Iranian Journal of Chemistry and Chemical Engineering
Volume:37 Issue: 5, Sep-Oct 2018

In the present study, Nickel-Copper nanoparticles were electrodeposited on glassy carbon electrode (GCE) by using electroplating deposition method. The prepared electrode was characterized by scanning electron microscopy (SEM) and elemental mapping analysis. Results showed that Ni-Cu nanoparticles with a high density are distributed at the surface of the glassy carbon electrode. Subsequently, this electrode was applied for ethanol electro-oxidation using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques. The results of voltammograms showed high catalytic activity, increased the oxidation peak current density at the low potential for ethanol electrooxidation on Ni-Cu/GCE. Study of the electro-oxidation mechanism by the effect of scan rate for ethanol on Ni-Cu /GCE indicated that the oxidation process is controlled by diffusion processes. Chronoamperometric measurements illustrate that Ni-Cu/GCE exhibits a steady state activity for ethanol electro-oxidation. EIS measurements showed that the diameter of semi-circle for Ni-Cu/GCE is greatly smaller than the bare GCE. The modified electrode is a good candidate as an anode for application in direct ethanol alkaline fuel cells.

The goal of this work is the separation and recovery of platinum and palladium from spent catalyst. The recovery consisted of separating the maximum amount of platinum and palladium from catalysts and changing them into usable forms. The petroleum and petrochemical units use Pt and Pd catalyst for reactions such as reforming and hydrogenation. Because these materials contain valuable metals, such as Pt and Pd, these metals should be recycled. Based on economic reasons and the high price of new catalysts, petrochemical companies should solve this problem. The new method in this work may help to recover these metals from spent catalyst. This method may help solve several environmental problems. In this work, the recovery of platinum and palladium from petroleum catalysts has been studied using spent catalysts. Two catalysts were characterized by XRF, XRD, and AAS. Aqua regia, used as a leaching agent, and the effect of dissolution temperature and time, Liquid/Solid (L/S) ratio, size of particles, and elimination of coke were also investigated. Under optimized conditions, the leaching process was done with 98% efficiency. Recovery of platinum and palladium from the leached solutions was done by the adsorption process with Activated Carbon (AC) in an environmentally friendly manner. According to the results, the optimum operating conditions for platinum and palladium removal by activated carbon were a temperature of a solution of 85 and 98℃, pH = 0.5 and 2, time of adsorption 180 and 150 min and adsorbent loading capacity = 18.75 mgPt/gAC and 12.5 mgPd/gAC, respectively. The activated carbon containing platinum and palladium was decomposed by ignition to produce platinum and palladium powder with commercial purity of 96.5% and 96.3% respectively.

The total oxidation of toluene at a wide temperature range (200–500 oC) over micro/mesoporous platinated catalysts has been investigated about activity, selectivity to CO2 and CO, catalyst's stability versus coke deposition and reaction kinetics. Kinetic of toluene oxidation was measured under various oxygen and toluene pressures and also the effect of the reaction conditions on the catalytic performance was studied. For more study, two kinetic models have also been selected and tested to describe the kinetics for this reaction. The results show that the Langmuir-Hinshelwood model provides a good fit for the experimental data. The obtained results showed that Pt/HZSM-5(30)-HMS have a better ability than other catalysts for the oxidation reaction of toluene, such as maximum toluene conversion (>97%), high selectivity to CO2 (100%), good catalytic stability against coke deposition and appropriate kinetic parameters

A green and convenient method for the synthesis of 2-amino-3-phenylsulphonyl-4H-chromenes by a one-pot three-component condensation of 1-naphthol, phenylsulphonylacetonitrile and aromatic aldehydes under solvent-free conditions using potassium phosphate tribasic trihydrate as an efficient catalyst is described. The reaction of 1-naphthol with phenylsulphonylacetonitrile and various aromatic aldehydes was carried out under solvent-free conditions at 100 °C using 10 mol% of potassium phosphate tribasic trihydrate as a catalyst. The results show that aromatic aldehydes containing electron-donating groups or electron-withdrawing groups could react smoothly to give the corresponding products in good to excellent yields. It was also found that potassium phosphate tribasic trihydrate can be recycled at least four times without loss of activity. High yields, short reaction times, ease of handling, cheap and reusable catalyst, mild and environmentally begin reaction conditions are the advantages of this procedure.

An efficient and convenient method for synthesis of 2,6-bis (4-(dialkylamino) styryl)-4H-pyran-4-one starting from 4- (dialkylamino) benzaldehyde with 2,6-dimethyl-4H-pyran-4-onein the presence of MeONa as the base was described. Additionally, preparation of novel compounds with bis-DCM-type skeleton for application in organic light-emitting diodes was developed via reaction of malononitrile as active methylene group with 2,6-bis (4-(dialkylamino) styryl) -4H-pyran-4-one derivatives. 1H and 13C NMR, FT-IR spectroscopy supported the predicted structure of the products. The UV-Vis absorption spectra of synthesis compound were measured in diluted dichloromethane solution. Maximum absorption (lmax) values differ from 460 to 496 nm, this absorption is due to π-π* transition.

Charge Transfer (CT) complexes formed between dibenzo-24-crown-8 (DB24C8) as an electron donor with the σ-electron acceptor iodine (I2) in chloroform, dichloromethane, and 1,2-dichloroethane solutions have been studied by different spectroscopic techniques at room temperature. The spectral studies of the complexes were determined by UV-Visible, Fourier Transform InfraRed (FT-IR) Studies on the system showed the time dependence of the absorption band of the complexes. The observed time dependence of the charge-transfer band and subsequent formation of I3¯ in solution were related to the slow transformation of the initially formed outer complex to an inner Electron Donor-Acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form three iodide ion. Formation constants of the resulting complexes were determined by measuring the absorbance at lmax for a series of solutions with varying excess amounts donor and constant iodine concentration in solvent systems used. The reaction stoichiometry was found to be 1:1 (donor : acceptor) molar ratio for both complexation system by using photometric titration measurements. The formation constant (KCT), molar extinction coefficient (eCT), free energy change (DG0), CT-energy (ECT), were calculated by using the Benesi-Hildebrand method. Stability of the resulting complex in three solvents was also found to vary in the order of 1,2 -DCE >DCM> CHCl3.

In this study, two new salicylideneaniline derivative compounds which are an isomer of each other have been synthesized and characterized by X-Ray Diffraction (XRD) technique, IR spectroscopy, and theoretical method. While (E)-4-(dihydroxyamino)-2-(((4-fluorophenyl)imino) methyl)phenol (1), crystalizes triclinic P-1 space group, (E)-4-(dihydroxyamino)-2-(((3-fluorophenyl)imino)methyl)phenol (2) crystalizes monoclinic P21/c space group. Both of the molecules which adopt (E) configuration with respect to the central C=N bond have strong intermolecular O―H∙∙∙N hydrogen bonds. These O―H∙∙∙N hydrogen bonds create S(6) motifs according to graph set notation. The optimized geometries of the molecules have been calculated by using Density Functional Theory (DFT) with the 6-31G(d,p) basis set. Molecular Electrostatic Potential (MEP) map and Frontier Molecular Orbitals have been made for the optimized geometries. In addition to these studies, the theoretical IR spectra of the compounds, the experimental IR spectra of which have been recorded at 4000-400 cm-1 interval, have also been calculated with same level theory. The experimental and theoretical results were compared to each other.

In order to improve the traditional freezing crystallization process of calcium nitrate in nitric phosphate process, crystal growth experiments by adding Ca(NO3)2·4H2O seeds in supersaturated calcium nitrate solution in a Circulating Fluidized Bed (CFB) crystallizer were carried out on crystal growth kinetics. The results showed that the growth of Ca(NO3)2·4H2O crystals is a complicated mass transfer process. The mean mass crystal growth rate (RG) of Ca(NO3)2·4H2O increased linearly with the fluid circulated velocity at fixed relative supersaturation and enlarged with relative supersaturation increasing. The crystallization kinetics follows the first order equation. The overall activation energy and the order of the overall growth kinetics of Ca(NO3)2·4H2O crystals were calculated by the isothermal method. The RG of Ca(NO3)2·4H2O crystals remains basically stationary within the entire crystallization time in the CFB crystallizer. The results have a deep significance to exploit a new CFB crystallization process for the production of Ca(NO3)2·4H2O crystals instead of the traditional one.

Many modern launch vehicles use unsymmetrical dimethylhydrazine (UDMH) as liquid fuel in the space program. UDMH is highly toxic and poses a serious threat to the environment and to humans. One of the most effective methods of UDMH neutralization in case of fuel spills is adsorption. This paper is the first to suggest using hydrolysis lignin as rocket fuel adsorbent. The research was based on the use of ion chromatography with amperometric detection and gas chromatography-mass spectrometry methods. The adsorption experiment resulted in finding the conditions that correspond to the residual UDMH concentration that does not exceed maximum permissible concentration in water. Also, it was investigated the effect of moisture content of hydrolysis lignin and ambient temperature on the dynamics of UDMH adsorption from the gaseous phase. We determined the kinetic and thermodynamic parameters of the adsorption process. It was demonstrated that the reaction between 1,1-dimethylhydrazine and active adsorbent centers (carbonyl and carboxyl groups) is close to the first order. The value of activation energy (85.9 kJ/mol) corresponds to that of chemisorption.

Inhibition performances of imidazoline derivatives with different alkyl chain length for carbon steel in H2S acid solutions has been studied by polarization curves, AC impedance measurements, current transient, Atomic Force Microscopy (AFM) and Density Functional Theory (DFT) techniques. Results showed that the inhibition occurs through adsorption of the inhibitors molecules on the metal surface. The inhibition efficiency was found to increase with increasing inhibitor’s concentration. Polarization data indicated that these compounds act as mixed-type inhibitors. Computational studies of investigated inhibitors were performed by using Hartree–Fock (HF) and M062X methods which are ab-initio and DFT methods with 6-31G basis set in the gas phase and water. Calculated results indicate that the inferred inhibition efficiency increases with the increasing alkyl chain length, which is well in accordance with reported experimental results.

Leaching of a low-grade lead and zinc oxide ore was studied by an organic reagent, citric acid. The quadratic mathematical models were developed for the relationship among the influential parameters and lead and zinc recoveries. Leaching rate was strongly affected by the interactive effects of factors. It was also found that the quadratic effects of stirring speed and linear effects of temperature have the most significance on the leaching rate of zinc and lead, respectively. It was found that the center level of influential factors was a good condition for getting higher zinc leaching rate, whilst, for the leaching of lead the extreme levels of factors were good. Additionally, the proposed models were optimized using the quadratic programming method to maximize recoveries. The highest recoveries of zinc and lead were achieved to be about 94 and 78 %, respectively.

Novel magnetic biochar has been successfully synthesized by using microwave technique, using discarded materials such as Empty Fruit Bunch (EFB). The optimized conditions for the best novel magnetic biochar synthesis are at 900 w reaction power, 20 min reaction time, and impregnation ratio 0.5 (biomas:FeCl3) The details physical and chemical analyses of novel magnetic biochar were found to be in good agreement with the hypothesis. These newly produced magnetic biochars have a high surface area 890 m2/g and that leads to highly efficient in the removal of arsenic (87%) from aqueous solution. As for new invention, magnetic biochar can be directly produced using microwaves heating by a single stage of activation compared to the conventional method.

In this study, different amounts of MoS2 particles and an anionic surfactant were added to the conventional chromium electroplating bath in order to electrodeposite crack-free chromium coatings and the structure, morphology, tribology and corrosion behavior of the deposited coatings were investigated using X-ray diffraction spectroscopy, scanning electron microscopy, pin on disk wear test method, dynamic polarization, and electrochemical impedance spectroscopy techniques, respectively. The results showed that the incorporation of MoS2 particle into the electrodeposited Cr coatings is impossible and no chromium coating can be electroplated from baths containing more than 5 g/L MoS2 particles. In addition, as the MoS2 concentration in the bath increases up to 1 g/L the corrosion and wear resistance of the deposited coatings increases. Moreover, those coatings that were electroplated from the baths containing more than 1 g/L exhibited less performance regarding their corrosion and wear behavior.

The electrochemical oxidation behavior of m-nitrophenol (m-NP) was studied comparatively on glassy carbon electrode, Pt electrode, PbO2 electrode, SnO2 electrode, and graphite electrode using cyclic voltammetry. The cyclic voltammetry measurements were performed in acidic (1 M H2SO4, pH 0.4), neutral (1 M Na2SO4, pH 6.8), and alkaline (1 M NaOH, pH 12.0) media to investigate the effect of pH value on the oxidation of m-NP. The fouling of electrodes was also studied during cyclic voltammetry measurements. The results indicate that both of the electrode material and the pH value of supporting electrolyte had a significant influence on the oxidation of m-NP. In acidic medium, m-NP was irreversibly oxidized on glassy carbon electrode, Pt electrode, SnO2 electrode, and graphite electrode at 1.23, 1.26, 1.26 and 1.27 V, respectively, while there was no any oxidation peak for PbO2 electrode. In a neutral medium, m-NP yielded well-defined oxidation peaks on all electrodes, although the height and potential of the peaks depended on the material of electrodes. In the alkaline medium, the m-NP could be directly oxidized only on glassy carbon electrode and graphite electrode, but their peaks were not well defined because the oxidation of m-NP occurs closer to oxygen evolution potential region. In addition, the oxidation peaks appeared at the lower potential value in the alkaline medium than in neutral and acidic media. Under all conditions, except in the alkaline solution and on glassy carbon electrode, the passivation of electrodes occurred during continual scans.

In the present study, we investigated the ability of an immobilized phospholipase A1 (PLA1) in degumming of soybean oil. The enzyme was immobilized by simple adsorption on bentonite without any further modification. The free and immobilized PLA1 were characterized by Fourier Transform InfraRed (FT-IR) spectroscopy and X-Ray Diffraction (XRD). The immobilization of PLA1 lowered the Energy of Activation (EA) from 155.64 to 27.13 kJ/mol, resulting in higher catalytic efficiency of PLA1. Thermal stability of the immobilized enzyme was found to be higher compared to free PLA1. Moreover, under the condition of pH 5.5 and T = 50 °C, the phosphorus content was reduced to less than 10 ppm after 4-5 h for free PLA1 and after 7 h for immobilized PLA1.

In this study, the oil contents, fatty acid composition and tocopherol contents of sesame seed and oils belong to different countries were determined. The oil contents of materials changed between 49.22% (India) and 56.16% (Nigeria-Kanu). The major saturated fatty acids in sesame seed oils were palmitic (6.06-9.03%), stearic (5.29-6.42%) acids with small 20:0 (0.19-0.71%) acids. The main unsaturated fatty acids of sesame oil samples were linoleic (38.11-47.11%) and oleic (36.83-44.49%) acids. There was a significant difference in the amounts of the major fatty acids in the oil samples (P<0.05). The oils extracted from the Sesamum seeds were composed of 18.51-49.63 mg /100g γ-tocopherol, 0.134 mg/100g α-tocotrienol (India) and 0.415 mg/100g γ-tocotrienol (India). Total contents of tocopherol of samples ranged from 18.508 mg/100 g (Nigeria (Benue)) to 49.630 (Turkey (Mersin)).

Ohmic heating is defined as a process which alternating electric current is passed through food with the primary purpose of heating it due to the electrical resistance and can be specially applied as an alternative heating method. In this research, Aloe vera gel concentrates having 0.5-2% soluble solids were ohmically heated up to 60°C by using four different voltage gradients (30–60 V/cm). The dependence of electrical conductivity on temperature, voltage gradient, and concentration were obtained. Results indicated that there was a linear relationship between temperature and electrical conductivity. The range of the electrical conductivity was 0.45 to1.20 S/m, which was dependent on the concentration and voltage gradient, although the effect of concentration was very higher than voltage gradient. The ohmic heating System Performance Coefficients (SPCs) were calculated by using the energies given to the system and taken by the Aloe vera gel samples and were in the range of 0.67- 0.89 and the highest SPC (0.89) was observed at 0.5 % and 30 V/cm.

Laser Doppler Velocimetry (LDV) has been employed to determine pseudo-turbulence characteristics of the flow field around bubble train forming in non-Newtonian caboxymethylcellulose (CMC) aqueous solution at low gas flow rate condition. The Reynolds stress and turbulent intensity of the liquid were investigated by means of Reynolds time-averaged method. The experimental results show that axial Reynolds stress rises greatly and then fluctuates slightly with the vertical height, whereas displays symmetrical Gaussian distribution in the horizontal direction; Radial Reynolds stress changes nonobviously in the vertical direction, but increases followed by a decrease in the horizontal direction. The axial turbulent intensity begins to wave to some degree with the height for near vertical axis passing through orifice center, but maintains constant within bubble channel in the horizontal direction; Radial turbulent intensity gets down with the vertical height, compared with the opposite trend of its variation with the horizontal distance.

Traditionally water-ethylene glycol mixture based nanofluids are used in cold regions as a coolant in the car radiators. In the present study, the rheological properties of water-ethylene glycol based graphene oxide nanofluid are studied using Non-Equilibrium Molecular Dynamics (NEMD) method at different temperatures, volume concentrations, and shear rates. NEMD simulations are performed with considering 75/25, 60/40, and 40/60 ratios of water/ethylene glycol as the base fluids at volume concentrations of 3%, 4%, and 5% graphene oxide nanosheets. The results, which demonstrated good agreement with experimental data, show that the viscosity and density of base fluids significantly decrease with temperature and increases with ethylene glycol volume fraction. Also, the viscosity and density of nanofluids depends directly on the volume concentrations of nanoparticles and decreases with increasing temperature. For example, at 289.85 K, the viscosity of water (75%)-ethylene glycol (25%) based nanofluids containing 3%, 4% and 5% volume concentrations of nanoparticles increased by 33%, 43%, and 56%, respectively. Similarly, the density of the same nanofluids increased by 1%, 1.7 %, and 2.2%, respectively. Moreover, the theoretical models confirm the obtained results. According to the shear rate analysis, the water-ethylene glycol based graphene oxide nanofluid behaves as a non-Newtonian fluid.

In this work, a Genetic Algorithm boosted Least Square Support Vector Machine model by a set of linear equations instead of a quadratic program, which is improved version of Support Vector Machine model, was used for estimation of 98 pure compounds second virial coefficient. Compounds were classified to the different groups. Finest parameters were obtained by Genetic Algorithm method for training data. The accuracy of the Genetic Algorithm boosted Least Square Support Vector Machine was compared with four empirical equations that are well-known and are claimed can predict all compounds second virial coefficients (Pitzer, Tesonopolos, Gasanov RK and Long Meng). Results showed that in all classes of compounds, the Genetic Algorithm boosted Least Square Support Vector Machine method was more accurate than these empirical correlations. The Average Relative Deviation percentage of overall data set was 2.53 for the Genetic Algorithm boosted Least Square Support Vector Machine model while the best Average Relative Deviation percentage for empirical models (Tesonopolos) was 15.38. When the molecules become more complex, the difference in accuracy becomes sharper for empirical models where the proposed Genetic Algorithm boosted Least Square Support Vector Machine model have predicted good results for classes of compounds that empirical correlations usually fail to give good estimates.

In this paper, the effect of ultrasonic pre-treatment and aeration on the flotation separation of chalcopyrite from pyrite was investigated at different amounts of potassium ethyl xanthate (KEX), as a collector, and pH values. Artificially-mixed samples of chalcopyrite and pyrite were subjected to flotation studies to understand the effect of aeration with or without ultrasonic treatment on the flotation behavior of the minerals. Results of laboratory micro-flotation tests indicated that joint aeration and ultrasonic treatment makes it possible to separate chalcopyrite from pyrite effectively. X-ray Photoelectron Spectroscopy (XPS) confirmed the existence of negligible amounts of hydroxide/oxide species, which are resulted from galvanic interactions, on the surfaces of the minerals after conditioning of the suspension by ultrasound waves. The effective separation of chalcopyrite from pyrite was attributed to desorption of metal hydroxide precipitates, as hydrophilic species, from the surface of the chalcopyrite by ultrasonic treatment.

Combined heat and power systems are becoming more and more important, regarding their enhanced efficiency, energy saving, and environmental aspects. In the peresent study, three configurations of combined heat and power systems are intended as an alternative to separate production plant by considering environmental aspects. First and second laws of thermodynamics are adapted to the operating data. The energy and exergy indicators, their distribution and exergy loss are evaluated. The economic analysis was done by determining the Rate of Return on Investment, Payback Period and Net Present Worth. The optimal configuration of system equipment has been determined based on economic feasibility and emission saving in view of power and steam demand. The method employed here may be applied to making a decision on the adoption of the combined plant to any separate heat and power systems.

A lot of recent research in the biomass sector is focusing on how to improve the efficiency of biomass resources. Pretreatment of biomass resources is a novel approach and has gained a lot of attention in the last decade. A review of modern methods and the latest technologies of enhancing the enzymatic saccharification of sugarcane bagasse are presented in this work. This paper looks at the very recent developments in this field. Use of such advanced methods as coupling ionic liquid pretreatment with supercritical fluids and ultrasound irradiation is taking us swiftly towards the ultimate goal which is achieving 100% yield at minimum cost with no adverse environmental effects. However, Optimum process conditions for these methods are yet to be discovered. There is a need to optimize the processes and learn completely about the reaction mechanism in order to shift from lab scale to pilot scale and ultimately to the industrial level. An effort is made to report the latest work and because of it, this paper contains about 95% citations from papers within the last five years. In the end, useful recommendations are given in the conclusion section.

The aim of this study is to design a new mathematical model biomass product with the help of the gasification reactor. This design will help in describing most of the internal parameters inside this process. This research also aims to study and analyze the kinetic reaction, mass and heat transfer for four zones of the gasification reactor. It has been found that the char concentration from zone one is almost 42% consumption and from zone three to four, the consumptions have found to be 72.06%. It means that the char conversion depends on oxygen consumptions in all zones to produce volatility gases, methane, and hydrogen. The mathematical model will help in optimizing best possible conditions so as to give a high quality product of methane and hydrogen to 2.2 kmol/m3 and 3 Kmol/m3 respectively. Thus, it appears to be important that important parameters of a chemical reaction are studied. Furthermore, all thermodynamic parameters of the reaction must be analyzed so as to optimize the best conditions through gasification reactor.