Search for: ph-effects
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    Effect of pH on aerobic granulation and treatment performance in sequencing batch reactors

    , Article Chemical Engineering and Technology ; Volume 38, Issue 5 , 2015 , Pages 851-858 ; 09307516 (ISSN) Rezasoltani, S ; Shayegan, J ; Jalali, S ; Sharif University of Technology
    Wiley-VCH Verlag  2015
    Two sequencing batch reactors were operated to investigate the effect of influent alkalinity and reactor pH on aerobic granulation. In the first reactor R1 with high influent alkalinity the pH was adjusted in the neutral range, and in the second reactor R2 with low alkalinity the pH was held within the acidic range. The R1-dominating species were bacteria and the appearance time of granules was three weeks after reactor start-up. On the other hand, the acidic environment of R2 provided favorable conditions for fungal growth, and rapid granule formation occurred within the first week of operation. The varying microbial structure of granules resulted in different reactor performance in terms... 

    Studies on the recovery of uranium from nuclear industrial effluent using nanoporous silica adsorbent

    , Article International Journal of Environmental Science and Technology ; Volume 9, Issue 4 , October , 2012 , Pages 629-636 ; 17351472 (ISSN) Sepehrian, H ; Samadfam, M ; Asadi, Z ; Sharif University of Technology
    Springer  2012
    In this paper, the sorption of uranium onto nanoporous silica adsorbent in the presence of nitrate, sulfate, chloride, fluoride and phosphate was studied. The effect of contact time between the nanoporous sorbent and aqueous solution, pH and initial concentration of uranium was also investigated. Uranium sorption onto nanoporous silica adsorbent is a very fast process as sorption rate increases with pH increment. Optimum pH for uranium sorption was 4-8. Experimental sorption isotherm is successfully described by Langmuir and Freundlich models. The results obtained by batch experiments showed that the presence of high concentration of nitrate, sulfate, chloride and phosphate anions alone had... 

    Immobilization of penicillin G acylase on non-porous ultrafine silica particles

    , Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 295-299 ; 10263098 (ISSN) Fazelinia, H ; Kheirolomoom, A ; Sharif University of Technology
    Sharif University of Technology  2005
    In this paper, immobilization of penicillin G aclylase onto non-porous ultrafine silica particles has been studied. The amount of penicillin G acylase immobilized was increased by increasing the free enzyme concentration and, at 0.45 mg/ml concentration of the free enzyme, 80% of the enzyme was immobilized. The optimum pH for immobilization was found to be 7.0, close to the pl of the enzyme. Although immobilization of the enzyme on ultrafine silica particles with and without glutaraldehyde showed almost the same activities, the enzyme immobilized with glutaraldehyde retained its initial activity much longer during 40 cycle-repeated batches with a half life of 163.2 h. © Sharif University of... 

    Production of low ester (LM) pectin by de-esterification of high ester (HM) apple pectin

    , Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 306-310 ; 10263098 (ISSN) Alemzadeh, I ; Saifkordi, A. A ; Kahforooshan, D ; Nahid, P ; Sharif University of Technology
    Sharif University of Technology  2005
    In this paper, LM pectin production from commercial apple pectin by using acid, alkali and ammonia methods in the presence of ethanol was studied. Also, the effect of different parameters such as, temperature, time, acid, alkali and ammonia treatment in LM pectin production were evaluated. In all the experiments, low temperature showed a better influence from a recovery, purity and low de-polymerization viewpoint. Optimum conditions in the acid method reached at pH = 2, t = 17 hrs and T = 30°C, in the alkaline method reached at pH = 11, t = 3 hrs and T = 5°C and in the ammonia method reached at 2 N ammonia and T = 5°C, were determined. © Sharif University of Technology  

    Synthesis and absorbency of gelatin-graft-poly(sodium acrylate-co- acrylamide) superabsorbent hydrogel with saltand pH-responsiveness properties

    , Article E-Polymers ; 2006 , Pages 1-15 ; 16187229 (ISSN) Pourjavadi, A ; Sadeghi, M ; Mahmodi Hashemi, M ; Hosseinzadeh, H ; Sharif University of Technology
    European Polymer Federation  2006
    In this article, we synthesize a novel gelatin-based superabsorbent hydrogel via graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N-methylene bisacrylamide (MBA) as a crosslinker. The hydrogel structures were confirmed by FTIR spectroscopy. The effect of grafting variables, i.e. concentration of MBA and APS, AA/AAm weight ratio, and reaction time and temperature, was systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The swelling behavior of these absorbent polymers... 

    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... 

    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... 

    Experimental investigation and thermodynamic modeling of amino acids partitioning in a water/ionic liquid system

    , Article Journal of Molecular Liquids ; Volume 260 , 15 June , 2018 , Pages 386-390 ; 01677322 (ISSN) Nazem, H ; Ghotbi, C ; Habibi Zare, M ; Shirazian, S ; Sharif University of Technology
    Elsevier B.V  2018
    Amino acids partitioning including phenylalanine, glutamic acid, and tryptophan in aqueous and ionic liquid phases at temperature of 298.15 K and atmospheric pressure were measured. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide used in this work can produce two phases with water immediately. The effect of aqueous solution pH on amino acids partitioning was studied and revealed that amino acid partitioning coefficient was decreased with increasing pH. This phenomenon pertains to the electrostatic interaction between cations of amino acid and the anions of ionic liquid which is decreased when pH increases. Considering the effect of pH, liquid-liquid equilibrium data of amino... 

    Selective separation of Congo Red from a mixture of anionic and cationic dyes using magnetic-MOF: Experimental and DFT study

    , Article Journal of Molecular Liquids ; Volume 318 , 2020 Mirzaee Valadi, F ; Ekramipooya, A ; Gholami, M. R ; Sharif University of Technology
    Elsevier B.V  2020
    La-MOF-NH2@Fe3O4 (magnetic-MOF) was used as an efficient, ultrafast, and selective adsorbent for the separation of Congo Red (CR) with 92.02% removal after 2 min. The magnetic-MOF was identified by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Zeta Potential analysis, analysis of the magnetic hysteresis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Kinetics, isotherms, the effect of pH, thermodynamic, and selectivity of CR adsorption were investigated. The results confirmed that the adsorption kinetics complied with the pseudo-second-order model. 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... 

    Uranium(VI) sorption behavior onto amberlite CG-400 anion exchange resin: Effects of pH, contact time, temperature and presence of phosphate

    , Article Annals of Nuclear Energy ; Volume 48 , October , 2012 , Pages 21-24 ; 03064549 (ISSN) Semnani, F ; Asadi, Z ; Samadfam, M ; Sepehrian, H ; Sharif University of Technology
    Elsevier  2012
    In this paper, uranium sorption onto amberlite CG-400 anion exchange resin in the presence of phosphate anions was studied. The effect of contact time between the sorbent and aqueous solution, pH, initial concentration of uranium and temperature were also investigated. Kinetic studies show that uranium sorption onto amberlite CG-400 resin in the presence of phosphate is a fast process and follows pesudo-second-order kinetics. It was also found that the pH value and the presence of phosphate play very important roles in the uranium sorption onto CG-400 resin. Optimum pH for uranium sorption in the presence of phosphate anions was about 3.5. The experimental sorption isotherm is successfully... 

    Performance of a single chamber microbial fuel cell at different organic loads and pH values using purified terephthalic acid wastewater

    , Article Journal of Environmental Health Science and Engineering ; Volume 13, Issue 1 , April , 2015 ; 2052336X (ISSN) Marashi, S. K. F ; Kariminia, H. R ; Sharif University of Technology
    BioMed Central Ltd  2015
    Background: Purified terephthalic acid (PTA) wastewater from a petrochemical complex was utilized as a fuel in the anode of a microbial fuel cell (MFC). Effects of two important parameters including different dilutions of the PTA wastewater and pH on the performance of the MFC were investigated. Methods: The MFC used was a membrane-less single chamber consisted of a stainless steel mesh as anode electrode and a carbon cloth as cathode electrode. Both power density and current density were calculated based on the projected surface area of the cathode electrode. Power density curve method was used to specify maximum power density and internal resistance of the MFC. Results: Using 10-times,... 

    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... 

    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... 

    Effect of pH and carbon nanotube content on the corrosion behavior of electrophoretically deposited chitosan-hydroxyapatite-carbon nanotube composite coatings

    , Article Ceramics International ; Volume 39, Issue 5 , July , 2013 , Pages 5393-5402 ; 02728842 (ISSN) Batmanghelich, F ; Ghorbani, M ; Sharif University of Technology
    In the first stage, chitosan (CH)-hydroxyapatite (HA)-multiwalled carbon nanotube (MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. In the next stage, effects of pH and MWCNT content of the suspension on the corrosion behavior and deposition mechanism were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves... 

    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... 

    Influence of key parameters on crude oil desalting: An experimental and theoretical study

    , Article Journal of Petroleum Science and Engineering ; Volume 90-91 , July , 2012 , Pages 107-111 ; 09204105 (ISSN) Vafajoo, L ; Ganjian, K ; Fattahi, M ; Sharif University of Technology
    Desalting plants are often installed in crude oil production units in order to remove water-soluble salts from an oil stream. Experiments in both the laboratory and field have shown the desalting process parameters to be very complicated. This research reflects the results of a study conducted regarding the impact of operational desalting parameters, including the effects of temperature, injected chemicals and the pH of the crude oil associated water, on an electrostatic desalter on one of the oil platforms owned by the Iranian Oil Offshore Company in the Persian Gulf. The temperature range applied was between 98 to 133 °C, at which the effects on water and oil density as well as salt... 

    Adsorption behavior of toxic metal Ions on nano-structured CuO granules

    , Article Separation Science and Technology (Philadelphia) ; Volume 47, Issue 7 , 2012 , Pages 1063-1069 ; 01496395 (ISSN) Ahmadi, S. J ; Sadjadi, S ; Hosseinpour, M ; Sharif University of Technology
    In this study, copper oxide nano particles were synthesized by batchwise supercritical hydrothermal method. After preparation of CuO nano particles, they were immobilized into the porous matrix of sodium alginate. The drying process formed a very porous structure that is useful for enhancing of adsorption activity. Produced CuO particles were characterized by X-ray diffractometery (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and BET for measuring the surface area. The prepared materials were then used as adsorbent in the removal of toxic metal ions in aqueous solution. To optimize the adsorption system, the effect of various parameters such as adsorbent... 

    Reprint of: Extraction of fluoxetine from aquatic and urine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by spectrofluorimetric determination

    , Article Analytica Chimica Acta ; Volume 716 , February , 2012 , Pages 61-65 ; 00032670 (ISSN) Bagheri, H ; Zandi, O ; Aghakhani, A ; Sharif University of Technology
    A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe 3O 4 nanoparticles (NPs) as a sorbent. The unique properties of Fe 3O 4 NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe 3O 4 and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully... 

    Use of response surface methodology for evaluation of effective parameters in codeposition of Cu-Sn alloys using non-cyanide electroplating solution

    , Article Transactions of the Institute of Metal Finishing ; Volume 90, Issue 1 , January , 2012 , Pages 38-43 ; 00202967 (ISSN) Asnavandi, M ; Ghorbani, M ; Sharif University of Technology
    A pyrophosphate based solution, as an acidic electrolyte, was developed for bronze electroplating. By using a statistical experimental design, response surface method, the effects of five factors [copper concentration (Cu), tin concentration (Sn), pyrophosphate concentration (P), current density j and pH] on the composition of the electroplated alloy as well as the process efficiency were evaluated. Statistical analysis indicated that all the parameters were significant and a second order polynomial model was successfully fitted to the data for both the alloy composition and the process efficiency. Based on the results obtained, a solution of Cu(II)8.04 g L -1, Sn(II)=26.36 g L -1, P=113.22...