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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 L. Zeka, I. Ndala, J. Frenay, S. Gaydardzhiev

"Reductive leaching of cobalt (III) from a heterogenite bearing ore has been performed. Pyrite was added to the system and simultaneously bioleached in order to provide ferrous iron as reducing agent. Within such arrangement the iron ions are continuously re-circulated inside a Fe 3+ / Fe 2+ loop. As a result Co(III) is solubilized in the presence of Fe 2+ ions in concentrations well below the stoichiometric requirement. The ore has been initially subjected to acid pre-leaching in order to guarantee that the available Co (II) has been entirely removed. Two technological parameters have been studied to show influence on the degree of cobalt leaching: concentration of ferric iron in the inoculum and the presence of bacteria. The bacterial role could be mainly viewed in supplying ferric ions in the system which chemically react with the pyrite to generate ferrous ions used as Co(III) reducing agent. Co(III) dissolution has been less efficient when the concentration of total iron in the system was low, but also when microorganisms were absent. SEM observations on leached heterogenite have evidenced bacterial attack on the mineral; however the precise role of bacterial presence on cobalt (III) leaching is still to be elucidated.INTRODUCTIONCobalt accompanies quite often copper in secondary oxidized ore deposits (Rumbu, 2013). In such associations cobalt is found both as CoII+ as well as CoIII+ (Deliens, 1974). In contrast to cobalt (III), cobalt (II) is leached relatively easy in sulphuric acid solutions. Cobalt (III) when present in mineral form belongs to the heterogenite mineral group with a simplified chemical formulae Co2O3.H2O or CoOOH. In order to be brought in solution, heterogenite should capture two electrons, likewise shown in reaction 1 below:"

Jan 1, 2016

By Barry W. Schmitke, J. M. Marino

"Cigar Lake Mining Corporation is presently operating an underground test mine in northern Saskatchewan, with a view to developing a high grade uranium deposit. The mining test is intended to demonstrate that the innovative mining methods designed are safe and economical. Two vertical mining methods are considered for the test:• box hole boring from the lower level;• blind boring from the upper level.In both cases, it is anticipated to freeze the ground before excavation to ensure hole stability and limit the inflow of water. Special care will be taken to minimize radiation exposure of personnel.Remote controlled equipment will be used where applicable.The access to the orebody was an important component of the test. After shaft sinking to a depth of 500 m, development work commenced at the 420 level in fractured sandstone which was grouted to restrict the inflow of formation water. The drifting continued in a section of poorly consolidated sand, clay and sandstone; this area was frozen to allow stabilization prior to excavation. At the 480 level relatively little water was encountered in the altered basement gneiss and grouting was not necessary; however, extensive ground support was required in the soft ground areas."

Jan 1, 1992

By Yugo Mitani, Tatsuya Kato, Chiharu Tokoro, Abdullah Al Mamun

Acid mine drainage (AMD), which is a major source of mining pollution, often contains ferric and/or ferrous ions together with several toxic elements. The ferric and ferrous ions in AMD precipitate in several mineralogical forms after neutralization, and the ferric/ferrous precipitates become the main component of the sludge generated after AMD treatment. The precipitates are also good absorbents for several toxic elements. To avoid generation of voluminous sludges and the re-dissolution of toxic elements from the sludge, it is very important to generate well-draining and efficiently adsorbing sludges by controlling the mineralogical form of the ferric/ferrous precipitates. Green rust, which is ferric and ferrous hydroxide, is a double layer hydroxide which is able to sorb several toxic elements. The green rust transforms to goethite or lepidocrocite by rapid oxidation, whereas it transforms to magnetite at ambient temperature by slow oxidation. The magnetite is also good absorbent especially for toxic cations and it makes a compact sludge due to its magnetic properties. We investigated the magnetite generation process at ambient temperature in detail. The magnetite generation process can be divided into three steps; (i) oxidation of Fe(II), (ii) Fe(II) surface complexation to Fe(III) hydroxide, and (iii) crystallization of magnetite. More magnetite can form when the oxidation rate is slower than the crystallization rate, and optimum conditions for its formation are at pH 9.5 with mild agitation. Ferrihydrite is the most common precipitate and it is able to sorb many different toxic elements. However, it drains badly and its solid/liquid separation properties are poor. We investigated the removal mechanism of several toxic elements by co-precipitation with ferrihydrite. We confirmed that the removal mechanism by co-precipitation partly involved surface precipitation when the initial ratio of toxic elements to ferric ion was high, although the main mechanism was always surface complexation. When surface precipitation occurred, highly efficient toxic element removal with ferrihydrite could be achieved.

Jan 1, 2016

By G. W. Poling, E. M. Coelho

"Sedimentary phosphate ores make up approximately 87% of the world's known reserves and are generally more difficult to beneficiate than igneous ores. In almost all cases, desliming prior to flotation represents the major source of losses. Laboratory studies of selective desliming of sedimentary ores are presented. Some fundamental studies with pure mineral systems are also discussed. Selective desliming, especially using selective flocculation, gave the best performance. Possible industrial applications of this selective flocculation-flotation procedure are discussed.IntroductionPhosphate ores are a major source of raw materials used in inorganic fertilizers (which supply nitrogen, phosphorus and potassium). Approximately 96% of the total world production of phosphate is utilized in the fertilizer industry. Reserves and production data are available in the literature. Today deposits with grades as low as 4% P2O5 are exploited in a few cases. However, in some northern African deposits, ore grades are still as high as 33 - 35% P2O5. Hout pointed out in 1982 that approximately 200 million tonnes of phosphate ore were upgraded by flotation only.Although there is a large number of phosphate minerals (over 300, only those in the apatite series are important ore minerals in phosphate ores. The most common member in this series is fluorapatite – Ca5(PO4)3F. However, in sedimentary phosphate rocks, many different substituents occur in the apatite lattice. Carbonate-fluorapatite (or francolite) is one of the most common names used to describe sedimentary apatites. It can be represented by the empirical formula:"

Jan 1, 1986

By S. W. Henley

"Shaft sinking design is typically driven by what has been successful in the past and the availability of sinking plant. This document considers a project where the sinking design and methodology is unconstrained by conventional thinking and removed from the commonly held belief that a sinking methodology should be developed from available winding plant. Schedule was a key driver for the Project and led to an alternative sinking design that aimed to optimise sinking advance rates by specifying new winders that compliment known sinking plant while providing improved safety, redundancy and flexibility within each part of the sinking cycle. KEYWORDS Consistent, Efficient, Flexible, Improved, Innovative, Optimise, Redundancy, Safety, Schedule INTRODUCTION The project is remotely located in the South Gobi region of Mongolia on a brownfield site and the scope of work included the concurrent blind sinking and concrete lining of two (2) ventilation shafts to an approximate depth of 1,150 m at a finished diameter of 10 m and 11 m respectively. All sinking and lining operations to be completed as in-line activities, (no lining whilst other activities are undertaken). The project was schedule driven with a completion date set for the first quarter (calendar) of 2021 and there were no restrictions imposed on the successful Contractor with respect to their equipment selection. Existing sinking plant already onsite from three previous shaft sinking operations would be made available to the Contractor if required on an as is where is basis Sustained advance rates in excess of 2.4 m per day would be required in order to achieve the completion milestone, therefore the design would have to include contingency and demanded flexibility to account for equipment down time. Previous shafts that had been sunk onsite have utilised a single double drum kibble (bucket) winder (hoist) with a single excavator loading on the shaft floor into a large capacity kibble (bucket). DESIGN Mucking The sinking design centred on the mucking cycle given that this is traditionally the most restrictive part of the sinking cycle and typically accounts for one third of the overall sinking cycle. The Vertical Shaft Mucker (VSM) and/or diesel excavator are commonly used plant for shaft sinking that were under consideration. The use of Cactus Grabs was not considered given the higher risk associated with grab ropes and hoist failures."

Jan 1, 2019

By Robert B. Parsons

"This article addresses the relationship between mine evaluation, the tax system, and economic risk. It is based on a paper presented by the author at recent seminars in Moscow and Tashkent on the subject of mine evaluation.IntroductionTaxation can have a strong influence on the feasibility of a mining project. For the most part, because metal prices are determined on a global basis, the mining concern is not able to pass on to its customers any portion of taxes which the concern has to pay. Taxes are a direct charge against the project. The purpose of the article is to highlight the various ways whereby different taxes can affect the financial viability of a mining operation.The first part of the paper identifies different forms of taxation, and the second part of the paper addresses the different forms of taxation in terms of risk analysis and impacts on the mining project. Finally, the third part of the paper makes brief mention of using the taxation system to provide incentives with respect to investment in mining activities."

Jan 1, 1993

By K. S. Raja, F. Battick, B. Pesic

"CeO2 doped with lower valence cations, such as Y3+, Sm3+, Gd3+ etc. is considered as electrolyte material for low temperature SOFC. Doping introduces additional oxygen vacancies and improves ionic conductivity. This work describes the preparation of yttria-calcia doped-ceria precursor material, its sintering in DC and AC field methods, and characterization of sintered electrolytes with respect to the ionic conductivity. Doped precursor materials were prepared by a controlled co-precipitation process. Sintering of prepared, pelletized particulates was carried out using three different methods such as: 1) conventional; 2) spark plasma sintering; and 3) an alternating current field at 1125°C (AC assisted sintering). The mechanism involved in the conductivity improvement as a function of defect density, grain boundary area and phase stability will be discussed. INTRODUCTIONThe performance of SOFCs depends highly on the properties of materials. Subtle variations in the composition, microstructure, or density of SOFC components can considerably alter the power output capabilities of fuel cells. Early SOFCs utilized zirconia based electrolytes but efforts in lowering the operating temperatures of SOFCs have prompted investigations into several other oxygen ion conductors – often modified with dopants to either promote the formation of oxygen vacancies or to stabilize a vacancy rich high temperature phase – such as bismuth oxide, lanthanum gallate, and ceria.The transport of oxygen ions through the electrolyte first begins with diffusion into the material. While this is generally a surface kinetics phenomenon, it is safe to say that it is highly dependent on oxygen pressure and vacancy gradients. The role of the cathode in SOFCs is to reduce oxygen at the electrolyte surface creating an O2– ion gradient which induces permeation into the material. Once inside and under the influence of a potential field, O2– ions migrate by a vacancy hopping mechanism, Catlow, C.R.A. (1990), effectively exchanging positions throughout the matrix until they reach the anode and react, thus leaving the matrix."

Jan 1, 2012

By M. S. Greenfield, E. Cocchiarella, S. Chubbs

"At Dofasco sNo.4furnace a variation of the basic oxygen steelmaking process, Klockner Oxygen Bottom Maxhutte (K-OBM), is used to produce steel. Large amounts of hot gases and particulate are evolved during the oxygen blowing phase. A quencher and a venturi scrubber are used to collect over 99.5% of the particulate. In 1990, the authors investigated the effect of foamy slag on the particulate emissions from the furnace. The amount of lime added early in the oxygen blowing cycle was reduced, making the slag more viscous and foamy for a six minute period. Instantaneous particulate emissions were monitored throughout the blow by analyzing quencher and venturi scrubber water samples. Particulate emissions were reduced up to 59% during the foamy slag period.IntroductionThe reduction of the amount of waste generated or control of emissions at source is at the top of the ""3R"" hierarchy of waste management (Reduce, Reuse, Recycle). Process and operating practice changes are often the most economical ways to control emissions. At Dofasco, they investigated the effect of operating practice changes, specifically the formation of a foamy slag, on particulate emissions from steelmaking furnaces. They wanted to determine if a foamy slag changed the quantity and nature of the fume evolved from the K-OBM furnace over the oxygen blowing phase.The Basic Oxygen Steelmaking ProcessesThe basic oxygen steelmaking process (BOP) generates large quantities of very fine metal oxide fume during the production of steel. In this process, scrap steel and molten iron (hot metal) from blast furnaces are charged into a steelmaking furnace. Then pure oxygen is injected and a lime flux added . The oxygen reacts with carbon dissolved in the molten iron to form carbon monoxide. Oxygen lances can have secondary nozzles which introduce oxygen above the bath. This secondary oxygen, known as post-combustion, bums some of the carbon monoxide radiating the heat back to the bath. Particulate and gases rich in carbon monoxide are ejected from the furnace during the oxygen blowing phase and are collected by a gas cleaning system. Typically, more than 99.5010 of the particulate is scrubbed from the gases by high energy venturi scrubbers or electrostatic precipitators. The oxide sludge or dust collected may have elevated zinc and lead which is unsuitable for recycle to blast furnaces. Due to the presence of these undesirable elements, treatment and disposal of steelmaking oxide dust is difficult and costly."

Jan 1, 1993

By Celine Y. Zhang, Chloe J. Feng, Charles Q. Jia, Donald W. Kirk

Oil sands petroleum coke (OSPC) is a by-product of coking - a high-temperature process that converts the mined bitumen to the synthetic crude oil (SCO). For every barrel of the SCO produced, about 20 kg of OSPC are generated. Over 70 million metric tons of OSPC have been produced and stockpiled as a result of the development of oil sands industry in the past few decades. Unlike conventional petroleum coke, OSPC has uniquely high impurity contents, particularly sulphur (~ 7 wt%) and metals (e.g. vanadium at ~0.15 wt%), which has hindered its large-scale applications as a solid fuel. Vanadium is a valuable metal that is widely used as an alloy for strengthening steels. The stockpiled OSPC contains about 100,000 tons of vanadium, while the world’s production in 2013 was only 75,600 tons. At the current price of $25US/kg, the OSPC-bound vanadium represents a total value of $2.5 billion US dollars. In this work, we investigate the technical feasibility of extracting vanadium from OSPC. The work focuses on the characterization of vanadium in OSPC and the conditions for effective extraction of vanadium from the OSPC.

Jan 1, 2015

By Stefan Boshkov

THE ADVENT of mining at great depth has brought to the fore the question of stresses around mine openings. The many-pronged attack on this problem is certified by the accelerated appearance, in the mining literature, of articles on various topics related to this subject (1). Whereas it may be agreed that we, of the mining profession, have fallen woefully behind in research and the development of an understanding of this important facet of the general problem of mining, it must also be accepted that the analysis of the stresses in a mine structure is usually more complex than is the case in the majority of structures encountered and dealt with in civil engineering. Whereas homogeneity and isotropy are readily acceptable for most metals, such properties are but crudely approximated in rocks. Whereas the external loads on a structure in civil engineering may be readily determined, those on a mining structure are subject to ?conjecture. Whereas the limits of the structure may readily be defined in civil engineering, the boundaries of the mining structure are, in most cases, indeterminate, and subject to intelligent guesswork, at best.

Jan 1, 1956

By M. Tadie, J. Wiese, K. Corin

The use of potential control in the flotation of ores has been applied in a variety of operations and presents an opportunity for improvement of selectivity and recovery of valuable minerals. Although it is possible to vary the redox potential (Eh) using chemical additives such as sodium hypochlorite or hydrogen peroxide this is more commonly done by varying the pH and dissolved oxygen (DO) concentration. The present study involves an investigation into the effect of varying dissolved oxygen concentration, ionic strength (IS) and pH on the flotation response with the aim of application to a South African lead-zinc ore. In all cases the Eh is measured as a function of the different DO, IS and pH values. The main objective was to achieve selective flotation of galena from sphalerite. The first part of the work was micro-flotation tests conducted on single minerals with galena used as the basis for effect of the factors studied on redox potential and ultimately recovery. The DO was varied by alternating between the use of air and nitrogen as the gas source to the micro-flotation cell. PH was varied between pH 9.2 and pH 11.8 using sodium hydroxide. In the first part of this study a factorial design approach was used to determine the interactive effects of the variables tested, viz. DO, ionic strength and pH, on the Eh and on the recovery. Redox potential was measured using a combination electrode made up of platinum wire and Ag/AgCl reference combination. Recoveries indicated that pH had the most significant effect on recovery and Eh. The influence of redox potential on recovery was found to be of relevance to the condition of high dissolved oxygen concentration and less so at low dissolved oxygen concentrations. It was also noted that that the combined interaction between ionic strength and dissolved oxygen concentration had a positive effect on recoveries, however this was not so with Eh. The chemistry of the ions in solution was observed to play a dominant role on the recovery due to changes in solubility arising to pH modification. The longer term objective of this work is to determine the optimal Eh conditions for the separation of galena from sphalerite.

Jan 1, 2016

By Ben Sheneider

AT THE Flin Flon plant of the Hudson Bay Mining and Smelting Co., Limited there are two types of multiple hearth furnaces used in the roasting of sulphides. This pa-per will deal primarily with the wedge-type furnace in the roasting of zinc concentrates. The other furnace, the Nichols-Herroshoff type, is used in the copper smelter and is described in the papers given by (1) J. H. Ambrose in 1935 and (2) R. E. Mast and G. H. Kent in 1954. The design and operation of these roasting furnaces at the present time is essentially the same as given in the write-up in 1954. No at-tempt will be made here to describe these furnaces, except to mention that there are five Nichols-Herreshoff multiple-hearth furnaces, four of which are used to roast a dried mixture of copper concentrate, zinc plant residue, and flux, before this material is fed to the reverberatory furnace.

Jan 1, 1961

By B. T. Lu

The corrosion and wear properties of a series of chrome white iron (CWI) castings were study using electrochemical and low-stress sliding abrasion tests. The results confirm that the corrosion resistance of these materials is largely dependant on the quantity of chromium in the matrix, while the wear resistance is mainly controlled by the volume fraction of chromium carbides. A pseudo-wear/corrosion map is developed to identify alloy compositions that may be suited for erosion/corrosion conditions.

Jan 1, 2005

By Jeremy Breker

Cameco aligns its social and environmental responsibilities with its vision, mission and values. Environmental Leadership is established as a corporate objective that emphasizes the triple-bottom-line and a systematic approach to understanding environmental, social and economic issues, risks and opportunities. These are ingrained in the project culture, systems and processes and used to influence solutions derived by the project teams to achieve Cameco's objectives. This paper traces the organizational objectives from the early stages of a project through to implementation and turn over to Operations. A case study is used to demonstrate how an asset is influenced by Cameco?s strategy.

Aug 1, 2010

By J. Schnarr, D. Deever, E. Johnson

"The above committee sent out a questionnaire to the gold mines for the purpose of learning what units and methods are currently in use in the mines as the first step in an attempt to agree on standard units to be used in any papers or reports that may be given to other mines or presented at meetings. The next step is to try to arrive at acceptable standard units for reporting and methods of making tests. It was suggested by Mr. J. Jardine of Eldorado Mining and Refining that the use of the metric system should be seriously considered. It was also brought out that there was no intention of having any mine change their methods to the standard for internal reporting as this would involve too much change. However for external reporting there shouldn't be too much difficulty in converting to the accepted standard units.On the following pages are the reports of those mines that replied to the questionnaire.MALARTIC GOLD FIELDS LIMITEDP.A. Coulter1. All assays - Ounces per ton2. Consumption of reagents - Pounds per ton3. Reagent strength of solutions - Pounds per ton4. Reducing Power - As described in C 0 I.L, Analysis of Cyanide Solutions5. Pulp Densities - Grams per litre6. Screen Analysis (Tailings) A sample of 150 gms is washed on a 200 mesh screen. The plus 200 mesh material is dried and ro-tapped for fifteen minutes. The plus 200 mesh portions are weighed cumulatively (the balance is considered -200 mesh) and reported in per cent."

Jan 1, 1967

By J. Schmidt

The development of set of laboratory experiments, intended to help undergraduate students meet Canadian Engineering Accreditation Board requirements for Engineering Design outcomes, is described.The laboratory, which is part of a third year level course in hydrometallurgy, is aimed at advancing the ability of students to generate and use experimental results to design an industrial copper leach/SX/EW plant. Emphasis is placed on the students demonstrating the ability to use of their engineering knowledge in weighing the pros and cons of the various process options that they test in converging to a final flowsheet. INTRODUCTION Over the past number of years the Canadian Engineering Accreditation Board, CEAB, has dramatically shifted the way that they evaluate undergraduate programs. In the past, the focus was on measuring of the quantity and quality of material the students were intended to learn as well as the methods and resources used to deliver that material. Now, rather than principally evaluating the inputs of programs, the focus is more on measuring the quality of the outputs from the programs, i.e. the quality of graduating students. In this regard, the CEAB has developed a list of twelve attributes that learners must develop in the course of their studies. Engineering programs must, not only demonstrate that their curriculums provide opportunities to develop these attributes, but must measure student proficiency in each of these attributes as they progress toward graduation. One particular graduate attribute that Laurentian University’s Bharti School of Engineering has encouraged its faculty members to develop content for is “design”. Engineering Canada (2018) defines this attribute as “an ability to design solutions for complex, open-ended engineering problems and to design systems, components or processes that meet specified needs with appropriate attention to health and safety risks, applicable standards, and economic, environmental, cultural and societal considerations”. The previous laboratory component for the hydrometallurgy course was a collection of unconnected experiments covering leaching, solvent extraction, ion exchange, and electrowinning. Like in other undergraduate courses, students would perform stand-alone experiments, make the specified measurements, do the specified analyses of the results, and report the findings, all as strictly detailed in the lab manual. The vision for the new lab was to create an experience that would more closely mimic an industrial research program whereby students would start with a given feed material and would progress through a series of connected experiments. Emphasis is placed on the student demonstrating competency in, not only, generating and analyzing experimental data, but also in using the data along with their engineering knowledge to design and evaluate the pros and cons various plant configuration options. Principally, students are asked to weigh cost, safety, and environmental concerns in converging to their final flowsheet. In designed the leach circuit, students must weigh the costs/benefits of varying leach temperature. Higher leach temperatures will yield faster and more complete copper dissolution, which will allow for the specification of relatively smaller leaching circuits, saving capital costs. However, hotter acid solutions are more dangerous to handle and require increasing amounts of energy to heat the slurry, increasing operating costs. In solid/liquid separation, students must weigh the pros and cons of the addition of a flocculent to assist settling. The flocculant will allow for the design of a thickener circuit that employs units with a relatively smaller area, but will result in a thickener underflow with a lower pulp density, which may necessitate a larger number of thickeners. In addition, the environmental concerns of producing a tailings product that contains an organic contaminant should be addressed. In solvent extraction, students must specify the number of stages of loading and stripping, as well as organic and aqueous flowrates to produce suitable raffinate and rich electrolyte streams. Finally, in electrowinning, students will compare the costs/benefits and risks of the use of precious metal coated titanium dimensionally stable anodes (DSAs) versus conventional Pb based anodes.

Jan 1, 2019

By S. Duvah Pentiah

The transformation of an open pit coal mine to a horizontal-punch underground mine is subject to a number of challenges. These include scheduling the operation of various sizes of trucks over a long period, as well as updating delivery routes and dump site locations as the mine transformation progresses. In this process, rock is excavated from a quarry through earthworks. The bulk earthwork and quarry material delivery were initially drawn from traditional planning and experienced issues in their early phases. As a result, a traffic simulator was developed in order to validate schedules and predict achievable throughput, likely delays or blockages in the long term. The dynamic traffic simulator was also used to provide traffic density and vehicle arrival data at selected intersections in order to identify possible safety and efficiency issues.

Aug 1, 2013

By T. G. Joseph

The strain softening relationship developed in part 1 is now applied to coal. Having determined the post-failure stress-strain curve for coal specimens, this information can then be used in a finite element program, such as Phase 2, to examine the post failure characteristics of coal pillars. Using example data, the strength of coal pillars of different width/height ratios are estimated and compared with well-known empirical pillar size-strength relationships. In addition, the post-failure stress-strain behaviour of a coal pillar is compared with an empirical relationship reported in the literature.

May 1, 2002

By Wei Zhang, Jinhong Zhang

"The adsorption of ethyl xanthate on copper sulfides, i.e., chalcopyrite, chalcocite and bornite, has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). AFM images show that xanthate, such as potassium ethyl xanthate (KEX), adsorbs strongly on chalcocite and bornite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This adsorption mechanism is totally different from the one obtained with chalcopyrite/xanthate system, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. The findings obtained from the present AFM study suggest that an AFM image analysis is a powerful tool for the study of the collector’s adsorption on mineral surface and as well the development of novel collector for copper sulfide flotation.INTRODUCTIONIn mining industry, copper sulfide minerals, i.e., chalcopyrite, chalcocite and bornite, are usually separated selectively from non-valuable gangue by froth flotation, which treats the highest throughput and produces the maximum economic outcome of any surface chemistry process. In flotation, collectors are added into the pulp (mixture of water and fine-grained minerals) to selectively adsorb onto the target mineral and render its surface with high hydrophobicity, which is generally beneficial for a strong mineralbubble attachment and thus a high flotation recovery.The adsorption of collector on mineral surface, therefore, is vital for a successful flotation process and it has been studied by applying various surface analysis techniques, such as IR (Infrared Spectroscopy), CV (Cyclic Voltammetry) and XPS (X-ray Photoelectron Spectroscopy). (Poling, 1963; Allison et al., 1972; Mielczarski et al., 1984; Leppinen et al., 1989; Kartio et al., 1996) These studies have revealed a lot of information, such as the reaction, product and mechanism, of the adsorption of chemicals on mineral surface. It is also of great interest to directly get the image of adsorbed collectors on mineral surface changing with pulp chemistry, such as pH, redox potential, ionic strength and chemical’s dosage."

Jan 1, 2016