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By Corby G. Anderson

Hydrometallurgical technology for the pretreatment of refractory gold concentrates has been developed at Sunshine Mining and Refining Company. It employs a patented nitrous-sulfuric acid pressure leaching process which' was proven industrially at the Sunshine refinery. Additionally, pretreatment for removal of antimony and some other impurities is done with alkaline sulfide leaching. This paper will discuss the successful application of these two technologies for pretreatment of a refractory gold concentrate prior to CIL gold recovery. A complex gold concentrate composed of pyrite, arsenopyrite and stibnite was tested. Results of antimony leaching in alkaline sulfide media will be discussed including some details of a novel and selective recovery method for gold leached by polysulfide or thiosulfate" Also, the factors important in and the results of the application of nitrogen species catalyzed pressure leaching to refractory gold concentrates will be detailed.

Jan 1, 1996

By Ted H. Eyde

Natural Zeolites are a less expensive and in certain applications a superior alternative to organic ion exchange resins. Mining and metallurgical waste streams are difficult to treat because the effluents which contain potentially valuable heavy metals such as copper, lead, and silver are often highly acidic and contain significant quantities of suspended solids. Under rigorous operational conditions, certain natural zeolites can remove the metals, which if desired can be recovered by either elution or conventional smelting techniques. There are significant differences in cation exchange rate, selectivity and capacity as well as resistance to either high or low pH, blocking cations and tolerance to elevated or depressed temperature and pressure not only between different zeolite minerals but between the same mineral from different deposits. Applying natural zeolites to the treatment of mining and metallurgical waste streams depends on matching the specific zeolite to the effluent by characterization of the zeolite minerals.

Jan 1, 1993

By Richard H. De Voto

The McDonald Gold Project and two satellite gold deposits near Lincoln, Montana, contain at least 9.9 million ounces of gold and 30 million ounces of silver. The McDonald gold deposit alone contains 7.2 million ounces of gold reserves that can be open-pit mined and processed by cyanide heap leaching at a projected cash operating cost of $190 per ounce. The deposit is predominantly oxidized with no chance of acid production, and can be mined, operated, and reclaimed with minimal permanent environmental disturbance other than the creation of an open pit filled with a fresh-water lake which would support trout. The Seven-Up Pete Joint Venture, the owner of the McDonald Gold Project, commenced permitting of an open-pit, heap-leach operation in November 1994. In 1998, Montana citizens passed an anti-cyanide, open-pit mining initiative, 1-137, which banned any new open-pit gold mine which uses cyanide processing, The Venture has conducted extensive studies, including metallurgical testing of the treatability of McDonald ores with alternative lixiviants, and has determined that all other mining and metallurgical treatment systems are vastly uneconomical in the recovery of gold and silver from the McDonald deposit. Therefore, the Venture's proposed open-pit mining and cyanide heap-leach processing is the only technology that can be applied economically to the McDonald deposit. Further, the analyses convincingly demonstrate that the proposed open-pit, cyanide heap leaching technology results in maximum resource conservation of this valuable and unique deposit and poses far less risk to human health and the environment than any of the alternative technologies.

Jan 1, 1998

By Ian M. Ritchie

Right across the universities of the developed world, the traditional disciplines of physics and chemistry are losing ground. Extractive metallurgy, which depends so heavily on chemistry, is also contracting despite a clear need for people with this kind of training in the mining industry. Reasons for this loss of popularity are discussed in this paper. High on the list is one of image. The extraction of metals is widely seen as a dirty, polluting, sunset industry which involves working in remote and uncomfortable corners of the earth for inadequate compensation. Ways in which the image problem can be overcome are considered. It is concluded that a concerted effort needs to be made by the universities and industry to redress this situation. The importance of extractive metallurgy, both now and in the future, when a greater emphasis will be placed on sustainability and recycling, needs to be stressed. In addition, courses need to incorporate training for a career path that leads on beyond extractive metallurgy.

Jan 1, 2003

By Jari Aromaa, Olof Forsen

"Oxygen evolution by decomposition of water is the main anodic· reaction in sulphuric acid solution. Traditional anode materials have been relatively low-cost lead alloys, though the active lead dioxide layer has a high oxygen evolution overpotential. This causes a significant increase of cell voltage. To lower total energy use in metal production, electrocatalytical properties or corrosion resistance to decrease replacement costs must be improved. Addition of an catalyzing ion will decrease oxygen evolution potential. The effective area of an anode increases by calcium additions and by producing anodes with fine microstructure. Remelting and rapid quenching is possibly a method that is economically feasible and technically simple enough to be adopted.IntroductionPermanent anodes are widely used in several electrochemical processes and cathodic protection applications. The permanent or ""inert"" anodes can be either massive or coated anodes. The massive anodes are metals, like lead alloys, or non-metals, like magnetite, graphite or ferrite. The coated anodes are made of a valve metal base (titanium, niobium or tantalum) coated with an electrochemically active coating. The purpose of anodes is to supply current to the electrochemical cell. A vast number of materials and their combinations are electrical conductors and may hence be used as anode materials. However, good anode materials must survive in aggressive environments and also be able to pass high current densities. These opposite requirements restrict the amount of possible materials. Generally, an useful anode material must meet three requirements, electrical conductivity, electro catalysis and stability. Good electrical conductivity is essential for energy efficiency. Good electrocatalytical properties are essential to improve product yield. Long term stability is also an important property, because electrode wear and corrosion may cause product contamination, increasing energy consumption and material and labor costs due to need of periodical maintenance. Electrical conductivity and electrocatalytical properties are more widely studied subjects than long term stability of anodes, and a good amount of information about these two subjects can be found in the open literature. Wear and corrosion mechanisms of the anodes vary depending on the operational conditions, i.e. concentration of different species, temperature and operating current density."

Jan 1, 1997

By Hideyuki Itou

Municipal wastes are mainly incinerated in Japan. Both bottom ash and fly ash from the incineration treatment are smelted recently to decrease the volume. Direct smelting of municipal wastes is also becoming popular. The smelting treatment generates fly ash which contains concentrated heavy metals such as Zn, Pb and Cu, and the harmfulness is causing concern. The smelter fly ash is mainly landfilled after stabilization. An effective treatment process of the smelter fly ash is required to recover the metals. For the treatment process, an application of chloridizing volatilization technique is considered. Chloridizing volatilization experiments were carried out to determine the effects of various factors on the volatilization behaviors in this study. A pretreated ash was mixed with a main raw material which mainly consists of hematite. Calcium chloride water solution was added into the mixture. The mixture was pelletized, dried and used as samples for the volatilization experiments. The sample was placed in the reaction tube heated in an electric resistance furnace. 5%02-95%N2 gas with controlled humidity was introduced into the reaction tube. Effects of humidity in the carrier gas, addition of calcium chloride and mixed ratio of the ash to the main raw material were investigated on the volatilization of Zn, Cu and Pb. To determine the volatilization behavior, samples were taken from the furnace at specified temperatures on the heating stage. In addition, experiments at specified holding temperatures for 15 minutes with shortened heating time were conducted. The two series of experiments revealed the effect of heating temperature on the volatilization behavior of Zn, Cu, Pb and Cl.

Jan 1, 2006

By T. P. R. de Jong

Dual energy X-ray transmission imaging is extensively applied for safety luggage inspection. Its advantages are its rapid scanning rate (25 to 100 cm/sec) at approximately I mm resolution and simultaneous thickness independent metal identification. This is especially advantageous for secondary scrap metal inspection and automatic sorting. Other applications include metal product inspection, bale control, and waste processing. Recent progress in development of an automatic on-line sorter for bulk solids is presented and discussed. Besides various non-metal applications (solid fuels, wastes etc.) it appeared particularly effective in light metal sorting. As inspection tool better control of difficult to monitor solid bulk streams, batteries, bales and other related metals becomes possible.

Jan 1, 2003

By Yuuki Yoshida

Electrolytic manganese dioxide, EMD, is the positive electrode material of primary batteries and the raw material of LMC used as the positive mass of lithium ion batteries and is currently produced by anodic deposition on and harvesting from a titanium anode in acidic manganese sulfate solutions prepared by dissolving high purity of manganese sulfate into sulfuric acid solutions. This paper presents an alternative method of EMD production using a novel anode, Mn2O3 coated titanium, at lower operating temperature than the current process to explore a possibility of manganese recovery from zinc electrowinning solutions. The Mn2O3/ Ti anode prepared by thermal decomposition of a precursor solution containing Mn (II) showed the anodic deposition of MnO2 by constant current electrolysis and the current efficiency was 95% in maximum, while the current efficiency and the crystallographic structure of deposited MnO2 depended on the current density, the electrolysis time, the bath temperature, and the concentration of Mn(II). The deposited MnO2 was successfully harvested from the anode and the recovery rate was 98%.

By S. B. Johnson

Keywords: Spray, Aluminum, Simulation A stochastic, droplet-resolved model has been developed to describe the behavior of a binary aluminum alloy spray during the spray-rolling process. In this process, a molten aluminum alloy is atomized and the resulting spray is deposited on the rolls of a twin-roll caster to produce aluminum strip. The one-way coupled spray model allows the prediction of spray characteristics such as enthalpy and solid fraction, and their distribution between the nozzle and the deposition surface. This paper outlines the model development and compares the predicted spray dynamics to PDI measurements performed in a controlled configuration. Predicted and measured droplet velocity and size distributions are presented for two points along the spray centerline along with predicted spray averaged specific enthalpy and solid fraction curves.

Jan 1, 2005

By V. A. Shumsky, I. P. Polyakov, N. M. Ospanov, M. A. Lyamina, N. N. Ushakov

Studies on the kinetics of the competitive processes of PbS volatilization and PbS oxidation, as applied to the heat and mass transfer conditions in the flame of the Kivcet furnace, revealed that the rate-determining factor is the supply of heat. Therefore, low yields of fume in the autogenous flash smelting of lead sulphide feeds are noted despite the high volatility of PbS at 1,300-1,400°C. Dust formation in the autogenous flash smelting of Kivcet-smelters does not exceed 5-7%, of which fumes amount to ~ 80%. Using extra fuel during autogenous smelting involves the mismatch of the sulphide oxidation rate and the release of heat in the flame, and increases the fume yield. This is a major cause of the high dust formation in pilot plant trials. The analysis of dust formation in the Kivcet smelting of oxidized lead feeds in an industrialscale smelter shows an overall increase of dust formation (up to 10% of the feed), with fumes constituting ~ 80% of the dust. A pronounced increase of the zinc component of the fumes is also noted. Lead

Jan 1, 2000

By T. Ranki-Kilpinen

In the flash smelting technique, developed by Outokumpu Oyj, off-gases with dust load are directed into the heat recovery boiler (HRB). As the temperature decreases, metallic sulphates become thermodynamically stable. Sulphation of oxidic particles initiates. The release of heat causes an increase in particle temperatures, and soft sulphated particles can stick to the heat transfer surfaces. Dust accretion may form and cause operational problems. The objectives of the project are to study sulphation reaction mechanisms and kinetics of flue- dust particles under HRB conditions, and get more information for the flue-dust treatment possibilities. The sulphation behaviour of synthetic Cu2O particles (37-53 pm) was studied using a fluid-bed reactor of laboratory scale. The experimental parameters in the latest campaign were oxygen and sulphur dioxide contents of 2.5-10 vol-% 02 and 40-60 vol-% SO2 respectively and temperatures of 600-660°C. Samples were examined microscopically (SEM+EDS) and chemical analysis were conducted. The sulphation rate was found to have a maximum at the certain temperature, which was dependent on the gas SO2 content. Regardless of the level of SO2, a rise in oxygen content promoted sulphate formation.

Jan 1, 2002

By Manuel Pérez-Tello

An experimental study on the oxidation of chalcopyrite (CuFeS2), pyrite (FeS2), covellite (CuS) and chalcocite (Cu2S) particles was conducted by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Oxygen concentration in the process gas was set to 40 and 70% by vol. and a heating rate of 40 °C/min was used. Response variables included: the temperature of incipient reaction, the total exothermic heat of reaction, particle mass, morphology, and mineralogy of the reacted particles. Based on the experimental data and phase stability calculations, reaction mechanisms were proposed to represent the behavior of the particles during oxidation. The reaction mechanisms were verified by X-ray diffraction (XRD) analyses of the oxidized particles, and by thermochemical and mass balance calculations to reproduce the DSC and TGA thermograms. Overall kinetic models were developed to represent the evolution of the exothermic heat of reaction for each mineral as a function of time. Experiments conducted with copper concentrate particles containing the minerals studied suggest that the reaction mechanisms for the individual minerals can be used to represent the oxidation behavior of the copper concentrate particles.

Jan 1, 2006

By John O. Burckle

For years, the measurement of fugitive emissions from the primary copper converter has defied all attempts based on inferential measurements, It has been concluded by virtually all investigators that the only dependable tech¬nique to measure these emissions would be to completely enclose an operating converter to permit the capture and measurement of all emissions. However, complete enclosure with a metal hood is difficult; many of the most serious fugitive emissions result during periods when the converter must be attended with crane-operated equipment. This approach would require either opening of the enclosure to permit the entry of large items of equipment or completely new methods for charging and tapping converters' The installation of the air curtain hooding system at ASARCO's Tacoma smelter has permitted a quantitative approach to the direct measurement of the fugitive for the first time. In this program, the fugitives captured by the air curtain were measured at a downstream sampling point in the exhaust side of the air curtain system during the various portions of the converter cycle. Emission factors were established for sulfur dioxide, filterable particulate (method 5), inhalable particulate, and selected trace elements.

Jan 1, 1983

By Zuomei Jin

The Mineralogical form of Silver in a Ag-rich complex ore was determined. In the complex sulfide ore, acidic thiourea leaching resulted in 35% extraction of silver directly. In the same complex sulfide ore, under the effect of ultrasonic treatment, 65% of silver can be ex¬tracted. After the above ore had been roasted and acidically leached of Zn and Cu, the silver extracted from this Pb-Ag residue was 96.8%. The effets of temperature, thiourea and ferric ion concentrations and partical size were examined. The leaching rate of silver from the Pb-Ag residue was diffusion controlled. The activation energy was calculated to be 10. 49%KJ/mole. The kinetic model for the thiourea leaching of silver from Pb-Ag residue was obtained and is given by, The kinetics of silver cementation by aluminium in thiourea solutions was also investigated. The activation energy was calculated to be 65. 13KJ/mole, which is reasonable fora rate-limiting surface reaction.

Jan 1, 1995

By William A. Apel

Several different strains of bacteria have been shown capable of reducing hexavalent chromium, Cr(VI), to Cr(III), a less toxic, .. more readily recoverable form of Cr. This paper examined the Cr(VI) reduction efficacies of 3 different Cr(VI) reducing bacteria: Pseudomonas f1uorescens LB300., Pseudomonas aeruginosa PAOI, and Pseudomonas aeruginosa PAOI (pCROI) It was demonstrated that all three bacterial stratns reduced Cr(VI) primarily during their exponential growth phases while using glucose as their carbon and energy source. Significant differences in the three organisms' Cr(Vl) reduction capabilities depending on initial Cr(VI) concentrations were also demonstrated. P. aeruginosa PAOI showed superior Cr(VI) reducing capabilities over the. entire range of Cr(VI) concentrations tested while the Cr(VI) reduction capabilities of the other two strains were increasingly inhibited as Cr(VI) concentrations increased.

Jan 1, 1991

By T. Shimizu

In Japan, the emission standard of selenium in effluent was set at a maximum of20 mgll in Feb. '94 for the first time, and it is scheduled to be further decreased to a maximum of 0.1 mg/I from Feb. '97 due to tightening of the Water Pollution Prevention Act. Selenium (IV) and (VI) are generally found in effluent from precious metals refineries. Although selenium (IV) can be easily eliminated by some reducing agents, selenium (VI) is more difficult to be reduced. Therefore, many smelters are having difficulty in complying with the new emission standard. At Mitsubishi Materials' Naoshima smelter, the behavior and the elimination of selenium in effluent have been extensively investigated. As a result, it was found that two strategies were particularly effective. One of them is improving the overall operation of precious metals refinery, that is, feeding uniformly the effluent to the waste-water treatment plant, reducing the effluent volume by recycling and recovering more selenium (IV) in the effluent. The other is eliminating selenium (VI) in the effluent from the precious metals refinery. It was found that selenium (VI) can be effectively reduced by using hydrazine under high? sulphuric acid concentration and high temperature conditions. By using these measures, it is considered that Naoshima Smelter will be able to comply with the new emission standard.

Jan 1, 1996

By D. J. Cassidy

This document discusses commercial strategies and applications of specialty processing plants for the recycling of nickel, copper, zinc and cobalt bearing by-products. For this discussion, I will focus on materials originating from the metal plating, electronic circuit board· and chemical industries. The review of select processes and the required service, sourcing, material handling, processing and marketing strategies necessary for a successful recycling program are highlighted. Materials discussed in this summary include filtercakes, filters, dusts, spent catalysts, spent solutions and solids. Both pyrometallurgical and hyrometallurgical applications to these materials are addressed. A comparison of targeted finished markets, including smelter feeds and value added products are also reviewed.

Jan 1, 2000

By K. B. McTaggart, G. Owusu, P. J. Merrin

"This study was conducted at Hudson Bay Mining and Smelting's zinc electrowinning tankhouse to determine the effects of varying levels of antimony and continuous gelatin addition on current efficiency. The levels of antimony and gelatin were varied from 0.012 to 0.030 mg/l and 0 to 10 mg/ll2 • 31 respectively, based on neutral ZnS04 electrolyte. A non-linear mathematical model relating current efficiency with antimony and gelatin was produced. The optimum operating point for gelatin was 6.5 mg/l. On the other hand the current efficiency increased with decreasing antimony levels. An interaction term between gelatin and antimony is present but is not significant enough to improve the ability of the tankhouse to handle purification upsets in antimony. Individually, the current efficiency was linear (decreasing) with antimony, and parabolic with gelatin concentration. However, at low antimony concentrations stripping of the cathode sheet was difficult. IntroductionThe zinc electrowinning tankhouse at Hudson Bay Mining and Smelting was designed in the 1930's and consists of 120 rows with each row containing ten cells. This system cascades acid from cell to cell In a row, with neutral zinc sulphate solution added to each cell through manually controlled spigots. Animal glue additions are made manually three times per day by operations personnel. The problem with this type of cell design and operation is that feed solution flows and composition can vary from cell to cell and from row to row due to the large number of manual control points. A new system which reduces the number of manual control points was designed and tested to determine if improvement in control of cell conditions would affect current efficiency. This system mixes spent acid, neutral ZnS04 electrolyte and reagents (gelatin, antimony and strontium carbonate) in a separate mix tank, ensuring that all cells receive a uniform feed solution. Gelatin was used in the test system instead of animal glue (which is presently used) because of the poor solubility and supply of industrial animal glue. The study reported here is the first in a series of experiments designed to justify the need to modify the present cascading cell feed system (Figure 1) to the proposed feed system (figure 2)."

Jan 1, 1997

By C. Dupuis

Thiourea is a promising reagent for gold extraction especially from refractory ores that cannot be treated by traditional cyanidation route. In this study recovery of gold from thiourea leaching solutions was investigated by direct electrowinning. The electrolysis cell consisted of a carbon flow-through cathode and a lead anode. The anodic and cathodic compartments were separated by a membrane. Galvanostatic mode was chosen for operation of the cell. Factors affecting recovery efficiency such as cathode thickness, linear flowrate, current intensity, thiourea and gold concentrations were investigated. The influence of some species in solution on efficiency and selectivity of recovery was investigated. Gold recovery reached 99% but current efficiency was lower than 10%. The complex formed with ferric ion and formamidine disulfide are reduced before gold-thiourea complex. Thiourea consumption occurred during leaching mainly by oxidation and reaction with dissolved copper.

Jan 1, 1989

By Charles I. Richman

Aquispirillum magnetotacticum (AM) is gram-negative hetrotrophic bacteria that belongs to a class ,of magnetotactic bacteria that have an ecological niche in marine marches and fresh water swamp sediments. Thiobacillus Ferrooxidans (TF) is a Gram-negative, acidophillic chemoliths that may have similar chemical conditions within the cytoplasmic membrane as Aquaspirillum M. to support growth of Magnetosomes. Magnetosomes are cellular bodies that accumulate under slightly aerobic conditions. Magnetotactic motion occurs in an external magnetic field and depends on the medium viscosity. The Atomic Force Microscope equipped with a magnetic tip shows the presence of Magnetosomes in these bacteria strains. The size, shape of magnetosomes in AM and TF strains are characterized.

Jan 1, 1998