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By D. A. Rhys, M. Sieb, M. A. Prefontaine, C. L. Swanson, S. R. Frostad, H. Q. Smit

"Gold-silver mineralization at Red Mountain (1992 resource of 2.5 million tonnes grading 12.8 g/t Au and 38.1 g/t Ag) occurs within several discrete zones within a folded sequence of Middle to Late Triassic Triassic sedimentary rocks, Early Jurassic volcaniclastic and pyroclastic rocks, and Early Jurassic intrusions. Three phases of Early Jurassic sills and stocks collectively comprise the Golds/ide intrusions: (1) irregular bodies of medium-grained hornblende monzodiorite (Hillside porphyry); (2) hornblende-biotite + quartz porphyritic monzodiorite to quartz monzodiorite (Golds/ide porphyry; U-Pb zircon ages of 197.1 + 1.9 Ma); and (3) biotite porphyritic hornblende monzodiorite sills (Biotite porphyry). Contact breccias and igneous breccia dikes are common features of the Golds/ide intrusions. Chemical similarities and equivalent ages of volcanic rocks and intrusions, and the presence of intrusive clasts in volcanic rocks suggest that the intrusions are feeders to overlying volcanic units.Hydrothermal alteration affects all pre-Tertiary rocks on Red Mountain, including all phases of the Golds/ide intrusions. Several shallow-dipping alteration zones are developed sequentially above a propylitic quartz stockwork/molybdenum zone. These include: (1) sericite-quartz-pyrite alteration (pyrite-dominant alteration); (2) chlorite-K-feldspar-sericite-titanite alteration with disseminated and vein pyrrhotite (pyrrhotite-dominant alteration); and (3) brown to black tourmaline veins and K-feldspar-pyrite-titanite-actinolite alteration. Anomalous gold(> 0.3 g/t) mineralization is developed at the transition from the pyrite to the pyrrhotite dominant alteration over a > 1 km2 area. Within this anomalous zone, high-grade (3 g/t to 20 g/t Au) gold-silver mineralization occurs in 5 m to 29 m thick, semi-tabular pyrite + pyrrhotite stockworks with intense sericitic alteration and surrounding disseminated sphalerite + pyrrhotite.Stratigraphic, spatial and geochronologic relations and alteration zoning indicate that mineralization formed in a subvolcanic environment at the top of the Golds/ide intrusions and at the base of the Early Jurassic volcanic pile. The Golds/ide porphyry is interpreted to be the mineralizing intrusion. The alteration zoning, molybdenum-copper mineralized quartz stockworks, extensive Ksilicate and tourmaline alteration, and the relationship with a hypabyssal porphyritic intrusion show similarities to many porphyry systems."

Jan 1, 1995

By L Avalos, F Melo Miranda, J Misle, M Ingwersen

"Los Pelambres, majority owned by the Chilean company Antofagasta Minerals, is one of the leading producers of copper and molybdenum in the country. It is located high in Andes Mountains, over 3000 metres above sea level, 316 km from the nation's capital, Santiago.The maintenance service supplied to Los Pelambres over the past 13 years has evolved to the point that FLSmidth now provides an integrated service crucial to the management of their customer's assets. The contract initially involved specialty mechanical, electrical and instrumentation maintenance and has developed to encompass maintenance planning and plant control systems.The integrated partnership has delivered excellent results in the areas of improved availability, reliability and return on investment. The operation is now amongst the industry leaders in plant availability.The integrated maintenance service has delivered: An increase in plant availability from 93%, in the first year, to 96.5% today, generating approximately $50 million additional income per year, Quality work procedures, Process and equipment improvements, Major shutdown planning involving more than 700 personnel, 6000 parts and over 2 000 discrete activities.The ongoing success of the partnership requires a high level of understanding between both companies. A commitment to maintain a long term sustainable relationship, based on a ""win - win"" culture, is the key to this success. In this regard Los Pelambres has been a pioneer in establishing and developing such relationships.This case study will share the lessons learnt, the measures taken to improve performance and the best practices adopted during the 13 year evolution of the maintenance service partnership.CITATION:Misle, J, Melo Miranda, F, Avalos, L and Ingwersen, M, 2013. Integrated maintenance services at the Los Pelambres Mine in Chile - The lessons learnt and best practices developed from a long-term sustainable relationship, in Proceedings MetPlant 2013 , pp 296-331 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 15, 2013

By Albert L. Brautigam, Michael R. Yenchek, Jeffrey Shawn Peterson, James C. Cawley

The National Institute for Occupational Safety and Health investigated how the starting of induction motors may cause nuisance tripping of short-circuit protection on coal mine power systems. This research had a dual purpose: 1) to identify how motor-start waveforms differ from those for short circuits and 2) to devise a method to provide short-circuit protection without intentional time delays to account for motor starts. This technology will help ensure that surface temperatures of energized electrical apparatus will not exceed gas or dust ignition thresholds when short circuits occur.

A reliable laboratory method to characterize the response of free gold particles to flash flotation conditions has been developed. The test has been performed on free milling gold ores as well as synthetic ores, using either a gravity concentrate or gold powder as the gold source, to assess the floatability of gold particles. Trends in free gold flotation kinetics, as well as size and milling effects, were identified for gold recovery based on the different feed types, reagent dosages, and residence times. It was shown that the ultimate recoveries and kinetic trends of gold particles from the gravity concentrate could be enhanced with increased dosage of collector, potassium amyl xanthate. Interestingly, in comparison to gravity-recoverable gold, recovery from pure Au powders was better in collectorless flotation, and cumulative recovery decreased with higher levels of collector addition. Improved coarse particle recovery appeared linked to increased collector additions for both the gravity concentrate and the pure gold powders. In general, coarse gold particles demonstrated slower kinetic rates thaen the fine or intermediate components incomparable tests.

Jan 1, 2015

By G W. Wilson, M Aubertin

A desulfurised tailings cover was installed at the Detour Lake Mine in Ontario, Canada, to reduce oxygen penetration into the underlying sulfidic tailings. The cover ranges from one to 1.5 m in thickness and was intended to maintain high water saturation to reduce oxygen diffusion and consume oxygen by oxidation of the residual sulfide minerals. The tailings impoundment was instrumented to measure climatic parameters, water levels and water content profiles within the tailings and single-layer cover. One year of monitoring data was collected. Additional tailings samples were obtained for geotechnical and geochemical characterisation. The average grain size of the cover material was found to be coarser than the underlying tailings. Monitoring also indicated that air entry values of the cover material were lower than the tailings. Numerical modelling was conducted on the cover to predict water content profiles under varying climate conditions together with the depth of oxygen penetration and diffusive oxygen fluxes. Estimates of the diffusion coefficient and kinetic oxidation rates from field data compared well with values obtained by laboratory measurements. Numerical simulations indicate water saturations of less than 85 per cent can be expected under varying climate conditions. Predicted oxygen flux rates through the desulfurised cover over tailings with high acid potential indicate low flux rates reaching these tailings due to either consumption of oxygen by residual sulfur within the cover or saturation of the underlying tailings.

Jan 1, 2003

Duty on Lead Reduced. -On December 28, the President signed H.R. 5047 which reduces the duty on unwrought lead from 3.5% ad valorem to 3% ad valorem, with a floor level of 1.0625 cents per pound, effective retroactively from January 1, 1980, through June 30, 1983. Pacific Northwest Power Bill Passed. -On December 5, the President signed S. 885 which will enable the Bonneville Power Administration to guarantee 20-year contracts to its 15 major industrial customers in exchange for higher rates. In effect, the bill will have industrial customers pay some of the costs of building additional generating facilities in the Northwest, of which thermal units are expected to be a major part. BPA supplies power to six primary aluminum producers which operate eleven plants having over 30% of the primary aluminum capacity in the United States.

Jan 1, 1980

By W. G. Park

Long-range projection of demand for domestic crude oil indicates a continued upward movement and accentuates the need for increasing the recovery from known crude-oil resources to supplement expected future discoveries. Consequently, the industry and Government have given special attention to the viscous or heavy-oil deposits because they offer the distinct possibility of large order increases in ultimate recovery. This report presents data pertaining to 150 heavy-oil reservoirs in Arkansas including oil characteristics of samples from 38 of these reservoirs. To January 1, 1967, about 600 million bbl of heavy oil has been recovered from the 150 reservoirs in 63 oilfields; however, about 4.5 billion bbl, or 88 pct, of oil remained in the ground. Of prime importance is that much of this heavy-oil resource is in reservoirs having characteristics considered favorable for thermal-recovery operations. Data for the thermal projects initiated [thus Ear are presented in individual field discussions. Also discussed is the t crude oil supply-demand situation in the State.

Jan 1, 1969

By L. Maday, V. J. Perrone, M. B. Gilbert

INTRODUCTION The Brightwater conveyance system project in King County, Washington consists of constructing about 21 km (13 mile) of effluent and combined influent and effluent tunnels. The influent tunnels will collect sanitary sewerage from the service area and convey it to the new wastewater treatment plant (WTP) site at Route 9 in Woodinville, Snohomish County, Washington. The effluent tunnels will convey treated effluent from the WTP to an outfall at Puget Sound. The tunnels will be constructed primarily under residential areas, busy suburban roads and state highways. This 21 Km (13-mile) soft ground tunneling project faced many design challenges because of the geologic and hydrostatic conditions, long tunnel reaches, and large overburden depths. Boring depths typically varied from 45.7 M (150 ft) to 114 M(375 ft) with a maximum depth of 185.6 M (566 ft) deep. Conventional empirical methods for non-mountain terrain based on a 1:1 ratio of drilled footage per foot of tunnel bore (National Research Council, 1984) for evenly spaced borings provided a good start for the Phase 1 explorations. However a continuation of this approach with closer spacing was deemed inadequate by the geotechnical team for efficiently allocating geotechnical exploration resources for the final design. This paper presents a rational approach that was used to evaluate the value of a particular geotechnical exploration boring, pump test or other in-situ test. The method of analysis, which was initially developed for rock tunnels (Einstein et al., 1978), was modified for the Brightwater project. The method considers the potential construction cost risks resulting from variable geologic conditions, the cost and reliability of the geotechnical exploration and the earned value (cost risk reduction) of performing the geotechnical exploration. PROJECT DESCRIPTION In total the land portion of the conveyance system will include approximately21 Km (13 miles) of tunnels ranging in size from 3.0 to 5.2 M (10 to 17 ft) minimum inside diameter with overburden depths of 30.0 to 168 M (100 to 550 ft) and

Jan 1, 2005

By Geoffrey D. Collins

This paper deals with the construction of the Effluent Outfall Diffusers which form part of the outfall for the Deer Island sewage project. The work was executed 15 km out to sea in Massachusetts Bay and required the drilling, installation, grouting and accurate determination of the actual position of 55 riser shafts in 33.5 m deep water. Although not strictly a "foundation", the contractor's approach to the installation of the diffusers was a logical development from many marine foundation projects executed by the Contracting companies over the last decades. The only previous application of this design of outfall had been in Australia where offshore oil drilling techniques had been adapted for use in riser installation.

Jan 1, 1994

By P. M. Ambrose, C. Travis Anderson, Cresap Moss, R. S. Dean

"MANGANESE METALMethods of PreparationMethods of preparing the manganese metal that has been used in chemical and metallurgical investigations have passed through a cycle. Most of the investigations made before the turn of the century used Moissan's pyrophoric manganese. 5/ This material was made by electrolysis into a mercury cathode and distillation in vacuo. It was essentially a pure material, and investigations in which it was employed (with proper precautions against oxida¬tion) led to accurate results concerning the intrinsic behavior of metallic manganese.An early investigation of the properties of ""Manganese-by-Mercury"" was made by M. Guntz. 6/ He prepared manganese by electrolysis of a concentrated MnCl2 solution with a mercury cathode. The manganese amalgam was pressed through chamois and distilled in vacuo (2 to 3 cm. of mercury) at 200°0., slowly rising to 250°0. Guntz recognized especially the decreased reactivity of manganese with increased temperature of mercury distillation. The most careful and com¬prehensive study of manganese made by this method is that of Kuh 7/ whose work unfortunately was never published in an accessible journal.Royce and Kahlenberg 8/ studied the electrode potential of manganese made by this method."

Nov 1, 1939

By Hibbert W. D, Lottrey A

The behaviour of coal in a process is a function of both the coal properties and the processing conditions. In the case of the Loy Yang coal deposit, extensive testing has been undertaken to determine: ò the extent, distribution and structure of the coal resource; ò the variations in properties throughout the resource; and ò evaluation of the behaviour of the coal during processing. This has involved the conduct of an extensive borehole drilling program, backed by geological modelling and material characterisation (chemical, physico-chemical and petrological). Evaluation of the behaviour of the coal during processing has ranged from theoretical modelling, laboratory-scale investigations through to pilot scale and full-scale tests. Until recently, the bulk of the work was directed at evaluating the behaviour of the coal for existing pulverised fuel (pf) firing/steam boiler technology and a high level of understanding has been developed of both the coal resource and its behaviour within these systems. More recent efforts have been directed towards the evaluation of new technologies directed towards cheaper and more efficient power generation using this coal. Loy Yang coal has been evaluated in the following technologies: ò Hydrothermal dewatering/direct coal-fired gas turbine; ò Steam fluidised bed drying; ò Solar drying/densification; ò Briquetting; and ò Gasification.

Jan 1, 1992

By Gift Makusha, Dave Minney

Anglo Coal South Africa mines coal for both the domestic and export market using open cast and strip mining methods. To establish a mine, a process is set in place to gather ever increasing amounts of geological and metallurgical data to confirm a proven reserve. Increasingly, geotechnical data are also included in this process to confirm that reserve is easily and safely mineable. The mine design process is an iterative one using a combination of numerical modelling and empirical data to arrive at a mining layout that is both, practical, productive and safe. In South Africa it is a legal requirement to compile a code of practice to combat rock fall and slope instability accidents and these have to be revised annually, reinforcing the iterative process of continual improvement. To ensure best practise occurs, all Anglo Coal operations are subjected to annual 2nd party audits and ad hoc 3rd party audit by independent consultants. This paper attempts to explain the process described above in a concise, but understandable manner. 1.0 GEOLOGICAL SETTING The Ecca sediments date from the Permian period and the coal deposits were formed in glaciated valleys on a basement of Dolomite, Ryolite or Granophyre rock types. The sediments overlying the coal deposits are typically flat lying and multiple bedded. The sediments consist of mudstones, shales and sandstones and are generally capable of forming stable highwalls given the time that they must stand up for. Anglo Coal extracts coal from the Witbank, Highveld and Vereeniging coalfields. The Witbank coalfields contain five seams numbered from the base upwards, 1 to 5 Seam; Highveld coalfield the 2 and 4 Seam and the Vereening area the seams are described as Top, Middle and Bottom seams. Coal deposited over the basement Dolomite formation display very erratic dips, as contemporaneous subsidence occurred in some instances over sinkholes that were forming, resulting in local thickening of the coal deposit and resulting in strata that dips toward the centre of the sinkhole.

Jan 1, 2006

By K. Morin

"Silver and gold leaching by cyanidation is a well-known process used around the world. This reaction is often accompanied by the leaching of other species throughtout the cyanidation circuit that causes the diversion of cyanide towards non valuable by-products (SCN-, Cu(CN)x, Fe(CN)x, etc.). One of the detrimental impacts of the formation of these by-products is the precipitation of silver-cyanide complexes that occurs when cyanide concentration is too low. Without any extra-addition of free cyanide, the precipitated silver is lost and cannot be recovered causing an important economic loss. To overcome silver precipitation, cyanidation circuits are often operated at higher cyanide concentrations. Recently, COREM’s research team has been working on a technology to measure and control silver precipitation during the cyanidation process. Moreover, a methodology has been elaborated in order to evaluate threshold cyanide level which corresponds to the cyanide concentration at which silver starts to precipitate. This technology has been tested on site on a real cyanidation circuit at Agnico Eagle’s LaRonde mine."

Jan 1, 2014

By Arun Vathavooran, Adrian Singh, Michael Fletcher, Rainer Imhof

The Imhoflot G-Cell, a new development in the pneumatic flotation technology (which incorporates centrifugal forces in the separating vessel) is a recent innovation in the mineral processing world. The G-Cell was invented by Dr Rainer Imhof and commercialised by Maelgwyn Mineral Services Ltd. In a short time span a number of plants and units have been successfully commissioned in the mineral processing industry. In addition, a number of industrial G-Cell flotation plants are in the process of construction for the purpose of coal preparation and environmental remediation. In this paper two industrial installations have been highlighted together with a pilot plant test programme investigating ultra fine flotation recovery for a base metal operation.

Jan 1, 2007

By F. E. Cash

"Explosions in bituminous coal mines are preventable. The combination of adequate ventilation, thorough rock-dusting, and water on the cutter bars of mining machines and of empty and loaded cars will certainly reduce the hazard to a minimum, if not remove it entirely. This is the attitude taken by the Woodward Iron Co. in lessening or removing the dust and gas explosion hazard from its Dolomite and Mulga mines.This report was made possible through the willingness of Frank H. Crockard, president of the Woodward Iron Co. to make records available and to authorize their publication for the benefit of the coal-mining industry.The compilation of these data and preparation of maps was facilitated by the cooperation of M. Heard, general superintendent of coal mines, J. B. Whatley, assistant general super-intendent of coal, and R. P. Whetmore, chief mining engineer.The Dolomite and Mulga mines are about 16 miles southwest of Birmingham, Jefferson County, Ala., on a company owned and operated railroad which connects ore mines, coal mines, coke ovens, and furnaces.In the Dolomite property there is a 30°, 860-foot, double-tracked slope for hoisting, three manway and air slopes and one air shaft, all in rock.At Mulga there is a 220-foot hoisting shaft, an air shaft and two manways, and material and air slopes, all in rock to the coal bed.The coal in both mines comes from the Pratt bed, which is the next coal above the Mary Lee bed in the Warrior Basin. The coal is horizontal or slightly undulating, with thickness varying from 36 to 72 inches and averaging 50 inches.The method of mining is essentially room-and-pillar with modifications for mechanized sections. The mines produced approximately 1,100,000 tons with 2,328,309 man-hours exposure n 1929 and 900,000 tons with 1,697,436 man-hours exposure in 1930.Through the work of the safety department the entire personnel in the coal mines, as well as in other departments, makes safety an essential part of efficient operation.Both mines are gassy; Dolomite produces about 334,000 cubic feet and Mulga about 919,000 cubic feet of methane every 24 hours.The ventilation maps, two of Dolomite mines (figs. 1 and 2) and one of Mulga (fig. 3) give as much of the details of ventilation as is practicable to put on maps of such scale. As will be seen from these maps there are two main ventilating fans in Dolomite mine and two in Mulga mine and the general direction of the air travel is indicated by long arrows to fan 1 and short arrows to fan 2 in each mine. Each fan has a gas or steam auxiliary drive and each mine has a complete fan and power unit ready for operation in emergency.In Dolomite, recently taken data show that fan 1 exhausts 82,000 cubic feet of air per minute at 3.2-inch water-gage pressure, with an analyzed methane content of 0.15 per cent, and fan 2 exhausts 115,500 cubic feet of air at 3.8-inch pressure and 0.10 per cent of methane. In addition, a Capell fan at No. 2 air shaft is a standby or emergency unit.In Mulga recently taken data show that fan 1 exhausts 83,000 cubic feet of air per minute at 3.0-inch pressure and 0.18 per cent of methane, and fan 3 exhaust 119,000 cubic feet of air per minute at 5.4 inch pressure and 0.35 per cent of methane. Fan 2 at No. 2 shaft is a standby or emergency unit for the Mulga mine.The ventilation is on a split system in both mines. All part split and total returns are measured, sampled, and analyzed weekly, requiring one man two days each week. During December, 1930, 77 samples were collected and analyzed in Mulga and 78 in Dolomite. Two weekly reports covering part of December, 1930, are given here so that they can be studied to show control of ventilation in the Dolomite and Mulga mines. In the event that a split sample shows more than 0.50 per cent of methane, immediate steps are taken to lower the explosive-gas content. The reports follow:"

Mar 1, 1932

The Tertiary gold deposits of the Hauraki area are predominantly epithermal vein types containing mineral assemblages of quartz, calcite, pyrite, sphalerite, galena, chalcopyrite, acanthite and native gold (electrum). Sulphosalt, telluride (eg hessite), seleniferous sulphide and selenide minerals are important locally. Studies of wall rock alteration mineralogy, fluid inclusions in gangue minerals, and sulphur isotopes of sulphide minerals indicate that the ore forming fluids had the following parameters: pH, near neutral at depth but acidic near surface; temperature, predominantly 320 - 270¦C for base metal dominated assemblages, 280 - 200¦C for precious metal dominated assemblages and generally below 200¦C for late stage barite; apparent salinity, six to zero equivalent weight per cent NaCl; and CO2 concentration, generally around one mole per cent CO2. There is fluid inclusion evidence for boiling during mineralisation in some deposits. Moderate values off S2 and FO2 are indicated for base metal and mixed base metal û precious metal assemblages of most deposits by the predominance of pyrite + chalcopyrite over other iron-bearing phases; primary bornite is absent, whereas pyrrhotite, hematite and magnetite rarely occur in the veins. The largest gold û silver deposits formed from solutions in which the sulphur species in solution were predominantly reduced. Near surface environments and some deep, predominantly base metal, deposits were formed from solutions with approximately equal concentrations of oxidised and reduced sulphur species.

Jan 1, 1984

On June 20, 1972, Ocean Energy was awarded Contract No. H0220055, entitled Portable Task Luminaire System Development. Initially, this was a 12 month program consisting of three phases: Phase I -- Design of the Luminaire System and Battery Chargers, Phase II -- Fabrication of Prototype Units, Phase III -- Fabrication of Production Prototype Units and Battery Chargers. In addition to developing the Portable Task Luminaire System, however, this contract was amended a number of times in the course of the program to include the development of a Low Coal Portable Task Luminaire, a Rib Mounted Luminaire System, and a Machine Mounted Luminaire System, all based upon the same high frequency fluorescent lighting and safety technologies involved in the Portable Task Luminaire. This report covers the activities of this program as amended, and includes the development and fabrication of all of the systems. This report constitutes the final fulfillment of the contract.

Jan 1, 1974

By Robert H. Ridgway

This circular outlines salient facts regarding the pyrites industry of the United States and the world. It is founded chiefly upon published information available in the literature of the subject. The United States Bureau of Mines has in its files additional and more detailed data upon many of the subjects presented very briefly here, and will endeavor to assist the mineral industries and the public by giving further information in response to individual inquiries. The bureau will welcome comments, criticisms, and contribu- tions of data that may assist in making later editions of this circular of information more accurate, or may aid in developing more fully the files pertaining to pyrites.

Sep 1, 1931

By Branch of Editorial Services

"The Bureau of Mines was established in the public interest to conduct inquiries and scientific and technologic investigations concerning mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve material resources and prevent their waste; to further economic development; to increase efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting those industries. The organic act of the Bureau, as amended by Congress and approved February 25, 1913, made it the province and duty of the Bureau of Mines to ""disseminate information concerning these subjects in such manner as will best carry out the purposes of this Act.""In accordance with this directive, the Bureau reports the findings of its research and investigations in its own series of publications and also in articles that appear in scientific, technical, and trade journals; in proceedings of conventions and seminars; in reference books; and in other non-Bureau publications. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make the kind of list and index presented in this special publication both necessary and valuable. This issue of the Bureau of Mines List of Publications and Articles describes reports and articles published during the period January 1, 1980, to December 31, 1984. It supplements the 50-year list of Bureau publications issued from July 1, 1910, to January 1, 1960;1 the 50-year list of articles by Bureau authors published outside the Bureau from July 1, 1910, to January 1, 1960;2 the 5-year lists of publications and articles from January 1, 1960, to December 31, 1964,3 from January 1, 1965, to December 31, 1969,4 from January 1, 1970, to December 31, 1974,5 and from January 1, 1975, to December 31, 1979;6 and the annual lists of Bureau publications and articles from January 1 to December 31, 1980,7 from January 1 to December 31, 1981,8 from January 1 to December 31, 1982,9 and from January 1 to December 31, 1983. 10"

Jan 1, 1985

By J. D. T. Steyl, C. A. Biley

"The chemistry of electrolyte systems containing iron remains generally poorly understood despite their prevalence in many natural and industrial processes, particularly in hydrometallurgy. These systems are typically challenging to study and model due to their affinity for complex formation and precipitation even at low pH. Recent developments in the hydrometallurgical processing of nickel laterites at Anglo American have called for a deeper understanding of the fundamental chemistry of the Fe2(SO4)3–FeSO4–H2SO4–H2O system. This paper details the development of an internally consistent, Pitzer ion-interaction model of this system, with explicit recognition of important contact ion pairs (CIPs). The primary application of this model is a thermodynamic framework for the interpretation of kinetic processes occurring during iron(III) reduction with SO2. Adopting a rigorous thermodynamic basis for the system chemistry facilitates the formulation of simple rate expressions that are capable of inherently capturing complex effects. While the iron(III) reduction case study remains the focus of this work, the developments have more universal applications and the thermodynamic speciation model can be extended into other systems containing acidic ferric sulfate.INTRODUCTIONIron is present in nearly all hydrometallurgical refining circuits typically as both a necessary and unwanted impurity and needs to be removed and disposed in a safe and efficient manner. This is generally performed by precipitation to form a range of solids such as hematite, goethite or jarosite. Numerous studies in the open literature have focussed on the removal of iron from refractory gold sulfide ore (Berezowsky & Weir, 1989; Berezowsky et al., 1991) and zinc pressure leaching (Buban, 1999; Ismael, 2003), and PGM matte sulfide circuits (Dutrizac & Monhemius, 1986). Moreover, since ferric iron is a strong oxidizing agent, it has been used extensively as a leaching agent for sulfide minerals (Dreisinger, 2006). Given the outlook of challenging economic conditions, declining ore grades and increasing levels of impurities, effective iron management is going to become increasingly critical to all hydrometallurgical processes.Against this background, and considering the widespread importance of acidic iron sulfate systems throughout natural and industrial processes, it is unexpected that the knowledge of the fundamental solution chemistry of these systems contains such significant gaps, particularly at the conditions typically found in hydrometallurgical applications. Existing literature describing the measurement and modelling of solution speciation in these systems have highlighted their significant chemical complexity (Magini & Caminiti, 1977; Magini, 1979; Lee & Tavlarides, 1985; Stipp, 1990; Papangelakis et al., 1994; Gil et al., 1995; Majzlan & Myneni, 2005; Kormanyos et al., 2008; Yue et al., 2014). Partially responsible for the lack of quantitative speciation measurements is the strong tendency of ferric to hydrolyse at even low pH (Flynn, 1984), complicating the laboratory study of such systems. Moreover, the large number of aqueous species that may co-exist simultaneously makes the study of individual species and the modelling of the numerous interactions between these species extremely difficult (Dry & Bryson, 1988; Stipp, 1990; Majzlan & Myeni, 2005; Kobylin et al., 2007)."

Jan 1, 2016