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By P. K. Sharma

The acidophilic and chemolithotrophic Thiobacillus ferrooxidans bacteria grown in the presence of soluble ferrous ions and solid substrates (sulfur, pyrite and chalcopyrite) as their energy source have been used in the investigations. The cell surfaces are characterised by zeta-potential, contact angle, FT-IR and FT-Raman studies. The adsorption isotherms of the cells on pyrite and chalcopyrite indicate that the adsorption begins on pyrite at a much lower equilibrium cell population than on chalcopyrite. The isotherms tend to level off at a cell adsorption density corresponding to a horizontal monolayer coverage when the geometrical dimensions of the cells are considered. In the presence of cells, the xanthate flotation of pyrite completely depressed, whereas chalcopyrite flotation is unaffected. The results suggest that chalcopyrite can be selectively floated from pyrite, also at a neutral pH region, in the presence of T. ferrooxidans cells.

Jan 1, 1999

By Richard W. Hornung, Steven Samuels

A great amount of work in recent years has been devoted to refining older survivorship models, e.g. life tables, and developing newer ones, e.g. Cox regression. In this paper, these models are applied to data from an epidemiological study of uranium miners in four western states conducted by the U.S. Public Health Service. One of the principal problems addressed in this paper concerns the appropriateness of using cumulative dose as the measure of radiation exposure. An alternative is considered that incorporates dose rate into the model. This procedure does not implicity assume that equal cumulative doses produce the same lung cancer mortality, but instead considers the amount of time in which each miner's dose was accumulated. Results of the statistical analysis indicate that dose rate is a significant factor at higher cumulative dose levels, with lower dose rate apparently more damaging than higher dose rate. The shape of the dose response curve is curvilinear at higher dose levels. No interaction was found between smoking and radiation exposure on a multiplicative or relative scale.

Jan 1, 1981

NIOSH is conducting research to reduce the silica dust exposure of workers at surface coal mines. One goal of this research is to evaluate the relationship between drilling parameters, rock strata and silica dust generation. This study involved measuring blast hole emission dust from a rotary drill rig which required sampling high concentration dust (>400 mg/m3) for silica content in a high velocity airstream. To measure dust initially, traditional sampling methods using personal sampling instruments were attempted in and around the shroud area of the drill with no success. Variations in the dust cloud concentrations under the shroud, the condition of the shroud and its orientation over the hole, and ambient air conditions prevented consistent and accurate dust measurements from being obtained. Amore consistent dust cloud is necessary for accurate measurements. An area of the drill’s dust collector system that consistently draws the emitted airborne dust from the hole is the collector tube. This tube connects the drill collector’s vacuum and dust filtration system to the shroud area. Assuming the collector system is working as designed, sampling from the collector tube would enable more consistent and accurate samples to be taken. However, current personal samplers are unable to sample in the concentrations and velocities experienced in the collector tube, so another method had to be devised. To achieve the desired results, an in-stack cascade cyclone was used. Preliminary field testing shows positive results.

Jan 1, 2003

By J. R. Batista, J. C. Young

Leachates from gold heap-leaching mines may contain selenium concentrations as high as 2 mg/L. Previous studies report satisfactory selenium adsorption by activated alumina from relatively "clean" drinking waters. However, the findings of these studies cannot be directly applied to the treatment of mine leachate where other ions compete for the alumina adsorption sites. This study evaluated the adsorption of selenium from a mine leachate to develop design parameters for a full-scale activated alumina process. The study revealed that 68% of the selenium in the leachate could be removed by alumina at pH levels greater than 5.0. At pH levels less than 4, silica was poorly adsorbed by alumina, and selenium adsorption was improved. Silica adversely affected the selenium adsorption capacity.

Jan 1, 1998

By D. T. Maiers, P. L. Wichlacz, P. A. Pryfogle, J. H. Wolfram

The effects of metal solution concentration, biomass density, length of exposure time, and pH were determined for biosorption of molybdenum (Mo) and chromium (Cr) by three organisms. Results indicate that it is possible to sorb Mo and Cr from dilute solutions. Differences were observed in the abilities of an organism to sorb Mo and Cr as well as among respective abilities of the three microorganisms. This suggests an inherent selectivity of the organism which may afford the means to control a sorption-based process. Results also indicate that the metal sorption abilities of these microorganisms depend on duration of exposure, biomass density, solution pH, and the metal concentration of the solution. Each of these parameters suggests an additional means of controlling the sorption process.

Jan 1, 1989

By H. Sis, D. Dahlin, S. Chander, C. Summers

Bench-scale selective-flocculation tests were conducted on samples of Florida phosphate and Western phosphate process tailings to recover upgraded phosphate concentrates. After physical and mineralogical characterization, the slurry samples were treated with a broad suite of flocculants with a range of molecular weights and anionic functional groups. Parameters investigated included pH, dispersant and flocculant types, and dose; conditioning parameters and settling times were, for the most part, held constant. Where selectivity was achieved, phosphate minerals remained dispersed, whereas silicate minerals flocculated and settled. Single-stage tests using reagents with low to medium anionic characteristics produced upgraded phosphate concentrates at moderately elevated pH. Two- stage site-blocking tests, in which low-molecular-weight flocculants were used as site-blocking agents, gave improved results.

Jan 1, 2002

By Richard L. Ranich, Frank F. Aplan, J. B. Hiskey, Robert S. Thompson, B. J. Scheiner

Acidic waters typified by acid mine drainage, copper dump leach solutions and steel pickle liquors will typically contain SO4-2 and cations such as Fe+3, AI+3 and for the pickle liquors, sometimes Cr+3. These acidic waters will often react with limestone, present naturally or introduced for purposes of solution neutralization, to form reaction - inhibiting coatings of gypsum and gelatinous, metal hydroxide precipi¬tates. The coating thickness, as a function of pH, was quantified for both reactive (calcite, limestone) and non-reactive (quartz, barite, fluorite) minerals, and the data were related to the hydroxy species diagrams and to solution turbidity measurements. Coatings were found on the reactive minerals at a lower bulk solution pH than on the non-reactive minerals.

Jan 1, 1993

By William H. Langer

Nearly every community in the United States is dependent on aggregate (sand, gravel, and crushed stone) resources to build and maintain its infrastructure. Unfortunately, developing aggregate resources to meet societal needs causes environmental impacts. Most environmental impacts associated with aggregate mining are benign. Extracting aggregate seldom produces acid mine drainage or other toxic effects commonly associated with mining of metallic or energy resources. The most obvious environmental impact of aggregate mining is the conversion of land use, most likely from undeveloped or agricultural land use, to a hole in the ground. This major impact is accompanied by loss of habitat, noise, dust, blasting effects, erosion, sedimentation, and changes to the visual scene. Some of the impacts are short-lived, and most are easy to predict and easy to observe. Most impacts can be controlled, mitigated, or kept at tolerable levels and can be restricted to the immediate vicinity of the aggregate operation by employing responsible operating practices and available technology. The intensity of environmental impacts generated as a result of mining are determined in large part by the geologic characteristics of aggregate deposits (geomorphology, geometry, and physical and chemical properties). Mining deposits that are too thin, or contain too much unsuitable material, results in the generation of excessively large mined areas and large amounts of waste material. Mining aggregate can lead to serious environmental impacts in some situations. Some geologic environments such as active stream channels, slide-prone areas, and karst terrain are dynamic and respond rapidly to outside stimuli including aggregate mining. Some geomorphic areas and (or) ecosystems underlain with aggregate serve as habitat for rare or endangered species. Similarly, some geomorphic features are themselves rare examples of geologic phenomena or processes. Mining aggregate might be acceptable in some of these areas, but should be conducted only after careful consideration, and then only with extreme prudence. Failure to do so can lead to serious, long-lasting, and irreversible environmental consequences, either in the vicinity of the site or at locations distant from the site. Environmental impacts caused by irresponsible aggregate mining can compromise mining in an entire region.

Jan 1, 2001

By Andrzej Wala, Tom Altman, Tom Hughes

The University of Kentucky Mine Ventilation Manager (UKMVM) is a system that contains Level Five knowledge bases and comprises an expert mine ventilation management system. The package uses production rule language (PRL) to interpret data monitored from sensors, e.g., for airflow, temperature, and concentration of gases, in an underground mining environment. Activated from the PRL knowledge bases are Pascal subprograms which (1) organize the monitored data to set up emergency consultations, (2) display graphic representations of a mine's ventilation network with the latest sensor readings, (3) provide interactive updating of mine ventilation parameters, e.g., resistance changes, revised flow requirements, and new regulator and fan settings. Also activated from these knowledge bases are programs which (1) monitor airflow, temperature and gas concentrations from a physical mine ventilation model and (2) adjust regulator openings and fan rpm's. Thus, as an expert system the UKMVM not only presents advisory consultations for underground environmental emergencies, but also serves as an interface between the monitoring and responsive control aspects in the continuous maintenance of normal mine ventilation.

Jan 1, 1989

By M. Li, J. D. Miller

It has been discovered that water insoluble alcoholic solutions of alkyl hydroxamic acids serve as selective collectors for the flotation of phosphate mineral resources (Miller et al., 2000). The effectiveness of the new collector chemistry has been demonstrated by the results from single stage bench scale flotation experiments for feed material from plants in Florida, North Carolina, and Utah. In the best case, from experiments with low grade (5% P20,) coarse feed (16 x 35 mesh), a single stage phosphate recovery of 95% was achieved with a concentrate grade of 31% P20,. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collectors as is evident from a comparison of the respective grade/recovery curves.

Jan 1, 2002

By K. Saberyan

A technique is described for the solvent extraction of zirconium. In this method, zirconium has been extracted quantitatively from 0.005 M sodium salicylate solution at pH 2.5 - 3 using 0.01 M triphenylphosphine oxide dissolved in toluene as an extractant. Zirconium has also been recovered quantitatively from 0.2 M potassium thiocyanate solution, but extractions in nitric and hydrochloric acids (as media) were negligible. The resulting extracted metal ion has been stripped with sulfuric acid (0.5 M) and determined with inductively coupled plasma atomic emission spectrometry. This method has been applied successfully to achieve 95% recovery of zirconium from zircon concentrate.

Jan 1, 2010

By P. A. Plunkert, D. E. Morse, L. McCartan, S. F. Sibley

Following the recession of 2001, restrained consumer spending, declines in domestic manufacturing and industrial output, and increased unemployment led to a lack-luster year in the domestic economy. In 2002, the U.S. real gross domestic product (GPD) grew only 2.4%. Significant production declines in the U.S. metals industry were registered by copper, lead and zinc producers. Steel producers, despite a slight improvement in shipments, continued to face strong foreign competition, higher energy costs and lower prices for their products. Homebuilding and other domestic construction sectors— major consumers of nonmetallic mineral products such as cement, brick, glass and stone — remained strong enough to help raise the output of industrial mineral materials slightly above 2001 levels. A strong U.S. dollar relative to other national currencies continued to weaken the competitive stance of U.S. metal and non-metal mineral materials companies alike against foreign producers in markets at home and abroad.

Jan 1, 2003

By Paul B. Queneau, Barry J. Hansen, D. Erik Spiller

Most lead and zinc secondaries are recycled pyrometallurgically. However, many problems encountered in secondary smelters have been solved by addition of physical concentration and/or hydrometallurgical processing steps, with resulting important environmental benefits. U.S. secondary lead and zinc operations are described, covering conventional smelters, EAF-dust treaters, and zinc sulfate/fertilizer producers, including plant capacities, technologies, and outputs. During the past two decades, remarkable advances have been achieved by recycling spent lead-acid battery components. Interaction between primary and secondary zinc producers, the fertilizer industry, and the zinc chemical industry has substantially decreased waste generation.

Jan 1, 1993

By S. Zaman, F. F. Aplan, Franklin T. Davis

This section deals with the oxides of heavy metals, namely, columbium and tantalum, rare earths, chrome, manganese, titanium, tin, and tungsten. Table I contains the production figures for each of these commodities in the US and in the world in 1977. Specifications for concentrates are also summarized as well as prices for concentrates in 1977. In each chapter an attempt has been made to describe the more common commercial mineral involved with the commodity and the processes used to recover and concentrate the minerals, as well as geographical areas where these processes are utilized.

Jan 1, 1985

By Jean-Luc Cornet

Downhill, or regenerative conveyors have always been a challenge to the design engineer due to their natural instability under load. The last decade has seen the appearance of high tonnage, high negative lift conveyors with several hundred meters of drop. These conveyors have made necessary the development of new braking systems and intelligent drive controls to address their starting and stopping requirements under various load conditions. This paper describes the critical design criteria of large regenerative conveyors and some of the advances in mechanical braking systems and drive control technology developed by Conveyor Dynamics, Inc. (CDI) to address their specific requirements.

Jan 1, 1993

By Walter Meintrup

On Nov. 4, 1981 the newly installed 1000tph wet-process iron-ore ball mill of A/S Sydvaranger completed its first four months of uninterrupted, successful full-load operation in Kirkenes/Norway. This 6.5m diameter mill is driven by a gearless ring or wrap-around motor of 8100kW at 13.1RPM - a first of a kind in this segment of industry. (Fig. 1) This paper analyses the reasons that have led to the selection of this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes in some detail the installation in Norway. General aspects of possible design variations, and application information for designers and users of such mills conclude the presentation.

Jan 1, 1982

By David B. Campbell

INTRODUCTION This submission was made to the Royal Commission of Inquiry into uranium mining in British Columbia. It discusses the stability of waste rock piles that might be developed in conjunction with uranium mining and the control of leachates that might be generated within these waste rock piles over the short and the long term. Short term refers to the interval during which a waste rock pile undergoes either continuous, or alternatively intermittent development, and in general can be considered to extend over the operating life of the mine. Long term refers to the postmining period, i.e. after the ore-body has been exhausted, and mining operations have ceased. Two major classes of waste material are generated in the course of mining and milling operations. Tails, which are the solid waste materials produced by the milling operations commonly exit the mill in slurry form and are stored in tailing retention ponds. Management and control of these slurried wastes are the subject of other papers to the Commission and this conference. In the course of the mining operations, it may be necessary to remove rock materials that are below cut-off grade. That is, ore concentrations within some of the mined rock may be lower than the concentrations which on the basis of economic considerations justifies milling the material. Rock which is removed in the course of the mining operations, but which is below cut-off grade is referred to as waste rock. This waste rock is commonly consigned to a specific area for disposal where it is placed in a mound or pile, i.e. a waste rock pile. Ore concentrations within the waste rock may vary from zero to just below cut-off grade. Since an increase in the market value of uranium could at some time in future result in reduction of the cut-off grade, it follows that waste rock containing ore concentrations slightly below today's cut-off grade could become ore grade rock at some time in future. For this reason, the mine operators may deem it advisable to separate waste rock according to grade, and to consign the waste rock to two or more individual waste rock piles. For purposes of clarity and simplicity, this submission treats the stability of waste rock piles and leachate control in a manner which assumes that these potential problems are isolated and separate from other aspects of the mining and milling operations. For many site specific cases, the problem of potential leachate control might be integrated with the tailings management aspect of the project, thereby realizing economic benefits while at the same time reducing the potential for adverse environmental impact.

Jan 1, 1980

By I. Iwasaki, K. A. Smith, X. Cheng

A cathodic decomposition model was examined for both pyrrhotite and chalcopyrite in an attempt to analyze the formation of surface coatings in deoxygenated solutions at natural, near neutral pH. Combination potentials established between the mineral-grinding media pair were simulated by applying a potential of -0.455 V (vs. a standard hydrogen electrode) either to a pyrrhotite or to a chalcopyrite electrode. Chronoamperometry was used to study the polarization behaviors and alteration of mineral surfaces through cathodic processes. The kinetic parameters of cathodic decomposition of pyrrhotite and chalcopyrite were determined and compared. It was concluded that pyrrhotite decomposed faster than chalcopyrite in near-neutral pH solutions. Both minerals were then covered by a film consist¬ing mainly of iron hydroxides, which adversely affected their flotation.

Jan 1, 1999

By D. G. Krige

Discussion by D.G. Krige I read the paper "The jackknife approach" with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be station. When this feature is evident, the relative variograms for the subpopulations (i.e., with variogram values divided by the relevant mean squared) will be similar, or they could even be accepted at an averaged model for the whole ore body with stationarity. Using this approach, the kriging variance will reflect the relative error variance that is to be multiplied by the kriged block grade estimate squared to yield the usual kriging variance for purposes of confidential limits. The objection that the kriging variance does not take into account the local grades used for a block valuation then falls away. In the example given by the authors, the global mean grade is not recorded. But the global variance, taken at the value of the total sill, is 0.005, whereas the variance of the 11 values used in the example is 0.000152. The two variances differ by a factor of nearly six. If the relative variogram approach is applicable in this case, the need for a jackknife technique will fall away. Also note that, for skew distributions, the confidence limits for ore-block estimates will be skew as well, and symmetrical normal limits will not apply. RepIy by G.S. Adisoma and M.G. Hester There are a few interesting ways to utilize the block-by-block kriging variance that the authors have encountered. One of them is to classify a particular block into a proven-probable reserve or a possible-resource category, using a somewhat subjectively determined kriging variance value. Here, the kriging variance still represents the drilling density, i.e., data configuration more than the data values. Professor Krige mentions another ingenious approach through the use of relative variograms. This will yield a block kriging variance that takes into account local (block) grade, as he correctly points out, for purposes of confidence limits. However, we are more interested in quantifying the uncertainties associated with grade estimation in a much larger scale than a block. e.g., for a mining phase or the minable reserve. The jackknife, through the block kriging shortcut, provides a simple solution to obtain a single estimation variance for a general shape. The authors' main reference discusses different ways to handle skewed distributions typical in mineral resource estimation, e.g., the weighted jackknife approach or data transformation. Also, as with any technique, we can always improve our estimate by subdividing into smaller populations that are geologically and statistically separate domains. As we have mentioned; the jackknife is but a tool in our collection of tools to solve estimation problems. The jackknife's appeals are its simplicity and versatility. It is handy when no other solution is available, or when the available solution is not practical. It is used with other methods, not to replace them altogether. ?

Jan 1, 1997

By A. Warren Wilson, Hugh R. Wilson

This paper describes the evolution of the Waste Management Program at the Lupin Mine through the years 1982 - 1986. Echo Bay Mines' Lupin Mine is located on the western shore of Contwoyto Lake in Canada's Northwest Territories about 80 km. south of the Arctic Circle. The gold mine commenced production in 1982 and the Waste Management Program was based originally on the total containment concept. Due to an expansion of the mill circuitry and increased throughput, it was apparent that total containment was no longer applicable and therefore studies were undertaken to characterize the tailings, to evaluate the effectiveness of natural degradation of contaminants in the tailings pond and to determine what additional treatment steps would be necessary to meet the requirements of the mine's Water Licence. These studies indicated that arsenic and cyanide concentrations in the tailings pond decant water would not meet Water Licence discharge limits unless certain measures were under taken. As a result of this work, in late 1984 a decision was made to create a two-ponds-in-series system and the necessary civil work was started in 1985. In addition, a series of dykes were constructed to contain the solids portion of the mill tailings in a confined area of the first pond. To remove cyanide, the ponds are operated in a sequential fill and decant mode to take maximum advantage of natural degradation. For arsenic removal, a chemical feed system was constructed for iron salt addition to the decant stream from the first to the second pond. Decanting of the ponds is accomplished by means of a series of 500 mm (20 inch) Sclairpipe syphons.

Jan 1, 1987