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By Kazuya Koyama

The leaching of copper from a printed circuit board (PCB) and the electrodeposition of copper from a cuprous solution in ammoniacal alkaline solutions were examined in order to develop an energy-saving hydrometallurgical process for copper recovery from electronic scrap. In the leaching experiments, copper in the PCB was oxidized by Cu(II), and Cu(I)-ammine complex ions were formed. The copper(I)-ammine complex slightly depressed the leaching rate, while Cu(II)?ammine markedly enhanced it. During the electrodeposition experiments, the current efficiency of copper deposition was approximately 100% in the current density range of 200 to 1000 Am-2. The electrodeposition of copper from the Cu(I)-ammine complex solution favored the production of plates rather than powders.

Jan 1, 2003

By Bahram Rezai

Fine particles float poorly and less-selectively under normal flotation conditions. One of the promising methods for fine minerals is the utilization of the principle of Flocculation. Hydrophobic flocculation flotation (or floc flotation) was tested on a magnetite concentrate that was finely ground to be micron particles, for producing a concentrate with sulphur grade less than 0.1%. After that, slurry dispersing with water glass as dispersant, pyrite fines were subjected to hydrophobic flocculation induced by xanthate and a small amount of kerosene then the slurry was transferred to a flotation cell for recovering the hydrophobic flocs. The experiments carried out indicated that through one-step rougher and two-step cleaner flotation, sulphur grade was reduced from 1% to 0.1%. It has been found that the separation efficiency of the floc flotation process closely correlates with the main parameters of hydrophobic flocculation such as xanthate addition, conditioning time and kerosene addition.

Jan 1, 2006

By F. Tailoka

In order to decrease the voltage required for electrorefining, a recessed electrode cell has been developed in which the anode and cathode have recesses machined into their faces. The anode and cathode plates are separated by a thin refractory cloth and the cell is filled with fused salt. Bismuth containing 10 to 90 % lead with copper and silver as minor impurities has been electrorefmed at a current density of 10,000 to 20,000 Am-2. The cell voltage was between 285 and 635 millivolts and the bismuth was refined to a purity of 99.9 %. Flow patterns were observed in a room temperature model of the recessed channel cell using water and mercury to simulate molten metal and the fused salt electrolyte. The flow in the electrode recesses is characterized by discrete droplets when the liquid flow rate is low and thin streams and rivulets at higher flow rates.

Jan 1, 1995

A rotating-discelectrode system was used to evaluate the electrochemical behaviour of Eu(III) during its reduction in NaCl solutions. The solution pH and NaCl concentration have a great effect on the reduction kinetics. The thermodynamic modelling study also revealed that Eu(III) exists in various forms in NaCl solutions. At a low concentration of NaCl, the predominant species is the free Eu3+. Other Eu-chloro complexes become more predominant when the NaCl concentration increases.

Jan 1, 1992

By W. H. Jay

Sulphide-containing minerals, particularly iron, lead to acid formation. In turn, the acid generates effluents such as copper acid drainage (AMD). The Berkeley Pit in Butte, Montana, USA and Mt Lyell in Tasmania, Australia, represent just two of many sites throughout the world for which acceptable treatment methods are required. In the gold cyanidation process, the presence of copper creates both a significant cost impediment and a potential environmental hazard. The tailings dam failure at Baia Mare in Romania which led to the release of copper and zinc cyanides created a major environmental disaster. The application of non-toxic water soluble polymers and ion exchange resins to selectively recover copper from AMD solutions, and the in-plant treatment of copper cyanide solutions and slurries to recover copper and recycle cyanide to prevent cyanide entering the tailings impoundment will be discussed. The economics of the various processes will be highlighted.

Jan 1, 2003

By Theo Lehner

Nasty, according to the Collins Dictionary, comprises the adjectives: bad, critical, dangerous, dirty, odious, serious, severe, sickening, unpleasant etc. From this we may at first conclude that each individual smelter relying on its own specific business surrounding would have a special definition of its nasties. But common product standards and common metallurgy makes us experience common nasties. To get an idea of possible problem elements we start with the demands on the products: [ ]

Jan 1, 1994

By R. M. Luna-Sánchez

Electrochemical studies, particularly Evans? diagrams, have been employed in hydrometallurgy to simulate and explain the redox phenomena that take place at mineral and metal surfaces during operations such as leaching and cementation. However, despite their utility, in some cases, the combination of the cathodic and anodic branches, determined separately, does not reproduce the chemical environment present when both processes occur simultaneously on a specific surface. In the present paper, limitations of Evans? diagrams are analyzed through two examples: silver sulfide cyanidation and gold cementation on zinc. In both cases, the surface kinetics are sensitive to the local pH and cyanide levels. When the electrochemical oxidation of silver sulfide or the reduction of gold are performed in the absence of its corresponding redox reaction, the local pH obtained does not simulate the real situation and the combined reaction kinetics may be very different from those determined from the Evans? diagrams.

Jan 1, 2003

By I. Van de Voorde

In this paper, results are presented concerning the search to implement Supported Liquid Membranes (SLM) Technology for the recovery of copper, nickel and zinc from electroplating and other effluents to prevent metal waste. A study of the influence of the individual parameters and of their combined effect on mass transfer in small-scale laboratory equipment has been performed, enabling to set forward the appropiate operating conditions for a pilot plant installation. The SLM pilot plant has been tested extensively, including short and long term runs, with real process solutions. It was demonstrated that the SLM technolgy is applicable for solutions containing 800 mg/L of metal ions, but also to the treatment of solutions with low metal content of origin other than plating shops. It was demonstrated by system analysis that the recycled salts are usable to produce metal electrolytes (for example Watt's nickel bath).

Jan 1, 2003

By Edgar Blanco

A thermodynamic and experimental investigation to develop a new process for converting molybdenite concentrate to molybdenum dioxide by a water-vapor oxidation process was carried out. In addition, the behavior of rhenium and selenium in molybdenum concentrate during the process was investigated. The kinetics of the reaction were determined by measuring the weight change of a sample with time in water vapor at temperatures between 700-1000°C. The results were analyzed by a Shrinking Unreacted Core model under chemical reaction control, which showed an activation energy value of 102 kJ/mol. To determine the behavior of rhenium and selenium, their concentrations in the molybdenum sulfide and the product molybdenum dioxide were measured by the use of ICP. While most rhenium remained with the molybdenum dioxide after the water vapor oxidation, almost all selenium volatilized. These results agree with thermodynamic analysis.

Jan 1, 2006

By David A. Army

Many times, the maintenance professionals have been involved in changes to processes or systems. Often they rely on seat of the pants knowledge to determine whether or not they were successful. More often than not, once our attention has been turned to other endeavors, the initiative has floundered. This paper will describe those measures that can be most effectively used to track and manage the success of implementing an improved Work Management System. However, not only will the paper discuss traditional work indicators, it will also explain how to establish the behaviors in the work place that will ultimately ensure successful implementation. Combined with the discussion on indicators will be a discussion on how to tie them to bottom line results and display them in the form of a scorecard. Actual results will be discussed.

Jan 1, 2006

By A. V. Tarasov

Based on the data available in the literature and the practical experience of new metallurgical plants, a method has been proposed and relevant studies conducted for metallurgical processing of zinc sulfide concentrates. Process conditions and parameters have been identified, which ensure high levels of recovery of zinc into solution. This is achieved by leaching concentrates under the normal pressure at a temperature of >90°C in the presence of ferric iron ions. Sulfide sulfur is converted to elemental sulfur in this process. To produce elemental sulfur it is necessary to maintain oxidizing conditions in the system, characterized by a positive Eh value. In order to eliminate the interfering effect of elemental sulfur formed in the process, it is possible to add surfactants into the concentrate pulp. The proposed technology has certain advantages as compared with the high-temperature pressure leaching and is considered as a basic technology to be applied to increase zinc production at one of the Russian zinc plants.

Jan 1, 2006

By Henrique Hesse, Rosana de Cassia de Souza Schneider, Wolmar Alípio Severo Filho, Ezequiel Bavaresco, Rodrigo Klamt, Luciano Roni Silva Lara, Luciano Dornelles

Alkyd resins are used in surface treatment. They are product of the glycerolysis followed by polymerization. In the present work it was studied methods of alkyd resin production from crude glycerol compared with resin produced with pure glycerol. This glycerol corresponds to 10% of the final products in the biodiesel production. The crude glycerol was partially purified with neutralization, flotation and adsorption. The experiments were accomplished with temperature control, inert atmosphere and with several quantities of the substrate. For the products characterization physic-chemistry methods, infrared spectroscopy and hydrogen nuclear magnetic resonance were used. According to the observed results, the resins obtained with crude glycerol have presented similar properties of the classic alkyd resin produced with pure glycerol. The exploitation of the crude glycerol reduces the stages and costs of the process.

Jan 1, 2008

By R. J. Batterham

This paper sets the scene for the Australian-Asian Pacific Course and Conference on Pyrometallurgy for complex materials and wastes. The relentless presence of competitiveness is rehearsed as the source of the current trends towards continuous improvement and benchmarking. While this might be expected to lead to more spending on pyrometallurgy, the opposite appears to be the case. The paper examines the reasons and suggests that we face an increasing challenge for selective developments that can lead to sustainable competitive advantage - both in mineral and in waste processing.

Jan 1, 1994

By Ahmet Geveci

In this work it is aimed to assess the plant analytical data which appeared during efforts to decrease the effect of carry-over slag (basic oxygen furnace slag) that can not be prevented to leak during tapping of steel in the ladles. While the amount changes, carry-over slag that escaped to ladle, consists of appreciable amount of reducible oxides (?FetO? and MnO) which act as oxygen source for steel bath. By using aluminum dross, containing %30-35 metallic aluminum, which is a non-recoverable process outcome (discard) for most of the aluminum factories, slag reduction behavior will be analyzed together with other parameters such as reaction time, initial amount of total Fe+MnO, amount of reducing agent and reducing effect of soluble aluminum in steel bath while obtaining a slag composition which promotes higher desulphurization capacity and inclusion removal for liquid steel.

Jan 1, 2006

By Sunil Jayasekera

This paper describes the results of a study carried out to examine the feasibility of electrolytic recovery of silver from cyanide leach liquor generated from a Western Australian silver mine tailings using a novel high mass transfer electrowinning cell. The proposed circuit involves heap leaching and electrowinning in a closed loop. The filter-press-like closed electrode arrangement of the cell allowed much improved mass transfer of metal ions to the cathode surface, making direct electrowinning of metals from dilute solutions feasible. The tests were conducted both in the laboratory and at large scale using a prototype with ~1.0 m2 cathode area. The results showed that the recovery of silver from as low as 250 mg L-1tenor was feasible. The silver deposit produced with the prototype cell was non-adherent and powdery and could be readily removed from the closed cell. A system was developed so that silver powder was discharged continuously during the run.

Jan 1, 2003

By Hiroyuki Sano

Elimination of heavy metals from the incineration fly ash by the chlorination volatilization method had been already developed and the effectiveness of this method was confirmed by the present authors. In this study, this method was applied to the elimination of heavy metals, mainly lead, from the incineration bottom ash. Since the fly ash contains a large amount of chloride, heavy metals in the fly ash are easily chlorinated. On the other hand, the addition of the chlorination agent is a key point for applying this method to the bottom ash, because it hardly contains chloride. The effects of various variables such as a kind of chlorination agent, adding quantity of it and temperature on the elimination ratio were investigated and the harmlessness of the residual ash was evaluated. The preferable condition was proposed from the recyclability of the bottom ash.

Jan 1, 2006

By Li Qihou

Mono-disperse ZnS and CdS nano-particles were prepared by the homogenous precipitation method and the effects of SO42-,NO3- and Cl-ions on crystalline of particles were investigated experimentally. The results showed that these anions had no influence on the crystalline of ZnS, but different crystalline CdS ultrafine particles were produced in different anion systems, where the blend-type CdS was obtained from natrate or sulphate solution, and wurtzite-type CdS from chloride solution. It was ascribed to the coordination of Cl- and Cd2+ that altered the supersaturation of precipitate ions in the solution, the existing growth units and their connecting patterns, thereby producing wurtzite-type CdS with a more stable structure.

Jan 1, 2006

By Bruce R. Conard

Consideration of environmental and human health issues in metallurgy is growing rapidly. While not all metallurgists need to have detailed expertise in environmental and health questions, they should be aware of the challenges the metals industry faces, be able to interact with colleagues in other sciences and contribute to sound metal resource management. Hydrometallurgists occupy a unique position among metallurgists because of their knowledge of the behaviour of metals in aqueous systems, which are of fundamental importance in understanding environmental chemistry and human toxicology. As a result, hydrometallurgists should more frequently and passionately lend their expertise in assessing environmental and health risks of metals and in helping to develop effective global guidelines, regulations and process and product stewardship strategies, thereby enabling metals to continue their beneficial service to society.

Jan 1, 2003

By Maurizio Marezio Bertini

Ammonia - ammonium sulfate solutions were sparged in a glass reactor with a SO2/O2 gas mixture (2% SO2 and 98% O2) to leach copper from pure chalcopyrite and chalcopyrite concentrate. The SO2/O2 mixture produces higher and faster extractions than O2 by itself. The effect of temperature, particle size and free ammonia concentration was investigated. The fastest and highest recoveries were obtained at 80 oC from a chalcopyrite concentrate with a d80equal to 13 m, with about 83 gpl free ammonia, an average pH equal to 8.75 and a stirring speed of 500 rpm. The extraction process was controlled by diffusion through a product layer, according to the shrinking core model, with an activation energy of 41 kJ/mole.

Jan 1, 2003

By S. Vellinga, G. H. R. Janssen, C. J. N. Buisman, C. F. M. Copini

Non-ferrous metallurgical plants are often confronted with the need to neutralize bleed streams or effluents containing sulfates. The treatment of these streams could produce large amounts of gypsum. With a biological sulfate-reduction process, the production of gypsum is avoided and the metals can be recovered as sulfides. In this paper, the biological treatment of an industrial stream is presented. The bleed solution from a roaster gas scrubber was treated by means of a two-step process. First, the acid was neutralized with calcine. The resulting zinc sulfate solution was converted to ZnS with bacteria using PAQUES-THIOPAQ® technology. The precipitated ZnS was de-watered to 70 wt% solids, and was returned to the roasters. The quality of the effluent stream complied with the environmental regulations.

Jan 1, 2000