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By Steven E. Follin

In-situ leaching is commonly used to recover uranium from low-grade deposits in sandstone formations. Acceptable recovery rates can only be obtained if the formation retains its permeability during leaching. Field experiences indicate that microbial growth, stimulated by the leaching pro- cess, can cause plugging problems. To investigate this hypothesis, leach solution and solid samples from well casings and submersible pumps were obtained from four in-situ mining sites. Chemical and microbiological analyses were performed. Bacillus species, Micrococcus species, pseudomonads, and xanthomonads were isolated from these samples. A mixed culture of these organisms was inoculated into a uranium core that was being leached in the laboratory. The permeability of this ore sample decreased to one-third its original value after 16 days. The addition of hydrogen peroxide (0.2 g L-1) to the leach solution killed the microbes and restored the permeability to its original value. This suggests that periodic injection of hydrogen peroxide into production wells may reduce microbial plugging in these wells and the immediate surrounding formation.

Jan 1, 1985

By J. L. Delplancke

During copper electrowinning in sulphate electrolyte, intense oxygen evolution takes place at the anode. Lead alloy anodes are progressively replaced by dimensionally stable anodes in order to avoid the cathode contamination by dissolved lead. The electroactive coating of these anodes has to be as cheap as possible, adherent to the substrate, electrochemically stable and has to be efficient at high current density and high temperature. This requirement is even demanding in case of copper electrodeposition for the production of thin copper foils for the electronic industry. The production of thin (20 µm thick) copper foils for the printed circuit boards requires high purity copper electrodeposited at a current density as high as 7,000 A/m2. The choice of a long term coating composition is driven by economics. The purpose of this paper is mainly to review the anode compositions suitable for copper electrowinning and for copper electrodeposition at high current density. A short description of preliminary results obtained with a new anode coating on a titanium substrate is also presented.

Jan 1, 1999

By S. Bagchi

The LaNi5-xMnx-hydrides have potential applications in cryocooling devices for non-mechanical method to compress hydrogen gas. Thermal aging behavior of LaNi5-xMnx-hydrides of compositions x=0.4 and x=1.5 has been investigated. The hydriding properties of the La1.02Ni4.6Mno.4 alloy do not change significantly after thermal aging at 453K for 260 hours. X-ray diffraction analyses of this aged alloy do not reveal the presence of any new phases but the Bragg peaks become broader. Line profile analyses show anisotropic microstrains with an average <e2>1/2 value of -5x103. Thermal aging of the other hydride, LaNi3.5Mn1.5 hydride, at 623K for 280 hours, showed significant disproportionation; the hydrogen capacity reduced significantly from an H/M value of 0.75 in the activated condition to -0.15 after aging. X-ray diffraction analyses showed disproportionated lanthanum dihydride, metallic Ni, and Mn phases. The Bragg peaks were very broad indicative of microstrains or small crystalline domains.

Jan 1, 1997

By Daojin Cao

Aiming at many controversial reports on Raman spectral pattern of octamolybdate ion in aqueous solution appearing in the literature, a new method for the establishment of corresponding relation between Raman spectral pattern and chemical components of aqueous molybdate solution was put forward using spectroscopy measure and component analyses of saturated solution of ammonium octamolybdate hydrate known structure. It was found that the main characteristic of Raman spectral pattern of the saturated solution was described as the same ?double-peaks, hereinto a weak peak at the boundary? as some literature, but chemical components of the saturated solution were affirmed to be octamolybdate ion (Mo8O264-) and double protonated heptamolybdate ion (H2Mo7O244-), which were in equilibrium in aqueous solution each other. The authors propose that the pattern of the saturated solution can be regarded as the standard pattern of primiparous octamolybdate ion during acidified molybdate solution. It is satisfying that the standard pattern is applied to the identification of primiparous octamolybdate ion during acidified molybdate solution.

Jan 1, 2006

By Brady Butler

Many high capacity metal hydrides exhibit a high degree of stability in the hydrogenated state. This stability leads to a number of significant design problems with regard to the low temperature kinetics and thermodynamics of dehydrogenation. Nanometric metal hydride materials provide a promising route for increasing the reaction kinetics while altering the thermodynamic stability of the material. The use of nanometric metal hydride materials for hydrogen storage has largely been absent because of the difficulties associated with the synthesis of these materials. In this paper, research results on the synthesis of lithium based metal hydrides by vapor phase reactions are presented. The lithium based compounds that have been made in our lab include nanosized powders of metallic Li, Li₃N, LiNH₂ and LiH. The vapor phase process has also been used to custom engineer Li-based materials with other alloying elements or doping elements. The dependence of the characteristics of these materials on synthesis process parameters is studied. The effects of nanoscaled particle sizes on the kinetics of dehydrogenation and hydrogenation reactions are also explored.

Jan 1, 2006

By Hong Yong Sohn

A thermodynamic and experimental investigation has been performed to develop a new process for converting sulfur dioxide to elemental sulfur by a cyclic process. The most promising new process is a cyclic reaction scheme involving calcium sulfide and calcium sulfate. In this process, the reaction between sulfur dioxide and calcium sulfide produces elemental sulfur vapor and solid calcium sulfate. The latter is reduced by a suitable reductant such as hydrogen to regenerate calcium sulfide. &apos;Experimental results showed that up to 60 % of calcium sulfide powder was converted to calcium sulfate in 10 min at 1153 K under a sulfur dioxide partial pressure of 25.8 kPa. More than 95 % of nickel-catalyzed calcium sulfate powder was converted to calcium sulfide in 20 min at 1123 K under a hydrogen partial pressure of 86.1 kPa, water vapor being the only gaseous product. Sulfur dioxide-containing streams from certain new sulfide smelting plants contain much higher partial pressures of SO2. The rate of the first reaction is expected to be accordingly higher than in the test conditions reported in this paper.

Jan 1, 2002

By James D. Navratil

The mineral magnetite, or synthetically prepared iron ferrite (FeO?Fe2O3), has been used to separate a wide variety of substances, such as dissolved metal species and particulate matter, from wastewater. In the absence of an external magnetic field, activated magnetite readily adsorbs numerous metal species including actinide elements. In the presence of the external magnetic field, enhanced capacity was observed in using supported magnetite for removal of actinides and heavy metals from wastewater. The enhanced capacity is primarily due to magnetic filtration of colloidal and submicron particles along with some complex and ion exchange sorption mechanisms. The removal of the magnetic field and use of a regenerating solution can easily regenerate the loaded magnetite. The process has recently been tested for the removal of other metal ions including cobalt and iron. This paper will review previous work on the use of iron oxides for wastewater treatment and discuss the development and potential of the magnetic filtration/sorption process for wastewater treatment applications in hydrometallurgy.

Jan 1, 2003

By Alan M. Peel

"Over the past years there has been an increasing demand by aluminium cast -house operations to obtain a greater return from their existing installed plant. This has included increasing existing furnace production capacity to match new and higher downstream production requirements, reducing melt losses and more efficient alloying.The paper discusses how Electromagnetic Pumping, which was developed for the combined purpose of;1. Melting light gauge aluminium scrap with a reduced melt loss and; 2. Effective circulation of the aluminium melt,has established its self in recent years, as an effective means of satisfying many of these industry requirements, but how it has also provided many other additional operational benefits to the aluminium cast house.The paper will discuss operational performance of the system with a particular emphasis on its effect on the metal bath quality (alloying, chemical and temperature homogeneity), metal recovery and increased production due to the high circulation.The technology having now been adopted by a variety of industry leaders has a number of prominent references and the paper will discuss the operational benefits and experiences from some of these."

Jan 1, 2000

By Hiroshi Nakazawa

An acid mine drainage in abandoned Horobetsu mine in Hokkaido, Japan, contains arsenic and iron ions; total arsenic ca.10ppm, As(III) ca. 8.5ppm, total iron 379ppm, ferrous iron 266ppm, pH1.8. Arsenic occurs mostly as arsenite (As (III)) or arsenate (As (V)) in natural water. As(III) is more difficult to be remove than As(V), and it is necessary to oxidize As(III) to As(V) for effective removal. 5mL of the mine drainage or its filtrate through the membrane filter (pore size 0.45m) were added to arsenite solutions (pH1.8) with the concentration of 5ppm. After the incubation of 30 days, As(III) was oxidized completely with the addition of the mine drainage while the oxidation did not occur with the addition of filtrate, indicating the microbial oxidation of As(III). In this paper, we have investigated the microbial oxidation of As(III) in acid water below pH2.0.

Jan 1, 2006

By A. M. Strachan

The arising and behavioural pattern of polonium-210 in the Capper Pass & Son Limited non-ferrous metal smelting and refining circuit is briefly discussed. The process developed for the removal of polonium from lead, solder and bismuth is discussed in detail, together with the essential personnel safety and environmental protection precautions which must be taken during the refining and subsequent storage of the active dross.

Jan 1, 1992

By Bora Derin, Sertac Yazici, M. Seref Sonmez

"In this study, the recycling conditions of waste liquor obtained after the production of tungsten boride powder from calcium tungstate by self-propagating high temperature synthesis (SHS) and the following hydrochloric acid leaching were investigated in detail. Environmentally unfriendly and extremely acidic (pH~ -0.3) liquor consisting of calcium, magnesium, and boron ions was treated with 1 M sodium carbonate solution to precipitate magnesium carbonate and calcium carbonate phases. The obtained amorphous precipitates were heated up to the temperature of 400°C for re-crystallization. As a result, MgO, CaC03 and CaMg(C03)z phases were obtained, while sodium, boron, chlorine ions were remain in the solution. The present study is still in progress.IntroductionSelf-propagating high temperature synthesis (SHS) is one of the techniques used in the production of a variety of advanced ceramics, inter-metallic, organic and inorganic compounds, oxygen free single crystals, and polymers [ 1, 2]. The reaction becomes selfsustaining and propagates in the reactant mixture, after initiation in SHS process. SHS products may contain the mixture of several unwanted compounds and elements. Therefore following acidic leaching process may be needed to purify the target product. In the previous study, calcium tungstate (Ca W04), magnesium (Mg) and boric acid (B20 3) mixture were reacted to produce tungsten boride powder by SHS process according to the Reaction 1. Then, magnesium and calcium containing byproducts (i.e. MgO, Mg3B206 and Ca3B206) found in the SHS product were leached out by using concentrated hydrochloric acid (HCl) solution to obtain pure tungsten boride powder [3].Ca W04 + 0.5B203 + 4.5Mg = WB + 4.5Mg0 + Cao (1)After the leaching, filtrate solution consisting of different amounts of magnesium, calcium, and boron requires additional treatment for the environmentally acceptable disposal.Several works were carried out about magnesium precipitation conditions and kinetics from brines. Rabadzhieva et al. investigated the precipitation of Mg(OH)z from brines by using NaOH as well as caustic soda [ 4]. Turek ve Gnot investigated the precipitation efficiency of Mg(OH)z for the temperature range between 10-40°C, while the reaction was kinetically experimented by Alamdiri et al [5, 6]. Homogeneous precipitation of nesquehonite (MgC03.3H20) by the reaction of MgCli with (NH4)2C03 in supersaturated solutions and factors that influence the precipitation of MgC03.3H20, such as reaction temperature, initial concentration, stirring speed, titration speed, equilibration time, have been studied by Wang et al [7]. The precipitation of Mg(OH)z by calcium hydroxide from aqueous solutions was studied by Baird et al. [8]. Stratful et al. focused on conditions influencing the precipitation of magnesium ammonium phosphate from wastewaters [9]. 1031"

Jan 1, 2011

By Guanghua Wen, Jian Li, Mingmei Zhu, Fei Xiong, Shengjian Cao

"Small inclusions removal from molten steel in a continuous casting tundish by gas bubbles, which were generated in the turbulent flow region by introducing inert gas, was analyzed theoretically and the inclusion-bubble adhesion and flotation process was also observed by high-speed photo-graph in water model. Results showed that small inclusions in the range of 20-50µm removal from molten steel by bubbles flotation involves three stages: contact, adhesion and flotation. The inclusion-bubble adhesion processes include two ways: inclusions adhering to the upper part of the bubble and inclusions adhering to the lower part of the bubble. As the bubble floats up, the number of inclusions adhering to the bubble are increased. The proper size of bubbles, which could enhance small inclusions removal efficiency, should be controlled in the range of 1-2mm.IntroductionReducing inclusions content in molten steel is a very important way to improve quality of steel, and one of the main tasks in steel making process.A variety of methods have been used for inclusions removal in molten steel. At present, the main approaches to remove inclusions are gas stirring, slag cleaning, filtering, centrifugal separating, and by means of ultrasonic or electromagnetic field. Among these techniques, gas stirring is the most widely and effectively method for inclusions removal. Inclusions in molten steel will be aggregated and generated to form larger size inclusions, and subsequently floated to the surface of molten steel by buoyancy; meanwhile, some inclusions will be adhered to bubbles and floated together to metal-slag interface where inclusions are absorbed by the covering slag layer. Some research work showed that flow behaviors of small bubbles are different from that of big ones [1-2], and smaller bubbles are more efficiency for fine inclusions removal in molten steel.There are many methods to generate bubbles. During steelmaking process, highly turbulent flow in the ladle shroud can split introduced inert gas into small bubbles, which enhances the removal of fine inclusions from molten steel. Turbulent flow of molten steel injected into tundish from ladle shroud has a high speed and it is a strong turbulent area in continuous casting. The gas can be introduced into the shroud below the slide gate. The high turbulence flow would break up the gas into small gas bubbles. Fine inclusions will be easily adhered to small bubbles and subsequently floated to the surface of molten steel. Generation of small bubbles in ladle shroud have been studied in some literatures [3-4]. Some research have analyzed the fine inclusions removal with injecting gas from the ladle shroud by mathematical simulation, and the results show that the refining method can obviously improve the removal efficiency of fine inclusions in tundish [5-8]."

Jan 1, 2013

By C. Liliane Carvalho

In the current study, bio-oxidation tests were carried out in shaking flasks with a flotation concentrate containing the sulphides pyrite, arsenopyrite and gudmidite. The tests were performed with mesophilic microorganisms (At. ferrooxidans) at 30 °C and also with the moderate thermophile S. thermosulfidooxidans, at 50 °C. The effects of (i) previous adaptation of the microorganisms to the concentrate, (ii) ferrous iron concentration and (iii) pulp density (2%, 4% and 6% (w/v)) on the dissolution of the sulphide were studied through arsenic extractions. S. thermosulfidooxidans was more sensitive to the pulp density in comparison to At. ferrooxidans as a reduction in sulphide oxidation was observed with the increase in the solid content to 6%. Therefore, the mesophilic strain was selected for further work, which comprised a rolling bottle experiment at 10% solids. After 40 days of bio-oxidation, the solid material was subjected to cyanidation, which revealed 85% gold extraction as compared to 21% from the original concentrate. The antimony sulphide grains in the bio-oxidized product showed similarity to what was observed in the original sample, suggesting such particles were not susceptible to the bio-oxidation process.

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By Christopher Solnordal

A mathematical model was developed to simulate the performance of the reaction shaft at BHP-Billiton?s Olympic Dam copper flash smelter. In order to have confidence in the predictions of the mathematical model, validation was performed by comparing and reconciling the predictions from the model with the results from a campaign of sampling and plant measurements. The model was based on the computational code CFX4.4 utilizing a combustion sub-model purpose-built by CSIRO. The combustion sub-model employed the concept of a composite particle which contained the three components of the solid charge: concentrate, flux and returned dust. Plant measurements were made and samples taken immediately below the burner and through a port halfway down the reaction shaft. Parameters measured included temperature, solid loading and SO2 concentration in the gas. Comparison of the measured and predicted values then showed that: predicted far field gas temperatures were within ±50C of measured values; predicted temperatures in the central plume were lower than measured, and, the predicted plume width was slightly smaller than measured. An optimum composite particle size of 19 m was identified for use in future modeling work at Olympic Dam.

Jan 1, 2006

By Osamu Yamamoto

In antibacterial evaluation of carbon-ceramic composites, we prepared two type composites with emphasis on carbon-ZnO system; one was porous carbon materials containing ZnO nano-particles and another was porous ZnO coated with carbon thin film. Porous carbon samples containing ZnO at highly dispersed state were prepared by carbonizing the resin exchanged by Zn2+ ion. Porous ZnO coated with carbon thin film was obtained by the pyrolysis of poly (vinyl alcohol). Antibacterial activity of these composites obtained was evaluated by measuring the changes in electrical conductivity with bacteria growth. The antibacterial activity on the composites increased with the increase of t he amount of ZnO in composite and decreased with the increase of carbonization temperature. The antibacterial activity for Staphylococcus aureuswas found to be stronger than that for Escherichia coli. No activity of the carbon samples without ZnO was observed. The occurrence of antibacterial activity was supposed to be due to the generation of hydrogen peroxide from ZnO in composite. In the present work, antibacterial activity of carbon-ZnO composites was studied in the details.

Jan 1, 2006

By Roberto Parra

The operational control in a Flash Smelting Furnace is based on the mass and energy balance of the chemical and mineralogical composition of the concentrates. It is well known that many troubles in the dust formation and slag quality occur without a clear correlation to a specific process parameter such as the matte grade or heat balance. This paper outlines two new considerations that could both help improve the entire quality of the process: blend characterization and versatile slag composition control. Related to the blend control, laboratory scale study has shown that the magnetite and dust formation don&apos;t have a linear behavior with the weight proportion of the blend and some optimal blends of2 or 3 types of concentrates can be identified. Related to the control of stag composition, the quantification of the slag liquidus temperatures and viscosity could be an effective operational tool for both for ferrite and fayalite slag that can also directly help deciding the blending parameters. From these viewpoints the benefits of the combination of these two approaches for high temperature operation is discussed. Keywords: Optimization, Copper concentrates, Flash combustion, Blends, Slag composition

Jan 1, 2003

By J. Sjöblom

New copper and nickel processes, flash converting and DON, direct high-grade nickel matte smelting, have been developed in order to replace the conventional and not so environmentally friendly PS-converting process. With a laboratory scale laminar-flow furnace the combustion reactions of sulfidic feed particles can be investigated under simulated flash smelting conditions. In the present study, finely ground and screened feed fractions of a copper matte and a nickel matte were flash oxidized in a laminar-flow furnace. The experiments were carried out using 20, 21 vol% and 75 vol% O2 in nitrogen, at temperatures 1100 and 1300 °C and reaction zone length of 7.5-16 cm. The samples were quenched in a water film after a specified reaction time. The matte particle reactions were stopped after short residence time intervals in order to obtain a better understanding of the reaction mechanisms. Chemical analysis was used to determine oxidation degree, and optical and scanning electron microscope combined with energy dispersive analysis was used for characterization of the reacted particles. On the basis of the experimental results the reactivity of the mattes is discussed and possible reaction and dust formation mechanisms are considered.

Jan 1, 1999

By J. Antonio Barrera-Godinez, S. E. James, J. Sun

The solvent extraction separation of iron from a zinc sulfate medium using DEHPA was investigated. After loading, the ferric ions were reduced in the organic phase using metallic zinc. The ferrous ions produced could be easily stripped into a sulfate solution with pH values in the range of 1.4 to 2.0. The small, laboratory scale pilot system used in this study allowed for continuous cycling of the organic and strip aqueous solutions. It was possible to establish and evaluate a series of steady state conditions under selected operating paiameters. The effects of processing parameters such as solution chemistry, flow rates, zinc metal loading and pH on iron recovery and efficiency were also evaluated. Under proper conditions, it was possible to remove about 5 g/L iron from the organic phase in one stage and to produce a concentrated iron sulfate strip solution containing ferrous ion concentrations in the range of 90 to 130 g/L. Preliminary feasibility tests were also made on electrowinning metallic iron from the strip solutions and crystallizing ferrous sulfate as a means of making a marketable iron product.

Jan 1, 2000

By K. O. Fagerlund

Theoretically and experimentally determined copper matte settling rate in iron silicate slag has been discussed. Separation and settling rate measurements of sand, homogenised slag and 25%Cu concentrate, 63%Cu industrial, and 71%Cu synthetic copper mattes were carried out by mixing crushed slag and matte samples with silica sand in an alumina crucible and melting at 1300-1350°C. Two different types of slag compositions were employed, with Fe/SiO2-ratio 1.4 and 1.7. The separation rate was followed by taking samples from the .melt. As expected, the settling rate of copper matte in fayalite slag depended on the slag composition, where the increasing silica decreased the matte settling rate. Microanalysis of solidified slags showed that the rate of separation of low grade matte was low compared with high grade matte and the presence of a very small size fraction of matte droplets in slag remained unsettled in stagnant fluid. The production of sulfur dioxide gas inside the molten bath was found to be possible up to a certain iron sulfide content in the matte. Also, copper matte settling rates in industrial furnaces have been discussed.

Jan 1, 1999