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By William C. Dixon

Since the mid 60's, several haul cycle simulation programs have been developed. However, most of these programs are believed to employ the continuous, rather than the discrete, event-oriented simulation approach to determine the haul cycle times. This paper describes the recently developed haul cycle simulation approach where time is advanced in varying amounts only as the system changes occur. This approach results in greater computational accuracy and increased computational efficiency. The program is written in FORTRAN and requires equipment performance curve and haul road profiles as input. Unique program capabilities include the handling of switchbacks and intersections. The program uses a master data file concept in which various haul road profiles found during the mine life can be simulated all in one job submission. The results of the model validation using the actual time study data provided by an open pit mine operator near Tucson, Arizona, are also described in this paper.

Jan 1, 1978

By N. K. Dumakor-Dupey, K. J. Bansah

"We made site visits to determine potential environmental issues caused by artisanal and small-scale mining (ASM) in the Tarkwa Mining Area (TMA) of Ghana. Activities of the diggers were observed to degrade vegetation, land and water. Improper handling of mercury was also identified as a major threat to people and ecosystem. Large abandoned pits and trenches posed fall traps to farmers, hunters and wildlife. We argue that lack of adequate monitoring and regulatory enforcement by Ghanaian authorities, together with inappropriate mining processes, probably due to lack of technical expertise are contributing factors to the environmental issues of artisanal and small-scale mining in the TMA. INTRODUCTION Environmental degradation caused by artisanal and small-scale mining (ASM) has been a major concern to many people and governments around the world. ASM is often associated with health, safety and environmental issues in communities where it is practiced (Kitula, 2006; Asiedu, 2013; Sousa et al., 2010). Some of the environmental issues that have been reported include land degradation, mercury contamination, cyanide release, and pollution of rivers/streams. These issues have been attributed to improper mining methods, inefficient technology, lack of technical training and environmental awareness, and lack of regulatory enforcement (Serfor-Armah et al., 2005; Bansah et al., 2016a; Hentschel et al., 2002). In Ghana, ASM typically occurs in rural communities, providing jobs to many people and contributing towards socioeconomic growth of the country (Banchirigah & Hilson, 2010; Bansah et al., 2016b; Osei-Kojo & Andrews, 2016). As a result of the environmental issues, many people have called on government to develop drastic measures to control ASM operations. It is in this regard that this paper examines potential environmental issues caused by ASM in the Tarkwa Mining Area in Ghana, and suggests mitigation measures to ensure environmental sustainability. ASM in the area comprises of registered (licensed) and unregistered (unlicensed) operations that adopt surface or underground mining methods to exploit gold-bearing materials. Surface operations typically involve clearing of vegetation, removal of overburden, excavation of mineral deposit, washing/grinding of excavated gravels and processing with mercury. Except grinding, washing and mercury recovery, underground operations are conducted below ground with limited impact on the surface. Alluvial mining is also commonly practiced in streams and along river banks. These activities can have devastating impact on biodiversity of the ecosystem. To achieve the objective for this study, field visits were made to ASM sites to observe operations and interact with diggers. Visits were also made to host communities of ASM and government officials to obtain their perspectives on ASM in relation to environmental impact. The study area (Tarkwa Mining Area) is located in the Western Region of Ghana (see Figure 1). It is endowed with natural resources such as gold and manganese. Hence, mining is the major economic activity in the area. ASM is widespread, with 15 registered operations and several unregistered mines. The environmental issues observed in the study have been grouped into three main categories: vegetation and land depletion; water quality and pollution issues; and mercury contamination issues."

Jan 1, 2017

By Truman P. Stauffer

Secondary use of mined-out space in underground limestone quarries is emerging in the Kansas City area where abandoned quarry sites are being renovated into warehouses, factories, and offices. Mining techniques, ceiling heights, and pillar distribution are being altered as planning for the secondary use of mined-out space is combined with the quarrying process. Even the historic urban- quarry land use conflict invites a reappraisal in that this development provides a potential resolution of the problem. Mutual subsidization by dual rock and space interest is changing the economics of rock production. A city is much more than a surficial adjunct superimposed upon the topography of an area. Its development and growth are deeply rooted in the resources, benefits and problems of its underlying geology. The environmental geologist must address himself to more than the quality of a particular resource. He must comprehensively relate resource extraction and processing with the urban emphasis of optimal use which favors long term usage of land over one time economic ventures. Limestone quarrying, closely allied with the growth of many cities, has commonly left a series of scarred landscapes in the path of the burgeoning metropolis. These abandoned quarry sites are barriers to orderly city growth and fail to serve the people as useful and taxable land. Where quarries are functional, supplying the city with needed growth minerals, problems of blasting damage, noise, and dust exist. Technology faces the challenge of making mineral production and processing good neighbors to the urban market they serve. Continued growth of cities may require more efficient use of space below as well as above the surface optimizing land usage so that long term economic benefits may be reflected in improved mining methods.

Jan 1, 1973

By R. W. Leonardson

Tectonic activity in northern New Mexico during late Oligocene and early Miocene time presaged events which led to the development of molybdenite deposits at Questa. East-northeast directed crustal extension produced north-northwest striking tensional fracture systems paralleling the early Rio Grande rift. A sequence of Oligocene andesite flows and breccias is overlain by a thick early Miocene rhyolite ash-flow tuff. Eruption of the tuff initiated collapse of the Questa cauldron: the south margin of which occurs as an east-northeast striking, north-dipping structurally weak zone. Continued east-northeast post-cauldron extension permitted the high level emplacement of granite stocks with coeval rotational deformation of fault blocks composed of cauldron fill and [ ] floor. The stocks occupy north-northwest fracture zones in the south margin of the cauldron, and porphyry dikes occupy east- northeast striking faults that define the south margin. These two fracture systems have played a dominant role in localizing the intrusive porphyries and associated mineral deposits at Questa. A molybdenite-bearing breccia matrix and related stockwork mineralization generally occur within volcanic rocks. Mineral deposits are spatially related to fault zones and the upper con- tact of their source intrusives. Deposits are localized in fault zones up to several thousand feet long and 100 to 500 feet in diameter. Magmatic-hydrothermal solutions from the source aplite porphyries have produced potash metasomatic alteration which is strongly centered on the mineral and ore zones. Alteration in ore is represented by orthoclase, quartz and secondary biotite. This pattern grades into secondary biotite and propylitic zones forming successively weaker alteration assemblages away from ore. Younger phyllic and argillic assemblages are particularly widespread only where strong north-northwest extensional fracture zones cross the south cauldron margin.

Jan 1, 2013

By A. M. Whiting

Competition for coal producers and their primary customers has constantly increased during recent years. The effects of the Clean Air Act Amendments of 1990 on the electric utility industry, coupled with the normal complexities of coal production, quality control, transportation and contracting techniques have spurred both buyers and sellers to increase their level of sophistication. This paper will review the basic aspects of the U.S. coal business and explore the commercial approaches which have proven to be most successful.

Jan 1, 1994

By Jacob Petersen, Jon J. Kellar, Samuel Kessinger, Kiran Green

Belle Fourche Shale was processed and characterized for use as a clay-based ceramic. The shale was wet sieved to produce particles that were ± 150 μm. X-ray diffraction (XRD) revealed that the -150 μm material was enriched in clay content compared to the unprocessed materials, whereas the oversize material was enriched in quartz compared to the undersize sample. Particle size analysis was performed on the—150 μm sample, which showed that the median particle size was around 10 μm. Scanning electron microscopic (SEM) analysis further confirmed the small plate size, which appeared to be primarily layered clay particles. Next, the -150 μm particles were rolled into a green body, dried at room temperature, and fired at 998°C. The fired piece was analyzed by XRD and contained 6 wt% hematite, 55% quartz, 19% microcline, and various other minor amounts of minerals. When fired at 1152 ℃, mullite was found with increasing hematite compared to the 998 ℃ firing. A multi-spectral analyzer was used to quantify the color change of the 998 ℃ fired (orange) to the 1152 ℃ fired (red) samples. Micro-computed tomography (Micro-CT) of the unfired body exhibited very few large pores, while the piece fired at 998°C also exhibited few and small pores, the overall porosity of the fired body increased. Microhardness data, obtained from the aforementioned samples, resulted in Vickers Hardness (HV1.0) values of 70.8 HV1.0 (998 ℃) and 485.7 HV1.0 (1152 ℃). Three-point bend testing was performed, giving an average strength of 23 MPa on pieces fired at 998 ℃. The average bending strength of the samples fired at 1152 ℃, was 55 MPa.

Sep 26, 2023

By M. C. Stuttle

MDL Rock Lasers has undertaken successful mapping trials of abandoned mine workings using its underground cavity scanning system. The work was being performed for Kalgoorlie Consolidated Gold Mines (KCGM), Australia's largest gold producer. MDL Rock Lasers supplies underground surveying systems to the mining and quarrying industry KCGM's Fimiston Super Pit, located in Kalgoorlie, Western Australia, is Australia's largest open-pit gold operation. Fimiston's final pit design is expected to be 3.7 km (2.3 miles) long, 1.5 km (0.9-miles ) wide and 540 m (1,770 ft) deep. During the early days of Australian mining, underground operations were labor intensive. Mining was selective and generally narrow stopes were mostly backfilled. Improved processing technology and mine mechanization during the 1970s and 1980s has permitted larger scale operations to adopt less selective underground-stope operations. The "super pit" concept was a logical step for mining companies working toward economies of scale. However, the industry recognized that there was no precedent for excavating a 500-m- (1,640-ft-) deep open pit through ground previously affected by old workings. To appreciate the geotechnical challenge facing KCGM, it is necessary to consider that under the pro¬posed area at the open pit, stoping reached a level of 1 km (0.6 miles) and was supported by more than 2,000 km (1,240 miles) of development headings. The company was fortunate because plans were available for the Golden Mile underground operations. The existing plans were interpreted by the mine's geotechnical team and computer models were constructed of the underground workings. These models can be imported into three-dimensional mine planning packages, such as the Vulcan's Unix-based software, Envisage, to assist analysis and design. This prior knowledge of the workings provided the focus for investigating and confirming ground conditions using probe drilling. After several iterations of drilling, followed by detailed analysis, several decisions were made relating to the nature of the ground and the mining approach to be taken. It was recognized that the stope models were not perfect due to hu¬man error, lack of original survey information and progressive deterioration in ground conditions. It also became apparent that the sole reliance on probe drilling was inefficient in terms of time and quality of information. This was particularly true in complex areas where stopes are in close proximity. A major concern was the presence of open stopes (voids). In many cases, stopes consist of combinations of filled and void sections. The condition of pillars within these underground workings is extremely important. In time, pillars collapse and voids will propagate in upward and lateral directions. So systems needed to be developed that allowed rapid and accurate verification of ground conditions. KCGM was introduced to MDL Rock Lasers while investigating technology for underground mining. The two companies decided to use the C-ALS, MDL Rock Laser's underground laser, cavity scanning system, to improve the management of mining through affected ground. This system was to be used in conjunction with probe drilling and void mapping activities. A field test in one area of the Fimiston Mine verified the capability of the C-ALS system to quickly and efficiently assist in this decision making process. The C-ALS scanner features lightweight, carbon fi¬ber alignment rods from Measurement Devices Ltd.'s (MDL) Boretrak MKII. This is a borehole deviation system that stops the two axis measurement head rotating and lowers the system down a borehole. The scanner is deployed by a 110-mm (4.3-in.) borehole, up, down or sideways. The operator can then carry out vertical and horizontal plan section scans at any user specified ARC (an angular increment of 2°) or the distance between two points on the ARC (CHORD) increments. Windows '95 software enables the operator to control the cavity scanner remotely, surveying the area in real time. The system makes data quick and convenient.

Jan 1, 1999

By Xie Longshui

INTRODUCTION The gold production is from the state-owned gold mines, the local gold mines and the by-product of metal mines. Since 1975, the small gold mines have developed in rapid strides. Currently, there are about 3000 small gold mines in China. Most of them are operated by the local, and the production is about 50% of China's gold output. In the small gold mines, the normalized mining equipments are employed at most of mines, but some mines still use such backward tunnelling and mining tools as pick, shovel and hand hammer etc.. The mining techniques have developed from the primitive to the advanced, especially the methods of open stope, shrinkage and filling have been widely used. Such new mining techniques as bolting, vibrating draw, non-electric ignition and diamond drilling etc. are also introduced in the wall gold mines. In recent years, the development of small gold mines is very fast under the guidance of new mining policy which is ' rapid and great development of large-sized mines, helping small mines to develop, and quick mining for the existing mines; and encouraging the collective and the individual to operate a mine.' GEOLOGICAL FEATURES The gold veins are dominant, which are divided into two types, ie. the mesothermal deposit with altered rock in a crushed zone and the hypothermal deposit with quartz veins. The orebody distribution is not centralized, and the size of deposit and single minable orebody is small respectively. Most of deposit dip at 30° to 50°, characterized by expansion and shrinkage, ramification and compound, thinning out and reappearance, separation and composite at the parallel veins etc.. The ore grade is variable, and the factor of grade change is above 100%. The waste zones with lean or submarginal ore usually exist in deposits. As for the gold deposits with altered rock, the ore boundary is indistinct. Most of gold deposits, particularly the gold deposits with altered rock, are intruded by the late structural rock, thus the faults and joints are developed, and the rock and ore are crushed, especially the host rock of roof wall is very crushed. It ie obvious that the conditions of both formation of deposit and mining are considerably complicated. HISTORY With a long mining history and rich experiences, the local gold sectors are small, but they play an important role in China's gold mining industry. Dated from Xia and Shang Dynasty, the gold goods was made. In the Tang Dynasty, the development of gold mining industry was very fast. A Chinese poem , written by Liu Yuxi -- one of famous poets in the Tang Dynasty, says: As sun is shining over Dengzhou land, The fog on river slowly goes away, The panning girls together meet at bay, The beauty's jewels and stamps of king are gold from river sand. This poem shows the local gold mining was flourishing at that time. In 1888, the local gold mining sectors were all the rage at the moment, and the annual output of gold was as high as 21.5 tons. Since the founding of New China, the development of local gold mining was subjected to several back- sets, but certain advances are made on the whole, especially since 1970. Round about 1970,the simple, backward and indigenous mining was dominant in the small gold mines; for instance, the hand-hammer drilling, the hand-operated winch hoisting and the hand haulage etc.were main methods of gold mining . Up until the late 1970s,great changes took place in stoping, haulage and so on. Currently, some advanced technology and large-sized equipments are adopted in the local gold mines. Generally, the local small gold mining sectors play an important role in development of China's gold mining industry, and are important and attractive sectors. PRESENT DEVELOPMENT

Jan 1, 1987

By Dongjie Zhang, Zeyu Liu, Shuxin Liu, Yang Liu

Lateral pressure provided by caving rocks plays an important role in keeping the stability of the sidewall rock mass and controlling the rock movement. Taking Xilinhot Fluorite Mine as an engineering background, we studied the control mechanism of the granular media lateral pressure on the rock movement by combining physical experiments, theoretical analysis, and field monitoring. The results indicated that with the increase of the granular media depth, the lateral pressure provided by the static granular media presented two stages of rapid growth and slow growth. The lateral pressure on the footwall was negatively correlated with the dip angle of the orebody, and the lateral pressure on the hanging wall was positively correlated with the dip angle of the orebody. Ore drawing only caused the granular media lateral pressure near the drawing point to decrease. As the granular media moved, the granular media lateral pressure outside the pressure reduction area further increased, and this part of the granular media would play a key role in limiting surface rock movement. On this basis, the improved calculation formula of GLMP was given, which could be better applied to calculate the GLMP and critical granular media column with different dip angles. The action mechanism of the GLMP in the control of the surface rock movement was clarified. The granular body in the collapse pit was mainly composed of three parts: the bottom loose granular media column, the middle compaction granular media column, and the upper critical granular media column. The critical granular media column was the most important area to control surface subsidence and rock movement. Finally, through field practice, after effective filling of the collapse pit, the surface vertical displacement of the hanging wall and footwall was decreased by 56.8% and 55.6%, respectively, and the control effect of surface rock movement was remarkable.

Sep 18, 2023

Diesel engines are used in underground mining 1 throughout the world. Exhaust gases from those engines contain toxic components. To protect quality in underground mines, diesel emission control was introduced decades ago, many years before the first surface applications. Today, emission controls, such as catalytic converters, are standard on underground diesel engines in countries concerned with occupational safety and health. Nett Technologies manufactures a range of diesel emission-control devices for underground mining. Emission problems are not the same at each mining operation. And there is no universal control technology. The selection of exhaust aftertreatment technology depends on raw exhaust emissions, particular emission problems, fuel quality and economics. Some of the technologies that have been used in underground mining to control diesel emissions include catalytic converters, diesel filters, fume diluters and water scrubbers. Table 1 compares the effectiveness of these technologies to control the particular components or aspects of diesel emissions.

Jan 1, 1997

By S. K. Kawatra

The use of inferential particle sizing for a closed wet grinding circuit control has been practiced for several years. This paper presents a review of some inferential sizing equations developed for pilot and industrial plants using regression analysis. An analytical development is then presented showing how the general inferential sizing model arises from the nature of the classifier model. The relation between the general sizing model and the individual equations is then discussed.

Jan 1, 1982

By W. E. Bardelmeier

The high speed conveyor type self unloading bulk carrier concept has been around for about 70 years. Although the design was developed, refined and steadily improved in the Great Lakes, to date limited numbers of such vessels have emerged in the bulk ocean trades, and these have tended to concentrate within specific mineral trades. For example, North American gypsum companies have embraced conveyor self unloaders to the point where such vessels almost exclusively carry the gypsum requirements of this part of the world. One major aluminum company has developed an impressive fleet capability in self unloaders. Application of other ships tends to be fragmented through several mineral trades. A few years ago a new phenomonen began to appear on the Great Lakes. Whereas it had historically been accepted in that region that self unloaders were effective vessels for the minor bulk trades including limestone, coal, salt, gravel and sand; they had seldom been employed heavily in the big volume iron ore trades. Suddenly, however, the new generation of 60,000 ton Lakers which emerged were all designed as high speed self unloaders. The new vessels intended to trade especially in ore, or alternatively especially in coal, have somewhat different internal features, but the important point is that all are self unloaders.

Jan 1, 1979

By K. Avarmaa, P. Taskinen

"The solubilities of rhodium (Rh) in a molten silver alloy in doré-smelting conditions for treating copper refinery slime at temperatures of 1,000 to 1,300 °C were measured using a high-temperature equilibration-quenching technique and direct phase analysis by electron probe X-ray microanalysis. The results obtained indicate that the solubility of rhodium in molten silver is very limited: only 0.04 to 0.26 weight percent at 1,000 and 1,300 °C, respectively. The thermodynamic properties of rhodium in molten silver were estimated from the solubility data. The compositions of the solid rhodium alloys in equilibrium with molten silver-rich doré metal were also measured in this study. The excess rhodium in the doré alloy will precipitate during the refining as solid, greater than 99 weight percent Rh.IntroductionSilver refining is a core step of the processes of anode slime treatment and precious metals recovery in copper refineries (Hait, Jana and Sanyal, 2009; Ludvigsson and Larsson, 2003). It separates the oxidic materials, such as nickel oxide (NiO) and barium sulfate (BaSO4), from metallics after the de-coppering and de-selenation steps of the anode slime, and refines the silver bullion from the undesired elements present (Cooper, 1990; Hyvärinen, Lindroos and Yllö, 1989). Doré metal is a silver-rich alloy which after the smelting step will be refined electrolytically, and the remaining constituents of gold as well as the platinum group metals (PGM) will be subsequently recovered in their own processing stages.Because of low concentrations of PGMs in copper, they are typically soluble in the doré metal in anode slime treatment. This can be concluded from their binary phase diagram data with silver (Massalski et al., 2007). One exception is sometimes encountered in the anode slime smelting operations if the smelter feedstock is rich in rhodium, as may be the case if the raw materials contain secondary raw materials such as e-scrap. The solubility of rhodium in solid silver is less than 0.04 weight percent (Królas and Sternik, 1995), and its solubility in molten silver is highly uncertain. The only experimental information in the literature (Królas et al., 1993; Elliott, 1985) suggests that the silver-rhodium alloy system at 960 °C forms a eutectic, which locates less than 2 °C below the melting point of pure silver (Arblaster, 2015). Early observations (Rössler, 1900) propose that rhodium is insoluble in molten silver even if solid silver-rhodium solutions have been recently produced on a nanoscale (Kusada et al., 2010).The aim of this study is to measure experimentally the solubility of rhodium in molten silver at doré metal smelting and refining temperatures. The silver alloy used to mimic the doré alloy contained silver and about 1 weight percent of the alloying elements copper, gold, palladium, rhodium and tellurium. The experiments were carried out in metal-slag equilibria with nitrogen-oxygen mixtures as the atmosphere, employing an equilibration-quenching technique and using direct phase composition analysis by electron probe X-ray microanalysis (EPMA) (Jak, Hayes and Lee, 1995)."

Jan 1, 2017

By David R. Delling

Tenneco is a large, diversified, energy-based company which has grown rapidly during its forty year life. We're the youngest corporation among Fortune's top 20 companies. Tenneco Minerals Company is the division of the Corporation responsible for nonfuel minerals exploration, development and operations. Tenneco Minerals Company is headquartered in Lakewood, Colorado. Exploration offices are in Colorado, Nevada, Alaska, and Perth, Australia. We currently operate two gold mines in Nevada and a large underground trona mine and soda ash processing plant in Wyoming. The latter has a capacity of 907 000 tonnes per year of soda ash and is the subject of my presentation today.

Jan 1, 1984

By Willard C. Lacy

Survival of the mining industry as a viable economic entity in the United States is being seriously threatened by declining grades of ore reserves, rising operational and capital costs, and increased governmental taxes, restrictions, and subsidizing of third world competition. Discovery of major high-grade deposits is becoming increasingly unlikely. International competitiveness of the U.S. deposits will depend upon 'Yankee Ingenuity', innovations in mining methods, metallurgical treatment, and financial arrangements, and a viable national strategy. This will require not only effective management for control of operations, but management that encourages breakthroughs in technology, financing, labor relations, and in public and governmental understanding. The mine geologist and the exploration geologist both have important roles to play in all aspects of this fight for survival of the industry.

Jan 1, 1984

The current understanding of the mechanics of rock fracturing during smooth blasting is largely empirical and qualitative due to an inability to model the dynamic process at the fundamental level. In order to overcome this difficulty, a numerical simulation of smooth blasting is performed using the Dynamic Lattice Network Model. This model is capable of simulating material inhomogeneities and the dynamic evolution of fragmentation at the micromechanical level. In this study, smooth blasting techniques are numerically analyzed to characterize the development of the damage rock zone during explosive fracturing.

Jan 1, 1995

By James H. Barks

Exploration for ore deposits in southeastern Missouri in the 1950's resulted in the important discovery of lead, zinc, copper and silver in 1955. Further discoveries in the area led to the naming of the Viburnum trend. It has sometimes been referred to as the "New Lead belt" to distinguish it from older lead-producing areas to the east. As presently developed, the "trend" is 35 miles long, running north and south about 50 miles west of the Lead belt. Galena (lead) is the principal ore mined, with lesser quantities of sphalerite (zinc), chalcopyrite (copper) and silver recovered as economic by-products. The ore body is as much as 140 feet thick and 1,200 feet wide, and is found in the Bonneterre Dolomite (Upper Cambrian) at depths ranging from 700 to 1,200 feet. Since its discovery many companies have engaged in exploration and several major companies have developed new mines and constructed mills and a smelter in the area. The first mine in the Viburnum trend came on stream in 1960, but as more mines came on stream and others reached capacity, lead production increased to the point that the Southeast Missouri Lead district produced 432,576 tons of lead in 1970 to become the world's largest lead-producing region (Missouri Geological Survey and Water Resources, 1971). The Viburnum trend area with its rolling, heavily forested hills and numerous clear running streams is in the Clark National Forest of the Missouri Ozarks. Until the recent development of its mineral resources, the area was sparsely populated and nearly unmarked by the activities of man. Industrial development is almost certain to be accompanied by environmental changes. In a day of growing awareness of the need to preserve the quality of the

Jan 1, 1971

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch type stirred mill. The experimental results were evaluated using stress intensity analysis. The performance was also compared in terms of mill orientation. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1*10−3 to 5*10−3 Nm at 750 and 1500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value. Additionally, to the best of the authors’ knowledge, this is the first study to compare mill orientation (vertical vs. horizontal) for the same mill and under the same test conditions.

Apr 21, 2021

By I. H. Warren

The high temperature lubricant molybdenite, MoS2, is usually produced by a complex sequence of processes involving mineral dressing of molybdenite concentrates followed by leaching with hydrofluoric acid to remove abrasive impurities such as silica (1). Many attempts have been made, mostly by techniques involving, direct fusion of molybdenum compounds with sulphur, to produce synthetic molybdenite. However, apart from some experiments of geochemical interest (2) in which aqueous solutions of sodium sulphomolybdate, Nat MoS4, were decomposed under pressure at temperatures between 300°C and 700°C, no attempts to produce the mineral by hydrometallurgical procedures have been reported. Since molybdenite is nominally a compound of tetravalent molybdenum with sulphur, and the most common state of molybdenum is +6, production of molybdenite is likely to involve reduction and sulphidization. The present study, therefore, describes the reduction, with hydrogen and carbon monoxide, of molybdenum in the hexavalent state in alkaline aqueous solutions containing sulphide ion. In these

Jan 1, 1972

By Nord L. Gale

Lead, zinc, copper, silver, cadmium and many other heavy metals which are potentially hazardous if released into the environment in wastewater discharges have been of considerable concern to governmental agencies, industry and the general public. In response to this concern, an interdisciplinary research team at the University of Missouri has been funded by the National Science Foundation-RANN program to study trace contaminants associated with the production of lead for the past eight years. Seven modern mines in close proximity to two lead smelters in the forested Ozarks of Southeast Missouri are the largest source of lead in the world and in 1976 alone produced 504,095 short tons of lead, 82% of the United States total production. This new and rapid industrial development in a sparsely populated. rural forest region has offered a unique opportunity for studying the impact of trace metals and for developing improved techniques to control detrimental effects. Research on the wastewater discharges and two methods of biological and recycle control are discussed in this paper. Although the two mine-mill complexes investigated in this study have many similarities, the differences between the two are substantive and warrant separate examination.

Jan 1, 1977