Search for: leaching
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    Oxidation pretreatment for enhancing desulfurization of coal with sodium butoxide

    , Article Minerals Engineering ; Volume 17, Issue 4 , 2004 , Pages 545-552 ; 08926875 (ISSN) Jorjani, E ; Rezai, B ; Vossoughi, M ; Osanloo, M ; Abdollahi, M ; Sharif University of Technology
    A sample of Tabas coal from Iran was oxidized using air, peroxyacetic acid (PAA), and PAA+air as a pretreatment for desulfurization with sodium butoxide in a batch reactor. The effects of air oxidation temperature, PAA oxidation time, sodium butoxide reaction time and temperature, solvent concentration and particle size on the reduction of sulfur were investigated. The PAA+air oxidation pretreatment was the most effective method for enhancing sulfur removal. This procedure increased pyritic sulfur removal by approximately 15% and organic sulfur removal by 20% in leaching with sodium butoxide. Increasing the temperature from 25 (unoxidized) to 100 °C on air oxidized samples, increased sulfur... 

    Optimization of acid leaching of rutile containing slag using factorial based response surface modeling

    , Article Indian Journal of Science and Technology ; Volume 9, Issue 4 , 2016 , Pages 1-8 ; 09746846 (ISSN) Abazarpoor, A ; Halali, M ; Khatibnezhad, H ; Sharif University of Technology
    Indian Society for Education and Environment  2016
    In this study the leaching of a high rutile containing slag in sulphuric acid has been investigated to find optimum leaching conditions. Using "Fractional Factorial" technique it was deduced that leaching temperature and duration, acid concentration and particle size are the most prominent parameters in the leaching process. The optimization of the leaching process was investigated using the "Rotatable Central Composite Design" technique. The four prominent parameters were studied at 5 different test values each. 3D response surface was employed to illustrate interaction of the parameters. The optimum leaching conditions for the ilmenite concentrate are thus recognized as: T = 123.9°C, time... 

    Oxidative leaching of chalcopyrite by cupric ion in chloride media

    , Article Transactions of the Indian Institute of Metals ; Volume 73, Issue 4 , 2020 , Pages 989-997 Rasouli, S ; Mojtahedi, B ; Yoozbashizadeh, H ; Sharif University of Technology
    Springer  2020
    In this study, chalcopyrite concentrate produced in Sarcheshmeh copper plant was subjected to oxidative leaching investigation by cupric ion to determine the effect of several parameters on the copper and iron dissolution, including temperature of leaching, time of holding and cupric concentration as oxidant agent in a range of 38–97 °C, 1.5–8.5 h and 0.2–0.8 M, respectively. The leaching media was chloride providing with 3 M HCl 37% and CuCl2. The experiments were designed by central composite design method. The dissolution of copper and iron was examined. The maximum dissolution of copper 62.64%, was obtained at 85 °C, 7 h and oxidant concentration of 0.7 M. The kinetics model of... 

    Pressure leaching of chalcopyrite concentrate with oxygen and kinetic study on the process in sulfuric acid solution

    , Article Transactions of the Indian Institute of Metals ; Volume 73, Issue 4 , 6 March , 2020 , Pages 975-987 Mojtahedi, B ; Rasouli, S ; Yoozbashizadeh, H ; Sharif University of Technology
    Springer  2020
    In this research work, the pressure leaching of chalcopyrite concentrate with oxygen was studied. Experiments were carried out under conditions of the solid–liquid ratio of 0.1, agitation speed of 750 rpm, and sulfuric acid concentration of 2 M in a stainless-steel autoclave system under 0.6 to 1 MPa oxygen gas. Central composite design was used to design experiments, and three factors of temperature, time, and oxygen pressure were selected as the design variables. A linear model for %Cu and a quadratic model for %Fe were proposed by Minitab Software. The results showed that temperature is the most effective factor in chalcopyrite leaching. Under optimal conditions, 93.08% of copper with the... 

    Micro-stratigraphical investigation on corrosion layers in ancient Bronze artefacts by scanning electron microscopy energy dispersive spectrometry and optical microscopy

    , Article Heritage Science ; Volume 1, Issue 1 , 2013 ; 20507445 (ISSN) Oudbashi, O ; Emami, S. M ; Ahmadi, H ; Davami, P ; Sharif University of Technology
    Background: Archaeological metallic artefacts buried in soils deteriorate by means of various environmental as well as internal factors and mechanisms over time such as change in composition and microstructure of metal and corrosive factors due to long-term burial environment. Corrosion in metals occurs in different morphologies and results in different types of corrosion products based on soil composition. Identification of corrosion mechanisms and morphology in archaeological metals can help conservators to characterize deterioration occurred in metals and make decisions to protect artefacts about preventing further deterioration. In archaeological bronzes, different layers may form on the... 

    Determination of optimal conditions for pressure oxidative leaching of sarcheshmeh molybdenite concentrate using Taguchi method

    , Article Journal of Mining and Metallurgy, Section B: Metallurgy ; Volume 48, Issue 1 , 2012 , Pages 89-99 ; 14505339 (ISSN) Khoshnevisan, A ; Yoozbashizadeh, H ; Sharif University of Technology
    The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO 3) with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L 25) array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration) at five levels were selected for 25 experiments. The experiments were designed and carried out in a high-pressure reactor in the presence of nitric acid as solvent and oxidizing agent for the molybdenite concentrate and its ReS 2... 

    Kinetics of pressure oxidative leaching of molybdenite concentrate by nitric acid

    , Article Hydrometallurgy ; Volume 111-112, Issue 1 , January , 2012 , Pages 52-57 ; 0304386X (ISSN) Khoshnevisan, A ; Yoozbashizadeh, H ; Mozammel, M ; Sadrnezhaad, S. K ; Sharif University of Technology
    The current study was carried out to investigate the kinetics of reactions for the pressure oxidative leaching of a molybdenite concentrate in less than one hour. The effects of oxygen pressure, stirring speed, pulp density, acid concentration and temperature on the leaching rate of the molybdenum were studied. It was found that about 85% of molybdenite was oxidized to molybdic oxide precipitate with remaining molybdenum dissolved in the leaching liquor. Analysis of experimental data showed that the reaction is chemically controlled with activation energy of 68.8 kJ/mol. Furthermore SEM images showed no significant boundary diffusion layer and it was noted that the molybdic oxide... 

    Application of artificial neural networks to predict pressure oxidative leaching of molybdenite concentrate in nitric acid media

    , Article Mineral Processing and Extractive Metallurgy Review ; Volume 33, Issue 4 , Jul , 2012 , Pages 292-299 ; 08827508 (ISSN) Khoshnevisan, A ; Yoozbashizadeh, H ; Sharif University of Technology
    Taylor and Francis Inc  2012
    This study is concerned with investigation of pressure oxidative leaching of entire molybdenum of a molybdenite concentrate. Effects of oxygen pressure, stirring speed, pulp density, acid concentration, and temperature on the leaching rate of molybdenum were studied. A three-layer feed-forward artificial neural network was applied to model the effect of the abovementioned parameters on the leaching ability. The leaching efficiency was considered as a target value for modeling. The quantified leaching efficiencies obtained by applying different parameters demonstrated a good agreement with neural network predictions  

    An Investigation on the Influence of EAF Slag Particle Size on AMD Neutralization Behavior in Static and Dynamic Slag Leaching Systems

    , Article Mine Water and the Environment ; Volume 34, Issue 2 , 2015 , Pages 204-212 ; 10259112 (ISSN) Alizadeh, A ; Shoushtari Zadeh Naseri, P ; Sharif University of Technology
    Springer Verlag  2015
    Steel slag, which contains basic oxides capable of generating high levels of alkalinity, may be used in leaching beds or leaching channels to neutralize acid mine drainage (AMD). In the present study, electric arc furnace (EAF) slag from the Pasargad Steel Complex was used to investigate the influence of slag particle size on AMD treatment. Three slag samples with different particle size distributions (coarse, mixed, fine) were prepared. Slag composition, pH variation, level of alkalinity, and specific surface area were measured and the surfaces of the slag particles was examined by scanning electron microscopy. In both dynamic and static leaching tests, there proved to be three stages: an... 

    Leaching kinetics of stibnite in sodium hydroxide solution

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 27, Issue 2 , February , 2014 , Pages 325-332 ; SSN: 10252495 Dodangeh, A ; Halali, M ; Hakim, M ; Bakhshandeh, M. R ; Sharif University of Technology
    The leaching kinetics of stibnite in basic solution has been investigated. Spherical pellets of antimony sulphide were dissolved in 1 molar sodium hydroxide solutions at different temperatures. It was found that the shrinking core with ash layer model could satisfactorily explain the dissolution process. Using this model, it was found that initially the rate controlling step was a chemical reaction with activation energy of 10.2 kJ/mol. As the ash layer built up, diffusion through the ash layer became the rate controlling step. The activation energy for this step was found to be 33.4 kJ/mol. It was also observed that smaller particle size, larger solid to liquid ratio, and higher NaOH... 

    The leaching kinetics of an oxide gold ore with iodide/iodine solutions

    , Article Hydrometallurgy ; Volume 113-114 , 2012 , Pages 42-50 ; 0304386X (ISSN) Baghalha, M ; Sharif University of Technology
    Two types of gold ores were subjected to iodide/iodine leaching at room temperature. The effects of three factors, including ore type (a carbonaceous and an oxide gold ores), iodide/iodine concentration, and the presence of oxygen in solution on gold leaching performance were investigated. The carbonaceous ore showed only 20% gold extraction, since gold-iodide complexes readily adsorb on organic matter. In contrast, gold extraction from the oxide ore in a solution containing 20 g/L iodide and 4 g/L iodine reached 77% in 6 h and 89% in 24 h. With iodate as the oxidant, no gold could be leached in 48 h. When the iodate was partially converted to iodine by adding HCl to the solution, gold... 

    Optimization of Leaching of Platinum Group Metals from Spent Car Catalytic Converters

    , M.Sc. Thesis Sharif University of Technology Ziari, Amir Hossein (Author) ; Halali, Mohammad (Supervisor)
    The catalytic converter converts 95 to 99 percent of the vehicle exhaust gases into environmentally friendly gases, which are installed between the engine and the vehicle's exhaust cistern. The catalyst contained in the converters includes a ceramic structure commonly used as an alumina, coated with metal catalyst of expensive metals of the platinum group (platinum, palladium and rhodium). The purpose of this project is to optimize the recovery of platinum group metals from automotive catalytic converters by hydrometallurgy by hydrochloric acid and oxygenated water as an additive using Design Expert software. In this project, using the factorial design, the effect of parameters of... 

    Copper recovery from reverberatory furnace flue dust

    , Article International Journal of Mineral Processing ; Volume 157 , 2016 , Pages 205-209 ; 03017516 (ISSN) Mohagheghi, M ; Askari, M ; Sharif University of Technology
    Elsevier, B. V  2016
    In this study, leaching of reverberatory furnace dust at Sarcheshmeh was investigated in H2SO4-O3 medium. Response surface methodology based on central composite face-centered design (RSM-CCF) was applied to optimize the operating parameters. The optimal conditions to achieve the principle objectives of maximizing copper dissolution and minimizing iron dissolution from dust were identified to be a temperature of 30 °C, a leaching time of 3 h, an initial pH of 0.5, a pulp density of 20%, and an ozone flow rate of 1 g/h. Under the optimum conditions, the copper and iron concentrations in the leaching solution were found to be 27.11 and 0.90 g/L, respectively. The results showed that selective... 

    Factors affecting the leachability of Ni/Co/Cu slags at high temperature

    , Article Hydrometallurgy ; Volume 85, Issue 1 , 2007 , Pages 42-52 ; 0304386X (ISSN) Baghalha, M ; Papangelakis, V. G ; Curlook, W ; Sharif University of Technology
    An oxidative pressure acid leaching process was investigated for the extraction of Ni/Co/Cu/Zn metal values from base metal smelter slags. The process is applicable to smelting furnace dump slags, as well as to mid-stream converter slags. In addition to the economical advantages, extracting the base metal values from the dump slags produces an environmentally benign residue. To produce high level of extraction for the metal values, it is necessary to have the slag in crystalline structure. This, in turn, requires cooling the molten smelter slags sufficiently slowly during solidification. It was shown that if the same slags are quenched in water thereby producing an amorphous structure, the... 

    Regeneration of Cobalt from Catalyst Deactivated in Fischer-Tropsch Synthesis

    , M.Sc. Thesis Sharif University of Technology Ahmadi, Ali Akbar (Author) ; Kazemeini, Mohammad (Supervisor) ; Rohani, Ali Asghar (Supervisor)
    In this work hydrometallurgical route for processing spent commercial catalysts (Co/Al2O3) are investigated for leaching the Cobalt component. The used catalysts were initially pre-oxidized at 500 °C and 5 h in order to eliminate coke and other volatile species present. Pre-oxidized catalysts were dissolved in solvents such as H2SO4, HNO3, HCl and H2O at 80-90 °C, and the remaining residues separated from the solution. These experiments were performed at different concentrations, presence and absence H2O2 solution. Also effect of reflux on leaching process investigated. The result show the yield of the pre-oxidized catalysts extracted with highly concentration of extractant is higher than... 

    Desulfurization of high sulfur petroleum coke by molten caustic leaching

    , Article Egyptian Journal of Petroleum ; Volume 28, Issue 2 , 2019 , Pages 225-231 ; 11100621 (ISSN) Askari, H ; Khorasheh, F ; Soltanali, S ; Tayyebi, S ; Sharif University of Technology
    Egyptian Petroleum Research Institute  2019
    Desulfurization by molten caustic leaching (MCL) at 400–500 °C has been investigated in order to reduce the sulfur content of petroleum coke. Effective parameters on desulfurization of petroleum coke, other than temperature, include alkali to feed (petroleum coke) mass ratio, time and mesh size in the ranges of 0.5–1.5, 1–3 h and 200–600 µm, respectively. In this work, petroleum coke desulfurization conditions using solid KOH have been studied. Maximum petroleum coke desulfurization by MCL method has been obtained by Taguchi L9 design using alkali to feed mass ratio of 1, temperature of 600 °C, time of 2 h and mesh size of 200 µm. The changes in the main groups on the coke surface have been... 

    Advances in bioleaching of copper and nickel from electronic waste using Acidithiobacillus ferrooxidans: evaluating daily pH adjustment

    , Article Chemical Papers ; Volume 74, Issue 7 , 2020 , Pages 2211-2227 Arshadi, M ; Yaghmaei, S ; Sharif University of Technology
    Springer  2020
    Abstract: The waste stream of electrical and electronic equipment is three times faster than other municipal waste streams. Recycling of electronic waste is necessary for both reducing environmental pollution and saving natural ores. Bioleaching is known as an efficient technology for metal leaching. In most of the previous studies on the bioleaching of electronic waste, the pH of the process was adjusted daily under the optimal pH of the bacterium growth. Using acid causes increasing process costs and unsustainability of the process. In this work, the effect of daily pH adjustment on the bioleaching efficiency of electronic waste using adapted Acidithiobacillus ferrooxidans was studied.... 

    Bioleaching of low-grade sphalerite using a column reactor

    , Article Hydrometallurgy ; Volume 82, Issue 1-2 , 2006 , Pages 75-82 ; 0304386X (ISSN) Mousavi, S. M ; Jafari, A ; Yaghmaei, S ; Vossoughi, M ; Roostaazad, R ; Sharif University of Technology
    The effects of several variables on zinc recovery in column bioleaching have been investigated. The ore contained sphalerite and pyrite as the main sulfide minerals and chalcopyrite and galena as minor minerals. Tests were carried out using a bench-scale column leach reactor which was inoculated with mesophilic (Acidithiobacillus ferrooxidans) and thermophilic (Sulfobacillus) iron oxidizing bacteria; initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran) and Kooshk sphalerite concentrate (Yazd, Iran), respectively. In the inoculated column, jarosite and elemental sulfur were formed. The leaching rate of sphalerite tended to increase with dissolved ferric ion... 

    The Routing Problem in the Wireless Sensor Networks

    , M.Sc. Thesis Sharif University of Technology Javadi, Mahrokh (Author) ; Eshghi, Kourosh (Supervisor)
    Wireless sensor networks have been widely used in such areas as intelligent transport systems, military systems and etc. Wireless sensor networks are composed of a number of sensor nodes in charge of data collection, analysis and transport. The energy limitations on wireless sensors have brought researchers to work on algorithms intended for efficient use of energy and therefor maximum network life.
    In this work, we will first present a detailed description of two well-known protocols: LEACH and AODV. In the second part, an optimized routing protocol for wireless networks, based on the previously described protocols and the ant colony theory will be presented. The optimized protocol will... 

    Performance modeling of the LEACH protocol for mobile wireless sensor networks

    , Article Journal of Parallel and Distributed Computing ; Vol. 71, issue. 6 , 2011 , p. 812-821 ; ISSN: 07437315 Nayebi, A ; Sarbazi-Azad, H ; Sharif University of Technology
    In many wireless sensor network applications, nodes are mobile, while many protocols proposed for these networks assume a static network. Thus, it is important to evaluate if a traditional protocol designed for a static network can tolerate different levels of mobility. This paper provides an analytic model to investigate the effect of mobility on a well-known cluster-based protocol, LEACH. The model evaluates data loss after construction of the clusters due to node mobility, which can be used to estimate a proper update interval to balance the energy and data loss ratio. Thus, the results can help the network designer to adjust the topology update interval given a value of acceptable data...