Nashrieh Shimi va Mohandesi Shimi Iran
Year:2014 | Volume:33 | Issue:2|Papers Count:20

A facile and highly efficient method have been developed for the preconcentration of the mercury content in crude oil and gasoline samples after digestion with microwave-assisted digestion. Octadecyl silica membrane disk has been modified by the recently synthesized triazene ligand, (E)-1-(2-ethoxyphenyl)-3-(4-nitrophenyl) triaz-1-ene (ENT), then the modified membrane was used for the preconcentration of mercury (II) ions and Cold Vapor Atomic Absorption Spectrometry (CV-AAS) have been used to determine the Hg (II) ion. Solution studies of ENT with a series of metal ions have been done in advance, and the results showed a strong affinity of ENT to the mercury ion. For solid phase extraction, pH of sample 6.0, flow rates 3.0 mL / min, enrichment factor 240, capacity of modified disk 690 µg Hg per 8.0 mg of ligand, eluent solvent 5.0 mL, 1.5M HClO4, and the amount of the ligand 8.0–10.0 mg, have been optimized. A linear calibration curve has been obtained in the range of 0.80–65 mg / L with R2=0.9991 and the Limit Of Detection (LOD) based on three times the standard deviation of the blank was 0.25 mg / L. The Relative Standard Deviation (RSD) for the determination of 50 mL aqueous solution containing 0.5 mg / LHg (II) found to be 1.0 % while a RSD value of 1.9% have been obtained for the determination of 0.1 µg / L Hg (II) (n=3). The characteristic concentration is 1.2 mg / Lin the original samples. The newly developed method was successfully applied to the determination of mercury ion in real crude oil samples, which are very important in environment and industries process.

Ground state geometries have been computed using Density Functional Theory (DFT) at B3LYP/6-31G (d, p) level of theory. The excitation energies and spectroscopic parameters have been computed using Long range Corrected (LC) hybrid functional by Time Dependent Density Functional Theory (TDDFT) with LC-BLYP level of theory. The Polarizable Continuum Model (PCM) has been used for evaluating bulk solvent effects at all stages. The efficient materials have been predicted and electron injection (ΔGinject), electron coupling constant (|VRP|) and Light Harvesting Efficiency (LHE) has been discussed. By elongating the bridge all these three parameters ΔGinject, |VRP| and LHE enhanced which revealed that new designed sensitizers would be efficient.

Titanium dioxide is widely used in the manufacturing of paints, varnishes, lacquer, paper, paperboard, printing inks, rubber, floor covering, and ceramics and so on. White titanium dioxide pigment has been produced by two main processes. The sulfate and the chloride processes. Each of these two routes requires different feedstocks. However, economic and environmental pressures are shifting the world balance of titanium dioxide production away from sulphate based manufacture towards the more cost effective and cleaner chloride route. According to usage of titanium dioxide, the nano sized TiO2 was produced by the sulfuric acid and hydrocholoric acid leaching by using Sonochemical technique during the leaching process. No adding extra materials and no milling after precipitate, no vaporization during the leaching are advantages of this work which reduced the processes of leaching. All of determination techniques of particle size (Zeta Sizer, XRD, SEM, and TEM) prove this matter. The particles sizes of nano TiO2 which was leached by HCl and H2SO4 are 83 and 85 nm respectively.

In this work, CoFe2O4 nanoparticles have been prepared by co-precipitation technique. The synthesized CoFe2O4 nanoparticles were applied in the preparation of CoFe2O4/Polyacrylonitrile fiber nanocomposites by the electrospinning process. The prepared nanoparticles and nanofibers were characterized using the Scanning Electron Microscopy (SEM) and X-ray diffraction methods. The results manifested that nanofibers of PAN and CoFe2O4 /PAN were successfully prepared with electrospinning method. Grayscale SEM images of nanofibers were analyzed by a new image analysis procedure for determination of fibers diameter, their diameter distribution and the compactness of electrospun nanofibers. It was found that the presence of CoFe2O4 nanoparticles in the PAN solution increases both of the compactness of electrospun nanofibers and their diameter. The prepared CoFe2O4/Polyacrylonitrile fiber nanocomposites have possible applications in fabrication of sensor and magnetic recording media.

In comparison to the previous researches, ZrO2 nanoparticles with higher surface area (85 m2/g) have been synthesized in this research. The as-prepared ZrO2 nanoparticles by co-precipitation method were characterized with X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The surface area of the sample was characterized by BET method. The effect of the growth parameters such as temperature, pH, Zr4+/template ratio and kind of template on the growth and morphology of ZrO2 nanoparticles have been investigated in detail. The results revealed that pH, temperature, Zr4+/template and kind of template have an important effect on the morphology and size of the ZrO2 nanoparticles. X Ray Diffraction (XRD) analysis of the superior nanoparticles that was prepared at pH=4, Temperature=70oC, Zr4+/template ratio=2 and by sorbitol as template indicates the formation of nanocrystalline ZrO2 tetragonal phase structure. The average particle size of the product is about 4.45 nm that was calculated from XRD pattern by the Debye-Scherrer formula.

ZnO and TiO2 nanoparticles were impregnated with merbromin dye and used as modified photocatalysts for degradation of phenol. Dye-modified ZnO and TiO2 showed significantly higher photocatalytic activity than neat ZnO and TiO2 under visible light illumination. Moreover, the prepared dye-modified ZnO showed superior photocatalytic efficiency in degradation of phenol compared to the dye-modified TiO2. In a period of 4 hours, dye-modified ZnO removed phenol almost completely while dye-modified TiO2 degraded it only to 47%. A cooperative working mechanism involving the possible photoactivation of both surface bound dye and semiconductor is proposed for the dye-modified systems. The suggested pathway is based on charge-transfer formalism. Furthermore, the study proposes some reasons for difference in reactivity of the dye-modified ZnO and TiO2 catalysts. Less aggregation of dye molecules on the surface of ZnO compared to TiO2 causes more prolonged lifetime of excited state of the dye on the surface of ZnO. Also, energy gap between the conduction band of semiconductor and LUMO level of merbromin in dye-modified ZnO is larger than dye-modified TiO2. Both above lead to more effective electron injection from the dye to ZnO which is hypothesized to be mainly responsible for the enhancement of the reaction rate of phenol degradation.

Nickel (II) complex of [NiL2] (ClO4)2, where L is an unsymmetrical tridentate ligand of 2-(2-aminoethyl) imino-3-butanone oximehas been synthesized by a template condensation reaction. The complex was characterized on the basis of microanalytical, spectroscopic, and other physicochemical properties. X-ray diffraction study of the complex reveals nickel (II) centerin a distorted octahedral environment through two amine nitrogen donors, two imine donors, and two nitrogen atoms of the oxime moieties of the ligand. The antibacterial activity of the complex has been tested against Gram (+) and Gram (-) bacteria. The results of the antibacterial screening indicated that the complex is effective against bacterial growth retardation activity to some extent and its effectiveness is higher forGram (+) bacteria.

Leaching of molybdenite concentrate with hydrogen peroxide in sulfuric acid solution was investigated to determine the effects of reaction time, reaction temperature, H2O2 concentration, H2SO4 concentration, pulp density and rotation speed on molybdenum extraction and molybdenite dissolution kinetics, using the Taguchi method. From analysis of variance (ANOVA) for molybdenum extraction, the most significant factors were H2O2 concentration, pulp density and reaction temperature. The optimal factor levels to maximize extraction were determined. As the leaching process does not result in an ash layer, only chemically controlled kinetic model was applied. ANOVA for the reaction rate constant showed that H2O2 concentration made the greatest contribution to the model, and reaction time and temperature were also statistically significant factors. The reaction rate constant increased with increasing temperature and H2O2 concentration. The order of reaction with respect to H2O2 and activation energy for the dissolution were determined to be 1.21 and 46.5 kJ/mol, respectively, and a semi-empirical rate equation was derived.

Samples of the waste rock obtained from Marofengin South Africa ground 60, 70 and 80% passing 75µm were leached with cyanide in bottle roll tests. The results obtained showed that the percentage gold dissolution depends more on the ore size consists than on the cyanide concentration with the highest average dissolution rates of 88.75, 94.34 and 95.90% found at 600, 500 and 500 ppm, for 60, 70 and 80% passing sizes, respectively. It was also noted that the lowest average percents cyanide consumption of 62.91, 61.73 and 58.56 at 60, 70 and 80% passing 75 µm were obtained at the 500 ppm cyanide concentrations. It was further observed that a clear pattern of increasing residual lime content was only observed at the 70% grind size, with the least lime content of 150.37 ppm at 500 ppm cyanide concentration being higher than the least lime contents for the 60 and 80% grind sizes. The results obtained thus suggest the 70% grind passing 75mmore with the gold dissolution percentage very close to the conventional 80% passing size at the lowest cyanide consumption of 500 ppm, much lower daily power consumption of about 925 kWh and high residual lime content that indicated the minimization of cyanide loss as hydrogen cyanide, a good choice for the leaching of the waste rock.

The present work examines leaching of lipoxygenase-1 from soybean flour employing stirred tank vessel. The effect of operating parameters, impellers speed, operational period, temperature, pH and scale-up were considered. The acetic acid pH: 5.2 increased the leaching of lipoxygenase- 1. The sensitivity of agitator speed and geometrical-scale-up on the enzyme leaching has been conducted. The effect of agitator speed on the geometrically-scaled- up reactor has shown that similar amount of enzyme is leached at lower speed. The result is in para with the conventional system. The importance of operational period from 5 to 50 min on the enzyme leaching was evaluated and higher enzyme leaching obtained within 10 min. of operation. The Sigmaplot-6 for statistical verification and developing a correlation for the enzyme leaching was used.

Heat transfer phenomena in batch fluidized bed dryer have been studied and analyzed using three phase model including solid phase, interstitial gas phase and bubble phase based on Rizzi model. New correlations of heat transfer coefficient to surrounding and convection heat transfer coefficient between solid and interstitial gas are being proposed. In addition, some modifications have been done according to the state of flow and particle properties.The model was used to study the effects of particle diameter, particle density and input gas temperature on Geldart group D particles. The numerical results of heat transfer such as solid and gas temperature distributions have been compared with the available experimental data and good agreement between them is observed.

Wastewater from molasses processing contains a large amount of coloured substances that give a recalcitrant dark brown colour and high organic load to the effluent. Photocatalytic decolourization of molasses wastewater was performed using titanium dioxide catalyst coated on the surface of South African natural zeolite using the solid-solid dispersion method. Addition of hydrogen peroxide as an oxidant was investigated and 30W UV-Clamp was used as source of irradiation. The Chemical Oxygen Demand (COD) of the wastewater treated was varied from 20 g/L to 1 g/L. Batch experiments were conducted in a thermostatic shaker fitted with the UV lamp. The effects of pH, catalyst loading, oxidant dosage and irradiation time on the COD reduction and decolourization of the Molasses Waste Water (MWW) were investigated in this study. The highest colour removal of more than 90% was achieved at pH=4 and oxidant dosage of 1.47 mM, while low COD removal (<20%) was observed during photodegradation. A H2O2/UV/TiO2 system achieved higher colour removal of 97% compared to a UV/TiO2 system which achieved 44% while H2O2/UV system achieved 34% colour removal. The rate of decolourization was found to fitpseudo - first order reaction kinetics with the highest rate constant value of 1.36 x 10-2 min-1.