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By D. E. Deegan, G. Holcroft, T. P. Johnson

"The rising cost of extracting metals from existing traditional deposits, increasingly stringent environmental regulations and a greater awareness of corporate social responsibility issues are all factors in stimulating the examination of mine tailings and small-scale alluvial deposits as a potential source of new raw materials. Furthermore, despite tougher economic times the demand for commodities remains strong, in no small part as a result of the growth of the world’s emerging economies.This combination of social and economic factors looks set to continue in the long term which will encourage greater recovery of materials from previously ignored sources such as mine tailings and ores from alluvial deposits.An expansion in the recovery of useful materials from mining-related activities is likely to require the use of robust and innovative techniques that have a built-in degree of future-proofing; DC plasma technology is one such technology.As a result of its ability to separate the valuable metal and minerals from the waste material while destroying hazardous compounds, Tetronics’ DC arc technology offers an alternative approach to resource recovery from a wide range of mine ores. Harmful cyanide compounds and the vast quantities of water used in conventional hydrometallurgical processing are avoided when plasma processing is adopted. DC arc technology also brings additional benefits, including: the extremely effective destruction of organic materials, the conversion of the inorganic material into a re-useable aggregate and the high tolerance of the process to fine and dusty materials. This paper presents details of Tetronics’ DC arc technology as one of the key pyro-metallurgical solutions available for the recovery of valuable materials from traditional mine ores and tailings, as well as giving specific examples of how the technology has been successfully employed in the recovery of enriched slags, ferroalloys and other metals."

Jan 1, 2016

By J. F. Jackson, R. W. Mau

"The first commercial installation in the mineral industry of the ""Verti-Press"" pressure filter was made by Falconbridge Limited at the Strathcona Concentrator to filter copper concentrate. The filtercake produced contains 6 - 7% H2O, an improvement from the 12 - 13% H2O produced by an internal drum filter, at rates of up to 20 t/hr. A novel slurry feed system incorporates a hose pump and a pressurized slurry accumulator.INTRODUCTIONIncreased copper production from Falconbridge Limited operational mines in the Sudbury Area has exceeded the current refinery capacity. A copper concentrate has been produced to overcome this constraint and has been shipped to custom smelters either as a slurry or as a 12 - 13% moisture filtercake utilizing an internal drum filter.With the treatment of the new Deep Copper Zone from the Strathcona Mine, copper concentrate production was forecast in excess of the installed dewatering capacity. The filtercake was too wet to transport by truck and the custom smelter refused to handle this product at the truck unloading site. The filtercake had to be trucked to a rail spur and transloaded into gondola cars. This system was expensive, incurred unaccountable losses and the concentrate was assessed a moisture penalty.To reduce the concentrate moisture content to permit direct shipment by truck, two basic systems were available; vacuum filter followed by a thermal dryer or a pressure filter. Past experience with the high capital and operating costs of dryers led Falconbridge to closely examine the pressure filter alternative.COPPER CONCENTRATE PRODUCTIONThere are two separate circuits at the Strathcona Mill; one treating nickel ore and the other treating copper ore.The rougher concentrates produced by both circuits are conditioned with lime and cyanide before the copper-nickel separation in a flotation columns. The concentrate consisting of cha lcopyrite with mi nor cubanite is very clean as shown in Table I. Currently 50% of the copper in the plant feed reports as copper concentrate, in the past, this has been as high as 70%."

Jan 1, 1990

By Benoit Bissonnette, David Gelderland

"The Campbell Mine Constructed Wetlands has been in full operation, processing effluent from the water treatment plant of the mill circuit for the last two years.The overall results are extremely positive with dramatic improvements for the originally targeted parameters – Ammonia, Copper and toxicity.• Ammonia concentrations were reduced from an average of 5 mg/L to an average of 0.43 mg/L which translates to an average reduction of 91%.• Copper concentrations were reduced from an average concentration of 0.054 mg/L to an average of 0.019 mg/L, which translates to an average reduction of 65%.• LC50 Acute toxicity testing revealed no impact.• IC25 Chronic toxicity tests revealed no impairment to growth or reproduction.As a result of the improvements in discharge water quality from the wetland, 100 percent compliance with respect to all Certificate of Approval, MISA and MMER regulations for effluent will be consistently achieved.The system has proven to be very easy to operate and maintain, with a minimum of care. Given some basic rules are followed, the construction of the wetlands was straightforward and relatively inexpensive compared to other treatment methods.The ecological benefits of the operation of the wetland are also quite substantial, as is the positive image of the corporation in environmental stewardship.INTRODUCTIONOver the last four years, Campbell Mine has adopted an aggressive schedule for the development of wetlands for use as the final stage of effluent treatment within the tailings management facility. The focus of this work has been to utilize natural biological systems to provide Campbell Mine with a 100 percent compliant water quality with respect to all MISA, MMER and COA discharge criteria at all times throughout the effluent discharge period."

Jan 1, 2003

By John G. Henning

The Porcupine Joint Venture operates the Dome Mine in South Porcupine, Ontario. Dome underground began production in 1910. It is the longest continuous operating gold mine in Canada, producing in excess of 15 M ounces. More than 900 underground stopes have been mined and hundreds of miles of drifts, sublevels and raises developed. Underground mining methods included shrinkage, cut and fill and longhole. Not all stopes were backfilled upon completion, particularly the longhole stopes. The Dome open pit was designed above the underground mine workings such that, as the pit is excavated, it intersects underground drifts and stopes. Potential operational problems associated with the interactions between the stopes and the pit walls may occur, necessitating pit wall redesign, ground support installation and operational rescheduling. Each intersection of the pit with the underground mine workings is closely evaluated to maintain a safe working environment and wall stability. This paper discussed how risks to pit wall stability are assessed, mitigated and monitored.

May 1, 2004

By D. Imeson, T. Grammatikopoulos, M. Aghamirian, M. Oliazadeh

"More than 70% of potash is produced worldwide by froth flotation. Flotation of potash was developed in the early 1930s. Amines are widely used for flotation of sylvite (KCl) from halite (NaCl) and insoluble materials such as clays. Amine collector is also absorbed by clays. Therefore, clays are usually separated by scrubbing and de-sliming prior to flotation. Alternatively, slimes can be floated ahead of potash flotation. Flotation recoveries of sylvite are commonly in the range of 85%, while losses can occur in slimes, flotation tailings and make-up of process brine. Ores containing free coarse-grained sylvite are generally screened, whereas both fine and coarse fractions are conditioned and floated separately. The unique features of potash flotation include solubility of sylvite in water, the size of particles floated and fast kinetics. Particles up to 2.3 mm can be floated and about 50% of flotation feed can be removed in the rougher stage in few minutes. The main challenges in potash flotation are the recovery of potash from slimes, flotation efficiency in the presence of carnallite and recovery of coarse potash grains. A review of potash flotation shows that there is still room for improvement in both coarse and fine potash flotation. The present paper reviews the most significant flotation parameters including reagent type and dosage, flotation circuits, flotation equipment size and new developments in potash flotation. The latter include new reagents, flotation technologies (Hydrofloat, Jameson and column cells) larger flotation cells and slimes flotation.INTRODUCTION Potash is the common industrial term for potassium in various chemical combinations and minerals soluble in water. About 90% of potash produced worldwide is used as agricultural fertilizers. Flotation is the main treatment process of sylvinite (KCl-NaCl) ores for recovery of sylvite (KCl). Potash concentrate should contain a minimum of 95% KCl and be relatively free from 0.2 mm KCl fines. The flotation process for beneficiation of potash ores was developed in United States and Russia concurrently in the early 1930s. In 1934, Potash Corporation of America applied flotation process in a commercial scale (Tippin R.B. and Huiatt J.L). In the initial application, halite (NaCl) was selectively floated by employing lead chloride as an activator and soap as collector. The sylvite concentrate was reported in the cell underflow."

Jan 1, 2012

By Valentin Choquenaha Bombilla, Oscar Alvarez Muiloz

"Tintaya’s basic production line is copper concentrate, which has an important gold content. The process used is flotation; the objective of the metallurgical department is to obtain the best results in the copper recovery without neglecting the gold, using very specific reagents. Copper recoveries are considered high, nevertheless every day emphasis is placed upon increasing those recoveries. Regarding gold, optimum recoveries could not be achieved with flotation; and implementation of a gravity circuit was considered.According to microscopy studies, the coarse and very fine grains of gold in native form are lost to tails. The native gold due to its high specific gravity is concentrated at the underflow of the cyclone, remaining in the circulating load of the circuit. It reaches three times the concentration compared to the head grade entering the ball mills. This re-circulation generates very fine and laminated gold particles inside the ball mill, passing to the classification stage making a short circuit to the overflow of the cyclone.The very coarse gold particles as well as the thick flakes of gold do not react favorably to the conventional flotation process; thus studies that have included gravity separation have been conducted to increase the gold recovery. Part of the research included concentrating tables, jigs, and Knelson Concentrators. The Knelson Concentrator proved to be the best selection in terms of metallurgical performance and recoveries considering the throughput and operation conditions of the Tintaya Plant.The gravity concentration circuit with the Knelson Concentrator was commissioned in BHP Tintaya in October 1998, as per the flowsheet shown later on. Presently the global gold production surpasses any estimated expectations.Present efforts are directed towards showing the evaluation and optimization of the different parameters that govern the performance of the Knelson concentrator, as well as illustrating the difficulties and successes throughout the operating period.In the first year of operation 200 tons of gold concentrate have been produced with an average concentrate grade of 320 gramdton, having paid back in full the cost of the automated KC-XD- 48 Knelson Concentrator, the peripheral equipment, and the cost of the installation."

Jan 1, 2002

By R. W. Diamond

PUBLIC debts, and the policies guiding public finance in Canada today, are in such a state that every intelligent citizen should be familiar with them, and should be concerned about them. None of you have robe reminded that taxes have already risen to a point where they both annoy and hurt you, but they should also alarm you; alarm you, not so much because of the taxation, but because of the mounting expenditures represented by that taxation. I have no hesitation, therefore, in presenting a paper dealing with public finance at a meeting of the Mining Institute, since all present are concerned,. both as individuals and as representatives of the industry. Moreover, it is important that engineers, particularly, should become better acquainted with the interlocking relationships of economics, public finance, government, and technology. While I am neither an economist, a tax expert, nor a chartered accountant, I shall try to tell you, from my viewpoint as an engineer and an interested voter, the story of public finance in Canada today and of certain causes and effects, and I shall venture certain conclusions. In doing so I may merit criticism by experts, but I will risk this in the hope that sufficient interest will be stimulated in the subject to persuade you, as individuals and as groups, to advance, or to institute, your own studies in public finance, and in turn to interest others. I hope that some of the ideas which will be expressed, or which may develop, will bear fruit. I fully realize that several eminently qualified men have spoken on this subject during recent months, and that many authoritative articles have been written. However, I approach it with confidence, because I propose speaking to you not as an authority, bur as one of you, having similar interests and similar engineering knowledge, who only a few months ago became particularly interested in the subject, studied it, and who now sets before you a summary of his findings, with the conviction that the situation is so serious that constructive planning and constructive action by all thinking citizens are imperative.

Jan 1, 1939

By P. Quinn

"The Venturi-aerated flotation column (VAC) is based on a reactor and separator design for a new generation of flotation machines. The reactor is a Venturi tube, where the air/slurry contact takes place with intensive aeration for efficient particle collection. The separator is a column of 1-3 m length that provides quiescent hydrodynamic conditions for effective separation of bubble-particle aggregates from the remaining slurry.Aeration in the Venturi tube occurs via two mechanisms: air dispersion and nucleation (cavitation). By forcing air through a restricted passage with a fast flowing slurry stream, air is dispersed into fine bubbles. Bubble formation due to cavitation occurs on the surface of particles in the low-pressure section of the Venturi, from dissolved air contained in the liquid.Size-by-size recovery and flotation rate constants were determined for a small-scale laboratory Venturi-aerated flotation column. The results were compared to those obtained in a laboratory 2.2 L Denver cell. It is shown that the Venturi-aerated flotation column has slightly slower flotation kinetics to the Denver cell, but with much higher flotation selectivity. A portable Venturi-aerated flotation column can effectively be used to investigate process or equipment problems in operating plants.INTRODUCTIONFlotation processes can generally be divided into two sub-processes: 1) selective collection of hydrophobic particles by air bubbles and 2) separation of bubble-particle aggregates from hydrophilic particles that remain in the pulp. The methods of aeration, or bubble generation, control the mechanism of particle collection by either collision with, and subsequent attachment to bubbles, or by in situ bubble formation on the surfaces of hydrophobic particles. A flotation device should provide optimal aeration conditions for efficient particle collection and a suitable hydrodynamic environment for effective removal of bubble-particle aggregates from the remaining pulp."

Jan 1, 2002

By A. P. Fletcher, K. Croteau

The intent of this paper is to cover some aspects of preventive maintenance methods which have come into wider usage in recent years as a means of increasing operating efficiencies. Particular emphasis is placed on lubrication and related servicing.

Jan 1, 1967

By John Wilson

"The unconformity beneath 75 per cent or over 6000 km2 of the Athabasca Basin in Alberta lies within economically exploitable depths. The basement beneath this unconformity consists of an extension of the Wylie Lake Pluton, locally faulted and containing areas of mylonitic rocks. While the rocks of the Wylie Lake Pluton are not promising host rocks for uranium ore deposits, the areas of mylonites, graphitic rocks and possible remnants of granitegneiss would bear closer examination. One area of maficmylonites shows a weathering zone enriched in Si, Ca, Na, Pb, Ni, Ba, Co, Sr, Zn and U in addition to reported values of 0.08 oz/ton gold. This zone occurs beneath 800 m to 900 m of Athabasca Group sediments, but similar rock types are present beneath much thinner cover elsewhere. Detailed geophysical exploration is required over the area of thinner Athabasca Group rocks to define more precisely the areas of promising basement rock type.IntroductionThe Athabasca Basin in Alberta has considerable economic potential which has not yet been realized. The geological setting is closely analogous to parts of the basin in Saskatchewan which host major uranium deposits. Recent advances in geophysical techniques have led to deposits being located in Saskatchewan below 600 m of cover. This means that the unconformity between the Athabasca Group and the basement lies at exploitable depths over 6000 km2 or 75 per cent of the Alberta portion of the basin. Much of this area was only cursorily examined almost a decade ago. In addition, Alberta's new Metallic Mineral Regulations have clarified the regulatory situation in the area, and opened up much land for exploration. This article is based on Wilson's (1985a) study of the Athabasca Group and Wilson's (1986) work on the basement and alteration beneath the Athabasca Group in Alberta."

Jan 1, 1987

By M. S. Badollet

INTRODUCTION THE DEMAND for general knowledge on asbestos fibres has increased considerably in recent years. A few publications have printed data showing some of the physical and chemical prupertie3 of asbestos, but in many cases this information is difficult to find and is seldom available when needed. During the past ten years, Johns-Manville have received many inquiries on the physical and chemical properties of asbestos fibres. Fortunately, we had some of the information in our files, and we willingly supplied the data. To help relieve this need, we have tried to present briefly in this paper some of the interesting and out-standing properties of asbestos. This information was obtained over a period of years by search of the literature and by experimental investigations. PROPERTIES OF ASBESTOS FIBRES Table I (1, 2) presents, in convenient form for easy comparison, data on the principal properties of the several varieties of commercial 'asbestos' -actinolite, amosite, anthophyllite, chrysotile, crocidolite, and tremolite. Under each variety of fibre is a brief statement describing the properties in terms of structure, mineral association, origin, etc. Some of the more important data in Table I are expanded and presented in Table II (3). SOLUBILITY OF ASBESTOS A report ( 4, 5) discussing the effects of acids and caustic on asbestos fibres was published in Germany in 1927.

Jan 1, 1951

By John F. Gartner

"Traditionally, the geologists of Canada have been occupied with the tasks of finding new mineral bodies, locating gas and oil fields or hunting for economic deposits of industrial minerals. A very minor percentage of graduate geologists have applied their skills to solution of the ""urban blight"" or employing their understanding of ""Nature"" for the optimum use of land by mankind. However, things are changing quickly. The role of the geologist in the planning process is being established. It is an exciting time! Geologists are now being consulted on a wide range of urban planning problems. These vary, tor example, from assessment of the geological environment for the new communities of Erin Mills and Meadowvale, which will have total populations in excess of 100,000 people (truly a satellite city), to a complete geological/ geohydrological assessment of the new sanitary landfill for the city of Guelph.Use of geologic techniques and methods for urban studies must be enhanced with certain skills not taught, in the past, to the geologist. These include airphoto interpretation, soil mechanics, geohydrology, municipal engineering and highway engineering to mention a few. The geologist has the unique training to assess the natural environment and to discover, warn and explain the implications of man's attempt to command his environment."

Jan 1, 1972

By D. Pawelus, J. Butra, R. Debkowski, M. Szpak

Impact of horizontal stresses on stability of underground workings in mines is a very important issue in underground mining. Identification of the initial state of stress in the rock-mass should be one of the main actions taken into account while designing and carrying out the mining activity in underground mines. The paper presents the tests on three dimensional stress pattern in Polish copper mines, owned by KGHM Polska Miedz S.A. Group, carried out in 2012. The research program covered 7 measuring stands in two mines; their average depth was about 1000 m. The main aim was to identify the values and directions of horizontal stresses in order to optimize the extraction and to improve the safety. The overcoring method with the use of CSIRO HI type probe was applied. The paper also describes the measuring technique which was developed for the purpose of specific mining and geological conditions of KGHM mines, taking into consideration the natural hazards encountered there as well as technical and operational capabilities with regard to drilling equipment. The experience gained during the underground measurements and the issue of making such measurements in underground copper mines in Poland are presented in the paper. The stress patterns obtained during the underground measurements are of application importance for the process of designing the spacing of mine workings and improving their stability and mine support selection.

Jan 1, 2015

By A. S. H. Kabir

Due to the high specific strength and excellent corrosion resistance, Ti-6A1-4V has been widely applied in aerospace industries. In this study, the welding performance of 3.2-mm and 5.1-mm thick Ti¬6A1-4V sheets was studied using a 4 kW continuous wave Nd: YAG laser. It is found that the use of filler wire, matching the parent metal composition, can bridge the joint gap and produce full penetrated welds up to a width of 0.6 mm without cracking. The laser welds were characterized in terms of the bead geometry, defects, microstructures, and hardness. With increasing joint gap, the percent porosity area increased, reaching just over 1% of the fusion zone area at a gap width of 0.6 mm for the 3.2 mm and 5.1 mm thick sheets. The maximum underfill depth in the Ti-6A1-4V laser welds was about 5% or 7% of the sheet thickness for the 3.2-mm and 5.2-mm thick materials, respectively, meeting the AWS D17-1 specification. The microindentation hardness was maximum in the fusion zone and sharply decreased through the heat affected zone until reaching the base metal value.

Jan 1, 2011

By R. C. Wallace

It was to be expected that the convening of the first Empire Mining Congress in June, 1924 in the city of London would turn men's thoughts very definitely to the question of exploring the mineral resources within the British Empire, the examining of her strength and her weakness in mineral material, and the consideration of steps that might advisedly be taken to strengthen her trade in minerals. That expectation was in part realized, though in the British way of presenting the case, and permitting the inferences to be drawn by implication. The opening address by the President of the Congress, to whom the Empire meant so much, gave a résumé of the contributions to the mining industry which were being made by the constituent parts of the Empire. The papers from the Institutes in Australasia, South Africa and Canada provided the details of resources and practice: while the individual contributions to the proceedings dealt with those phases of the mineral industry which are fundamental to the economic strength of British people, or to the health and well-being of the workers. While the subject matter thus presented was British mineral resources, and while the first consideration was the co-ordination and co-operation of British enterprise throughout the world, there emerged very clearly the wider viewpoint that the discussions had to do with a world industry, and with the contributions that that industry was making, and could further make, to the advancement of civilization irrespective of national boundaries, the world over. The invitations to representatives of the mining industry from the United States to participate in the Congress, and the warmth of approval which that participation evoked, were indications that such a congress cannot to-day be merely national in scope, and that trade in minerals, as in other natural resources, cannot be confined within national boundaries, but will seek its channels, unless artificial obstructions are too great, where the natural channels already exist.

Jan 1, 1925

By R. Al-Hent, M. Aissa, J. Asfahani

"This paper focuses on determining the favorable geological and hydrogeological conditions for forming uranium occurrences in the Froqlos-Jabal Abou Rabah region, Palmyrides, Syria. Eighty rock samples from this area were analyzed by spectrometric gamma-ray technique to determine the radioactive concentrations of eU and eTh, and of %K. Uranium concentrations in shallow and deep groundwaters were also determined. High uranium concentrations were registered owing to the presence of phosphatic outcrops in the study region. The uranium migration trends and its remobilization were analyzed through the analysis of the behavior of eU, eTh, and their ratio. A positive relationship between eU and eU/eTh, and a negative relationship between eTh and eU/eTh in geological formations of different ages supports the secondary remobilization of uranium. The role of groundwater movement in transportation and redeposition of uranium mineralization is discussed: deep waters are less oxidizing than near-surface waters, and do not appear to have significantly remobilized uranium. This indicates that the source of secondary uranium mineralization is surficial or near surficial, and is mainly related to the leaching of outcropping phosphatic layers.Integration of the results with established radioactive and geological sections reveals four radioactive anomalous zones: north Froqlos, Kherbet Hannora, northwestern flanks of Jabal Abou Rabah (Kherbet Al-Hajar), and the northwestern limit of the Ghuntor depression. The high uranium concentration in north Froqlos is because of its original presence in the phosphate beds and extensive fracturing, which allows groundwaters to penetrate and remobilize the uranium. High uranium concentrations in the other three locations are caused by the presence of evaporites and capillary action, which draws solutions upwards and causes redeposition as surface crusts (gypcrete)."

Jan 1, 2009

By Christoph Broeckmann, Andrew Gardula

"The adoption of high-pressure grinding throughout the cement industry has yielded enormous savings in energy and wear material costs. There are also a number of installations, which are applied in iron ore and kimberlite processing operations. High pressure grinding offers the same potential for energy and media savings, as well as opportunities for improved, downstream metallurgical performance, in hard rock mineral processing. This paper focuses on developments in machine design and wear surface engineering for high-pressure grinding of the hard rock ores in the mineral processing industry.INTRODUCTIONIn the early eighties 3.4 % of the world electric energy was consumed for crushing and grinding operations of minerals and 0.6 % in the ore dressing industry. During that time using a laboratory press Prof. Schönert found that interparticle comminution at high pressure requires remarkably less energy as conventional grinding technologies. In grinding of cement clinker he expected energy savings between 33 and 50 % compared to ball mills [1]. Piston presses are limited in throughput. Thus, the principle of interparticle comminution was adapted by the use of high pressure grinding rolls (HPGR) to a continuous plant process. Figure 1 shows the main components of a roller press: The roller nip of width s is formed between the floating roller (1) and the fixed roller (2). The diameter of the rolls will be denoted with D, the width with B. The total press force F can be adjusted using a hydraulic system with two or four pistons (3). In order to compare machines with different roll geometries the specific pressing force p is introduced:"

Jan 1, 2005

By L. R. Plitt, A. J. Neale, B. C. Flintoff

"INTRODUCTIONThis is not a technical paper in the normal sense. It is an informal document which is intended to share the results of some recent cyclone research with our colleagues both in operations and in research.PILOT PLANT FACILITIESFigure 1 is a schematic of the closed circuit hydrocyclone pilot plant testing facility at the University of Alberta. In this figure the system is configured for some experimental work on wide angle cyclones which was recently completed. The rig is designed to study cyclones in the approximate range of 10 cm to 20 cm diameter. Notable features include the variable speed feed pump, the magnetic flowmeter and pressure sensors on the cyclone feed line and the travelling launder which permits simultaneous sampling of both product streams.ORGANIZATIONFor organizational convenience the subject matter has been divided into three parts:(1) Peculiar Partition Curves(2) Wide Angle Cyclones(3) Rope DischargePECULIAR PARTITION CURVESMuch of the initial empirical mathematical modelling work on cyclone classifiers dealt with homogeneous ores. A homogeneous ore is one in which all particles have substantially the same apparent density, or where one phase is very clearly predominant. In contrast, a heterogeneous ore is one in which there are at least two different density classes, each making a significant contribution to the ore composition. (Particle shape similarity is always assumed.)One of the problems which can arise when analysing the overall solids partition (selectivity, Tromp, etc ... ) curve for a heterogeneous ore is the peculiar shape which may be observed, when compared to partition curves for homogeneous ores. This is not an unusual occurrence and it has been documented by Lynch and Rao, Finch and Laplante and Larsen and Spring. The purpose of this section is to identify those operating conditions which may give rise to peculiar partition curves."

Jan 1, 1986

By L. M. Lowe, D. G. Feasby, J. R. Goode

"Rare earth resources usually contain minor amounts of radioactive elements. The most widely recognised sources of radioactivity are associated with thorium and uranium. However, also present in the resources are isotopes of rare earth elements (REE) that are themselves radioactive, including lanthanum (La-138), lutetium (Lu-176) and samarium (Sm-147). These radioisotopes, as well as remnants of the natural thorium (Th-232) and uranium (U-238, U-235) decay series, can contribute to significant levels of radioactivity in mixed REE concentrates and in separated products. Levels such as these can present challenges for transport, transboundary movement, product storage, workers’ health and safety, as well as waste management issues at the facilities that separate out the individual REE’s. These are discussed in this paper. A particularly challenging radioactive isotope is Ac-227 (a decay product in the U-235 decay series). Actinium behaves chemically similar to lanthanides and hence normally concentrates with REE multi-element composites. Reliable analysis of Ac-227 is not widely available and the methodology required to deal with this challenge is briefly described. A principle reason for minimization of radioactive content throughout REE processing is restrictive specifications by concentrate purchasers in order to reduce waste management challenges. Approaches to the minimization of radioisotope content in REE concentrates and separated products are outlined in this paper."

Jan 1, 2014

By Mostafa Benzaazoua

Les remblais en pâte cimentés sont de plus en plus utilisés dans les exploitations minières souterraines. Une autre alternative d?utilisation du remblai en pâte consiste à le pomper et à le stocker dans des empilements de surface. En plus d?avoir des avantages d?un point de vue de stabilité physique des ouvrages, le remblai en pâte cimenté en surface permettrait également de stabiliser les contaminants dans la matrice du remblai à l?aide du processus de solidification et de stabilisation. Dans cette étude, des remblais en pâte constitués d?un résidu minier sulfuré renfermant beaucoup d?arsenic et de différents liants ont été testés afin d?évaluer la stabilisation des contaminants dans la matrice de remblai. La méthode utilisée pour évaluer la stabilisation et la solidification des contaminants est le test de lixiviation en extracteur de Soxhlet. Les résultats géochimiques issus de ces essais ainsi que la caractérisation chimico-minéralogique des remblais lixiviés ont été analysés pour comprendre les phénomènes chimiques présents dans les remblais durant le temps de cure. Les résultats obtenus montrent que les sulfures présents dans les remblais étudiés (pyrite FeS2 et arsénopyrite FeAsS) s?oxydent et provoquent la dissolution des hydrates les plus vulnérables (dissolution de la portlandite Ca(OH)2 et/ou décalcification des gels CSH). Le calcium produit permet de précipiter les sulfates (essentiellement sous forme de gypse plus ou moins hydraté) et l?arsenic sous forme d?arséniates de calcium plus stables. Les différents liants utilisés donnent des résultats différents en termes de stabilisation et de solidification qui seront discutés dans cet article.

Nov 1, 2002