Search Documents

By Kuniaki Murase, Tetsuji Hirato, Yasuhiro Awakura

"Electrodeposition of CdTe was studied using aqueous ammonia-alkaline electrolytic baths in which Cd11-and Te1V-ions are dissolving as Cd11(NH3)/+ and Te1vol-ions, respectively. Ca-thodic polarization curves of the baths suggest the presence of strong interaction between the Cd11-and Te1V-ions; electrodeposition of tellurium is inhibited by the presence of Cd(NH3)/+ ions. The interaction makes it possible to electrodeposit CdTe films with stoichiometric composition. Polycrystalline CdTe thin film of about 1 µm thickness was electrodeposited at 343 K from ammonia-alkaline solutions (pH= 10.7) containing TeO32-(<20 mmol dm-3) and Cd(NH3)/+ ( < 60 mmol dm-3) ions. Increasing Cd(NH3)/42+/TeO32- mole ratio or decreasing total concentration of ammonia/ammonium-ion gave flat and smooth crystalline CdTe deposits at constant cathode potential-0.70 to -0.30 V vs SHE at 343 K.IntroductionCadmium telluride (CdTe) is well-known as a compound semiconductor whose band gap, i.e. 1.44 eV, is suitable for solar energy conversion with a photovoltaic cell. Various methods, such as CVD (chemical vapor deposition) and electrodeposition, of preparing CdTe thin films for solar cells have been investigated.Acidic sulfate solutions with a pH of 1-2 are usually employed for CdTe processing by electrodeposition.1-3) The electrodeposition of compound semiconductors is usually achieved (i) at a higher cathode potential than the redox potential of less-noble species, can in this case, and (ii) under the condition of diffusion-limiting current of a more noble species, Te1Y.4) There-fore, a suitable CdII/TeIV concentration ratio in the acidic electrolytic baths, resulting in the deposition of stoichiometric CdTe, is determined by the diffusion-limiting current density of TeIV- reduction, i.e. the concentration of HTeIVO2+ · Since the solubility ofTe1v species HTeIVO2+ in the acidic solutions is quite low, the rate at which CdTe is deposited from the acidic solutions is extremely slow."

Jan 1, 1998

By Richard D. Hagni

An enhanced Interest in pyrometallurgical dusts has recently emerged due to increased world-wide environmental concerns. Mineralogical study of dusts samples from lead sinter plants. lead smelters, and secondary steel mill electric arc furnaces has shown that they can be readily studied by reflected light microscopy. These dusts typically are composed of small particles sufficiently large that their mineralogical identification and characterization can be conducted under the reflecting light microscope. Scanning electron microscope-energy dispersive spectroscopic analysis (SEM-EDS) has been used to confirm optical identifications and chemical compositions. The sinter and blast furnace dusts at the Doe Run Smelter at Herculaneum, Missouri are commonly about 20-150 11m. They consist predominantly of galena, chalcopyrite, sinter. slag. coke. and particles. Dusts from remote sampling sites 112-1 mile from the lead smelter are composed of similar particles and abundant fine-grained particles, less than 10 um. of locally derived calcium-aluminum silicates. Electric arc furnace (EAF) dusts are mostly spherical and less than 10 11m. They consist predominantly of iron oxides (magnetite. franklinite. jacobsite and solid solutions of these spinels), zincite. and calcium-iron silicate glass, together with smaller amounts of hematite. sylvite. coke and metallic iron. Reflected light microscopy is rapid provides mineralogical data on individual grains within dust particles. and allows direct observations of textural intergrowths in pyrometallurgical dust particles.

Jan 1, 1991

By Masafumi Maeda

Our aim in this project was to develop a new copper refining technology utilizing pyrometallurgical treatment and a raw materials preparation technique. In the recycling process; raw material is not an idealized concentrate of copper sulfide but is composed of various types of scrap, industrial wastes such as sludge, ash and slag, and municipal wastes. Since we cannot expect oxidation heat in this process as in sulfide smelting, organic materials are viewed as an alternative energy source. Quality of the copper produced is targeted as 99.99% and an intermediate grade will also be marketable. To benefit the plant, rare metals and other nonferrous metals will also be recovered The overall system is described in this paper, specific topics outlined and preliminary research presented. Current Japanese technology for recycling copper based materials is briefly reviewed.

Jan 1, 1995

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 H. Eccles

BNFL, an internationally acclaimed company noted for its nuclear fuel cycle services and waste management technologies, collaborated with Viridian BioProcessing Ltd, a small company acknowledged for developing environmental biological processes, and an internationally recognised professor of biological sciences, to develop an unique bioremediation process for treating toxic, heavy metal contaminated land. This paper describes the process, with particular reference to the problem and scope of land contamination with toxic, heavy metals and the current available technologies. The process technologies are based on using indigenous, soil micro-organisms which can be stimulated to produce acid or sulphide ions to mobilise or precipitate the heavy metals respectively. Laboratory studies have indicated metal removal efficiencies of greater than 90 % can be achieved, whilst recovery efficiencies from the metal loaded leachate are even higher at approximately 95%.

Jan 1, 1996

By D. Morin

A general study of gold refractory arsenopyrite-pyrite concentrate bioleaching has been carried out including two continuous bioleach testworks at different sizes, namely one at a laboratory scale with a 100 I unit at a 2 kg/d dry solid flowrate and the other at a pilot scale at a 100 kg/d dry solid flowrate. Both tests show a 80% bioleaching of arsenopyrite in about four days of treatment and with the same kinetic. Pyrrhotite is attacked at the earlier stage of the bioleaching but pyrite remains unaffected. The weak potential of oxidation associated with the decomposition of arsenopyrite and the abundance of arsenite leads to a high grade of elemental sulfur in the bioresidue which consumes the major part of the cyanide during the gold recovery. Furthermore. the arsenite and ferrous produced in solution have to be oxidized to obtain a stable precipitate in the waste products and as outlined in previous works of other authors on this subject the addition of iron to obtain a Fe/As molar ratio at least above 3 is necessary. The agitation equipment used in the pilot unit allowed an optimization study calculation for scaling-up the design and power requirements of an industrial installation. For the pretreatment of a gold refractory As high-graded concentrate the reagent cost has the greatest part in the operating cost of the biooxidation step due to the necessary retreatment of the biosolution. In that conditions the power cost is quite marginal. actually it is significant for the treatment of pure pyrite.

Jan 1, 1991

By R. Padilla

A thermogravimetric study has been conducted to follow the decomposition and volatilization of arsenic from enargite concentrate in nitrogen and slightly oxidizing atmospheres. Temperature has a large effect on the rate of volatilization of arsenic. Fractional volatilization of arsenic as high as 98% were obtained in less than 60 min at 650°C in nitrogen atmosphere, while in slightly oxidizing atmosphere the same volatilization could be achieved in 30 min. It was found that arsenic volatilizes as sulfide in nitrogen atmosphere and as 4xture of sulfide and oxide in atmospheres containing 1% oxygen. By using the pore blocking and the first order kinetic models, apparent activation energies of 213 and 200 kJ/mol for the temperature range of 780 - 900 K and 205 and 184 kJ/mol for the temperature range of 900 - 985 K were determined for enargite and copper concentrate, respectively.

Jan 1, 1997

By Milorad Cirkovic

Kinetics of copper concentrate oxidation in roasting processes in a fluidized bed reactor has been studied at temperatures between 600°C and 720°C using particles of 0.038 to 2.5 mm in average size. The analysis of composition of samples has been done by chemical methods. Phase composition has been determined by Siemens X-ray equipment with Cu anticathode and Ni filters at a voltage of 40 kV and a current of 18 mA. The content of sulphur has decreased from 33.23 to 19.02 mass percent with the increase of temperature, but the content of Fe304 has increased from 0.15 to 17.14 mass percent. The new mechanism of copper concentrate oxidation in a fluidized bed reactor is proposed in this study. It has been shown from the mathematical model that the velocity of oxidation of copper concentrate between 600°C and 720°C is virtually controlled by the rate of diffusion of 02 through the layer of reaction product.

Jan 1, 1999

By Cesar Garban

The samples of the washings are characterized of the ore for physical, chemical and metalurgical properties for representivity. the optimum values are determined for the recuperation of gold of the washings of the gold ore from the zone El Callao, Venezuela by acidic solutions of thiourea of the following parameters: Ph , contact time, composition of the liquid mixture, ratio of solid to liquid, grade of liberation, in an apparatus designed for contacting solid powder of the mineral with liquid solution of thiourea mantained in suspension by bubles of compressed air. The experimental results showed that the velocity of lixivation in primier time of (20) minutes is rapid and practically 2/3 part of the reaction is completed. For experimental design of parameters, the optimum conditions of recuperation of gold determind in this experimental investigation are:

Jan 1, 1999

By S. Raghavan

The thermodynamic activities of MgO in the solid solutions that can exist in the system NiO-Mg0-Zn0 are determined by measuring the EMF of the cell: O2 (g), Pt / MgO, MgF2 // MgF2 // x MgO + yNiO + (1-x-y)ZnO / Pt, O2 (g) / MgF2 in the temperature range 1190-1237 K. Equilibrium phases were prepared along the quasi- binary lines MgO/NiO = 0.1765,0.3333, 1.0,3.0 and 5.667 with the ZnO contents being 0.1, 0.2, 0.25, 0.35, 0.5, 0.75 and 0.9. The crystal structures of the phases were identified by X-ray diffraction. Results obtained so far show that a single phase MgO-rich cubic solid solution exists upto 0.2 ZnO content and for compositions above 0.25 ZnO, a second ZnO rich wurtzite phase forms in addition. Activity measurements show that for low MgO and ZnO contents, the MgO activities exhibit ideal to slight positive deviation from ideality and at higher MgO contents, a negative deviation is shown. Further studies are in progress.

Jan 1, 1993

By William Petruk

An investigation was conducted to determine whether mineral liberation data obtained by one image analysis technique are the same as data obtained by another image analysis technique. The liberated vs non-liberated, volume % and weight % techniques for measuring mineral liberations by image analysis were tested. The results show significant differences between the values obtained by the different techniques. The lowest liberation values were obtained by the liberated vs non-liberated technique and highest by the weight % technique. It is interpreted that the weight % technique produces the most realistic results. The weight % technique also produces data that can define mineral associations for the unliberated grains. These include (1) mineral quantities in particles that contain different amounts of unliberated mineral, (2) mineral quantities in particles that have different size ranges, and (3) mineral quantities and degrees of liberation for specific minerals in particles of different size ranges.

Jan 1, 1996

By Ernest D. Mast

Noranda&apos;s Altonorte custom smelter, located in the 2nd region of Chile, 20 kilometres southeast of the city of Antofagasta, started operations in 1993. Presently, 1150 tonnes per day of new feed are smelted with an 85% sulphur capture. An oxy-fuel reverberatory furnace produces a 48%-55% copper matte that is treated in 13 ft. x 36 ft. (3..96m x 10.97m) Peirce-Smith converters (two hot and one blowing). Up to thirty percent of the new concentrate is smelted via dry concentrate injection into the converters. This paper reviews the development of the concentrate drying and injection system, and oxygen enrichment at Altonorte from start-up in 1995 to the present time. The relationship between oxygen enrichment and concentrate injection is reviewed from a theoretical and practical standpoint. Concentrate injection has improved the smelter&apos;s productivity and added flexibility to the operations. Due to the relatively high matte grades and the subsequent short converting times, maintaining consistent operations was difficult at times and the smelter has gone through a learning curve. Plant operating results and experiences are presented on the impact of concentrate injection in relation to: feed treatment, blowing times, revert generation, slag quality and refractory wear.

Jan 1, 1999

By Rolando Campos

Until 1970, the Caletones Smelter of CODELCO-CHILE, División El Teniente, operated under the conventional pyrometallurgical process used by most of copper smelters. The annual copper production varied around 165.000 tons. The failure in the commissioning of the "oxygen smelting" technology in Peirce- Smith converters (1970-1972), forced further introduction of transcendental changes in the Caletones smelter operating scheme. Implemented technological innovations were based on wide studies and research works performed by División El Teniente. This paper presents a summary of technological modifications introduced, their impact on production and energetic performances, and short and medium terms improvement plans.

Jan 1, 1993

By Yong J. Kim, J. M. Park

"Solid/melt interface shape during continuous casting process has a strong influence on the resulting microstructure of the ingot. The interface shape is primarily governed by the heat flow condition between the molten metal and mold (or container). The roll of the microstructural transition resulting from various solid/melt interface shapes is discussed using the Sn-22.6wt%Pb alloy. Three different types of mold such as cold mold, resistantly heated mold, and electromagnetically heated mold were used to generate those interfaces having different curvatures. Experimental measurements of complete temperature profile along the axis and surface of the ingot during downward continuous casting are presented to determine the solid/melt interface geometry. The results provide an explanation of the ingot property with emphasis on microstructure.IntroductionA large scale of continuous casting process of alloys often has a rather deep V channel type of solid/melt interface resulting from a limited heat flow condition. As a result, the deep V type solid/melt interface shape entraps defects such as pores and inclusions and also creates canter segregation. In order to reduce the defects concentration, electromagnetic stirring(EMS) mechanism has been applied to the melt in the channel[l]. Speith and Bungeroth introduced first experimental EMS device to the continuous caster in 1952.[2] Today, with wide ranges of benefit, a large variety of such technique is available. Electromagnetic field on the melt can be divided into three aspects. First, eddy current is induced on the metal surface by alternating magnetic field with high frequency, which results in heating the metal. Second, electromagnetic body force which is generated by the magnetic field and the eddy current reduces the melt pressure on mold or support the melt not to contact with the mold[3,4,5]. This force is used for electromagnetic casting process(EMC). Finally, it causes stirring in the melt. Many research efforts have been done on the EMC process to improve surface quality of slab[6] and control meniscus shape where three phases such as melt, solidified metal, and mold powder coexist[7,8]. However, the eddy current heating effect on the surface of the ingot was less considered. It is worth noting that induced eddy current on the surface of slab melts the solidified shell and thus changes the heat flow condition between the mold and melt. Mold heating effect was first proposed by A. Ohno[9] and its processing conditions were identified in details[ 10, 11]. The so-called Ohno process is based on the fact that by keeping the mold temperature slightly above the melting temperature of the liquid, no grain can be nucleated on the mold wall[12]."

Jan 1, 1998

By G. S. Hill

A large amount of the stereological error associated with liberation studies can he eliminated by assessing areas instead of linear intercepts. The presentation of a simple geometrical model as a stereological &apos;worst case&apos; allows calculation of the worst possible grade/recovery curve for a given assemblage of areas. The true results are expected to lie in the window between this worst case and the hest possible case, represented by uncorrected data. The width of this window typically corresponds to an error margin of about 5% grade at a given recovery. An indication of where the data lies within the range of possible grade/recovery results may he obtained from a qualitative analysis of the locked section complexity. Assemblages consisting of texturally complex locked sections (ie. containing many mineral nuclei) are likely to exhibit minimal stereological bias and therefore will tend to lie close to the uncorrected side of the grade/recovery window.

Jan 11, 2011

By C. M. F. Vieira

The main characteristics and physical and mechanical properties of clays from the county of Campos dos Goytacazes, located at the northern part of the State of Rio de Janeiro, Brazil, are presented. The characterization included mineralogical composition, chemical composition and particle size distribution. The properties related to water absorption, linear shrinkage and flexural rupture strength were obtained in samples that were prepared by 20 MPa uniaxial pressing and fired at 950 and 1100oC. The results showed that the clays are predominantly kaolinitic with high percentage of clay minerals. The kaolinitic structure associated with a small amount of fluxes confers a refractory behavior which makes difficult the sinterization and impairs the ceramic consolidation.

Jan 1, 2009

By B. J. Jody

Each year, about 11 million tons of metals (ferrous and nonferrous) are recovered in the U.S. from about 10 million discarded automobiles. The recovered metals account for about 75% of the total weight of the discarded vehicles. The balance of the material or shredder residue, which amounts to about 3 million tons annually, is currently landfilled. The residue contains a diversity of potentially recyclable materials, including polyurethane foams, iron oxides, and certain thermoplastics. This paper discusses a process under development at Argonne National Laboratory to separate and recover the recyclable materials from this waste stream. The process consists essentially of two- stages. First, a physical separation is used to recover the foams and the metal oxides, followed by a chemical process to extract certain thermoplastics. The status of the technology is discussed, and the process economics are reviewed.

Jan 1, 1994

By Kenneth L. Nash

The control of solubility of waste actinide ions, by conversion to highly insoluble mineral phases has been demonstrated in the laboratory. Actinide metal ions are removed from neutral pH solutions by a combined ion exchange-decomposition-mineralization process based on the application of the naturally-occurring hydrolytically unstable.polyphosphate organic compound phytic acid.

Jan 1, 1999

By Samantha Moodley, Rauf Hurman Eric, Cevat Kucukkaragoz, Aditya Kale

"Two titania slags, rutile and synthetic rutile were chlorinated with petroleum coke and CO in a small bubbling fluidized bed reactor. The study aims to identify differences in chlorination mechanism, compare conversion rates, blowover and the chlorination of impurities for the various titania feedstocks at different temperatures.Chlorination rates were highest at 1000ºC; rutile chlorination significantly increases as temperature increases from 800ºC to 1000ºC. At 1000ºC, synthetic rutile had the highest chlorination conversion rate; this was followed by Slag B which in turn was more reactive than Slag A and rutile. The mechanism for slag, synthetic rutile (SR) and rutile chlorination differs. Synthetic rutile feed is porous, providing a larger surface area for the chlorination reaction, hence the highest conversion rates was attained. Titania slag becomes porous with the initial chlorination of FeO and MnO whilst rutile remains solid. As the porosity of slag particles increases so does its tendency to be elutriated. Ti2O3 is oxidized within the early stages of chlorination during the chlorination of FeO and MnO. Ti2O3 not oxidized is then rapidly chlorinated.IntroductionTitanium dioxide (TiO2) is the most common compound of titanium, about 95 - 98% of extracted titanium minerals is processed into TiO2 white pigment [1]. Two processing routes exist for the production of TiO2 pigments, i.e., sulphate and chloride based processes. In the chloride process, titania feedstock is fed to a fluidized bed reactor together with reductant and chlorine gas. A temperature of 1000 - 1300ºC is maintained in the reaction zone and apart from silica, zirconia, uranium and thorium, virtually all the metal oxides in the feed are converted to their respective chlorides [2]. Chlorine is recovered and recycled back to the reactor."

Jan 1, 2012

By F. E. Wagner, L. J. Cabri, Y. G. Safonov, N. S. Bortnikov, A. D. Genkin, J. Friedl, G. N. Gamyanin

"A multidisciplinary investigation (including INAA, SIMS, EPMA, and Mossbauer Spectroscopy) was used to characterize gold in four of the largest Siberian mesothermal sulfide gold deposits. These are the Olympiada (""'750 metric tons gold) and Veduga (estimated at 75-100 metric tons gold) deposits in the Enisei Mountain Range and the Nezhdaninskoye (z500 metric tons gold) and Sentachan deposits in the Verchoyansk-Kolyma area. It was found that some of the mineralization is refractory in all four deposits, largely due to the occurrence of ""invisible"" gold in arsenopyrite as well as within pyrite, but with a lesser concentration. The gold concentration and its distribution varies considerably both within and between arsenopyrite grains, with implications for processing options such as heap leaching. The ore most likely to be amenable to heap leaching is the oxidized ore of the #4 orebody of the Olympiada deposit, but further quantitative mineralogical investigations are recommended for this orebody's sulfide ore and for the ores of the Nezhdaninskoye deposit. Following a full mineralogical characterization, it is possible that economic viability will depend on a combination of pre-concentration with or without pre-treatment, followed by heap leaching of some tailings products.Acknowledgements· The Russian authors performed this study under an ""Eco res"" Project which was financially supported by the Ministry of Science and New Technology of the Russian Federation. C.J. Stanley wishes to thank John Spratt and Terry Williams for help with EPMA. F.E. Wagner acknowledges the Deutsche Forschungsgemeinschaft for a grant supporting the Mossbauer studies. L.J. Cabri is grateful to the following: M. Beaulne, D. Carson and J.H.G. Laflamme for technical support, K.E. Haque for technical comments, and D.M. Hausen and W. Petruk for editorial suggestions."

Jan 1, 1997