Search Documents

By O. G. Olvera, D. G. Dixon, E. Asselin, L. S. Quiroz

Dissolution rates of chalcopyrite (CuFeS2) were calculated using electrochemical impedance spectroscopy (EIS). The calculated dissolution rate decreased by a factor of 3.2 after the electrode was passivated. The results presented in this work indicate that the reduction of Fe3+ was the rate-controlling step for fresh CuFeS2 electrodes while the transport of cations within the passive film limited the dissolution rate for the passivated electrode. The transfer of cations at the electrode/electrolyte and passive film/electrolyte interfaces did not affect the dissolution rates of the fresh and passivated CuFeS2 electrodes, respectively. The catalytic effect of pyrite (FeS2) on the dissolution of CuFeS2 continued after the passivating treatment. The contact of fresh and passivated CuFeS2 electrodes with different FeS2 particles resulted in increased dissolution rates, due to an increase in the reduction rate of Fe3+.

Jan 1, 2014

By Marcel Allard

On January 1st, 1977, SIDBEC-NORMINES INC. purchased from Quebec Cartier Mining Company various facilities located at Gagnon and Lac Jeannine together with the Fire Lake deposit. A t the same time, SIDBEC-NORMINES started its mining operations at Fire Lake, 83 km northeast of Gagnon. The paper summarizes the various adjustments which were necessary to satisfy the new production conditions, such as the physical and mechanical properties of the ore at Fire Lake, and the new crushing and loading installations at the mine, together with the transport of some 14 million tons of crude ore to the Lac Jeannine concentrator about 100km away, and finally to achieve satisfactory recovery from the FireLake ore. In addition, mention is made of the manpower organization, in which Quebec Cartier Mining Company plays an important role as manager of operations and owner of the railroad linking the mining operations to the pelletizing operations at Port-Cartier.

Jan 1, 1979

By J. Jin, J. D. Miller

"Bubble attachment at hydrophobic surfaces is of critical importance in the flotation recovery of mineral resources and fundamental experimental results have been reported in the literature describing the details of film thinning, rupture, and displacement. Now, for the first time, bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS). The simulation involves a nitrogen bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at the hydrophobic molybdenite (001) surface. During the simulation period of 1 ns, film rupture occurs and the nitrogen bubble attaches to the molybdenite (001) surface, resulting in a contact angle of about 90o. In contrast, the film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles, determined from MD simulation after stabilization of the three phase line of contact, are reported and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. For example, the interfacial water molecules for the hydrophobic molybdenite (001) surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed bythe presence of a 3 A water exclusion zone at the molybdenite/water interface. INTRODUCTIONAttachment of air bubbles to mineral particles is of fundamental importance in understanding flotation separation phenomena. It is well known that attachment of an air bubble at a hydrophobic surface includes film thinning, film rupture, and film displacement (Somasundaran, 2006; Wilson, Adlard, Cooke, & Poole, 2000). Experimental techniques, such as high speed video, can catch the process of bubble attachment at a mineral surface (Drelich & Miller, 2012; Niecikowska, Krasowska, Ralston, & Malysa, 2012). However, molecular scale information to examine the phenomena has not yet been reported."

Jan 1, 2016

By John R. Sullivan, Real Daigneault, Mathieu Piché, Jayanta Guha, Gilles Bouchard

"RESUMELa stratigraphie du camp minier de Matagami se résume a la présence de deux groupes volcaniques: le Groupe du Lac Watson et le Groupe de Wabassee qui le surmonte. Les gisements de sulfures massifs volcanogènes sont situés au sommet du Groupe du Lac Watson. Ces roches sont déformées par l'anticlinal de Galinée dont l'axe, orienté E-W, plonge vers l'ouest. Le cœur de cette structure est occupé par le Complexe de la Rivière Bell.Les roches volcaniques du flanc sud de l'anticlinal sont peu déformées et pendent à 45° vers le sud. Les gites qui s'y trouvent présentent la morphologie typique des gisements de sulfures massifs volcanogènes. Ceux-ci se situent le long d'un horizon repère cherteux et sulfure, appelé ""Tuffite Clef', et leurs cheminées d'altération rejoignent, en profondeur, une zone d'altération stratiforme d'étendue régionale.Les roches du flanc nord ont été transposées tectoniquement en écailles chevauchantes, de dimension kilométrique, a l'intérieur d'un couloir de failles anastomosées d'orientation est-ouest. A l'intérieur: le ce couloir, les gites de sulfures sont déformes et sépares de leur héminée d'altération sous-jacente par des failles.Les gites de sulfures situes sur les deux flancs de l'anticlinal de 'Galinée se seraient mis en place dans un mime environnement volcanique. Leur position stratigraphique est identique puisqu' ils se 'rouvent au sommet de la rhyolite porphyrique du Groupe du Lac Watson. lis se seraient constitués au cours d'une pose volcanique recédant 1'éruption du basalte du Groupe de Wabassee. Le Complexe de la Rivière Bell est perçu comme la source de chaleur responsable de la circulation des fluides hydrothermaux qui sont à ""origine des gisements de sulfures massifs volcanogènes."

Jan 1, 1990

By Hiroyuki Sano, Hiroshi Chida, Katsuya Toda, Takafumi Sasaki

Saganoseki Smelter & Refinery is one of the largest copper producers in Japan to produce 450,000 tons of new copper annually. Saganoseki used to operate six PS converters with "4 Hot-2 Blow" scheme, but managed to change its operation to "3 Hot-2 Blow" scheme with four PS converters, while maintaining the same production capacity. To achieve the operational change, the following improvements have been carried out; 1) Extending service life from 220 to 350 batches, 2) Shortening cycle time by increasing the blowing rate and the matte grade, 3) Reducing environmental impact by applying sophisticated fugitive gas collection system and 4) Saving energy by waste heat boiler’s modifications. The operational change has been successfully executed, and results in drastic productivity increase and cost reduction. Currently, Saganoseki is maintaining the efficient and consistent operation with 4 PS converters. This paper describes the above-mentioned improvements for increasing productivity and the recent operational conditions of the PS converters.

Jan 1, 2015

By E. Michelotti, M. Cardu

This paper presents the results of a new method that has been tested to recover metallic cobalt lost by diamond beads from rock cuttings. When dimension stones are cut using diamond wire saws, the beads become worn and, before the end of their cycle life, lose a certain amount of material; this material is prevalently made up of sintered metal and diamonds. The material is then washed away, together with rock debris, in a dilute pulp. In effect, this process involves the dispersion of economically valuable, but potentially polluting, materials (such as cobalt) that are used to confer indispensable technological features to the beads. This current research aims to develop a waste-processing pilot plant (High-gradient Magnetic Separator or HGMS) to recover metallic components from the pulp by means of a suitable separation. The research\u2019s purposes are two-fold: a. to remove the polluting components from the rock debris before their disposal and b. to start a recycling process of the valuable metals.

Jan 1, 2010

By Hilden. M.

"As the Cadia mill was the first 40ft diameter SAG mill, commissioned in 1998, its performance, liner and discharge design attracted considerable international attention. Twelve years on, the liner design and the control philosophy are being readdressed to further improve the mill’s performance. A comprehensive series of 3D liner scans, over life of the liner, have been used to calibrate liner mass loss and progressive changes in the liner profile. This data is being used to provide true charge mass and mill filling, plus progressive trajectory profiles over life of liner. This information, along with measures of mill performance over liner life, is being used to select the optimal operating conditions as the liner wears, and hopes to inform future liner design. INTRODUCTIONSince the Cadia mill was the first 40ft diameter SAG mill, its performance, liner and discharge design has attracted considerable international attention, as reported in previous SAG conferences. The mill experienced particular challenges with regard to pebble and slurry discharge, which necessitated a discharge redesign, incorporating a considerably greater pebble port open area and curved pulp lifters (Hart, Valery, Clements, Reed, Song & Dunne, 2001). Packing between lifter bars on the shell liner was found to dramatically reduce mill throughput over the first half of the liner life. In response, the liners were redesigned to a 2/3 spacing so as to open up the space between lifters. Due to ongoing high liner wear issues, the liner was redesigned based on the discrete element modelling (DEM) of Conveyor Dynamics conducted by Nordell and Potapov (2001). This aimed to maintain mill throughput with new liners and provide an extended liner life. This design was kept proprietary for many years, so has not been open to review."

Jan 1, 2012

By H. McIntire, R. Preston, D. Roberts

"Repeated 3D terrestrial digital photogrammetric surveys were conducted on hard rock mine pillars to characterize damage during secondary mining. Damage was quantified by measuring Depth of Failure, DOF, from spalling material and crack intensity, D21. These damage values were then correlated to visually assessed Pillar Damage Ratings and numerically estimated pillar loads. Measured damage, particularly Depth of Failure, correlated well with Pillar Damage Ratings. Numerical predicted pillar stress vs. damage exhibited the expected trend with shorter pillars being stronger. High resolution photographs and 3D models were also used to characterize damage mechanisms, which were found to be structurally constrained. INTRODUCTIONThe Doe Run companies Southeast Missouri Operations consists of six room and pillar lead mines (Brushy Creek, No. 29, Casteel, Buick, Fletcher and, Sweetwater) (The Doe Run Company, 2014). The mines are hosted in the Carbonates and Shales of the Viburnum trend with mining depths varying from 180 to 300 m. Pillars are commonly cut square with widths varying from 7 to 9 m and heights generally between 5 and 18 m, resulting in extraction ratios between 80 and 85% (Roberts et al., 1999). Figure 1 presents an idealized stratigraphic section through the Viburnum trend and Figure 2 shows a plan view of the five areas spanning the three mines included in this study."

Jan 1, 2015

By D. Furrer, M. Dallaire

The arrival of Image analysis in the last 20 years has changed the world of quantitative metallography. Many standard measurement techniques which were previously manual can now be done with fully automated systems. This reduces subjectivity and operator fatigue and therefore enhances the quality of the statistical results. In many laboratories, Titanium Alloy microstructures continue to be evaluated by traditional methods, where quality of results is subject to operator fatigue and level of experience. Advances in Camera technology have tremendously improved image acquisition. One can often see clearly at 500x what can not be observed at 1000x, allowing for a larger area to be analyzed, without the inconveniences associated with very high magnification objectives. Powerful and versatile Image analysis software combined with a high precision motorized stage gives access to a multitude of applications, which were extremely challenging or impossible until now. Image Analysis tools such as Multilayer Grab, which reconstructs an uneven image into one plane of focus (ex. Observation at high magnification of texture resulting from etching) and Mosaic which builds an image from a number of fields of view (ex. Reconstruction of very large grains at low magnifications) expand even further the power and flexibility of IA systems. This presentation will describe how automated methods are applied to the point count method and grain size measurement. We will show how cameras and software work together to permit quantitative measurements of primary alpha and prior beta microstructures, as well as lamellar alpha plate thickness in titanium alloys.Automated and semi automated quantitative measurements of various Titanium microstrures have been assessed, using the Clemex Vision PE. Examples of the methods and steps used are presented.

Jan 1, 2006

By A. H. Harvey, M. Delangen, A. D. Fernie

"A large-scale expansion to Pacific Coast Bulk Terminals Ltd. has now been completed and placed in operation. The original plant, built approximately eight years ago, consists of the direct rail-car to ship transfer of bulk commodities. The extension includes additional rail-car unloading, a transfer house system for directing commodities to storage or ship, major storage and reclaim facilities, a second shiploader and a second deep-sea berth. In addition to the facilities for overseas shipments, a wood-chip loader and a barge berth have been installed for domestic shipments of wood chips and, occasionally, for other local commodities. The design considerations imposed by the nature of the products to be handled are covered in this paper."

Jan 1, 1969

By R. Holmestad, M. Gazizov, S. Wenner, R. Kaibyshev, J. K. Sunde

"Mechanical properties and microstructure of an Al-4.7Cu-0.74Mg-0.51Si-0.48Mn-0.10Cr-0.09Ti-0.02Fe (wt. %) alloy subjected to various thermomechanical processing (TMP) have been investigated and compared to conventional ageing at 170°C (designated T6). Three TMP routes involving cold deformation of solution treated samples were tested. These were (i) 3%-stretching (T8-3%), (ii) equal-channel angular pressing (ECAP) to true strain (e) of ~1 (T8-1) and (iii) ECAP to e~2 (T8-2), all with subsequent ageing at 170°C for 0-96 h. At peak age conditions, both yield stress, ultimate tensile strength and elongation-to-fracture decreased for the T8-3% state as compared to the T6 condition. Intermediate ECAP (T8-1 and T8-2) lead to significant increase in maximum yield stress, ultimate tensile strength and elongation-to-fracture. The changes in mechanical properties were related to microstructure evolution, encompassing changes in grain sizes, dislocation densities, precipitate morphology and phase fractions, which were characterised using transmission electron microscopy. Relations between TMP, precipitation behavior and contributions to different strengthening mechanisms are evaluated.INTRODUCTION Al-Cu-Mg-Si alloys are widely used as structural materials in aerospace industry due to their attractive combination of high specific strength, good fracture toughness and enhanced creep resistance. These properties are largely due to the formation of a large number of nano-sized metastable precipitates during artificial ageing (Polmear, 2006; Eskin, 2003; Gazizov, Dubina, Zhemchuzhnikova, & Kaibyshev, 2015). The precipitation behaviour in these alloys is complicated and depends among other things on Cu concentration and the Mg:Si ratio (Wolverton, 2001; Chakrabarti, & Laughlin, 2004). In general, the precipitation sequence has been presented in a prior study (Eskin, 2003) as follows:"

Jan 1, 2018

By V. W. Shtenko, B. J. Ennis, P. H. Bridge

"The northeastern region of British Columbia contains large quantities of high-quality metallurgical coal. To market the coal, it was necessary to provide the required infrastructure which included rail access. This paper presents the role of the British Columbia Railway in the northeast coal development.In 1976, B.C. Railway undertook to study two main routes, one originating at Chetwynd and the other at Anzac, both located on the main line, north of Prince George. The routes studied are briefly described, detailing the methodology and engineering analysis carried out to permit the selection of a single route that would be the most cost effective, taking into consideration the construction, maintenance and operating costs. The operating parameters, track and grade standards, anticipated tonnage, construction costs and the final route selected are also presented.Pre-engineering analysis and studies of the route selected originating at Anzac, known as Tumbler Ridge Branch Line, and which commenced in 1977, were concluded in 1978. New mapping was developed to a scale of 1:2000 with good vertical and horizontal control. Based on the mapping data, terrain analysis, and designs developed, an estimate of construction costs and schedule of work was developed.Authority to proceed with the final design and construction was provided in December 1980, with the first shipment scheduled for December I, 1983. Final designs of all structures are discussed, including schedules, cost to completion, and control systems utilized. The decision to electrify the Tumbler Ridge Branch Line and related topics are discussed, with a brief description of train operations. The present status of the project is also presented."

Jan 1, 1983

By H. Son

The three-dimensional (3D) reconstruction of as-built industrial plant models plays an important role in revamping planning, maintenance planning, and preparation for dismantling during the lifecycle of industrial plants. Recently, the 3D reconstruction of existing industrial plants was conducted using laserscan data to make surveying processes more efficient. However, the current 3D reconstruction process from laser-scan data is still limited due to the need for significant human assistance. Although a great deal of effort has been made to efficiently reconstruct 3D as-built industrial plant models, the presence of objects?such as equipment, pipelines, and valves of different sizes and shapes?in existing industrial plants significantly increases the complexity of laser-scan data and makes automating the reconstruction process more challenging in practice. The purpose of this study is to propose a knowledge-based approach for the 3D reconstruction of as-built industrial plant models from unstructured laser-scan data. First, pipelines were extracted from laser-scan data based on surface curvature information and knowledge about pipelines' sizes from existing piping and instrumentation diagrams (P&ID). Once entire pipelines were extracted, they were modeled based on skeleton features. Then, the remaining objects were clustered and grouped separately via the region grouping process. Afterward, clustered objects were retrieved and modeled based on global feature-based matching from the 3D database. Finally, the resulting model was checked to ensure that it was well-reconstructed according to the information regarding the relationships among objects abstracted from the existing P&ID. The preliminary results on actual industrial plants show that integrating knowledge into the reconstruction steps played an important role in the proposed approach and that this approach obtained accurate as-built industrial plant models from unstructured laser-scan data. The proposed approach could be successfully utilized to assist in many applications during the lifecycle of industrial plants.

Aug 1, 2013

By S. D. F. Rocha1, L. Katsarou, G. P. Demopoulos

"Crystalline scorodite (FeAsO4·2H2O) has been pointed out as the most stable compound to immobilize arsenic for disposal due to its good stability performance according to EPA’s TCLP test. However, in anaerobic conditions, arsenic releasing is increased to undesired levels due to scorodite reductive break down, in eh <100 mV at 5.5< pH <7 which causes contamination of groundwater. In this work, the concept of encapsulation by controlled deposition of mineral coatings immune to pH or redox potential variations is presented. Aluminum and calcium phosphates were evaluated as coatings and the release of arsenic from scorodite previously coated with phosphates was substantially decreased when compared to the VALUES (obtained from crude scorodite, both in oxic and anoxic conditions. INTRODUCTIONThe widely acknowledged hazardous properties of arsenic as a soil and natural water contaminant and its adverse health effects when present in drinking water have led to very strict environmental regulations (Mandal & Suzuki, 2002) aiming at the drastic reduction of the presence of arsenic in the effluents of the mining and metallurgical industries.In Canada, the Metal Mining Effluent Regulations (Government of Canada, 2002) dictate that the maximum monthly mean concentration in tailings for arsenic must be lower than 0.5 mg/L. At the same time the new Environmental Protection Agency’s (EPA) standard for drinking water foresees concentrations of arsenic less than 0.01 mg/L, which means that the leachability limit for the industrial waste is set at 1 mg/L arsenic (EPA, 1994; Le Berre et. al, 2007). One of the preoccupations of the mining and metallurgical industries is directed to the elimination of arsenic presence in all its effluents, especially since arsenic is commonly found in many ores mainly in the form of oxides and sulphides. After processing of arsenic-containing ores and concentrates, arsenic can be present either in solid residues and tailings, liquid effluents or in flue dusts. Several of these forms of arsenic waste materials are soluble and therefore may cause the contamination of ground water, if disposed of without further treatment."

Jan 1, 2012

By W. F. James

Introduction The season of 1927, from the point of view of mining development in the area west of Rouyn, was quite satisfactory. Serious prospecting and development&apos; were undertaken over quite a large area, though the results in the matter of discovering new deposits of economic importance were rather disappointing. A large amount of systematic prospecting and geological mapping was carried out in the course of the work, and a considerable body of information collected. A widespread occurrence of sulphide mineralization was noted, chiefly near bodies of older gabbro. The frequent occurrence of pyrrhotite in or near which local concentrations of chalcopyrite were localized, lends support to the idea that such older sulphides as pyrite and pyrrhotite are relatively easy of replacement by chalcopyrite. From the prospector&apos;s viewpoint, areas near the contacts of masses of older gabbro are favourable prospecting ground, and pyrite and pyrrhotite mineralization are favourable indications that massive chalcopyrite may be found where it has completely replaced such sulphides. Pyrrhotite being magnetic is easily located, even where drift covered, by the use of such convenient instruments as the dip-needle and the magnetometer. It is suggested that pyrrhotite bodies, when located, be thoroughly prospected because of the fairly strong probability that they may show replacement by the more valuable chalcopyrite.

Jan 1, 1928

By William J. Davis, R. Blair Hrabi, Sally Pehrsson, Amelia V. Logan, Ross Sherlock

"Abstract - The Meadowbank gold deposits are hosted by a series of polydeformed and metamorphosed auriferous iron formations located in the Neoarchean Woodburn Lake group, western Churchill province, Nunavut. The supracrustal rocks in the Meadowbank area consist of a thick sequence of intermediate-composition volcanic rocks with intercalated iron formation, ultramafic volcanic rocks, and quartzite to quartz arenite. U-Pb geochronology gives an interpreted age of 2711 ± 3 Ma for the host strata at Meadowbank.The intermediate volcanic rocks are predominately volcaniclastic and have a geochemical composition that is consistent with an active continental margin setting. Iron formation deposition was coeval with the intermediate volcanism, as indicated by incorporation of volcanic detritus in the chemical precipitate. The geochemistry of the iron formation indicates that it precipitated from a fluid that at one time was at high temperature (>250°C), reducing, and likely acidic. Intercalated ultramafic rocks rarely show spinifex textures and have trace element ratios that are consistent with mantle plume-related undepleted mantle asthenosphere, likely recording episodic mantle upwelling associated with rifting in an active continental margin. The contact between the ultramafic volcanic rocks and the overlying quartz arenite is a disconformity marked by a quartz pebble conglomerate. However, similar geology on the structural hanging wall and footwall of the contact suggests that the conglomerate does not represent a significant hiatus in deposition, and is more likely a prograding terriginous siliciclastic unit.Three metamorphic events are recognized. The first, M1, is a cryptic greenschist facies event that is pre-D2. The second event, M2, is a mid-greenschist to amphibolite facies, syn-D2 event. M3 is the last event recognized, and is a post-tectonic greenschist facies event that is regional but inhomogeneous in extent, possibly reflecting thermal aureoles around post-tectonic 1.7 to 1.8 Ga Nueltin granites. The structural geology of the area is complex with four phases of deformation recognized, two of which had a significant effect on the geometry of the deposit. All of these regional events are interpreted as Paleoproterozoic in age. Relationships between deformation fabrics and mineralization, as well as the overall geometry of the mineralized envelopes, suggest that the deposit formed during syn- to late-D2. Superimposed on the mineralization are D4 structural elements that postdate gold mineralization.The main control on gold mineralization is replacement of magnetite by pyrrhotite and pyrite in high-strain corridors. The composition of amphiboles and chlorites associated with gold mineralization is remarkably consistent and shows no spatial or temporal variation, suggesting that it was buffered by the iron-rich nature of the host rocks. The bulk metasomatic effect on the intermediate volcanic rocks is characterized by the addition of K2O and the loss of CaO, Na2O, and MgO, with little variation in the total iron content. The elemental losses are likely the result of destruction of feldspars, stilpnomelane, and ferroactinolite, which are relatively common in the unmineralized rocks, and the formation of sericite, chlorite, and grunerite."

Jan 1, 2004

As land resources decrease, commodity prices increase, and technology evolves, deep sea mining is becoming a viable alternative to meet the increasing demand for minerals. Successful deep sea mining operations are built on sound identification of the resource, proper selection of equipment, a thoughtful production plan, and good project management. These four key activities can be further optimized by analyzing how the spatial variability and uncertainty of the ore body properties impact the final mining operation. To address this problem, IHC Merwede is in the process of developing a risk quantification framework in the context of deep sea mining, which makes use of state of the art geostatistical simulation methods and transfer functions to quantify geological uncertainty and translate it into decision or project risk. The paper introduces the Local Average Subdivision method (LAS) for generating simulated models of the deposit and presents a new extension to incorporate point measurements of geotechnical or ore grade properties. Due to its computational efficiency, the presented method is suitable for simulating largely extended sea floor deposits. The second part of the paper illustrates, through example case studies, the significant benefits of a risk based approach which translates geological uncertainty into financial or operational performance indicators. In particular, the focus is on assessing financial project risk and on the design optimization of the deep sea excavation equipment by analyzing cutting forces, specific energies, and power requirements.

Aug 1, 2013

By P. Moreno

ABSTRACT: The Maras salt terraces, located between Cuzco and Urubamba in the Andes (southern Peru), are living examples of traditional Incan salt production, where present-day artisanal miners produce salt from shallow pans by solar evaporation. In these terraces, natural spring water, eight to nine times saltier than seawater, is used to produce the salt. The field observations and chemical analyses show that the poorly crystalline traditional salt is finer in particle size and contains impurities such as dolomite and gypsum. These differences are the result of shallow pond depth, contamination from wall erosion, and the nonsequential mode of salt crystallization.

Jan 1, 2011

By J. R. Rodda

Stainless steels are widely used to handle concentrated sulphuric acid (H2SO4) solutions produced in the manufacturing process, The majority of corrosion rate data published for stainless steel in product acid conditions is typically complied in tables or in iso-corrosion diagrams (iso-corrosion rates plotted as a function of temperature and H2SO4 concentration), without any reported consideration as to the accuracy and relevance of the method used to obtain the data, Given the characteristic potential cycling associated with the active-passive corrosion behaviour exhibited by stainless steel in hot, concentrated H2SO4, weight loss is considered to be a more reliable method than electrochemical measurements to measure corrosion rates, Consequently, an effort is made herein to demonstrate the accuracy and relevance of weight loss to determine laboratory corrosion rates in product acid conditions.

Jan 1, 2010

By Joo Hyun Park, Hyun-Sik Park

"Gold is one of the most valuable and precious metals. But, the extraction efficiency of gold from natural resources is very low and labor-intensive due to very low concentration of gold, i.e.,1–5 ppm, which means that gold extraction processes produce extensive amounts of tailings. The gold content in printed circuit boards (PCB) from waste mobile phones is about 100 to 400 ppm, which is enormously greater than the concentration found in natural ores. Consequently, processes for recycling waste PCB and gold mine tailings become of increasing importance to maintain a sustainable society. As processing these waste materials by pyrometallurgical methods has become more economically attractive, understanding the thermodynamic behavior of gold in smelting slags under oxidizing and reducing conditions has become increasingly important. Therefore, in this study, the effects of slag chemistry, oxygen potential and temperature on gold solubility in smelting slags are discussed. From the results presented, the predominant species of gold is strongly dependent on the basicity of slag. Furthermore, more basic slags showed higher solubility of gold at a given oxygen partial pressure, and more oxidizing atmospheres enhanced the dissolution of gold to the molten slag phase. As a consequence, careful control of the slag composition during pyro-processing of gold-containing waste materials is required to maximize gold recovery. INTRODUCTIONGold has good physicochemical properties. Thus, it plays an increasingly important role in industrial applications. For example, over 300 tons of gold are used annually in electronic components (Hageluken &Corti, 2010).However, 75% of all gold ever produced has been extracted since 1910 and gold reserves in the world are becoming rapidly depleted (Louis & Pluchery, 2012).The cost of gold production and its price in the market have increased rapidly during last 20 years as shown in Figure 1, and interest in the recycling of gold-containing materials has naturally increased.The wastes from electronic equipment (e-wastes) contain large amounts of precious metals compared to their own respective ores, and therefore such wastes may be considered as a secondary source of valuable metals. For instance, the concentration of gold in natural ore is commonly 0.5–15 g/ton-ore (0.5–15 ppm), while its concentration in electronic circuit boards is over 10 times higher, typically being about 150 ppm in expansion cards and over 10,000 ppm in central processing units(Barbieri et al., 2010).Also, gold mine tailings are discharged after the flotation process as slurry form then stored near the operating plants (approx. 100 ton per day in one Korean gold mine). Gold mine tailings contain gold at about 1–2 g/ton. This is the reason why Au-containing materials such as e-wastes and mining wastes are highly important sources of gold (Yamasue et al., 2009)."

Jan 1, 2017