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By Renato G. Bautista

The prospect for recovery of rare earths from red mud, the bauxite tailings from the production of alumina is examined. The Jamaican red mud by far has the higher trace concentrations of lanthanum, cerium, neodymium, and yttrium. Scandium is also present. The dissolution of the rare earths is a major extraction problem because of the large volume of other materials present. The recovery processes that have been proposed include the production of co-products such as iron, alumina, and titania concentrates, with the rare earths going with the titania A critical examination of the possible chemical processes for the complete utilization of the red mud are presented Recommendations for research projects considered to be important in the development of a chemical separation process where no pig iron product is contemplated are also discussed.

Jan 1, 1992

By Jian Wang, Hongyang Cao, Binxiu Wu, Junhong Li, Jimin Wang

"The enrichment and separation of scattered metal indium component in the pressure leaching solution with sulfuric acid from vacuum furnace germanium slag were studied by iron substitute and P204 extraction, which is supplied by shaoguan smelter. The experimental results show that the extracting power of P204 for indium from pressure leach solution is powerful. The optimal technological condition were the ratio of P204 and sulphonating serosene 3:7, phase ratio 1:3, solution pH 1.2, and extracting 5 minute. The enrichment indium solution of 21.7 g/L In at 95.2% recovery ratio was obtained by three-stage counter flow extraction and four- stage counter flow stripping.IntroductionScattered metals, such as Indium and germanium, were inriched as intermediate product or by-product during the metallurgy process of other non-ferrous metals, such as lead, zinc, copper and tin. For example, the indium and germanium were inriched in vacuum furnace germanium slag, which is the by-product of zinc vacuum distillation operation from hard zinc. It is difficult to recovery the indium from the vacuum furnace germanium slag, because the indium content is low, and the chemical composition and phase compositon were complex.Recovery indium from bearing indium zinc slag was researched extensively, such as pressure acid leaching, high temperature evaporation, solvent extraction method[l-7], acid leaching method has the advantages of high leaching rate, which can be separated hydrochloric acid, sulfuric acid and silicon fluoride acid systems. Solvent extraction method has the advantages of low production cost, fast reaction speed, high enrichment ratio, and simple operation."

Jan 1, 2013

By Lidong Teng, Seshadri Seetharaman, Aida Abbasalizadeh

0In the present paper, the feasibility of the recovery of dysprosium from spent Nd-Fe- B magnets containing approximately 9 wt% Dy was investigated by using molten salt process. The salt bath consisted of a mixture of NaCl-KCl-LiCl corresponding to the ternary eutectic composition. AlCl3 was used as a chlorinating agent in order to enable an efficient dissolution of metal in the molten salt phase in the salt bath. The metal chloride which is formed as the result of chemical reaction between the metal in magnet and AlCl3, is subsequently subjected to electrolysis in order to be deposited on the cathode. Graphite rods were dipped in the salt bath as electrodes and alumina crucibles were used as the containers for the electrolytic cells.

Jan 1, 2014

By Victor Bredykhin

The reasons of formation low quality cathode deposits and conditions of the anode passivation in electrorefining of copper silver alloys with increased (more then 5%) silver content in electrolyte, g/l: Cu - 40; H2SO4-50; 150 and 250; T= 401C have been investigated. As it is shown, increased acidity, anodic current density and silver content in anodes favor passivation. The assumption is made that the ingress of silver on cathodeis the most probable reason of growing dendrites on cathode. We have determined that addition of ethylene carbonic acid to electrolyte in the amount of 3,5 ÷ 10 ml/l suppresses the dendrite formation.

Jan 1, 2006

By Felipe P. D. Lopes, Jr. dos Santos, Sergio N. Monteiro, Frederico M. Margem

"Natural fibers are gaining attention as a class of low cost, biodegradable and renewable materials that also exhibit some interesting properties for specific applications. In particular, the incorporation of some natural fibers in polymeric matrix composites is nowadays providing opportunity of manufacturing a variety of industrial items, for instance automobile interior components. Among these fibers, ramie (Boehmeria nivea) is one of the least investigated and only recently was studied as polymeric composite reinforcement. Therefore, the objective of this work was to evaluate the possibility of ramie waste reinforced polyester composites to replace conventional building materials, such as plywood, plastic boards and gypsum panels in terms of a cost-benefit analysis.IntroductionThere is a growing concern over the environmental questions that are presently affecting our society in a global sale such as climate changes and generalized pollution. Among the solutions for these questions, the replacement of energy intensive materials, especially those long term degradable such as the synthetic fibers, is already being considered [1]. As a consequence, the past decades have witnessed an increase in research devoted to new biodegradable materials obtained from natural resources mainly the biomass. Important examples are the renewable natural fibers as well as composites incorporated with them [2,3]. In addition to their friendly status with respect to the environment, well know natural fibers like jute, sisal, wood, coir, hemp and flax are relatively low cost and recyclable. In recent works [4,5], the use of these cultivated and abundant lignocellulosic fibers was investigated as the reinforcement phase in polymeric composites.Other less know lignocellulosic fibers have also been recently investigated [6,7]. These are fibers that likewise show a potential of incorporation into the polymeric matrix of composite materials. Most of these less know fibers are typical of tropical regions and, in principle, their application in industrialized composites would represent job opportunities for developing countries in Africa, South Asia and Latin America."

Jan 1, 2008

By Esperidiana A. B. Moura, Mariana N. Sartori, Vijaya K. Rangari, Angel Visentim Ortiz, Francisco R. V. Diaz, Rene R. Oliveira

"This work presents the preparation and characterization of a nanocomposite based on Poly(butylene terephthalate) PBT and Brazilian smectitic clay (bentonite chocolate clay). Before being incorporated as clay nanoparticles in PBT resin, the clay was organically modified by the addition of a quaternary salt and sodium carbonate. PBT/Clay nanocomposite (96.3:3.70 wt %) was obtained by using a twin-screw extruder machine. After extrusion process, the nanocomposite was characterized by tensile, flexural and impact tests, SEM, Vicat, HDT, DSC, TGA and XRD tests. The results showed that the properties of the nanocomposite obtained were superior to those of neat PBT. Concerning the temperature of thermal distortion (HDT) an expressive gain of around 45 % was presented to PBT/Clay nanocomposite compared to PBT evidencing the interaction of nanofiller with the polymeric matrix.IntroductionPolymer-clay nanocomposites, also called as polymer layered silicates nanocomposites have attracted much attention from both industry and academia over the past decade because they frequently exhibit unexpected properties. In contrast to the traditional fillers, nanofillers, in particular, nanoclay, is found to be effective. The addition of a small amount (< 5 wt.%) can show significant improvement in mechanical, thermal and barrier properties, flammability resistance, and electrical/electronic properties of the final polymer nanocomposite without requiring special processing techniques. Also, as with other nano-size particles, the overall crystallization rate and the glass transition temperature are also affected. It is generally believed that the improvement of properties of nanoclay composites is directly related to the complete exfoliation of silicate layers in the polymer matrix. However, a processing technique that produces complete exfoliation is still a technical challenge [1,2]."

Jan 1, 2012

By T. Xin

A vertical grain boundary intercepting a horizontal free surface forms a groove to reduce the combined surface energy of the system. We study grooving by surface diffusion with anisotropic surface energy. A recently developed delta-function model of facets is used to describe the surface energy with three or four fold symmetry. It is found that the groove grows following a similarity law. The self-similar groove profile is solved numerically by a shooting method. Even with strong anisotropy, the groove profile can be smooth if the exposed surface orientations do not include a facet orientation. The smooth self-similar groove shape is the same as an isotropic groove, but the size is reduced by a factor that depends on the degree of anisotropy. This induces a large error on the value of surface diffusivity if the isotropic model is used for an anisotropic system. In this talk. we will describe how to correct for this error.1 I Xin, T. and H. Wong, "Grain-Boundary Grooving by Surface Diffusion with Strong Surface Energy Anisotropy," Acta Materialia 51, 2305-2317 (2003). Keynotes: Grain growth, Surface Diffusion, Surface energy, Anisotropy

Jan 1, 2003

By M. Somerville

In 1989 CSIRO Minerals initiated investigations into continuous converting of copper matte into low sulphur blister in Sirosmelt type reactors. Following the successful piloting of this processing route, some effort was directed towards a single stage copper making process where copper metal is made in one step from concentrate. The aim of the project is to develop a continuous process, which offers considerable environmental and economic benefits over conventional copper making processes, which use Pierce-Smith converters. In the selection of the optimum flowsheet a number of slag treatment options have been considered and tested. These unit operations include: leaching and electrowinning, flotation-leaching-electrowinning and flotation with recycling of recovered copper through the smelting vessel. In this paper the suitability of these process options are evaluated using the available information and recently measured copper recoveries from our testwork at CSIRO. The operating and capital costs of the various options have been estimated using Aspen Plus simulation procedures. The most attractive flowsheet in terms of capital and operating costs is the treatment of slag using mineral processing techniques and the recycle of a copper slag concentrate to the smelting vessel. It has been found that the chemistry of the slag being treated has a large bearing on the recovery of copper in flotation and hence on the economics of the process.

Jan 1, 1999

By Ning Wang, Bing Xie, Hong-Yi Li

"Compared to traditional sodium roasting, calcified roast inhibits chlorine pollution. A vanadium extraction technique based on a calcified roast is especially suitable for vanadium slag with high calcium content. In this report, V205was extracted from vanadium slag by calcified roast followed by acid leaching and hydrolysis precipitation. In optimized conditions, the high silicon low vanadium slag was roasted at 850'C for 2 hours without CaO addition. The roasted materials were leached with 35 % H2SO4 in liquid/solid ratio of 5:1 (mL/g) at 95OC for 4 hours. The extraction of vanadium was as high as 97.66 %. These results are instructive to V2O5 production in industry.IntroductionVanadium slag is produced in converter, sodium salt roasting is the commonly used technique to extract vanadium. In sodium salt roasting, vanadium slag is roasted with sodium salts including sodium chloride and soda as additives, followed by leaching with acidic or basic solution [1]. However, in this process chloride reacts to produce corrosive gases including HC1 andCl2- SO2 and SO3 can also corrode equipment severely and are also an environmental contaminant. The low melting point of sodium salts leads to fusion agglomeration, which blocks vanadium oxidation and thus decreases the extraction rate of vanadium. A large amount of sodium salts consumed as roasting additives increases the production cost. Moreover, sodium salt roasting requires low CaO content in vanadium slag. When the CaO content increases to 1%, V2O5 extraction can amount to 4.7%-9% [2]. For vanadium slag with high CaO content, the sodium salt roasting technique leads to low vanadium extraction rate."

Jan 1, 2012

By Edouard Asselin, Guikuan Yue

"In the present study, electrochemical measurements, especially cathodic potentiodynamic polarization (CPC) and cyclic potentiodynamic polarization (CPP), have been employed to study the kinetics of ferric reduction on chalcopyrite in aqueous Fe( II )-Fe(III)-H2S04 solution at 25°C and 70 °C. Results from the calculation ofspeciation in the above solution reveal that, at both 25 °C and 70 °C, the real Fe3+/Fe2+ ratio is much lower than the nominal ratio, which leads to smaller values for the reversible potential of the ferric/ferrous couple based on the Nemst equation. Exchange current densities of the ferric/ferrous couple were obtained by extrapolating the cathodic linear Tafel line to the reversible potential and are on the order of 10-7·10-6 A/cm2 at 25°C and 10·6-10-5 A/cm2 at 70 °C, respectively. The transfer coefficients were about 0.35-0.38 at 25°C and 0.35-0.45 at 70 °C. Polarization plots of CPC and CPP under different nominal Fe3+/Fe2+ ratios are in good agreement at 25 ·c and at 70 °C. Based on the obtained exchange current densities, the rate constant k, was calculated and is on the order of 10-1 cm/s at 25 °C and 10 1 cm/s at 70 °C.IntroductionChalcopyrite is the most abundant copper mineral in nature, accounting for about 70% of copper reserves in the world [I]. In recent years, the metallurgical industry has been searching for a hydrometallurgical process as an alternative to pyrometallurgical treatment due to high emissions of S02 and capital costs associated with smelting. Activity in this area has increased recently due to some inherent advantages associated with hydrometallurgical processing, such as the possibility of treating low-grade ores (increasingly more abundant in the case of copper) and easier control of waste, with the attendant benefits to the environment [I]. Chalcopyrite is highly refractory under most hydrometallurgical conditions, owing to the formation of an anodic passivation layer on the chalcopyrite surface which renders the process kinetics very slow. Most of the currently proposed processes are based on sulfuric acid with ferric ions and/or dissolved oxygen as oxidants. Sulfuric acid is preferred over all other leaching reagents in terms of cost, environmental friendliness, and ease of its regeneration during electro-winning. Some of these processes have been piloted in attempts to implement these technologies on an industrial scale,"

Jan 1, 2012

By Raymond PoIick

The Demag Electric Slag Cleaning Furnace installed at the Asarco Smelter in Hayden Arizona is one of the few rectangular electric furnaces now operating. The long transition times from charge to tap allow exceptionally clean skims (high recovery); however, the furnace design is complex. Additional Asarco requirements for rapid installation and commissioning further complicated the design. When operating and wear effects accumulated after two years of use, steps were taken to rebuild the furnace with enhanced durability based on the design parameters experience in actual use.

Jan 1, 1993

By Melissa L. Trapani

The removal of molten products from metallurgical furnaces is one of the most hazardous and labour intensive processes in a non-ferrous smelter. The proximity of operators to the molten metal and slag during tapping and the oxygen lancing that facilitates the flow have led to many reported injuries on tapping floors. In most cases, tapholes are opened and closed periodically leading to extreme thermal cycling in the tapping assembly. As a consequence, refractory wear rates are high and unpredictable in the taphole. This paper provides a review of the current state of taphole development, and gives a methodology that is now being applied to gain a better understanding of the taphole region to allow design improvements.

Jan 1, 2002

By Ray D. Peterson, Annette Revet

The optimization of secondary aluminum furnaces is critical to the efficient operation of a recycling facility. Since all metal loss occurs in the drosses, physical and chemical analyses of these by-products are valuable diagnostic tools. Dross analyses can provide information concerning total furnace metal recovery efficiency as well as identifying areas for potential improvements. A complete dross analysis is a labor-intensive process that requires significant care both in sampling and performing the analytical techniques. Experiments can be done at a bench- or plant-scale depending on the facilities available. This paper outlines the benefits and information that can be generated through dross studies. Furthermore, several analytical methods are discussed as well as the special requirements needed to gain accurate results. Experimental data from industrial studies is provided to demonstrate the use of dross evaluations for ~ace optimization.

Jan 1, 2000

By Rodney T. Jones

Mintek has developed and piloted a novel process for the treatment of nickel-copper and PGM (platinum group metal) sulphide concentrates. The ConRoast process is based on the removal of sulphur by roasting, followed by smelting of the dead-roasted concentrate in a DC arc furnace using an iron-based alloy as a collector for nickel, copper, cobalt, and PGMs. The environmental benefits with respect to sulphur emissions are considerable, in that essentially all of the sulphur is removed from the enclosed roasting equipment in a continuous stream of SO2 of an appropriate strength for feeding to a sulphuric acid plant. This process allows great flexibility with respect to the selection of ore types, and does not impose limits on the minimum quantities of contained base metals or sulphur, and can tolerate very high contents of chromite in the concentrate. The furnace alloy is water-atomized prior to leaching. Iron may be rejected from the alloy hydrometallurgically, by precipitation as hematite for example. The ConRoast process achieves very high metal recoveries, and produces high-purity metals, and a clean high- grade PGM concentrate.

Jan 1, 2002

By J. Vander Linden, R. De Ketelaere, M. Verhaege

In this paper, results are presented concerning the search to implement Supported Liquid Membrane (SLM) technology for the recovery of copper from electroplating effluents. Acid copper electroplating rinse solutions or effluents resulting from the post-treatment of, for example, cyanide-containing copper electroplating baths all contain copper (2+) in the lower concentration levels. A thorough study of the influence of the individual parameters and of their combined impact on mass transfer in small scale laboratory SLM modules has been performed, enabling to set forward the appropriate operating conditions for a pilot plant installation. The pilot plant, containing two SLM modules. of 18 m2 of surface area, has been tested extensively, including short and long term runs, with real process solutions. It was demonstrated that this installation is able to treat 40 l/h of acid copper sulphate rinse solutions· containing 500 ppm of copper. The final copper concentration in the effluent can be reduced to a few ppm while copper metal is recovered by electrolysis of the concentrate. This technology is also applicable to the treatment of solutions with low copper content of origins other than plating shops, such as tailings from copper plants or mine waters.

Jan 1, 2000

By A. D. Besser

The world production of lead has been growing continuously and reached over 7 million tonnes in 2005. At the same time, the structure of lead consumption has changed: the use of lead compounds to liquid fuel has been virtually terminated; the proportion of lead for manufacture of lead-acid batteries has been growing and reached 76.7% of the overall world production of this metal. This has taken place against the background of increasingly stringent environmental norms and environmental legislation. This is due to the lack of an alternative for lead in manufacture of local power sources. A solution to the problem of meeting the industrial demand for lead with simultaneous reduction in the primary lead production is in recycling. A large amount of batteries manufactured worldwide and their short life cycle, as well as the positive economics and a possibility to comply with the environmental requirements encourage the development of secondary lead production. Currently, over 60% of the world demand for lead is met due to recycling. The current situation with collection, transportation, storage and processing of spent lead-acid batteries has been analyzed in this paper. Examples are given to illustrate technological and equipment solutions and trends for improvement of secondary lead production discussed.

Jan 1, 2006

By Tejs Vegge

The lack of suitable means of storing hydrogen for use in the transport sector is generally viewed as a primary showstopper for a hydrogen economy. Recent developments within solid state hydrogen storage in complex hydrides and metal ammines have sparked new hope of a long term solution, but as of now, no materials fulfill all the DoE targets for onboard storage [1]. A detailed physical understanding of the ab-/desorption processes and the role of the essential catalytic additives is an essential prerequisite for the development of new optimized hydrogen storage systems. Here, we illustrate the potential of utilizing the synergy of combining state-of-the-art in theoretical methods and experimental techniques in the analysis and design of materials for hydrogen storage. Recent advances in computer hard- and software has made it possible to treat many of the essential problems in such materials, i.e. structural stability, hydrogen dissociation and diffusion, with high accuracy methods like density functional theory. We rely on such results to guide our synthesis of new materials, and to interpret our experimental results from, e.g. time dependant in situ x-ray diffraction, synchrotron/neutron experiments, and advanced materials testing. Through a continuous feed-back optimization loop between theory and experiments, the obtained nano-scale insight is used to expedite the design and development of novel materials for hydrogen storage.

Jan 1, 2006

By Nagy El-Kaddah, Thinium T. Natarajan

A modeling strategy is presented for computing the electromagnetic field and the shape of the molten metal in electromagnetic confinement systems. This strategy involves the use of a hybrid finite element/integral technique to calculate the electromagnetic field and force distribution in the melt. The free surface shape is determined from minimization of electromagnetic, gravitational and surface tension energies using the Lagrange method of multipliers. This approach was applied to model the electromagnetic levitation melting process. The model was found to accurately predict the measured shape of levitated droplets.

Jan 1, 2014

By I. E. A. Aghachi

During static strain-aging of low carbon steel, when the material is pre-strained, the dislocation density increases. If totally or partially unloaded and aged for a prescribed time, interstitial solute atoms diffuse under the influence of the dislocation stress fields, thus tending to lock dislocations causing an increase in yield stress. If held for long periods at certain aging temperature, a decrease in yield stress (over-aging) is observed following the initial increase. This behaviour has been variously attributed to either recovery of cold worked dislocation structure and/or formation and coarsening of carbide precipitates. The present work demonstrates that, using a "process control" model for the competing processes of hardening and softening, dislocation recovery is responsible for over-aging of mild steel specimens under conditions tested during this investigation. Keywords: Strain-aging, Precipitation, Recovery

Jan 1, 2003

By Catherine Williams-Beam

Thallium is more toxic to humans than mercury, cadmium, lead, copper or zinc. Its chemical behavior resembles the alkali metals (K, Rb, Cs). It occurs almost exclusively in natural waters the monovalent thallous cation. The solubilities of thallous compounds are relatively high so that monovalent thallium is readily transported through aqueous routes into the environment. The major sources of thallium are the base metal sulfides and precious metal bearing sulfides. Therefore, it is often present as a contaminant constituent in waters emanating from heavy metal sulfide bearing deposits. Thallium can be effectively removed from wastewater to <2 µg/L by reductive precipitation of thallium sulfide. Effective thallium sulfide precipitation requires a controlled solution potential/pH combination. The required potential can be effectively achieved by utilizing a particulate iron slurry or packed column environment. Experimental results will be presented and discussed.

Jan 1, 2003