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By M. Cai

"It is well known that Peak Particle Velocity (PPV) plays a critical role in triggering rockburst damage in burst-prone underground mines. To estimate the PPV distribution around excavations, advanced numerical modeling can be used. In wave propagation numerical modeling, velocity field is often assumed to be uniform around an excavation. However, it is observed that wave velocities near mine openings are not constant, but rather non-uniform. Wave velocity in a rock mass depends on many factors such as rock quality and confinement. In particular, confinement has a large influence on wave velocity. The confinement around an excavation is low at the wall boundary and increases gradually and reaches a constant value far away from the excavation boundary. Hence, stress redistribution due to excavation will have a profound influence on wave propagation in underground mines. A better understanding of the influence of excavation effect on wave propagation helps to interpret the field observation of rockburst damage and improve mine safety. For this purpose, a non-uniform velocity model need to be constructed and the influence excavation effect should be taken into account in numerical wave propagation modeling.In the present study, a non-linear velocity model is developed firstly by considering the influence of confinement on wave velocity. This model links wave velocity to confinement explicitly. A coupled numerical method is then developed and used to study the seismic wave pattern around excavations in underground mines. Two codes, FLAC and SPECFEM2D, are coupled in the analysis. The motivation of developing the FLAC/SPECFEM2D coupled approach is to take merit of each code, such as the stress analysis capability in FLAC and the powerful wave propagation analysis capability in SPECFEM2D. The coupling process is realized through three steps: (1) static stress redistribution around an excavation is analyzed in FLAC; (2) data for coupling analysis, such as non-uniform velocity field (based on the new developed velocity model), mesh, absorbing boundaries, etc., are generated by FISH functions in FLAC and passed to SPECFEM2D; and (3) wave propagation modeling is performed in the SPECFEM2D considering a fault-slip seismic source. Because stress redistribution around the excavation is considered, non-uniform velocity field for the SPECFEM2D model can be obtained and this is a notable feature of this study. Very large difference in the S-wave response in these two modeling approaches with uniform and non-uniform velocity fields can be seen from the modeling results.Using the FLAC/SPECFEM2D coupled modeling approach, accurate velocity models can be constructed and this in turn will help to produce accurate PPV distribution around the excavations. Accurate PPV contours can be used to identify high rockburst risk zones for improved dynamic ground support strategy."

Jan 1, 2015

By James Kear, Romain Prioul, Robert G. Jeffrey, Andrew P. Bunger, Dimitry Chuprakov

"Unconventional gas and geothermal reservoirs are typically naturally fractured and therefore the challenging problem of hydraulic fracture (HF) growth through naturally fractured rocks is an important issue especially for the development of accurate predictive HF models. This paper presents results from laboratory experiments in which HFs have been created in both sandstone and crystalline (gabbronorite) rock specimens such that they impinge either orthogonally or at an oblique angle on an unbonded, machined frictional interface. Depending on the conditions of each experiment, the fractures either cross or are blunted at the interface. The growth behavior was ascertained for these experiments based on a synthesis of the injection pressure record, active ultrasound monitoring, and direct post-experiment inspection of fractured specimens. From these experiments we observe: 1) A contrast between direct crossing and crossing with an offset for orthogonal and oblique intersection, respectively, 2) Apparent independence of crossing/blunting behavior on the friction coefficient for orthogonal intersection, 3) Dependence of the stresses required to promote crossing on the intersection angle between the HF and NF, 4) Existence of cases in which the hydraulic fracture crosses but then essentially ceases propagation such that all fluid is diverted to the interface. INTRODUCTIONHydraulic fracturing is a vital technology used to increase the productivity of oil, gas, and geothermal wells. Predicting hydraulic fracture (HF) growth is, in turn, critical to design of hydraulic fractures that grow to the desired length, accept the desired amount of proppant, and remain contained in the reservoir without unwanted height growth into surrounding layers (e.g. Economides and Nolte, 2000). The importance of HF modeling has prompted 6 decades of research during which simulators have become more efficient, more accurate, and have addressed a growing range of complexities (see review of e.g. Adachi et al., 2007).One of these complexities is the interaction between HFs and mechanical discontinuities such as natural fractures (NFs). Efforts in this area have been mainly driven by development of unconventional (i.e. low permeability) oil and gas resources because essentially all viable low permeability reservoirs, including shale gas/oil reservoirs, are naturally fractured to some degree (King, 2010). One of the most important questions for developing effective HF stimulation strategies in these reservoirs is whether the hydraulic fracture(s) is/are expected to be single-stranded or whether interaction with the NFs will lead to network-like growth. The basic building block for numerical simulators that can address this question (such as Kresse et al., 2013 and Weng et al., 2014) is whether an HF that intersects an NF will cross the NF or whether its growth will be captured by the NF so that additional fluid injection pressurizes the NF but does not generate ongoing growth of a new HF. These scenarios, including subcategories such as crossing with an offset, have been recognized for several decades (Daneshy, 1974; Warpinski and Teufel, 1987, and as recently reviewed and expanded by Chuprakov et al., 2013)."

Jan 1, 2015

By P. Groleau, O. Tavchandjian, D. Marcotte

In open pit mining, each small mining unit (SMU) is selected for mill processing based on an estimate of its true grade. The estimation is usually done using analyses of cuttings from blast holes within that SMU. One common estimator used for selection is the arithmetic average of within-SMU samples. This estimator is conditionally biased. The effect of a conditional bias is to overestimate the profit really recovered from the deposit. For this reason, a conditionally unbiased estimator is preferable. Increasing the number of samples generally improves the accuracy of the estimation (and diminishes the conditional bias, if present, of most estimators). However, there exists a practical limit where an additional sample does not improve the estimation sufficiently to cover the expense of making the analysis. This limit is specific to each deposit and depends on geostatistical parameters, economic factors, and mining parameters. This study examines how the number of samples affects the recovered reserves and the resulting profit. Also, the effects on optimal profit of varying the different factors are examined. Globally, the number of samples required increases with the selectivity of the operation. For a given ore deposit, the greater the number of SMUs selected for processing, the fewer samples are required and vice-versa.

Jan 1, 1998

By J. M. Rios

Without conscious effort and understanding, a number of factors peculiar to mineral exploration campaigns conspire against building sustainability in host communities. These include the episodic and transitory presence of an exploration team in the community and the inherent uncertainty of outcomes; most projects fail. Given these circumstances, there is a strong tendency to apply a simple formula of providing employment, pragmatic philanthropy and supporting infrastructure improvements (roads, schools and clinics) to demonstrate that mining provides benefits. Experience in rural native communities of Mesoamerica has shown that it is possible to create positive, sustainable outcomes quite rapidly within communities, which build capacity, improve quality of life and support a strong social license to operate. Success comes from an understanding of community structure and dynamics; engaging with all segments of the community; creating healthy, transparent and accountable relationships based on clearly defined roles and responsibilities; and supporting and strengthening the role of women in a culturally appropriate way. To this are added innovative and culturally appropriate ways of incorporating sustainability through genuine social investment in areas more typically addressed by exploration companies; health, education, and environmental management.

Aug 1, 2013

By V. J. Southey

HOLLINGER mining operations have required development by 24 vertical shafts having a total length of 28,160 feet. Seventeen of these are sunk from surface and seven are interior shafts. Four surface shafts and three interior shafts are now active and, excepting the recently completed new main ore-hoisting shaft, the remainder are either abandoned, or are used for passes or for ventilation. The new shaft bottoms 60 feet below the 3,050 level, but there is much work to be done before it is placed in service. The term 'shaft practice' is intended to include shaft construction and a general treatment o typical equipment. It is a large subject for an organization the size of Hollinger and this paper is intended only to present the salient features. The writer wishes to thank the management for permission to publish this information and to acknowledge the advice and criticism o A. G. Irving, chief engineer, and the willing co-operation of other members of the Hollinger staff.

Jan 1, 1939

By B. Hewitt

Murrin Murrin Operations has not had a successful beginning. Numerous reliability and operability issues many of which are the result of design decisions have been addressed through mechanical and operational changes and the CCD circuit is no exception. The decision to install, the installation and the results of the CCD1 rake-lift mechanism and feedw ell dilution system are discussed in this paper. The installation was justified on improved operational robustness and an increase in the in the underflow density of 1% (per cent w/w). At approximately the same time process modifications in the solution neutralisation circuit were implemented and these changes altered the rheology of the slurry reporting to CCD1. Since the modifications to CCD1 and the solution neutralisation circuit, the CCD circuit has averaged a 2% improvement in the circuit underflow density. The CCD1 modification was completed on time and mechanically has performed well. From a risk point of view, the central rake-lift and Turbodil® dilution system add a degree of freedom and robustness to CCD1 operation that has extended the range of operational confidence. In this respect, the modification has been a success and is complementary to solution neutralisation improvements.

Jan 1, 2004

By G. A. Sutton

"At the San Manuel mine (Arizona, USA), in-situ copper leaching of a copper porphyry deposit was carried out from 1986 to 1999 during underground and open-pit mining. In 1993–1994, well¬field testing of the supergene zone, composed primarily of chrysocolla and copper-rich clay minerals, led to estimates that 52% of the acid-soluble copper (ASCu) could be recovered during in-situ leaching; however, the actual recovery from zone 6, which had the longest leach history, was approximately 42%. Comparing drillcore assay data from holes drilled before and after leaching also indicated an approximate recovery of 42%. The discrepancy between the predicted (52%) and actual (42%) recovery is probably related to several factors, including difficulty maintaining fluid saturation, channelling effects, and gypsum precipitation. ¦ KEYWORDS Copper oxides, in-situ leaching, Modelling, Porphyry, Solvent extraction and electrowinning (SXEW), Well-to-well RÉSUMÉ À la mine San Manuel (Arizona, États-Unis), on a procédé de 1986 à 1999 à la lixiviation in-situ de cuivre d’un gisement porphyre cuprifère pendant l’exploitation minière souterraine et à ciel ouvert. En 1993 et 1994, des essais effectués dans des champs de captage de la zone supergène, composée principalement de chrysocolle et de minéraux argileux cuprifères, ont abouti à des estimations selon lesquelles on peut récupérer 52 % de cuivre soluble dans l’acide (ASCu) pendant la lixiviation in-situ ; toutefois, la récupération réelle dans la zone 6, qui affiche l’histoire la plus ancienne en matière de lixiviation, était d’environ 42 %. La comparaison des données d’analyses de forage obtenues à partir de trous forés avant et après la lixiviation indiquait également une récupération approximative de 42 %. La différence entre la récupération prévue (52 %) et réelle (42 %) réside probablement dans plusieurs facteurs, notamment la difficulté à maintenir la saturation des fluides, les effets de canalisation et la précipitation du gypse. ¦ MOTS CLÉS d’un puits à l’autre, extraction par solvant et extraction électrolytique (SXEW), lixiviation in-situ, modélisation, oxydes de cuivre, porphyreINTRODUCTION in-situ copper leaching at the San Manuel mine, Arizona, USA (Figure 1), began in 1986. It was recognized that some of the copper oxide resource was not economically recoverable by conventional open-pit and heap leach methods using solvent extraction and electrowinning (SXEW) and a high stripping ratio would be required to access part of the resource. At the time, in-situ leaching was becoming popular in the uranium industry, but the approach was virtually unknown in the copper industry, especially at a large scale."

Jan 1, 2019

By J. M. Cummings

CONSIPERABLE information on the industrial or non-metallic mineral resources of British Columbia has been published. For a general resume of the subject, reference may be made to a paper presented by A. M. Richmond before the Annual General Meeting of the Institute in 1935 (1). To avoid duplication, the present paper is confined to a discussion of the existing industrial mineral industry of the Province and of the factors governing its present and future development. British Columbia's mineral production in 1936 had a value approximately 15 per cent of that for the whole of Canada. Preliminary estimates for 1937 indicate that this proportion has been maintained, although the totals have increased about 25 per cent. The following table presents comparative figures, for the year 1936, illustrating the relative importance of the major divisions of the mineral industry in British Columbia and in Canada as a whole.

Jan 1, 1938

By A. Ingelson

Conflict over mineral development and its impacts on indigenous peoples occurs in many countries around the world. Canada, Bolivia and Peru have experienced mine development for centuries in areas where indigenous communities have been and continue to be affected by the mining industry. On a global basis the mining industry continues to face the challenge of implementing meaningful consultation programs with indigenous peoples. Many governments around the world have adopted sustainable development as a policy and one important element of sustainable development is minimizing social conflict. John Moffet and Francois Bregha (Moffet & Bregha, 1996), in their analysis of the role of law reform in promoting sustainable development, noted that stakeholder participation can reduce this type of conflict. Social conflict can result in expensive litigation and costly project delays for mine developers. Meaningful consultation with indigenous peoples in areas where mine development is proposed can be a critical factor in securing a social licence to operate. A report released by the United Nations in 2005, outlined the elements of a concept called ?free, prior informed consent? (FPIC) that promotes more sustainable development. FPIC provides that mineral exploration and mining should not proceed unless the mining company has secured the consent of the relevant indigenous group(s). This paper employs a comparative approach to evaluate the extent to which three active mining nations, Canada, Bolivia and Peru, require consultation with indigenous residents and adhere to the principle of FPIC. The comparative approach assists in the identification of those consultation elements in the legal regimes of each country that can minimize social conflict in mineral exploration and mine development and therefore contribute to more sustainable development. First, we examine the legal requirements to consult with and accommodate indigenous communities in Canada, a country with a long history of mineral development over a large geographic area that has entrenched in its Constitution the protection of indigenous peoples? rights. We then turn to an analysis of Bolivia, one of the most indigenously conscious mining jurisdictions that has followed the Canadian lead in entrenching constitutional protection for indigenous peoples. Third, the approach to consultation with indigenous peoples in Peru, a nation that has not adopted the Canadian and Bolivian approaches to constitutional protection of indigenous peoples rights, is considered.

Aug 1, 2013

By George E. Cole

Introduction In view of the fact that, during the past year, two Manitoba mines-Flin Fion and Sherritt Gordon-have entered the list of producers and have materially increased that Province's contribution to the metal production of the Dominion, it would seem appropriate at this time to review the progress of the industry in the Province, with particular reference to the out-standing metal-mining developments of the past decade. That these two mines have been able to continue their operations in spite of the low prices of copper and zinc adds a touch of brightness to the industrial life of the Province. Depression in metal prices is not encouraging to the mining industry, but it does stimulate efficiency in methods and costs of production. As two thriving towns have grown around the two mines, the will of the management to carry-on is of great consequence to Manitoba, this year so hard hit by the .agricultural depression. And, much as it is a pleasant feature in the mining situation that these mines have been able to continue operations, nevertheless it must be noted, in reviewing the mining developments of the past few years in Manitoba, that the Province was fortunate enough to profit by good times, in that an industry was established which gives evidence of permanency. In the metallic field, the section of Manitoba that first received attention from prospectors was the boundary district, west of the Lake of the Woods. Several claims were staked here at the time of the gold boom in the neighbouring Ontario area. But the first real interest in metalliferous deposits dates from the discovery of gold in March, 1911, in quartz veins on the shores of Rice lake, some twenty miles east of lake Winnipeg. Systematic and organized prospecting of the pre-Cambrian areas of the Province may be said to have commenced with that discovery. The first gold discovery in northern Manitoba was made at Wekusko (Herb) lake in 1914. This was followed by the discovery of the Flin Flan and Mandy copper ore-bodies in 1915 on Flin Fion and Schist lakes, respectively.

Jan 1, 1932

By H. O. Seigel, J. C. Gingerich, E. O. Köstlin

"To satisfy their continuing need to replenish or expand their ore reserves, mining companies are faced with the dilemma of arriving at a proper balance between the dual avenues of discovery through in-house exploration and of acquisition of properties that are relatively proven or are even in production. The returns from exploration activities may be spectacular, but are unpredictable. The allure of an acquisition lies in its promise of quick and risk-reduced addition to reserves. However, it is historically clear that quantum increments in shareholders’ values have arisen primarily through major exploration discoveries, rather than through major late-stage acquisitions. Late-stage acquisitions can prove highly profitable, sometimes based upon the planned use of superior mining or metallurgical technology, but more often occur as the result of unexpected windfalls. At the other extreme, they can become expensive failures through inadequate due diligence, or unforeseeable factors.Citing numerous case histories and industry statistics, it is concluded that a judicious combination of both exploration activity and the acquisition of prospects is the most advantageous strategy for adding new ore reserves. A skilled exploration staff is essential for success, be it through exploration discoveries or through opportunistic acquisitions, preferably at their early stages. In the future, it is anticipated that there will be fewer opportunities for acquisition because of reduced funding for junior exploration companies, leading to increased competition and higher costs for fewer properties, both in the advanced exploration and mining stages."

Jan 1, 2002

By A. A. Wessels, D. P. Allison

"Mine hoists are built to handle a certain nameplate capacity; they are specified and designed according to the required duty. However, as production capacity increases in other parts of an operation, the hoist capacity can become the critical constraint. Such a situation occurred at Lundin Mining’s Neves-Corvo operation. This paper examines how each component of the existing hoisting system was examined and optimized. Through a combination of engineering study and hoist simulations, the annual hoisting capacity was improved by 24% through increases in payload capacity and available hoisting time combined with a reduction in cycle time, while no changes were made to the hoist motor, drum or headframe. The additional payload capacity was achieved by reducing the mass of the hoist ropes and skips, and improving load monitoring systems. The cycle time was reduced through the shortening of the creep distances and increased availability through the installation of a shaft collar safety platform, alternative guide rope bushes, and superior liners for both the skips and underground measuring flasks. Enhanced cooling of the hoist electrical system was also incorporated to increase hoist availability by reducing downtime during hot summer months. The changes will increase the capacity from the current 4.5 mega tonnes per annum (Mtpa) to a planned 5.6 Mtpa and are being implemented over a 2-year period whilst maintaining the mine production during the upgrade work. INTRODUCTION Neves-Corvo Mine Neves-Corvo is primarily a copper and zinc mine producing copper, zinc and lead concentrates. The operation is owned and operated by Somincor, the Portuguese subsidiary of Lundin Mining. Located in the Alentejo district of southern Portugal, the operation is situated approximately 15 km southeast of the town of Castro Verde, where summer temperatures can reach as high as 45ºC, and approximately 220 km southeast of Lisbon. The principal means of mine access is via a ramp from surface, with the vertical shaft used to hoist ore and waste from the 700 m level, while conveyors descend from the 700 m level to transport ore and waste up from the deeper levels of the mine. The mine is highly mechanized and several different stoping methods are employed, with the most significant being bench-and-fill and drift-and-fill. The Neves-Corvo mine currently exploits five orebodies: Neves, Corvo, Graça, Zambujal and Lombador for copper and zinc-lead ores which are processed in one of two plants. All the orebodies are currently exploited over their full elevation with the exception of Lombador which is only mined down to the 220 m level, approximately the top 50% of the orebody, known as Lombador Phase 1."

Jan 1, 2019

By C. M. Campbell

The Inconceivable Wealth propaganda goes on apace. Premier King, at Vancouver, has stated that we still have, untouched, natural resources, "beyond the wildest dreams." Principal Currie, in an address before the Canadian Society in New York said that Canada's resources, "are as yet merely scratched and it is not possible to compute her almost fabulous natural wealth." Mr. Meighen, in the last election campaign announced that, "under the providence of God, Canada is more richly endowed, perhaps, than any other country in the world." Four years ago a despatch was sent to Premier King "on behalf of" this Institute advising him that "Inconceivable Wealth" in minerals in this country was assured. This was made as a statement ~f "incontrovertible fact." Specifically, this despatch stated that this wealth was on such a scale that the mining industry would in the future lead all others in this country. This inventory is still in effect as far as this Institute is concerned.

Jan 1, 1926

By D. Moronkeji, R. Maharidge, D. A. Curry, B. J. Davis, U. Prasad, J. Franquet

"Proper shale characterization is crucial in shale gas drilling, exploration, completion and production. Unlike porous sandstone and carbonate reservoirs, the challenge with shales comes from their micro- to nano-darcy permeability ranges and the anisotropy of their mechanical and hydraulic properties. Most porosity-dependent logs are not sensitive enough to capture the true behavior of shales. Consequently, mineralogy and other strength and stiffness-related properties must be determined to characterize magnitudes and variances in shale mechanical and flow properties. In addition, these properties must pass quality assurance/quality control (QA/QC) practices to give confidence in their use in subsequent log calibrations, during geomechanical modeling, or in fracture design models. This paper presents a technique to integrate shale properties that are measured by various methods, and a methodology to perform QA/QC on the data before application.Shale properties originate from various sources, including downhole and laboratory measurements. Physical samples for laboratory testing are usually limited to a few depths. Lab tests are often costly, and replicating in-situ conditions can be difficult or impossible. In addition, results frequently show wide scatter, reflecting inherent depth variability and lateral heterogeneity. Wireline logs provide nearcontinuous data, but rarely yield direct measurements of rock strength properties. Although geomechanical and fracture models use log data, calibrating it with reliable and previously verified lab-measured properties is important. This paper presents a process to perform QA/QC on lab-measured data using various crossplots.Ten mechanical, microstructural and physical properties are graphically displayed to visually characterize shale strength behavior in ambient and in-situ conditions, whether measured or modeled statically or dynamically. These properties are often sourced from different departments. The properties are integrated but are individually subject to the previously mentioned uncertainties. Pairs of property values are crossplotted and compared with correlations from the literature or previously established with qualified data from related formations. Conformance with these correlations gives confidence in the data, whereas outliers are flagged as questionable. Repeating the process with questionable data crossplotted against other parameters for the same depth highlights the property with the greatest uncertainty. The determination of its value is investigated to locate the source of the inconsistency and establish a more reliable value. Where this is not possible, the user has a rational basis for rejecting that property value."

Jan 1, 2015

By F. R. Jones, B. W. Taylor, A. R. MacPherson, L. J. Lamb

"The Lake St. Joseph Iron Deposit is in Northwestern Ontario. Exploration to date by Steep Rock Iron Mines Limited has indicated an ore reserve of 683 million long tons. Metallurgical investigations have proved that suitable oxide pellets and/or superconcentrates can be economically produced from this ore. Studies of the Lake St. Joseph iron ore deposits have covered the period 1956-71, and have embodied applications of the improvement in mining and processing technology over this period. Market demand in the early 1960's for high-grade oxide pellets as a replacement for natural iron ores for the blast furnace first drew attention to the potential of the Lake St. Joseph deposit. The current market trend toward utilization of sponge iron to replace steel scrap as feed to electric furnaces and cupolas now suggests that the deposit can better be exploited as a prime source of superconcentrates."

Jan 1, 1972

By J. S. Fox

Major-element data for unaltered, unmineralized felsic host rocks from a number of stratigraphically simple, massive volcanogenic Zn-Cu(-Pb) sulphide deposits of low metamorphic grade have been compiled. The petrochemical affinities of these host rocks have been determined (by standard means and by discriminant analysis) and compared. This comparison indicates that volcanogenic deposits in felsic terrains are not restricted to the classical calc-alkaline rock association as previously thought, but can actually be hosted by rocks showing a range of iron content. There is a positive correlation between differentiation trend and are tenor. Zn-Cu ores usually have iron-rich felsic hosts (most Canadian Shield deposits); Pb-Zn -Cu ores have iron-poor felsic hosts (Japanese, Iberian and Tasmanian deposits). This parallels the antipathetic relationship between iron content and background lead levels evident in young, unmineralized, island arcs as well as in many older belts. Correlations between differentiation trend on one hand and massive ore mineralogy and the relative proportions of various rock type (including rhyolite, quartz-porphyry and coarse pyroclastic rocks) on the other are also evident. It is concluded that the recognition of a calc-alkaline differentiation trend cannot be used as a prospecting guide, as has previously been proposed. However, in view of the above correlations, the recognition of a given trend may aid in the formulation of an effective exploration philosophy.

Jan 1, 1979

By N. C. Carter, Wm. H. White, J. E. Harakal

"Of twenty-one ore deposits in British Columbia which are either in production or advanced stages of exploration, five have potassium-argon ages in a range of 165-205 m.y., eight are in a range of 44-55 m.y. and the remainder are either ca. 140 m.y. or ca. 100 m.y. old. Deposits of the oldest group have generally similar geological environments and radiometrically indistinguishable ages of magmatic and hydrothermal minerals. Deposits of the youngest group also have similar geological environments, with successive magmatic and hydrothermal events closely intermingled in time and place. Such deposits find no comfortable home in existing classifications of ore deposits. 1t is suggested, therefore, that those epigenetic deposits which can be shown by radiometrie and/or geologie means to be coeval with genetically related magmatism be designated as ""paramagmatic deposits."""

Jan 1, 1968

By R. Hans

Removal of toxic anions from aqueous solution was studied using a Magnetic Ion Exchange (MIEX) resin which is a polyacrylic, strong base resin. Gravity based settling is made more efficient due to the magnetic nature of the resin which is advantageous over conventional ion exchange resins. In addition, the magnetic microspheres of MIEX have larger surface area in comparison to conventional ion exchange resins. Over the years MIEX has been successfully used and has gained significant popularity for efficiently removing dissolved organic matter from wastewater and groundwater. In the present study the efficiency of the MIEX resin was tested for the removal of chromium(VI), molybdenium(VI), vanadium(V) and arsenic(V) anions. Effects of pH (2-10) and temperature (25oC-55oC) were examined. In general, low solution pH values were favorable for anion uptake by MIEX. Except for chromium(VI), the metal ion uptake was significantly increased by the increase in solution temperature. The adsorption data were analysed on the basis of chemical speciation and heterogeneous kinetic models.

Jan 1, 2014

By Kevin P. Plucknett, Z. Memarrashidi

"In the current work, factors influencing the corrosion mechanisms of TiC and Ti(C,N) based cermets are reviewed. Cermets were typically prepared with 30 vol.% of metal binder, in the form of various in-situ reaction-formed Ni3Al alloys. Commercial WC-Co hardmetals were also examined as baseline materials. The assessment of corrosion involved a variety of electrochemical measurements, including open circuit potential and potentiodynamic polarisation. The corrosion potential and current density were determined, following Tafel extrapolation, allowing estimation of the corrosion rates. Post-corrosion characterisation involved scanning electron microscopy analysis and associated energy dispersive X-ray spectroscopy of the sample surfaces. It is demonstrated that the primary corrosion mechanism for this type of cermet is dissolution of the metallic phase during oxidation attack, and thus this response can be expected to increase with the amount of binder in the cermet, although degradation can be subtly affected by composition (i.e. alloy composition, C:N ratio, impurities in the ceramic phase, etc.) and test procedure (i.e. aerated vs. de-aerated electrolytes). It was observed that addition of N content into the ceramic phase is beneficial to the corrosion characteristics of TiC based cermets, through significant refinement in the grain size of the hard phase. Similarly, elimination of impurities, such as W in selected TiC powders, also improves the corrosion resistance.INTRODUCTION Cermets are prepared using the combination of a hard, high elastic modulus ceramic phase with a ductile, high toughness metallic binder. This pairing of hard and ductile components ensures wide application of cermets in demanding wear environments. These materials are consequently used industrially in both bulk and coating form. The most common example of such a composite system is based on the use of tungsten carbide with a cobalt-based binder (WC-Co), which has been widely examined over the past 80 years. However, while WC-Co has been shown to exhibit an excellent combination of high strength and wear resistance, the corrosion and high temperature properties of this material are relatively poor. In addition, WC-Co possesses a high density (~13–14 g/cm3), which makes it a less desirable option when the component mass is a design factor (i.e. use in aerospace). In particular, the aqueous corrosion response of WC-Co limits its use in wear environments where combined corrosive degradation may occur (i.e. tribo-corrosion scenarios). Alternate cermet systems are therefore being actively developed due to these performance limitations."

Jan 1, 2017

By F. Baczek, S. S. Rocks, D. Chaiko, C. Eyzaguirre, S. Asihene, T. Walters

The majority of efforts to improve primary copper sulfide leaching have focused on solution chemistry, temperature, O2 pressure, ultra-fine grinding, the use of catalysts, etc. Historically, very few studies have focused on the solid/solution interface. A new, patent pending approach to catalyzed, copper sulfide leaching has been discovered by FLSmidth that enables manipulation of the 2-D semi-conductor properties of chalcopyrite surfaces to the benefit of higher electrochemical reactivity. Copper dissolution rates are then further accelerated by incorporating a Stirred Media Reactor (SMRt) into the process. By using minute amounts of Cu2+ to "pre-activate" chalcopyrite, leach times have been reduced from >20 hours with incomplete Cu dissolution to <2 hours with 98+% Cu dissolution at 80°C. The pre-activation process takes only minutes to complete at temperatures of 80°C or less. The total atmospheric leaching process, incorporating the pre-activation and Stirred Media Reactor is compatible with existing SX/EW processes. Results of batch leach testing are presented and possible mechanisms are discussed.

Jan 1, 2015