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By Kazuya Koyama

The leaching of copper from a printed circuit board (PCB) and the electrodeposition of copper from a cuprous solution in ammoniacal alkaline solutions were examined in order to develop an energy-saving hydrometallurgical process for copper recovery from electronic scrap. In the leaching experiments, copper in the PCB was oxidized by Cu(II), and Cu(I)-ammine complex ions were formed. The copper(I)-ammine complex slightly depressed the leaching rate, while Cu(II)?ammine markedly enhanced it. During the electrodeposition experiments, the current efficiency of copper deposition was approximately 100% in the current density range of 200 to 1000 Am-2. The electrodeposition of copper from the Cu(I)-ammine complex solution favored the production of plates rather than powders.

Jan 1, 2003

By M. F. Chambers

Neodymium metal was electrowon from a molten-chloride electrolyte at 650° C using a molten-metal cathode. A 50 mol pct NdC13-50 mol pct KC1 mixture served as the electrolyte. Binary metal alloys of 'Mg with Zn and Mg with Cd were used as molten cathodes. Under the best conditions, current efficiencies were 90 pct with a Mg-Zn cathode and 80 pct with a Mg-Cd cathode. Vacuum distillation was performed at 1,100° C for 30 min under a vacuum of 10-3 to separate the cathode metals from the neodymium. Neodymium metal of 99.9+ pct purity was recovered from the Mg-Cd alloy cathode. Almost 2 pct zinc remained in the neodymium recovered from the Mg-Zn alloy.

Jan 1, 1989

By M. G. King

In 1982, Asarco operated six smelters and refineries producing primary copper, lead, zinc, silver and gold. At that time Asarco was still reliant on its custom smelting and refining roots and mined only 25% of its smelting and refining capacity for copper and 10% of its lead smelting and refining capacity. By 1992, Asarco had been reshaped to become largely an integrated primary metal producer operating four smelters and three refineries. Zinc is no longer refined and the mining capacity has been increased to meet 100% of copper smelting and 50% of lead smelting needs. Only one custom smelter is in operation. This paper describes the metallurgical changes and challenges which have occurred in this restructuring of Asarco's operations while maintaining Asarco's position as one of the largest non-ferrous metals producers in the world.

Jan 1, 1993

By Liping Li

A comprehensive three-dimensional two-phase mathematical model was developed to represent a channel type reactor with intense bottom gas agitation. Tracer dispersion and particle tracing methods were used to conduct the analysis based on the solution of the Navier-Stokes equations. Different operational parameters, such is gas volume flow rate. bubbler separation aspect ratios and liquid Input flow rates, were investigated for the purpose of reactor optimization. The numerical calculations were compared with experimental results obtained at the University of Missouri and a good general agreement was observed. Relatively low longitudinal mixing was observed characterizing the system as a "plug-flow" type reactor, in contrast to the intense vertical mixing, under the conditions investigated. Some general mixing characteristics are also discussed In connection to the behavior of other metallurgical reactors.

Jan 1, 1996

By Richard M. RusselI, Jerry Sweeney

"The disposal of Aluminum slag wastes continues to challenge an otherwise environmentally beneficial and highly desirable industry - Aluminum Recycling. Slag wastes contain soluble salts that can be reused in aluminum smelting. Reclaiming salt is a logical first step in eliminating slag waste.Reclaiming salt flux has been conducted on a limited basis in the United States for reasons of economy. Practical methods and rising landfill tipping fees will increase the number of plants which opt to recover salts from slag wastes.The authors share their experiences in the design, operation and startup of a commercial scale flux reclamation plant operated by Tennessee Aluminum Processors at Mt. Pleasant Tennessee. This paper identifies three elements that allow practical operations:• Minimizing Evaporator Heat Duty• Simplifying Evaporator Operations• Potassium Chloride Fortification of the Recycled Salt"

Jan 1, 2000

By G Hope, C Young, R. N. Gow

"The presence of enargite (Cu3AsS4) is problematic in gold processing as it is refractory, increasing cyanide and oxygen consumption, and enviromnentally hazardous. Selective leaching and treatment of the arsenic would prove advantageous to conventional gold leaching methods. The reactivity of enargite samples from Montana, US and Quiruvilca, Peru were studied under alkaline conditions, pH range of 8-13, using a cyclic voltammetry corrosion cell setup. Raman spectra of the surface were taken during and after cycling to compare surface species against theoretical predominance diagrams. Under slightly oxidizing conditions, covellite (CuS) peaks were found on the surface in a short matter of time, above - 200m V vs SHE for pH 9-13, suggesting arsenic leaching, but for longer conditioning times, elemental sulfur peaks were also found, which created a passivating surface layer. By operating above pH 12, under reducing conditions, ~-500mV vs SHE, arsenic can be leached as a thioarsenate (AsS4-xOx3-), without sulfur formation.IntroductionEnviromnental limitations on pyrometallurgical processing of arsenic has pushed the desire to process enargite-, Cu3AsS4, bearing concentrates towards a hydrometallurgical solution. Attempts to process can be broken down into two categories - the co-dissolution of arsenic and copper under acidic conditions or the selective leaching of arsenic under basic conditions. The selective leaching of arsenic would preferably leave behind a chalcocite, Cu2S, or covellite, CuS, phase that would be more amenable to conventional processing methods of the copper and gold industries. These methods employ bi- or poly-sulfides to leach arsenic as Assl· [1-4], hypochlorite leaching [5-7], ammoniacal leaching [8] or fine grinding to mechanically activate the enargite surface and increase normally slow reaction kinetics[9]. This study looked into the surface formations of an enargite electrode under alkaline conditions, in a pH range from 8-13, as it cycled from -1000 mV to 1000 mV vs SHE. The understanding of the formations and under what conditions they form will be helpful in further development of any of the aforementioned processes."

Jan 1, 2012

By Laurence G. Dyer, David G. Dixon, John Rumball, Maziar Eghbalnia, Edouard Asselin

"Linear scan voltarnmetry was used to determine the reactions that occur during the cyanidation of petzite (Ag3AuTe2). Gold oxidation in petzite requires more oxidising conditions than are required for pure gold, it also does not achieve the same current (related to reaction rate). Tellurium oxidation occurs at a similar potential in water and cyanide, but as a component of petzite is impeded somewhat in water, likely due to the stability of the precious metals. Pre-treatment of petzite to oxidise tellurium in the absence of cyanide prior to gold recovery appears to be at least moderately successful.IntroductionWhile gold occurs most prevalently in its native form, many other gold bearing phases appear throughout natural systems [I]. Tellurides are a common group of such minerals, many of which also contain silver, often existing in association with native gold deposits. The six major gold-bearing tellurides are calaverite (AuTe2), sylvanite [(Au, Ag)2Te4], montbrayite [(AuSb)zTe3], krennerite [(Au1-x, Ag,)Te2], petzite (Ag3AuTe2) and muthmannite (AuAgTe2) [2]. While several other phases exist they are much more complex (i .e. buckhornite), which dilutes and confuses the influence of each specific component. Studies of gold tellurides have predominantly focussed on calaverite as it is the simplest and most common phase, however petzite, commonly found in Australia and North America, is the focus of this investigation.Gold processing via cyanidation has been operated for more than a century and is a highly effective hydrometallurgical treatment of native gold deposits. However, some gold alloys such as tellurides have proven to be somewhat less responsive under the same conditions. Several groups have shown that gold/silver tellurides are amenable to cyanidation, but are significantly more refractory than native gold [3]. Pre-oxidation steps have been tested to remove constituents that would consume cyanide such as sulfides. Such species are also linked to the precipitation of oxidised telluriwn, forming a passive layer, further inhibiting gold recovery [2]. It is uncertain to the definite reasons underpinning the refractory nature of precious metal tellurides in conventional cyanidation."

Jan 1, 2012

By Gowda H. S. Desai, A. Herbert Mervin, P. G. Mukunda

"The mechanical properties of cast iron depend on the graphite morphology and characteristics of metallic matrix. In spheroidal graphite iron these properties are affected by the nodule count, nodule percentage, nodularity, nodules per square mm, nodule types and size distribution. In this work an attempt is made to study of the effect of centrifugal and gravity casting process on the morphology and mechanical properties. A comparison of microstructure and mechanical properties of specimens of the cast are studied. It has been observed that the centrifugal effect produces an increase in rupture strain but hardness is unaffected. In microstructure it has been observed that the centrifugal effect produces an increase in the number of bigger nodules and decrease in the number of smaller nodules and an increase of nodules per square mm. It has no effect on nodularity percentage. The centrifugal casting process produces better mechanical properties.IntroductionCast iron, the first man-made composite, is at least 2500 years old. It remains the most important casting material, with over 70% of the total world tonnage [1,7]. The main reasons for cast irons longevity are its wide range of mechanical and physical properties coupled with its competitive price [l]. Gray cast iron is traditionally used in many industries because it is characterized by a flexibility of use, excellent castability, low cost, wide range of achievable mechanical properties. Gray cast irons are selected according to their tensile strength, high modulus of elasticity, good wear resistance and good machinability are desired and for this a high-strength cast iron is selected [2].Flake Graphite and Spheroidal Graphite irons are predominantly being used to manufacture heavy automobile components throughout the world. The properties of gray iron castings are much dependent on foundry practice. Perhaps the most interesting feature of the family of cast irons is the morphology of the graphite phase, which occurs as a result of changes in chemical composition, melting, melt handling techniques and the process of solidification and subsequent cooling. The significance of these differences through graphite morphology is observed primarily in their effect on the physical and mechanical properties of the iron, but in the foundries these are also known to influence the ability to manufacture sound and dependable castings."

Jan 1, 2013

By Ruth Marlene Campomanes Santana, Michel Tieccher, Marcondes Mafacioli Pacheco, Juliano Urach

"IntroductionThe gaseous emissions of fuel burning by mobile sources are responsible for incidence and increase of many lung and cardiovascular diseases (Braga et al., 2007). These implications can watch in morbity as much as mortality, even when the levels of pollution are considerate restrained or lower. (Leite et al., 2002).Sample of mobile sources exhausts contain not only particles directly shaped by burning, but also secondary particles that results of reaction between other compounds (Burtscher, 2004).One of the principal pollutants produced by combustion process with major toxicity and raiser of adverse effects to health is the particulate material. In its constitution there are fine and ultrafine particles that can to extend deep portion of breath system, break epithelial barrier and reach the interstitial of lungs and then, to unleash inflammatory process (Arbex, 2004).The Particulate Material is employed to define a mixture of solid particles and liquid drops suspense in atmosphere. Queiroz et al. (2007) declare that this material can be divided in two types separated by size interval that together, represent the major class of disperse particles: the fine particles type of 2,5 µm de (breath particulate) and the type of earthliness particles, major than 2,5 µm to 10 µm (inhale particle). The difference of size between the particles influences on the physics and chemistry properties. They affirm that exist correlation between size of particle and heavy metals; how many lower was the dimension of particulate materials, major is the concentration of heavy metals.The inhale particulate (MP10) that is object of present study can exhibit in your composition sulfates, nitrates, amoniacal, marine salt (NaCl), soil elements (Al, Ca, Fe, Si, Ti), metals (Cd, Cr, Cu, Ni, Pb, V, Zn) and water (Queiroz et al., 2007).Recent studies have exhibit strong relation between daily levels of particulate material inhale (MP10) with diameter until 10 µm and others pollutants and one infinity of effects to health that go since total mortality of population, sicken for specific causes until congenital bad formation or even difficult win weight by the fern during gestation (Gouveia et al., 2006)."

Jan 1, 2008

By Elsa Olivetti, Randolph Kirchain, Gabrielle Gaustad

"As scrap usage increases, it is often necessary to “dilute” the melt with primary aluminum to ensure the finished product meets compositional specifications. Secondary raw materials, particularly postconsumer scraps, often include high levels of unwanted or “tramp” elements, such as iron and silicon in the case of aluminum. Recent literature on this issue cites several causes including inherent contamination during processing as well as ineffective segmentation at end-of-life. To address this accumulation problem, “upgrading” solutions have been developed including: dismantling of end-of-life products, spectrographic or magnetic sorting of shredded scrap, and “filtration” technologies that remove tramp elements in the melt. Although it is clear that upgrading strategies enable increased usage of scrap, it is not clear that they would be economic or efficient. This work presents a set of analytical methods, based on chance constrained optimization, to quantify the potential environmental and economic value of several scrap upgrading technologies.IntroductionAluminum recycling has a number of key environmental and economic benefits. Compared to other materials, aluminum production has one of the largest energy differences between primary and secondary production: 175 MJ/kg for primary compared to 10-20 MJ/kg for secondary[1]. With energy and cost savings in mind, many producers now have targets of increasing their usage of secondary materials[2, 3]. However, the accumulation of impurities in these recycled material streams provides a significant compositional barrier to these goals[4].A growing number of studies and literature would suggest that accumulation of unwanted elements is a growing problem, in all recycled material streams. In the case of aluminum, the list of problematic impurities is quite large, including but not limited to: Si[5, 6], Mg, Ni, Zn, Pb, Cr[7], Fe[5-7], Cu[6, 7], V, and Mn[6]. Metals recycling is a metallurgical process and is therefore governed by the laws of thermodynamics. The removal of unwanted elements in the scrap stream is dictated by the energy considerations of the melt process. Compared to many metals, aluminum has a high degree of difficulty in the removal of tramp elements, due to thermodynamic barriers. Therefore, with no simple thermodynamic solution, producers must identify strategies through-out the production process to mitigate this elemental accumulation."

Jan 1, 2008

By S. Aguayo-Salinas, J. L. Valenzuela-García, A. L. Leal-Cruz, M. I. Pech-Canul, M. T. Certucha-Barragán

"The aim of this research was to carry out a comparative and systematic study of the degradation of cyanide by hybrid natural/biodegradation and biodegradation methods using a mixture of Pseudomonas sp and Bacillus megaterium native bacteria. Bioreactors consist of filled columns with contaminated ore containing 100 ppm of total cyanide. In the biodegradation tests a mixture of bacteria was inoculated into the biodegrading solution. Results of cyanide degradation show a similar asymptotic behavior in both the hybrid (opened system) and biodegradation (closed system) methods; however, for the same period of time (72 h) the permissible maximum levels (1-2 ppm of cyanide) are only attained in the closed system. While in the closed system the cyanide levels are reduced from 100 to 1.5 ppm, in the open system, cyanide decreases from 100 to 2.4 ppm.IntroductionOne of the most important tasks of mining industry is the treatment of the wastes generated in mining operations. Accordingly, industrial waste waters and ores represent a complex problem and a great challenge. In addition to ethic and communitarian considerations, there are laws that prohibit or regulate the contamination of water and air. Moreover, they establish that the restoration of wastes must be considered as a necessary operation cost [1]. Currently this important problem is being addressed by the mining and metallurgical industries using different approaches; mainly they are focusing on the treatment of waste waters and ores generated by the leaching process in which cyanide is used as a leaching agent for the recovery of precious metals as gold and silver. Cyanides have toxic characteristics and thus negatively impact the environment when they are discharged to the ground without previous treatment. While there are some processes in current use there are others that have only been proposed and that allow cyanide degradation, transformation to less toxic compounds and/or the complete elimination of cyanide. The second group includes a variety of techniques that use natural, chemical and biological treatments. Natural treatments consist of the passive abandoning of the heap and of its washing with water. Since these processes are slow and generate great volumes of water partially contaminated, then other alternatives should be considered."

Jan 1, 2008

By Guo Xian Jian

In this paper, an alternative process to recover the value metals from polymetallic gold ore by FeCh leaching was proposed. In the process, gold was recovered by direct cyanidation from the leaching residue, the isolative electrolyte in chloride solution was selected to recover lead, the cementation with copper powder was used to recover silver and the solvent extracting was applied to recover copper and zinc. The total recovery of gold, lead, copper, silver and zinc in the process is 90.8%,96.05%,84.3%,81.98% and 54% to the bullion of gold, lead and silver and sulfate of copper and zinc, respectively. The process conditions selected for FeCh leaching are the temperature of 104°C, leaching time of 6 hours, Fe3+ content of 140 g/l and stoichiometry of FeCl3.

Jan 1, 1996

By J. E. Jacoby

Scrap recycling has become an increasingly important source of metal units for the aluminum industry during the past 25 years. Aluminum scrap from the manufacture and recycling of cans, automobiles, buildings and other products has created an industry that melts these products and delivers the metal in molten or sow form to companies that make cast parts or fabricated products This rapidly developing recycling industry has contributed a large number of severe (Force 3) molten aluminum explosions (25) with associated fatalities (19) to the Aluminum Association data accumulated during the past nineteen years. The explosions that occurred in recyclers plants represent 17% of the total explosions, 33% of the Force 3 explosions and 37% of the fatalities reported. These explosions can be prevented! This paper will identify causes of these explosions and procedures that can be used to prevent them.

Jan 1, 2000

By Jae-Woo Ahn

Waste acids containing phosphoric, acetic, nitric and hydrofluoric acid were produced during the etching process of liquid crystal display and semiconductor manufacture. In recent years, the attention on the treatment of industrial waste acids has been increased considerably according to the reinforcement of the environmental regulations as well as the implementation of the economic considerations about the waste acids. Fundamental studies on the separation and regeneration of the mixed waste acids were conducted using Cyanex 923, Tri-octyle phosphate and 2-Ethylhexyl alcohol as an extractant by solvent extraction. It is considered that the extraction of liquid crystal display waste acids with Cyanex 923 and Tri-octyle phosphate, semiconductor waste acids with 2-Ethylhexylalcohol is applicable for the separation and recovery of acid. Finally, the acceptable recycling process from the multi-component waste etching acids was proposed.

Jan 1, 2006

By Fatma Arslan

Alada (Kayseri-Turkey) lead-zinc sulfide-oxide ores contain 10.17% Pb, 10.98 %Zn, 164 g/t Cd and 57 g/t Ag. During the laboratory scale flotation tests of these ores, it was found that almost all zinc was remained in the tailings that contain 12.31% Zn, 1.35%Pb, 198.3 g/t Cd, and 22.3%Fe. Three different methods were studied such as basic (NaOH) leaching, roasting+acidic (H2SO4) leaching and direct acidic (H2SO4) leaching for recovering metals that these tailings contain. In the direct acidic leaching, which gave the best results, dissolution efficiencies of 91.5% zinc, 78.2% cadmium, and 14.3% iron were reached at the optimum leaching conditions while Pb remained in the leach residues and the acid consumption was 422.3 kg/ton of tailings.

Jan 1, 2006

By Giovanni Principi

The activity of the ?Hydrogen Group? of Padova University, addressed to the study of materials for solid state hydrogen storage, is illustrated. Various Mg-based materials have been considered and are being studied: a) MgH2 and 0.5% mol Nb2O5 mixture ball milled under argon atmosphere; b) Mg-Ni-Fe intermetallic compounds prepared by short time ball milling of ribbons obtained by melt spinning and by long time ball milling of a mixture of MgH2, Ni and Fe powders; c) MgH2 ball milled in argon with Mm-Ni-Al (Mm = La-rich mishmetal) and Zr-Cr-Fe catalyst alloys. All the samples have been structurally characterized by X-ray diffraction (Rietveld refinement) before and after hydrogen absorption/desorption cycling and tested with a Sievert apparatus as regarding their thermodynamic and kinetic properties.

Jan 1, 2006

By Y. Mori, K. Kawanaka

The permeability changes during the sintering of the feed for the Imperial Smelting Process (ISP) were investigated using an experimental sintering pot, as well as with a mathematical model. The results obtained were as follows. The blowing resistance in the sintering bed changes as the sintering reaction proceeds. It increases at the beginning of the reaction when the temperature of the bed is still low. Then it decreases as the reaction continues, accompanied by an increase of the bed temperature. The increase of the blowing resistance in the bed during the sintering process mainly occurred in the drying zone, and was comparatively small in the reaction and cooling zones. Based on Erugen's equation, the change of the permeability during sintering is explained by the decrease of the apparent fractional void volume in the drying zone of the bed.

Jan 1, 2000

By Jack A. Simon

My remarks are directed at relating some of the mineralogical approaches mentioned in the preceding presentations to emerging energy issues. The assembling of this symposium on process mineralogy attests to the growing concern for energy development from the non-petroleum mineral fuels and the unconventional petroleum fuels. A report in 1979, prepared under the auspices of the National Research Council/National Academy, of Sciences, was published in two parts and dealt with "Redistribution of Accessory Elements in Mining and Mineral Processing." This report rather comprehensively considers broad aspects of minerals associated with the solid fuels considered in this symposium and focuses attention on some problems of process mineralogy relative to these fuels. Papers have dealt with coal, oil shale, tar sands, and uranium minerals. Problems associated with mining, processing, and use of these materials have significant differences, but also have some factors in common relative to the subject of this symposium.

Jan 1, 1981

By Guillermo J. Román

The precipitation of copper and zinc as cements from a copper alloys' spent pickling solution has been studied at laboratory and pilot scale, with the objective of designing an economic process to recover both metals and render a solution to be either recycled to the pickling process or treated in a standard fashion and produce a non-hazardous sludge. The sulfuric acid spent pickling solution already containing copper and zinc was used first to dissolve another solid residue originated in the copper alloys foundry to neutralize part of the acidity. The resulting enriched solution was treated separately with two reductants,; sodium borohydride and iron powder varying pH and excess of reductant under constant agitation. Under the best conditions, precipitation of over 95 percent of zinc and copper was achieved together with the reduction of lead and cadmium contents respectively. A process for the combined residues treatment is proposed.

Jan 1, 1995

By F. Tailoka

In order to decrease the voltage required for electrorefining, a recessed electrode cell has been developed in which the anode and cathode have recesses machined into their faces. The anode and cathode plates are separated by a thin refractory cloth and the cell is filled with fused salt. Bismuth containing 10 to 90 % lead with copper and silver as minor impurities has been electrorefmed at a current density of 10,000 to 20,000 Am-2. The cell voltage was between 285 and 635 millivolts and the bismuth was refined to a purity of 99.9 %. Flow patterns were observed in a room temperature model of the recessed channel cell using water and mercury to simulate molten metal and the fused salt electrolyte. The flow in the electrode recesses is characterized by discrete droplets when the liquid flow rate is low and thin streams and rivulets at higher flow rates.

Jan 1, 1995