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By Bernard Bonnetot

The potentialities of hydrogen storage using borohydrides are presented and discussed especially in regard to the recoverable hydrogen amount and to the recovery conditions. A rapid analysis of storage possibilities is proposed taking in account the two main ways for hydrogen evolution: the dehydrogenation obtained using thermal decomposition of borohydrides or the hydrolysis of solid or dissolved borohydrides. The recoverable hydrogen is related to the dehydrogenation conditions and the real hydrogen useful percentage is determined for each case of use. The high temperatures required for dehydrogenation, even using catalyzed borohydrides, lead to poor outlooks for this storage technique. The hydrolysis conditions fix the yield of the recovered hydrogen and rule the storage capacity of the dissolved borohydride, the "fuel".

Jan 1, 2006

By Xie Gang

The leaching experiment used by bacteria on the low grade sulfide copper ore which is difficult to leach was carried out. Some leaching bacteria which have good physiological and leaching activity were isolated and domesticated, and were adapted to leaching ore. The effective domesticated method was put forward. Some technological parameters such as ore acidification, potential controlling, leaching method, ore granularity, leaching acidity, leaching liquid quantity and acid consumption were obtained by column experiment and leaching ore in situ under the ore well. The results show it could leach 30.62% of copper from the low-grade sulfide copper ore within 24 weeks by column leaching method, and the bioleaching rate of copper is 22.83% by leaching in situ under the ore well in 8 months.

Jan 1, 2006

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified.

Jan 1, 2006

By Beatriz Ramírez

Xanthates are anionic collectors normally used in flotation devices to modify the hydrophobic surface of sulphide minerals. Xanthates are heteropolar compounds and in aqueous media they dissociate into ionic xanthate and alkali-metal ions; nevertheless their behaviour is not well understood yet. This work characterises the six reactions describing the decomposition of the ionic xanthate in aqueous media by analysing the set of spectra from a UV- Spectrophotometer. Results show the effect of pH on the stability of certain compounds which can be useful to explain the relationships among xanthates and the hidrophobicity of some surfaces (or ions dissolved).

Jan 1, 2006

By W. Marnette

Norddeutsche Affinerie is the largest West European copper producer with an annual output of more than 350,000 tonnes of refined copper, about half of which is produced from copper concentrates. However, in addition to concentrates, Norddeutsche Affinerie processes secondary raw materials and recycling materials which contain a combination of copper and lead. These materials were previously treated in blast furnaces, a technology which has meanwhile been superseded at NA by the electric furnace process, primarily owing to the necessity of complying with the increasingly stringent requirements for environmental protection.

Jan 1, 1994

By O. C. Rojas

Improvements and modifications on lay out and process, from 1997 till 1998, are presented. Based on a Teniente Converter, started up 1993, a Strategic Development Plan was structured to increase the production efficiency and comply with the enviromental regulations, too. It considered the oxygen supplies to the Teniente Converter and Peirce Smith converters; reverberatory furnace shut down as a smelting unit; and the Teniente converter slag treatment through a combined process between a Slag Settler furnace and flotation. Also it included the off-gas handling and treatment.

Jan 1, 1999

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 Tang Chaobo

Employing manganese carbonate ore and zinc oxide dust as material, Mn-Zn compound oxide powder for soft magnetic ferrite was prepared by a serial methods, as follows: leaching by using sulfuric acid, removing aluminium and silicon by neutralization and flocculation method, using ammonium bicarbonate to co-precipitating Mn and Zn, calcinations and washing to removing impurity content. The optimal technical condition was obtained by experiments. The difficulty of removing impurity such as Si, Al, Ca, Mg, from leaching solution was solved. The impurity content in the production meets with the preparation standard of high quality soft magnetic ferrite. The compound oxide powder obtained in the experiment was made into lower power loss magnetic ferrite, the quality of magnetic ferrite meet the standard of PC40 which was established by TDK corporation.

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