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By Sadegh Safarzadeh, Anne-Marie Suriano, Stanley Howard

The electrodeposition of metal ions from aqueous electrolyte solutions has been a well-known process for the last half century. With numerous industrial applications such as electroplating, electrowinning and electrorefining, the kinetics of electrochemical reactions involved in the process has been extensively researched. Arrhenius-type rate equations, the Butler-Volmer equation, and the empirical Tafel equation are among the most important models to explain the rate of electrochemical reactions. The study of the kinetics of metal deposition is critical to understanding the underlying mechanisms through which a certain morphology of metal deposit is formed on the cathode. The purpose of this paper is to elucidate the influence of experimental parameters such as pH and additives on the rate and the reaction mechanism determining the rate limiting step of the electrodeposition reactions.

Jan 1, 2015

By Youn-Bae Kang, Jong-Jin Pak, Min-Kyu Paek

The critical evaluation and thermodynamic optimization of Mn-Si-C and its sub-binary systems have been carried out over the whole composition range from room temperature to above the liquidus temperature. The solution properties of the liquid systems have not been clearly described because the liquid solution exhibits a high degree of short-range-ordering. In order to predict the thermodynamics of the liquid solution, the liquid phases were optimized by the modified quasichemical model. The model parameters of the solid phases were also optimized by the compound energy formalism to best reproduce the phase diagram and important thermodynamic properties in Mn-Si-C system. Using the model parameters, various thermodynamic calculations were carried out. The present database will be a part of larger thermodynamic database for the ferromanganese alloy database.

Jan 1, 2014

By Roderick Guthrie

Gas injection into liquid steel baths is widely practiced, ever since the early days of Bessemer’s pneumatic steelmaking process. What has not been fully appreciated is the critical role of bubble sizes for delivering higher quality commercial steels than is presently possible. This was first proposed by Prof P. Hayes and his research group. Using a full-scale water model of a typical 4-strand Ladle-Tundish-Mold system, we demonstrate the potential advantages of modifying a typical ladle shroud, to generate microbubbles within the water flowing into the tundish. This is possible by taking advantage of high shear rates and turbulence kinetic energy available in that region. These microbubbles enhanced the removal of “micro-inclusions” (hollow glass microspheres) in the 5–50 micron size range, to the upper surface of the tundish. There, they were absorbed into an overlaying “slag” phase. Accompanying CFD studies confirmed that no microbubbles in the size range generated (500–900 μm), pass through the submerged entry nozzles into the moulds.

By Lori Bassman, Cassandra George, Cullen McMahon, Md. Zakaria Quadir, Michael Ferry

"Complete and accurate analysis of subgrain microstructural features must include three-dimensional information. Three-dimensional electron backscatter diffraction (EBSD) data can be used to characterize these features; however their boundaries first must be determined. This cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast Multiscale Clustering (FMC) is an established image processing technique that we have combined with quaternion representation of orientation to segment this kind of data. Segmentation algorithms often have issues handling images with both distinct and subtle boundaries. Our implementation of FMC addresses this by using a novel distance function and statistical analysis to take into account the variance in orientation of each feature. Although FMC was originally a twodimensional image processing algorithm it can be generalized to analyze threedimensional data sets. As an example, a segmentation of microbands in cold-rolled aluminum is presented.IntroductionThree-dimensional electron backscatter diffraction (3D-EBSD) is a method for mapping the local crystallographic orientations of points in a volume. The technique uses a dual beam platform consisting of a focused ion beam (FIB) and SEM with EBSD, where FIB is used for serial sectioning and EBSD for orientation mapping of 2D slices. These 2D slices may then be stacked to create a 3D volumetric data set.Typical uses of such a data set include characterizing the geometries and crystallographic orientations of surfaces between structures in 3D [1-5]. This involves identifying boundaries accurately, either in 2D slices with subsequent 3D reconstruction (as illustrated in Figure 1) or in the 3D data set. All such data sets present the challenges of i) aligning data slices to correct for instrument drift, ii) identifying relevant boundaries, and iii) implementing appropriate smoothing or interpolation algorithms. The focus of this paper is boundary identification."

Jan 1, 2011

By Hojat Naderi

In this research assisted leaching of chalcopyrite using sodium peroxodisulfate was studied. Electrochemical techniques such as Tafel analysis and electrochemical impedance spectroscopy (EIS) were used to investigate the surface reactions of a chalcopyrite electrode in the presence and absence of Na2S2O8. According to the results, addition of sodium peroxodisulfate increases the current exchange of the corrosion process and prevents the formation of a passive layer on the surface of the electrode. EIS tests show the trans-passive dissolution of the passive layer on the chalcopyrite electrode in presence of Na2S2O8. Equivalent electrochemical circuits were modeled for Na2S2O8-free and -containing solutions and the model parameters were compared to determine the effect of S2O8 2− on chalcopyrite dissolution. Copper dissolution from pure chalcopyrite mineral and chalcopyrite concentrate was carried out using 15 g/L sulfuric acid solution with and without Na2S2O8. Simultaneous presence of 10 g/L ferric ion and 40 g/L peroxodisulfate salt results in about 40 and 18% of Cu extraction from chalcopyrite concentrate and pure chalcopyrite mineral, after 96 h, respectively.

By G. C. Amstutz

The topic of the industrial applications of mineralogy is a vast field which can be adequately covered only in a large book or by a two or three semester course. This paper recalls experiences of the writer in this field, a task requested by the Process Mineralogy Committee. Therefore, this paper is largely an account of the industrial mineralogy problems I was involved with, since my student years, Although I will treat each application only briefly, it is hoped that they will illustrate to the students in the field how varied are the applications of mineralogical methods. In this respect, I want to emphasize that it is important for mineralogy teachers to point out the usefulness of mineralogical methods much more often in their courses. Not only does that help prepare young individuals for industrial careers, but also it arouses their feeling of consciousness of public responsibility which is an important attribute for the world's scientists. When professors utilize the varied applications in their teaching of mineralogical methods students then understand better the significance of learning those methods and appreciate the many years of necessary university preparation. The first time I was involved in an application of mineralogical methods was about 1944 as a student of Professor Paul Niggli. He was asked to study the problems of ice crystallization on wings of airplanes. The ice formed at high altitudes and during the winter. This was not outside his realm of expertise because he was the main initiator of the Snow Research Institute on the Weissfluhjoch in Switzerland. I believe that the work of this Institute was an important factor in stimulating much of the snow research subsequently carried out at the United States Army Snow Research Center, which was located at that time in Willmette near Chicago. Dr. Bader, one of Paul Niggli's former students, was the Director of Research at Wilmette at that time and for quite a number of years thereafter. A mineralogist-crystallographer can make important contributions to a better understanding of the problems of snow and ice formation, avalanche hazards, and the prevention of hail. The habits of snow crystals are essentially a function of the temperature and the humidity,

Jan 1, 1982

By Nils Lippmann, Ulrich Weber, Siegfried Schmauder, Jr. Mishnaevsky

"A computational approach to the optimization of fracture resistance of multiphase materials (here - high speed steels) by varying their microstructure is presented. The main points of the optimization of steels are as follows: (1) development and verification of the model: numerical simulation of crack initiation and growth in real microstructures of steels, (2) computational experiment: simulation of crack growth in different idealized quasi-real microstructures and (3) the comparison of fracture resistances of different microstructures and the development of recommendations to the improvement of the fracture toughness of steels. Numerical simulations of crack growth in real microstructures of steels and different idealized carbide distributions are carried out. On the basis of the simulations, recommendations for the improvement of high speed steel microstructures are given. It is shown that the fracture resistance of the steels is much higher for the fine than for the coarse version of the same type of microstructures.IntroductionThe purpose of this work is to develop an approach to the optimal design of multiphase materials on the basis of numerical simulation of their behaviour under mechanical loading. We suggest here the following strategy:1. Collecting input data for the simulations: taking a micrograph of a microstructure, and determining mechanical properties and failure conditions of the material constituents [1, 2],2. Simulation techniques and assumptions are tested for a real microstructure of the material: crack growth in a real microstructure is simulated and then compared with the experimental data,3. Computational experiments: different microstructures of materials are tested in the numerical model under the same loading conditions. The calculated service properties of the different microstructures are compared, and recommendations are developed. As differentiated from the ""real"" experimental techniques, the computational experiment is much cheaper and not labor- and time-consuming."

Jan 1, 2001

By Malti Goel

"The cost-effective capture of carbon dioxide (CO2) from the point sources for its reduction the atmosphere offers many challenges in materials science. Novel CO2 capturing approaches using chemical, physical and biological methods are in the research stage and are aimed to minimize the cost. Appropriate materials development , which can withstand required temperature or pressure as the case may be for CO2 emanating from coal gas or industrial waste gases form the minimum condition. Other requirements are reclyclability of material and cost of separation. Nano-material composites can be more effective in selective capture of CO2 and can offer solutions for large-scale separation process. Nano-porous material catalysis can enhance the reaction rate of CO2 with other chemicals and thus help in capture of CO2 and convert it into value added products. This paper reviews recent industrial scale developments. In the Indian context, R&D priority areas in CO2 capture process development with a focus on energy industry are presented.IntroductionScience of Climate Change is growing at an enormous pace. With the ultimate goal of stabilization of greenhouse gases in the atmosphere, new scientific approaches are being researched worldwide. A shift in policies from low carbon and no carbon energy sources to fossil fuel sources with capture of carbon and its permanent storage is taking place. The process of carbon capture is both energy and materials intensive and the cost of power generation may increase up to 40% when carbon capture and storage (CCS) technology is implemented. Development of cost effective R&D technology therefore remains the greatest challenge before the scientific community."

Jan 1, 2009

By Ximena Diaz

Mercury is one of the most undesirable contaminants in gold bearing ores. During cyanidation mercury cyanide compounds accompany gold in all the extraction and recovery processes. Of course mercury in the carbon eluates creates environmental problems in subsequent refining steps. One possible process alternative for the separation of gold from mercury in such concentrated alkaline cyanide solutions is the selective solvent extraction of gold by undiluted Dibutyl Butyl Phosphonate (DBBP). In order to describe the behavior of mercury during extraction by DBBP, the results from a preliminary research program are presented. In this study, temperature and cyanide concentration have been found to be the most significant variables which influence the separation of gold from mercury by solvent extraction using DBBP. It was found, using plant eluate from a carbon strip, that excellent separation of gold from mercury can be obtained at 60' C with 98% gold recovery and complete mercury rejection in a single stage of extraction. The influence of pH is also discussed in terms of the extraction chemistry. These results complement previous research which described the DBBP solvation extraction of an aurocyanide ion pair. In addition, these results extend our understanding of the alkyl phosphorous ester extraction systems by illustrating that neutral ionic species such as Hg(cN)02sq, can be extracted at low cyanide concentrations, a phenomenon which had not been observed previously for other cyanoanions.

Jan 1, 1993

By Saskia Duyvesteyn

Small ion-exchange resin particles provide faster mass transport than conventional-sized beads. Unfortunately, high pressures are needed to pump solutions through columns containing small resin particles. It is preferable to disperse fine resins in the solution being treated. Screens have been used to separate the resin from the solution, but screens do not retain fines created by attrition of the resin particles. We have developed a separation process based on flotation, which relies on the surface characteristics of the resin, instead of size. The resin is conditioned with a surfactant before dispersing it in the solution to be treated; this increases the hydrophobicity of the resin sufficiently for froth flotation, without introducing surfactant directly into the solution. The surfactant adsorbed on the resin surface does not appear to impair the kinetics of metal ion removal. A flowsheet for an effluent treatment process is proposed; other applications are clearly possible.

Jan 1, 1998

By Kazusuke Sato, Takahiro Uno, Koji Hoshino

"A novel Ni coating technique of Ni(OH)2 powders was developed to improve the positive-electrode performance· of the Ni-MH batteries. It was found out that Ni(OH)2 powder was reduced by N2H4 without any catalysts in an alkaline - solution at high temperatures. In result of observation of pH and potential changes in the solution during the reaction, it was found that the reduced species was HNio2- ion dissociated from Ni(OH)2 in the alkaline solution. The molar fraction of reduced Ni of the Ni(OH)2 was increased in proportion to the amount of added N2H4. At the small Ni fraction, a porous Ni layer was formed on the surface of Ni(OH)2 powder. Open cell tests were carried out with the paste type electrodes made of either the Ni coated Ni(OH)2 powder or non-coat powder, and cell performances were compared. In result, it was found that the Ni coating technique is effective on improvement in the utilization of Ni(OH); as a positive-electrode active material under high current densities.IntroductionNi-MH rechargeable battery is generally used for the power source of portable machines and electric vehicles because of its good performance at high energy density and. long term cyclical life as well as cleanness and good safety. Cell component materials have been improved respectively, and as concerns ·the positive-electrode reducing 'the internal resistance is a principal problem to improve the discharging performance at higher current densities.In recent years, improved Ni(OH)2 powders coated with conductive materials as NI. or CoOOH have been developed for the· positive-electrode active materials in order to· reduce the internal resistance of the electrode1)· 2) The Ni coated Ni(OH)2, however, is costly because it is fabricated by .the -non-electrode plate technique which needs a expensive precious ·metal catalyst as PdC12We found that Ni(OH)2 powder was reduced by N2H4 without any cryatalysts in an alkaline solution at high temperatures. After the treatment, Ni(OH)2 powder become gray color like Ni powder from light-green color; and. turned into a magnetic. In this study, the mechanism of the -reducing reaction was investigated to apply the reactions .to a novel Ni coating technique of Ni(OH)2 powders, · and the performance of the Ni coated Ni(OH)2 powder obtained by the reducing process was evaluated as an -positive-electrode active material of Ni-MH batteries."

Jan 1, 2000

Halide media are considered as suitable alternatives to cyanide for extracting gold and have received much attention lately. The extraction of gold by iodide-iodine mixture has been patented and briefly studied without much attention given to the fundamental aspects of this process. This paper reports recent studies on the kinetics of gold extraction in iodide media, using hypochlorite, iodine and hydrogen peroxide oxidants. The kinetics of dissolution was found to be dependent on the solution pH, reagent concentration and most importantly the iodide- oxidant molar ratio. Without proper control, the gold surface can be passivated due to the formation of solid products. Thermodynamic modelling was carried out to determine the equilibria governing the dissolution process. The formation of AuI solid was also identified as a possible product during the dissolution.

Jan 1, 1992

By B. Wasmund, K. Adham, K. O'Keefe, C. Lee

"Metal chlorides (e.g. iron and nickel) can be pyrohydrolysed at elevated temperatures to yield an HCl rich off-gas and a metal oxide product. Typically, the high energy requirement for pyrohydrolysis is provided by the combustion of a hydrocarbon fuel with air. Here, it is demonstrated that the use of oxygen-enriched combustion can result in lower fuel requirements and higher HCl concentrations. In addition, the oxygen enrichment can result in a smaller volume of off-gas and thus, smaller and less expensive process equipment. This new concept can be applied to both the spray roaster (SR) and the fluidized bed reactor (FBR). Similar to the aircombustion case, the oxygen-enriched process can use a direct contact venturi scrubber, to recover energy from the roaster off gas, but at a higher efficiency. The new process also uses an absorption tower for capturing HCl from the roaster off-gas, but generates a stronger HCl solution than is possible with pyrohydrolysis in air.BackgroundIn recent years, the metallurgical industry has become increasingly involved with developing methods for extracting metals, upgrading products or cleaning metallic products by using hydrochloric acid. These applications of chloride metallurgy often result in metal chloride solutions, which should be processed to regenerate HCl for reuse, and to recover the metal value as a product or by-product oxide [2, 3, 4].The pyrohydrolysis of metal chloride solutions has been done in two types of air roasters: spray and fluidized bed. The existing roasters burn a hydrocarbon fuel in air, to provide the required energy for evaporating the feed solution and to provide an elevated temperature for the chloride pyrohydrolysis to occur, according to the following reactions:"

Jan 1, 2011

By Thierry De Nys

A direct leaching process of sulphidic zinc-based concentrates in aqueous sulphuric acid solutions has been developed by the V.M. R & D Department. By a very accurate control of the oxidation potential of the leach solution, this process enables a separate recovery of the zinc, copper, silver, lead and sulphur of the concentrate and makes it extremely attractive for treating more complex ores. The iron, solubilized during leaching, is eliminated out of the zinc solution by means of the V.M. goethite process. Alternative flow sheets for a conventional zinc electrolysis plant are presented.

Jan 1, 1990

By Shenghui Guo, Ying Lei, Wei Li, Jinhui Peng, Libo Zhang, Yu Li

"In this work, the Panzhihua low grade ilmenite and graphite were milled for 1, 2, 4 and 8 h firstly, then the temperature rising behavior of milled sample in microwave field were studied. The average heating rate of samples milled for 1, 2, 4, 8 h were 1.86, 4.08, 2.82, and 2.32 K/s; Before optimize the microwave reduction process, several experiments were conducted in order to confirm the parameters range. After milled for 4 or 8 h and reduced above 930 oC, the Fe metallization are higher than 90%; Then the optimization was investigated by using response surface methodology (RSM), the significance of predict model and each terms were analyzed, and the optimization parameters were given as: milling time is 4 h; reduction temperature is 1001 or 1070oC; the holding time is 37.5 or 26.9 min. Under these conditions, the Fe metallization given by predict model is 91 or 92 %.IntroductionThere is about 9.66 billion tons of Vanadic Titan-magnetite deposits in Panzhihua, China. In this reserve, there is about 8.73×108 t of TiO2, accounting for 90.54% of the Chinese reserves, and 35.17% of the international reserves and ranking first in the world. [1] Titanium mineral deposits are classified into Rock type and Placer type. Rock type is the igneous mineral, which have high content of FeO (Relative to Fe2O3) and gangue. The Panzhihua ilmenite is a typical rock type ilmenite ore. The higher contents of MgO, CaO, SiO2 and the complex mineralogy are making its direct reduction progressively more difficult."

Jan 1, 2011

By Gunnar Eriksson

Computer simulation has become an everyday practice in thennodynamic and materials research. Advanced thennochemical algorithms take into account heat transfer effects and salient reaction kinetics when applied for process models. In particular, the combination of mass transfer or overall reaction rates with multi-component Gibbs energy minimisation provides an effective tool for simulation of industrial thennochemical processes and processing of materials. In this work the combination of rate factors with the Gibbs energy technique was studied by using the novel program ChemSheet, which operates through Microsoft's Excel® spreadsheets. Such processes as, for example, CVD of pure silicon production, titania pigment manufacturing, vapour pressure of Mercury in amalgams (in Hg-Iamp manufacturing) and melting behaviour of low-temperature alloys have been modelled. Provided that the thennochemical data is available simulations can be performed with any thennodynamic system. The calculation can be performed as an affinity study without a particular reactor model or with a specific reactor scheme.

Jan 1, 2001

By Helena Byrdziak

KGHM Polska Miedz SA, in existence since nineteen seventies, operates three underground mines and three smelters with total production of over 400 000 mtpy of electrolytic copper. Its impact on the environment, very serious in the past, has been gradually reduced. While in general emissions into the air and water have been brought under control, attention recently has shifted to the disposal of wastes and residues. The main streams of wastes are flotation tailings, slags and dust captured from the dedusting systems. Much effort has already been expended and is still being spent to utilize this waste for by-products production or to dispose of it within the process by recycling. The most effective measures taken up thus far, as well as present activities directed at tailings disposal, are presented.

Jan 1, 1997

By Kuiting Wang, Jinshan Liu, Ninglei Sun, Aiguo Dong, Yeda Lu

"Eliminating the environmental threat caused by waste effluent containing magnesium sulfate derived from the process of nickel laterite sulfuric acid leaching and subsequent nickel precipitation is always a focus in the metallurgy field. A new flowsheet whose procedures include vaporization, crystallization, two stages precipitation of magnesium, causticizing treatment of filtrate and ammonia recycle was investigated. Both the details of the flowsheet and its application are described in this article. It is confirmed to be an effective and economical method to prevent the pollution by the waste effluent, simultaneity, a series of magnesium products recovered during the process own good economic returns.IntroductionSulfuric acid leaching is the conventional procedure of extraction valuable metals from ores in hydrometallurgy field. During the process of nickel laterite sulfuric acid leaching, several metals, including Ni, Co, Al Mn, Fe, Mg etc., migrate into the leachate in the form of soluble metal sulfate. After subsequent procedure of purification, precipitation of Ni and Co and neutralization, an enormous stream of waste effluent which contains a concentration of approx. 15-40g/L Mg is exhausted. Such solution containing magnesium sulfate is toxic, which causes diarrhea for both human and animals. On the other hand, large amount of sulfate acid was consumed during the process of leaching by the compound of Mg, which increases cost of a hydro nickel plant.In arid areas, the waste effluent mentioned above is treated via evaporate pond owning large acreage, which needs not only the appropriate meteorologic condition, but occupies much land. In coastal areas, it is directly discharged to the sea, which probably deteriorates ecological system of offshore strip. The most widespread method to treat with the waste effluent is neutralization by lime cream, the residues of which containing magnesium hydroxide and gypsum are transported to residues pool. Neutralization is a simple process, but it never recycles the Mg and sulfate anion into new application, meanwhile, the residues are potential threat to the environment."

Jan 1, 2012

By Ivo André

Sorption of copper ions from aqueous solutions by dried biomass of the aquatic plant Potamogeton luscens was studied at laboratory scale. The aquatic plant was collected in water resources in Brazil, washed, dried at 60°C and ground in a bladed mixer. Sorption experiments were conducted in agitated flasks and in a packed bed column. Maximum copper removal was obtained between pH 5.0 and 6.6 when copper was present in the ionic form Cu'. Sorption followed the Langmuir isotherm with saturation attained at 35 mg/g. Free energy of sorption was found, to be of the order of -25 kJ/mol. Sorption kinetics data were better described by a second order reaction and rate constants were calculated in 0.030 1/(min.mg) for - 4.0 mm particles and 0.081 1/(min.mg) for - 0.59 mm particles. Removal of metal ions in a packed bed column showed that Potamogeton luscens biomass can be used in several sorption/dessorption cycles. After sorbent saturation, copper ions can be recovered from the loaded biomass by elution-with H2SO4, solution. Main mechanism responsible for heavy metal uptake was found to be ion exchange. Results are discussed in terms of the surface properties of the biomaterial, solution chemistry of copper ions and thermodynamics parameters.

Jan 1, 1995

By C. A. Pickles

Microwave processing is a relatively new technology that has been successfully applied in a number of industries. However, in the field of metal extraction, there is a paucity of success, despite considerable hype in the early years. Increased reaction rates, lowered reaction temperatures and higher energy efficiencies were some of the advantages claimed. Even with over almost two decades of research and some pilot plant studies, microwave metal extraction remains essentially a laboratory technique. In this paper, the research performed over the last few decades will be reviewed and some reasons for the lack of success in developing microwave metal extraction processes will be discussed. Based on the knowledge gained from these experiences, a more informed view of microwave heating can lead to the realization that there is still some untapped potential for this heating technique in metal extraction processes.