scholarly journals Influence of Zn/Fe Molar Ratio on Optical and Magnetic Properties of ZnO and ZnFe2O4Nanocrystal as Calcined Products of Layered Double Hydroxides

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Abdullah Ahmed Ali Ahmed ◽  
Zainal Abidin Talib ◽  
Mohd Zobir Hussein ◽  
Moayad Husein Flaifel ◽  
Naif Mohammed Al-Hada
Keyword(s):  
Magnetic Properties ◽  
Near Infrared ◽  
Mixed Oxides ◽  
Diffuse Reflectance Spectroscopy ◽  
Molar Ratio ◽  
Nanometer Scale ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Double Hydroxide ◽  
Double Hydroxides

The coprecipitation method has been used to synthesize layered double hydroxide (Zn-Fe-LDH) nanostructure at different Zn2+/Fe3+molar ratios. The structural properties of samples were studied using powder X-ray diffraction (PXRD). LDH samples were calcined at 600°C to produce mixed oxides (ZnO and ZnFe2O4). The crystallite size of mixed oxide was found in the nanometer scale (18.1 nm for ZnFe2O4and 43.3 nm for ZnO). The photocatalytic activity of the calcination products was investigated using ultraviolet-visible-near infrared (UV-VIS-NIR) diffuse reflectance spectroscopy. The magnetic properties of calcined LDHs were investigated using a vibrating sample magnetometer (VSM). The calcined samples showed a paramagnetic behavior for all Zn2+/Fe3+molar ratios. The effect of molar ratio on magnetic susceptibility of the calcined samples was also studied.

Preparation of Sodium Paeonolsilate Intercalated into Layered Double Hydroxides and its Release Properties

2015 ◽  
Vol 1095 ◽  
pp. 349-354 ◽  
Author(s):  
Liang Hua Gu ◽  
Hong Qing Song ◽  
Zhi Yong Sun ◽  
Ji Yong Zheng ◽  
Jin Wei Zhang ◽  
...  
Keyword(s):  
Controlled Release ◽  
Release Kinetics ◽  
Molar Ratio ◽  
Burst Release ◽  
X Ray Diffraction ◽  
Release Process ◽  
Rate Determining Step ◽  
Release Ratio ◽  
Double Hydroxide ◽  
Double Hydroxides

A controlled release composite has been prepared by intercalation of sodium paeonolsilate (PAS) into Mg/Al layered double hydroxide (LDH) with the molar ratio (M2+/M3+) of 2:1. The powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) confirm the intercalation of PAS into the galleries of LDH. The chemical composites of PAS-LDH were revealed by elemental analysis. Release tests of the PAS-LDH composite showed that no burst release phenomenon occurred at the beginning stage and a high release ratio of PAS (89.8%) was obtained, exhibiting controlled release behavior. Furthermore, the parabolic diffusion model was used to simulate the release kinetics of PAS from the LDH carrier, indicating that the intraparticle diffusion via ion-exchange is the rate-determining step in the release process. It is significance in this work for introducing the PAS-LDH composite to develop antifouling materials with long-term activity.

scholarly journals Silver Orthophosphate Immobilized on Flaky Layered Double Hydroxides as the Visible-Light-Driven Photocatalysts

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Xianlu Cui ◽  
Yaogang Li ◽  
Qinghong Zhang ◽  
Hongzhi Wang
Keyword(s):  
Visible Light ◽  
Diffuse Reflectance Spectroscopy ◽  
Diffraction Field ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Photocatalytic Activities ◽  
Visible Light Driven ◽  
Double Hydroxide ◽  
Double Hydroxides ◽  
Acid Red G

Flaky layered double hydroxide (FLDH) was prepared by the reconstruction of its oxide in alkali solution. The composites with FLDH/Ag3PO4mass ratios at 1.6 : 1 and 3 : 1 were fabricated by the coprecipitation method. The powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, and UV-vis diffuse reflectance spectroscopy. The results indicated that the well-distributed Ag3PO4in a fine crystallite size was formed on the surface of FLDH. The photocatalytic activities of the Ag3PO4immobilized on FLDH were significantly enhanced for the degradation of acid red G under visible light irradiation compared to bare Ag3PO4. The composite with the FLDH/Ag3PO4mass ratio of 3 : 1 showed a higher photocatalytic efficiency.

Photocatalytic decolourization of methylene blue using [Zn-Al] layered double hydroxides synthesized at different molar cationic ratios

Clay Minerals ◽  
2017 ◽  
Vol 52 (2) ◽  
pp. 203-215 ◽  
Author(s):  
Kaouther Abderrazek ◽  
Najoua Frini Srasra ◽  
Ezzeddine Srasra
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Layered Double Hydroxides ◽  
Diffuse Reflectance Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Inductively Coupled ◽  
Molar Ratios ◽  
Constant Ph ◽  
Double Hydroxides

Abstract[Zn-Al] layered double hydroxides (LDH) with cationic molar ratios of R = Zn/Al 1–5 were synthesized by the coprecipitation method at constant pH = 10. The samples synthesized and their derived forms obtained after calcination at 500°C and at 900°C (denoted Zn-Al-R, Zn-Al-R-500 and Zn-Al-R-900, respectively), were characterized by X-ray diffraction (XRD), inductively coupled plasmamass spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, diffuse reflectance spectroscopy and nitrogen physisorption at −196°C. The XRD study showed: (1) the presence of accessory ZnO with the LDH in samples synthesized with R ≥ 3; and (2) the lamellar structure was destroyed at 500°C which made room for a poorly ordered ZnO phase, while calcination at 900°C yielded well crystallized ZnO and ZnAl2O4. The photocatalytic activity of the calcined and the unheated samples was evaluated for the decolourization of methylene blue. The photocatalytic activity was dependent on the cationic ratio R and on the calcination temperature. The sample Zn-Al-3 displayed maximum photocatalytic activity. Calcination at 500 and 900°C improved the photocatalytic activity of LDH synthesized at R = 1 and 2.

Synthesis and Characterization of MgFe2O4 /MgO Composite Films from Layered Double Hydroxides Precursors

2013 ◽  
Vol 690-693 ◽  
pp. 342-350
Author(s):  
Ying Chao Zhang ◽  
Ting Ting Chen ◽  
Lan Yang
Keyword(s):  
Magnetic Properties ◽  
Composite Films ◽  
Xrd Analysis ◽  
Particle Size Analysis ◽  
Molar Ratio ◽  
Size Analysis ◽  
X Ray ◽  
Single Source Precursor ◽  
Double Hydroxide ◽  
Double Hydroxides

MgFe2O4/MgO composite films have been successfully fabricated by a facile route using magnesium iron layered double hydroxide (MgFe-LDH) as a single-source precursor. This strategy mainly involves the formation of MgFe-LDH film by casting the slurry of MgFe-LDH precursor on the α-Al2O3substrate, followed by calcination at 900°C. The structure, morphology and magnetic properties of the resulting films were characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), laser particle size analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and vibrating sample magnetometer (VSM). The results show that the composite films are composed of spherical or elliptical grains with diameters of less than 150nm and their thickness range was 2~3 μm. EDX mapping analysis reveals that the composite films have uniform distribution of MgFe2O4particles in MgO matrix. Further investigation indicates that the magnetic properties of the composite films can be tailored by altering the Mg/Fe molar ratio of LDH precursors.

scholarly journals Removal of Lead from Aqueous Solution by Adsorption using Magnesium Aluminium Hydrogenphosphate Layered Double Hydroxides

2014 ◽  
Vol 8 (1) ◽  
Author(s):  
Zaini Hamzah ◽  
Mohd Najif Ab Rahman ◽  
Yamin Yasin ◽  
Siti Mariam Sumari ◽  
Ahmad Saat
Keyword(s):  
Aqueous Solution ◽  
Layered Double Hydroxide ◽  
Molar Ratio ◽  
Maximum Adsorption Capacity ◽  
Lead Removal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation ◽  
Double Hydroxide ◽  
Double Hydroxides

Layered double hydroxide with molar ratio of 4 (MAN 4) was synthesized by co-precipitation and followed by hydrothermal method. The compound was then later going through ion exchange with K2HPO4 for 48 hours to produce MgAlHPO4 (MAHP 4). The solid produced were characterized using X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). Adsorption of lead solution by MAHP 4 was carried out using batch experiment by mixing the lead solution and the solid of layered double hydroxide. The effects of various parameters such as contact time, pH, adsorbent dosage and initial concentration were investigated. The optimum pH for lead removal was found to be at pH of 5 and the optimum time of lead removal was found at 2 hours. The isotherm data was analysed using Langmuir and the correlation coefficient of 0.998 was obtained. The maximum adsorption capacity, Qo (mg/g) of 500 mg/g was also recorded from the Langmuir isotherm. The remaining lead solution was determined by using EDXRF (Energy Dispersive X-Ray Fluorescence spectrometry) model MiniPal 4 (PAN analytical). The results in this study indicate that MAHP 4 was an interesting adsorbent for removing lead from aqueous solution.

scholarly journals Removal of methylene blue from aqueous solution using Mg-Fe, Zn-Fe, Mn-Fe layered double hydroxide

2020 ◽  
Vol 81 (12) ◽  
pp. 2522-2532
Author(s):  
Zhongliang Shi ◽  
Yanmei Wang ◽  
Shuyu Sun ◽  
Cheng Zhang ◽  
Haibo Wang
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Langmuir Adsorption ◽  
Molar Ratios ◽  
Pseudo Second Order ◽  
Co Precipitation ◽  
Double Hydroxide ◽  
Double Hydroxides

Abstract Layered double hydroxides (LDH) with highly flexible and adjustable chemical composition and physical properties have attracted tremendous attention in recent years. A series of LDH with different M (Mg, Zn, Mn)-Fe molar ratios were synthesized by the double titration co-precipitation method. The effect of the factors, including M (Mg, Zn, Mn) : Fe molar ratio, pH, and M-Fe LDH dosage, on the ability of the prepared M-Fe LDH to remove cationic methylene blue (MB) dye from aqueous solution were investigated. Results indicated that the removal efficiency of MB (10 mg/L) was the best at the M (Mg, Zn, Mn): Fe molar ratio of 3:1 by using 2.0 g/L of M-Fe LDH at pH 6.0 under 298.15 K. Mg-Fe LDH had the highest removal performance (71.94 mg/g at 298.15 K) for MB compared to those of the Zn-Fe and Mn-Fe LDH. Zn-Fe LDH with the smallest activation energy resulted in the fastest adsorption rate of MB. The pseudo-second-order model and Langmuir adsorption isotherm were also successfully applied to fit the theory of M-Fe LDH for removal of MB.

Investigation of the Dye-Sensitized Solar Cell Prepared by the Mixed Oxide from the ZnAl-Layered Double Hydroxide

2013 ◽  
Vol 816-817 ◽  
pp. 115-118
Author(s):  
Liang Ji Zhang ◽  
Ming Zhe Leng ◽  
Yao Wei Qin ◽  
Jian Qiang Liu
Keyword(s):  
Solar Cells ◽  
Mixed Oxides ◽  
Dye Sensitized Solar Cells ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Dye Sensitized ◽  
Different Temperatures ◽  
Basic Parameters ◽  
Double Hydroxide ◽  
Sensitized Solar Cells

The layered double hydrotalcites (LDH) with molar ratio Zn:Al=2:1 was prepared by urea method. The mixed oxides were prepared by calcining the LDH at different temperatures and a series of dye-sensitized solar cells were assembled by the corresponding oxides and the dye Ruthenizer 535-bisTBA (N719). The basic parameters were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric and differential thermal analysis (TG-DTA) and UV-Vis absorption spectrum. The photovoltaic behaviors of solar cells were characterized and the best efficiency was 0.015% when the calcining temperature was 500°C.

Zn-Cr Layered Double Hydroxides Composites for Methyl Orange (MO) Absorption

2018 ◽  
Vol 281 ◽  
pp. 836-841
Author(s):  
Tao Zhou ◽  
Jian Ping Ai ◽  
Wei Xiu Liao ◽  
Li Hong Cheng ◽  
Yue Zhang ◽  
...  
Keyword(s):  
Methyl Orange ◽  
Layered Double Hydroxides ◽  
Adsorption Property ◽  
Bet Surface Area ◽  
Molar Ratio ◽  
Light Illumination ◽  
X Ray Diffraction ◽  
Anionic Dyes ◽  
Molar Ratios ◽  
Double Hydroxides

In this study, The Zn-Cr nanocomposite was synthesized using the hydrothermal method show good adsorption property. The as-prepared LDHs absorbent were characterized by Powder X-ray Diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FT-IR), BET surface area, and simultaneously UV-visible spectrophotometer. The nanocomposites of Zn-Cr layered double hydroxides, the strong adsorptive adsorbents for anions. Zn-Cr LDHs with various Zn/Cr molar ratios for 2, 3, 4. The nanocomposites quickly adsorbed the anionic dyes such as methyl orange (MO) without the light illumination. The effects of Zn/Cr molar ratio on the adsorption performance of Zn-Cr LDHs were investigated.

scholarly journals Modification of Nife Layered Double Hydroxide and Photocatalytic Activity

2019 ◽  
Vol 25 (4) ◽  
pp. 460-465 ◽  
Author(s):  
Huan YU ◽  
Weiwei WANG ◽  
Pengfei FANG
Keyword(s):  
Photocatalytic Activity ◽  
Photocatalytic Performance ◽  
Diffuse Reflectance Spectroscopy ◽  
Adsorption Property ◽  
X Ray Diffraction ◽  
X Ray ◽  
Valence States ◽  
Double Hydroxide ◽  
Double Hydroxides ◽  
Fe Ions

Modifying materials by ions with multiple valence states is an effective way for enhancing their properties. NiFe layered double hydroxides (NiFe LDHs) were prepared by using a hydrothermal method. Efficient LDH photocatalyst was synthesized by the modification of NiFe LDHs with Fe(III). Electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, photoluminescence spectroscopy, and UV-Vis diffuse reflectance spectroscopy were used to investigate the morphology, crystal structure, and optical properties of the NiFe LDHs. The photocatalytic and adsorption performances were examined in the degradation of methyl orange. NiFe LDHs exhibited higher adsorption property but lower photocatalytic activity. After modification with Fe(III), the introducing of Fe ions and recrystallization of LDHs led to the distance decreasing between NiFe LDH sheets and exhibit higher photocatalytic performance.

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

2022 ◽  
Vol 9 ◽  
Author(s):  
Lada Dubnová ◽  
Rostislav Daňhel ◽  
Vendula Meinhardová ◽  
Valeriia Korolova ◽  
Lucie Smoláková ◽  
...  
Keyword(s):  
Layered Double Hydroxide ◽  
Mixed Oxides ◽  
Diffuse Reflectance Spectroscopy ◽  
Aldol Condensation ◽  
X Ray Diffraction ◽  
Basic Properties ◽  
Catalytic Potential ◽  
Adsorption Temperature ◽  
Temperature Programmed ◽  
Double Hydroxide

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.

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