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By Nolberto Moreno Borjas

This paper outlines the detrimental impact that unblended ore can have on the Ni and Co recoveries and the ore slurry density with real data from the Caron low-pressure ammonia leaching process for the Punta Gorda ore. The author briefly discusses the reason for the decrease in slurry density that the process experiences. The lower metal recoveries in the process that are caused by the unblended ore chemical characteristics and variations are shown with a data base statistical analysis drawn from the results obtained from a pilot test, designed with different ore bypassed from the normal process flow and a similar ore from a similar metallurgical treatment. Keywords: Ni-Co Laterite, Caron Process, Ore Blending, Slurry Density, Metal Recovery

Jan 1, 2004

By Heinz Boeni, Daniel Ott, Uca Silva

"Latin America is facing a rapid increase in internet use. Penetration with electronic equipment is in some countries approaching the level of industrialized countries. There is an evident need to resolve the management of “end-of-life” computers and other electronic equipment. Several studies in Latin America assessed the increasing e-waste quantities and confirmed the importance of a sustainable e-waste management. This paper gives an overview on the status on e-waste management in Latin America, explains the challenges for establishing an e-waste management system in a developing country setting and highlights the social and economic potential and the possibilities of a regional approach.IntroductionGlobal ICT-Trade and generation of e-waste from ICTThe global production of electronic devices and particularly of Information and Communication Technologies (ICT) faces the biggest industrial expansion of the history: OECD figures show that global trade of ICT technologies has reached 7.7% of the gross world product by 2004, the major proportion accruing from China [1]. In 2006 an estimated 230 million computers and 1 billion cell phones have been sold worldwide which corresponds to a volume of 5’848’000 t [2]. As a consequence, Waste from Electrical and Electronic Equipment (WEEE), or e-waste, is by far the fastest growing waste component. It reaches more than 5% referred to Municipal Solid Waste and e-waste generation in developing countries according to UNEP is expected to triple by 2010 [2].According to the OECD e-waste is “any appliance using an electric power supply that has reached its end-of-life” [3]. The European WEEE directive [4] distinguishes 10 categories of ewaste: Big household appliances, Small Household Appliances, IT and Telecommunications Equipment, Consumer Equipment, Lighting Equipment, Electrical and Electronic Tools, Toys, Leisure and Sports Equipment, Medical devices, Monitoring and Control Instruments, and Automatic dispensers. In this paper e-waste and WEEE are used as synonyms. Focus will be laid on e-waste from IT equipment (IT-waste), corresponding to category 3 of the European WEEEDirective."

Jan 1, 2008

By Veronica Escobar

This paper presents results from a two month pilot evaluation of EMEW® technology at CODELCO Radomiro Tomic, in Chile. A prime focus in the test programme was to assess the technology?s capabilities to recover high quality copper from the Radomiro Tomic electrowinning tank house bleed stream. The EMEW® cell developed by Electrometals Technologies Ltd. tolerates substantially higher levels of contaminants than those found in conventional tankhouse, operating at high current densities while maintaining high cathode copper quality all the way down to low copper concentrations. To maintain high copper purity in a copper electrowinning (or electro-refining) tank house, a continuous bleed of solution must be taken from the tank house inventory to prevent build-up of contaminants, and resulting degradation in cathode quality. In an SX-EW operation, this bleed stream is normally recycled back to the solvent extraction circuit, but is occasionally sent to the raffinate pond to re-enter the leach circuit. Return of the bleed stream to the solvent extraction circuit creates a continually recycling load of copper in solution, which may reduce overall plant capacity and expansion potential. Return to the leach circuit has a similar effect, and methods to reduce its impact are always under consideration. The use of the EMEW® technology allows for direct and efficient recovery of near 100% of the contained copper instead of recycling. Tests were run at ambient temperature on bleed electrolyte using current densities which varied between 250 and 1100 amps per square meter, with copper concentrations between 38 and 1 g/l. A profile of maximum allowable current density with respect to concentration was developed, showing that high grade copper can be obtained at all levels of concentrations tested, by choosing an appropriate current density and electrolyte flow rate. The results of this programme show that the recirculating bleed electrolyte from an SX-EW operation can be converted into an expansion in copper production at a comparatively low investment cost.

Jan 1, 2003

By I. B. Scorzelli

The aim of this paper is to make a detailed mineralogical characterization of a typical brazilian xenotime and zircon from the Pitinga Mine using SEMIEDS techniques, On the other hand, superficial pretreatments with HCI, HN03 and HF were done to evaluate the modifications on surface compositions and the morphology of the particles for flotation purposes, The studies showed that both xenotime and zircon present very small inclusions of thorite; zircon is strongly metamictizated given rise to malacon. The HF pretreatment deeply affected the morphology of the particles as well as the surface properties in relation to flotation.

Jan 1, 1996

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 Takashi Nakamura, Kenji Oosumi, Kazuhisa Fujisawa, Takayuki Kogishi

"Recycling of used aluminum beverage cans(UBCs) is one of the important issues for aluminum manufacturer presently. The direct re-melting of UBCs shows two problems. One is a reduction in molten aluminum recovery and the other is a contamination of other metals such as Ti and Fe from paints. Both problems are caused by paints coated on the surfaces of aluminum cans. Removal technique of the paints, therefore, has been required. Although roasting and shot blast techniques have been developed, both were not successful in removing the paints effectively. A swell-peeling method has been applied to remove them using a methylene chloride solution with acids and it works very well. Small laboratory scale tests have been carried out to develop the commercial process and clarify the mechanism of the swell-peeling method in the present study.When the surface area of UBC is more than 10 cm2, peeling time is independent of the surface area, about 60 seconds, because swelling phenomenon is controlled by the penetration of the liquid through the fine pits on the surface of the paint. This is good for a commercial process. Peeling takes place when the swelling force generated by methylene chloride exceeds the adhesion force between the film and the surface of aluminum, that is weakened by the coexisting acid, especially halogenated acetic acid."

Jan 1, 2000

By Vinay Kumar, Jae-Chun Lee, Abhishek Kumar, Manis Kumar Jha

However, India is rich in ores and mineral, but E-waste recycling is necessary due to the report of national and international studies, which cautioned on the generation, treatment and accumulation of e-waste in India. Current data indicate that the total domestic e-waste generation including imports is around 382979 MT, however waste available for recycling and actually recycled are 144143 MT and 19000 MT, respectively. In which recycling by non-formal and formal sector are 95% and 5%, respectively. On the other hand, India has developed expertise in handling verities of metallic wastes in an organized and safe manner. The development of individual process or combined processes for handling the e-waste is underway. Eco- friendly and energy-saving processes are necessary to comply with stringent environmental regulations. The paper includes the recent trend of e-waste generation, recycling process and its future prospects particularly in India.

Jan 1, 2011

By Robert F. Jenkins, King G. Robertson

This paper presents a practical approach for utilizing a computer model to determine the mass balance for a typical UBC recycling complex - starting with raw materials input, through scrap preparation, delacquering, melting, alloy adjustment and casting. This model is especially concerned with metal unit losses throughout the recycling complex with emphasis on metal losses at the melting furnace. The model also addresses the application of hardener alloys, metallurgical salts, chlorine for demagging, and reagents for acid gas emissions control. Other issues addressed are dross generation, acid gas emissions and dirt and fines to landfill. One benefit of the model is the conversion of annual production objectives to hourly production rates and resource requirements taking into account production schedules, maintenance downtime, and operations inefficiencies.

Jan 1, 2000

By A. P. Paiva

Although the advantages of Solvent Extraction for separation/purification of relatively concentrated solutions are well known in Extractive Metallurgy, its use for the recovery of elements present in low levels only recently has been discussed, with particular attention devoted to precious metals. In this work, the extraction behaviour of Cyanex 471X towards silver, from an acidic chloride medium is reported, the extraction and stripping isotherms and related kinetic features analysed. Results on the selectivity of silver extraction against high contents of iron, copper and lead are discussed. Phosphine sulphide extractants are generally associated with solvation mechanisms: analysis of the extraction pathways along with the possibility of reaching a suitable loading in the organic phase are also presented.

Jan 1, 1993

By Myung Bae Kim, Yong Hack Lee, Woll Seung Lee

The Slag Fumer is the first Ausmelt furnace system adopted at the Onsan Refinery of Korea Zinc. This plant continuously treats the QSL lead smelting slag in the molten state. It has developed progressively since its first commissioning in October 1992 and has generated a confidence that it can produce an environmentally acceptable slag for use in cement manufacture and recover the zinc and lead in the slag as a fume oxide. This paper provides the operating experiences accumulated during the last eight years of operation, a summary of problems and solutions, and the current status of the operation.

Jan 1, 2000

By Gunther Schimmel

Ag exudation in four different alloys (Ag-Cd, Ag-Sn, Ag-Sn-In and Ag-Zn) is characterized. The amount of exuded material is correlated with the volume increase due to oxide formation in dependence of the alloy concentration and different densities of the oxide and matrix phases. It is shown that all four alloys show similar amounts of volume increases, but different amounts of exuded material. It is concluded that internal stresses due to the volume increase cannot be the dominant driving force for Ag exudation. A gradient in the chemical potential of Ag that originates from the O concentration gradient inherent to internal oxidation is suggested as driving force. The exudation behavior is thus governed by the variation of the activity of Ag in the Ag fcc phase in the Ag-Me-O system that differs between the alloying systems.

Jan 1, 2010

By J. G. Peacey, P. Hancock, R. -Q. Li

A pyrometallurgical process for the direct recovery of zinc from zinc concentrates and zinc/iron residues has been proposed and tested extensively by Noranda. The process consists of smelting bone-dry zinc containing materials (sulfide concentrates and secondary zinc/iron materials) in a molten iron oxysulfide bath to volatilize metallic zinc into a SC^-free offgas. Sulfur contained in the feed materials is fixed as an iron oxysulfide matte for disposal. Thus, this process not only is capable of treating zinc sulfide concentrates and secondary zinc materials simultaneously, but also eliminates the need of sulfuric acid production. Detailed thermodynamic analysis and experimental test work are described in this paper.

Jan 1, 2000

By Z. Zhang, Zongshu Zou, Nan Wang

"Thermodynamic calculation is applied to make an investigation on the equilibrium phase relations and liquids of CaO-SiO2-Al2O3-FeOx system for different temperatures. The calculated results with FactSage6.1 show that the effect of temperature on the the equilibrium phase relations and liquidus of CaO-SiO2-Al2O3-FeOx system and its sub-systems is appreciable. The liquid phase regions enlarge with increasing temperature from 1573K to 1873K, while the primary phase fields reduce distinctly.IntroductionThe main oxide components of vitrified bottom ash slag are CaO, Al2O3, SiO2, Fe2O3, MgO, and Na2O, accounting for more than 90% of the bottom ash by weight[1]. During slag processing, the knowledge of thermodynamic properties and liquidus temperature in the related slag systems is highly required [2, 3], which is not yet available. Through literature survey [4-6], it is clear that the systematic information on the concerned complex slag system is scarce. So far the engineers in the field have to make assumptions of the thermodynamic properties of the simplified oxide system, without taking into consideration the interactions of the different oxide components, which hinders the development of the slag valorization and utilization. In order to provide thermodynamic properties for the application of the vitrified bottom ash, the six-component oxide system (CaO-MgO-Al2O3-SiO2-FeOx-Na2O) is highly required. A preliminary phase diagram of the CaO-MgO-Al2O3-SiO2-FeOx-Na2O system can be obtained from extrapolation of the thermodynamic functions of constituent subsystems such as CaO-SiO2-FeOx-MgO, CaO-SiO2-FeOx-Al2O3, CaO-SiO2-Na2O-MgO and CaO-SiO2-Na2O-Al2O3. In this work, the equilibrium phase relation and liquidus of CaO-SiO2-FeOx-Al2O3 system, one subsystem of the concerned complex slag system, are calculated and the effect of temperature is also discussed."

Jan 1, 2012

By Junbiao Liu

Rutile is mostly produced from placer sands. Its beneficiation from primary deposits has rarely been investigated. However, there is interest in primary deposit because of the depletion of sand deposits. The Zaoyang deposit in China is the only rutile primary deposit currently mined. The plant employs a Tabling-Magnetic process which recovers only 20% Ti02 at a grade of 87%. This study shows that significant improvement on the recovery (52% at the same grade) can be achieved. This study includes a detailed mineralogical examination and the development of a processing flowsheet of the ore. The gangues are primarily amphiboles, garnets, zoisites, and chlorites. The liberation of rutile occurs at about 200 mesh. Gravitational, flotation, and magnetic separations are all employed in the process developed, depending on the mineral characteristics and experimental results. The flotations circuit utilizes benzyl arsonic acid to float rutile and sodium fluosilicate to depress the gangues. This is a new reagent scheme for rutile flotation.

Jan 1, 1989

By Huang Chao

The thermodynamics analysis on reducing-matting smelting of sulfide ore of lead, antimony and bismuth which use ferric oxide as sulfur fixed agent is first analyzed. Due to the analysis of reaction mechanism, ferric oxide is first reduced to ferrous oxide, then ferrous oxide produce reducing-matting reaction with sulfide ore and reducing agent as reaction equation: MeS+FeO+CO=Me+FeS+CO2. The reaction thermodynamic calculation shows that the reducing-matting reactions of lead sulfide, antimony sulfide, Jamesonite, and bismuth sulfide are feasible, but is infeasible for zinc sulfide. These conclusion provide a feasible method for solve the pollution which produced in the smelting of sulfide ore of lead, antimony and bismuth.

Jan 1, 2006

By I. G. L. Sinclair

The Selbaie deposit is located in northern Quebec. It is comprised of three distinct, but genetically related, Cu-Zn-Ag ore bodies which also contain economically significant amounts of Au. The deposits are Archean in age and volcanogenic in origin. At Selbaie, ore microscopy has been employed to aid in planning of ore beneficiation methods and to monitor the ongoing performance of the concentrator. Examples of both types of study are described. Early in the life of the mine, excessive amounts of Zn appearing were found to be appearing in the Cu concentrate. Microscopic examination of concentrates showed that this was being caused by the presence of coatings of supergene chalcocite on sphalerite grains. Fine coatings of supergene galena and chalcopyrite were also observed on some sphalerite grains. The presence of Ag and Au in the ores makes an important contribution to the revenue of the mine. The various modes of occurrence and mineralogical relationship of these two metals are described and discussed. Monitoring of the ongoing concentrating process at selbaie is done by qua-litative and quantitative examination of products collected at various points along the circuit. Causes of such problems as excessive loss of metals to the tailings or inefficient recovery of individual metals, can often be identified and possible solutions proposed.

Jan 1, 1989

By N. Bazzanella

The hydrogen desorption kinetics of pure and Nb-doped magnesium hydride film samples was investigated by using a Sievert-type apparatus. The overall activation energy and the reaction order controlling desorption are (141±5) kJ mol-1H and n 4 for Mg hydride and (51±5) kJ mol-1H and n 1 for Nb-doped (5% at) Mg hydride indicating that, in the doped sample, hydrogen desorption is controlled by the H migration in transformed h-Mg layers. Structural analysis performed by X-Ray Diffraction (XRD) and Extended X-Ray Absorption Fine Structure spectroscopy (EXAFS) show that the catalytic effect of the Nb dopant is connected with the formation of NbH0.89 nanoclusters dispersed in the Mg hydride matrix. It is suggested that the catalysis process is also connected to the presence of Mg-Nb hydride interfaces where the transfer of H atoms preferentially occurs by connecting h-Mg grains and by the role of the MgH2-NbH0.89 interface as preferential site for the dissociation of the hydride phase.

Jan 1, 2006

By R. L. Miller

An industrial wastewater, including plating wastes, is treated with sodium sulfide and ferrous sulfate to form a sulfide-oxide precipitate containing chromium and other toxic metals. Hydrocarbons, in the water, coat the sulfide-oxide particles, impeding metal recovery. Froth flotation, without reagent addition, was found to recover 93.9% of the solids from the sludge with simultaneous rejection of 89% of the water. Methyl isobutyl carbinol (MIBC) improved recovery and potassium amyl xanthate improved both recovery and grade. The process design has wastewater feed (without MIBC) to the rougher circuit. The rougher concentrate is conditioned with MIBC and fed to a cleaner circuit to achieve a high grade concentrate. About 95% of the water is recirculated to the waste treatment plant.

Jan 1, 1992

By H. Kandemir

An experimental study of the bacterial oxidation of naturally occurring high-purity sulphide minerals (FeS2, Fe1-xS, Cu5FeS4, ZnS) is presented using a mesophilic strain of T. ferrooxidans. As well as metal analyses and solution pH, partitioning of sulphide sulphur into elemental sulphur and sulphate has been monitored as a function of leach time. Partially oxidized sulphide substrates have been characterized, at regular time intervals, by X-ray diffraction methods and extracellular organic compounds reporting into leach solution .have been identified by thin layer -chromatography.

Jan 1, 1985

By Li Rongxing

A general regular solution model put forward in this paper defines a general interaction parameter that includes both composition and temperature dependence. On the basis of this model, analytic express of solution excess properties was obtained by least square fit using the composition and temperature relations in binary alloy phase diagram. After some solution excess properties analytic expresses of correlated binary alloy system obtained, the analytic express of ternary alloy system could be obtained by superposition of general geometrical model. The ternary alloy system Pb-Sn-Zn has been predicted in terms of this method and the result was very in agreement with actual measured value.

Jan 1, 2006