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By R. Padilla

In most of the Chilean copper and gold concentrates, arsenic is present mainly as enargite, Cu3AsS4, which at the conventional roasting or smelting temperatures decomposes liberating arsenic as gaseous compounds. The objective of this investigation was to study the decomposition reaction of enargite in an inert atmosphere in the range of 500 °C - 750°C. The results obtained indicated that the decomposition begins at about 525 °C. Two distinct regions in the temperature dependence of the decomposition rate were observed: a low temperature region between 525 °C to 650°C and a high temperature region between 650 °C to 725 °C. The X-ray diffraction analysis suggests that the decomposition of enargite occurs through the formation of intermediate tenantite, according to the following sequential reactions: 4Cu3AsS4(s) ? Cu12 As4S13(s)+ 3/2S2(g) Cu12 AS4S13(s) ? 6Cu2S(s) + 2As2S3(g) + 1/2S2(g) The decomposition kinetics was analyzed by using the model for a topochemical reaction of spherical particles: 1-(1-X) 1/3 = kt, which represented well the data. Apparent activation energies of 113 kJ/mol and 60.5 kJ/mol were found for the low and high temperature regions, respectively.

Jan 1, 1999

By C. E. Hunt

Since the turn of the century, copper-nickel sulphide ores have been processed at the Sudbury, Ontario operations of INCO Limited, currently the largest integrated mining, milling, smelting and refining complex in the free world. Through the years operational, ecomomic, social and legislative changes have dictated the need for research and development directed at mitigating the impact of existing operations on the surrounding natural environment and also the reclamation of areas affected by earlier mining activities. Approximately one hundred years of mining history and the current annual processing of some 12 million tons of ore presents significant challenges with respect to waste disposal, liquid effluent treatment and land reclamation, particularly in light of rapidly evolving environmental regulations' and controls within the Province of Ontario.

Jan 1, 1992

By Khoo Khyou Pin, Yoshiyuki Funaki, Hirotsugu Takeuchi, Ryoichi Urao, Naotatsu Asahi

"Steel is used to be ion carburized with mixing gas of methane and hydrogen. In carburizing, carbon in the methane decomposes and deposits on the steel by plasma, so methane gas flow may influence on ion carburizing of the steel. An apparatus in which works can transfer preheating, ion-carburizing and diffusion treating zones continuously was made for effective carburizing of steel. The gases were flown into above three zones with three different gas inlets. The hardness and microstructure of the works were investigated after ion carburizing and quenching. The steel is carburized deeper near the carburizing gas flow nozzle of the inlet than far from the nozzle. Hard surface layer fom1ed by quenching of ion-carburized steel.IntroductionGas carburizing is used for a surface hardening treatment which decreases fatigue and wear of the industrial parts used in automobile, machines etc. Ion and vacuum carburizing have been developed recently and applied to some industrial parts of restrictive purposes. The ion carburizing treatment which uses hollow cathode discharge (HCD ion-carburizing) is superior in energy saving, resource saving, environmental cleanness to the other carburizing treatment. Specially, carburizing energy can be saved in HCD ion-carburizing, because highly heated zone can be restricted in the range between work and subsidiary cathode where hollow cathode discharge arises, and the work is carburized in shorter tin1e in HCD ion carburizing method than other carburizing methods. Three treatments of preheating, carburizing methods and carbon potential controlling by hollow cathode discharge tried to be carried out in one continuous transferring series to carburize works more effectively, so the HCD ion-carburizing apparatus with continuous transferring system was made and gears of works were HCD ion-carburized in continuous transferring. The works were rotated themselves to get homogeneous carburizing by continuous transferring in glow of hollow cathode discharge."

Jan 1, 2000

By P. R. Seidl, R. C. C. Ribeiro, J. C. G. Correia

"More than 95% of asphalt pavement materials consist of aggregates. The highway and construction industries consume a huge amount of aggregates annually causing considerable energy and environmental losses. The aggregates are usually produced from neighborhood aggregate quarries or form natural aggregate sources. The use of marble and granite wastes from quarries as aggregates might help meet the increasing demands and slow down any detrimental effects on the environment. Chemical and physical results showed that the use of marble and granite wastes from quarries in the asphalt production is quite fusible. Consequently, granite sawmills would perform a clean technology. This technology would also have an economical impact by not spending on basalt extraction.IntroductionThe granite fines generated from sawmills of ornamental rocks comes as a great problem and it lacks undeletable solutions. This problem involves the preservation of the environmental and constitutes one of the subjects more critical the point of view of social beneficiation of the population. The Cachoeiro de Itapemirim County, Espírito Santo State, Brazil is an example, of this problem. In this area, the granite and marble fines generation is around 15.000 ton/year.The problems generated by these residues affect with more emphasis the animals, such as the cattle, which inhaled the water content fines of granite and this residue accumulate in their lungs. Other great problem observed is the sanded of the river and the reduction of aquatic life.This problem is beginning to be set out due to performance of Center of Mineral Technology (CETEM), and of several other organisms of Rio de Janeiro State, aiding the sawmills owner’s. This help consists of teaching the best procedure of discard the residues and studies for its use, for instance the production of mortars, tiles, bricks and road pavements [1]."

Jan 1, 2008

By Xinghua He, Shujing Zhu

"In this paper, the chemical composition, the content and the leachability of heavy metals in dredged sludge are tested and analyzed. It is shown that the leachability of Pb and Cr exceeds the leaching toxicity standard, and so the dredged sludge is considered as hazardous waste and must be solidified. The effect of solidifying the dredged sludge by the hydraulic ash-slag cementitious composites is studied, and it indicates that the heavy metals can be well immobilized if the mass fraction of the dredged sludge is appropriate. The heavy metals are immobilized within the hydraulic ash-slag cementitious composites hydration products through either physical fixation, substitution, deposition or adsorption mechanisms.IntroductionDredged sludge is classified as a hazardous waste because it usually contains concentrated heavy metals and chlorinated organic compounds, as well as soluble salts, and is also composed of very fine particles. Moreover, inorganic pollutants are typically associated with soluble compounds, which are, therefore, highly leachable from dredged sludge when dredged sludge is contacted by a liquid medium[l1. Thus, dredged sludge must be stabilized in order to reduce its environmental impact on the final disposal site. The frequent means of dredged sludge disposal used include(!) Chemical stabilization (2) acidic extractionChemical stabilization is translating mobile heavy metals into low dissolution and low toxicity form through chemical reaction. The commonly chemical medicaments are sodium hydroxide, soldium sulfide, thiourea, EDTA. But Zhao et al [ZJ found sodium hydroxide is not fit for Pb stabilization, the other three are effective, but the chemical properties of sodium sulfide are not stable, thiourea and EDTA are very expensive, and so it is very difficult to apply them. Moreover, because of the complexity of heavy metal conformation and dredged sludge composition, it is very difficult to find a cheap and prevalent stabilization medicament in point[31 ."

Jan 1, 2013

By Eduard Ouerra, Nuo Jin

"The use of polytetrafluoroethylene, PTFE, as a solid sorbent for elemental sulfur during pressure oxidation of chalcopyrite was investigated. The effects of agitation, PTFE particle size and lingin sulfonate addition were evaluated using leaching conditions that were otherwise similar to those employed in the CESL process. The effects of these factors and their interactions on chalcopyrite oxidation are explained in terms of interfacial forces and solid-solid interactions. Using relatively fine PTFE powder with vigorous agitation resulted in about 100% copper extraction in less than 90 minutes without the need for grinding of the flotation concentrate.IntroductionThe extraction of copper from sulfide ores has always been dominated by the conventional pyrometallurgical smelting process. Though much effort has been made to develop various hydrometallurgical processing routes, smelting remains as the dominant process, treating approximately 80% of the chalcopyrite concentrates worldwide [1]. However, some of recently emerged techniques for treating chalcopyrite through hydrometallurgical routes are showing results that are competitive with smelting in terms of economical feasibility. Representative methods include: Activox Process, CESL Process, Anglo/UBC Process, High Temperature Pressure Oxidation, and Bio-Oxidation. Among these, the CESL processes operate at a medium temperature range (typically 140-150GC) and oxygen pressure of 100 psi, with chloride as a catalyst, and reportedly achieve copper extractions of about 95% with a light regrinding of flotation concentrate to a p95 of 45 ìðé [2]. In spite of this satisfactory extraction result, the leach residues contain significant amounts of conglomerates which contain a small amount of unreacted concentrate [2], The conglomerations are formed because the elemental sulfur generated is liquid and sticky (melting point of sulfur being 119°C), and has a tendency to wet the sulfide mineral surface, a fact which inhibits the oxidation of the minerals. The overall process chemistry of the CESL process may be summarized as follows [3]:"

Jan 1, 2012

By Jincheng Hu, Honggang Zhong, Qijie Zhai, Congsen Wu, Cheng Zhang, Jingzheng Ye

"The influence of cooling intensity on the solidification structure and ferrite phase content of a new duplex stainless steel (DSS) was investigated by using a thermal simulation setup for continuous casting. The results showed that the characteristics of the solidification structure were similar to their industrial scale manufactured slabs, including chill zone, colunmar zone and equiaxed zone. And austenite morphologies were mainly primary and secondary Widmanstatten sideplates as well as intragranular Widmanstatten plates. In addition, it revealed that the ferrite content increased with an increasing distance from the chill surface and decreased at colunmar to equiaxed transition (CET) position, then the value remained relatively stable at equiaxed zone. Furthermore, the ferrite content presented the same trend with the cooling intensity ranging from 100 mL/min to 2000 mL/min with the values just varying in a slight range.IntroductionThe duplex stainless steel (DSS) is the kind of steel that ferrite phase and austenite phase occupy about 50% respectively, or the content of the fewer phase has to be more than 30% [l]. The success of modem duplex stainless steels is to a large degree due to their higher strength than austenitic stainless steels, higher toughness than ferritic stainless steels, good weldability and high resistance to stress corrosion cracking as well [2,3]. The cost of stainless steel production continues to soar in recent years due to the increasingly higher price of Cr. In order to decrease the production cost, a new type of duplex stainless steel was developed by Bao steel [4]. This newly developed duplex stainless steel had low Cr content compared with 2205 DSS, and was expected to be applied into automobile industry. However, this type of steel was still in the initial stage of development, and the influence of continuous casting process on its solidification process and structure was still unclear, which needed to be studied further. Several works published in literature presented the effect of continuous casting conditions on duplex stainless steel (DSS) 2205, 2304 [5,6]. It was discussed that the cooling intensity in the chill-side had little efficient influence on the phase transformation. In this paper, the effect of cooling intensity on the solidification structure and ferrite volume fraction of this DSS at a given cooling rate was investigated."

Jan 1, 2014

By Tong Zhilin

The reasons why the pits were formed on the cathode in the process of Ni electrowinning and the methods how to prevent these pits from forming are described. Some examples are presented. It has 'been proven that P507 and P204 present in the electrolyte can effectively prevent pits from forming on the cathode.

Jan 1, 1993

By Ulrich E. Klotz, Gemot Pottlacher, Shahid Mehmood

"Platinum alloys are frequently used in technical applications and in jewellery. Their thermophysical properties such as density, heat capacity, thermal conductivity and surface tension play an important role in casting processes and are required as input data for casting simulation. Scope of this work was to investigate these properties by different methods. Platinum and four alloys namely, Pt96Cu4, Pt68Cu32, Pt50Cu50 and Pt25Cu75 were investigated. Melting range and thermal expansion was measured at fem by DSC and dilatometry, respectively.At TU Graz wire shaped samples were investigated by an ohmic pulse heating technique. This technique allows the calculation of specific heat capacity and the temperature dependencies of electrical resistivity, enthalpy, and density of these alloys in the solid and liquid phase. Experimental results were compared with available literature and data from thermodynamic calculation using the SNOBl database and ThermoCalc.IntroductionPlatinum is a precious element and its alloys are commonly used in jewellery. But Platinum is much more difficult to cast then other jewellery elements like silver or gold, because of its high melting temperature, large shrinkage during freezing, low thermal conductivity, high surface tension, and high viscosity. As a result there arise problems during casting. Hence to resolve these difficulties a detailed study of thermophysical properties of solid and liquid platinum and its alloys is necessary for simulation and casting. The Platinum alloy samples were prepared by vacuum induction melting and casting into copper molds. Rods of 3 mm in diameter and a length of 80 mm were prepared and drawn to wires of 0.5 mm in diameter."

Jan 1, 2011

By Shubin Wang

Copper(II) and nickel(II) are often recovered from ammoniacal alkaline solutions by solvent extraction using hydroxyoxime extractants: both copper(II) and nickel(II) are extracted from ammoniacal alkaline solutions and, from the loaded organic phase, nickel(II) is selectively stripped with a dilute acid followed by copper(II) stripping with an acid of higher concentration. Since a small portion of ammonia is co-extracted with copper and nickel, the extracted ammonia should be scrubbed using a dilute acid before metal stripping. In the present study, a mechanistic model has been developed in order to support design and control of this process. The equilibrium distribution ratios of copper(II), nickel(II), and ammonia at 298 K using LIX® 84-I (active component, 2-hydroxy-5-nonylacetophenone oxime) as the extractant are successfully correlated by considering the relevant equilibria. Based on these results, quantitative prediction of equilibrium distribution ratios in the process has been made possible, and suitable conditions for the efficient separation of copper(II) and nickel(II) are discussed.

By Alicia Esther Ares, Carlos Enrique Schvezov, Alejandra Silvina Roman, Claudia Marcela Méndez

In this paper the structure of aluminum based alloys and their corrosion behavior by using different electrochemical techniques as characterization methods are considered. Currently, it becomes imperative to know the role of the Al2Cu against the susceptibility to corrosion of these alloys. The present work aims to studying the electrochemical behavior of aluminum base alloys with the following compositions: Al-1wt.%Cu, Al-4.5wt.%Cu and Al-15wt.%Cu (with different grain structures), in 1M NaCl solutions, at room temperature. Cyclic potentiodynamic polarization tests were performed and were found that the alloys with more than 1wt.%Cu in the matrix have an unstable behavior and without tendency to reach passivity. The equivalent circuits derived from electrochemical impedance spectroscopy technique (EIS) generally showed two capacitive contributions. The susceptibility to corrosion becomes a complex function, not only of copper concentration and structure, but also with interdendritic spacings and distribution of phases in the alloys.

Jan 1, 2015

By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340'C by the two probe method using an ultra high resistance meter. The k value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it mouutuniocally increased from 10-5 to10-4 A' 1 cm-1 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the K value. The k value increased with the increase of Na proportion in the melt. For a 10mol% Na doped sulfur melt it was as high as max ~30 A 1cm -1 above 180 C under the irradiation of of ultrasconics.

Jan 1, 2003

By Leonid N. Shekhter, Corby G. Anderson, Esra Cankaya-Yalcin, Daniel G. Gribbin, Joseph D. Lessard, Larry F. McHugh

"A new process for smelting copper, Looping Sulfide Oxidation™ (LSO™) significantly and positively alters the smelting energy balance. This process uses copper oxide in conjunction with air for the desulfurization of copper and chalcopyrite concentrates. Copper oxide is regenerated in a flash type furnace and then ""looped"" back for the oxidation of the copper concentrate. Heat and material balances show that the Looping Sulfide Oxidation™ process requires significantly lower net energy than conventional technology. This process produces anode copper and higher S02 content off-gases for efficient formation of sulfuric acid. Additionally, the process yields slags with lower copper solubility as compared to the conventional technology.IntroductionBased on the positive results from LSO™ investigations [1], further lab investigations into co=on sulfides and metal oxides were performed. It was discovered that chalcopyrite (CuFeS2) is oxidized with copper (II) oxide. In this reaction over 98.5% of sulfur was removed as S02, while a significantly improved energy balance was observed. This paper intends to analyze both the conventional flash smelting process and the newly developed Looping Sulfide Oxidation™ process, comparing heat and material balance results. LSO™ yields improvements to the energy footprint for copper, opening the door to new copper processing opportunities."

Jan 1, 2013

By Edita Vircikova

The best demonstrated available technology (BOAT) for the removal of dissolved arsenic and some heavy metals as reported by USEPA (Contaminants and Remedial Options at Metal Sites, Draft Report, August 1993) (1) is still the chemical precipitation. Coprecipitation with the excess of iron is usually practised because of the availability of iron at low/no cost and also in order to meet the stringent regulatory discharge limits. The arsenic is usually removed with iron because of its common occurence in the mined orebodies and the excellent adsorptive property of the precipitated hydrous ferric oxide compounds. There has been controversy, however, over the long-term stability of the arsenic-bearing ferrihydrite which is produced.

Jan 1, 1995

By In-Ho Chi

In copper metallization, resistivity of copper seed layer is very important since the thickness of seed layer is less than 200iun. Conventionally MOCVD has been used for this purpose however electroless copper plating is simple process and the resistivity of copper deposit is less than that of copper prepared by MOCVD. In this study eIectroless depositions of copper were conducted on different substrate to find optimum conditions of electroless copper plating for electronic applications. To find optimum conditions, the effects and selectivity of activation method on several substrates were investigated. The effects of copper bath composition on morphology were investigated. The effects of pH and stabilizer on deposition rate was investigated. The resistivity of copper with thickness was also measured.

Jan 1, 2001

By M. H. Lin, S. Kou

"Czochralski pulling has been a very widely used process for growing single crystals for electronic and optical applications. Dopant segregation can significantly degrade the quality and yield of single crystals. We have used the floating-crucible technique for segregation control in Czochralski pulling, our floating crucibles being unique in that the melt passageway is very long. As such, dopant back diffusion is suppressed, even when the cross-section of the melt passageway has to be relatively large to help the melt go through or when the pulling rate is very low. Single crystals of model materials K-doped NaN03 and Pb-doped Sn have been grown with very uniform dopant concentrations. IntroductionSingle crystals of electronic and optical materials are often doped with a small amount of impurities to develop required physical properties, e.g., P and B in Si for n-type and p-type semiconductors, respectively, and Nd in YAG lasers. Dopant segregation can result in nonuniform physical properties, thus degrading the quality and yield of the resultant crystals.Figure 1 is an illustration of the conventional Czochralski process for crystal growth. Several techniques have been developed to control dopant segregation in Czochralski pulling, including the push-pull technique (1,2), the drop-pull technique (3-7) and the floating-crucible technique (8-13). The first two techniques require precise sensing devices and feedback control systems to keep the feeding rate equal to the pulling rate. The last technique is simple since the feeding rate is automatically equal to the pulling rate."

Jan 1, 1994

By O. Chemezov, Yu Zaikov, A. Apisarov, A. Isakov

"Silicon deposits containing 99,9 wt.% of main component were obtained by SiO2 electrolysis from chloride-fluoride melts. The operating temperature was varied from 973 up to 1073 K. The conditions for obtaining crystalline fibrous micro- or nanodeposits were determined. The deposits were investigated by ESM methodIntroductionThere are large reserves of natural quartz of high purity in Russia. Processing of this raw material by electrolysis in molten salts produces silicon containing 99.9 weight percent of basic substance.[1]This method is less energy-consuming in comparison to existing methods for producing high purity silicon from gas phase.Another advantage of the electrolytic method for producing silicon from its oxide in molten salts is the possibility of production of high-purity silicon under air atmosphere. It dramatically reduces costs of the electrolytic cell construction, and the operating costs at electrolysis.On our opinion, the main advantage of the electrolytic production from SiO2 in molten salts is a unique opportunity to obtain micro-and nanostructures of silicon deposits. In particular, it is possible to obtain fibrous structures of silicon. The electrolytic method allows smoothly adjusting the thickness and length of silicon micro- and nano-wires by varying the cathode current density and temperature of the process."

Jan 1, 2012

By W. G. Davenport

Chapter 11 determined the combinations of industrial oxygen, oil and blast preheat that will steadily produce 65% Cu matte from pure chalcopyrite concentrate. It showed that the . combinations are described by a flat plane. It also showed that the minimum energy requirement for making 65% Cu matte occurs with maximum oxygen enrichment, zero oil and zero blast preheat. This chapter examines the, effect of matte grade on industrial oxygen, oil and preheat requirements.

Jan 1, 2001

By Toshihide Ito, Jie Liu, Takashi Nishiyama

"Human society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society. The increase pattern of supplemental energy is similar to that of mineral production throughout the world. Low positive and stable long-term increasing occurred before 1950, whereas they increased quickly after 1950, especially between 1950 and 1973. A substantial decline in· the growth of energy and mineral production began in 1973 and lasted until the early 1980s. Production of energy resources has recently begun to increase again at a high growth rate in the world. Observing the consumption trends of energy and key metals, it is clarified that increasing patterns can be thought in three stages.IntroductionHuman society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society [1-3]. Humphreys [4] described that both the non-ferrous metal consumption and the construction material consumption showed a similar trend dropping markedly in the UK over the period 1960-1992. On the other hand, per GDP (Gross Domestic Product) consumption, that is, the intensity of use of construction materials has declined sharply over the past 30 years, more so than the intensity of metal use in the USA [5]. Nishiyama [6] observed that increase pattern of supplemental energy is similar to that of mineral production throughout the world."

Jan 1, 2000

By Philip Thompson

"Carefully planned laboratory test programs provide valuable data regarding the amenability of low grade gold ores to heap leaching. The most common laboratory test is the column leach test. The overwhelming problem associated with this type of test is the limit on the test column height. Most laboratories use a three (3) meter (10 foot) high column as a standard test due to building ceiling limitations, sample size limitations, etc. This paper presents a case study in which an ore sample was tested in a 1.5 meter, a three meter, and a six meter high column to determine the effect of column height on the test results. Other important factors such as sample preparation protocol, preliminary bottle roll testing to determine appropriate crush size, column diameter requirements, and leach solution analyses, are also discussed.IntroductionColumn leach testing has been used for years by many laboratories to determine the amenability of low grade precious metals bearing ores to heap leaching. However, the test work can be compromised by poor planning, misinterpretation of results, and extrapolation of data beyond the reasonable boundaries of the experiment. Preliminary test work should be performed prior to column testing. This preliminary work provides valuable information regarding the response of the ore to cyanidation and aids in the design of the column tests.The sample should be screened into various size fractions prior to testing. The fractions are assayed to determine the gold content of each size fraction and of the overall sample. The most valuable preliminary test is the bottle roll cyanidation test which is usually performed on five kilograms of coarse sample in a large rolling bottle which can accept material up to 50 millimeters top size. The residue from this test is screened at different sizes to determine the distribution of unleached gold in the residue. Comparison of the gold distribution in the leach residue with the distribution of gold in the feed at the same size intervals provides an indication of the appropriate crush size for the sample. The overall gold extraction from the sample at the crush size tested is also determined from these data. Lime and cyanide requirements can also be estimated from this test. The viscosity of the bottle roll pulp and the size distribution of the feed and leach residue can also suggest whether agglomeration of the ore will be required prior to column testing. Ores which contain significant amounts of clays (greater than 5 percent) will generally require agglomeration to prevent plugging of the test column."

Jan 1, 1997