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By M. Girgis

The behavior of arsenic III during electrolytic refining of copper in acidic copper ?sulphate electrolytes was studied by different electrochemical methods such as, linear potential sweep, cyclic voltammetry, chronoamperometry and chronopotentiometry. The study showed that arsenic behaves as a depolarizing ion and has a deleterious effect on copper deposit. Three substrates; Pb, Cu and Ag were used during the refining process and the electrode kinetics were found similar for both Cu and Pb electrodes while a little difference was found for the Ag electrode. A microscopic study by scanning electron microscope was undertaken to show the influence of arsenic on deposit's morphology. Surface analyses of the deposit were carried out by some electronspectroscopic techniques such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that arsenic coexists with copper deposit at potential?~ -0.25 V.

Jan 1, 1987

By John J. J. Chen, Barry J. Welch

"As in many industrial processes, the detailed mechanisms involved must first be understood before being able to redesign, or to carry out improvements or optimisation of the process and equipment performance. In a great majority of metallurgical processes, visual observation and actual measurement of process variables are either very difficult or near impossible. Often, the cost and effort involved are prohibitive. Consequently, physical modelling is often used to provide some understanding of the process and for the validation of computer numerical models. In this paper, we summarise some of the work carried out at The University of Auckland on the modelling of the Hall-Héroult electrolytic cell, the in-line melt treatment process, and the steel casting tundish. IntroductionIn any industrial process, it is essential to understand the underlying mechanisms before any optimization or process improvement can be carried out. In many metallurgical operations, the processes are conducted at elevated temperature and under rather hostile environments. Consequently, it is often difficult, and sometimes impossible, to observe the actual processes occurring, or conduct measurements which are pertinent. In some situations, it is possible to formulate mathematical equations purported to describe the process, and obtain the solutions numerically. However, in this latter case, the validity of the simplifying assumptions made are often uncertain. Physical modelling may provide the necessary information for the validation of such numerical models. Furthermore, through an application of the principle of similitude, it is possible to apply data obtained from physical modelling to actual metallurgical processes. This paper will summarise some the work carried out at The University of Auckland on the physical modelling of gas-induced flow in the Hall-Héroult electrolytic cell, an in-line melt treatment unit, and the flow in a steel casting tundish.Gas-Induced Flows in a Hall-Héroult CellIn an aluminium cell, the effects due to electro-magnetic forces have been addressed and various design modifications such as magnetic shielding and the positioning of risers have been carried out to control or lninimise the effects of magnetic fields'. Consequently, the effects of gas-induced flows are now becoming significant providing the impetus for the study of the gas behaviour in the bath. Furthermore, the shape and size, and the rate of evacuation of the anodically generated gases affect the cell voltage affecting the energy efficiency; at the same time, the back-reaction between the anode gas and the metal produced is the predominant cause of the loss of current efficiency. Figure 1 shows a cross-section of a conventional cell in which the gas evolution occurs directly under the anodes, and the gas induced flow is confined mainly to the region occupied by the bath"

Jan 1, 1994

By Yotamu Stephen Rainford Hara, Animesh Jha

The investigation focuses on a low temperature recovery of Cu and Co from a 40 wt% SiO2-(30 wt%Fe,6 wt%Al)2O3-10wt% CaO-7wt%CuO-7wt%CoO slag over a temperature range of 1173K to 1323K. The alloy phases containing Cu-Co and Fe-Co alloy formed via the carbothermic reduction of oxides: MO + C = M + CO(g), where M represents metallic copper, cobalt or iron. In the direct reduction of oxides, the recovery of metallic phase was well below 90% at 1323K, due to the kinetic barrier which was analysed and attributed to oxygen and metal-ion transport in the slag. This barrier was overcome by adding CaSO4 and carbon, which yields a matte (MS) phase via MO + CaSO4 + 4C = MS + CaO + 4CO reaction. Lime thus produced in situ participates in metal oxide/metal sulphide reduction reactions, which are analysed with the help of X-ray powder diffraction, scanning electron microscopy, and thermogravimetric analysis.

Jan 1, 2014

By Anna Franzkowiak, Dean Gregurek, Alfred Spanring, Angelika Ressler

In order to determine the most suitable refractory products and improve the lining lifetime for the diverse furnaces used in the nonferrous metal industry, corrosion tests are performed at RHI’s Technology Center. The practical facilities include the cup test, induction furnace, rotary kiln, and drip slag test described in this paper, which enable a comprehensive understanding of the chemo-thermal brick wear on a pilot scale. The corrosion trials are performed with actual slags generated during operations at a customer’s plant. To determine the highest influencing wear parameter, every single test is combined with a detailed mineralogical investigation and thermochemical calculations performed using FactSage. Based on the results, tailored refractory solutions for the nonferrous metal industry can be provided in combination with trials conducted at the customer’s site.

Jan 1, 2014

By Vaughan R. Voller

"Over the last ten years an increasing number of heat and mass transfer models of solidification processes have been presented in the literature. A key component in these models is the coupling between thermal and solute fields. This is achieved by developing relationships based on the behavior at the microscopic scale in the casting (typically a secondary dendrite arm space). An important class of models in this respect are models that describe the local scale redistribution of solute alloy components-collectively referred to as microsegregation models. This paper explores this class of models.IntroductionModeling takes a key role in processing materials for properties. This is particularly time in solidification processes where current computer techniques allow for a detailed treatment of the critical macroscopic phenomena. Typically these macro scale models consist ·of three main coupled components.1. A model of flow in the melt and solid + liquid mushy region.2. A model of heat transfer.3. A model of solute transport.The focus of this paper is the solute transport component, in particular the manner in which process scale transport is coupled to transport ·at the local scale of the solid-liquid interface. This step requires a modeling of the redistribution of solutes at the scale of the secondary arm spaces in the dendritic mushy region-a process referred to as microsegregation. Basic microsegregation models use the limit assumptions of no mass diffusion in the solid (Gulliver-Scheil [l]) or complete diffusion in the solid (equilibrium lever rule) in a fixed and space. Recently, however, more sophisticated microsegregation models that account for finite mass diffusion and coarsening of the arm space have been developed [2-19]. In this paper governing equations for a general microsegregation model for a multi-component alloy in a coarsening and spacing _are introduced. From these general equations various models for a binary system are developed and tested"

Jan 1, 2000

By R. H. Lien

The Bureau of Mines, U. S. Department of the Interior, is investigating chemical and biological decontamination of complex wastewaters such as tailings pond water containing 280 ppm CN and 5 ppm Se as well as significant concentrations of arsenic, copper, iron, silver, and zinc. The most effective chemical procedure involves cyanide oxidation using hydrogen peroxide or sodium hypochlorite followed by selenium reduction using ferrous hydroxide. The effluent contains <l ppm CN and 20 ppb Se; concentrations of other major contaminants meet EPA drinking water standards. Preliminary research indicates that biological cyanide oxidation is possible even in highly alkaline solutions (pH 10.5) containing high cyanide concentrations; indigenous bacteria destroyed 85 pet of the cyanide. Exploratory research shows that other bacteria removed up to 79 pet of the selenium from chemically oxidized, low-cyanide water. These promising results may lead to a final processing scheme that involves a combination of chemical and biological techniques.

Jan 1, 1990

By Pesic. Batric

A novel chitosan-pyridoxal-epichlorohydrin was synthesized and evaluated in our laboratories. The evaluation was achieved by performing kinetic and equilibrium studies of copper sorption. The parameters examined were pH, temperature, concentration of copper, particle size and selectivity of copper sorption against iron, zinc, cadmium and cobalt. It was found that pH was the most important parameter, and sorption of copper increased with pH increase in the range pH 2.5-6.0. The low activation energy of the sorption reaction, 1 1.13 kJ/mole (2.66 Kcal/mole), showed that temperature was not an important parameter. The synthesized chitosan was selective against iron, zinc, cadmium and cobalt. The selectivity with respect to last three metals was achieved by the kinetic difference of sorption, as sorption of copper was much faster than for other metals. Iron (Fe2+) does not adsorb on chitosan. The mechanism governing the sorption of copper is intraparticle diffusion. This finding was supported by the dependance of copper sorption on the square root of time, the low activation energy, and the fit of experimental data in the diffusion through the product layer equation.

Jan 1, 1994

By Xie Zhang, Jiang Diao, Xiaojun Li, Bing Xie

"Vanadium is widely utilized as an important element to improve the quality of alloyed steels in iron and steel industry. Moreover, the crystallization process of V-containing spinels plays a significant role due to the aim of achieving a fairly larger size of spinel crystals in vanadium extraction. Thus, a comprehensive exploration and discussion on the competitive precipitation and growth of vanadium, chromium and titanium spinel crystals in vanadium slag during a cooling process were carried out in the present study on the basis of a crystallization kinetic model. To be more specific, the abilities of forming crystal, precipitation order and suitable temperature range for crystallization of the three kinds of spinels were discussed with both theoretical and experimental methods.IntroductionVanadium is an important element which is used almost exclusively in ferrous and non-ferrous alloys due to its excellent physical properties such as high tensile strength, hardness, and fatigue resistance [1]. Various kinds of processes of vanadium extraction from V-containing hot metal are available at present. However, only four processes which are the Highveld process (South Africa), the Pan-steel process (China), the NTMK duplex process (Russia) and the New Zealand steel process (New Zealand) take the dominant positions [2, 3]. Although the type of reactor and the initial vanadium content in hot metal are different in these techniques, they share the same principle that vanadium is oxidized by oxygen into vanadium slag."

Jan 1, 2012

By E. Ozberk

The copper and nickel smelting industries are important contributors to the technical and economic well-being of Canada while some of the smelters are among the largest sources of sulphur dioxide emissions in Canada. A review of the operations in six smelters - Falconbridge Limited, Falconbridge, Ontario; Hudson Bay Mining and Smelting Co. Limited, Flin Flon, Manitoba; Inco Limited, Copper Cliff, Ontario and Thompson, Manitoba; Noranda Mines Limited, Horne Division, Noranda, Quebec and Gaspe Mines Division, Murdochville, Quebec - have shown that about 80% of the total sulphur input to these smelters was emitted to the atmosphere in 1980. A simultaneous review of the existing and emerging technologies which can directly or indirectly reduce the sulphur dioxide emissions indicated that it is possible to reduce the emissions to below 20% of the sulphur input to these smelters. This can be achieved by varying degrees of modifications to the smelting operations and installing sulphur fixation facilities at significant costs which may increase the metal production costs. This would consequently make the competitiveness of the Canadian copper and nickel producers more difficult in the already tough world metals market.

Jan 1, 1983

By J. Gartelmann, B. Zaslavsky, Y. Vojta, D. J. Chaiko, W. Mego, A. N. Rollins

"Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that we have studied are generated by combining an aqueous salt solution with an aqueous polymer solution.We have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. We have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this chapter we review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.IntroductionAqueous biphasic extraction (ABE) is a highly adaptable separation technique that can be used in a wide range of applications. We have been evaluating various types of ABE systems for possible applications in the treatment of solid radioactive wastes (1,2), liquid nuclear wastes (3,4), and contaminated soils (5-7), and in the removal of organics from aqueous salt solutions (8). We have also conducted fundamental studies of the solution microstructure of ABE systems using small angle neutron scattering (SANS) (9).The extraction systems are generated by combining an aqueous salt solution and an aqueous polymer solution. This produces two distinct liquid layers that are as immiscible as oil and water, yet each liquid layer contains at least 70 to 80 wt % water. The biphasic systems that we have been working with consist of immiscible polyethylene glycol (PEG) and salt solutions. Some inorganic salts that promote biphase formation with PEG solutions include the sodium/potassium salts of sulfate, carbonate, phosphate, and hydroxide (10)."

Jan 1, 1996

By Kafui Nyavor

Acid mine drainage (AMD) is presently the biggest single environmental problem facing the mining industry. New and expanding metal mines in most parts of the world have to demonstrate their ability to contain this problem to obtain operating permits. Conventional methods of controlling acid mine drainage have primarily been limited to collecting the drainage and neutralizing with alkaline materials which do not provide a permanent solution to the AMD problem. Since acid mine drainage results from the oxidation of sulfides in the presence of oxygen, water and iron-oxidizing bacteria, controlling any of these three factors contributing to pyrite oxidation provides a potential at-source remedy for reducing or preventing acid mine drainage formation. Physical properties such as hydrophobicity also play an important role in the attachment of bacteria, adsorption of oxygen, water, and other ions that subsequently lead to the oxidation of pyrite. In this communication, the suppression of pyrite oxidation by treatment with fatty acid amines (FAA) was investigated. The FAA treated pyrite samples were tested at various conditions of temperature and pressure. At an elevated oxygen pressure of 500 psi and a temperature of 600 C, less than 0.2% oxidation was obtained for the FAA treated pyrite samples, while over 1.2% oxidation was obtained for the untreated samples in 10 hours of oxidation time. Accelerated column oxidation tests at ambient condition showed that FAA mated samples reduced pyrite oxidation by at least 75% in 81 days.

Jan 1, 1994

By William Gregg

Recent environmental and workplace safety legislation has Imposed more stringent limits on the amount and type of particulate emitted Into the air. In the past, the mass of particles contained In a volume of air was the governing criteria. Now the size and precise chemical nature of the particulate must be known and controlled In addition to it&apos;s ?mass. Processors of metallic materials have to implement stricter control practices and more efficient control equipment to meet the new regulations. Pulse-Jet dust collector systems are being used to control particulate emissions from various process gas streams. Pulse-jets :are also being used for maintaining a healthy environment In the workplace. this paper will discuss the impact of these regulations, the control techniques used to comply with such regulations, and the equipment needed for compliance.

Jan 1, 1992

By S. M. Hay

The zinc content of blast furnace and basic oxygen furnace dusts is low compared with electric arc furnace dusts and it is generally not economical to treat the dusts to recover zinc. However, they have a high iron content and removal of the zinc would allow recovery of the iron values. A literature review and thermodynamic analysis was undertaken and, as a result, several smelting options were identified. This paper describes experiments undertaken to develop understanding of metallurgical aspects of these processes which are not amenable to theoretical analysis. Dusts from an Australian steelworks were characterised in order to determine their mineralogical make-up and the form of the iron. The processing aspects investigated in the laboratory were slag-metal equilibrium and solid-state pre-reduction using reducing gases of compositions expected from bath-smelting processes. Particular attention. was paid to the deportment of zinc, sodium, potassium, phosphorous and sulfur between the phases formed during smelting and pre-reduction. The smelting results indicate that less than 10% of the zinc, sulphur, sodium and potassium report to the metal. About 99% of the zinc and potassium and about 80% of the sodium could be volatilised from the dusts by reducing them at 1,000°C with mixtures of CO, CO2, H2 and H2O even when metallic iron was not formed. The experiments indicate that smelting of blast furnace and basic oxygen furnace dusts should produce hot-metal of a composition which can be blended into the main stream of hot-metal in the steelworks.

Jan 1, 1994

By Yogeshwar Sahai

Submerged gas injection into melts contained in furnaces, ladles, or similar transfer vessels is commonly used in industrial practice. In this review paper, conditions leading to gas bubble formation at the nozzle are first summarized. The increasing gas injection rates and other conditions, such as nozzle size, lead to regimes which are commonly known as "bubbling" and "jetting". These are explained. The gas/melt interactions result in energy transfer to the melt. In recent years, a large number of researchers have investigated the relationships between the energy density and the mixing times. Their work is reviewed, and the mixing mechanisms is described. Finally, computational approaches of modeling submerged gas injection are briefly presented.

Jan 1, 1993

By A. Mejias, M. A. Garcia, G. Diaz

During 1997 and 1998 two successful zinc feasibility studies, Skorpion and Sanyati, were carried out by Tecnicas Reunidas based on the modified ZINCEX® technology. The technical viability of each project was proved during more than 600 h of continuous running in a pilot plant. The Skorpion zinc project would recover 150,000 t SHG Zn/y from an oxidized zinc ore of a Namibian mine. The economical study showed that the plant would have the lowest production costs in the world. The Sanyati zinc project would treat a bleed from an existing copper refinery in Zimbabwe to recover 5,000 t SHG Zn/y. In the first case the electrowinning cellhouse was supplied by Union Miniere and in the second by Tecnicas Reunidas. This article highlights the pilot plant results and the advantages of the proposed process over conventional zinc production practices.

Jan 1, 2000

By S. Seetharaman

In the processing of molten metals, it is extremely important to monitor continuously the concentration levels of various minor elements, In the production of common metals like copper, iron and aluminium electrochemical sensors involving solid, as well as liquid electrolytes are being increasingly used to measure the concentrations of minor elements The present paper deals with the electrochemical principles underlying these measurements and the possible errors involved. One of the major difficulties in the case of the solid electrolytes is to correct for the consequences oldie electronic contribution to the conduction of the electrolyte. The application of the electrochemical sensors for molten metals processing involves designing of these probes to withstand the industrial operating conditions. In this respect, significant achievements have been made with respect to the design of oxygen probes for liquid metals in general and liquid copper in particular. Some of the salient design features are discussed in the paper, The application of auxiliary electrodes for impurities in molten metals like phosphorus in copper and silicon in iron are taken up. The development of oxygen sensors for slags is given special attention. Recent developments&apos; in the field of sensor technology, as applied to metals processing are highlighted.

Jan 1, 1996

By Wenjie Zhu

Chromite ore processing residue (COPR) is a hazardous waste containing high concentration of chromium. We describe here a pioneer trial of detoxification of COPR in column reactor with an indigenous chromate reducing bacterium Leucobacter sp. Ch1, which showed high chromate reducing ability at high pH. Under the optimum conditions, at 30°C and pH 10.0, pH of leachate decreased from 10.3 to 8.3, and Cr(VI) concentration in solution decreased to zero mg L-1, and 76.4% of Cr(VI) was removed from COPR samples. The leaching toxicity of detoxified residue was 1.1 mg L-1 that was lower than national standard of China.

Jan 1, 2008

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 Cissé Kane, Klaus Hieronymi, Mathias Schluep, Gerry Newson, Susanne Dittke

"E-waste is currently the fastest growing waste stream in South Africa as well as in many other African countries. Informal collectors, dismantlers and recyclers based in Africa play an increasingly larger role in the processing of e-waste under generally unacceptable social and environmental conditions. In direct response to this trend, and as part of Hewlett Packard’s international Extended Producer Responsibility, the project “e-Waste Management in Africa” was started in 2007 in cooperation with the Global Digital Solidarity Fund (DSF) and the Swiss Federal Laboratories for Materials Testing and Research (Empa). This project is investigating the e-Waste situation in various African Countries, including South Africa, while actively supporting the development of practical, socially just and environmentally acceptable local e-waste management solutions. To this end, the project has been funding the development of a pilot project in Cape Town, South Africa since February 2008, supporting the start-up of a low tech/highly labour intensive material dismantling and recovery facility (MRF) for the pre-processing of e-waste. The aim is to test the feasibility of an integrated value adding local e-Waste management system, designed to maximize the potential of refurbishment, repair, re-use, dismantling and recycling of equipment, with environmentally responsible disposal as a last resort only. The project also seeks to incorporate the current informal e-waste processing activities, by transforming them into sustainable and environmentally sound operations. The MRF acts as a nucleus, raising awareness, and providing training and education to previously disadvantaged individuals as a means of creating opportunities for entrepreneurship in the technical maintenance, dismantling and waste-to-art project sectors."

Jan 1, 2008

By J. L. Jambor

Previous crystal-structure determination of magnesian annabergite (Ni,MgMAsO4)2 8H2O indicated that ordering of Ni and Mg occurs in non-equivalent octahedral sites; such ordering supports the possibility of miscibility gaps on the Ni3(AsO4)2 8H2O -MgiAs04)2 8H2O. (annabergite-hornesite) join. In a predecessor study based on analyses of natural specimens, it was proposed that solid solution is incomplete both for annabergite-hornesite and annabergite-erythrite [Co, (AsO4)2 8H2O]. In the current study, syntheses by use of a slow-addition technique and aging of the precipitates indicated that the annabergite-erythrite solid solution is complete, and that no miscibility gap is present on the annabergite-hornesite join to at least 58 mol % Mg. Thus, interpretation of the compositions of these phases in oxidized mill-tailings impoundments can be done with the normal precautions for homogeneity, and without the added concern of the possible presence of miscibility gaps in the ternary system.

Jan 1, 1995