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By M. Misra

The volume of low-level contaminated soil at the. Department of Energy's Nuclear Weapon Sites are in the order of several million tons. Most of the contaminants are uranium, plutonium, other heavy metals and organic compounds. Selected Physical separation processes have shown demonstrated potential in COD Centratingthe radio nuclides in a small fraction of the soil. Depending upon the size, nature of bonding and distributions of radio nuclides, more than 90 percent of the radio nuclide activity can be concentrated in a small volume of fraction of the soil. The physico-chemical separation processes such as flotation in a mechanical and microbubble tall column cell have shown, promising applications in cleaning up the high volume contaminated soil.

Jan 1, 1995

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

By C. D. Seybert, J. W. Evans

"The elimination of convection is essential in experimental investigations of diffusive transport (of heat and matter) during solidification. This paper describes an investigation of an approach whereby a magnetic field gradient is applied to a electrically non-conducting diamagnetic liquid. A magnetic body force then arises which is dependent on the volume susceptibility of the liquid and thereby on the density. With the field gradient aligned vertically and of correct magnitude, the variation of gravitational body forces due to density variations (arising from temperature variations, for example) can be counterbalanced by a variation in magnetic body force.Preparatory to a study of convection control in diamagnetic liquids, PN measurements have been made of the convection occurring during the solidification of water. A peculiar flow arises because of the density maximum at 4°C. Modeling of the flow the steady-state solidification of water in an extremely high field magnet at the NHMFL indicates that flow can be significantly reduced, but it is suggested that, due to field gradient variations within the cell, flow cannot be completely halted. INTRODUCTIONNatural convection is inherently a part of terrestrial solidification. Density-based convection during solidification, due to gradients of temperature and/or concentration, has a significant effect on a material's properties. The design of products with specific material characteristics has required the development of many processes to control convection (such as in the growth of semiconductor crystals, and electromagnetic stirring in steel casting). The expansion of fundamental knowledge about the process of solidification requires collecting data in the absence of density-based convection, while most of science's solidification data (and thus the equations that science has fitted to those data) have been obtained under the influence of gravity. Only relatively recently, through clever experimental design (e.g., drop towers, high altitude parabolic flights, and space laboratories), have investigators been able to study solidification in an environment with ""micro-gravity""."

Jan 1, 2001

By Virgil Optasanu, Yvon Lacroute, Eric Lesniewska, Tony Montessin, Pauline Vitry, Eric Bourillot, Cédric Plassard

A general challenge in metallic components is the need for materials research to improve the service lifetime of the structural tanks or tubes subjected to harsh environments or the storage medium for the products. One major problem is the formation of lightest chemical elements bubbles or different chemical association, which can have a significant impact on the mechanical properties and structural stability of materials. The high migration mobility of these light chemical elements in solids presents a challenge for experimental characterization. Here, we present work relating to an original non-destructive, with high spatial resolution, tomographic technique based on Scanning Microwave Microscopy (SMM), which is used to visualize in-depth chemical composition of solid solution of a light chemical element in a metal. The experiments showed the capacity of SMM to detect volume. Measurements realized at different frequencies give access to a tomographic study of the sample.

Jan 1, 2015

By M. I. Novgorodova

Most of the gold in the earth&apos;s crust occurs as finely-dispersed gold and accounts for much of the gold lost in extraction processes and during exploration for gold. The Compositions, sizes, and morphology of fine gold particles (0.01 to 10 ~m in diameter) were studied with high resolution electron microscopy coupled with electron microprobe and microdiffraction devices, using colloidal carbon replicas. Correlations were made between fine gold, mineral associations and ore genesis. The results provide qualitative information on the proportions of finely dispersed, invisible and visible gold distribution in ores. Such knowledge is fundamental when planning an optimum technological recovery process.

Jan 1, 1991

By Shun Fujieda, Shigeru Suzuki, Kozo Shinoda, Tetsuo Fujita

"Dowa Metals & Mining Co. Ltd. has developed and plant-practiced a unique scorodite synthesis technology (DMSP®) for arsenic immobilization by oxidizing Fe(ll) ions in the presence of As(V) ions. Dowa has improved the DMSP® technology and has developed the process extensively for other applications. This paper focuses on the applicability of the DMSP® for various cases of copper smelting, and introduces other technologies for fixing arsenic and recycling gallium from GaAs, simultaneously processing (fixing) arsenic and thallium, and fixing and recovering arsenic from dilute arsenic solutions. The DMSP® was found to be applicable not only for various processes in nonferrous smelting, but also for other applications with a high potential for reducing environmental problems.IntroductionDowa Metals & Mining Co. Ltd. developed a method for synthesizing scorodite at ambient pressure [1], The scorodite is precipitated by oxidizing Fe(II) ion in a high-concentration As(V) solution. The scorodite produced in this way does not readily release arsenic because of its high crystallinity. Dowa built a demonstration plant for this technology at the Kosaka Smelter and established the production of scorodite at 30 t As/month by treating intermediate products from copper smelting as the starting material. The DMSP® was demonstrated to be favorably applicable to copper smelting [2]. We are engaged in further increasing the amount of arsenic fixation by the use of this process. Further improvements in productivity, cost reduction and applicability in various processes have been devised. Dowa has been endeavoring to resolve other problems as well as to improve productivity. We have gained extensive knowledge on arsenic treatment in our endeavors, enabling us to solve problems and improve productivity. This paper introduces the investigations and developments related to DMSP®."

Jan 1, 2012

By Patrick R. Taylor

Titanium nitride has been synthesized in a thermal plasma reactor from ilmenite ore concentrate using methane and ammonia as the reactive gases. The product has been characterized by x-ray diffraction and SEM. Results show that a high concentration of methane favors the formation of iron, titanium nitride and titanium carbonitride. The formation of titanium carbonitride can be minimized by controlling the concentration of methane. The formation of TiN proceeds by the progressive reduction of the oxides of titanium to titanium, which is converted to titanium nitride.

Jan 1, 1998

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 Peijia Lin

Wheat straw was chemically modified by alkaline treatment followed by succinylation and sodium carbonate treatment for the use of cadmium and nickel adsorbent. The adsorption efficiency was calculated in different conditions. The experimental parameters were solution pH, adsorbent dosage, contact time and initial metal concentrations. The biosorbent was analysed by FTIR (Fourier- Transform Infrared Spectroscopy) to investigate the changes of surface functional group. The maximum adsorption percentages of cadmium (>99%) and nickel (>98%) were achieved using 5 g/L adsorbent with 50 mg/L initial metal concentrations. The adsorption kinetic study showed that the reaction was pseudo-second order kinetics and the adsorption isotherm was well fit by the Langmuir adsorption model. The dynamic column study indicates that modified adsorbent has a better adsorption capacity towards cadmium than nickel.

By Ho Jung Heo

The proper control of slag composition is a dominant factor affecting yield of iron as well as dephosphorization efficiency in an electric arc furnace (EAF) operation. Moreover, thermophysical properties of slags such as viscosity are strongly affected by the changes in slag composition. Slag foaming, which is also a function of viscosity, is directly connected with the yield of iron and thus optimum slag chemistry are highly required in view of thermodynamics and physical properties. Therefore, we analyzed the slag composition in commercial melt shop (70 ton EAF) with the aim of higher yield of iron as well as higher dephosphorization during EAF process.

By A. J. Davidson

A novel sensor is described for the measurement of the copper content of copper matte. Due to the high copper concentrations found in matte, potentiometric sensors are not sufficiently sensitive. A highly sensitive sensor has been developed based on a modification of the amperometric technique using a copper ion conductor, Cusicon. The results correlate closely with the theoretical predictions.

Jan 1, 1998

By Y. Shigeno

The reactivity of a porous solid is a strong function of its pore structure (porosity, pore surface area and pore size distribution). It follows that reactivity could be altered by altering pore structure; one way to achieve this is by chemical vapor infiltration whereby a gaseous species is reacted in the porous solid to produce a solid. Experiments were carried out in which the pore structures of various carbons were modified by cracking methane within the pores; oxidation rates of the carbons were then measured for both infiltrated and original samples. For coke it was found that two indices of coke performance used in the steel industry (CRI and CSR) can be greatly improved following a small amount of infiltration. Infiltration/oxidation results are interpreted in terms of measured pore structure changes.

Jan 1, 1993

By Damien Wagner

To reduce the emission of greenhouse gases by the steel industry, particularly for ironmaking, the production of DRI (Direct Reduced Iron) using hydrogen as the reducing gas instead of carbon monoxide is being considered. In this context, the reduction of pure hematite by hydrogen was studied at the laboratory scale, varying the experimental conditions and observing the rate and the course of the reaction. All the reduction experiments were performed in a thermobalance and supplementary characterization methods were used like scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectrometry. The influence of rising temperature in the range 550-900°C is to accelerate the reaction; no slowing down was observed, contrary to some literature conclusions. A series of experiments consisted in interrupting the runs before complete conversion, thus enabling the characterization of partially reduced samples. Interpretation confirms the occurrence of three successive and rather separate reduction steps, through magnetite and wustite to iron, and illustrates a clear structural evolution of the samples. Finally, the influence of the sample type was revealed comparing a regular powder, a nanopowder and a sintered sample. The regular powder proved to be the most reactive despite its larger grain size, due to a more porous final structure.

Jan 1, 2006

Silver has the highest electrical conductivity of all metals and consequently this property is an attractive feature which makes it a leading candidate for use in electronic devices. The research conducted was focused primarily on the development of a process for obtaining a deposited silver-coating onto alumina, for applications related to electrical-conducting devices and, ancillarily, catalysts. Alumina balls and plane substrates were utilized for the investigation. The coating process employed an aqueous arnmoniacal silver-nitrate electrolytes with a formaldehyde solution as the reductant. Modifying additives - an activator which would be expected to promote good deposition-characteristics onto the (dielectric) substrate and an inhibitor which would obviate homogeneous reduction (precipitation) of silver was observed when the activator-containing silver-electrolyte reductant constituents were combined. However, the silver-electrolyte/reductant system with inhibitor could be employed (at 80°C) to achieve a viable (subject to future research optimization) coating on alumina. The influence of the processing temperature on the deposition process was delineated during the course of the research. The morphology of the deposited-silver on the alumina balls was assessed by SEM imaging. A tape-peel test was employed, with the plane substrates, to semi-quantitatively characterize the adhesion to the alumina.

Jan 1, 1998

By W. Mueller

The function of a process mineralogist in the operation of a copper mine and plant is to assist in the identification and classification of the operation&apos;s main throughput. These include ore, concentrates, slag and matte, and to a lesser extent, refined products. In addition, a number of other products not normally thought of in association with mineralogy are examined. These include scales from submersible pumps, failed boiler tubes, acid plant, and shaft furnace; characterization of inclusions in failed compressor gear teeth as well as in copper rod; and flue dusts from a smelter, air transported particulates and coatings on passive copper anodes in the refinery. Techniques and equipment required for these studies include simple hand magnets to the high intensity Isodynamic separator, visual examination to electron microscopes, x-ray equipment, DTA, IR, heavy liquid separation, and contracted services of custom laboratories. Several examined products from Magma Copper Company have been selected to illustrate the range of techniques and equipment required by a process mineralogist.

Jan 1, 1981

By Wolfgang Baum

Case studies from epithermal gold-silver deposits in the western United States and in Latin America show that the routine use of process-related mineralogical studies has become an important tool for the reduction of development, capital and operating costs. Bypassing the mineralogical characteristics of epithermal gold-silver ores, as a result of fast-track development approaches, has resulted in multimillion dollar metal losses and/or in considerable modification costs of existing operations.

Jan 1, 1988

By Dan A. Mackie

Continuous leaching of precious metals ores in a vat is possible using a jigging technique. This patented method promises to be competitive with heap leaching, particularly in northern climates, difficult terrain, high precipiptation regions, and environmentally sensitive areas. The paper discusses test work to date, plans for pilot plant testing and basic economics

Jan 1, 1990

By C. O. Bounds

The magnetic properties of (NdDy)15Fe78B6 sintered magnets have been evaluated using powder prepared by Inert gas atomization. The atomized powder had a particle size distribution from 1 to approximate 1000 microns. The as atomized powders have been sieved into, coarse, intermediate, and fine fractions; magnetic properties were evaluated for the as produced powder and each fraction. A B, of 11.7 kG, a Hci of 11.0 kOe and a BHmax of 32.5 MGOe was -obtained on a sintered magnet made from the as-atomized powder. The magnet made from coarse powder exhibited a slightly higher B, of 12.1 kG, while that from fine powder showed a decrease in B, to 11.2 kG. Hydrogen decrepitation has been utilized to study its effect on the magnetic properties. Finally, cast ingots with a definite columnar structure have also been used to compare the magnetic properties of magnets of the same nominal, composition but of different alloy preparation process. Hydrogen decrepitation does not appear to improve the magnetic properties of magnets made from thin cast ingots. However, it does show a significant improvement in the Hci of magnets made from the atomized powders. Possible causes for the differences in the magnetic properties on magnets made from each process have been discussed in the paper.

Jan 1, 1992

"An experimental study has been performed to investigate the dispersed phase holdup induced by a high-strength submerged gas injection in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor using two different tuyere configurations. The air flow rates varied from 0.00599 m3/sec to 0.01312 m3/sec. In these series of experiments, water height and kerosene height were kept constant at 0.23m and 0.02m respectively. The dispersed phase holdup was determined at various gas flow rates, and tuyere orientations by using water and kerosene.The dispersed phase holdup increased with gas injection rate and decreased with vertical distance from the original interface. At constant gas flow rate, as the vertical distance increased in the centerline, off-center configuration of nozzles displayed higher values of the dispersed phase holdup than those of the center configuration. The variation of the dispersed phase holdup with the dimensionless axial distance and the gas injection rate was correlated by using the Modified Froude Number. The experimental values of the dispersed phase holdup were found to be in good agreement with the calculated values obtained from the correlation equations."

Jan 1, 1999

By Yue Tian, Shengqian Wang, Lifeng Zhang

This paper is to discuss the removal of non-metallic inclusions from molten steel using a high frequency magnetic field. In experiments, a certain amount of aluminum was added to the molten steel in a crucible to generate aluminum inclusions. A layer of aluminum clusters were observed close to the wall of the crucible after the electromagnetic (EM) field was imposed. Three dimensional EM field and fluid flow simulation were performed and showed that over 91% inclusions transported to the skin depth (2.31 mm) of the molten steel. The calculation of inclusion removal agreed well with the experimental observation. The separation mechanisms of inclusions from the molten steel by the high frequency EM field were discussed.

Jan 1, 2014