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By Engin Burak Anil

Objective, accurate, and fast assessment of damage to buildings after an earthquake is crucial for timely remediation of material losses and safety of occupants of buildings. Laser scanners are promising sensors for collecting geometrical data regarding the damaged states of buildings, as they are able to provide high coverage and accuracy at long ranges. Yet, we have limited knowledge on the performance of laser scanners for detecting earthquake damage, and requirements of such data collection. This paper focuses on characterizing the performance of laser scanners for detecting thin cracks for damage assessment of reinforced concrete frames. We identified a series of crack parameters based on the state-of-the-art damage assessment codes and standards. Similarly, we identified parameters, which affect the performance of laser scanners for detecting cracks, based on prior research in this area. We studied the width, depth, and orientation of cracks; sampling interval of the scanner, and the range of the laser beam from the surface. Effects of these parameters on the detection of the minimum crack size were determined in an experimental setting. An automated algorithm was used to analyze the data. The results show that it is possible to detect as small as ~1mm cracks.

Aug 1, 2013

By P. E. Georghiou, S. Shafiei Zadeh, H. Hassan Nejad

Data are presented on the extractant behaviour on toxic metal removal from spent hydroprocessing catalyst, produced at the North Atlantic Refinery plant in Newfoundland and Labrador. Aliquat 336 was selected due to its potential capabilities for the separation of cobalt, molybdenum and nickel from the leachate extractant produced by aqua regia. The solvent extraction process was statistically modeled using central composite design (CCD), and the numerical optimization was conducted to achieve the optimum point for toxic metal recovery for the extractant.

Jan 1, 2014

By Louise Corriveau

Exploration strategies have traditionally considered felsic gneiss complexes of the Canadian Shield sterile. This paradigm is challenged with the discovery of extensive granulite-facies Cu-Au, Fe oxides-bearing hydrothermal systems in the 1.4 Ga Bondy and 1.5 Ga La Romaine volcano-plutonic complexes of the Grenville Province. Early identification of magnetite-rich units in association with meta-exhalite and pelite-like units was key to targeting the search for mineralization, protolith information and indicators of pre-metamorphic hydrothermal activity during regional surveys of these frontier terrains. Textural evidences for a volcano-plutonic setting were found. There remained, however, numerous impediments to the recognition that the ubiquitous magnetite-laden units and associated aluminous gneiss were hydrothermal in origin. Many metamorphic reactions form magnetite at the amphibolite to granulite facies transition, and hydrothermally-leached rocks resemble metapelite or migmatitic restite, while carbonate alteration zones may look like marble or calc-silicate rock. Non-typical metamorphic mineral assemblages, modes and colours arise when hydrothermally-derived rock types are metamorphosed. These effective markers served as tools for reliable field identification of hydrothermally-altered rocks. In our case-studies, we traced pre-metamorphic hydrothermally-driven Fe-oxide precipitation in association with sericitization, albitization, pyrophyllite alteration, chloritization, and B enrichment by mapping unusually high contents of (1) magnetite or hematite, (2) biotite, (3) albite, (4) sillimanite, (5) orthopyroxene or phlogopite with cordierite, and (6) tourmaline or kornerupine. The unveiled garnetite, tourmalinite, and aluminous gneiss had assemblages that vary according to metamorphic grade and composition. To assess if high mode of Fe-Mg-Al phases resulted from partial melting (restitic residue) or metamorphism of hydrothermal rocks, we compared leucosome mineral assemblages, shape and amount with that expected of in situ partial melting reactions. In both areas there is no compelling evidence for these units to be restites. In contrast, the presence of lapilli in garnet-cordierite-sillimanite gneiss, though extremely rare, constitutes conclusive evidence for extreme pre-metamorphic high-sulphidation alteration of a volcanic protolith, while Fe-oxides or sillimanite-bearing nodules and veins record a less pervasive alteration. Geochemical research on element mobility and mass balance calculations further testified of an hydrothermal origin for these gneisses. The magnetite-rich units, together with calc-silicate rocks, garnetite, hornblendite, albitite among amphibolite, provided effective guides to sites of fluid discharge and led to the discovery of Cu and Cu-Au showings. With the presence of highsulphidation alteration, these features suggest early Cu-Au VHMS-type alteration halos within a predominantly felsic composite volcano-plutonic arc setting for both case-studies. Evidences for subsequent F-driven orthomagmatic fluid activity are also present.

May 1, 2003

By Mark B. Thorpe

Golden Star Resources started gold mining operations in Africa in 1999 after 15 years of exploration in South America. At the time, the approach to local assistance was through "alternative livelihood" programs and the donation of infrastructure to local communities. This was initially successful with local community support. However, with time and on reviewing the implemented projects, it became evident that the success was limited and many if the projects were either poorly used or in disrepair. Through a review of the options, we decided to develop a community assistance model driven by the communities themselves, while keeping control of the finances and the actual construction of the projects. Through the formation of the Golden Star Development Foundation, we began to support community driven projects for local economic development. The evolution of economic development projects continued over the next several years with the addition of project requirements for partnerships with government, and finally an evolution to a partnered turn-key piece of infrastructure that we hand over to an agency for operation and ongoing maintenance. We are currently working with outside partners to further our economic development activities in Ghana to the benefit of our stakeholders.

May 1, 2011

By C. W. Chao, M. Melashvili, F. Hilário

The processing of a bulk concentrate containing copper as chalcocite, enargite, bornite and chalcopyrite along with pyrite and precious metals of silver and gold was studied. A leaching study was undertaken to examine the application of the atmospheric acid leaching process to a bulk copper concentrate for copper recovery followed by cyanidation or thiosulfate leaching for gold and silver recovery. The extraction of copper exceeded 90% under some conditions and the recovery of gold and silver reached a maximum of 44 and 45%, respectively. A sample of bulk concentrate was roasted in air to oxidize the sulfides with release of sulfur dioxide followed by acid leaching of the roaster calcine and cyanidation of the acid leach solution. The copper extraction reached over 92% and the gold extraction exceeded 88%. The sulfur dioxide may be captured for acid production. INTRODUCTION The processing of a large primary copper deposit in Indonesia is under investigation. One of the possible routes for processing involves flotation of a bulk copper-gold concentrate followed by treatment by an atmospheric leach/SX-EW process for copper recovery. The atmospheric leach residue would then be leached for recovery of gold and silver. A second route involves roasting of the concentrate followed by acid leaching and SX-EW for copper recovery. The leach residue from the roaster calcine would then be leached for recovery of gold and silver. The roaster off-gases could be used for sulfuric acid manufacture, enabling the production of a valuable by-product. The Cobre Las Cruces (CLC) process (Munoz, Garcia, & Delgado, 2017) was designed to treat a resource of copper discovered close to Seville, Spain. The process was developed by Outotec with MK Gold (original project owner). INMET Mining subsequently purchased the deposit from MK Gold and built the copper processing facility. The CLC process is similar to the Mt. Gordon Copper process; except that OKTOP reactors have been installed instead of a low temperature, low pressure autoclave process. The plant was designed to treat 1.3 mtpa of ore at a grade of 6.2% Cu to produce 72,000 tpa of cathode copper over a 15 year project life. The main gangue mineral at Cobre Las Cruces was pyrite. The Cobre Las Cruces ore is therefore similar to a rougher flotation concentrate containing copper minerals and pyrite. The roasting of a rougher flotation concentrate can be designed to produce hematite, basic copper oxides and sulfur dioxide off gas. The acid leaching of the basic copper oxides may produce soluble copper for SX-EW recovery of copper. The sulfur dioxide off-gas may be used to make sulfuric acid.

Jan 1, 2019

By R. A. D. Pattrick, D. A. Polya, D. J. Marsh, J. -J. Bao

"Abstract-The utility of high-density stream sediment and stream water sampling to the exploration for silver deposits was investigated by the study of the epithermal Ag-Au base-metal prospect at Lagalochan in western Scotland. The geology of Lagalochan is dominated by a calc-alkaline Caledonian intrusive complex emplaced into Dalradian Supergroup rocks (Harris et al., 1988a). The complex consists of subvolcanic porphyrytic rocks associated with intense hydrothermal alteration and brecciation. Early Cu-Ag-Mo-rich mineralization is found in the core of the complex with later Pb-Zn-Ag-Au-As-Sb-rich mineralization toward the margins (op. cit.).Stream sediment sample analysis spatially resolved the Cu-rich and Ag-rich mineralization. Ag and Cu anomalies relative to local background values were found in all size fractions analyzed (-125 µm, +125 µm, +180 µm, +250 µm) but the more pronounced anomalies were found in the -125 µm fraction. The coarser fractions generally revealed more erratic but longer dispersion trails. The separation of Cu-rich and Ag-rich mineralization is also apparent in the distribution of relatively high dissolved Cu and Ag in stream waters, particular when expressed relative to the solute load as Cu/TDS and Ag/TDS.The mineralization at Lagalochan is indicated by Ag, Cu and Pb stream sediment and water concentrations that are anomalous with respect to local backgrounds, but are difficult to distinguish from regional backgrounds. This emphasizes the further potential of high-density stream water sampling, in particular, as a viable geochemical exploration tool on a sub-regional scale for epithermal deposits in relatively unpolluted upland terranes."

Jan 1, 1995

By R. A. D. Pattrick, D. A. Polya, D. J. Marsh, J. -J. Bao

"The utility of high-density stream sediment and stream water sampling to the exploration for silver deposits was investigated by the study of the epithermal Ag-Au base-metal prospect at Lagalochan in western Scotland. The geology of Lagalochan is dominated by a calc-alkaline Caledonian intrusive complex emplaced into Dalradian Supergroup rocks (Harris et al., 1988a). The complex consists of subvolcanic porphyrytic rocks associated with intense hydrothermal alteration and brecciation. Early Cu-Ag-Mo-rich mineralization is found in the core of the complex with later Pb-Zn-Ag-Au-As-Sb-rich mineralization toward the margins (op. cit.).Stream sediment sample analysis spatially resolved the Cu-rich and Ag-rich mineralization. Ag and Cu anomalies relative to local background values were found in all size fractions analyzed (-125µm, +125 µm, +180 µm, +250 µm) but the more pronounced anomalies were found in the -125 µm fraction. The coarser fractions generally revealed more erratic but longer dispersion trails. The separation of Cu-rich and Ag-rich mineralization is also apparent in the distribution of relatively high dissolved Cu and Ag in stream waters, particular when expressed relative to the solute load as Cu/TDS and Ag/TDS.The mineralization at Lagalochan is indicated by Ag, Cu and Pb stream sediment and water concentrations that are anomalous with respect to local backgrounds, but are difficult to distinguish from regional backgrounds. This emphasizes the further potential of high-density stream water sampling,in particular, as a viable geochemical exploration tool on a sub-regional scale for epithermal depositsin relatively unpolluted upland terranes."

Jan 1, 1995

By H. Dundar

An extensive testwork was performed around the HPGR plant at GoldFields Ghana Limited Tarkwa Gold Mine. The HPGR was used to prepare the feed for heap leaching. The circuit was configured in such a way that the edge material from the HPGR discharge was recycled for further crushing while the product from the centre reported to the heap leach section. The set-up of the Polysius HPGR provided an opportunity to study the effect of different design and operating variables. This paper will discuss the results from the tests performed to assess the effect of rolls? speed and applied pressure on the capacity and the grinding efficiency of the HPGR. Applying different pressure values appeared to have an influence on the amount of edge material recycled.

Jan 1, 2012

By Zia Pirzada

"Time is of the essence" and "Time is money" These are powerful and true statements during a project life cycle and have far-reaching implications on the success and failure of the project Time and progress management is crucial to the project success. Project delays may increase the cost to an unacceptable level and may render the project as economically unfeasible. On the other hand, if the project is completed on time or earlier than as planned, it may generate economic benefits greater than what had been envisioned To take advantage of the financial opportunities and to improve the cash flow as well as Return On Investment (POI), project schedule can be accelerated to complete the project earlier than planned Project schedule acceleration can be achieved by using analytical tools, such as "Schedule Optimization", "Schedule Reduction", "Schedule Compression" or a combination of any of these concepts along with the "Planning for start up". Schedule optimization does not entail any extra cost, however, other acceleration methods, such as Schedule Reduction and Schedule Compression, may require extra expenditures from the owner. Based on the forecasted early start of the revenue stream, the extra expenditure could become a worthwhile venture with a very high rate of return To accelerate the schedule, all aspects of the project should be reviewed with acceleration costs calculated. All risks and opportunities should be evaluated and taken into consideration to determine if the acceleration is feasible and advisable and will provide definite financial advantages Sometimes schedule acceleration may be desired to prevent the company from paying liquidated damages. This is especially true when the project is not expected to complete on the contractual completion date and when the cost of acceleration is less than the liquidated damages that may accrue against the company.

Oct 1, 2010

By M. B. Kime

"Discrete-element method (DEM) modelling is a powerful tool for studying particulate systems within the mineral processing industry. DEM simulations were conducted to investigate the power draw, load behaviour, and impact energy profile of an experimental ball mill under different milling conditions. The variables considered were mill rotational speed (percent critical speed), ball size, and lifter face angle. The simulation results indicated that the grinding efficiency would be enhanced by using 80% critical speed, 30 mm ball diameter, and 45° lifter face angle. These findings can be useful in guiding actual ball milling tests involving an ore sample.RÉSUMÉ La modélisation par méthode des éléments distincts (MED) est un outil puissant qui permet d’étudier les systèmes particulaires au sein de l’industrie de traitement des minerais. Des simulations par MED ont été menées de façon à étudier le profil de la consommation énergétique, du comportement de la charge et de l’énergie de rupture d’un broyeur à boulets expérimental dans diverses conditions de broyage. Parmi les variables prises en compte figuraient la vitesse de rotation du broyeur (vitesse critique en pourcentage), la taille des boulets et l’angle de coupe de la cornière élévatrice. D’après les résultats de la simulation, on pourrait améliorer l’efficacité de broyage en utilisant une vitesse critique de 80 %, un diamètre de boulet de 30 mm et un angle de coupe de 45 ° de la cornière élévatrice. Ces résultats peuvent se révéler utiles pour les essais concrets de broyage à boulets impliquant un échantillon de minerai."

Jan 1, 2017

By J. F. Shirley

"Very seldom, if ever, is a molybdenite by-product plant operated exactly the way the process design engineer visualizes it. The best thing the design engineer can do is provide a sound, basic circuit with enough room and flexibility in order that the operating staff can make the necessary modi fi cations to optimize the process. The plant, with minor modifications, should be capable of handling more than one process. This is especially true when the client is having the plant designed for a new process.The writer would like to propose the following ten ""rules-of thumb"" for designing by-product molybdenite plants where the molybdenite is floated out of a copper concentrate. The term rules-of-thumb is used, because there are probably valid reasons for not using one or more of them in a particular plant design. In fact it was 1980 before the writer was all owed to start up a plant where all of these rules were honored in the plant design. This was after 19 years of experience in the design of molybdenite by-product processes and plants. The main reasons for not following the rules are available capital, available space, and the client's experiences based on pilot plant and laboratory test results."

Jan 1, 1981

By EJ. Reichhardf

The Molopo Farms Complex is a major, layered ultramafic/mafic, early Proterowic intrusion which is totally covered by sediments of the Karoo and Kalahari Fonnations and situated in southern Botswana and northeastern South Africa. The approximately 3000 m thick, generally fine- to medium-grained ultramafic and mafic cumulates are intrusive into equivalents of Thmsvaal Supergroup sediments and lavas. Multiphase defonnation resulted in tilting and segmentation of the Complex into individual tectonic blocks. Sr isotopes document at least two chemically distinct parental liquids which interacted in a complex manner to form an approximately 1000 m thick rhythmically layered succession which straddles the ultramafic/mafic boundary. Repeated mixing resulted in a complex cryptic layering pattern and numerous sulfide-enriched layers which contain significant PGE+Au concentrations.

Jan 1, 1994

By K. Wongpreedee

Recovery and recrystallization of Au wire can degrade strength and alter conductivity properties during exposure to elevated temperature. Au Deformation Processed Metal Metal Composites (Au DMMC's) are being developed for electronic applications requiring high conductivity and high strength. This paper discusses the relationships between microstructure, strength, and resistivity of Au DMMC's. It also presents the results of a recent study on the elevated temperature stability of Au DMMC's of several compositions. Au-7 vol %Ag, Au-14 vol %Ag, and Au-vol 7%Pt DMMC samples were prepared by a powder metallurgy technique. All specimens were processed into wire by extrusion, swaging, and drawing. The smallest final diameter of these wires was 120 ?m. Thermal stability was analyzed by electrical resistivity measurements to determine the relation between transformation rates and time at elevated temperature. The extensive deformation used to produce these composites reshaped the initially equi-axed powder into filaments that are 30 to 100 nm in diameter and 16 to 180 mm in length. The small filament diameter confers high strength on the composite. The high conductivity can be explained by electrons flowing parallel to the filamentary microstructure aligned with the wire axis. Using the Avrami and Arrhenius equation relationships, it is possible to predict the times and temperatures needed to achieve various degrees of homogenization. The Au DMMC's were found to have good thermal stability compared to conventional coldworked Au interconnection wires. Although these composites will revert to solid solutions if exposed to high temperatures for prolonged time periods, their relative stability is sufficient to allow them to maintain their twophase microstructure during the anticipated lifetime temperature profiles of many products.

Oct 1, 2003

By Damian Connelly

The option to leach iron from low grade copper concentrates could reduce transport costs and significantly improve the saleability of the concentrate. In addition, it reduces smelting costs and can remove undesirable impurities. The trend to produce cleaner and higher grade copper concentrates is very appealing to the smelters. A recent copper project came on line and there were three serious deficiencies which were not identified in the feasibility study. This came as a surprise and resulted in a number of projects to investigate ways of rectifying the problems in the shortest timeframe possible and using minimal new capital. The first serious issued not identified when commissioning was the lower than expected copper recovery, which was 70% compared to a predicted recovery of 80% to 87% in the feasibility study. This required investigating new flotation reagents and incorporating controlled potential sulphidisation. The second serious issue overlooked is the presence of significant amounts of talc minerals (insol) in the ore which are naturally floatable. This leads to lower concentrate grade and attempts to remove the talc resulted in lower copper recovery. Smelters have limits on the amount of talc in concentrate because it produces viscous slags and difficulties for the smelter. It also incurs higher transport costs. The third serious issue not identified in the feasibility study was the high arsenic reporting to the concentrate. Arsenic is a penalty element for smelters and at levels exceeding 0.3% the smelters may reject the concentrate. Arsenic is a problem environmentally for copper smelters and penalties apply when it is high. This paper describes the options for penalty element removal and suitability to incorporate into the modified flowsheet. It also highlights where the geometallurgy was not properly addressed and how these surprises could have been avoided. INTRODUCTION From 1970 to 1985, a copper company undertook metallurgical testwork on the Peruvian project copper ore. The ores were mined underground and treated over many years previously. Various other groups undertook studies and work until Aker Kvaerner undertook a feasibility study in 2006. Three ore composites were tested and grind-recovery relationships were developed. The feasibility study testwork identified that talc was a possible concern and will have an impact on copper concentrate grade. This was to be managed by blending. The current operating reality is that there is so much talc in the ore body it is not possible to blend it out. There was far more emphasis on molybdenum recovery. No mention was made of arsenic issues other than blending. There was a Concentrate Leach Study and a Molybdenum Hydrometallurgical Plant Study but these options did not proceed to a final flowsheet. A Scoping Study in 2006 looked at a Heap Leach project. The heap leaching gave very poor copper recovery on the sulphide ore. Heap Leaching was evaluated and tested for the high talc and high arsenic ore but recoveries were poor. The Aker Kvaerner feasibility study opted for a simple primary crush SAG/ball grind followed by flotation and sale of a concentrate. This is the current flowsheet utilised and the scale of the project is very large based on processing 117,200 tonnes of ore per day. A feasibility study does not guarantee success and the deviations from the feasibility study suggest there is a lot of technical work required to improve the current metallurgical performance.

Jan 1, 2019

By F. Hassani, J. Peck, D. J. Lucifora

The performance of a rotary blasthole drill is heavily dependent on the material being drilled. This material is a microcosm of the in-situ geology that makes up the surface mine in which the rotary blasthole drill is deployed. The performance metrics that are influenced by the in-situ geology are penetration rate (distance drilled per unit time), rotary torque and to a lesser extent rotary speed and vibration. For simulation and testing purposes it is useful to have a validated plant model based upon the application of study. Once validated, a plant model can be used to perform simulation based testing as a supplement and possibly in place of more expensive and logistically complex field testing. Previous studies in the field of rock mechanics have supplied proven models that relate the performance of a rotary blasthole drill to the material being drilled for a given rock type with a given drill bit. In this study, field based experiments were conducted in an active surface mine on a working rotary blasthole drill and the corresponding monitoring while drilling (MWD) data was recorded. Data analysis was then performed on the collected field data. The techniques used successfully fit the collected MWD data to the previously proven rock mechanic models. This paper explores the theory relating rotary blasthole drill performance to the material being drilled, illustrates the required data collection and data analysis techniques, and demonstrates the ability of these techniques and the known rock mechanic models to provide a simulated plant model for the drilling process that can then be validated. This validation is also discussed.

Jan 1, 2015

By Andrew D. Lapworth

The use of geological and grade models has been standard practice in mine design for many years now, with a wide range of software available to create and analyze the models. Although geotechnical parameters are also of vital importance for mine planning, there has been very little in the way of commercially available systems for integrating geotechnical data into the mine planning and design process. Sirovision is a new technology based on digital photography for automated, safe and accurate 3D mapping of geological and geotechnical features in rock faces. Datamine has integrated this capability into its product range so that Sirovision becomes an integral part of day-to-day face mapping, mine geology and geological / geotechnical modeling in both open pit and underground mines. This results in improved fragmentation for loading, hauling and processing, and for open pits local geotechnical conditions can be taken into account to improve slope design and control. This paper describes some of the ways that geotechnical modeling can be used to create more refined and cost effective mine designs and then discusses the role of Sirovision in enabling the raw data required for such modeling to be collected quickly, safely and reliably.

May 1, 2007

By X. Cao, M. Xiao, M. Jahazi

Magnesium alloys have low hardness, wear, erosion and corrosion resistance. The repair of service-damaged aerospace components made of magnesium alloys is an attractive solution in terms of time and cost saving. The feasibility of applying laser beam technology to repair ZE41A-T5 magnesium alloy sand castings in the machined surface conditions was studied using a continuous wave 4 kW Nd:YAG laser system. The influence of process parameters such as laser power, cladding speed, wire feed rate and defocusing distance on the shape, size and area of single cladding beads is discussed using a process optimization software. Sound single clad beads with good geometric characteristics were obtained using strictly controlled laser process parameters. The overall results indicate that laser surface cladding using filler wire has the potential for repairing aerospace components made of cast magnesium alloys.

Jan 1, 2006

By Laxman M. Amaratunga, Glen G. Hein

"Most mining operations utilize the tailings coarse fraction for backfilling while the fines have been traditionally disposed on surface in tailings ponds. Recently, paste fill has been developed which uses a fraction of the fine tailings (10-30% w/w of <45 µm) in the fill (Brummer and Moss, 1991). This development allows a mining company to use a portion of the fines for backfill, but still requires surface impoundment of the unused tailings. Reactive tailings have the added problem of generating acid after being oxidized in the presence of air and water. Treating acid mine drainage (AMO) from these ponds has proven to be a costly environmental problem and a long term liability.One practical method to reduce the environmental impacts associated with the tailings pond is to modify the physical and chemical prope1ties of the fine tailings so that they can be utilized in an environmentally safe manner. This was accomplished by agglomerating the tailings into pellets and using theses pellets as a coarse aggregate in a total tailings paste fill. This technology does not require any supplemental sand or gravel to be added to the fill.This paper presents the ongoing research into utilizing these tailings agglomerates as a coarse aggregate fraction, in order to create a total tailings paste fill which has supe1ior strength characteristics.IntroductionThe Canadian mining industry produces more than 500 million tonnes of tailings and waste rock annually. The waste rock is usually returned underground for use as rock fill in underground support with the tailings remaining to be disposed of in tailings ponds. Tailings consist of a coarse and fine fraction, and can be either reactive (acid generating) or non-reactive. In an effort to minimize tailings disposal, the coarse fraction has been used underground in backfill along with alluvial sands. This diversion of the coarse fraction, however still requires that the fine fraction be disposed of in tailings ponds. This disposal creates the potential for acid mine drainage (AMO), since in the presence of air and water, reactive sulphide tailings can generate acid. It is therefore an important goal in the mining industry to minimize the disposal of fine tailings into tailings ponds since the treatment of AMO is a costly and long-te1m environmental liability."

Jan 1, 1997

By O. Benavente, M. C. Hernández

Selenium is obtained mainly from copper anode slimes, which is a by-product of the copper electrorefining process. Selenium is present in copper anode slimes as silver and copper selenides. Traditionally, selenium has been obtained by pyrometallurgical processes; however, hydrometallurgy has now been incorporated either full or partial to the conventional process. Some hydrometallurgical processes are been developed and used at laboratory level an industrial scale. This document describes theoretical background and results of characterization and dissolution of selenium from a decopperized anode slimes in an alkaline oxidizing system. The results have indicated that the oxidizing leaching process reaches a practically complete dissolution of selenium (up to 90 %); the undissolved portion is due to the generation of a AgCl around the particle surfaces that delays the progression of the reaction. The results indicated that 90% of selenium extraction can be obtained by dissolution under moderate conditions of pH, temperature and reagent concentration in oxidizing medium. INTRODUCTION Selenium is distributed in the earth's crust in most rocks and soils. Selenium is essential, as it has wide range of applications in the medical and food industries as well as, used in semiconductor, sensors and photochemical devices. Selenium is rarely found in the native state, 90% of selenium is obtained from copper anode slimes, which is a byproduct of the copper electrorefining process (Lu, Chang, Yang, & Xie, 2015; Xiao et al., 2017; Yang et al., 2018). In anode slimes, selenium is present as an intermetallic compound, as Ag-Cu selenides. Currently, selenium is recovered from the anode slimes via hydrometallurgical and pyrometallurgical processes (Lu et al., 2015). The traditional pyrometallurgical method recovers selenium effectively, but faces difficulty as a result of increased energy costs and strict environmental regulations associated with the process (Li, Yang, Jin, Chen, & Tong, 2017). Therefore, hydrometallurgical processes are proposed in oxidizing medium such as nitric acid, alkaline leaching with sodium nitrate, wet chlorination and pressure leaching, amongst others (Hait, Jana, & Sanyal, 2012; Kim & Wang, 2010; Xiao et al., 2017; Yang et al., 2018).

Jan 1, 2019

By P. Woo, N. Brodusch, R. Gauvin, H. Demers

For developing new technologies, it is important to characterize the microstructure of materials with high spatial resolution at the nanoscale. To achieve high resolution, field emission scanning electron microscopes (FE-SEM) were developed. These microscopes allow working at low accelerating voltage, below 5 kV, to take advantage of the reduction of the interaction volume with accelerating voltage. Furthermore, their higher gun brightness compared to conventional thermo-electronic emitters, allow a probe size at the nanoscale. At low accelerating voltage, the emission volume of backscatter and secondary electron (SE) of the type II signals approach that of SEI signals. However, it is not enough to reach the highest resolution. A magnetic field above the sample improves the spatial resolution by collecting mostly high-resolution signals. In addition, the energy-filtration of the electron signals allows selecting the type of contrast detected: topographic, compositional, or crystallographic. The development of these new technologies permits to extend the imaging capabilities of the SEM towards new nanoscale applications.

Jan 1, 2014