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An iridium oxide coated titanium electrode was tested as anode in copper electrowinning. Initial results confmed that the DSA-type anode was significantly more active for oxygen evolution than traditional lead anodes. However, during longer runs, the anode potential was observed to increase linearly at a rate of 220 mV/year. Scanning elecuon microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that the anode passivation could be attributed to elecuochemical dissolution of the coating. The effect on the anode potential of organic additives (glue and thiourea) and lead in solution was also examined. A preliminary economic evaluation of the anodes is given.

Jan 1, 1992

By K. Osseo-Asare

It is possible to form a two-phase system in certain polymerlinorganic salt/water mixtures, such as those containing the polymer polyethylene glycol (PEG). Such aqueous biphase systems have many of the separation characteristics of conventional solvent? extraction systems, but are environmentally friendlier. Just like the well-known organic solvent/water two-phase system, the top polymer-rich phase is more hydrophobic. and the bottom salt-rich phase more hydrophilic. The partition of dispersed? particles is dependent on the interfacial interaction between the particles and the conjugate aqueous biphase solutions. In particular, the hydrophilic/hydrophobic properties of the surface determine the transfer of the dispersed particles into either the top (more hydrophilic) phase or the bottom (more hydrophobic) phase. Accordingly, differences in the surface chemistry of particles can be exploited to achieve selective separations. In this work, several approaches to separation control will be discussed. using pyrite (FeS2), alumina (AI203). hematite (Fe203), silica (Si02), and titania (Ti02) as model particulate materials. For metal sulfides, pH and redox potential can be used to alter the hydrophobicity/hydrophilicity of the particles. In ?the case of oxides. polymer adsorption and collector adsorption may be exploited to facilitate particle transfer.

Jan 1, 1999

By H. Itou, J. M. Toguri, T. Takasu

"Marangoni convection has a large effect on materials processing since it remarkably enhances heat and mass transport near a free interface. To have a better understanding of the behavior of Marangoni convection in molten salts, observation and calculation of the thermal convection in a column held between a pair of Pt disks (2mm in diameter) fixed to hot thermocouples, were carried out.Calculated flow patterns and absolute values of fluid velocity agreed well with the observed results. When the temperatures of both disks were set equal and the height of liquid column was 2.4mm, four vortexes were generated on the longitudinal plane with a typical velocity of 15mm/s . From the calculated isothermal lines, the behavior of the enhanced heat transport was obvious; fluid heated at the disks was conveyed to the free surface and the cooled fluid at the surface was conveyed to the inner region. Increase in the height of column and/or increase in the absolute value of applied temperature difference lead to increase in fluid velocity lineally in this calculation range.IntroductionIn the processing of many materials, fluid flow of melts has a large effect on refining capabilities and on the characteristics of the produced material. Marangoni convection is generated when a spatial gradient of interfacial tension exists on the free interface due to differences in temperature and/or concentration. This promotes heat and mass transfer locally near the interface.For example, Marangoni convection which are created following the dissolution of interfacially active materials, increases the local corrosion rate of refractories (1-3). In absorption and discharge of oxygen and/or nitrogen in a molten metal, the effective reaction rate of the gas components through the gas-liquid interface increases (4-7). Also in crystal growth, the distribution of defects and impurities in the crystal is affected and this can alter its quality (8-11 ). The temperature distribution is also affected and can greatly change the productivity. For these reasons, the effectiveness of Marangoni convection in refining should be quantitatively clarified and its control should be better understood."

Jan 1, 1997

By T. Shibasaki

Purification of copper electrolyte at Naoshima is carried out by two stage liberation to completely depress copper and impurity ions followed by concentration of the solution to produce crude nikel sulfate as by-product. A new nickel recovering process has been developed and pilot tested recently. It consists of the following process steps.; neutralization of spent electrolyte from liberation section to remove free acid and most part of remaining impurity ions, refining and nickel concentration by solvent extraction, and crystallization of pure nickel sulfate from concentrated strip solution. This paper describes the results of laboratory and pilot plant tests, then briefly discusses feasibility of the proposed process.

Jan 1, 1987

By Merete Tangstad, Gabriella Tranell, Jeff Kline

"Raman spectroscopy as an instrumental technique for the determination of silicate structure is widely accepted. This method was utilized for analysis of structural modifications associated with the addition of network modifying species. Silicate melts are described by the extent of oxygen bridging. Therefore, understanding the effect different oxides have on modifying the silicate structure will provide valuable information regarding the removal of boron from silicon in slag refining processes. Samples ranging from CaO/SiO2 = 0.56-1.2 were evaluated with and without varying concentrations of B2O3. The addition of CaO to SiO2 revealed Q2 species constitute 45% of the Qn species and addition of B2O3 to the high concentration CaO system results in an increase in Q2 and a decrease in Q0 . The disappearance of the Raman band associated to the three-member ring in the low concentrated CaO system indicates boron addition and destruction of the ring.IntroductionExtensive studies on the structure of silicate systems have been performed using Raman spectroscopy with consensus on the Raman shift associated with different bridging oxygen units [1]. Most of these studies are motivated by the lack of a fundamental understanding of the processes involved in petrology. Due to this, an opportunity exists to build on the knowledge obtained from these studies and conduct more research on slag structures relevant to industrial applications, as these systems are often compositionally similar to magmatic melts. Raman spectroscopic studies of industrial slags will provide insight into the possible structural modifications necessary to enhance removal of impurity species from the metal phase to the slag phase."

Jan 1, 2012

By Ronald K. Riddle

The processing of lateritic ores in rotary drying and preheating/pre-reduction systems has historically been plagued by problems associated with significant dust generation. These problems include handling issues, kiln capacity limitations, negative impacts on furnace stability, a reduction in nickel recovery and higher operating costs. The dust is formed in the rotary devices during heating and tumbling due to the following three mechanisms: (I) mechanical dccrepitation of the ore as a result of tumbling and attrition, (2) thermal decrepitation during rapid vaporization of internal free and bound water, and the (3) loss of free moisture which functions as a binder. This paper investigates the causes of dust formation, provides methods to reduce dust carryover from the rotary devices, and finally offers methods to recover the dust in the existing pyrometallurgical process. Keywords: Laterite, Drying, Rotary, Dust

Jan 1, 2004

By Michael B. Mooiman, David J. Kinneberg, Philippe Cettou, Leo W. Simpson, Pierre Ramoni

"The demand for high purity precious metals began with certain industrial applications having uncompromising requirements for quality and performance. As industrial uses proliferated and as the jewelry industry became increasingly sophisticated, the demand for high purity gold has reached the point where 99.99% is now the standard in the marketplace. A similar evolution is expected for other precious metals.In this paper, we examine both the production and use of high purity precious metals, specifically gold, silver, platinum and palladium. After defining what is meant by ""high purity"", we discuss the various analytical techniques used for measuring impurity concentrations. Next, we review process strategies employed by extractive metallurgists to produce high purity precious metals. Lastly, we describe some of the principal applications for high purity materials including thick films, thin films, bonding wire, thermocouples and jewelry manufacture.Precious metals have unique physical properties that, despite their expense (and the ever-continuing search for more economical alternatives), make substitution difficult if not impossible. These physical properties are dramatically affected by small concentrations of certain impurities. As long as manufacturers continue to demand quality and performance, there will be a need for high purity precious metals.IntroductionIn the precious metals industry, the qualifier ""high purity"" describes any specification over and above commodity grade. High purity specifications delineate lower limits on overall metal purity or upper limits on individual impurities or both. Sometimes, if these special requirements become commonplace, either because of improved refining technology or because of market pressures, yesterday's ""high purity"" material becomes tomorrow's commodity. This transition is now occurring with gold bullion and probably will soon occur with platinum and palladium as industrial use of these materials grows."

Jan 1, 1998

By Jian Li, Guo Chen, Bingguo Liu, Hongying Xia, Jinhui Peng, Libo Zhang

"Decomposition of ammonium tetramolybdate to prepare Mo03 using silicon carbide crucible in microwave fields was investigated. The results were analyzed Using TG-DTG and X-ray diffraction. Meanwhile, the effects of heating rat, material thickness, socking time, socking temperature on the structure of preparing Mo03 were studied. TG-DTG curves show that the decomposition process of ammonium tetramolybdate is only one stage, in the temperature range 300-350°C, whose begin to decompose when temperature increases beyond 300°C. The molybdenum trioxide was prepared by thermal decomposition. The quality ofMo03 was not affected under the heating rat is 12°C/min. It was beneficial for decomposition ratio with the lower material thickness, longer soaking time, and higher soaking temperature. XRD curves showed that it is viable method for preparation of Mo03 by decomposition from ammonium tetramolybdate in microwave fields.IntroductionMolybdenum is widely used in national defense, aviation, industrial and agricultural production as rare refractory metal. Molybdenum trioxide is vital raw materials for the process of preparation of molybdenum. The traditional production technology of molybdenum oxide is that ammonium tetramolybdate is calcined in rotary kiln or 4-tube furnace [J,2J. But the longer production time, the higher production cost, the lower furnace thermal efficiency, and bigger the energy consumption, especially the powder is easy to leak, the working environment is poor by using rotary kiln [ 3 l _ The particle of molybdenum oxide is non-uniform by using 4-tube furnace because of the uneven temperature of every tube and the poor exhaust of boat bottom [4l _ However microwave heating is quick and uniformity, it is a meaningful research that the microwave is used in the process of calcining ammonium tetramolybdate."

Jan 1, 2013

By M. M. Kim

As-electrogalvanized coatings of pure Zn, Zn-11% Fe, and Zn-18% Fe coatings were characterized in terms of initial crystal structure and surface morphology. Samples were then subjected to heat treatments simulating the paint bake cycle of automobile manufacturers. Surface morphology changes were correlated with the process variables, and crystallo.graphic changes were interpreted by mapping heat treatment routes on the Fe-Zn phase diagram. The morphology of pure zinc electrogalvanized coatings with heat treatment from platelets to smeared platelets. The zn-11% Fe coating changes with heat treatment from tetrahedral nodules to a mixture of round and tetrahedral nodules, with the Zn-:18% Fe coating always having round nodules. Regarding crystal structure, a critical transformation time can be defined at any selected temperature, below which the crystal structure does not change. This temperature is related to iron content.

Jan 1, 1990

By T. H. Jeffers

The U.S. Bureau of Mines' Salt Lake City Research Center. has developed porous polymeric beads containing immobilized non-living biological materials for extracting metal contaminants? from wastewater&. Immobilized biological materials include peat moss, algae, biological polymers, and other materials that demonstrate high .affinities for heavy metals. The beads, designated as BIO-FIX beads, have distinct advantages over traditional methods of utilizing biological materials in that they have excellent handling characteristics . and can be used in conventional processing equipment or low-maintenance systems.. Toxic metals such as copper, cadmium, zinc, lead, and mercury are several of the many heavy metals effectively removed from mine wastewater& using B'IO"FIX beads. Continuous cyclic testing indicated that the beads continued to produce treated effluents which met National Drinking Water Standards (NDIJS) after 175 loading-elution cycles, Adsorbed metals were removed from the beads using dilute ?mineral .acids. In many cases" the extracted metals were further concentrated to enable processors to reclaim the metals, thus minimizing the generation of a hazardous sludge. Tests indicated that use of the beads in a low-maintenance system was particularly effective for treating remote acid mine drainage waters? and small toxic seeps from hardrock mining districts ..

Jan 1, 1991

By Akira Yazawa

Experimental results for the distribution ratios of various elements between the slag, matte and/or copper in the silica-saturated copper smelting system were summarized. The experiments were carried out under an oxidative smelting condition with S02 gas flow, and also a reductive smelting condition equilibrating with metallic copper or iron. To evaluate the results thermodynamically, the availability of one atom cation base expression for the constituent compounds is emphasized from both of theoretical and practical standpoints. Both of oxidic and sulfidic dissolutions in slag are postulated for some elements such as copper, nickel and lead., and the experimental results are reasonably explained thermo-dynamically. The results for the mutual solubility between matte and ferrite slag and the distribution of minor elements between liquid copper and ferrite slag are also discussed.

Jan 1, 1983

By P. Koskinen

Outokumpu Oy has 30 years' experience in nickel production. It is mainly based on the technology developed within the company. The production chain starts from the mines reaching to the high-grade cathode nickel and the stainless steel manufacturing. As a multi-metal producer Outokumpu has the advantage to exploit from nickel raw materials also other valuable metals and intermediate products which can be processed at the company's various plants. The main source of nickel concentrate is nowadays the Enonkoski Mine started up in early 1986. It is the most modern mine in Finland being provided with the latest Finnish high-tech systems. Nickel concentrates are smelted at the Harjavalta Works using Outokumpu's internationally well-known flash smelting method. Also nickel containing residues and secondaries' are used as raw materials. The high-grade nickel matte from the smelter is then refined at the nickel refinery in a hydrometallurgical process, which was also developed by the company's own research staff. These processes have been continually improved and capacities gradually enlarged to 18 000 mtpy of cathode nickel. Besides plating, melting and superalloying purposes part of the nickel ends in stainless steel at the Tornio Works. The production was started in 1976 and has reached an established position on the European market.

Jan 1, 1988

By J. D. Sloop

This paper discusses the current state of EAF dust recycling at AmeriSteel's Dust Processing Division in Jackson, Tennessee. Included are a brief history of the plant, a description of the facility, a description of the process, and operating data.

Jan 1, 2000

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993

By Bin Zhu, Mingmei Zhu, Hong Zhou, Xiaofei Dou, Bin Xie, Yu Wang, Tiancheng Lin

In this study, the formation of 2CaO·SiO2 and 3CaO·P2O5 solid solution (nC2S-C3P) in hot metal dephosphorization process is discussed. The variations of CaO and SiO2 mass, both in nC2S-C3P solid solution phase and liquid slag phase with increasing P2O5 mass in CaO-SiO2-FetO-P2O5 slags were calculated using Factsage software. CaO-SiO2-FeOt-P2O5 slag containing up to 18 % P2O5 was melted at 1823 K then cooled to 1673 K. The contents of CaO and SiO2 both in the solid solution phase and liquid slag phase of quenched samples were observed and analyzed by SEM/EDS. Both the calculated and experimental results show that the contents of CaO and SiO2 in the solid solution phase decreased, just opposite in the liquid slag phase, with increasing P2O5 content in the slags. Formation mechanism of nC2S-C3P solid solution in the slags was derived based on the ionic structure theory of molten slag. The SiO4 4- in the nC2S-C3P solid solution can be replaced by PO4 3- in the liquid phase resulting in the increasing of free Ca2+ and SiO4 4- in liquid phase.

Jan 1, 2015

By Jose F. Hevia

This study is part of a broader project on the hydrothermal conversion of copper concentrates to metallic copper by solid state reactions in which the copper remains localized in the solid phases. The kinetics of the solid/solid hydrothermal hydrogen reduction of tenorite (CuO) and cuprite (Cu,O) to metallic copper are presented. After an induction period, the process is governed initially by a nucleation step followed by rapid solid state reduction. Nucleation promoter agents decrease the induction period and control the particle morphology. Separate nucleation and reduction rate processes have been identified. Following nucleation, reduction follows a shrinking core process.

Jan 1, 1994

By William D. Riley

The U. S. Bureau of Mines has developed technology to recover by-product materials from aluminum scrap using engineered scavenger compounds (ESC). ESCs are structural oxides with a channel or tunnel structure that allows them to hold ions of a specitksizes and charges. The scavenging reaction is easily reversible allowing the ESC to be recharged for continued use and the ion is recovered as an electro deposit. Key features of this novel technology are; a) ESC ,systems are designed to have a high degree of selectivity for a desired ionic species. b) The recovered mater.ial requires little or no additional reprocessing prior to reuse. Two current uses for the ESC technology that are described in this paper are the removal and recycle oflithium (Li) from lithium aluminum (Li-AL) alloys; and, using ESCs as a replacement for the conventional demaging (magnesium removal) technology used by the secondary casting industry. Research indicates that the ESC technology proposed for both these applications has either 'distinct economic and/or environmental advantages over previously employed methods of recovering. metal values from aluminum scrap.

Jan 1, 1995

By Patrick R. Taylor

Glass is used for immobilization of radioactive and hazardous wastes due to its durability and ability to accept a variety of waste constituents into its network structure. Alternative high temperature vitrification techniques have the advantage of increased throughput, increased waste loading and being applicable to variable and heterogeneous waste streams. However, the increased processing temperature places further concerns on the increased volatilization of contaminants, and increased corrosion and erosion of me Iter components. A database of melt properties at higher temperatures, such as partitioning, viscosity, density and electrical conductivity, in the temperature range of 1400-20000 K are being developed.

Jan 1, 2000

By Xuefeng She, Qingguo Xue, Jingsong Wang, Guang Wang

Iron nugget could be got at high temperature using carbon composite pellet, which were made by the mixture of ludwigite and reducing agent. In order to reduce sulfur content in the nugget, effects of additives on the desulfurization was investigated. The sulfur content could be dramatically reduced if the CaO was introduced into the pellet and the sulfur content was as low as 0.046wt.% when the addition amount of CaO was 5wt.%. However, the melting separation of pellet became increasingly difficult and the yield of iron decreased when CaO content in the pellet gradually increased. Na2CO3 could also reduce the sulfur content in the iron nugget and made the iron and slag separate difficultly as well. When 6wt.% Na2CO3 was added into the pellet, the pellet was too difficult to melt separation and the sulfur content in the nugget was 0.084wt.%, which didn’t meet the need of steel making.

Jan 1, 2015

By A. René Silva

The separation of Fe(III) from simulated Ni(II) solutions using different ion exchange resins was studied. The resins tested included cation exchangers with sulfonic and carboxylic groups and chelating resins with iminodiacetic, aminophosphonic, and mixed sulfonic and phosphonic groups. The dosage of resins was varied from 0.1 to 0.5 g/mL to study the impact of resin type and dosage on iron separation from simulated nickel leach solution containing 25 g/L Ni(II) and 25 g/L Fe(III) at pH 1.5. Also, the effects of different metal ion concentrations, Fe (III):Ni(II) ratios in solution, pH, and adsorption times were investigated. Experimental results demonstrate that all the chelating resins selected favored the adsorption of Fe(III) over Ni(II) with high Fe(III) loading. Soft cation exchange resins also favored the adsorption of Fe(III) over Ni(II), but no significant Fe(III) loading was observed. In contrast, strong cation exchange resins did not show adsorption preferences. The most efficient separation was observed using resin with aminophosphonic groups at resin dosage of 0.2 g/mL, having a Fe(III) adsorption over 94% and Ni(II) adsorption below 5%.