phosphate adsorption was investigated, and adsorption mechanism was also analyzed. XRD proved that Cu2+ doping increased the interlayer spacing of adsorbent. The optimum copper doping amount of ZnAlCu-1%-LDO was 1% of the total metal molarity. The ZnAlCu-1%-LDO obtained the phosphate adsorption capacity of 199.28 mg P/g, which was 4.6 and 2.9 times higher than that of ZnAl-LDH and ZnAlCu-1%-LDH (phosphate concentration of 200 mg P/L, adsorbent dosage of 0.4 g/L), respectively. Experimental characterizations revealed that the phosphate adsorption mechanisms of ZnAlCu-1%-LDO were memory effect, electrostatic attraction, ligand exchange and surface precipitation. In addition, the phosphate removal efficiency of ZnAlCu-1%-LDO in the actual wastewater (3.43 mg P/L initial concentration) was also investigated, and the residual concentration after adsorption was 0.0664 mg P/L, which reached the A-level standard of phosphate effluent in China (0.5 mg P/L). The experiment provided a universal solution for other layered double hydroxides (LDHs) to improve their phosphate adsorption performance.

Chemical transesterification of soybean oil as a feedstock for stable biodiesel and biolubricant production by using Zn Al hydrotalcites as a catalyst and perform tribological assessment

Chemical transesterification of soybean oil as a feedstock for stable biodiesel and biolubricant production by using Zn Al hydrotalcites as a catalyst and perform tribological assessment

Role of Al and Mg alloying elements on corrosion behavior of zinc alloy‐coated steel substrates in 0.1 M NaCl solution

AbstractThe corrosion behavior and corrosion products of three zinc alloy‐coated steel substrates with different Al and Mg contents such as hot‐dip galvanized steel (HDG), Zn–Al‐coated steel (ZA), and Zn–Al–Mg‐coated steel (ZM) substrates were investigated during 168 h of immersion in 0.1 M NaCl solution. The characteristics and morphology of corrosion products on all the substrates formed during exposure to electrolyte solution were observed by X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy/energy‐dispersive X‐ray spectroscopy. Their electrochemical behavior was investigated by open‐circuit potential, polarization curves, and electrochemical impedance spectroscopy. The addition of Al and Mg alloying elements affected the corrosion mechanism as well as the anticorrosion properties. The main crystalline corrosion products on the HDG surface were simonkolleite and zincite, while the ZnAl hydrotalcite was identified as the main corrosion product on ZA and ZM surfaces. The corrosion resistance of ZA and ZM substrates was improved compared to the HDG substrate due to the enhanced adhesion of the corrosion product layer.

Study of the formation and anti-corrosion properties of Zn[sbnd]Al hydrotalcite conversion films grown “in situ” on different zinc alloys coated steel

The Zn-Al-CO32− hydrotalcite (HT) conversion film was developed on hot-dip galvanized steel (HDG), ZnAl coated steel (ZA), and Zn-Al-Mg coated steel (ZAM) substrates by “in situ” growth process for Al3+/Zn2+ ratio of 5/3 at pH 12. The characteristics of all the ZnAl HT film-coated samples before and after exposure to 0.1 M NaCl for 24 h were investigated by means of Fourier-transform infrared (FT-IR), X-Ray Diffraction (XRD), electron microscopy/energy dispersive X-ray spectroscopy SEM/EDS, and X-ray photoelectron spectroscopy (XPS). The corrosion properties of all the samples were studied by open circuit potential measurements (OCP), polarization curves, and electrochemical impedance spectroscopy (EIS). The electrochemical tests indicated that the HT film-coated can significantly restrain the corrosion of the HDG, ZA, and ZAM substrates but this efficiency was depending on the alloying compounds of the sacrificial layer. The inhibitive effect of HT film-coated on all the corrosion substrates was discussed in detail.

Enhanced Photocatalytic Degradation of Rhodamine-B under Led Light Using CuZnAl Hydrotalcite Synthesized by Co-Precipitation Technique

The co-precipitation method was employed to synthesize a set of ZnAl hydrotalcite materials modified by Cu2+. The synthesized materials have a similar lamellar structure to that of hydrotalcite. The distance between layers is in the range of 7.73–8.56 Å. The network parameters a and c ranged from 3.058 to 3.074 Å and from 23.01 to 24.44, respectively. According to the IUPAC classification, the composites possess a mesoporous structure which belongs to class IV, type H 3. Particularly, the absorption edge shifts strongly to the visible light region when increasing the molar ratio of Cu2+ in the samples from 0 to 3.5. The photocatalytic activity of the synthetic materials was evaluated through the degradation efficiency of rhodamine-B (Rh-B) in the water and colorants in textile wastewater. The present study was the first to synthesize a material sample that contains a molar ratio of Cu2+ in the range of 2.5–3.5 and has high catalytic activities. They were able to degrade Rh-B at a high concentration (100 ppm) with a conversion rate of approximately 90% after 240 min of irradiation using a 30 W LED light. The catalytic activity of the composites depends on the molar ratio of modified Cu2+, the value of environmental pH, the H2O2 concentration and the irradiation time.

Synthesis of Biohybrid Material Based on Magnetic Zn–Al Hydrotalcite and Cellulase: Structural and Enzymatic Activity Characterizations

Synthesis of Biohybrid Material Based on Magnetic Zn–Al Hydrotalcite and Cellulase: Structural and Enzymatic Activity Characterizations

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.

Modification of Zn-Al Hydrotalcite as Potential Photocatalyst

Modification of Zn-Al Hydrotalcite as Potential Photocatalyst

A comparative study of the structure and corrosion resistance of ZnAl hydrotalcite conversion layers at different Al3+/Zn2+ ratios on electrogalvanized steel

The dissimilarities of the composition, crystal structure, and corrosion resistance of ZnAl hydrotalcite (ZnAl-HT) conversion films grown “in situ” on electrogalvanized (EG) steel substrate were investigated for different Al3+/Zn2+ ratios at pH 12. The corrosion behavior of all conversion films in 0.1 M NaCl was compared through electrochemical techniques. The composition, morphology, structure, and thickness of conversion films with different Al3+/Zn2+ ratios were characterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), and electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and X-ray diffraction (XRD). The polarization curves indicated that the ZnAl-HT films provided anodic inhibition for EG steel and the inhibition efficiency of the ZnAl-HT conversion films increases sharply with decreasing the Al3+/Zn2+ ratios from 5/1 to 5/3, while, for the 5/4 and 5/5 ratios, the corrosion resistance of ZnAl-HT conversion films showed a downward trend after two immersion hours. However, the corrosion behavior of HT conversion films with the Al3+/Zn2+ ratios from 5/3 to 5/5 remained stable for a longer immersion time. The protection performance of the ZnAl-HT films can be attributed to the barrier effects, ion-exchange competitive adsorption of chloride ions, and protective deposition of ZnO on the EG steel surface.

ZnAl hydrotalcites modified with nanocomposites nZVI–PAA for environmental remediation

Diffraction patterns of polyacrylic acid (PAA) encapsulated-(Fe)-modified ZnAl hydrotalcite (ZnAlH) showed the integration of Fe in the H lattice, resulting in a hybrid nanocomposite (Fe-PAA-ZnAlH), which was mainly verified with the characteristic shift in the 59–63° (2θ) region of the ZnAlH (110) reflection plane. The rise in the unit cell parameters (c and a ) as the Fe % incremented, denoted incorporation of Fe in the ZnAlH red. Nonetheless, changes in the immobilizer molecular weight (PAA MW) from 1250 kDa to 5.1 kDa did not cause a difference in the distance between layers (c parameter) but in the cation-cation separation ( a parameter), which meant that the nanoparticle was not located between layers, but in the lattice. The resulting band gap energies of the calcined hybrid nanocomposites were among 1.07–1.21 eV, which is an additional support of Fe +3 integration, suggesting insertion of Fe +3 3d orbitals between the valence and the conduction band of ZnO. Furthermore, nZVI were prepared through a pre-agglomeration reduction method, where COOH-groups were bound to metal cations. Initially, aqueous Fe +2 was bound to PAA [Fe +2 -PAA], then reduced to obtain enclosed hybrid (nZVI-PAA). Less stability and more aggregation were observed with the lower molecular weight PAA. Additionally, PAA dissociation caused by pH changes affected the clustering of the nZVI particles. At higher MW, the hydrodynamic diameter and size distribution become smaller and tighter, respectively, allowing a more monodispersed population with sphere shape and organized in core–shell beads chains.

Insights into the degradation mechanism of perfluorooctanoic acid under visible-light irradiation through fabricating flower-shaped Bi5O7I/ZnO n-n heterojunction microspheres

• Bi 5 O 7 I/ZnO n-n heterojunction was facilely prepared by in-situ phase transition. • n-n Bi 5 O 7 I/ZnO efficiently degraded PFOA under visible light irradiation. • The experimental mechanism was verified by DFT calculation. • h + were the active substance responsible for PFOA degradation. Perfluorooctanoic acid (PFOA), which is an emerging contaminant, has received extensive attention in recent times due to its high toxicity and environmental risk. In this study, BiOI supported on Zn-Al hydrotalcite (BOI 0.04 -BHZA) was calcined at 400 ℃ to obtain flower-shaped Bi 5 O 7 I/ZnO n-n heterojunction microspheres for the photocatalytic degradation of PFOA under visible light irradiation. The samples were characterized by X-ray diffraction, Fourier transform infrared, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Compared with BOI (k 1 = 0.0044 h −1 ), BHZA (k 2 = 0.0054 h −1 ), and BOI 0.04 -BHZA (k 3 = 0.0073 h −1 ), the degradation rate constant of Bi 5 O 7 I/ZnO n-n heterojunction microspheres (k 4 = 0.013 h −1 ) increased by 2.9, 2.4, and 1.8 times, respectively. Approximately 91% of PFOA was degraded after 6 h of irradiation. The excellent photocatalytic performance was ascribed to the Bi 5 O 7 I/ZnO n-n heterojunction formed by calcination, which enlarged the photoresponse to the visible light region and increased the separation efficiency of electron-hole pairs. Moreover, the degradation pathway of PFOA was investigated using high-performance liquid chromatography-mass spectrometry and ion chromatography assisted by density functional theory calculations. The results demonstrated that the carboxylic groups of PFOA was vulnerable to attack by the photoproduction hole. The formed unstable perfluoroheptyl radicals transformed into shorter chain perfluorocarboxylic acids by the elimination of CF 2 units. It was expected that this Bi 5 O 7 I/ZnO n-n heterojunction photocatalyst would be a promising candidate for PFOA treatment.

Preparation of orange peel loaded Zn/Al-HT and its adsorption for Cr(VI) in water

The orange peel loaded Zn/Al Hydrotalcite (Zn/Al-HT) was prepared by coprecipitation method. The effects of calcination temperatures, initial concentrations and pH on the adsorption properties of Cr(VI) were investigated, and the results showed that the calcined orange peel loaded Zn/Al-HT at 300°C(Mod2-LDO-300) had best removal rate of Cr(VI), it can be 96%, and the adsorption capacity is 38.5-106.2mg/g in the range of Cr (VI) initial concentration of 20-80mg/L. The Mod2-LDO-300 has a good adsorption effect at pH 2-8. It is a kind of environmental protection and industrial adsorption material.

Controlled release of herbicides by 2,4-D-, MCPA-, and bromoxynil-intercalated hydrotalcite nanosheets

Herbicide-intercalated Zn–Al hydrotalcites were facilely fabricated by a simple, rapid, and sustainable process and could reduce the volatilization and leaching risks simultaneously without affecting herbicidal activity.

In-situ fabrication of a spherical-shaped Zn-Al hydrotalcite with BiOCl and study on its enhanced photocatalytic mechanism for perfluorooctanoic acid removal performed with a response surface methodology

Perfluorooctanoic acid (PFOA), a widely used compound, is harmful to the environment and human health. In this study, a facile one pot solvothermal method of integrating BiOCl with Zn-Al hydrotalcite to form spherical-shaped BiOCl/Zn-Al hydrotalcite (B-BHZA) sample is reported. The characteristics and main factors affecting photocatalytic PFOA and photocatalytic mechanism of BiOCl/Zn-Al hydrotalcite (B-BHZA) are systematically investigated. It is found that spherical-shaped B-BHZA possesses abundant defects and a larger surface area of 64.4 m2 g−1. The factors affecting photocatalytic removal PFOA (e.g., time, pH, initial concentration and dosage) are investigated by modeling the 3D surface response. The removal rate of PFOA is over 90 % in 6 h under UV light at an optimal pH of 2, an initial concentration of 500 μg/L and a dose of dosage 0.5 g/L. The main mechanism occurs by photo-generated h+ oxidation and synergistic effects from the photocatalysis process. Though investigating the intermediates of PFOA degradation and F−, a possibility was proposed that h+ initiated the rapidly decarboxylation of PFOA. The unstable perfluoroheptyl group is formatted and further conversed to short chain perfluorocarboxylic acid. This study provides a new insight for the preparation of highly efficient photocatalysts to the treatment of halogenated compounds in UV system.

Keratin/Hydrotalcites Hybrid Sponges as Promising Adsorbents for Cationic and Anionic Dyes.

In this work, keratin sponges were prepared by freeze-drying method and tested for adsorption of Azure A and Methyl Orange dyes. The obtained materials showed a porosity of 99.92% and a mean pore size dimension of about 91 μm. The use of oxidized sucrose with a heating treatment at 150°C was demonstrated to be a useful crosslinking procedure alternative to the conventional glutaraldehyde. Keratin sponges showed a maximum adsorption capacity of 0.063 and of 0.037 mmol/g for Azure A and Methyl Orange, respectively. The absorption of the cationic dye Azure A onto keratin sponges was better described by Freundlich model while the isotherm adsorption of the anionic Methyl Orange was found to correlate with both Langmuir and Freundlich models. The mean free energies evaluated by using the D-R model indicated a physisorption of Methyl Orange and a chemisorptions of Azure A onto keratin sponges. Finally, the functionalization of keratin sponges with Zn Al hydrotalcites nanoparticles did not affect the adsorption performances of the adsorbent toward the cationic dye Azure A, while it improved those toward the anionic Methyl Orange, increasing the related removal efficiencies from 43 to 96%. Collectively, the reported data indicates that the combination of keratin with hydrotalcites nanoparticles is a good strategy to obtain more functional adsorbent materials of potential interest for water treatment and purification.

Tuning the Basic Properties of ZnAl Hydrotalcites Modified with Ce Applied to Transesterification of Soybean Oil

The basicity of ZnAl hydrotalcite type materials was modified through the incorporation of Ce into their structure and used as heterogeneous catalysts in the transesterification of soybean oil. A series of novel ZnAl–Ce(X) catalysts was synthesized by the co-precipitation method varying the loading of Ce (X = Ce/Al molar ratio). The larger ionic radius of Ce3+ (1.01 A) compared with Al3+ (0.53 A) and Zn2+ (0.72 A), hinders the appropriate incorporation of Ce3+ in the brucite-like structure, causing a small segregation of Ce3+ as CeO2. However, the concentration of basic sites (acid–basic Lewis pairs) and specific surface area of the ZnAl–Ce(0.0) sample were enhanced with the incorporation of Ce, improving its catalytic activity. The most appropriate Ce loading was obtained with a Ce/Al molar ratio of 0.03, which was attributed to its large surface area, along with a higher amount of acid–basic Lewis pairs related to the presence of aluminum in pentahedral coordination. Thus, the total amount of basic sites (−OH and M–O−) of ZnAl–Ce(0.03) was triplicated, leading to a FAME yield of 80% with this catalyst, which represents an increase of 11.3% when compared with the ZnAl hydrotalcite without Ce.

Structural Characterization of ZnO and Al Doped ZnO Powders Synthesis in Aqueous Solutions

Undoped and Al-doped ZnO (AZO) powders have been synthesized by hydrolytic and hydrothermal synthesis from Zn(NO3)2 , AlCl3 using KOH 1M concentraction like hydrolisis agent. The structural properties of prepared powders were studied using XRD and FTIR spectroscopy. Presence of aluminium in the hydrothermal powders is correlated with the presence of Zn-Al hydrotalcite like structure.

Effect of Interlamelar Composition on ZnAl Hydrotalcites: Synthesis and Characterization

The preparation and characterisation of ZnAl hydrotalcites with varying interlamellar anions have been investigated. The synthesis was achieved through co-precipitation at low supersaturation, accompanied by hydrothermal curing at 110˚C for 18h. A range of techniques such as XRD, XRF, FT-IR, TG-DTA, SEM, and surface area were utilised to investigate the effect that the varying of interlamellar anions impacted on the hydrotalcites. The x-ray diffraction and FT-IR data confirmed that the samples synthesised were hydrotalcites with the intercalation of various anions of interest. The nitrate hydrotalcite showed less stacking order with highest basal spacing, while the carbonate hydrotalcite showed smallest unit cell, more regular stacked sheets, and denser nanoparticles. Thermal results are identical in all hydrotalcite studied but with variance in the temperature of the decomposition stages. Suraface area and the scanning electron microscopy analysis demonstrated that the composition of interlamella region influences the structure and properties of the synthesised hydrotalcites.