Sharif Digital Repository

In this research, antimony extraction by hydrometallurgical method has been investigated using an alkaline medium. Stibnite ore, as a source of antimony was leached in alkali potassium hydroxide solution. Furthermore, related kinetic equations and process factors were also studied. It was determined that optimum conditions occure when the concentration of KOH is 0.5 mol /L, the solid to liquid ratio is 100 g/L, the reaction temperature is 25 °C, and the process is performed in 115 minutes. It was found that diffusion through the ash layer controls the reaction kinetics during the first 60 minutes. Finally, for the first time, the effect of different parameters on antimony electrowinning was... 

The enormous benefits of hydrometallurgical processes have led to the progressive metals extraction industry. Many studies are carried out on the application of these processes in the copper extraction industry. In this research, the oxygen pressure leaching of chalcopyrite concentrate 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 2M in a stainless-steel autoclave system. Central composite design (CCD) was used to design experiments, and three factors of temperature, time, and pressure of oxygen, were selected as design variables. The obtained model for %Cu includes parameters of... 

Molybdenum disilicide is an intermetallic compound in Mo-Si binary system that has very applications because of its individual properties. High melting point of MoSi2 limits the fabrication of this compound by conventional methods. Nowadays modern techniques such as Mechanical Alloying are used for synthesis of Molybdenum disilicide. In this investigation the MoSi2 has been synthesized from the elemental powders by Mechanically activated Self propagating Reaction method and the effect of milling atmosphere on synthesis efficiency is discussed  

Because of the importance and value of Superalloy, In this research has been treid to remelting scrap of gas turbine blades cobalt based Superalloy X-45, In order to restore it to the cycle of consumption. For this purpose, scraps were remelted under different conditions, for example changing the atmosphere, changing slag composition, changing type of the furnace for remelting and changing time of remelting process. Then in order to investigate effect of the above factors, microstructure were studied by optical microscope and Scanning Electron Microscopy (SEM) And also in order to investigate changings of element composition, chemical analysis were examined by atomic absorption analysis and... 

The current study was carried out to investigate the pressure oxidative leaching of the molybdenite concentrate in nitric acid to produce molybdic oxide (technical grade) and liquor containing entire rhenium of the concentrate and molybdenum. In the first step The Taguchi method was established to design and minimize the number of experiments. By using Taguchi orthogonal (L25) array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration) in 5 levels were selected for 25 experiments. 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 ReS2... 

High advantages of hydrometallurgy have led to its recent development in metal extraction. Many investigations are being carried out on applying hydrometallurgy processes on copper extraction. In this study, the chloride leaching of chalcopyrite in a concentrated sodium chloride solution (4M) –which is a novel process–, using CuCl2 as leachant is investigated. Main effects and interactions of temperature (50–90°C), time (2–6 hr), CuCl2 concentration (0.1–0.5M), pulp density and HCl concentration (0.1–1M) at constant stirring rate (600 rpm) on leaching is studied using 2k factorial design and applying Design–Expert 7.0.0 software. While the effect of pulp density is almost negligible,... 

In the present study, nanocomposite of Ce-TZP/Al2O3 was synthesized via aqueous combustion synthesis. In order to investigate the effects of alumina on the morphology and the mechanical properties of this nanocomposite, four sample with 20, 40, 60 and 80 mole percent of alumina were prepared. At first, the synthesized powders were characterized with scanning electron microscope and X-ray diffraction technique. Then, in order to determine the effects of alumina mole percent on the mechanical properties of the nanocomposite, the powders were uniaxailly compacted with the press of 250 MPa followed by sintering at the temperature of 1400 °C for 4 hours. The density of the compacted powders was... 

In the present work,the effect of solidification rate on the electrochemical behavior of copperanodes of Sarcheshmeh copper complex has been studied.Inthis regard, three cylindrical coppers pecimens with different solidificationrates casted into water-cooled metal mold (A specimen), metal mold (B specimen) and sand mold (C specimen). Cylinders for microstructural and electrochemical investigation, alongthickness dividedinto several specimens. To investigate themicrostructure of the specimens, opticalmicroscopyand scanning electron microscopy(SEM)were used. ICP testhasbeen usedforelemental analysis of each specimen; and eventuallytoinvestigate theelectrochemical behavior ofeach of... 

The photovoltaic (PV) industry is in rapid growth and a large supply of PV feedstock materials must be provided to maintain this growth. Since silicon is still the dominant material for the fabrication of solar cells, low-cost solar-grade silicon (SoG-Si) feedstock is demanded. The most cost-effective and direct approach for producing SoG-Si is to purify and upgrade metallurgical-grade silicon. The major impurities in silicon are Al, Fe and Ca. other impurities present are Cu, Ti , Zn, Ni, Cr, Mn, Cd, B and P. In this study The effects of the acid leaching process parameters, including the particle size of silicon, the acid type (HCl, HNO3, H2SO4, and their combination), tmepreture and the... 

In copper electrorefining process, to control Nickel and other impurities concentration and avoiding copper cathode contamination, a certain volume of electrolyte is withdrawn continuously from the circulation system and replaced by fresh electrolyte. The spent electrolyte includes valuable elements such as Nickel, Copper, Iron and also great value of sulfuric acid which is worthwhile to be recycled. Solvent Displacement Crystallization (SDC) method is suitable for this purpose because it retains significant amount of acid and have low energy consumption. The present work studies the using of SDC method to recover Nickel and other impurities from Sarcheshme Copper bleed solution and... 

The most important raw material for production of titanium dioxide is titanium that used in Aerospace, Plastic, Pigment and Pharmacy industries. Due to the presence of titanium minerals in Iran, reduce imports of titanium dioxide is one of the goals of the Ministry of Industries and Mines to achieve self-sufficiency in the production of TiO2.One of the very rich sources of titanium is alluvial sands in northern of Iran. In this study the TiO2 high grade pigment production from these sources has been investigated. Titanium-bearing sands with 9.5% TiO2 are used to produce high grade TiO2 pigment. After magnetic separation stage and reach a purity of 16.2% TiO2, upgrading slag step is not... 

The term “Rare Earth”, represents 17 metalic elements such as Sc, Y and Lanthanides wich have similar chemical properties. Lanthanides are a group of elements with atomic numbers of 57 to 71 that all of them exept Pm are present in nature. Rare earth elements are never concentrated in a special mine rock, but they could be found in various rocks and at very low concentrations. In the present study, apatite concentrate of Chadormalu was used for leaching and solvent extraction of Cerium, Lanthanum and Neodymium. After leaching step, its optimum conditions were found as follow: 30% nitric acid, 10 mins time and 10% for solid to liquid ratio. After finding optimum conditions, sufficient leach... 

Titanium dioxide is one of the most important first material in many industrial applications and for producing Titanium.Although it was discovered more than 200 years ago and has been commercially processed for 85 years, it is still being actively investigated. So far Iran imports TiO2. But some projects have been planned to produce pure TiO2 from Ilmenite and Titanomagnetite ore. In the present work production of highly purity TiO2 from Ilmenite ore by chloride leaching has been investigated. Chloride leaching has been accomplished by several stages of leaching in hydrochloric acid, reduction, crystallization, hydrolysis and finally calcination of the powder. According to the result... 

In this research, Chadormalou apatite concentrate was dissolved by 40% nitric acid and a solid to liquid ratio of 0.4 at 70 ° C for 2 hours, and its rare earth elements were dissolved. Recovery percents for Cerum, Neodymium and Lanthanum were 62.4, 48.7 and 49.6, respectively. In the solvent extraction step, the effect of HQ concentration as extractant, pH, temperature and phase ratio on the concentration of the adsorbed elements in organic phase, extraction percentage, distribution ratio and separation factor of rare earths were investigated. Organic solutions containing HQ in the kerosene alone pricipitated after contacting with PLS solutions. In order to prevent HQ pricipitation in the... 

Gold is a noble and precious metal used in various industries, including jewelry, electrical and electronic, catalyst, and medical industries. Multiple processes are used to extract and refine gold; each one has its advantages and disadvantages. In this research Work, comprehensive information on the electrochemical purification process of gold from anode electrode with 75% crude gold and titanium cathode electrode in the chloride electrolyte solution is presented. To perform the purification process, first using the parameters and their levels, including temperature (30, 45, and 60 degrees Celsius), voltage (2, 2.2, and 2.4 volts), and acid concentration (1, 2, and 3 M), Design of... 

The foregoing note is a Ph.D. Thesis in Material Science and Engineering entitled "Leaching of hydrometallurgical treatment residue of zinc concentrate and Indium solvent extraction of solution". This research includes three stages of Roasting, Leaching, and solvent extraction. The scientific fundamentals and research background in all three domains have been studied. Investigations on the Roasting of zinc sulfide concentrate showed that in order to prevent the ingestion of indium into the zinc ferrit structure, the alkaline roasting process with 15% calcium oxide at 850 0C and 150 min prevented the ingression of 80% of the indium into the ferritic structure. The results of studies on the... 

The extraction of molybdenum and rhenium from acidic solution produced by pressure leaching of molybdenite concentrate, using organophosphorus solvents has been investigated. First, extraction of molybdenum by Di-2-EthyHexyl Phosphoric Acid (D2EHPA) extractant dissolved in kerosene diluents was done. Extraction experiments were designed using Taguchi L16b orthogonal array. The effects of four factors: Shaking time, Organic solvent concentration, Organic to aqueous phase ratio, pH were studied in four levels. Optimum conditions occur at: shaking time: 35 min, organic solvent concentration: 30 volumetric percent, organic to aqueous phase ratio: 3, pH: 7 and molybdenum is completely extracted.... 

In recent decades, various studies have performed on leaching of sulphide ores in ammoniacal thiosulphate solution for the recovery of precious metals such as gold and silver and significant results have been gained. In this study, the ammonia thiosulfate solution utilized to dissolve copper sulfide concentrate, which contained chalcopyrite. The effect of various parameters such as grain size, thiosulfate and ammonia concentration, solid to liquid ratio, temperature and pH in turbulent leaching process were considered to obtain the optimum conditions in the laboratory scale. The outcomes obtained by chemical analysis were evaluated. The results demonstrate that maximum dissolution (26.72%)... 

In this study, nano-powders of copper-cobalt spinel (CuCo2O4) were fabricated by solution combustion synthesis (SCS) of Cu and Co nitrates with urea, glycine,acid citric and alanine. The method involved exothermic decomposition of viscous liquid nitrates and the fuel. Products which were synthesized by using this fuels contained less impurity constituents. Duo to low purity, other factors which have influence on synthesis process investigated and observed that pH have key role on process. X-ray diffraction (XRD) patterns gave crystal structure and the existing phases. Particle size distribution and morphology changes were studied by dynamic light scattering (DLS) and field emission scanning... 

In this project alumina-zirconia-ceria nanocomposite with 80% mol alumina (0.2Ce0.1Zr0.9O2-0.8Al2O3) was produced by solution combustion synthesis method. In the mentioned method, optimal fuel with composition of 75% urea, 25% ammonium acetate, and stoichiometric amount of glycine (0.75U-0.25AA-1G) was used. Moreover, ammonium nitrate as aid combustion was added to optimal fuel. In order to calcinations, nanopowder obtained from combustion synthesis was heated to 500°C for 1 hour and kept at this temperature for 2 hours. To complete heat treatment, the nanopowder was heated to 1150°C for 2 hours and 10 min and kept at this temperature for 2 hours. Then the specimens were pressed at pressure...