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concentration--process
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Zinc extraction from Iranian low-grade complex zinc-lead ore by two native microorganisms: Acidithiobacillus ferrooxidans and Sulfobacillus
, Article International Journal of Mineral Processing ; Volume 80, Issue 2-4 , 2006 , Pages 238-243 ; 03017516 (ISSN) ; Yaghmaei, S ; Vossoughi, M ; Jafari, A ; Roostaazad, R ; Sharif University of Technology
2006
Abstract
A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (33 °C) from a typical, chalcopyrite concentrate of the Sarcheshmeh copper mine in the region of Kerman located in the south of Iran. In addition, a thermophilic iron oxidizing bacterium, Sulfobacillus, has been isolated (60 °C) from the sphalerite concentrate of Kooshk lead and zinc mine near the city of Yazd in the center point of Iran. Variation of pH, ferrous and ferric concentration on time and effects of some factors such as temperature, cell growth, initial ferrous concentration and pH on bioleaching of low-grade complex zinc-lead ore were investigated. The results obtained from bioleaching...
Three-dimensional structures in experimental density currents
, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 1 SYMPOSIA, Issue PART A , March , 2007 , Pages 781-787 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Afshin, H ; Safaaee, E ; Sharif University of Technology
2007
Abstract
Density currents are continuous currents which move down-slope due to the fact that their density is greater than that of ambient water. The density difference is caused by temperature differences, chemical elements, dissolved materials, or suspended sediment. Many researchers have studied the density current structures, their complexities and uncertainties. However, there is not a detailed 3-D turbulent density current data set perfectly. In this work, the structure of 3-dimensional salt solution density currents is investigated. A laboratory channel was used to study the flow resulting from the release of salt solution into freshwater over an inclined bed. The experiments were conducted...
The Pr and oxygen correlation in the GdPr123 system
, Article Modern Physics Letters B ; Volume 16, Issue 25 , 2002 , Pages 943-953 ; 02179849 (ISSN) ; Daadmehr, V ; Akhavan, M ; Sharif University of Technology
2002
Abstract
We prepared single-phase polycrystalline Gd1-xPrx Ba2Cu3O7-δ samples with x = 0, 0.10, 0.15, and 0.20. The deoxygenation process of these samples was performed by an annealing method. Electrical resistivity measurements revealed depression of the transition temperature with the increase of x and δ. We calculated the hole concentration in the CuO2 plane for different values of x and δ. A linear dependence of transition temperature and hole concentration in the CuO2 plane was found as a function of 2δ + x. It is proposed that a combination of the localization and filling of holes should be considered as the effective mechanisms for the appearance of the Pr anomaly in HTSCs
The effects of Fe(II) and Fe(III) concentration and initial pH on microbial leaching of low-grade sphalerite ore in a column reactor
, Article Bioresource Technology ; Volume 99, Issue 8 , 2008 , Pages 2840-2845 ; 09608524 (ISSN) ; Yaghmaei, S ; Vossoughi, M ; Roostaazad, R ; Jafari, A ; Ebrahimi, M ; Chabok, O. H ; Turunen, I ; Sharif University of Technology
2008
Abstract
In this study the effects of initial concentration of Fe(II) and Fe(III) ions as well as initial pH on the bioleaching of a low-grade sphalerite ore in a leaching column over a period of 120 days with and without bacteria were investigated. Four different modifications of medium were used as column feed solutions to investigate the effects of initial concentration of Fe(II) and Fe(III) ions on zinc extraction. The experiments were carried out using a bench-scale, column leaching reactor, which was inoculated with mesophilic iron oxidizing bacteria, Acidithiobacillus ferrooxidans, initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran). The effluent solutions were...
The effect of variable catalyst loading in electrodes on PEM fuel cell performance
, Article 3rd International Conference on Fuel Cell Science, Engineering, and Technology, 2005, Ypsilanti, MI, 23 May 2005 through 25 May 2005 ; 2005 , Pages 145-152 ; 0791837645 (ISBN); 9780791837641 (ISBN) ; Farhanieh, B ; Sharif University of Technology
American Society of Mechanical Engineers
2005
Abstract
Catalyst layers are one the important parts of the PEM fuel cells as they are the main place for electrochemical reaction taking place in anode and cathode of the cells. The amount of catalyst loading of this layer has a large effect on PEM fuel cell performance. Non-uniformity of reactant concentration could lead to a variation of current density in anode and cathode catalyst layer. The main reason for this phenomenon is porosity variation due to two effects: 1. compression of electrode on the solid landing area and 2. Water produced at the cathode side of diffusion layer. In this study the effect of variable current density in anode and cathode electrode on cell performance is...
The effect of growth parameters on photo-catalytic performance of the MAO-synthesized TiO2 nano-porous layers
, Article Materials Chemistry and Physics ; Volume 120, Issue 2-3 , 2010 , Pages 582-589 ; 02540584 (ISSN) ; Golestani Fard, F ; Moshfegh, A. Z ; Sharif University of Technology
2010
Abstract
In this research, the effect of applied voltage and electrolyte concentration on structure, chemical composition, optical properties, and especially photo-catalytic activity of the TiO2 layers containing micro/nano-sized pores are discussed. TiO2 layers were synthesized by micro arc oxidation (MAO) process using different electrolyte concentrations and applied voltages. Surface structure of the layers was studied by scanning electron microscope (SEM); furthermore, energy dispersive spectrophotometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were employed to determine phase structure and chemical composition of the layers. Photo-activity of the...
The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au-Ag:SiO2 thin films
, Article Journal of Alloys and Compounds ; Volume 486, Issue 1-2 , 2009 , Pages 22-28 ; 09258388 (ISSN) ; Akhavan, O ; Zaker Moshfegh, A. R ; Sharif University of Technology
2009
Abstract
Gold-silver alloy nanoparticles with various Au concentrations in sputtered SiO2 thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H2 atmosphere at different temperatures. The UV-visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au-Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing...
The effect of additives on anode passivation in electrorefining of copper
, Article Chemical Engineering and Processing: Process Intensification ; Volume 46, Issue 8 , 2007 , Pages 757-763 ; 02552701 (ISSN) ; Yoozbashizadeh, H ; Sadegh Safarzadeh, M ; Sharif University of Technology
2007
Abstract
In copper electrorefining process, some additives are added to the electrolyte to improve the morphology of cathode deposits as well as the quality of products. In the present investigation, the effects of thiourea, glue and chloride ions (as additives) on the passivation of industrial copper anodes under high current densities have been reported. Experiments were conducted at 65 °C; using a synthetic electrolyte containing 40 g/l Cu2+ and 160 g/l H2SO4. Results obtained from chronopotentiometry experiments showed that increasing the concentration of chloride ion leads to increase in passivation time. The results also indicated that from a certain level on, namely 2 ppm, the increase in...
Synthesis of high surface area nanocrystalline anatase-TiO2 powders derived from particulate sol-gel route by tailoring processing parameters
, Article Journal of Sol-Gel Science and Technology ; Volume 40, Issue 1 , 2006 , Pages 15-23 ; 09280707 (ISSN) ; Cordero Cabrera, M. C ; Ghorbani, M ; Fray, D.J ; Sharif University of Technology
2006
Abstract
Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism, with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO2 concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO 2 concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher...
Synthesis, characterization and swelling behavior of chitosan-sucrose as a novel full-polysaccharide superabsorbent hydrogel
, Article Journal of Applied Polymer Science ; Volume 109, Issue 4 , 15 August , 2008 , Pages 2648-2655 ; 00218995 (ISSN) ; Aghajani, V ; Ghasemzadeh, H ; Sharif University of Technology
2008
Abstract
A novel full-polysaccharide hydrogel was prepared by crosslinking of chitosan with periodate-oxidized sucrose. A tetraaldehyde molecule is synthesized via periodate oxidation of sucrose and then applied as a crosslinking agent to form a new hydrogel network. A mechanism for the superabsorbent hydrogel formation via reductive N-alkylation was also suggested. The structure of the hydrogel was confirmed by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). It is shown that crosslinking of chitosan can improve its thermal stability. The effects of crosslinker concentration, pH, and inorganic salt on the swelling behavior of the hydrogel were studied. The...
Sulphate reduction in a three-stage packed-bed anaerobic bioreactor
, Article World Environmental and Water Resources Congress 2008: Ahupua'a, Honolulu, HI, 12 May 2008 through 16 May 2008 ; Volume 316 , 2008 ; 9780784409763 (ISBN) ; Poorhashem, Q ; Environmental and Water Resources Institute of ASCE ; Sharif University of Technology
2008
Abstract
In this paper the effect of the sulphate concentration on the performance of a three-stage anaerobic baffled packed-bed reactor (ABPR) was investigated. Synthetic wastewater (3000 mg COD/l) was used as the sole organic substrate. The 30 liters fixed-bed bioreactor filled with plastic packing and divided in three equal sections was used as the mABPR reactor. The unit was run at a hydraulic retention time (HRT) of 1 day and at temperature of 25° C. The results of this study showed that when COD/SO42- ratios were changed from 30 to 3 with increasing sulphate concentration from 100 to 1000 mg/l, COD removal slightly was decreased. Maximum COD and sulphate removal were 91 and 96%, respectively,...
Study and optimization of amino acid extraction by emulsion liquid membrane
, Article Separation Science and Technology ; Volume 43, Issue 11-12 , 2008 , Pages 3075-3096 ; 01496395 (ISSN) ; Alemzadeh, I ; Vossoughi, M ; Sharif University of Technology
2008
Abstract
A batch extraction of an essential amino acid, phenylalanine, from an aqueous solution of different concentrations by an Emulsion Liquid Membrane (ELM) was developed using D2EHPA as a cationic carrier, Span 80 as the surfactant, paraffin, and kerosene as the diluents, and HCl as the internal electrolyte. All effective parameters such as the initial pH of the aqueous external phase, the electrolyte concentration in the aqueous internal phase, carrier, and surfactant concentration in the emulsion, the volume ratio of the organic to aqueous internal phase (Roi), the volume ratio of the W/O emulsion to the aqueous external phase (Rew) and time were examined and optimized using the Taguchi...
Studies of Iranian heavy oils pertinent to reservoir conditions for their auto-ignition to initiate fire flooding
, Article Chemical Engineering Communications ; Volume 196, Issue 5 , 2009 , Pages 643-657 ; 00986445 (ISSN) ; Razzaghi, S ; Kharrat, R ; Rashtchian, D ; Vossoughi, S ; Sharif University of Technology
2009
Abstract
In this work, the potential for the auto-ignition of Iranian heavy oil during in situ combustion (ISC) process conditions was studied. Kinetic studies were carried out using thermal analysis techniques. Effects of oxygen partial pressure, reservoir pressure, and clay on the auto-ignition condition were investigated. Based on the experimental results obtained, a kinetic equation was derived for each of the different oil samples in the presence of different sands. The effect of partial pressure of oxygen in the injected air showed that at atmospheric pressure, low temperature combustion (LTC) was initiated at 275°C. Also, enriching the injected air by oxygen lowers the initial LTC temperature...
Statistical analysis for enzymatic decolorization of acid orange 7 by Coprinus cinereus peroxidase
, Article International Biodeterioration and Biodegradation ; Volume 64, Issue 3 , 2010 , Pages 245-252 ; 09648305 (ISSN) ; Kariminia, H. R ; Sharif University of Technology
2010
Abstract
Enzymatic decolorization of the monoazo dye, acid orange 7 (AO7) by the fungal peroxidase from Coprinus cinereus NBRC 30628 is a complex system, which is greatly affected by temperature, pH, enzyme activity and the concentrations of H2O2 and dye concentration. The study of these factors and investigating the combined interactions between them by applying one-factor-at-a-time (OFAT) method and two other statistical methods including 2-factorial method and response surface methodology (RSM) were aimed in this work. Through OFAT analysis the optimized conditions were a temperature of 25 °C, pH 9.0 with H2O2 concentration of about 3.9 mM and AO7 concentration of 40 mg/l. A complete...
Stability, size and optical properties of colloidal silver nanoparticles prepared by electrical arc discharge in water
, Article EPJ Applied Physics ; Volume 48, Issue 1 , 2009 , Pages 10601p1-10601p7 ; 12860042 (ISSN) ; Iraji Zad, A ; Ahadian, M. M ; Hormozi Nezhad, M. R ; Sharif University of Technology
2009
Abstract
We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl...
Solvent extraction of rare earth elements from a nitric acid leach solution of apatite by mixtures of tributyl phosphate and di-(2-ethylhexyl) phosphoric acid
, Article Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science ; Volume 48, Issue 6 , 2017 , Pages 3380-3387 ; 10735615 (ISSN) ; Yoozbashizadeh, H ; Sharif University of Technology
Abstract
Solvent extraction of rare earths from nitrate leach liquor of apatite using mixtures of tributyl phosphate (TBP) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) was studied. The effects of nitrate and hydrogen ion concentration of the aqueous phase as well as the composition and concentration of extractants in the organic phase on the extraction behavior of lanthanum, cerium, neodymium, and yttrium were investigated. The distribution ratio of REEs increases by increasing the nitrate concentration in aqueous phase and concentration of extractants in organic phase, but the hydrogen ion concentration in aqueous phase has a decreasing effect. Yttrium as a heavy rare earth is more sensitive to...
Simulation and experimental evaluation of initiator and surfactant concentrations and temperature effects on styrene conversion and polymer particle size distribution in batch emulsion polymerization
, Article Iranian Polymer Journal (English Edition) ; Volume 19, Issue 8 , Aug , 2010 , Pages 599-614 ; 10261265 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
Abstract
Effects of initiator and surfactant concentrations and temperature on styrene conversion and polymer particle size distribution (PSD) in a batch emulsion polymerization are investigated through simulation and experimental studies. The detailed model based on population balance (zero-one model), accounting for nucleation, growth and coagulation phenomena has been used for prediction of particle size distribution. In checking the effect of initiator concentration on final PSD, it was noticed that when critical micelle concentration (CMC) is kept constant, the model cannot predict PSD very well. Thus, a correlation for calculating critical micelle concentration has been proposed and...
Silver nano-islands on glass fibers using heat segregation method
, Article Materials Chemistry and Physics ; Volume 113, Issue 1 , 2009 , Pages 63-66 ; 02540584 (ISSN) ; Taghavinia, N ; Sharif University of Technology
2009
Abstract
A new method for fabrication of silver nano-islands on glass fibers using a top-down process is introduced. A thin layer of silver chemically coated on the surface of the glass fibers evolves into silver islands by heat treatment. The effect of the concentration of the initial solution and the temperature were investigated. Segregation was more clearly observed for lower solution concentrations and higher temperatures. The temperature of 500 °C was found optimum where separated islands form. At higher temperatures, the coagulation and burial of silver islands occur. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and diffused reflectance spectroscopy (DRS) were...
Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol
, Article Powder Technology ; Volume 197, Issue 1-2 , 2010 , Pages 49-53 ; 00325910 (ISSN) ; Guenther, B. H ; Sharif University of Technology
Abstract
Rheological behavior of agglomerated silver nanoparticles (~ 40 nm) suspended in diethylene glycol over a wide range of volumetric solids concentrations (φ{symbol} = 0.11-4.38%) was studied. The nanoparticle suspensions generally exhibited a yield pseudoplastic behavior. Bingham plastic, Herschel-Bulkley and Casson models were used to evaluate the shear stress-shear rate dependency. Analyzing the effect of silver concentrations on the yield stress and viscosity of the suspensions followed an exponential form, revealing an increase in the degree of interparticle interactions with increasing solid concentrations. Fractal dimension (Df) was estimated from the suspension yield stress and...
Protein folding rates correlate with heterogeneity of folding mechanism
, Article Physical Review Letters ; Volume 93, Issue 20 , 2004 , Pages 208105-1-208105-4 ; 00319007 (ISSN) ; Ejtehadi, M. R ; Plotkin, S. S ; Sharif University of Technology
American Physical Society
2004
Abstract
The folding rates of protein were shown to correlate with the degree of heterogeneity in the formation of native contacts. It was shown that both experimental rates and simulated free energy barriers for 2-state proteins depend on the degree of heterogeneity present in the folding process. Heterogeneity due to variance in the distribution of native loop lengths, and variance in the distribution of φ values, were observed to increase folding rates and reduce folding barriers. The observed effect due to φ variance was found to be the most statistically significant, because φ variance captures both heterogeneity arising from native topology and that arising from energetics