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By T. G. Digges, M. R. Achter

ALTHOUGH zone melting has found favor in recent years because of its convenience and its faster rate of production of single crystals, the older technique of strain annealing still has a number of advantages. It has been reported1 that the lattice of a crystal prepared in this manner has fewer defects than one grown from the melt and, of course, the control of the external geometry is easier. Also, the diameter of the crystal which can be grown by zone melting has a theoretical limit determined by the surface tension, thermal conductivity, and specific gravity of the material, while the size of that which can be grown in the solid state is limited only by practical considerations. In a program for the study of the structure-sensitive properties of niobium and its alloys it was desirable, for ease of handling, to have available single crystals of large diameter. This requirement dictated the choice of the strain-anneal technique. Induction heating was chosen in the present work in preference to other methods because of its deep penetration of large-diameter sections. A five-turn coil, powered by a motor generator operating at 10,000 cps, is contained in a vacuum chamber. The work is lowered through the coil for both the recrystallization and the crystal-growth steps. Starting with electron-beam melted material, the bars are cold-swaged, recrystallized, strained in a tensile machine, and then subjected to the growth step. Single crystals have been grown under the following conditions: Reduction in area during swaging— 79 to 99 pct, recrystallization temperature—1500o to 1667°C at the rate of 1.25 in. per hr, strain—1.0 to 2.5 pct, growth temperature—1600o to 2400°C at rates from 0.15 to 1.25 in. per hr. Starting grain sizes achieved after the recrystallization step varied from 0.6 to 1.55 mm. The starting grain size was found to be critical; if it is too fine and has any residual cold work, as shown by the presence of a fiberlike texture, a single crystal cannot be grown. Using this technique niobium single crystals have been grown from 0.250 in. diameter and 12 in. long to 1.00 in. diameter and 5 in. long as shown in Fig. 1. The 1-in. crystal is the largest to be reported for a refractory metal as compared to 0.500 in. for molybdenum grown by zone melting.2 As with zone melting, control of orientation is possible by the use of special procedures. Other investigators, see for example Williamson and Smallman,3 have reported that orientation control may be achieved by a bending technique. In the present work the strained rod is partially lowered through the coil to start the growth of the crystal. Then it is removed and bent at a point ahead of the interface between the single and polycrystalline portions. Finally, it is returned to the chamber and growth is continued "around the corner". The amount of bending which can be imparted to the rod is limited by coil geometry which up to now has been 10 deg. However, by repeating the bending and growing operations it should be possible to attain any desired orientation. The perfection of these single-crystal specimens as a function of process variables is being measured by X-ray and metallographic techniques and the results will be reported in a forthcoming paper. This work was partially supported by the Advanced Research Projects Agency.

Jan 1, 1964

By Jean Howard

ALTHOUGH zone melting has found favor in recent years because of its convenience and its faster rate of production of single crystals, the older technique of strain annealing still has a number of advantages. It has been reported1 that the lattice of a crystal prepared in this manner has fewer defects than one grown from the melt and, of course, the control of the external geometry is easier. Also, the diameter of the crystal which can be grown by zone melting has a theoretical limit determined by the surface tension, thermal conductivity, and specific gravity of the material, while the size of that which can be grown in the solid state is limited only by practical considerations. In a program for the study of the structure-sensitive properties of niobium and its alloys it was desirable, for ease of handling, to have available single crystals of large diameter. This requirement dictated the choice of the strain-anneal technique. Induction heating was chosen in the present work in preference to other methods because of its deep penetration of large-diameter sections. A five-turn coil, powered by a motor generator operating at 10,000 cps, is contained in a vacuum chamber. The work is lowered through the coil for both the recrystallization and the crystal-growth steps. Starting with electron-beam melted material, the bars are cold-swaged, recrystallized, strained in a tensile machine, and then subjected to the growth step. Single crystals have been grown under the following conditions: Reduction in area during swaging— 79 to 99 pct, recrystallization temperature—1500o to 1667°C at the rate of 1.25 in. per hr, strain—1.0 to 2.5 pct, growth temperature—1600o to 2400°C at rates from 0.15 to 1.25 in. per hr. Starting grain sizes achieved after the recrystallization step varied from 0.6 to 1.55 mm. The starting grain size was found to be critical; if it is too fine and has any residual cold work, as shown by the presence of a fiberlike texture, a single crystal cannot be grown. Using this technique niobium single crystals have been grown from 0.250 in. diameter and 12 in. long to 1.00 in. diameter and 5 in. long as shown in Fig. 1. The 1-in. crystal is the largest to be reported for a refractory metal as compared to 0.500 in. for molybdenum grown by zone melting.2 As with zone melting, control of orientation is possible by the use of special procedures. Other investigators, see for example Williamson and Smallman,3 have reported that orientation control may be achieved by a bending technique. In the present work the strained rod is partially lowered through the coil to start the growth of the crystal. Then it is removed and bent at a point ahead of the interface between the single and polycrystalline portions. Finally, it is returned to the chamber and growth is continued "around the corner". The amount of bending which can be imparted to the rod is limited by coil geometry which up to now has been 10 deg. However, by repeating the bending and growing operations it should be possible to attain any desired orientation. The perfection of these single-crystal specimens as a function of process variables is being measured by X-ray and metallographic techniques and the results will be reported in a forthcoming paper. This work was partially supported by the Advanced Research Projects Agency.

Jan 1, 1964

By Don S. McCoy, W. Joseoph Schlitt, Donald B. Swanson

Introduction Contract miners have long played an important role in the minerals industry. Historically, these were individuals who worked as underground miners and were paid by the ton or the day. These hardy types still ply their trade in the industry. However, today the term "contract miner" generally refers to an independent contractor who supplies the people and equipment needed to conduct surface mining operations for an owner or lease holder. At one time or another, contract miners have probably handled virtually every mineral commodity from sand, gravel, and stone quarrying to mining uranium and precious metal ores. In today's market, though, contract mining appears to be concentrated in just a few areas. These include precious metal mines, various types of solid fuel operations, and reclamation of abandoned mines. This article covers market areas, contract mining organizations and services, and their advantages and disadvantages. Gold and silver mines Although exact figures are not available, contract mining represents a significant element in the precious metals segment of US mining. For gold and silver, the growth in contract mining appears to be paralleling the overall growth in mining activity itself. Nevada is the largest gold producer in the US. The latest available data (1985) on open pit gold/ silver mines is summarized in Table 1 (Nevada Division of Mine Inspection, 1986). These figures show that contractors mined nearly half of the ore in 1985. Total tonnage mined, of course, was much higher for both owners and contractors. Assuming an average stripping ratio of 2.5 to 1, the total daily mining rate for the contractors was more than 145 kt (160,000 st). This translates into a contract mining rate of about 36 Mt/a (40 million stpy) based on 250 operating days a year. This approximate 50-50 split between owner and contractor also appears to hold for the future. Metals Economics Group (1987) published a survey of 51 short-range and 54 long-range precious metal projects being considered throughout the US. Contacts with owners, requests for proposals, and past corporate philosophies all suggest that about 55% of the open pit operations scheduled for the near-term will be contract mined. This represents an estimated 26 kt/d (28.5 stpd) of ore. A similar assessment of the long-term projects indicates that about 12 kt/d (13,000 stpd), or just under 50% of the open pit tonnage will be contract mined. There are several reasons why gold and silver represent such an attractive opportunity for contract miners. One is that many properties are owned or leased by individuals or partnerships that are essentially entrepreneurial. Many of these owners or lease holders have minimal mining experience. They must therefore either rely on contract mining organizations, sell an interest in the project to another mining company that will become the operator, or hire an experienced management team. For about the same reason, junior mining companies also represent good prospects for contracting. This is because most junior companies focus on exploration. They would prefer to spend their generally limited funds on drilling programs. Thus, they tend to minimize additional capital requirements by using contract miners or farming out the property to another mining company. Another good reason for using contract miners is the size of the deposit. Many properties are so small that their reserves will not support the capital expenditures

Jan 12, 1987

By John M. Kelly

New Mexico produced 39,751,868 bbl. of oil in 1941 and ranked seventh among the oil-producing states. Its 1941 production established an annual record, exceeding the 1940 record year by 854,498 bbl. The average daily production for the year was 108,909 bbl. The average daily non-marginal well allowable for New Mexico on Jan. I, 1941, was 36 bbl.; at the close of the year it was 43 bbl. The average daily pipe-linc runs were approximately 3 per cent less than the allocations of the New Mexico Oil Conservation Commission, which followed closely the recommendation of the United States Bureau of Mines in setting the daily outlet demand. The production in Lea County was 34,333,448 bbl.; Eddy County, 5,009,354 bbl.; and northwestern New Mexico (San Juan and McKinley Counties), 406,306 barrels. The total number of completions in the state was 402, of which 301 were oil wells, 19 gas wells, and 82 dry holes. Drilling during 1941 was 68 per cent of 1940, and the ratio of dry holes to producers, I to 4, was the greatest since 1935. Of these dry holes 43 were drilled in proven fields and 39 were wildcats. One new oil field and one new gas field were discovered as a result of the 1941 wildcatting program. However, numerous extensions were made to the existing fields, which, although they were called extensions to proration areas, were in reality field discoveries, being on separate geologic structures. Southeastern New Mexico Lea County The Monument field was the largest producing field in Lea County, with 6,973,808 bbl. It was closely followed by the Eunice field, with 6,644,181 bbl.; Vacuum field, with 4,800,608 bbl. and Hobbs, with 3,624,159 bbl. Hobbs field, however, still has the largest total recovery, this being 97,407,929 bbl. at the end of 1941. The new oil-field discovery in Lea County during 1941 was the Salt Lake field, T. 20 S., R. 33 E. The discovery well was Leonard-Welch State No. I, NW. NW. of sec. 18, T. 20 S., R. 33 E. This well was drilled to a total depth of 3103 ft. and was completed for an initial production of 250 bbl. per day pumping. The oil is 26" gravity and the producing horizon is in the San Andres limestone of Permian age. The discovery well was completed on June 22, 1941, and since that date four more producers have been completed, with no failures. The area is about 10 miles north-west of the Lynch pool, to which the oil from this field is being trucked because there is no pipe-line connection. The greatest drilling activity during 1947 was in the Maljamar field of western Lea County, with 62 completions, 59 being oil wells and 3 dry holes. The limits of this pool are now being defined on the north and south but to date have not been defined either to the east or west. The total number of 40-acre oil-producing units in the field at the close of the year was 158. On April I, 1941, a pressure-maintenance project was installed at the southern end

Jan 1, 1942

By Bradley Johnson

Introduction Since its creation in 1910, the Bureau of Mines has conducted a wide-ranging program of research on mining technology. Over the years, the Bureau has perhaps become best known for its accomplishments in mine health and safety technology, a field that has been the object of much public attention. Nevertheless, the Bureau's program in other areas of mining technology has always been strong and remains so today. A distinguishing feature of the current effort is its tendency to concentrate on high-risk, high-gain projects. Throughout the federal research establishment, the Administration's policy has been to phase out short-term research that could be performed by private industry, in favor of long-terms projects that industry cannot usually afford to fund. This tendency is evident in the following account of the highlights of the Bureau's current mining technology research program. Underground Mining Technology Fragmentation. Research studies on fragmentation have focused on nonexplosive concepts. If successfully developed, these concepts would lend themselves to continuous automated operation and reduce time and costs of fragmentation in underground mines. A special laboratory-scale device to investigate ripper cutting was designed and fabricated in 1982. Experiments were conducted with large drag cutters to develop an efficient cutting technique for hard rock. Tests were successfully conducted with 76- and 152-mm (3¬and 6-in.) bits in rocks up to 138-MPa (20,000-psi) compressive strength. Because of the success of these initial tests, larger-scale proof-of-concept tests are planned. To prepare for these tests, a tester capable of cutting a 1.8-m (6-ft) opening was fabricated. This device will allow ripper cutting to be carried out at full scale, and will also allow mucking and holddown requirements to be investigated. Preliminary estimates indicate that this concept has the potential to double excavation rates while reducing costs up to 30%. Mobile Hydraulic Monitor. A mobile hydraulic monitor system was designed, fabricated, and used to mine the St. Peter sandstone at an average rate of 22 t/h (25 stph) from a face in Martin-Marietta's foundry sand mine at Clayton, IA. A slurry transport system worked in tandem with jet cutting, resulting in a continuous mining and transport system. Problems with spray from the jet hitting the sandstone showed that a remote-controlled mobile monitor was needed at a station 15 m (50 ft) from the face, so the operator would have a clear view of the face and be safely out of the backwash. Crushers. Research on crushing systems to improve efficiency in underground mines is continuing. Final testing of a low-profile, portable crusher for underground applications has begun. A system for handling oversize feed to the crusher was conceived and tested. Underground crushing systems, portable enough to be kept near the face, offer considerable improvement in materials handling because main haulage by conveyor is often less costly. Hoists. Research to increase hoisting efficiency and speed and to reduce energy requirements has led to experimental ore skips. The skips feature guide rollers to improve riding characteristics, bearing improvement at critical locations, and weight savings of about 1.8 t (2 st). An experimental aluminum skip was installed last year at Kerr McGee's Church Rock mine. Performance is being monitored under production conditions. A portable service hoist for low-cost, efficient movement of men and supplies in raises between mine levels was designed, fabricated, and tested on the surface. The hoist has maximum equipment payload of 570 kg (1,250 lb) at

Jan 11, 1983

By J. D. Morgan

Demand for nonfuel minerals depends in large measure on economic activity, which rose in each quarter of 1985. However, despite 1.7 million new housing starts and a 7% increase in motor vehicle production, many domestic metal mining operations experienced continued difficulties as a result of import competition, greater use of newer engineered materials, emphasis on multi-unit housing, and downsizing of motor vehicles. Recognizing the continued difficulties of the domestic metal mining industry, many corporations made major efforts to retrench and rationalize - selling, closing, or spinning off less profitable operations, renegotiating labor contracts, and inviting increased participation by foreign firms. About 15% of US energy was imported in 1985. This included $52 billion worth of crude oil and refined products, adding significantly to the overall merchandise trade deficit of $149 billion. With the exception of a few large-bulk, low-value raw materials, most minerals move relatively freely in world trade. The strong dollar encouraged imports and made exporting more difficult US nonfuel minerals trade deficit totalled $17 billion. The US continued to rely on imports for many important strategic minerals in 1985 (see accompanying Table). Increased pressures for protection included major mineral products such as steel, ferroalloys, and copper. But President Reagan, in his Feb. 1986 "Economic Report to the Congress" stated: "Our international trade policy rests firmly on the foundation of free and open markets." He also stressed the need for fair trade and more open markets internationally. The National Critical Materials Council, created by law in the latter part of 1984, was activated in the latter part of 1985. Its first public hearing was held in January 1986. The Council is to review the nation's materials posture and advise the President on such matters. Compared with 1984, the value of US raw nonfuel mineral output rose 2%, to $24 billion. This supported the production of $244 billion worth of processed materials of mineral origin. Raw steel production - a major indicator of both material use and mineral production - fell 4% to 81 Mt (89 million st). Consequently, domestic iron ore production fell to 49 Mt (55 million st), about 97% pelletized. Iron ore imports fell 7% to 16 Mt (18 million st). Raw steelmaking capacity fell 4% to 117 Mt (129 million st). Pacts with 16 leading steel exporting nations have been negotiated in an effort to reduce import penetration of the domestic market. Domestic producers of bulk ferroalloys of chromium, manganese, and silicon operated at about 40% capacity. The US mined no manganese or chromium. Only a small quantity of ferronickel was produced from domestic laterite mining in Oregon. Molybdenum production increased slightly to 49 kt (54,000 st). Mine shipments of tungsten, another mineral tied to steel production, also fell slightly to 1.1 kt (1200 st) of contained metal. Even the domestic aluminum smelting industry suffered reverses as high stocks and low prices reduced production 16% to 3.5 Mt (3.8 million st). Similarly, imports of bauxite fell 7% and alumina 10%. Production of magnesium metal fell 6% to 136 kt (150,000 st), while titanium metal production remained unchanged at 22 kt (24,000 st). Copper mine production was unchanged at 1.1 Mt (1.2 million st). Copper refinery production fell slightly to 1.1 Mt (1.2 million st). Lead mine production rose 24% to 400 kt (440,000 st). Zinc mine output was down 10%, to 225 kt (250,000 st). Refined lead production increased 28%, to 510 kt (560,000 st). Primary slab zinc production fell 5% to 240 kt (260,000 st).

Jan 5, 1986

By Y. C. Guan

The cementation of gold on to copper and zinc in ammoniacal solutions has been studied using rotating disc electrodes. The cathodic reduction of aurous ammine was studied on a gold rotating disc electrode and the anodic dissolution of copper and zinc was studied in the absence of aurous ammine. The cementation rate was found to be a first order with respect to the concentration of aurous ammine and to be proportional to the square root of the disc rotating speed. Based on the results obtained, it was concluded that the cementation reaction was controlled by mass transfer of aurous ammine to the reaction surface under the experimental conditions.

Jan 1, 1995

By Kenneth McGowan

"The aluminum industry is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating accounts for 25% of the energy consumed to manufacture aluminum. Consequently, the generation of this energy results in the production of a significant amount of CO2 (over 3.75 million metric tons in 2003)1. As a result, the Aluminum Industry Technology Roadmap of 2003 listed the development of improved refractory materials as a goal to reduce energy use and decrease greenhouse gas creation. The result of a R&D effort addressing this desire is the development of patented microporous refractory materials for metal contact applications in all furnace areas including the belly band. It has been demonstrated that this material can reduce energy consumption up to 38% in furnaces and significantly reduce heat loss in launder and trough systems. Furthermore the material developed is non-wetting and remains un-penetrated by metal throughout its lifetime. The material does not contribute to the formation of corundum. As a result, the energy efficiency of an older lining remains intact compared to standard refractory materials which may have an initial high insulating value (such as lightweights and board) or standard dense refractory (even with penetration inhibitors) both of which show a rapid increase in thermal conductivity as the refractory is penetrated with aluminum and formed corundumIntroductionThe aluminum industry is the second largest producer of metal in the United States, behind the iron and steel industry. It is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating is required to melt, hold, purify, alloy, and heat treat the metal and accounts for 25% of the energy consumed to manufacture aluminum. As such, process heating is the second largest energy consuming operation. Smelting, which utilizes an electrolytic reduction process is the largest energy consuming operation1.Most process heating is accomplished through the use of fossil fuels, either directly or indirectly. The choice of fuel is dependent on a plant’s location and fossil fuel availability. Table I shows the processes impacted by refractories and the calculated BTU’s generated by usage of the respective fuels as well as the Metric Tons (MT) of metal passed through each process in 20001."

Jan 1, 2009

By Alan H. Goode

Of the 15 million tons of glass discarded in municipal wastes annually, about 2 million tons pass through incinerators and can be recovered by ore processing techniques. Although the primary use for this recovered waste glass would be as cullet in the manufacture of new glass containers, this approach is not always practical because of long shipping distances, high freight costs, and high purity requirements. Alternatives to the use of waste glass as cullet would be either as landfill or in secondary products. Although glass is considered a good landfill material, it is still wasteful of potentially valuable raw materials. Secondary products that can be made from waste glass1 include a variety of industrial and construction items. As part of the Bureau of Mines' program in secondary materials recovery, the Tuscaloosa Metallurgy Research Laboratory has conducted research concerned with the development of ceramic building products from waste glass. Materials employed in this research were obtained from municipal incinerator residues fractionated in the Bureau's continuous residue processing plant, College Park Metallurgy Research center.' The studies reported herein3,4 present research results using waste glass in the formulation and production of clay bricks, not only to produce improved products, but to reduce production costs, conserve natural raw materials, and most important, to reduce manufacturing energy requirements.

Jan 1, 1974

By I. Raposo, I. Moreno-Ventas, A. Palma, M. J. Díaz, M. Vázquez

The oxidative degradation kinetics of chalcopyrite have been studied by thermogravimetric analysis (TGA). The obtained data are necessary for the kinetic description of the flash fusion process, which can contribute to the optimization of the smelting process in copper extractive metallurgy. Activation energy (Ea) evolutions of the involved processes have been determined by several isoconversional methods; in this sense, the chalcopyrite oxidation processes could be adequately described, among studied models (E1641–16, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman), by the Kissinger–Akahira– Sunose kinetic model. Using this method, Ea and A values are found to be very dependent on the conversion. Under lower conversion levels, higher Ea and A values have been calculated with respect to that found for medium and higher conversion levels.

By G. A. Johnson

Basic management principles will be discussed (as they apply to minerals education efforts), especially in light of the changing nature of volunteerism in today’s society. Also, the “minerals education tree” will be presented, along with public opinion / public policy realities.

Jan 1, 2001

By Edward E. Johnson

The U.S. economy made significant progress in 1984. The current-dollar gross national product (GNP), the market value of the Nation's output of goods and services, increased almost 11 percent over that of 1983 to slightly more than $3.66 trillion (table 1), and the real gross national product increased almost 7 percent.2/ Such rapid growth in real GNP has not occurred since the early 1950's. Real final sales increased only 5 percent during 1984, and real business inventories increased $24.8 billion ($57.9 billion in current dollars). Total employment of 106.7 million was an all-time record, and the unemployment rate declined from 9.5 percent in 1983 to 7.4 percent in 1984. During 1984 the U.S. dollar showed great strength on international markets, contributing to large current-dollar negative net exports of goods and services (-$62.5 billion) and even larger negative net exports of merchandise (-$107.6 billion). The strong dollar and the substantial increase in net imports of goods and services helped reduce U.S. inflationary pressures and provided a major source of loanable funds for financing domestic private investment.

Jan 1, 1985

By Thomas M. Barczak

he stiffness characteristics of longwall shields were investigated in this Bureau of Mines study. Since longwall strata activity is characterized by roof-to-floor and face-to-waste displacements, a model with two degrees of freedom was used to describe the load-displacement relationship of the shield structure. The model considers the support as an elastic body and relates horizontal and vertical resultant forces acting on the support to associated displacements as a function of the stiffness of the support structure. Stiffness coefficients under full canopy and base contact configurations were determined by controlled displacement loading of longwall shields in the Bureau's Mine Roof Simulator (MRS). Three two-legged longwall shields of different manufacture were investigated. The stiffness characteristics of these shields were evaluated relative to two parameters, namely, shield height and setting pressure. The test results indicate a reduction in shield stiffness for increasing height. Setting pressure was found to have less of an effect on shield stiffness, producing only a slight increase in stiffness as setting pressure increased. Similar trends were observed for all three shields, indicating a similarity in stiffness characteristics for shields of the same basic configuration.

Jan 1, 1988

By A. S. Choudhary

India is endowed with a reasonably large reserve of chrome ore, amounting to about 100 million tons in different grades and is one of the leading producers of ore/concentrate along with South Africa, Kazakhstan and others. Chromite production in India has registered a 10 times increase during the last 30 years. Till late 1940s, the practice was to mine the high-grade ore for making ferrochrome and charge chrome and export the same leaving the low and medium grade ores stacked around the mine as waste material. This practice was continued for quite some time till the increase in world wide de-mand of chromite initiated an increase in production of chromite ore in India and the aspects of ?economy of operation? and ?conservation of mineral? dawned on the producers and associated authorities. Recovery of chrome values from low and medium grade ore was initiated to produce high-grade saleable concentrate. Suitable legislation was made by Government of India to induce and provide incentives to the operators to do so. First large scale chromite beneficiation plant in India was commissioned about three decades back at Byrapore in the Southern state of Karnataka. The ore, rather simple in nature and relatively free from clay, was obtained from underground. The processing consequently was simple washing and wet tabling. Further more, some test work, on the samples from eastern coast particularly from Orissa, was carried out at an internationally reputed laboratory by a large private operator and the plant was set up. This consisted of a combination of crushing-grinding-de-sliming-classification followed by concentration in multi stage spiral concentrators and shaking table. The plant was commissioned and operated successfully. Soon a state owned company followed suit on the basis of test work carried out in a well equipped Indian laboratory. The plant worked satisfactorily after some initial teething trouble and the company plans to double the existing plant capacity by installing balancing facilities. This development prompted a number of operators, including industry leaders to join the fray and the chrome ore processing industry flourished in India. More and more operators are now in the process of adding capacities to their existing plants. This paper attempts to chart the evolution of chrome ore beneficiation industry in India through a case study with reference to an existing plant. The process technology adopted and modified to suit the altered requirements as well as the future trends are outlined.

Jan 1, 2014

By Elimame Elaloui, Kais Elghniji, Constantin Virlan, Aurel Pui, Chaima Ouled Amor

Separation and identification of minerals composing the Tunisian silica sands have been conducted by acid etching and hot filtration/sedimentation (HFS) without affecting the quartz component. It was found that the hot acid etching process is an effective method to separate quartz and clay minerals in the silica sand. The SEM micrographs of the silica sand show rough surface and some cracks with irregular shapes. The surface becomes clean and smooth after acid etching process. After chemical dissolution, the clay minerals were recovered by hot filtration following by sedimentation at low temperature. FT-IR, EDS maps, and secondary electron (SE) analyses of separated clay minerals reveal the presence of Fe2O3, montmorillonite, and kaolinite minerals. The LIBS analysis of clay minerals shows the presence of Al, Fe, Ca, Al, and Mg. The sequential etching process can be introduced in the purification methods as an effective way to separate quartz from clay minerals.

Jul 29, 2020

By Chuan-Jian Zhong

Gold-based nanoparticles in the size range of a few nm have attracted increasing interests in catalysis, sensors and biomedical applications. The study of the unique catalytic properties of nanosized gold was inspired by the pioneering work of Haruta on the nanogold-catalyzed CO oxidation (1-4). There have been a number of excellent reports discussing both fundamental and application aspects of gold nanoparticles in catalysis (3-8). Our work reported herein is aimed at investigating the preparation and application of gold and its alloy nanoparticles for potential applications in fuel cell catalysis. Fuel cells operating by electrochemical oxidation of hydrogen or methanol fuels at the anode and reduction of oxygen at the cathode are attractive power sources due to their high conversion efficiencies, low pollution, lightweight and high power density. While methanol offers the advantage of easy storage and transportation in comparison with hydrogen fuel cell, its energy density (~2000 Wh/kg) and operating cell voltage (0.4 V) are much lower than the theoretical energy density (~6000 Wh/kg) and the thermodynamic potential (~1.2 V). The poor activity of the anode catalysts and inefficient activity or issue related to "methanol cross-over" at the cathode electrode are associated with the loss of about one-third of the available energy at the cathode and the other one-third at the anode. Extensive studies have been focused on Pt-group metals (Pt+Pd+Rh+Ru+Ir (PGM)) for both anode and cathode catalysts. A major problem is the poisoning of Pt by COlike intermediate species (9,10). Recently, oxide-supported gold nanoparticles in the <10 nm size range have emerged as one of the best catalysts for CO oxidation (1-3,11), and for water gas shift reaction in reforming stage using 5 nm Au on Fe2O3 (6). Gold and its alloy with other metals in the nanosize range present new alternatives (2,12). Whether the unique properties of gold nanoparticles can be exploited for addressing these problems is a focus area of our work. The ability to harness the large surface area-to-volume ratios and the unique surface sites of nanoparticles in <10 nm size range, especially in heterogeneous catalysis, constitutes a major driving force in fundamental research and practical applications of nanoparticle catalysts. It is this size range over which the metal particles undergo a transition from atomic to metallic properties. The understanding of factors controlling the morphological and surface reconstitution associated with such a size range is of fundamental importance to the ultimate exploration of nanostructured catalysts. We have been investigating the interfacial structures and properties of core-shell types of nanoparticles consisting of gold or alloy nanocrystal cores and organic monolayer shells that were prepared by twophase synthesis (13) and processing (14) protocols. Important attributes of such nanoparticles include controllable size monodispersity, processibility, and stability towards size- and composition-tunable catalysis (15-21). Some of these attributes were studied for understanding their electrocatalytic properties in the oxidation of methanol and reduction of oxygen, which are of fundamental interest to fuel cell technology.

Oct 1, 2003

By N. D. Ilankoon

"The use of thiosulfate as an alternative lixiviant for cyanide to treat complex refractory ores followed by the use of ion exchange resins (IX resins) for gold recovery has become an industrial reality. In this study, polyethylenimine (PEI) coated iron oxide magnetic nanoparticles (MNPs) were used to recover gold from the leaching solutions that consist of calcium thiosulfate, copper and gold. The gold loaded MNPs were easily separated from the solution using an external magnetic field. Proposing a novel adsorbent with characteristically easy solid-liquid separation, to recover gold from synthetic thiosulfate leaching solutions and gold elution and reuse of MNPs were the main objectives of this study. Adsorption isotherm studies revealed that the data fitted both Langmuir and Freundlich isotherm models equally well. The maximum adsorption capacity was 18.5 mg/g at pH 8 and 50?C. According to thermodynamic studies the physisorption process was exothermic and spontaneous. Gold and copper elution, and the regeneration and reuse of the nanoparticles were investigated and promising results were obtained. Different elution systems comprising sulfites, chlorides, glycine, EDTA (ethylenediaminetetraacetic acid) and sodium hydroxide were considered. Among them, EDTA for copper elution and NaOH for gold elution were the most efficient eluants. Regeneration and reuse studies revealed that the MNPs can be used for several cycles without significant performance loss. INTRODUCTION Although cyanidation has been used for gold leaching for more than 100 years, some major drawbacks associated with cyanidation have led to a quest for alternative lixiviants for gold leaching. Cyanide is ineffective in treating carbonaceous refractory ores as gold cyanide complex is adsorbed onto the native carbon in the ore itself known as preg-robbing. On the other hand environmental concerns associated with cyanidation drives the need for environmental friendly alternatives for cyanide. As of today, thiosulfate is known to be the most extensively studied and most promising alternative lixiviant for cyanide in both technical and environmental perspectives (Aylmore and Muir 2001, Oraby 2009)."

Jan 1, 2018

By Henry E. Swanson

In the early 1960&apos;s the Company, then named the United States Smelting Refining and Mining Company, was drilling the Continental ore body located near Fierro, New Mexico. Reserves of underground ore of sufficient quantity were indicated to build a mill. At the same time some ore from the Continental No. 1 mine was being milled at the Company&apos;s Bullfrog Mill, formerly a lead-zinc mill. The copper ore in comparison to the lead-zinc ores was very hard, abrasive, and heavy. These factors pointed out the possibility and attractiveness of autogenous grinding. While prior to this some study had been given to autogenous grinding, no large scale tests had been made. Such a program was carried out and from the pilot plant data the following was established: 1. Grinding of the ore by autogenous means could be accomplished. 2. This could be done in one stage; however, not at a satisfactory tonnage throughput rate. Thus, the use of a secondary unit has been employed. 3. Grinding in the secondary unit could be done by pebbles generated in the primary unit. This resulted in the scheme whereby the ore would be ground 100% autogenously. 4. Liberation of the copper minerals was excellent so that good recovery at a satisfactory concentrate grade would be obtainable.

Jan 1, 1976

By M. K. Mohanty

A modified coal flotation characterization procedure, referred to as the Advanced Flotation Washability (AFW) technique, has been developed which, compared to traditional procedures, provides a more accurate prediction of the optimum separation performance achievable by a froth flotation process. The AFW procedure uses a vertically-baffled flotation column which provides enhanced selectivity among particles of varying degrees of hydrophobicity due to a plug-flow environment and an improved carrying-capacity environment. In fact, the separation performance of the traditional procedures was enhanced by increasing the possibility of operating under improved selectivity conditions. The separation performance provided by the AFW procedure was superior to that obtained from multiple cleaning stages using commercially-available flotation columns under both kinetic and carrying-capacity limiting conditions.

Jan 1, 1997

By J. A. Botín

Investment decision for large mining projects imply an enormous financial risk and therefore, require a more complex risk evaluation methodology taking into account all sources of uncertainty from each process in the project value chain. Generally, the main sources of risk are those related to uncertainty on grade and other techical variables of the orebody. In this study, conditional simulation is applied to develop a risk management model to quantify and to manage financial risk associated to uncertainty on the grade of the orebody. The model was validated in case study on a real porphyry copper orebody in Chile.

Feb 23, 2014