Search for: ph-effects
0.007 seconds

    Partitioning of l-lysine monohydrochloride in aqueous two-phase systems of poly(ethylene glycol) and dipotassium hydrogen phosphate or trisodium citrate 5-hydrate

    , Article Journal of Chemical and Engineering Data ; Volume 55, Issue 9 , 2010 , Pages 3005-3009 ; 00219568 (ISSN) Mirsiaghi, M ; Pazuki, G ; Vossoughi, M ; Alemzadeh, I ; Sharif University of Technology
    The partition constants of l-lysine HCl were measured in polymer-salt aqueous two-phase systems. These systems contain poly(ethylene glycol) with a nominal molecular weight of 4000 or 10000 and two different salts (dipotassium hydrogen phosphate or trisodium citrate 5-hydrate). The experimental data were obtained at temperatures of (293.15, 298.15, and 303.15) K. The effects of temperature, pH, polymer and salt concentrations, polymer molecular weight, and salt type on the partitioning of l-lysine HCl were also studied. The results showed that salt concentration has a significant effect on the partition constant while temperature has less effect. The Diamond and Hsu model was used to... 

    Investigation and optimization of SDS and key parameters effect on the nickel electroless coatings properties by Taguchi method

    , Article Journal of Coatings Technology Research ; Volume 7, Issue 5 , 2010 , Pages 547-555 ; 15470091 (ISSN) Farzaneh, A ; Ehteshamzadeh, M ; Ghorbani, M ; Vazifeh Mehrabani, J ; Sharif University of Technology
    In this research, the influence of anionic surfactant sodium dodecyl sulfate (SDS), pH, substrate finishing, and annealing temperature on the surface morphology and hardness of the electroless nickel phosphorus (ENi-P) coatings were studied. Taguchi's experimental design method was used. Parameters selected in three levels and L9 from orthogonal robust array design were employed. Surface roughnesses of the deposits were measured using a stylus instrument. Scanning electron microscope and x-ray diffraction analysis were implemented to study surface morphologies and phase composition, respectively. Microhardness of the ENi-P deposits was measured using a microhardness tester at three trials... 

    Enzymatic synthesis of amoxicillin with immobilized penicillin G acylase

    , Article Scientia Iranica ; Volume 17, Issue 1 C , 2010 , Pages 106-113 ; 10263098 (ISSN) Alemzadeh, I ; Borghei, G ; Vafi, L ; Roostaazad, R ; Sharif University of Technology
    The synthesis of amoxicillin with immobilized penicillin G acylase (PGA) in aqueous medium was investigated. The parameters studied were: time course of amoxicillin production, concentration of substrates: hydroxyphenylglycine methyl ester (HPGM) and 6-aminopeicillanic acid (6-APA) and the. effect of enzyme (PGA) content and pH, under variable and constant conditions and temperature variations. In the study of two substrate concentration on amoxicillin production, impressive results were obtained for a 1/3 ratio of 6-amino penicillanic acid (6-APA) and hydroxyl-phenylglycine methyl ester (HPGM). The. synthesis of amoxicillin was preferable at constant pH rather than a variable one. Other... 

    Glassy carbon electrodes modified with a film of nanodiamond-graphite/chitosan: Application to the highly sensitive electrochemical determination of Azathioprine

    , Article Electrochimica Acta ; Volume 55, Issue 11 , 2010 , Pages 3621-3627 ; 00134686 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Sharif University of Technology
    A novel modified glassy carbon electrode with a film of nanodiamond-graphite/chitosan is constructed and used for the sensitive voltammetric determination of azathioprine (Aza). The surface morphology and thickness of the film modifier are characterized using atomic force microscopy. The electrochemical response characteristics of the electrode toward Aza are investigated by means of cyclic voltammetry. The modified electrode showed an efficient catalytic role for the electrochemical reduction of Aza, leading to a remarkable decrease in reduction overpotential and enhancement of the kinetics of the electrode reaction with a significant increase of peak current. The effects of experimental... 

    Relative and interactive effects of fluid's physicochemical characteristics on the incipient motion of a granular particle under laminar flow condition

    , Article Journal of Hydraulic Engineering ; Volume 144, Issue 5 , 2018 ; 07339429 (ISSN) Xiao, M ; Gholizadeh Vayghan, A ; Adams, B. T ; Rajabipour, F ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2018
    This paper presents an experimental research for studying the relative and interactive effects of three physicochemical fluid characteristics (viscosity, pH, and ionic strength) on the incipient motion of a granular particle under laminar flow condition. Critical flow velocity for particle's incipient motion, an important factor for evaluating flow-induced soil erosion, was used to quantify the relative erosive capacity of the test fluids. Response surface methodology (RSM), a statistical design of experiments, was used to design and implement 20 test fluids with various levels of the three fluid characteristics. Incipient motion of a highly spherical glass bead positioned atop a specially... 

    Microbial leaching of a low-grade sphalerite ore using a draft tube fluidized bed bioreactor

    , Article Hydrometallurgy ; Volume 99, Issue 3-4 , 2009 , Pages 131-136 ; 0304386X (ISSN) Soleimani, M ; Hosseini, S ; Roostaazad, R ; Petersen, J ; Mousavi, M ; Kazemi Vasiri, A ; Sharif University of Technology
    The use of a draft tube fluidized bed bioreactor (DTFBB) has been successfully demonstrated for the bioleaching of a chalcopyrite concentrate (Mousavi, et. al., 2005). In the present paper this technique was used for the bioleaching of zinc from a sphalerite bearing low-grade ore. A strain of the thermophilic bacterium, Sulfobacillus, has been isolated from the Kooshk lead and zinc mine near the city of Yazd (Iran) and is tested at temperatures 47 °C-72 °C. This is compared to leaching with a strain of the mesophile Acidithiobacillus ferrooxidans, which has been adapted to the high levels of zinc and the presence of the low-grade ore, and which was tested at temperatures 18 °C-42 °C. The... 

    Properties of alumina nanoparticle-filled nitrile-butadiene-rubber/ phenolic-resin blend prepared by melt mixing

    , Article Polymer Composites ; Volume 30, Issue 9 , 2009 , Pages 1290-1298 ; 02728397 (ISSN) Faghihi, M ; Shojaei, A ; Sharif University of Technology
    Effect of alumina nanoparticle (ANP) on the properties of rubber compounds based on nitrile-butadiene-rub- ber (NBR) and NBR/phenolic-resin (PH) blend is examined. To investigate the surface characteristics of the nanoparticles on the performance of nanoalumina- filled compounds, trimethoxyvinylsilane (MVS) is attached chemically on the surface of ANP through an appropriate functionalization process. Various NBR and NBR/Ph compounds filled with ANP and functionalized ANP (f-ANP) are prepared via melt mixing using traditional open two-roll mill. Microscopic analysis carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveals good dispersion of... 

    Corrosion protection of aluminum by smart coatings containing layered double hydroxide (LDH) nanocontainers

    , Article Journal of Materials Research and Technology ; Volume 8, Issue 3 , 2019 , Pages 3004-3023 ; 22387854 (ISSN) Imanieh, I ; Afshar, A ; Sharif University of Technology
    Elsevier Editora Ltda  2019
    In this study, the LDH containing a kind of green inhibitor (sodium molybdate) was synthesized and utilized in a poly-vinyl alcohol (PVA) base coating applied on the aluminum (5054 series) surface. After evaluating the LDH performance, the inhibitor release from the LDH crystals was examined by changing significant parameters like MII/MIII (the molar ratio of divalent ions into trivalent ions), pH, aging time and temperature. In order to find the kinetic release of intercalated inhibitor a prediction model was introduced in 3.5% NaCl solution. The model expressed that the pH as the processing parameter has special effect on the kinetic releasing of the inhibitor. It can enhance the amount of... 

    Effect of collision on self-assembly of nanoparticles in zirconia microparticle suspension

    , Article Journal of Dispersion Science and Technology ; 2020 Jiryaei, Z ; Saidi, M. H ; Sharif University of Technology
    Bellwether Publishing, Ltd  2020
    Nanoparticle halo mechanism is a stabilization method for microparticle suspensions. This study investigates suspension pH and nanoparticles–microparticles collision effects on the stabilization of an aqueous binary suspension. The long-term turbidity measurements show that for the nanosilica suspension stability is directly correlated with pH values; however, in the cases of zirconia and binary suspensions, it is not a monotonic function of pH. It is shown that for binary suspension, the halo mechanism is the primary method affecting the stability of the suspension. The suspension is best-stabilized at pH = 5 that is associated with high halo mechanism efficiency, while increased repulsive... 

    Influence of phosphate anions on the stability of immobilized enzymes. Effect of enzyme nature, immobilization protocol and inactivation conditions

    , Article Process Biochemistry ; Volume 95 , August , 2020 , Pages 288-296 Kornecki, J. F ; Carballares, D ; Morellon Sterling, R ; Siar, E. H ; Kashefi, S ; Chafiaa, M ; Arana Peña, S ; Rios, N. S ; Gonçalves, L. R. B ; Fernandez Lafuente, R ; Sharif University of Technology
    Elsevier Ltd  2020
    A destabilizing effect at pH 7 of sodium phosphate on several lipases immobilized via interfacial activation is shown in this work. This paper investigates if this destabilizing effect is extended to other inactivation conditions, immobilization protocols or even other immobilized enzymes (ficin, trypsin, β-galactosidase, β-glucosidase, laccase, glucose oxidase and catalase). As lipases, those from Candida antarctica (A and B), Candida rugosa and Rhizomucor miehei have been used. Results confirm the very negative effect of 100 mM sodium phosphate at pH 7.0 for the stability of all studied lipases immobilized on octyl agarose, while using glutaraldehyde-support the effect is smaller (still... 

    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) Mousavi, S. M ; Yaghmaei, S ; Vossoughi, M ; Roostaazad, R ; Jafari, A ; Ebrahimi, M ; Chabok, O. H ; Turunen, I ; Sharif University of Technology
    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... 

    Optimization of peroxidase-catalyzed oxidative coupling process for phenol removal from wastewater using response surface methodology

    , Article Environmental Science and Technology ; Volume 41, Issue 20 , 2007 , Pages 7073-7079 ; 0013936X (ISSN) Ghasempur, S ; Torabi, S. F ; Ranaei Siadat, S. O ; Jalali Heravi, M ; Ghaemi, N ; Khajeh, K ; Sharif University of Technology
    Hydroxylated aromatic compounds (HACs) are considered to be primary pollutants in a wide variety of industrial wastewaters. Horseradish peroxidase (HRP) is suitable for the removal of these toxic substances. However, development of a mathematical model and optimization of the HRP-based treatment considering the economical issues by novel methods is a necessity. In the present study, optimization of phenol removal from wastewater by horseradish peroxidase (HRP) was carried out using response surface methodology (RSM) and central composite design (CCD). As the initial experimental design, 2 4-1 half-fraction factorial design (H-FFD) is accomplished in triplicate at two levels to select the... 

    Experimental investigation on synergic effect of salinity and pH during low salinity water injection into carbonate oil reservoirs

    , Article Journal of Petroleum Science and Engineering ; Volume 202 , 2021 ; 09204105 (ISSN) Mehraban, M. F ; Ayatollahi, S ; Sharifi, M ; Sharif University of Technology
    Elsevier B.V  2021
    Interaction between rock-fluid and fluid-fluid can have a significant effect on oil recovery. Changing the wettability of reservoir rock toward more water-wet or less oil-wet state is one of the expected mechanisms during low salinity water injection (LSWI). pH and salinity are of the most eminent factors of injection water controlling the wettability state of a crude oil/brine/rock system during any waterflooding operation. A small change in pH can affect the surface charges at the rock/water and oil/water interfaces leading to wettability alteration in a porous medium. In this study, the synergic effect of salinity and pH on the wettability state of carbonate rocks is evaluated through... 

    Electrochemical deposition of gold nanoparticles on carbon nanotube coated glassy carbon electrode for the improved sensing of tinidazole

    , Article Electrochimica Acta ; Volume 78 , September , 2012 , Pages 422-429 ; 00134686 (ISSN) Shahrokhian, S ; Rastgar, S ; Sharif University of Technology
    The electrochemical reduction of tinidazole (TNZ) is studied on gold-nanoparticle/carbon-nanotubes (AuNP/CNT) modified glassy carbon electrodes using the linear sweep voltammetry. An electrochemical procedure was used for the deposition of gold nanoparticles onto the carbon nanotube film pre-cast on a glassy carbon electrode surface. The resulting nanoparticles were characterized by scanning electron microscopy and cyclic voltammetry. The effect of the electrodeposition conditions, e.g., salt concentration and deposition time on the response of the electrode was studied. Also, the effect of experimental parameters, e.g., potential and time of accumulation, pH of the buffered solutions and... 

    Effect of pH, citrate treatment and silane-coupling agent concentration on the magnetic, structural and surface properties of functionalized silica-coated iron oxide nanocomposite particles

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 44, Issue 3 , December , 2011 , Pages 618-627 ; 13869477 (ISSN) Mohammad Beigi, H ; Yaghmaei, S ; Roostaazad, R ; Bardania, H ; Arpanaei, A ; Sharif University of Technology
    Superparamagnetic iron oxide nanoparticles were synthesized by coprecipitation of iron chloride salts at various pH values (9, 10, 11 and12) that were adjusted using an ammonia solution. Increasing the pH from 9 to 12 led to decreases in the size of iron oxide nanoparticles from 7.9±1.4 to 5±0.6 nm and the saturation magnetization (M s) from 82.73 to 67.14 emu/g, respectively, when analyzed with transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). X-ray diffraction patterns as well as M s values showed that magnetite is the dominantly synthesized phase in the examined pH values. Unmodified iron oxide nanoparticles were coated with silica via the hydrolysis and... 

    Glassy carbon electrode modified with a bilayer of multi-walled carbon nanotube and polypyrrole doped with new coccine: Application to the sensitive electrochemical determination of Sumatriptan

    , Article Electrochimica Acta ; Volume 56, Issue 27 , November , 2011 , Pages 10032-10038 ; 00134686 (ISSN) Shahrokhian, S ; Kamalzadeh, Z ; Saberi, R. S ; Sharif University of Technology
    A promising electrochemical sensor was developed based on a layer by layer process by electro-polymerization of pyrrole in the presence of new coccine (NC) as dopant anion on the surface of the multi-walled carbon nanotubes (MWCNTs) pre-coated glassy carbon electrode (GCE). The modified electrode was used as a new and sensitive electrochemical sensor for voltammetric determination of sumatriptan (SUM). The electrochemical behavior of SUM was investigated on the surface of the modified electrode using linear sweep voltammetry (LSV). The results showed a remarkable increase (∼12 times) in the anodic peak current of SUM in comparison to the bare GCE. The effect of experimental variables such... 

    Enhancing biosurfactant production from an indigenous strain of Bacillus mycoides by optimizing the growth conditions using a response surface methodology

    , Article Chemical Engineering Journal ; Volume 163, Issue 3 , October , 2010 , Pages 188-194 ; 13858947 (ISSN) Najafi, A. R ; Rahimpour, M. R ; Jahanmiri, A. H ; Roostaazad, R ; Arabian, D ; Ghobadi, Z ; Sharif University of Technology
    In this study, we have investigated the potential of a native bacterial strain isolated from an Iranian oil field for the production of biosurfactant. The bacterium was identified to be Bacillus mycoides by biochemical tests and 16S ribotyping. The biosurfactant, which was produced by this bacterium, was able to reduce the surface tension of media to 34. mN/m. Compositional analysis of the produced biosurfactant has been carried out by thin layer chromatography (TLC) and FT-IR. The biosurfactant produced by the isolate was characterized as lipopeptide derivative. Biosurfactant production was optimized by the combination of central composite design (CCD) and response surface methodology... 

    Degradation of humic acids through heterogeneous catalytic ozonation with bone charcoal

    , Article Reaction Kinetics, Mechanisms and Catalysis ; Volume 100, Issue 2 , 2010 , Pages 471-485 ; 18785190 (ISSN) Mortazavi, S. B ; Asgari, Gh ; Hashemian, S. J ; Moussavi, G ; Sharif University of Technology
    Catalytic ozonation has recently been used as a new means of contaminant removal from water and wastewater. In this study, bone charcoal (BC), a new catalyst prepared under laboratory conditions, was used to catalyze the ozonation of humic substances (HS) in aqueous solutions. The catalytic effect of bone charcoal and the relevant parameters of this ozonation process (solution pH, temperature, scavenger effect, humic acids concentration and BC dosage) were investigated. In the catalytic ozonation experiments, the degradation kinetics was investigated. The reaction rate and the rate constant were determined. The results showed that using a BC catalyst in the ozonation of HS produced a 1.43-... 

    Fractional factorial design for the optimization of hydrothermal synthesis of lanthanum oxide nanoparticles under supercritical water condition

    , Article Journal of Supercritical Fluids ; Volume 52, Issue 3 , 2010 , Pages 292-297 ; 08968446 (ISSN) Jafari Nejad, Sh ; Abolghasemi, H ; Moosavian, M. A ; Golzary, A ; Ghannadi Maragheh, M ; Sharif University of Technology
    In this research, synthesis of lanthanum oxide nanoparticles using supercritical water as a reaction medium in batch type reactor was studied. The crystallographic identity and morphology of the synthesized nanoparticles were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate that the well-crystallized lanthanum oxide nanocrystals can be easily obtained under the current synthetic conditions. The effect of four parameters includes temperature, reaction time; primary concentration of aqueous solution of lanthanum (III) nitrate and pH of starting solution on reaction efficiency, particle size and the BET surface area were investigated... 

    Simultaneous determination of epinephrine and acetaminophen concentrations using a novel carbon paste electrode prepared with 2,2′-[1,2 butanediylbis(nitriloethylidyne)]-bis-hydroquinone and TiO2 nanoparticles

    , Article Colloids and Surfaces B: Biointerfaces ; Volume 76, Issue 1 , 2010 , Pages 82-87 ; 09277765 (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Sheikh Mohseni, M. A ; Benvidi, A ; Naeimi, H ; Nejati Barzoki, M ; Taghavinia, N ; Sharif University of Technology
    A carbon paste electrode (CPE) modified with 2,2′-[1,2 butanediylbis(nitriloethylidyne)]-bis-hydroquinone (BBNBH) and TiO2 nanoparticles was used for the sensitive voltammetric determination of epinephrine (EP). The electrochemical response characteristics of the modified electrode toward EP and acetaminophen (AC) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic activity of the electrode for the electrooxidation of EP, which leads to a reduction in its overpotential by more than 270 mV. The effects of pH and potential sweep rate on the mechanism of the electrode process were investigated. The modified electrode exhibits an...