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By Seong- Rin Lim

Light-emitting diodes (LEDs) are regarded as environmentally friendly light sources due to their high energy efficiency and lack of mercury content. LEDs are used for a variety of domestic and commercial lighting systems, where they are replacing incandescent and fluorescent lamps at a rapid rate. Incandescent lamps inefficiently consume energy because electricity is mostly converted to heat rather than light. This causes unnecessary environmental impacts and energy consumption associated with power generation and transmission from a life cycle perspective. Although fluorescent lamps are more energy-efficient than incandescent lamps, their disposal at end-of-life presents special challenges because of the presence of toxic mercury. Despite the seemingly apparent advantages of LED, very few studies have rigorously addressed potential environmental consequences of their disposal. Specifically, LEDs are designed with III-V semiconductors that presumably consist of toxic and rare materials, including arsenic, gallium, and indium. We hypothesize that, depending on their concentrations and leachability, these constituents may also contribute to render LEDs as hazardous waste at the end of their useful life.

Jan 1, 2010

By Gregory A. Knapp

Treatment of industrial wastewaters generally advances with specific chemical concentration and mass-flow targets, established by National Pollutant Discharge Elimination System (NPDES) permits. Treated discharges must also address toxicity to test and receiving water organisms. Various parameters might need consideration during treatment design and planning, such as the known toxicants, hardness, alkalinity, solids, nutrients, metals in both the dissolved and particulate state, and even flow. Since toxicity is used as a "catch all" regulatory monitoring tool, design of treatment systems should focus on the various factors contributing to toxicity.

Jan 1, 1996

By David Minson

On many occasions, operators have seen that high density and paste thickener performance does not meet the initial design expectations, and the installed equipment produces lower than expected thickener underflow solids content. This lower-density tailings slurry leads to more water and lower beaching angles being seen at the tailings storage facility (TSF). This not only reduces storage capacity, but also increases the risks of non-compliance with environmental permit constraints. Reasons for the shortfall in performance can be many, but perhaps the main problem is inadequate understanding of the critical components of thickener design and operation, with too much reliance placed on standardised design terminology; such as tph/m2. This paper discusses additional factors that influence high-density thickener operation and presents test work that defines “Dynamic Slurry Fluidity”, “Bed Compaction Rates”, and “Natural Slump Angles” for these high yield stress/viscosity slurries. Finally, the paper uses this data to define thickener geometry, drive torque, floor slope(s), rake blade configuration and how this can be used to provide engineers with more tools for in depth evaluation of a High-Density thickener design. INTRODUCTION Generally copper mines are high tonnage operations, with copper flotation concentrators producing high volumes of tailings slurries of milled solids and water. As a result, Tailings Storage Facilities (TSF) become very large and this, along with potential scarcity of water, favours a design that maximises storage space. In theory, the use of filtration equipment that achieves immediate water recovery, high TSF in-situ densities and high stacking angles are preferred for this duty. However, large tailings filter units are uncommon, and have high operating and capital costs that favour the use of thickeners. The use of high-density thickeners to produce a thick or near-paste like slurry with high un- sheared yield stress values above 100 Pascals, is becoming more common. The higher thickener underflow is required to not only maximise water recirculation within the mill, but to also increase beaching angles, maximise tailings storage capacity and minimise evaporation losses arising from large areas of superficial water. However, the reliability of this equipment is also under scrutiny and there is perhaps a need to better define these designs.

Jan 1, 2019

By G. Budge

In the extractive industry the term ‘continuous improvement’ (CI) usually means procurement of the latest state of the art equipment. This is generally perceived as the only way to add further value to the supply chain, with the driving philosophy of increased tonnage to dilute operational costs. However, not all market places can facilitate this approach. RJB lives in a fiercely competitive market and has targeted the standard efficiency drivers of rationalisation and stock management with a vengeance; and also operate CMMS (Computer Maintenance Management System), RCM (Routine Condition Monitoring)and CBM (Condition Based Maintenance) methodologies. Ultimately though, these systems are only as good as the people who operate and manage them and to add further value without procurement, people must be re-introduced back into the operation. Through TPM (Total Productive Mining), that is what RJB have set out to do.

Jan 1, 2001

By Joseph Cervik

Gas occurs in coalbeds in an adsorbed and a free gas state. Adsorbed gas is stored in the micropore structure and its transport is governed by Fick's law. The free gas occurs in the fracture system and flows according to Darcy's law. These two modes of mass transport are interdependent. Production decline curves of coal-gas wells are of the constant percentage decline type and, thus, show no indications of flow characteristics peculiar to coal-gas reservoirs. The effectiveness of surface boreholes as a degasification scheme depends upon both good fracture permeability and a high fracture density. Conventional methods of reservoir engineering analysis are not applicable to coalbeds

May 1, 1969

By Richard J. Mainiero

The Bureau of Mines has developed a prototype nonincendive explosive rock-breaker charge that can be fired unconfined in underground bituminous coal mines without the danger of igniting a flammable atmosphere that might be present. At present, unconfined shooting in underground coal mines is prohibited, but there are situations where the use of such shots would yield an overall improvement in safety. The charge consists of l-1/2 lb of permissible water gel explosive in the form of a short cylinder 7 inches in diameter and 7/8 inches high, surrounded by a l/2-inch-thick layer of damp salt, and encased in latex rubber reinforced with cheese cloth. The latex rubber housing provides a charge package that is strong enough to resist rough handling yet is pliable enough to conform to an irregular stone surface. A charge of this shape was found to be more effective at breaking rock than charges with lined or unlined cavities. Incendivity tests in a gallery have shown that the prototype charge will not ignite a flammable methane-air atmosphere when fired. Rock- breaking tests made with limestone boulders indicate that the charge will satisfactorily break stone slabs weighing 1 to 2 tons, and that two or more charges might be effective for slabs weighing up to 10 tons. In cooperation with the Mine Safety and Health Administration (MSHA), a test protocol for the certification of these charges as "permissible" for use in flammable atmospheres is being developed.

Apr 1, 1982

By J. D. Hadden, Albert Sainato

The Bureau of Mines conducted drilling studies in the Pocahontas No. 3, the Pittsburgh, and a western coalbed to establish the gas migration characteristics for each. Gas pressures in the Pittsburgh coalbed were about 260 lb/in2 and in excess of 550 lb/in2 in the Pocahontas No. 3. Caving in drill holes prevented pressure measurements in the western coalbed. The Pittsburgh coalbed contained intersecting "clay veins" which formed gas pres- sure cells. Although these geological features hamper mining, they can be used to control the flow of methane into a mine working. Methane control techniques are proposed for the Pittsburgh and Pocahontas No. 3 coalbeds.

May 1, 1969

By C. H. Elder

An experimental degasification program using a vertical borehole and vacuum pump to drain gas from the gob area of a longwall panel was successful at Bethlehem Mines Corporation, Cambria Division, No. 33 coal mine. Sixty-one million cubic feet of methane has been exhausted during a 9-month period. Daily production time in the panel increased as a result of lower methane levels in the returns. Removal of large quantities of methane in this way and the exclusion of it from the ventilating system will provide reduced cost in mine ventilation and provide a safer environment for the mine.

May 1, 1969

By Joseph Cervik, J. H. Perkins

The Bureau of Mines has conducted desorption work on fine coal particles at near atmospheric pressure. An apparatus has been developed that uses a capacitance manometer to measure desorption of methane from coal particles up to 2 inches in diameter and pressures up to 1,000 psi. This will make it possible to duplicate the desorption process as it occurs in its natural under- ground environment.

Aug 1, 1970

By W. M. Merritts, Charles Findlay, Stephen Krickovic

Methane emission rates were studied in a Pittsburgh coalbed mine in northern West Virginia. A fullface boring-type continuous miner, equipped with a methane monitor, was used in the development of a set of eight main headings, one side of which was near old workings; the other side abutted virgin coal. Two air splits ventilated the section. Air volumes and methane percentages were recorded, and time studies of the miner were made during five consecutive operating days, during which a complete cycle of mining the headings and one line of related breakthroughs was accomplished. Methane emission rates increased significantly as mining progressed from the side near old mine workings toward the virgin area, and generally increased with coal extract ion. Mining in the heading immediately adjacent to virgin coal was interrupted quite frequently, owing to excessive methane concentrations at the face, despite adequate air volumes and acceptable methane concentrations in the immediate return airway.

Aug 1, 1970

By G. E. Rennick, F. E. Armstrong, J. Pasini, J. R. Abrams

An oil well penetrating the Pittsburgh bituminous coalbed in northern West Virginia was plugged and safely mined through 3 months later. A sensitive chemical tracer, introduced into the oil reservoir before the test, was not detected in the mine air following the plugging and during mining of the pillar and penetration of the well. Effectiveness of the plugging in preventing reservoir gas from entering the mine through the well hole was verified by continuous monitoring of the mine air for indications of sulfur hexafluoride, an inert gas detectable in amounts as minute as 112 part per billion. Expand- able cement and fly ash-gel-water slurry were utilized to seal the well above and below the coal seam. Three other wells were also plugged using various techniques.

Jul 1, 1972

By Stan Merjan

Composite piles with precast concrete tapered pile tips (TPT Composite Piles - U.S. and foreign patents) are a new and important addition to the piling types available to the construction industry. TPT Piles were invented by Stanley Merjan, Vice President of Underpinning & Foundation Constructors, Inc.. U. F. C. installs these piles in the Northeast United States and licenses piling contractors in other parts of the country. TPT Piles have been developed for use in sandy subsoils at depths to 70 feet or greater. The TPT system (see Figure 1) is simple. A pile stem of conventional material (shell, pipe, steel, wood, precast concrete) is connected to a socket formed in a precast concrete tapered pile tip (TPT). This composite assembly is then driven as a unit by ordinary pile driving methods until adequate driving resistance (established by formula or load tests) is met in a suitable soil strata. This driving resistance develops from the displacement and densification produced by the TPT. Many combinations of tip shapes and stems are available to suit particular job requirements with respect to subsoil conditions and pile capacities. TPT Piles should be considered for use on a wide variety of jobs. The advantages offered by a TPT installation include: ? High capacity piles in marginal soils ? Minimal lengths required to produce these capacities ? The use of conventional pile driving equipment and procedures ? Pile inspection techniques that are the same as for ordinary pile driving Furthermore, TPT piles are economical due to a combination of a low cost per ton of pile capacity and high productivity, both of which lead to significant savings in foundation costs and time required to complete foundation work.

Jan 1, 1987

By Marton A

The Readymix Group have a Quarry Improvement Program - 'Building in Quality (BIQ) which has many parallels to the ICI Explosives' total quality management - 'Quality Improvement Program' (QIP). Both companies have for some time recognised that the 'do it right first time' principle means less wasted effort and materials, that efficiency breeds profitability and so actively promote the quality culture. To install the principles and generate the culture requires considerable commitment and effort from the top down and invariably spreads to the suppliers and sub-contractors. Understanding the component processes involved with the quarry operation, analysis of those processes and gaining a breakdown of the cost of non conformance then allows the astute quarry operator to make the necessary changes to improve the process to realise profits. This paper outlines the steps in such a process and the profitable outcomes of the commitment to continuous improvement at the Nickol Bay Quarry.

Jan 1, 1994

By B P. Scott

Podsol soil horizons developed on Pleistocene glacial sediments overlying the Coronation Mine orebody were analyzed for copper and zinc spectro-photometrically, using biquinoline-isoamyl alcohol and dithizone carbon tetrachloride reagents. Copper and zinc are concentrated in the A. and C horizons, whereas the A1, A2 and B horizons are leached. Of economic significance is the fact that the C horizon contains a copper anomaly, in excess of 100 times back-ground, directly over the orebody. Due to the erratic distribution of high copper concentrations in the Ao horizon with respect to the orebody, that horizon is not considered as a reliable prospecting datum. U NDER certain conditions, metallic ore deposits are accompanied by primary halos of trace elements in unweathered rock surrounding the orebodies or by secondary halos in weathered rock, alluvium, soil, or vegetation above or near the mineralized zones. Where such halos occur, chemical analysis, as applied to the detection of trace elements, is a valuable prospecting aid, permitting the detection of mineralization of possible economic value.

Jan 1, 1965

By I. de Jong, G. Van Weert

Silver cyanide adsorbs extremely well on activated carbons. This suggests that the addition of soluble silver salts to trace cyanide containing waste streams should allow efficient cyanide removal with active carbon. Silver losses, however, would make this method expensive and also objectionable, since silver has biocidal effects. When silver impregnated carbon is used, these problems are overcome. Test work has shown that such silver remains on or in the active carbon, that cyanide concentrations can be reduced to the level of detection (< 5 ppb) and that the silver impregnated carbon can be reactivated with equipment similar to that now in use at gold milling operations. Initial results on the type of carbon, the impregnation procedure and the level of silver, and the effect of repeated regeneration are discussed.

Jan 1, 1992

By M. P. Nackowski, Armond H. Beers, W. T. Parry

Three hundred soil samples were collected on a one-mile grid in a 400-square mile area of the Oquirrh Mountains, Utah, including the Bingham-Lark, Ophir, Rush Valley, and Mercur mining districts. The soil samples were analyzed for copper, lead, zinc, silver, molybdenum, manganese, and iron by X-ray fluorescence using arsenic as an internal standard. Anomalies coincide in most cases with the mining districts. However, in the Mercur district no anomalies were detected. Also samples collected one mile from the Bingham mine barely reflect this major producer. No samples were collected within the Bingham mine area.

Jan 1, 1973

By T. Luterbach, V. T. McLemore

"Trace element analysis of placer gold can be used as a valuable exploration tool in order to determine the original deposit source and locating lode gold deposits. Placer gold collected from multiple districts in New Mexico and Alaska, coupled with a broad database of previously analyzed placer gold samples indicate correlations between chemical signatures (especially gold, silver, and copper) and type of deposits (i.e., Au-rich copper porphyry deposits, Au porphyry deposits, and epithermal deposits). By completing a chemical analysis and determining the particle morphology of placer gold collected from these districts using an electron microprobe, patterns in the chemical signatures from each location can be used to examine chemical variability (1) within the individual placer gold particles, (2) within the same district and (3) among different districts. INTRODUCTION Although there are numerous past studies on the chemical composition of placer gold by Newberry et al. (1997), Melchiorre (2001, 2009), Townley et al. (2003), and McLemore et al. (2014), the gold analyzed tends to be collected from one or few specific districts. Rarely do those studies compare compositional results to additional districts, or elaborate on the correlation between the elemental composition of the placer gold and the original deposit source for the respective districts. This research analyzes the composition of placer gold from multiple districts and within the same district. There are a number of elements, which can, in various quantities, be present in placer gold particles. Native gold can be in complete solid solution with native silver and contain additional elements including Cu, As, Pb, Fe, and S. The chemical signature of the gold is determined by the thermodynamic conditions of precipitation and transport as well as the total metal content of the system. As Townley et al. (2003) explains, “These thermodynamic conditions and metal budget differ from one type of hydrothermal deposit to another, and hence different deposit types will each have a characteristic gold compositional signature.” Identifying this signature can be a highly valuable tool in exploring for gold, as it can not only be used to determine the original source deposit of the placer gold, but provide valuable insight as to the erosion level of the present deposit."

Jan 1, 2016

By Stephen Chryssoulis, Stamen Dimov

Detection and quantification of precious metals (Au, Pd, Pt, and Rh) in spinels and silicate minerals is important for establishing the maximum attainable recovery by sulphide flotation. To achieve this goal subpart per billion (ppb) detection limits are required plus the ability to quantify results. Existing quantitative microbeam techniques (EPMA, PIXE, SIMS, TOFLIMS) have limits of detection in the O. l-200ppm range. Time-of-flight resonance ionization mass spectrometry (TOF-RIMS) is a microbeam analytical technique that allows for the identification and quantification of atomic species in very small quantities. It utilizes a tunable laser source for resonant excitation and ionization of a particular element of interest and has some unique features: elemental selectivity, linear response over a large dynamic range and very high sensitivity. The analysis consist of three steps: (i) the solid sample is vaporized by laser ablation to form a plume containing neutral atoms, (ii) the neutral atoms of a specific atomic element in the plume are resonantly excited and ionized by another tunable laser, and finally (iii) the ions created are mass analyzed in a time-of-flight mass spectrometer. A TOF-RIMS mass spectrometer was developed at AMTEL for trace element analysis of Au, Pd, and Rh in minerals. The spectrometer was calibrated using homogeneous CANMET and NIST reference samples covering three orders of magnitude in concentration. Attained minimum detection limits (MDL=2cr of the background) are in the low ppb range.

Jan 1, 1999

By ANGELA NAIR AVELAR, Reiner Neumann, PAULO R. G. BRANDÃO

The understanding of the influence of the different types of apatite on the performance of mineral processing of igneous phosphate ores is still a challenge due to the difficulty to explain why some types of apatite floats in the froth flotation cell and others do not under the same conditions. Three types of apatite were identified by means of cathodoluminescence (CL) images in flotation concentrate and tailing samples from the Catalão mine: predominantly blue apatite, followed by green apatite and less frequently yellow apatite. The chemical composition of these types of apatite was determined by electron microprobe analysis (EPMA) and LA-ICP-MS. Blue and green apatite respond well to the process, thus remaining in the concentrate, while yellow apatite remained in the tailings. Yellow apatite is the one bearing the lowest P2O5 content and the largest anionic and cationic sites substitution, followed by green apatite, whereas blue apatite is the most homogeneous, with highest P and Ca grades and lowest substitution level. A negative correlation of the amount of phosphorus with fluorine was observed. Furthermore, impregnation of iron oxide-hydroxides in the yellow apatite was also observed. Therefore, the low flotation behaviour is due to low crystallinity coupled with impregnation onto its surface.

Jan 31, 2022

By R. L. Teseneer

Pyrite samples from twenty-one locations in the North Carolina Slate Belt were analyzed for cobalt, gold, mercury, and nickel by atomic absorption spectrophotometry. The geographic distribution of relatively high values of certain trace elements in pyrite suggests that, in addition to gold, cobalt and nickel metallogenetic provinces are possible in the slate belt. Northwest trends of province boundaries may be genetically related to subsurface features rather than to surface geology. Within province boundaries gold and nickel exploration programs should be concentrated in areas containing intermediate to mafic tuffs, while cobalt may be more concentrated in argillites and phyllites.

Jan 1, 1979