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By Oleksandr Liaskovskiy, Sergey Beringov, Sergiy Yatsuk, Timur Vlasenko, Iryna Buchovska

"Working with solar-grade silicon for solar cells application usually meets some difficulties in comparison to polysilicon produced by Siemens method: higher impurities content leads to lower yield, worse electro-physical parameters and poor performance in solar cells application. However some adjustments in ingot production can show significant improvements in quality of final product: crystalline wafers and cells.Recent investigations have shown that solar-grade silicon is suitable for high effective production process such as mono-like multicrystalline wafer production. Production-scale lots made at Pillar show promising results for solar-grade silicon application: high-quality wafers with significantly big crystalline grains of <100> orientation.IntroductionThe standard technology of producing multicrystalline silicon ingots by directional solidification method in quartz crucibles has a number of disadvantages resulting in limited efficiency of solar cells made of multicrystalline material: crystallites of multicrystalline ingot are relatively small (down to 5 mm size), grain borders of crystallites contain parasitic impurities such as metals, silicon nitride etc., crystallographic orientation of crystallites is random. The listed deficiencies are an integral characteristic of the technology which affects the efficiency of solar cells, such as presence of solar cells with low efficiency even at a high level of average efficiency, problems with shunted cells, silicon nitride inclusions, which adversely affect cell efficiency and are centres for silicon carbide formation, impossibility of application of high effective alkaline texturing etc. Also with regard to the targets set by photovoltaic to reduce the cost per Wp in the nearest future, standard technology of multicrystalline silicon ingots production by directional solidification faces certain challenges some of which are hard to overcome due to rather low efficiency of solar cells made of multicrystalline wafers. Therefore alternative methods of multicrystalline silicon production for photovoltaic application having a number of advantages in comparison to traditional technology are developing rapidly."

Jan 1, 2012

By M. Mujahid, A. Maqsood, M. H. Asghar, K Iqbal

"Thin film multilayer anti-reflection coatings (Si02/Si/Si02) having thicknesses 286/571/143nm were deposited by RF magnetron sputtering deposition technique on 0.5mm thick Si(100)-substrates. Post-deposition annealing is also carried out in the temperature range 150-650°C for 4hr at the rate of 10°C /min. Si Optical window was designed at 4.21lm wavelengths and correlated with modeling software. The films are transparent in the 3-51lffi band of the electromagnetic spectrum, firmly adhered to the substrate. The prepared multilayer thin films are characterized optically and structurally using a spectrophotometer, an atomic force microscope, x-ray diffraction and a scanning electron microscope. Optical and structural characterizations show that the %transmittance is between 60% and 75%, no appreciable change in crystal structure and roughness of coatings vary between 9 and 25 nm when annealed in the temperature range of 150-650oC. Local elemental characterization on the surface of the thin film was carried out using energy dispersive spectroscopy. The quantitative result of energy dispersive spectroscopy has also shown that the ratio of Si to 0 on the film is 0.67: 1.IntroductionSi02 thin films have unique properties in the interfaces with Si and most studied materials in the field of microelectronics and optical devices [1]. Multilayer thin films are using nowadays in the design and fabrication of the shrinking systems with a variety of fields such as optoelectronic devices. The physical properties and parameters can be controlled at scales of microns down to nanometers by using RF magnetron sputtering system [2].Silicon and Silicon dioxide are used as coating materials [3]. These thin films are laid on top of each other in SiO2/Si/Si02 order by RF magnetron sputtering on top of a substrate as given in Table 1."

Jan 1, 2012

By Jose Castro

The growing demand of scrap to supply the electric arc furnace has driven to search for new alternatives of raw material. The DRI produced using self-reducing pellets has become competitive due to the potential use of a wide range of carbonaceous materials such as coal, charcoal, biomass etc. In this context, the rotary kiln process using improved technologies such as post-combustion and self-reducing burden is a promising source of high quality raw materials. This paper presents a mathematical model of the rotary kiln process designed for self-reducing pellets and post-combustion. The model is based on the transport equation of two-phase flow, energy and mass transfer. The solid material is composed of a typical self-reducing pellet. The model considers the solid phase (C, volatiles, Fe2O3, Fe3O4, FeO, Fe, H2O, SiO2, Al2O3, MgO, P2O5, K2O, Na2O, FeS, CaO and gangue) and the gas phase (N2, O2, CO, CO2, H2, H2O, SO, SO2 and SiO). For each of the above components a conservation equation is solved and the mass and energy transport is accounted. The set of differential equations are coupled by the rate equations describing the kinetics of the several reactions, which take place within the rotary kiln. All the conservation equations are solved based on the finite volume method applied for a three-dimensional cylindrical coordinate system. Simulation results are presented for global parameters such as metallization degree, productivity, gas utilization ratio and calorific value. Inner conditions such as three-dimensional gas and solid temperature patter and compositions are discussed.

Jan 1, 2006

By Shaohua Ju, Jin-hui Peng, Ya-jian Wang, Shuai-dan Lu, Li-bo Zhang, Lei Guo

"The granulation of a red mud is of great importance for recycling this material as an adsorbent for waste water or gas. A new granulating process was developed and its effect was evaluated. To reduce the cost of the granulation process, the wet filter cake (containing 25% water) was directly mixed with different cement contents (4%, 6%, 8% and 10% based on wet material). The mixtures were placed in a moist environment for 4 days, and then were washed with deionized water until the pH values of leachants were lower than 9.0. The efflorescence ratio, surface area and particle size of the aged mixture were determined, respectively, by bottle shaking experiments, N2 adsorption and screening. The results showed that the best addition of cement is 2%, and this yielded granulated material with a particle size of less than 2 mm, an efflorescence ratio of 4.83% and a specific surface area of 17.42 m2/g.IntroductionRed mud is a residue of the aluminium industry that is produced during the alkaline extraction of alumina from bauxite by the Bayer process. For every ton of alumina that is produced, the amount of red mud generated can vary from 0.3 to 2.5 tons, depending on the characteristics of the bauxite. In its typical form, red mud is brick red in colour, caustic, about three times as dense as water and, when un-neutralised, has a high pH, typically around pH 13 [1]. It is primarily composed of iron oxide, silica and alumina, along with traces of heavy metals. Red mud particles are quite small; typically 99% will pass through a 0.6 mm sieve and 87% through a 0.038 mm sieve [2],"

Jan 1, 2012

By Ting Luo, Hongmin Zhu, Kai Huang, Shuanglong Du, Tao Gui, Yifan Xiu

"Poplar cotton, a cellulosic material, was found to adsorb metals ions effectively. In the present study, the biosorption characteristics of Pb(II) onto poplar cotton, were evaluated as a function of pH, contact time, biomass dosage, initial concentration and temperature. Within the pH range investigated (1.0-6.0), the optimal pH value suitable for the uptake of Pb(II) was determined. The maximum adsorption capacity obtained from the Langmuir model is around 0.52mol kg for the poplar cotton sorbent. Equilibration is achieved in 60min for the studied concentrations. Results suggest that the poplar cotton can be directly used as an effective and low-cost biosorbent for removal of Pb(II) from aqueous solution.IntroductionHigh value utilization of various biowastes produced in agricultural, forestry, fishing industries, etc. have attracted great interest from many researchers [1], Biomass, due to its easy availability, great abundance, low cost, easy processing, eco-friendliness and biodegradability, has exhibited exciting potential for being used as raw materials for the preparation of many new hi-tech functional products [2]. For example, using biowastes to synthesize sorbents for application in the removal of toxic substances such as dyes [3], heavy metals from the waste water [4] or in the recovery of valuable metals [5] from the ore tailings and secondary metals resources has made great progress in last decade. In present study, poplar cotton, a kind of white light fluff of poplar trees, like that of dandelion, usually flying in the air each spring was tested as a biosorbent for the remove lead ions from the water. It may also provide some good ideas for new sorbent design. Lead, as one of the typical poisonous heavy metals, for its typical toxicity and extensive pollution, was chosen to test the adsorption behavior of poplar cotton in aqueous solutions."

Jan 1, 2012

By František Molnar, Zsolt Szentirmai, Juraj Schmiedl, Felix Sekula

"Hydrometallurgical nickel production in Sered Nickel Plant (Slovakia) that treated roasted Albanian ore left behind a considerable amount of the solid leaching residue. About 6 million tons of this fine-powder residue containing approximately 52 wt.% of iron in the form of oxides is to the present day stored in a stockpile. However, its iron content makes it a potentially interesting secondary raw material for iron production. This secondary raw material is not, unfortunately, suitable for direct treatment in iron and steelmaking processes.This paper presents results of the laboratory tests of pyrometallurgical method of processing of the leaching residue by its roasting and subsequent refining melting. The objective of the selective reducing agglomeration roasting was to reduce iron oxides and to simultaneously avoid reduction of chromium oxides and silica. Refining melting is carried out in an inert atmosphere. The products of melting are technically pure iron and slag.IntroductionThe leaching residue stockpiled on waste dump near already non-existing Nickel Plant Sered, Slovakia, is considered to be one of the most important environmental burdens in this country. The 40-years of an on-going effort focused on finding the methods for extracting metals and thus remove the waste dump have not been successful [1,4,5,6]. From the literature survey it is evident that past investigations have been following three main routes:1.Removal of chromium by mineral processing methods prior to its metallurgical treatment to achieve final chromium concentrations below 0.3 wt.%.2.Pelletization of solid leaching residue and its subsequent reduction in blast furnace and steelmaking plant and simultaneous removal of chromium.3.Pelletization of solid leaching residue followed by metallurgical processing of preliminary reduced semi-product in electric arc furnace (EAF) accompanied by partial reduction of chromium."

Jan 1, 2008

By Majid Sarkari, Hossein Atashi, Farhad Fazlollahi

"The aim of this research work was to prepare the efficient catalyst to purify pollutant output gases such as SO2 , NO2 and CO. This catalyst, lanthanum cobaltat (LaCo03) was prepared by the proper method in the analysis laboratory of Tabriz Oil .The first materials were chosen through calcination operation and temperatures of operation related to the Tamman temperature, therefore the basis for the first material of catalyst was nitrate and aqueous and since we had no availability to lanthanum nitrate, lanthanum oxide was used to prepare the nitrate one. Before all else, the first materials of catalyst were mixed together with the equal mole proportions and then, at the lower and upper temperatures of Tanunan temperature, calcination operation was carried out. To determine the molecular structure, the XRD analysis was utilized and specified that prepared lanthanum cobaltat was sixth aqueous and had the crystal structure type Triclinic.IntroductionLaCo03 has presented a vast interest because of its special electrical, magnetic and catalytic properties [1-4]. The catalyst LaCo03 can be prepared by means of several methods such as spray drying, freeze drying and also co-precipitation [5-12]. Some methods including hydrothermal, sol gel and citrate [13] This material usually has been synthesized by ceramic method and certainly the high temperature for the calcination operation. [14]. Lanthanum catalysts have been researched because of having such an active state [15]. One of the unique properties of this catalyst is the simultaneous conversion of pollutant elements. Nowadays CO oxidation has important applications in environment protection, such as indoor air cleaning and automotive exhaust treatment. LaCoO3 is one of the most important catalysts for CO oxidation."

Jan 1, 2013

By Jian Li, S. Penttila, W. Zheng

"Materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. Beside high-temperature mechanical properties, SCC and general corrosion resistance of commercially available materials are also major focuses in recent research. Recent reports suggest that certain types of surface modifications are beneficial to SCW corrosion resistance. In this study, the effects of surface modifications are investigated, and possible mechanisms for improved corrosion performance are discussed.IntroductionThe current Canadian pressure-tube supercritical water reactor (SCW) design specifies a core outlet temperature of 625°C under 25 MPa of pressure, with peak cladding temperature as high as 850°C. Challenges in materials selection include high-temperature mechanical properties, corrosion resistance, SCC resistance and radiation damage. Most of the SCW corrosion test results available are below 730°C. Early work by Allen [1] summarized the corrosion resistance of alloy groups including Ni-based super alloys, stainless and ferritic/matensitic (F/M) steels that can potentially be used for SCW reactors. F/M steels can only be used at low temperature sites (e.g. down stream piping). At 500°C and 25 MPa, F/M steels develop a thick but mechanically stable oxide layer. However, the long term stability of the surface oxide layer is largely unknown. Ni-based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of some intermetallic precipitates [2-5], and dissolution of major alloying components could pose significant problems for down stream piping [6]. In addition, concerns of Helium formation due to Ni transmutation prevented this alloy group to be used as fuel cladding. The corrosion resistant austenitic stainless steels (e.g. 316L) are found to be susceptible to localized corrosion such as pitting, intergranular attack and stress corrosion cracking (SCC) [7]."

Jan 1, 2012

By Núbia Suely Silva Santos, Alexandre da Silva Crespo, Frederico Muylaert Margem, Sergio Neves Monteiro, Anderson de Paula Barbosa, Michel Picanço Oliveira

"Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. The fibers extracted from the petiole of the buriti palm tree is a relatively unknown but promising natural fiber for composite reinforcement. In this work, a statistical analysis of the density of buriti petiole fibers using the Weibull methodology was performed. An attempt to correlate the fiber density with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the buriti petiole fiber diameter and corresponding density. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.INTRODUTIONIn the past decade polymer composites reinforced with natural fibers obtained from cellulose-based plants, known as lignocellulosic fibers, have been applied in several engineering sectors, specially the automobile industry as both interior and outside component [1-4].Environmental benefits as well as economical, social, and technical advantages are actually promoting the substitution of these lignocellulosic for the traditional glass fiber in polymer matrix composites [5]. Today several lignocellulosic fiber are being extensively investigated [6-11] and considered for reinforcement of polymer composites. Some relatively unknown lignocellulosic fiber with reinforcement potential, however, still need to be characterized aiming at future application in composites. This is the case of the fibers stripped of from the petiole of the buriti palm tree, which is endemic in the central and northern regions of South America [12,13]. Preliminary works on the possibility of using the buriti petiole fibers as composite reinforcement, has shown favorable results [14,15]."

Jan 1, 2012

By Donghai Li, Cheng Pan, Xuyang Liu, Xuewei Lv, Chenguang Bai

"Fine chromite ore is the common raw material to produce ferrochrome alloy through the submerged electric furnace process. The electric resistivity of fine chromite ore plays an important role in the operation efficiency because it determines the current distribution. The effect of particle size and the contact area of the particles on electric resistivity for several of chromite were investigated at room temperature, and the relationship between the electric resistivity of mixed particles and the volume fraction of lump ore to fine ore was also studied. The results shown that the electric resistivity increases with the increase of particle size, and the electric resistivity of mixture decreases with the increase of volume ratio of fine ore.IntroductionChromium is one of the most important alloying elements in manufacturing of stainless steel that used at high temperature and corrosive environment applications [I, 2]. As the raw materials to be charged into the steel, ferrochromium alloys and charge chromium are produced directly by smelting of chromite ore with the reducing agent in submerged electric arc furnace (SAF). During the process, the oxides of chromium and iron were reduced by carbon and meanwhile the electrical energy were consumed [3,4]. The ideal industrial process is to achieve high recovery level of Cr and Fe with minimal power consumption. In SAF process, the electric resistivity of charge stock has significant effect on the current distribution, which determines the heat distribution, molten bath structure and chemical reactions in the furnace. High resistance of the charge is desired to reduce the current distribution through the charge stock, thus the electrodes may insert into the charge stock with proper depth to form a high temperature arc heat source, and proper smelting can be realized[5]."

Jan 1, 2012

By Samir N. Shoukry, Mourad Y. Riad, Gergis W. William

"Setting of concrete material is defined as the transitional period between states of true fluidity and true rigidity. Initial and final setting times are measured in the laboratory on the mortar sieved from the mix in a controlled environment where temperature and moisture values are constant. On the other hand, field applications are held in outdoor environments where environmental variations have direct impact on setting time values. In this study, initial setting time of class K concrete, usually used for bridge decks and concrete pavements, are investigated highlighting discrepancies between laboratory and field measurements. 72 mixes have been cast in variable environments and collected data from concrete mixes and the ambient conditions are reported. In light of the collected data, the effects of variable setting times on early age cracking of concrete material are studied and means to minimize such cracks are presented.BackgroundSetting of concrete material is defined as the transitional period between states of true fluidity and true rigidity [1]. Continuous hydration of the cement within the matrix transfers the mix from a state of setting to hardening. Initial and final Setting times are measured in a laboratory setting following ASTM C 403 specifications. Initial setting approximates the time at which the cement paste can no longer be plastic under compaction (or can be handled in a proper fashion), while the final setting approximates the time at which hardening occurs. The standard test described in ASTM C 403 is conducted on the mortar sieved from the mix (paste passing from 4.75 mm sieve opening). Initial and final settings are described as the elapsed time after the initial contact of water and cement till the mortar reaches a penetration resistances of 3.5 MPa (500 psi), and 27.6 MPa (4000 psi) respectively."

Jan 1, 2012

By W. Y. Kim, K. H. Song, K. Nakata

"The present study was carried out to evaluate the mechanical properties of friction stir welded Inconel 600/SS 400 lap joints. In this process, friction stir welding (FSW) was performed at a tool rotation speed of 200 rpm and welding speed of 100 mm1min, and argon gas was utilized to prevent surface oxidation during the welding. Application of FSW notably decreases the grain size of Inconel 600 alloy from 20 µm in the base material to 8 ~ in the stir zone. However, the grain size of SS 400 in the weld zone was slightly coarsened, when compared to the base material. Also, the hooking in the advancing side and the intermetal1ic compounds (M7C3) in the weld interface between Incone1 600 and SS 400 were well formed. These intermetallic compounds and hooking were effective to increase in mechanical properties such as tensile and peel strengths.IntroductionFriction stir welding (FSW), applicable welding process at solid state, has several advantages in defect suppression such as blow hole, segregation and cracking which mainly occurs in fusion welding [1, 2]. Notable grain refinement in the stir zone due to FSW can expect the outstanding increase in mechanical properties of the welds. In constructing the chemical and power plants, Ni base superal10ys have been used in many parts, moreover, fusion welding as construct method, such as gas tungsten arc welding, electron beam welding and laser welding, has been mainly used [3-5]. However, fusion welding has a limit in an increase in chemical and mechanical properties in the welds. Lately, Ni base superalloys to which FSW applied have been reported with notable enhancement in mechanical properties, which resulted from refined grains in the welds [6-10]. These researches showed the possibility in applying the FSW, directly."

Jan 1, 2012

By Nedam Abed

A fundamental study of the sonochemical leaching of chalcopyrite in ferric ion media has been performed to understand and quantify the effects of sonication and other parameters on leaching reactions. The study covers sulfate and chloride media. The main leaching reaction: CuFeS2(s) + 4Fe3+(aq) Cu2+(aq) + 5Fe2+(aq) + 2S(s) (1) was found to be dependent on temperature and initial particle size, but less dependent on ferric ion concentration. Leaching kinetics were not affected by ferrous ion concentration or the amount of chalcopyrite added. Leaching was performed under a variety of sonication and leaching conditions. Reaction stoichiometry was confirmed through detailed wet chemistry analysis and mass balance calculations. The use of ultrasound activation showed a clear improvement in leaching kinetics and amount of copper extracted, sonication having a catalytic-like effect on the leaching reaction. Compared to experiments without sonication, reaction rates were 2-3 times faster at the same temperature, and could be faster by a factor of 20 for the same initial particle size. Regardless of initial particle size, the amount of copper extracted was comparable under sonication, and could be twice that under chemical leaching, implying the avoidance of fine particle grinding. Sonochemical leaching was found to be only temperature dependent, where the best copper extraction was at 75C. Leaching was further enhanced by the use of a grinding aid. The leaching behavior of chalcopyrite particles remained similar with and without ultrasound activation, implying that the known passivation mechanism in the oxidative leaching was not eradicated. Sonication resulted in coarse particle breakage (ultrasonic milling). Sonication did not contribute to particle passivation, as affirmed from different leaching procedures and sonication in aqueous and organic media. Parabolic leaching kinetics were confirmed for leaching experiments.

Jan 1, 2003

By Thomas Brynjulfsen, Merete Tangstad

"Manganese ore fines, generated during mining and transportation, can not be added to the submerged arc furnace directly as they will prevent even gas flow through the burden. Low gas permeability in the burden will lower the degree of pre-reduction of ore and subsequently increase the carbon and energy consumption of the process. In order to utilize manganese ore fines in the furnace they are agglomerated into sinter, pellet or briquettes. The agglomeration process will however change the reduction properties of the ore. In this work the melting and reduction properties of sinter has been investigated.The melting temperature and melting mechanisms has been studied. The mineralogy of the raw ores and agglomerated has been found using XRD, and the composition established using EPMA(WDS). The effect of adding fluxes such as dolomite and quartz has also been investigated.IntroductionManganese metal is produced in a submerged electric arc furnace or in blast furnaces. The reduction of manganese oxide in blast furnace has in the recent years become more unusual due to the high consumption of reducing carbon material[5]. Manganese metal for alloying in steel usually contains silicon and iron, and are therefore called ferro manganese and silicomanganese.During mining, transportation and handling the manganese ore is broken up into different size fractions. The larger lump are used directly in the electric arc furnace, but the finer materials can not be added without treatment. The fine ore can disrupt the flow of CO and CO2 gas through the burden, subsequently reducing the degree of pre-reduction. The fine fractions must therefore be agglomerated into larger lumps, in order to promote gas flow. This can be achieved through a number of different processes. The agglomerate used in this work has been sintered, which means that is has been partly molten and reduced, in order to create bigger lumps."

Jan 1, 2012

By Fu-Shen Zhang, Mengjun Chen, Jianxin Zhu

"In the present study, different types of cathode ray tube (CRT) glasses were examined by sequential extraction combined with TCLP to provide possible explanations for how Pb and Ba leach out from the waste CRT glasses and to give possible reasons for why they leach out. Sequential extraction results showed that Pb and Ba in the CRT glasses dominanfly presented as the residual fraction. The exchangeable fractions of Pb and Ba were extremely low, less than 0.01 % of the total content, but they were higher than those required by the regulation limits, 5 and 100 mg/L for Pb and Ba, respectively. TCLP tests of the original CRT glasses and CRT glasses residues after each step of sequential extraction demonstrated that the extremely high leaching toxicity of CRT glasses mainly caused by its exchangeable and carbonate fractions of Pb and Ba.IntroductionIn recent years, the amount of cathode ray tube (CRT) contained monitors or TV sets in the market were sharply reduced, since they were substituted by novel and better electronic and electric equipments such as LCD and PDP, leaving huge amount of end-of-life CRTs. 50-85% of the total weight of this kind of computer monitor or a TV set is glass[1,2], which was classified to three categories according to their chemical compositions: black & white glass (BW), color panel glass (CP) and color funnel glass (CF)[3]. In order to provide shielding from X-rays generated during the picture projection process, lead, barium and strontium oxides were used in the glass. In general, a color CRT contains 1.6-3.2 kg of lead . Therefore, these glasses have attracted wide and tense attention due to the potential risk to the environment and human health."

Jan 1, 2011

By K. Verbeken, E. Wettinck, M. Verhaege

Iron (III) can easily and selectively be removed from acidic sulphate solutions with organo-phosphoric acids like Di-2-Ethyl-Hexyl-Phosphoric Acid [D2EHPA]. Stripping of the iron (III) loaded organic, however, is difficult unless highly concentrated inorganic acid solutions are used. In this paper results are shown for the enhanced stripping of iron from loaded D2EHPA by electro-reduction. The loaded solvent is contacted with a 2 M H2SO4 solution, which is continuously recycled in an electrochemical reactor where iron (III) is reduced to iron(II). As iron (II) is not extracted by D2EHPA, the equilibrium for iron (III)- D2EHPA is shifted towards the aqueous iron (Il)-sulphuric acid solution. The electro-reduction unit is a vessel with separated catholyte and anolyte chambers. The catholyte is the actual stripping solution where iron (III) is reduced to iron (II) on a stainless steel electrode. The anolyte is a 2 M H2SO4 solution where oxygen is evolved on a lead alloy electrode. A sintered glass plug separates the compartments. With this unit, enhanced stripping of iron from the solvent is possible under mild acid conditions [2 M H2SO4], and a concentrated ferrous sulphate solution can be obtained. The results shown have mainly been obtained by studying the parameters affecting the electro-reductive stripping of a D2EHPA loaded organic phase in a batch reactor. From an iron (IH)-saturated 20 vol. % D2EHPA solvent containing ~ 12.5 g/1 Fe (III) over 90% of the iron can be stripped in one stage with a 2 M H2SO4 solution at 50°C. It is shown that in this way it should be possible to obtain a concentrated ferrous sulphate solution which can be processed downstream to recover a pure iron product.

Jan 1, 2000

By Carlos Eduardo Gomes de Souza, Luis G. S. Sobral, Paulo A. Medeiros da Silva, Selma G. F. Leite, Renata de B. Lima

"The use of mixed cultures of acidophilus microorganisms that act in different temperature ranges, aims at speeding up the digestion of chalcopyrite, highly refractory sulphide mineral, the major mineral in the flotation concentrate of Caraíba Mining Co., with an attractive processing cost. The concentrate under consideration contains mainly chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents of, approximately, 70 and 30%, respectively. It was observed in this study, the performance of consortium of mesophiles, moderate and extreme thermophile microorganisms, in the oxidation of the aforementioned sulphides minerals, evaluating operational parameters such as pH of the leaching solution, the reaction temperature and redox potential, with consequent extraction of 80% of the concentrate copper content within 60 days of bioleaching. Such high copper extraction was achieved in column bioleaching tests.INTRODUCTIONThe solubilization of metals by the application of microorganisms from the mineral ores and the subsequent recovery of metals from solution are referred to as bioleaching (Rohwerder, T et al, 2003). This is an economical method for the recovery of metals from minerals; especially lowgrade ores, overburden, and waste from current mining operations which requires moderate capital investment with operating cost (Watling, 2006).Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes such as concentration and smelting. Those physicochemical metal extraction processes generate sulphur dioxide, a toxic emission that is increasingly the target of regulatory legislation (Stott et al., 2000; Olson et al., 2003). Bioleaching of chalcopyrite is the key industry target. The main problem hindering commercial application of chalcopyrite bioleaching is the slow dissolution rate (Fu et al, 2008).Dissolution of acid-soluble sulphide minerals such as sphalerite, and to a lesser extent chalcopyrite, occurs by a combination of ferric iron and proton attack via the polysulphide pathway (Rohwerder et al., 2003)."

Jan 1, 2008

By Dinabandhu Ghosh

The stability diagram of the ternary system Ti-C-O is drawn in the present work for four temperatures, 1473 K, 1573 K, 1673 K and 1873 K, showing the stability fields of TiC, Ti, TiO, Ti2O3 and TiO2. An analysis of the system reveals that it is not possible to produce Ti in a carbon-saturated system; instead, the stable product is TiC. However, Ti can be an equilibrium product in a carbon-unsaturated system at prohibitively low values of pCO and pCO2; for example, at 1873 K, these limiting values are: pCO = 10-6.76 atm and pCO2 = 10-13.36 atm, which, when exceeded, produce TiC and TiO respectively. The magnesiothermic reduction is examined through the stability diagram (log pO2 vs. 1/T) of the system Ti-Mg-O, drawn for a number of pMg values, presenting the pairwise stability fields such as Mg(l) + Ti(s), Mg(v) + Ti(s), MgO(s) + Ti(s), etc. The diagram shows that magnesium reduction of TiO to Ti is possible only at T < 1641 K with pMg = 1 atm and only at T < 1569 K with pMg = 0.5 atm. An experimental scheme for Mg vapor reduction of TiO2 is proposed in which an argon stream is passed over a Mg(liquid) evaporator at temperature T1 (say, 1234 K); the resulting Ar-Mg mixture at 1 atm is subsequently flown over a bed of TiO2 at temperature T2. A thermodynamic analysis establishes that complete reduction to Ti is possible and that the best results are obtained when T1 = T2.

Jan 1, 2006

By Tracy Morris, Weldon Read, Luis Navarro

"During the leaching of anodic slimes, tellurium dissolves into the leach liquor together with copper and must be removed before the solution is sent to liberator cells for copper recovery. Prior to the installation of autoclaves, tellurium was precipitated using raw slimes that caused a recirculation of tellurium in the leaching circuit. After autoclaves were installed the old leach tanks were converted into tellurium reactors utilizing copper chips, steam and agitation to form a copper telluride precipitate. Tellurium levels of less than 10 rng/L are achieved in a timely manner.IntroductionThe electrolytic refining of copper consists of an electrolytic cell provided with an anode of impure copper, a cathode of substantially pure copper (starter sheet) and an electrolyte made of copper sulfate and sulfuric acid [1]. When a direct electrical current is passed between the anode and cathode inside the cell, the impure copper anode dissolves in the electrolyte and pure copper is plated onto the cathode. During this operation, many of the impurities are deposited on the bottom of the cell as an anodic slime residue composed of insoluble chemical compounds. Slimes are a major source of rare and precious metals in the copper industry [2-5],In the Amarillo Copper Refinery (ACR), the anodic copper slimes are sent to the Precious Metals department in order to extract and then refine the gold, silver, platinum and palladium from them. The remaining impurities, in the form of a soda slag or copper slag are sent to the Hayden smelter for further processing. Copper telluride is sent to the Selenium/Tellurium department inside the plant for selenium and tellurium recovery. During the leaching process of the anodic slimes, copper, tellurium, and other metal species in the slimes are dissolved into leach liquor that cannot be returned to the tankhouse unless the tellurium concentration is below 10 mg/L."

Jan 1, 2012

By José Sancho, Julia Ayala, Purificación García, Begoña Fernández

"A study is carried out to see the adequacy of using flying ashes coming out from a Power Station to eliminate the copper present in waste cyanide waters that are generated in gold mines.Tests were carried out to see how effective the use of ashes taken from two Power Stations could become. Later, the tests are made using ashes coming from Narcea Power Station as this station is near the mine under study.The work is centred on looking for an economically adequate solution to close the waste decanting ponds of the mine. After several tests, a solution is reached through filtration in static layers.IntroductionThe use of coal to adsorb some water-soluble substances has been widely studied [1,2,3,4,] both in the treatment of drinking waters and in determined stages of selective detachment of cyanide gold complexes in cyanide lixiviation processes [5]. Flying ashes sent to the atmosphere by Power Stations as a sub-product of the combustion of this combustible are generally made of more of a 70 % of a vitreous aluminosilicated material and of an active residual material which may be changeable making them potentially useable as adsorbents. Nevertheless, the properties of each kind of ashes depend on the characteristics of the Power Station, of the combustibles being used, of the combustion system, etc.The aim of this work is to demonstrate the adequacy of flying ashes to eliminate the copper present in cyanide waters coming from gold mines either by adsorption or precipitation of the metal. For this study, tests are carried out with Asturian ashes which have a low quantity of lime. The results obtained in the tests demonstrate the effectivity of the method used. To be absolutely concrete, the work is carried out to establish the use of these ashes in the closing of Asturian installations of cyanide lixiviation"

Jan 1, 2008