T (+98) 23 352 20220
Email: international@du.ac.ir
Damghan University
University Blvd, Damghan, IR
Azim Malekzadeh
Dean of School of Chemistry and Associate Professor of Inorganic Chemistry
TEL: +98-9123113115
Selected Publications
DOI: 10.1016/j.measurement.2018.09.041
Particle size distribution is determined by various methods such as laser diffraction scattering, image counting, sieving and sedimentation methods, none of which are perfect and need to be refined in the fields of soil science and civil engineering. This study tried to achieve a more accurate method for gradation of fine-grained soils. Regarding the concept of sedimentation and spectrophotometry, experimental and theoretical studies have been done on the particle size measurement of seventeen fine-grained soil samples. The diameter of the particles was determined on the basis of the Stokes’ law of settling velocity for particles in suspension placed in the cuvette whereas the percentage finer than these diameters were determined by a formula derived herein using the spectrophotometry method at the operating range of 900–1000 nm. The ratios between the concentration values at each reading time and the initial value were related to the percentage of particles passing. The gradation curves obtained by this method for the soil samples in this study correspond to the curves of microscopy imaging analysis. Compared with other methods, this test procedure and the related calculations are rather convenient. © 2018 Elsevier Ltd
AUTHOR KEYWORDS: Fine-grained soils; Gradation; Sedimentation; Spectrophotometry
INDEX KEYWORDS: Consolidation; Light transmission; Particle size; Particle size analysis; Sedimentation; Size distribution; Soils; Spectrophotometry; Suspensions (fluids); Testing, Concentration values; Fine grained soil; Gradation; Laser diffractions; Microscopy imaging; Particle size measurement; Settling velocity; Spectrophotometry methods, Soil surveys
PUBLISHER: Elsevier B.V.
DOI: 10.1007/s10854-018-0069-y
Graphene oxide (GO) and reduced graphene oxide (RGO) nanostructures were synthesized using a novel method of CO gas flow under ambient pressure and at several temperatures. The produced samples of GO and RGO were structurally, chemically and optically characterized and the results were analyzed using the techniques of UV–Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, field-effect scanning electron microscopy (FE-SEM), and sheet resistance measurements. Thermo-gravimetric analysis, and FTIR indicated the successful preparation of GO and RGO. FE-SEM was used to demonstrate the layer structure of GO and RGO nanostructures. The band gap energy (Eg) of the samples was estimated through the optical absorption spectra of GO and RGOs recorded between 200 and 1100 nm wavelengths using UV–Vis spectroscopy. The results are in good agreement with the data determined by other workers. Sheet resistance of RGO shows a decreasing trend versus annealing reduced temperature. This behavior is in accordance with variation of c-axis parameter with temperature which can be suggested to be due to the removal of water molecules and oxygen-containing functional groups between the carbon layers of the GO. Removing of the latter components may results in decreasing the distance between the graphene nano-layers. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
INDEX KEYWORDS: Energy gap; Flow of gases; Graphene; Gravimetric analysis; Light absorption; Molecules; Nanosheets; Scanning electron microscopy; Sheet resistance; Thermogravimetric analysis, Ambient atmosphere; Ambient pressures; Efficient synthesis; Layer structures; Oxygen-containing functional groups; Reduced graphene oxides; Reduced graphene oxides (RGO); Sheet resistance measurements, Fourier transform infrared spectroscopy
PUBLISHER: Springer New York LLC
DOI: 10.1007/s10562-018-2537-7
A hydrothermal technique was employed in order to produce a novel coordination polymer [Co0.42Ni0.40Zn0.68(btc)(H2O)6] (1). The complex (1) was characterized by elemental analysis, and FT-IR spectroscopy; and its structure was determined by single crystal X-ray diffraction (XRD). Alumina-supported Co–Ni–Zn and silica catalysts were prepared by thermal decomposition of respective inorganic precursors (fabricated or synthesized catalysts) and through impregnation method as reference catalysts. The evaluation of catalytic activity of these catalysts was carried out at a fixed bed reactor for Fischer–Tropsch synthesis. The performance of the synthesized catalysts was much better than the catalysts which were produced by the impregnation procedure, those that were characterized by scanning electron microscopy (SEM), XRD, and BET specific surface area. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
AUTHOR KEYWORDS: Catalytic performance; Fischer–Tropsch synthesis; Inorganic precursor; Metal oxide promoter; Mixed metal catalyst
INDEX KEYWORDS: Alumina; Aluminum oxide; Chemical reactors; Cobalt; Cobalt deposits; Crystal structure; Decomposition; Impregnation; Scanning electron microscopy; Silica; Single crystals; X ray diffraction, Catalytic performance; Inorganic precursor; Metal oxides; Mixed-metals; Tropsch synthesis, Catalyst activity
PUBLISHER: Springer New York LLC
DOI: 10.1007/s11164-018-3484-z
Three tetrahedral coordination compounds formed from Ni(II), Cu(II), and Zn(II) transition-metal ions with ON-donor, (2-aminophenol) ligand (L), were synthesized and characterized by Fourier-transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, elemental analysis, and magnetic susceptibility measurements. The magnetic properties revealed that the NiL2 and CuL2 complexes were paramagnetic while the ZnL2 complex was diamagnetic. Also, photodegradation of methylene blue as model organic pollutant by the synthesized complexes was studied based on an oxidation process under visible-light irradiation. The results showed that the photocatalytic activity of the Cu complex was greater compared with the Ni and Zn complexes, with degradation efficiency of 100, 85, and 60 %, respectively, after 30 min of irradiation in this condition. Thus, the Cu (bis-chelate) complex is more efficient, produces higher yield, is easily produced, and represents a more stable heterogeneous photocatalyst for degradation of organic dyes such as methylene blue. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
AUTHOR KEYWORDS: Bis-chelate complexes; Heterogeneous catalyst; Methylene blue; NO-donor ligand; Photodegradation; Visible light
INDEX KEYWORDS: Absorption spectroscopy; Aromatic compounds; Chelation; Complexation; Degradation; Fourier transform infrared spectroscopy; Irradiation; Ligands; Light; Magnetic susceptibility; Metal ions; Nickel compounds; Organic pollutants; Photocatalysts; Photodegradation; Synthesis (chemical); Transition metals; Zinc compounds, Bis-chelate complexes; Heterogeneous catalyst; Methylene Blue; NO donor; Visible light, Copper compounds
PUBLISHER: Springer Netherlands
DOI: 10.1016/j.carbpol.2018.03.102
SN38 is an active metabolite of irinotecan, which was approved for clinical use in metastatic colorectal cancers. However, poor aqueous solubility and inactivation at pH below 6 are the main limitations of its use. In the current study, we separately conjugated α-, β- and γ-cyclodextrins to graphene oxide sheets to produce stable, biocompatible nanocarriers for SN38 delivery. The conjugates were coordinated with Fe3O4 in the form of superparamagnetic iron oxide nanoparticles. Then, SN38 was non-covalently conjugated to the developed nano-conjugate in order to overcome its solubility and stability problems and reduce its side effects. The loading efficiency of different formulations was between 13–22%. α-CD-GO-Fe3O4-SN38 and γ-CD-GO-Fe3O4-SN38 significantly enhanced the cytotoxicity of the conjugates compared to the free drug. Besides, combined photothermal/chemotherapy study revealed that all the designed nano-platforms reduced the HT-29 cell line viability synergistically in vitro. However, β-CD-GO-Fe3O4-SN38 showed the highest synergistic effect compared to other formulations. In conclusion, the results of the study revealed that such combined treatment platforms might find their way as potential therapeutics to fight against cancer. © 2018 Elsevier Ltd
AUTHOR KEYWORDS: Cyclodextrin; Graphene oxide; Photodynamic therapy; Photothermal therapy; SN38; SPION
INDEX KEYWORDS: Biocompatibility; Cell culture; Controlled drug delivery; Cyclodextrins; Diseases; Graphene; Graphene oxide; Magnetite; Metabolites; Photodynamic therapy; Solubility; Targeted drug delivery, Active metabolites; Aqueous solubility; Gamma-cyclodextrin; Loading efficiency; Photothermal therapy; SN38; SPION; Superparamagnetic iron oxide nanoparticles, Iron oxides
PUBLISHER: Elsevier Ltd
DOI: 10.1016/j.ijhydene.2017.11.019
The silica- and alumina-supported Co–Zn catalysts were synthesized by thermal decomposition of new inorganic precursors [Co4.32Zn1.68(HCO2)18(C2H8N)6]/SiO2 or Al2O3. A novel coordination polymer formulated as [Co4.32Zn1.68(HCO2)18(C2H8N)6] (1) was prepared using the solvothermal technique and characterized by elemental analysis, FT-infrared spectroscopy. Thermal stability of the complex 1 was investigated by thermogravimetric analysis and differential scanning calorimetry, and its structure was determined by single-crystal X-ray diffraction. Characterization of catalysts was carried out using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET specific surface area. The catalysts were evaluated for Fischer–Tropsch synthesis (FTS) in the temperature range 200–300 °C. The results revealed that the synthesized catalysts have higher selectivity to the desired products at 260 °C. The performance of the catalysts was compared to those of catalysts constructed via impregnation method and the fabricated catalysts show higher activity and selectivity than the reference catalysts. © 2017 Hydrogen Energy Publications LLC
AUTHOR KEYWORDS: Catalytic performance; Coordination polymers; Fischer–Tropsch synthesis; Impregnation; Inorganic precursor
INDEX KEYWORDS: Alumina; Binary alloys; Catalyst activity; Catalyst selectivity; Catalysts; Cobalt alloys; Coordination reactions; Crystal structure; Decomposition; Differential scanning calorimetry; Impregnation; Infrared spectroscopy; Polymers; Scanning electron microscopy; Silica; Single crystals; Thermodynamic stability; Thermogravimetric analysis; X ray diffraction; Zinc alloys, BET specific surface area; Catalytic performance; Characterization of catalysts; Coordination Polymers; Ft-infrared spectroscopies; Inorganic precursor; Powder X ray diffraction; Single crystal x-ray diffraction, Fischer-Tropsch synthesis
PUBLISHER: Elsevier Ltd
DOI: 10.1016/j.molstruc.2017.05.027
The silica- and alumina- supported Ni catalysts synthesized by thermal decomposition of inorganic precursors were evaluated for Fischer–Tropsch synthesis (FTS); the structural properties and performance of the catalysts were compared to those of samples constructed via impregnation method. The results revealed that the synthesized catalysts have higher catalytic activity comparison to those prepared via the conventional impregnation method. The effect of the preparation method on the structural properties shows that synthesizing the catalyst through inorganic precursor route is more appropriate. Characterization of catalysts is carried out using inductively coupled plasma (ICP), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET specific surface area. © 2017 Elsevier B.V.
AUTHOR KEYWORDS: Coordination polymers; Fischer-Tropsch synthesis; Impregnation; Inorganic precursor; Nickel catalyst; Synthesis route
INDEX KEYWORDS: Alumina; Catalyst activity; Catalysts; Coordination reactions; Decomposition; Impregnation; Inductively coupled plasma; Nickel; Scanning electron microscopy; Structural properties; X ray diffraction, BET specific surface area; Characterization of catalysts; Coordination Polymers; Inductively coupled plasma (ICP); Inorganic precursor; Nickel catalyst; Powder X ray diffraction; Synthesis route, Fischer-Tropsch synthesis
PUBLISHER: Elsevier B.V.
DOI: 10.1111/ijac.12650
In this work, structural and catalytic properties of La0.7Bi0.3Mn1−xCoxO3 nanocatalysts with x=0.00, 0.25, 0.50, 0.75, and 1.00 prepared by citrate method are investigated. The structural characterization using X'Pert package and Fullprof program is an evidence for structural phase transition. The values of refined unit cell volume obtained from the Rietveld analysis show decreasing and increasing tendencies for values of x≤0.5 and x>0.5, respectively. The catalytic performance tests of the catalysts show that the samples x=0.00 and 0.25 have lower temperature of CO oxidation and C2H6 combustion, respectively. © 2017 The American Ceramic Society.
AUTHOR KEYWORDS: C2H6 combustion and CO oxidation; manganite-cobaltite; nanoperovskites; structural phase transition; X-ray diffraction analysis
INDEX KEYWORDS: Combustion; Manganese; Oxidation; Rietveld analysis; X ray diffraction analysis, Catalytic performance; Catalytic properties; Co oxidation; Lower temperatures; Nanoperovskites; Structural characterization; Structural phase transition; Unit-cell volume, Catalytic oxidation
PUBLISHER: Blackwell Publishing Ltd
DOI: 10.1016/j.ceramint.2016.04.134
In this work, structural and catalytic properties of La1−xCaxMn0.5Co0.5O3 and La1−xSrxMn0.5Co0.5O3 nano-catalysts in the concentration range of 0.00≤x≤1.00 are investigated. The structural characterization of the compounds obtained by X-ray powder diffraction and using X′Pert package and Fullprof program is an evidence for structural phase transition of the samples that can be described by variation of tolerance factor. The obtained results also have been confirmed by FTIR measurements. The structural results, and the non-uniformly changes of activation energy, band gap energy and electrical conductivity values suggest the presence of different concentration of various cations Co+2, Co+3, Co+4, Mn+4 and Mn+3 in the compounds studied. The decrease of the crystallite size with increasing Ca and Sr substitution for x up to 0.5 in La1−x(Sr, Ca)xMn0.5Co0.5O3 can be related to the increase and decrease of micro-strain, respectively. Substituting Sr having higher ionic radius with respect to La in LaMn0.5Co0.5O3 shifts the catalytic activity of CO oxidation to lower temperature, whereas, for Ca substitution the catalytic activity shifts to higher temperature. The trend of catalytic activity observed for Ca- and Sr-substituted samples can be related to different morphology observed in SEM micrographs due to different types of micro-strain. La0.5Sr0.5Mn0.5Co0.5O3 nano-catalyst exhibits excellent CO conversion rate of 95% at 175 °C. © 2016 Elsevier Ltd and Techna Group S.r.l.
AUTHOR KEYWORDS: CO oxidation; Manganite–cobaltite; Nano-catalysts; Structural phase transition
INDEX KEYWORDS: Activation energy; Calcium; Catalyst activity; Catalysts; Catalytic oxidation; Cobalt compounds; Crystallite size; Energy gap; Lanthanum; Manganites; Oxidation; Temperature; X ray powder diffraction, Catalytic properties; Co oxidation; Concentration ranges; Electrical conductivity; Low-temperature CO oxidation; Nano-catalyst; Structural characterization; Structural phase transition, Manganese
PUBLISHER: Elsevier Ltd
DOI: 10.1021/acs.jpcc.6b00949
The charge and spin-state evolution of manganese and cobalt in the LaMn1-xCoxO3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) perovskite nanoparticles have been studied with soft X-ray absorption spectroscopy. The results show a gradual increase in the average oxidation state of both Mn and Co ions with cobalt doping. The average valence of the LaMn1-xCoxO3 samples remains close to 3.0, with the Mn valence increasing from 3.1 to 4.0 and the Co valence increasing from 2.0 to 3.0. The symmetry of Mn and Co was determined using multiplet calculations. Calculating the intensity-area of the oxygen K pre-edge feature confirmed an increase in covalency with increasing Mn and Co oxidation state. The ground-state composition of Mn3+ in LaMnO3, and Co3+ in LaCoO3, was investigated, and it was found that Mn3+ (D4h) and Co3+ (Oh) are mainly in their low-spin state, with 10-20% admixture of high-spin state contributions into a mixed spin ground state. © 2016 American Chemical Society.
INDEX KEYWORDS: Cobalt; Ground state; Nanoparticles; Spin dynamics; X ray absorption spectroscopy, Co oxidation; Cobalt doping; High spin state; Oxidation state; Pre-edge features; Soft x-ray absorption spectroscopies; Spin evolution; Spin state evolution, Manganese
PUBLISHER: American Chemical Society
DOI: 10.1016/j.ceramint.2015.12.101
Structural, magnetic and catalytic properties of La0.7Sr0.3Mn1-xCoxO3 (x=0.00, 0.25, 0.50, 0.75, 1.00) nano-perovskites prepared by the citrate method are investigated. The structural characterization of the compounds by X-ray powder diffraction and using X'Pert package and Fullprof program is an evidence for a monoclinic structure (P21/n space group) with x=0.50 and a rhombohedral structure (R-3c space group) for other samples. These results have been confirmed by the FT-IR measurements. Crystallite size of the powders obtained from Halder-Wagner method has been compared with the Scherrer method. The structural and magnetic results suggest the presence of different concentrations of various cations of Co+2, Co+3, Co+4, Mn+4 and Mn+3 in the samples. Activation energy, band gap energy, and electrical conductivity measurements have been employed to explain catalytic performance of the samples. The results of performance tests show that the sample with x=0.25 has the highest catalytic activity for CO oxidation, whereas, the sample with x=0.75 has the highest catalytic activity for C2H6 combustion. © 2016 Elsevier Ltd and Techna Group S.r.l.
AUTHOR KEYWORDS: C2H6 combustion; CO oxidation; Magnetic phase transition; Manganite-cobaltite; Nano-perovskite
INDEX KEYWORDS: Activation energy; C (programming language); Catalytic oxidation; Combustion; Crystallite size; Energy gap; Infrared imaging; Magnetism; Manganese; Oxidation; Perovskite; X ray powder diffraction, Catalytic performance; Co oxidation; Electrical conductivity measurements; Magnetic phase transitions; Monoclinic structures; Nano perovskites; Rhombohedral structures; Structural characterization, Catalyst activity
PUBLISHER: Elsevier Ltd
DOI: 10.1016/j.mssp.2015.10.019
Cubic cobalt oxide nanoparticles with the formula of Co3O4 were synthesized via thermal treatment in air, using [CoII{(μ-L)(μ-OAc)CoIII(NCS)}2]; [H2L=salen=1,6-bis(2-hydroxyphenyl)-2,5-diazahexa-1,5-diene]; as precursor. Effect of calcination temperature and citric acid, as emulsifier, was investigated on the phase formation and particle size distribution of the products. Calcination of the precursor at 600 °C in the presence of citric acid results in the formation of Co3O4 nanoparticles with the average crystallite size of ∼13 nm. The presence of citric acid provides conditions for the formation of more pure Co3O4 crystalline phase with smaller particles. The as-prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), particle size analyzer (PSA), transmission electron microscopy (TEM), UV-vis and Photoluminescence (PL) spectroscopies. The optical property studies indicate that the absorption peaks of Co3O4 nanoparticles, prepared in the presence of citric acid, shift towards short wavelengths. This blueshift is related to the quantum size effect. © 2015 Elsevier Ltd. All rights reserved.
AUTHOR KEYWORDS: Cobalt oxide; Complex precursor; Cubic; Optical property; Thermal treatment
INDEX KEYWORDS: Atomic force microscopy; Calcination; Citric acid; Cobalt; Crystallite size; Electron microscopy; Emulsification; Fourier transform infrared spectroscopy; Heat treatment; High resolution transmission electron microscopy; Nanoparticles; Optical properties; Particle size; Particle size analysis; Scanning electron microscopy; Synthesis (chemical); Transmission electron microscopy; X ray diffraction, Calcination temperature; Cobalt oxide nanoparticles; Cobalt oxides; Complex precursors; Cubic; Fourier transform infra red (FTIR) spectroscopy; Particle size analyzers; Quantum size effects, Cobalt compounds
PUBLISHER: Elsevier Ltd
In this work, structural, magnetic and catalytic properties of LaMn1-xCoxO3 (x = 0.00, 0.25, 0.50, 0.75, 1.00) are investigated. The structural characterization of the samples by X-ray powder diffraction and using the X'Pert package and Fullprof program is evidence for a monoclinic structure (P21/n space group) with x = 0.5 and a rhombohedral structure (R-3c space group) for other samples. These results have been confirmed by FTIR measurements. The magnetic characterizations of the samples have been studied by magnetization measurement versus temperature and field. The structural and magnetic results show the ferromagnetic interactions of Co2+-Mn4+ for x ≤ 0.5 are being progressively replaced by the less effective Co2+-Co3+ and Mn4+-Co3+ interactions for x > 0.5. The catalytic activity of LaMn1-xCoxO3 was evaluated for C2H6 combustion and CO oxidation reactions. Under similar reaction conditions, the catalytic results show that the LaMn0.5Co0.5O3 nano-perovskite is the best catalyst for C2H6 combustion and CO oxidation. © 2016 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.
AUTHOR KEYWORDS: C2H6 combustion; CO oxidation; Manganite-cobaltite; Nano-perovskite; Structural and magnetic phase transition
PUBLISHER: Bulgarian Academy of Sciences
DOI: 10.1016/j.cej.2015.04.032
Nano-mushroom ZnO and Cu-doped ZnO were prepared by co-precipitation method and characterized by general techniques. The particle size of ZnO is 28nm, while it decreased to 17nm by doping Cu2+ ion on it.Then, catalytic properties of these nanoparticles were studied in oxidation of benzylic alcohols by 30% H2O2 with nano-catalyst at room temperature. The results showed, a solvent free, green, selective, high yield and effective oxidation. Also, the catalytic performance such as: % conversion, % selectivity and rate of reaction of ZnO are significantly enhanced by doped 1% Cu metal cation on nano ZnO. The ketone and aldehyde are the main product of secondary and primary benzylic alcohols respectively under this condition. © 2015 Elsevier B.V.
AUTHOR KEYWORDS: Benzylic alcohols; Cu-doped; Green chemistry; Nano ZnO; Nanocatalyst; Oxidation
INDEX KEYWORDS: Catalytic oxidation; Copper; Ketones; Oxidation; Particle size; Positive ions; Precipitation (chemical); Zinc oxide, Benzylic alcohols; Cu-doped; Green chemistry; Nano-catalyst; Nano-ZnO, Catalyst activity, Basidiomycota
PUBLISHER: Elsevier
DOI: 10.1016/j.spmi.2014.09.027
A simple thermal decomposition route has been developed to prepare La2O3 and La2O2CO3 nanoparticles. Sonication of La2O3 nanoparticles in water at room temperature is accompanied to the formation of La(OH)3 nanoparticles. The effect of addition of citric acid, as disperser, was also investigated on the phase formation and particle size distribution of the products. It is observed that citric acid has no effect on the particle size of the samples. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses. Photocatalytic activity of the products was examined for degradation of methyl orange, a common reactive dye, as a pollutant under ultraviolet irradiation in the wastewater. The results show that La2O2CO3 nanoparticles are promising materials in this photocatalytic degradation with no significant loss of activity even after four cycles of successive uses. A pseudo-first-order kinetic is obtained for the photocatalytic degradation of methyl orange over La2O2CO3 nanoparticles according to the Langmuir-Hinshelwood analysis. © 2014 Elsevier Ltd. All rights reserved.
AUTHOR KEYWORDS: Citric acid; La2O2CO3; La2O3; Nanoparticles; Photocatalyst; Salicylaldehyde
INDEX KEYWORDS: Atomic force microscopy; Azo dyes; Citric acid; Citrus fruits; Decomposition; Fourier transform infrared spectroscopy; Lanthanum; Lanthanum oxides; Nanoparticles; Particle size; Particle size analysis; Photocatalysis; Photocatalysts; Transmission electron microscopy; Water treatment; X ray diffraction, Degradation of methyl oranges; Fourier transform infra red (FTIR) spectroscopy; Photo catalytic degradation; Photocatalytic activities; Pseudo-first order kinetics; Salicylaldehyde; Thermal decomposition routes; Ultraviolet irradiations, Synthesis (chemical)
PUBLISHER: Academic Press
DOI: 10.1016/j.seppur.2014.07.022
Nanosized La0.7Sr0.3MnO3 perovskite has successfully synthesized via citrate method. The product was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size analyzer (PSA). The degradation of methyl orange (MO), as a model of organic pollutant, was investigated in aqueous suspensions of La0.7Sr0.3MnO 3, as a visible-light photocatalyst, under a variety of conditions comprising amount of catalyst mass, pH of solution and the presence of electron acceptors of hydrogen peroxide, potassium persulphate, or hydrogen peroxide-urea. The MO was found to degrade more efficiently in acidic solution or in the presence of potassium persulphate as oxidant. The adsorption isotherm and the kinetic of photocatalytic degradation of MO were investigated. Reusability of the catalyst was also investigated. © 2014 Elsevier B.V. All rights reserved.
AUTHOR KEYWORDS: Organic pollutant; Photodegradation; Sunlight
INDEX KEYWORDS: Azo dyes; Catalysts; Fourier transform infrared spectroscopy; Hydrogen peroxide; Organic pollutants; Particle size analysis; Perovskite; Peroxides; Photodegradation; Reusability; Scanning electron microscopy; Suspensions (fluids); Urea; X ray diffraction, Degradation of methyl oranges; Nano perovskites; Particle size analyzers; Photo catalytic degradation; Potassium persulphate; Solar photocatalytic degradation; Sunlight; Visible-light photocatalysts, Manganese oxide
PUBLISHER: Elsevier
DOI: 10.1007/s10876-013-0617-9
Non-stoichiometric zirconium oxide nanocrystals with the formula of ZrO2.12 and diameters less than 10 nm were synthesized in the course of calcination of a dried solution of zirconium(IV) oxy nitrate in the presence of citric acid at 600 °C for 5 h. Crystallite size of product was increased to 20 nm when starch was used as emulsifier. Effect of the organic additive, which was equal of moles of the nitrate ions of the zirconium precursor, was investigated on phase formation, morphology and particle size of products. Samples were characterized by FT-IR, TG/DTA, SEM and TEM analysis. Phase structure of samples were also analysed by the powder X-ray diffraction. © 2013 Springer Science+Business Media New York.
AUTHOR KEYWORDS: Cubic; Nanoparticles; Non-stoichiometric; Organic disperser; Zirconia
DOI: 10.1007/s40195-014-0060-4
The collection of different cations in the A and B sites of ABO3 was explored for the regularity of perovskites phase formability. Here, Sr 2+, La3+, and Ce4+ are selected as the cations of site A. The site B is considered to be Mn or Co cations. XRD analysis and Fourier transform infrared spectroscopy results confirm the formation of perovskite structure for catalysts in which La3+ and Sr2+ are considered as the cations of site A. Ceria is detected as the main crystalline phase when Ce4+ is selected to be cation of site A. It is found that the octahedral factor (r B /r O) takes the same important role as the tolerance factor to form cubic perovskite. Average crystallite size of the products was calculated by data of the XRD and measured by the TEM analysis. Results of the XRD and TEM studies were supported by the study of the particles size distribution, which was carried out in a particle size analyzer. The perovskite samples were also used for stoichiometric oxidation of carbon monoxide with air. © 2014 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.
AUTHOR KEYWORDS: Carbon monoxide; Cerium; Lanthanum; Nano-perovskite; Oxidation; Strontium
INDEX KEYWORDS: Carbon monoxide; Catalysts; Cerium; Fourier transform infrared spectroscopy; Lanthanum; Manganese; Oxidation; Particle size analysis; Positive ions; Strontium, Carbon monoxide oxidation; Crystalline phase; Cubic perovskite; Nano perovskites; Octahedral factor; Particles size distribution; Perovskite structures; Structural feature, Perovskite
PUBLISHER: Chinese Society for Metals
DOI: 10.1007/s13738-013-0394-2
In this study, synthesis and characterization of two polymorphs of a new nano-sized zirconium(IV) complex, [ZrO(dmph)I2] (1), {dmph = 2,9-dimethyl-1,10-phenanthroline (neocuproine)}, have been investigated in two different solvents. The reaction between zirconyl nitrate pentahydrate and potassium iodide with dmph as a ligand under ultrasonic irradiation in methanol and mono-ethylene glycol (MEG) leads to the formation of the nano-sized Zr(IV) complex. Characterization of the Zr(IV) complex has been performed using scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and elemental analysis. The thermal stability of the compound 1 has been studied by thermal gravimetric and differential thermal analyses. Particle sizes of the compound 1 have been decreased after thermal treatments in an autoclave. Pure monoclinic (m) and tetragonal (t) zirconia (ZrO2) nanoparticles were readily synthesized from thermal decomposition of the Zr(IV) complex as a new precursor in presence of methanol and MEG as solvents, respectively. Zirconium oxide was characterized by FT-IR, XRD, and SEM to depict the phase and morphology. The results showed that, pure zirconia was produced with particle size about 59 nm and crystal system was monoclinic when methanol was used as a solvent during complexation process. On the other hand, particle sizes of zirconia with tetragonal structure were significantly reduced to about 39 nm, when MEG was used as solvent. © 2013 Iranian Chemical Society.
AUTHOR KEYWORDS: Nano-sized zirconium(IV) complex; Sonochemical method; Thermal decomposition
PUBLISHER: Springer Verlag
DOI: 10.1002/crat.201200423
Lanthanum oxide nanoparticles were synthesized via thermal decomposition method of the lanthanum nitrate in the presence of citric acid or starch as emulsifier. The effects of emulsifier and calcination temperature were investigated on the phase transformation and particle size distribution of the products. La2O3 nanoparticles were synthesized by drying lanthanum precursor and emulsifier solution, followed by calcination process at 600 and 900°C, respectively. Products were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal analysis (TG/DTA) and nitrogen adsorption method (porous characteristics). The morphology of the samples analyzed using scanning electron microscopy (SEM). Average crystallite size of the products was calculated by XRD data and average particle size was measured from the TEM micrographs. Lanthanum dioxycarbonate in different forms of the tetragonal and monoclinic is crystallized in the presence of citric acid and starch during the calcination at 600°C, respectively. The hexagonal structure, however, is detected as the only crystalline phase formed by calcination at 900°C. Lanthanum oxide nanoparticles are formed at lower temperature in the presence of starch in compared with citric acid when is used as emulsifier. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
AUTHOR KEYWORDS: Citric acid; Emulsifier; Lanthanum oxide; Nanoparticles; Starch
INDEX KEYWORDS: Average particle size; Calcination temperature; Emulsifier; Fourier transform infra red (FTIR) spectroscopy; Hexagonal structures; Lanthanum precursors; Porous characteristics; Thermal decomposition methods, Calcination; Citric acid; Decomposition; Emulsification; Gas adsorption; Lanthanum; Lanthanum alloys; Lanthanum oxides; Nanoparticles; Particle size analysis; Scanning electron microscopy; Starch; Thermoanalysis; Transmission electron microscopy; X ray diffraction, Synthesis (chemical)
DOI: 10.1016/S1002-0721(13)60020-4
Stoichiometric LaMnO3 and LaCoO3 nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La(NO3)3·6H2O/[Mn(NO3) 2·4H2O or Co(NO3)2· 6H2O]=1 and citric acid as disperser at temperature range of 600-900 C for 5 h. The role of organic additive concentration, which was 0.0, 1.0, 2.5 and 5 times of the total number of moles of the nitrate ions, was investigated on phase formation, morphology, extent of crystallization and particle size of the products. Products were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. The tendency of lanthanum ion toward manganese cation was observed to be more than to cobalt cation for the formation of LaBO3 (B: Mn or Co) perovskite phase. A spongy product was formed on perovskite phase formation or in the presence of citric acid. A constructive or destructive effect was observed for the organic disperser on perovskite phase formation, which depended on mole of the citric acid. © 2013 The Chinese Society of Rare Earths.
AUTHOR KEYWORDS: citric acid; mixed oxides; nano-perovskite; rare earths
INDEX KEYWORDS: Lanthanum; Manganese; Perovskite; Positive ions; Rare earths; Scanning electron microscopy; Synthesis (chemical); Transmission electron microscopy; X ray diffraction, Destructive effects; Fourier transform infrared spectroscopy (FT-IR); Mixed oxide; Moderate concentration; Nano perovskites; Perovskite phase formation, Citric acid
PUBLISHER: Chinese Society of Rare Earths
DOI: 10.1016/j.catcom.2012.08.009
The effect of partial substitution of lanthanum by strontium or bismuth in LaMnO 3 nano-perovskites, i.e. La (1 - x)(Sr or Bi) xMnO 3 samples, in which x = 0.0, 0.2 or 0.4, is explored for stoichiometric oxidation of carbon monoxide with air. FT-IR and XRD analyses confirmed the perovskite structure for the catalysts. Average crystallite size of the products was calculated by the data of XRD and average particle size was measured from the TEM micrographs. Small effect is observed on perovskite phase formation of LaMnO 3 on substitution of lanthanum with strontium or bismuth. Under similar reaction conditions, small substitution of bismuth has a more positive effect than strontium on lowering the CO oxidation temperature. © 2012 Elsevier B.V.
AUTHOR KEYWORDS: Bismuth; Carbon monoxide; Lanthanum manganite; Nano-perovskite; Oxidation; Strontium
INDEX KEYWORDS: Average particle size; Carbon monoxide oxidation; Co oxidation; Lanthanum manganites; Nano perovskites; Partial substitution; Perovskite phase formation; Perovskite structures; Reaction conditions; Structural feature; XRD; XRD analysis, Bismuth; Carbon monoxide; Catalysts; Lanthanum alloys; Manganese oxide; Oxidation; Perovskite; Strontium; Transmission electron microscopy, Lanthanum
DOI: 10.1016/j.matlet.2012.04.125
Thorium dioxide (thoria) nano-particle was synthesized by employing supercritical water (SCW) as an excellent reaction environment for hydrothermal crystallization of metal oxide particles. This method is ideal for production of ultrafine powder having controlled stoichiometry, high quality, purity and crystallinity. The nano-crystalline thoria was prepared in a stainless steel (316 L) autoclave, fed with an aqueous solution of Th(NO 3) 4.5H 2O as a reactant and took place under SCW condition up to 450 °C for 45 min. The product was recovered and characterized by X-Ray Diffraction (XRD), Thermal Gravimetry Analysis (TG/DTA) and Brunauer, Emmett and Teller (BET) surface area analysis. The crystallite size of the product was calculated by the Scherrer and Williamson-Hall equations and was subsequently measured by the Transmission Electron Microscopy (TEM) analysis. The average size was found to be about less than 27 nm with a particle size distribution in the 5-31 nm range. © 2012 Elsevier B.V. All rights reserved.
AUTHOR KEYWORDS: Hydrothermal; Nano-crystalline; Supercritical water; Thoria
INDEX KEYWORDS: Average size; Controlled stoichiometry; Crystallinities; High quality; Hydrothermal; Hydrothermal crystallization; Hydrothermal methods; Metal oxide particles; Nanocrystallines; Supercritical condition; Supercritical water; Surface area analysis; Thermal gravimetry; Transmission electron microscopy tem; Ultra fine powder; Williamson-Hall equation, Crystalline materials; Nanoparticles; Particle size analysis; Stoichiometry; Synthesis (chemical); Thoria; Transmission electron microscopy; X ray diffraction, Quality control
DOI: 10.1002/crat.201100240
Calcium carbonate nanoparticles were synthesized via so-called sol-gel citrate method using calcium nitrate as precursor in presence of different concentration of citric acid, selected to be 0.0, 0.5, 1.25 and 2.5 times of the concentration of the precursor, on calcining at 600 °C for 5 h. Stable phase of the calcite is formed in presence of citric acid. The roles of organic additive concentration, calcination temperature and sonication on the particle size of the products were investigated. Calcium oxide nanoparticles were prepared by facial calcination of the resulted product at 900 °C for 5 h. Calcium hydroxide nanoparticles, however, were synthesized on sonication of the product for 20 min in water at room temperature. Samples were characterized by XRD and FT-IR studies. Crystallite size of samples was calculated by XRD data and was measured by TEM analysis. The specific surface are (SSA) of samples was calculated by the XRD data and compared by the measured BET. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
AUTHOR KEYWORDS: Ca(OH) 2; CaCO 3; CaO; citric acid; nanoparticles
INDEX KEYWORDS: CaCO 3; Calcination temperature; Calcium nitrate; CaO; Citrate methods; FT-IR study; Organic additives; Room temperature; Specific surface; Stable phase; TEM analysis; XRD, Calcination; Calcium; Calcium carbonate; Carbonate minerals; Citric acid; Hydrated lime; Nanoparticles; Sol-gels, Synthesis (chemical)
Oxidative coupling of methane has been studied over (Mn+A+W)/SiO2 catalysts in a continuous-flow micro reactor, where A represents an alkali ion of Li, Na, K or Cs having different weight percents. The main aim of this study is to find the role of alkali ions in interaction between Mn and W species with SiO2 to make a proper structure for catalyzing oxidative coupling of methane (OCM) reaction. The catalysts were characterized by XRD, SEM, FTIR, TPR and also the electrical conductivity was measured in air and under OCM reaction. It was found that for the formation of crystallized catalyst, the amount of alkali ion should be such that the catalyst containing tungsten transforms into A2WO4. Using a smaller amount of alkali ions does not result in crystalline catalyst by calcination under the same condition of temperature and atmosphere. However, under the OCM reaction condition the catalyst gradually turns into a crystalline structure and its catalytic performance, i.e. conversion and selectivity, for the OCM reaction is almost similar to the (Mn+A2WO4)/SiO2 catalyst. The transformation of the catalyst containing alkali ions from amorphous to crystalline one indicates a kind of structural flexibility of the catalyst under OCM atmosphere. The structural flexibility of the catalyst under the OCM reaction is considered to be the main chemical role of the alkali ions.
AUTHOR KEYWORDS: Alkali ion; Electrical conductivity; Manganes oxide; Oxidative coupling of methane (OCM); TPR
PUBLISHER: Shiraz University
DOI: 10.1016/S1003-9953(10)60199-5
A comprehensive kinetic model for oxidative coupling of methane (OCM) over Mn and/or W promoted Na 2SO 4/SiO 2 catalysts was developed based on a micro-catalytic reactor data. The methane conversion and ethylene, ethane, carbon monoxide and carbon dioxide selectivities were obtained in a wide operating condition range of 750-825 °C, CH 4/O 2 = 2.5-10 and contact time = 267-472 kg·s·m -3. Reaction networks of six models with different rate equation types were compared together. The kinetic rate parameters of each reaction network were estimated using linear regression or genetic algorithm optimization method (GA). A reaction network suggested by Stansch et al. for OCM was found to be the best one and was further used in this work. The suggested model could predict the experimental results of OCM reaction within a deviation range of ±20. © 2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved.
AUTHOR KEYWORDS: fixed-bed reactor; genetic algorithm; kinetic modelling; oxidative coupling of methane (OCM)
INDEX KEYWORDS: Contact time; Fixed-bed reactors; Genetic algorithm optimization method; kinetic modelling; Kinetic models; Kinetic rate parameters; Kinetic study; Methane conversions; Micro-catalytic reactors; Operating condition; Oxidative coupling of methane; Rate equations; Reaction network, Carbon dioxide; Carbon monoxide; Catalysts; Chemical reactors; Ethane; Ethylene; Genetic algorithms; Kinetic theory; Kinetics; Manganese; Mathematical models; Silicon compounds; Sodium, Methane
DOI: 10.1002/crat.201000258
In this study the effects of citric acid concentration, used as organic emulsifier, on the perovskite phase formation of the nano strontium manganite or cobaltite samples were studied. Stoichiometric perovskites in the absence and presence of citric acid were prepared by drying a solution containing molar ratio of Sr(NO3)2/Mn(NO3)2 4H 2O and Sr(NO3)2/Co(NO3) 2-6H2O = 1 followed by calcination at 900 °C for 5 h. Citric acid concentration, selected to be 0.0, 0.3, 0.6, 1.0, 1.3, 2.5 and 5 times of the total number of moles of the nitrate ions. The results revealed that increase in the citric acid concentration, larger than number of moles of the nitrate ions equivalent, deteriorates the perovskite phase formation. Instead, a new phase of carbonates and metal oxides are appeared. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.
AUTHOR KEYWORDS: Citric acid; Emulsifier; Mixed oxides; Nano perovskite; SrCoO3; SrMnO3
INDEX KEYWORDS: Emulsifier; Mixed oxide; Nano perovskite; SrCoO3; SrMnO3, Calcination; Concentration (process); Emulsification; Manganese; Manganese oxide; Perovskite; Strontium, Citric acid
DOI: 10.1016/S1003-9953(09)60028-1
The effects of manganese oxide or ceria promoters on the performance of Na2WO4/SiO2 catalysts for oxidative coupling of methane (OCM) are reported. The OCM reaction was performed in a continuous-flow microreactor at 800 °C, atmospheric pressure and under GHSV = 13200 ml·gCat -1·h-1. Catalysts were characterized by in situ conductivity measurement, FT-IR spectroscopy, XRD, SEM and temperature programmed reduction analysis. Manganese oxide promoted Na2WO4/SiO2 is considered as one of the active and selective catalysts for OCM reaction. Ceria with high oxygen storage capacity is selected as a proper oxygen activator, providing a higher concentration of the oxy-anion species which is suitable for OCM reaction and compared with manganese oxide. Electrical conductivity of the catalysts was measured in OCM reaction under oxidizing atmosphere, i.e. in the absence of methane. It was found that the trimetallic catalysts, i.e. the catalysts having sodium, tungsten and Mn or Ce species, exhibited similar crystalline structures and morphologies, which lead to suitable bulk properties for the formation of an active and selective catalyst. However, tungsten had significant effect on the texture and redox properties of the catalysts. It was also shown that the crystalline structure of the bimetallic (Na+Mn or Ce)/SiO2 samples was quite different. This reveals that the metal oxides have significant effect on the extent of crystallization, taking place in the course of interaction of sodium with silica support. Similar conductivities and catalytic performances of (Na2WO4+Mn or Ce)/SiO2 catalysts propose that the ability of Na2WO4/SiO2 for utilizing oxy-anions formed in presence of different metal oxides is limited. © 2010 CAS/DICP.
AUTHOR KEYWORDS: ceria; conductivity; manganese oxide; oxidative coupling of methane (OCM); TPR
INDEX KEYWORDS: Anion species; Bulk properties; Catalytic performance; Concentration of; Continuous-flow; Crystalline structure; Electrical conductivity; FTIR spectroscopy; In-situ; In-situ measurement; Metal oxides; Micro-reactor; Oxidative coupling of methane; Oxidizing atmosphere; Oxygen storage capacity; Reaction under; Redox property; Selective catalysts; SEM; Silica supports; Temperature programmed reduction analysis; Trimetallic catalysts; XRD, Atmospheric movements; Atmospheric pressure; Catalysis; Catalysts; Cerium; Cerium compounds; Crystalline materials; Electric conductivity; Manganese; Metallic glass; Methane; Negative ions; Oxygen; Silica; Sodium; Tungsten, Manganese oxide
DOI: 10.1016/j.catcom.2007.09.026
Oxidative coupling of methane conversion (OCM) and C2 selectivity on Na2WO4-MOx/SiO2 catalysts, where M is V, Cr, Mn, Fe, Co or Zn are related to surface morphology, textural properties and reduction behavior of the catalysts. The catalysts are prepared by sequential impregnation of aqueous solution of metal salts and then sodium tungstate on the silica followed by drying and calcination at 800 °C for 8 h. Methane conversion increases with the transition metal compound of the catalysts in the order of V ∼ Cr ∼ Zn < Fe ∼ Co < Mn while the C2 selectivity enhances in the order of V ∼ Cr ≪ Fe ∼ Co ∼ Zn < Mn. XRD and SEM results reveal some interactions between the V and Cr oxides and silica support, decreasing the tungstate peaks intensities and deteriorating catalyst bulk properties and both OCM conversion and selectivity. Both silica and Mn, Fe, Co and Zn transition metals, however, interact with sodium tungstate, forming an OCM selective catalyst. TPR analyses combined with the XRD and SEM results show that the metal-metal and metal-support interactions, which take place due to the presence of sodium ion, depend on the transition metal that in turn affect catalyst performance. Moderation of the transition metal-tungstate interaction is proposed as the main chemical role of sodium ion in these series of catalysts. Results reveal that this interaction improves the redox properties of catalyst, which are related to the transition metals, forming a selective catalyst. © 2007 Elsevier B.V. All rights reserved.
AUTHOR KEYWORDS: Alkali ions; OCM; Redox catalyst; Surface morphology; Transition metal oxide
INDEX KEYWORDS: Catalyst selectivity; Methane; Oxidation; Reaction kinetics; Surface morphology, Alkali ions; Methane conversion; Oxidative coupling; Redox catalysts; Transition metal oxide, Catalyst activity
DOI: 10.1016/S1003-9953(07)60037-1
Modification and performance of Li induced silica phase transition of (Mn+W)/SiO2 catalyst, under reaction conditions of oxidative coupling of methane (OCM), have been investigated employing textural characterizations and redox studies. Stability and precrystalline form of fresh Li induced silica phase transition catalyst depend on the Li loading. A catalyst, with high lithium loading, destabilizes on OCM stream. This destabilization is not due to Li evaporation at OCM reaction conditions, a-cristobalite is proposed to be an intermediate in the crystallization of amorphous silica into quartz in the Li-induced silica phase transition process. However, the type of crystalline structure was found to be unimportant with regard to the formation of a selective catalyst. Metal-metal interactions of Li-Mn, Li-W and Mn-W, which are affected during silica phase crystallization, are found to be critical parameters of the trimetallic catalyst and were studied by TPR. Role of lithium in Li doped (Mn+W)/SiO2 catalyst is described as a moderator of the Mn-W interaction by involving W in silica phase transition. These interactions help in the improvement of transition metal redox properties, especially that of Mn, in favor of OCM selectivity. © 2007 CAS/DICP.
AUTHOR KEYWORDS: intermetallic interaction; lithium; oxidative coupling of methane; redox properties; silica phase transition
INDEX KEYWORDS: Characterization; Crystallization kinetics; Intermetallics; Lithium; Phase transitions; Redox reactions; Silica, Intermetallic interaction; Oxidative coupling, Methane
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