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Factors affecting platinum extraction from used reforming catalysts in iodine solutions at temperatures up to 95 °C
, Article Hydrometallurgy ; Volume 97, Issue 1-2 , 2009 , Pages 119-125 ; 0304386X (ISSN) ; Baghalha, M ; Sharif University of Technology
2009
Abstract
Platinum extraction from the spent reforming catalysts in iodine-iodide solutions at temperatures from 25 to 95 °C was investigated. The reforming catalyst mostly consists of a porous gamma alumina support with metallic platinum finely dispersed on the walls of the nano-pores of the catalyst support. The effect of a variety of factors, including catalyst particle size, impeller agitation speed, reactant concentrations, liquid to solid mass ratio, temperature and the solution pH on the Pt extraction rate and recovery were investigated. It was found that the catalyst particle sizes less than 106 μm and impeller agitation speed higher than 700 rpm eliminated the effects of catalyst size and...
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) ; Afshar, A ; Sharif University of Technology
Elsevier Editora Ltda
2019
Abstract
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 ; Saidi, M. H ; Sharif University of Technology
Bellwether Publishing, Ltd
2020
Abstract
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 ; 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
Abstract
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...
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 ; Ekramipooya, A ; Gholami, M. R ; Sharif University of Technology
Elsevier B.V
2020
Abstract
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...
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...
Mild steel carbon dioxide corrosion modelling in aqueous solutions
, Article Corrosion Engineering Science and Technology ; Volume 43, Issue 4 , 2008 , Pages 290-296 ; 1478422X (ISSN) ; Afshar, A ; Ghorbani, M ; Rahmaniyan, M ; Sharif University of Technology
2008
Abstract
A model for prediction of corrosion of mild steel in aqueous solutions containing carbon dioxide is proposed. In this model, formation of protective corrosion product is not yet considered, species concentration at the surface was calculated by using molecular diffusion phenomena and the diffusion equations were solved using the finite difference method. Calculated electrochemical currents at the steel surface may be used to determine the corrosion rate. The model was verified experimentally under atmospheric pressure and the effect of parameters, such as liquid velocity and pH, was investigated. The model can predict the electrochemical reaction rates when they were controlled by diffusion...
Effects of rubber curing ingredients and PhenolicResin on mechanical, thermal, and morphological characteristics of rubber/phenolic-resin blends
, Article Journal of Applied Polymer Science ; Volume 108, Issue 6 , 2008 , Pages 3808-3821 ; 00218995 (ISSN) ; Shojaei, A ; Faghihi, M ; Sharif University of Technology
2008
Abstract
This article examines the physical and mechanical characteristics of mixtures of two different synthetic rubbers, namely styrene-butadiene rubber (SBR) and nitril-butadiene rubber (NBR), with novolac type phenolicresin (PH). According to Taguchi experimental design method, it is shown that the addition of PH increases the crosslinking density of rubber phase probably due to its curative effects. Thermal analysis of the blends indicates that, contrary to NBR/PH blend, thermal stability of SBR/PH blend is dependent on sulfur content due to predominant polysulfidic crosslinks formed in SBR. Slight shift in glass-transition temperature (Tg) of pure SBR and NBR vulcanizates by the addition of PH...
Comparison of furfural degradation by different photooxidation methods
, Article Chemical Engineering Journal ; Volume 139, Issue 3 , 2008 , Pages 482-488 ; 13858947 (ISSN) ; Hosseini, S. N ; Sharif University of Technology
2008
Abstract
In this paper, the degradation of C5H4O2 "Furfural" in aqueous solution by photooxidation technology using UV, UV/H2O2, UV/H2O2/O2, UV/H2O2/Fe2+, UV/O2/Fe2+, O3, UV/O3 process and also oxidation by sodium hypochlorite was investigated in a lab-scale batch photo-reactor. To evaluate the performance of different processes, the efficiency of furfural degradation was studied by measuring the total organic carbon (TOC) throughout the experimentation. Results show that compare to other reactions studied in this research, the UV/H2O2 is a simple and effective process for furfural degradation and presence of Fe2+ ions (UV/H2O2/Fe2+) enhanced removal of furfural in solution. The influence of...
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...
Salt- and pH-resisting collagen-based highly porous hydrogel
, Article Polymer Journal ; Volume 40, Issue 2 , 2008 , Pages 94-103 ; 00323896 (ISSN) ; Kurdtabar, M ; Ghasemzadeh, H ; Sharif University of Technology
2008
Abstract
A novel approach was developed to prepare a highly porous hydrogel with superior salt- and pH-resisting properties. According to this method, synthetic comonomers, i.e. acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), were polymerized and crosslinked in the presence of hydrolyzed collagen as a natural backbone. The characterizations of hydrogels were investigated by swelling experiment, Fourier transform infrared (FT-IR) spectroscopy, acid-base titration and thermogravimetric analysis (TGA). Morphology of the samples was examined by scanning electron microscopy (SEM). Experimental results indicate that the hydrogel has an absorbency of 360 and 73-82 g/g for distilled...
Modified solvent microextraction with back extraction combined with liquid chromatography-fluorescence detection for the determination of citalopram in human plasma
, Article Analytica Chimica Acta ; Volume 610, Issue 2 , 2008 , Pages 211-216 ; 00032670 (ISSN) ; Khalilian, F ; Babanezhad, E ; Es haghi, A ; Rouini, M. R ; Sharif University of Technology
2008
Abstract
A modified solvent microextraction with back extraction method (SME/BE) combined with high performance liquid chromatography and fluorescence detection (HPLC-FD) was developed for the determination of citalopram in human plasma. Extraction process was performed in a home-made total glass vial without using a teflon ring, usually employed in SME/BE. Citalopram was first extracted from 0.5 mL of plasma, modified with sodium hydroxide, into hexane. Back extraction step was then performed into 5.2 μL of 45 mM ammonium formate solution (pH 4) using a GC microsyringe. The extract was subsequently transferred into a liner-like vial and then injected into the HPLC system. An enrichment factor of 150...
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) ; Torabi, S. F ; Ranaei Siadat, S. O ; Jalali Heravi, M ; Ghaemi, N ; Khajeh, K ; Sharif University of Technology
2007
Abstract
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...
Optimization of ferrous biooxidation rate in a packed bed bioreactor using Taguchi approach
, Article Chemical Engineering and Processing: Process Intensification ; Volume 46, Issue 10 , 2007 , Pages 935-940 ; 02552701 (ISSN) ; Yaghmaei, S ; Jafari, A ; Vossoughi, M ; Ghobadi, Z ; Sharif University of Technology
2007
Abstract
The biological oxidation of ferrous ion by iron-oxidizing bacteria is potentially a useful industrial process for removal of H2S from industrial gases, desulphurization of coal, removal of sulfur dioxide from flue gas, treatment of acid mine drainage and regeneration of an oxidant agent in hydrometallurgical leaching operations. The main purpose of this study was to find optimum values of the process parameters on the ferrous biooxidation rate by immobilization of a native Sulfobacillus species on the surface of low density polyethylene (LDPE) particles in a packed-bed bioreactor using Taguchi method. Five control factors, including temperature, initial pH of feed solution, dilution rate,...
Water adsorption in the organic phase for the D2EHPA-kerosene/water and aqueous Zn2+, Co2+, Ni2+ sulphate systems
, Article Hydrometallurgy ; Volume 88, Issue 1-4 , 2007 , Pages 92-97 ; 0304386X (ISSN) ; Haghshenas, D. F ; Etemadi, S ; Keshavarz Alamdari, E ; Sadrnezhaad, Kh ; Sharif University of Technology
2007
Abstract
Water adsorption by bis-2-ethylhexyl phosphoric acid (D2EHPA) during the extraction of zinc, cobalt and nickel using a D2EHPA-kerosene/H2O mixture is investigated. Based on the experimental results, about 1 mol of water is adsorbed by 2 mol of D2EHPA (which exists in the form of a dimer), irrespective of the pH. Water adsorption decreases with presence of zinc, cobalt and nickel. The stoichiometric coefficients of D2EHPA in water adsorption reactions are determined with and without zinc, cobalt and nickel by applying the slope-analysis method. It is experimentally confirmed that 1.0, 1.8 and 1.2 mol of adsorbed water will be rejected from the organic phase when zinc, cobalt and nickel are...
Synthesis and properties of biodegradable hydrogels of κ-carrageenan grafted acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid as candidates for drug delivery systems
, Article Reactive and Functional Polymers ; Volume 67, Issue 7 , 2007 , Pages 644-654 ; 13815148 (ISSN) ; Barzegar, Sh ; Zeidabadi, F ; Sharif University of Technology
2007
Abstract
Novel types of highly swelling hydrogels were prepared by grafting crosslinked polyacrylic acid-co-poly-2-acrylamido-2-methylpropanesulfonic acid (PAA-co-PAMPS) chains onto κ-carrageenan through a free radical polymerization method. Here, we propose a mechanism for κ-carrageenan-g-PAA-co-PAMPS formation and confirm the hydrogel structure using FTIR spectroscopy. The effect of grafting variables (i.e. concentration of methylenebisacrylamide (MBA), acrylic acid/-2-acrylamido-2-methylpropanesulfonic acid (AA/AMPS) weight ratio, ammonium persulfate (APS), κ-carrageenan, neutralization percent and reaction temperature) were systematically optimized to achieve a hydrogel with a maximum swelling...
Leaching of an oxide gold ore with chloride/hypochlorite solutions
, Article International Journal of Mineral Processing ; Volume 82, Issue 4 , 2007 , Pages 178-186 ; 03017516 (ISSN) ; Sharif University of Technology
2007
Abstract
An oxide gold ore was subjected to chloride/hypochlorite leaching at room temperature. The effects of three factors, including Ca(OCl)2 vs. NaOCl, OCl- concentration, and HCl concentration on gold leaching performance were investigated. Due to formation of CaOCl+ complex in solution and hence less reactivity, calcium hypochlorite produces a sluggish gold leaching kinetics, taking twice the time (46 h) to achieve maximum gold recovery of 58% compared to sodium hypochlorite. 10 g/L of total initial hypochlorite species in solution produces reasonable gold recoveries. The amount of added HCl and hence the initial pH was found to have a major effect on gold leaching kinetics and maximum gold...
Collagen-based highly porous hydrogel without any porogen: Synthesis and characteristics
, Article European Polymer Journal ; Volume 43, Issue 3 , 2007 , Pages 877-889 ; 00143057 (ISSN) ; Kurdtabar, M ; Sharif University of Technology
2007
Abstract
In this contribution we have developed a collagen-based highly porous hydrogel by neutralizing the grafted poly(acrylamide-co-acrylic acid) after gel formation. Preparation of the hydrogels involved free radical polymerization of a combination of hydrolyzed collagen, acrylic acid (AA), acrylamide (AAm) and distilled water, in appropriate amounts and contained a crosslinking agent called N,N′-methylene bisacrylamide (MBA). The chemical structure of the hydrogels was characterized by means of FTIR spectroscopy, DSC and TGA thermal methods. Morphology of the samples was examined by scanning electron microscopy (SEM). Systematically, the certain variables of the graft copolymerization were...
Bacterial leaching of low-grade ZnS concentrate using indigenous mesophilic and thermophilic strains
, Article Hydrometallurgy ; Volume 85, Issue 1 , 2007 , Pages 59-65 ; 0304386X (ISSN) ; Yaghmaei, S ; Vossoughi, M ; Jafari, A ; Roostaazad, R ; Turunen, I ; Sharif University of Technology
2007
Abstract
In this study low-grade sphalerite has been treated by the bioleaching process using native cultures of Acidithiobacillus ferrooxidans and Sulfobacillus thermosulfido-oxidans in order to determine the ability of these bacteria to the leaching of zinc. The effects of bacterial strain, pH, temperature, pulp density, iron precipitation, and initial concentration of ferric iron on the zinc leaching were evaluated. The bioleaching experiments were carried out in shake flasks at pH 1.5, 180 rpm, 33 °C and 60 °C for mesophilic and thermophilic bacteria, respectively. Compared with the use of laboratory reference strains or control conditions, zinc recovery from the respective concentrate was...
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...