Nashrieh Shimi va Mohandesi Shimi Iran
Year:2019 | Volume:37 | Issue:4 (90) |Papers Count:27

IIn this paper, the results of the structure and magnetic properties of Fe/Al/Fe multilayers were prepared on monocrystalline Si were investigated. Thin films were obtained by RF Magnetron Sputtering Method (RF-MSM). The results of XRD analysis show that the preferred direction of Fe/Al/Fe multilayers is oriented (200). Then, the thermal behavior of samples in high temperatures in vacuum was studied using HT – XRD analysis between 26° C-800° C at 180min. Finally, the morphology of surface, gin sized and magnetic properties were studied using AFM, MFM, and AGFM analysis, respectively.

In this study, the effects of the aromaticity on electronic properties of single-walled Boron Nitride Nanotubes (BNNTs) have been studied along with tension. The geometries were optimized at the B3LYP/6-31+G(d) level. In the axial tensile process, the B and the N atoms within two atomic layers at both ends of BNNTs were kept fixed, whereas the remaining layers were relaxed during the calculations. The values of the bandgap, binding energies, electronic chemical potential, chemical hardness, and electrophilicity index have been calculated. The Nucleus-Independent Chemical Shielding (NICS), Harmonic Oscillator Model of Aromaticity (HOMA), Harmonic Oscillator Model of Electron Delocalization (HOMED) and Para-Delocalization Index (PDI) have been calculated to quantify aromaticity in terms magnetic, structural and topological criteria. Our results indicate that the HOMED index is appropriate for determining the aromaticity of single-walled zig-zag BN nanotubes. Also, the aromaticity of these nanotubes decreases with the increase of axial strain. A reverse correlation is observed between aromaticity and conductivity of nanotubes along tension.

Phenolic compounds are among of current pollutants of water resources. Photodegradation by using semiconductor nano photocatalyst is an effective and practicable method for the removal of these compounds. In this research, Sb/TiO2-Fe3O4 nano photocatalyst with 0 to 10 %w/w Sb was successfully synthesized and their structure was characterized by FT-IR, XRD, SEM methods. The size of synthesized particles was calculated using the XRD pattern and Scherrer equation which is accordant to the average size of nanoparticles observed in SEM images that were about 50 nm. Furthermore, the effects of various parameters including the initial pollutant and antimony concentrations, temperature, pH and the amount of catalyst were investigated. The phenol and 4-nitrophenol were degraded 70. 1% and 95% with Sb/TiO2-Fe3O4 (5 %w/w Sb), respectively.

In this research, ZnO-Cr nanoparticles loaded on active carbon were used for the removal of disulphine blue dye. The influence of variables such as the amount of adsorbent, initial concentration of dyes, pH and stirring time on removal percentage were optimized and investigated by central composite design. The kinetic models, adsorption isotherms and thermodynamic parameters also reviewed, and the ability to use in the optimal conditions assessment. After analyzing the results and compared the optimal points, for ZnO-Cr nanoparticles loaded on active carbon, removal percentage of disulphine blue 98. 70 respectively. Finally, the adsorption process was modeled by the artificial neural network. In this study, time, the amount of absorbent, pH, the concentration of dye as the network inputs and removal percentage of dyes is considered as network targets. In the modeling removal of dye processes by the artificial neural network, neuron 15 as the optimum neuron was chosen in the removal of disulphine blue. The mean square errors in the optimal neuron for the process of adsorption using ZnO-Cr nanoparticles loaded on active carbon 7. 17×10-5 respectively obtained that numerical is close to zero, also according to the calculated AAD% values in the model the results show that the artificial neural network model is more in agreement with experimental data is compared to the response surface methodology.

Taguchi model is a model for the analysis of experiments, that predicts both the effects of each factor and the optimum level of them using a certain number of experiments. The purpose of this study was the optimization of Cd(II) ions adsorption on the cobalt oxide using the Taguchi model. The characterization of synthesized cobalt oxide was investigated by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transfer InfraRed (FT-IR) spectrometry and X-Ray Diffraction(XRD). In this experimental study, the cobalt oxide was prepared in a few steps. Then, 4 main factors (i. e. temperature, amount of absorption, contact time and pH) on 4 levels were selected by Matrix L25 trials and the experiments were conducted in this matrix. Finally, the adsorption of Cd(II) on cobalt oxide was determined in optimal conditions. The optimization of the adsorption process using the Taguchi model showed that the factors of importance for optimizing respectively were: contact time of 20 minutes, pH =8, temperature=15 ° C and adsorbent dosages of 25 mg. The maximum adsorption in optimal conditions was determined 96/21.

The separation of thorium and uranium ions in radioactive waste is one of the important and complex processes in the management and storage of radioactive waste in the nuclear industry. One way of removing radioactive materials from nuclear waste is by means of natural adsorbents. In this study, natural zeolites of Firoozkooh and Tabrizhave been prepared and identified with the FT-IR, XRD, BET, and XRF methods. The results showed the Clinoptilolite and Ferrocarpholite structure with an average particle size of 30, 38. 7 nanometer, and a specific surface area of 28. 51 and 4. 78 m2/g for Firoozkooh and Tabriz zeolites, respectively. The effects of different variables such as pH, time of contact between the exchanger and solution, initial concentration of ions and the amount of adsorbent were investigated and optimum conditions for separation of these ions were determined. The maximum adsorption of thorium ions on both adsorbents under optimum experimental conditions was observed at 25 mg/L, pH=4, 240 min. and weight of 0. 1 g, 96. 93% and 96. 77%, and for uranium ion, the maximum adsorption was at 25 mg/L, pH=4 for Firouzkohe zeolite and pH=5 for Tabriz zeolite, 240 min. contact time, 0. 1 g weight, 93. 01% and 52. 68% respectively by zeolites of Firouzkooh and Tabriz, which increased the mass of zeolite in Tabriz up to 0. 3 g, the highest uranium uptake reached 83. 65%.

In this research, in order to obtain the clean gasoline, a new nanocomposite, TBA-FePOM@NiO was synthesized via the sol-gel method and tested as a catalyst for oxidative desulphurization (ODS) of gasoline. The nanocomposite was successfully prepared by reaction of mono Fe-substituted polyoxometalate [N(CH3)4]4PW11FeO39 (hereinafter TBA-FePOM) and nickel oxide (NiO). The incorporation of the materials was confirmed by FT-IR، XRD، UV-Vis and SEM. The catalytic activity of nanocomposite was tested on real gasoline fuel in the presence of CH3COOH: H2O2 as an oxidant system. The results are compared with the oxidation process of prepared model sulfur compounds at the same conditions. The obtained results show that the nanocatalyst to be able to have oxidative desulphurization of gasoline with high yield. The synthesized heterogeneous nanocatalyst could be separated and recycled successfully after five times. in this study main factors such as temperature, time of reaction and dosage of catalyst were investigated.

In this study, novel xanthan-graft-itaconic acid (XG-g-IA/clay) composites hydrogels were synthesized by the incorporation of three types of clay (montmorillonite, bentonite, and kaolinite) for adsorption of Cu2+ from aqueous solution. The results of the spectroscopy of the infrared Fourier transform before and after the adsorption process proved the contribution of clay and monomer of itaconic acid to the composite hydrogel. It also showed that carboxylate groups play a significant role in absorbing copper cations from aqueous solutions. The results of SEM results showed that the nonuniform structure of the adsorbent surface became smoother after the absorption of copper cations. The Intercalation of the nanoparticles in the polymer matrix and increasing the surface area were determined by X-ray diffraction and BET tests, respectively. The isotherm results showed that the equilibrium data followed Langmuir isotherm with the maximum adsorption capacity of 133. 62, 131. 96 and 125. 68mg/g for XG-g-IA/BT, XG-g-IA/MMT and XG-g-IA/KT hydrogel composites at 45° C and pH=5, respectively. The experimental data of all three synthesized hydrogels were fitted well with the second-order kinetic model. The negative values of standard Gibbs free energy and the positive values of standard entropy confirmed that the adsorption process is spontaneous and feasible, respectively.

In this research, nickel acetate/polyvinyl alcohol (Ni(OAc)2/PVA) nanofibers were prepared by the electrospinning method. In the following, nickel oxide nanofibers (NiO NFs) were obtained by appropriate heat treatment. The surface morphology and diameter of the synthesized nanofibers were investigated by Scanning Electron Microscopy (SEM). The results showed that long fiberswith an average diameter of around 90 nm were obtained for NiO NFs. By using Thermo Gravimetric Analysis (TGA), the appropriate temperature for calcination was obtained at about 600 ° C. The Fourier Transform-InfraRed (FT-IR) spectroscopy showed that all the organic constituents of the electro-spun NFs were removed after calcination. For the investigation of the crystallinity of the nickel oxide NFs, X-Ray Diffraction (XRD) was used. The crystalline phase of the NiO NFs was determined as cubic. The surface area of the NiO NFs was estimated at about 4. 2 m2 g-1 using adsorption-desorption isotherms (BET). The electrochemical behavior of NiO NFs modified Carbon Paste Electrode (CPE) was studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry methods. The electrocatalytic activity of the modified electrodes was studied towards oxidation of ethylene glycol (EG), ethanol and methanol in alkaline medium and the obtained results showed that the catalytic current density for the NiO NFs/CPE towards EG oxidation is more than other alcohols.

Among the various processes for the separation of impurities from natural gas, adsorption by solid adsorbent because of the simplicity of the process, low cost and also capability to achieve the high purity gas, have been considered. The SAPO-34 adsorbent as a molecular sieve has pores the same as CO2 and larger than CH4, so this causes high CO2 separation from the natural gas. In this study, SAPO-34 has been modified by H3PO4 at various operating conditions in order to maximize removing of carbon dioxide from the natural gas. Modifications can change the Si/Al ratio of SAPO-34 that is leading to a change in the acidity of adsorbent via the ion exchange process. These changes have been analyzed by various techniques such as EDX, SEM, XRD, and BET. The effects of temperature and pressure on separation have been verified at 5, 20 and 35 ° Ϲ and 3, 5 and 7 bar, respectively. The results indicated that by increasing pressure and decreasing temperature, the amount of adsorption is increased, but at very low temperatures and very high pressures, this trend was slightly reversed. Finally, by applying the design of experiments the temperature of 17. 4 º C and pressure of 4. 6 bar represented the highest yield for removing CO2 from natural gas (95%).

An attempt was made to investigate the capability of an aqueous solution of monoethanolamine (MEA) and 1, 3-diaminopropane (DAP) for carbon dioxide absorption. The solubility of carbon dioxide (CO2) in aqueous solutions of 10wt% MEA+5wt% DAP and 12. 5wt%MEA+2. 5wt% DAP was measured over a temperature range of 313. 15 to 333. 15 K and pressure ranging from 13 to 215 kPa using the pressure decay method. The measure solubility data have been presented as equilibrium partial pressure of CO2 against loading. Results showed that the solubility of CO2 increases by decreasing temperature at constant pressure and also increasing pressure at a constant temperature. Also, the solubility of CO2 increases by increasing the concentration of DAP in aqueous solution. It can be concluded that DAP improves the solubility of CO2 and can be presented as a new additive. with the use of Gibbs-Helmholtz equation Heat of reaction calculated and results showed increasing DAP decreased heat of reaction.

In this research, the effect of Ni loading on the structural and catalytic properties of the Ni/10%Sr-Al2O3 catalyst prepared by the wet impregnation method was studied in dry reforming of methane. The samples were characterized by X-Ray Diffraction (XRD), N2 adsorption, temperature-programmed reduction and oxidation (TPR, TPO), and scanning electron microscopy (SEM) techniques. The XRD results revealed that increasing Ni loading increased the NiO particle size. The BET results showed that the catalysts possessed a mesoporous structure and 5%Ni/10%Sr-Al2O3 catalyst exhibited higher surface area and CH4 and CO2 conversions compared to the other catalysts. It was found that the raise in Ni loading from 5 to 15 wt. %, increased the amount of deposited carbon which was in agreement with the results of SEM analysis. In addition, the long term stability of the 5%Ni/10%Sr-Al2O3 catalyst showed high stability during 13 h on stream at 650 oC.

In this work, two Platinum (II) and Palladium (II) complexes of 2, 2'-bipyridine (bpy) and diethyldithiocarbamate (Et-dtc) with anti-tumor activity against K562 were selected. The Cc50 values of Pd and Pt compounds are 55 and 89 micromolar, respectively that are lower than cisplatin. These complexes interacted with human serum albumin (HSA) in Tris-buffer containing 10 mM NaCl, pH=7. 4 at 27 and 37 ° C by spectroscopic methods. Results obtained from denaturation studies indicate that probably Pd(II) complex denature the HSA while the Pt(II) does not so. Isothermal titration data indicated that the stability of protein decrease by increasing complex concentration and the denaturation process is exothermic. Binding of these cationic complexes with HSA occurs by electrostatic interaction. These complexes can denature HSA at very low concentrations of the micromolar spatially platinum complex. Fluorescence studies showed the intensity of HSA quenched in the presence of each Pt or Pd complex and quenching mechanism seems to be static. Circular dichroism spectra of HSA were recorded and the percentage of alpha helicity in the presence of Pd and Pt complexes were investigated 5 and 3%, respectively.

In this study, the surface tension and surface coordination number of the molten metal using the Stephen equation calculated and reported. Parameters such as enthalpy of vaporization, density and surface tension of the parameters are required. Assumptions to predict the surface tension of molten metals such as minor changes in the volume of melting point similar to the melting point of the crystalline structure of liquid and solid, considering the increasing entropy, and no matter particles interact with particles in the second and third layers the surface is used. Results have shown that the surface coordination number of molten metal is in the range of 0. 3-0. 7 of bulk coordination number. As well as being dependent surface coordination number on different parameters, such as temperature and lack of uniformity in terms of the calculation of various metals has made it difficult to compare the surface coordination number numbers. Also, different equations have been used to correlate the coordination number and adjustable parameters reported.

The formulation of the fluid properties in terms of its affecting variables is important in the practical works that cannot be tested in the laboratory. In this work, the modified GMA equation of state which was developed with the (3, 6, 9) average intermolecular potential, has been used for the description of the behavior of the binary mixture. The application of the equation of state for some binary mixtures was investigated and the temperature dependence of its parameters in different mole fractions was determined. It is found that the parameters of the equation of the state obey the cubic mixing rule. The excess volume, excess internal energy and excess enthalpy of the studied mixtures were calculated in the different temperatures and mole fractions using the equation of state and compared with the experiment. Good compatibility of the predicted values with the experiment indicates the ability of the equation of state in the prediction of such properties. Furthermore, the existence of the common intersection point in the isotherms of the excess enthalpy of ethanol-methyl cyclohexane, cyclohexane-n-hexadecane, TEGME-HFC-134a, and propane-isobutenemixtures show that the temperature dependence of the excess enthalpy in this mole fraction is very low and consequently, the value of excess heat capacity in this mole is nearly zero. An expression was obtained for the mole fraction of the common intersection point that more experimental data needs to approve.

The energy crisis in recent years has to lead us to think about new sources of energy. Phase change materials are one of these efficient sources. They can be used as thermal insulators besides their heat storage applications. Also, implementing these materials has erased our need for immunization of energy consumption systems. Despite all the benefits, phase change materials have some limitations such as leaking problems and low thermal conductivity coefficient. Nanoparticles are therefore can improve their properties. In this study, the melting process of paraffin wax comprising nanoparticles of Al2O3, Fe2O3, SiO2 and ZnO (with weight fraction percentage 2% and 8%) in a rectangular container is simulated by Comsol software. Influence of nanoparticles with different weight fractions on temperature, velocity distribution, density, thermal conductivity coefficient and liquefy process are subsequently investigated. The results presented a 12. 5% increase in the thermal conductivity coefficient by adding 8wt% nanoparticles. The rate of melting process in 8wt% nanoparticles is bigger than that of 2wt% nanoparticles and pure paraffin with similar initial and boundary conditions for all states, which indicates that adding nanoparticles to paraffin for increasing the melting rate can be useful in various thermal management purposes such as storing energy.

Molecularly Imprinting Polymer (MIP)-coated A ZnO Quantum Dots (QDs) composite was introduced for selective determination of Aflatoxin B1 (AFB) as a template. The MIP layer was obtained by a simple method containing the self-assembly process of 3-aminopropyl triethoxysilane (APTES) monomers and tetraethyl ortho-silicate as a cross-linking agent. In order to create suitable sites in the polymeric matrix, AFB was applied as a proper template molecule. The inherent advantage of the MIP procedure is the great tendency of the prepared QDs toward the AFB molecules. The MIP-coated ZnO QDs displayed a potent fluorescence emission which could be quenched in the presence of AFB. This effect was exploited as the basis of a selective probe for the detection of AFB some water samples. In optimal conditions, a linear relationship between the emission intensity of prepared composite and concentration of AFB was obtained in the range of 0. 008-1 mg/L with a detection limit of 0. 003 mg/L. Linking the high selectivity of the MIP component with individual fluorescence features of ZnO QDs offers a sensitive and selective method for recognizing various toxic detection. The established method was satisfactorily applied for the determination of AFB contamination in environmental water samples.

This research is aimed to investigate the effect of crystallization parameters like cooling rate, seeding ratio, a cooling trend, and agitation intensity on the morphological properties of ammonium perchlorate crystals. A solution of AP was prepared by solving industrial grade ammonium perchlorate into the pure water and recrystallization was conducted using a 1. 3 L agitated batch crystallizer. The effects of the selected parameters were analyzed by applying Taguchi’ s method. Resulted crystals were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results indicate that the cooling rate has the greatest contribution to the roundness of the crystals and by optimization of the parameters, roundness and its standard deviation have been improved by 9. 4% and 79% respectively. Compared to the industrial crystals, the crystallinity of the resulted crystals was also substantially enhanced.

In this study, the dynamic evolution of water droplets size in crude oil due to aggregation and sedimentation phenomena are modeled by the Monte Carlo technique. The predicted results are compared to the NMR experimental data. The effect of type and concentration of emulsifier, water volume ratio, mixing rate and water salinity on the droplet size distribution are evaluated. The adequate agreement between the model results and experimental data reveals the model capability in the description of the aggregation and sedimentation processes in water/crude oil separation. The average size of water droplets is increased with a small rate at the initial period of the separation process. The probability of droplets collisions due to the random motion and sedimentation mechanisms are increased by increasing the size of the droplets. An increase in the aggregation among the droplets increases the average diameter of droplets evolution rate while the aggregation is decreased within a long time and the average size of droplets is approached to a steady value.

One of the most important issues in the world is the environmental pollution caused by toxic metals. Human activities such as the extraction of metals from mines, industrial wastes production led to the heavy metals accumulation in the environment that cause toxic effects on living organisms. On the other hand, the only way of environmental cleanup is metal removing, recycling and reusing, due to lack of metals biodegradability. For this purpose, the use of biological processes and microorganisms is one of the adopted solutions. Biological processes are based on interactions between microorganisms and metals. The identification of microorganisms resistant to metals plays an important role in the removal of environmental pollution. In order to survive, microorganisms can be resistant to heavy metals by different mechanisms as they contacted with metals. In this paper, the effects of toxic metals on microorganisms, resistance mechanisms, and applications of resistance mechanisms to metals such as bioaccumulation, biosorption, biotransformation, biomineralization and bioleaching of metals have been studied. The results illustrate that the use of microorganisms is a natural, sustainable and economical solution to recycle wastes and clean up the environment from heavy metals and could have a high percentage of valuable and toxic metals recovery and/or detoxification.

Investigation of electrical field effect on nanoparticles can be important in the electrochemical treatment of industrial and urban wastewaters contaminated by nanoparticles. Because the excessive presence of nanoparticles in the environment can be harmful to organisms and humans. The behavior of silver nanoparticles (AgNPs) under an applied electric field depends primarily on their stabilizing agent. This research is aimed at investigating the behavior of AgNPs and their stabilizers under the electric field, which called “ electrocoagulation” . Silver nitrate and hydrazine hydrate were used as the sources of silver ion and reducing agent, respectively. In separate experiments, sodium citrate and polyvinylpyrrolidone (PVP) were used as nanoparticle stabilizers. The stability of the particles was studied when an electrical current was applied with different voltages. The efficiency of the EC process was investigated for different of AgNP sols. With sodium citrate for different voltages, after using the electric field for 90min, the plasmon resonance peak of the sample disappeared, reflecting the removal of the AgNPs in the sol by 99. 91%. With PVP, by using different voltages of the EC, for10 min, the absorbance peaks disappeared, and removal efficiency of the AgNPs reached 99. 98%. Based on these results, it can be recognized that the AgNPs stabilized by citrate, are slightly more stable, whereas AgNPs solutions prepared by PVP showed better results on floc formation and, therefore, agglomerated more easily.

In this research, the mechanism of complex formation between the catechol with the nitrate and hydrogen sulfate through the hydrogen bond analysis has been investigated. All calculations have been performed by using the Gaussian09 software within the DFT-B3LYP functional and the 6/311++G(d, p) basis set. The thermodynamic parameters of the studied reactions have been fully calculated. NBO analysis showed a proper charge transfer through the H-bondsin complexes. The stabilization energies E(2) have been computed for these complexes and showed that the interaction energy for the HSO4-catechol complex is more than nitrate-catechol. Also, atoms in molecules, analysis has been done and electron density, Laplacian and the ratio of the kinetic energy density to the potential issue have been obtained. Based on this analysis, the electron density is maximum for the nitrate-catechol in the first step and for the HSO4-catechol in the second step. Quantum chemistry reactivity parameters of electronic chemical hardness, electronic chemical potential, and electrophilicity index have been investigated and the probable correlations have been analyzed.