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By Garrett May

We present a periodic technique for measuring the thermal conductivity of thin, disk-shaped samples. In samples of this type, temperature measurements must be made across the sample faces and are therefore subject to large error due to the interface resistance between the temperature sensor and the sample. The technique uses measurements of the amplitude and phase of the periodic temperature across both a reference sample and the unknown material at several different frequencies. Modeling of the heat flow in the sample allows the simultaneous determination of the thermal parameters of the sample as well as the interface resistance. The technique is demonstrated on nanocomposite samples less than 1.0 mm thick.

Jan 1, 2008

By C McIntosh, M van Dam, N Whetter, R Lane, M McCulloch

Mine geology is understood through synthesising large amounts of structural, lithological, geochemical and geophysical data derived from the original topographic surface, drilling and surfaces exposed and removed during open cut and underground excavations. Computer- generated 3D geological models of any mine environment need to incorporate large amounts of information but also should be regularly updated with typically frequent influxes of new data. Geologists with the local knowledge should also be involved in the model construction, enhancement and interpretation, placing ease-of-use functionality high on modelling software requirements. Implicit-style modelling is a fast-growing area of 3D geological software development where interpolated surfaces such as lithology boundaries and bedding orientations are defined mathematically as functions rather than explicitly through coordinate meshes. The functions are constrained only by the data and not by an artificially imposed grid; therefore, implicit 3D modelling can process a lot of information quickly and routinely operate on original data (such as observed contacts and structural data) rather than on evolved iterations and interpretations. 3D mine geology models can be readily updated with new data, which can be automatically reprocessed to test ideas in near-real time. Implicit, function-based 3D modelling software has been applied to the Globe-Progress mine in West Coast, New Zealand. This structurally- hosted gold mine has some geometrical conundrums that are in part being resolved as excavation of the open pit proceeds. The relationship of the Globe-Progress ore shoots to hanging wall and footwall structure is still not fully understood, however, and 3D geological modelling is assisting with visualisation and testing of structural hypotheses. The modelling is also capable of predicting areas of bedding defect slope failure in yet-to-be excavated parts of the mine.

Jan 1, 2009

By Harry C. Gatos, Frank J. Bachner

It was shown through high-pressure experiments that tin loss by volatilizatim is necessary for the degrada-tion of the superconducting transition temperature of Nb,Sn associated with high-temperature annealing. Crystallochemical analysis of the degraded Nb3Sn showed that it constitutes a new phase with ordered niobium-site vacancies, created by the migration of niobium atoms to vaccnt tin sites. This new phase was found to form when 4 pct Nb-site vacancies were present. It has a transition temperature of 6'K and a lattice parameter of 5.283A. A similar degradation effect was observed in Nb,Al. Its superconducting transition temperature dropped from 16.5" to 8" K following a high-temperature annealing. The superconducting temperature degradation in these 0-tungsten structure compounds is attributed to the disruption of the interchain d bonding by the periodic interruption of the niobium atom chains. By annealing the degraded Nb, Sn at 1000 C in nitrogen its normal superconducting behavior is restored most likely due to the incorporation of nitrogen atoms causing the elimination of the ordered vacancies. HANAK et al.' have observed low superconducting transition-temperature values (T, - 9"K) in some NbsSn samples deposited from the vapor phase. They attributed such low T, values to disorder in the 0-tung-sten structure. Much lower T values (down to 5.6"K) were reported by Reed et al.zC for NbsSn samples annealed at high temperatures. These authors also attributed this degradation effect to disorder (random occupation of the A and B sites by niobium and tin) but pointed out that such disorder could be brought about (by high-temperature treatment) only in samples containing niobium in excess of the stoichiometric composition NbsSn. Both groups reported that the normal superconductivity behavior could be rever-sibly restored by appropriate heat treatment. Courtney et al., also found that degradation in NbsSn requires excess niobium brought about by the loss of tin during the treatment. However, these investigators proposed that the degradation is due to niobium-site vacancies resulting from the migration of the niobium atoms to the vacated tin atom sites. They did not consider the reversibility of the effect. The present study attempts to establish the nature of the above degradation phenomenon. EXPERIMENTAL PROCEDURES All compounds prepared for this investigation were made from the powders or filings of the elements which were intimately mixed, cold-pressed into a cylindrical pellet at approximately 50,000 lb per sq in., and then submitted to the desired heat treatment. The samples annealed under high pressure were placed in a MgO sample container which was mounted in a pyrophyllite tetrahedron designed for a tetra-hedral-anvil press. Details of the experimental arrangement are given elsewhere. This setup allowed heating at 1800°C or above under pressures in excess of 30kbars for 3 hr. The samples annealed in a vacuum were prepared in a high-temperature vacuum furnace which could reach temperatures up to 2400°C under a pressure of 2 x lo-' Torr. For annealing in a reactive atmosphere, a quartz tube was placed in a clamshell furnace and the desired gas ambient passed through the tube. Lattice parameters were determined using a Debye-Scherer 114.6-mm camera. Cohen's method, programmed for the IBM 7094 computer, was used to calculate the lattice parameter from the measured d spacings. X-ray integrated intensity measurements were made on several samples. These samples were ground to -400 mesh and the powder mixed with a solution of collodion in amyl acetate. The mixture was poured into a depression milled in a bakelite disc. When the mixture dried, the surface of the disc was ground flat leaving a diffraction surface defined by the face of the disc. The disc was mounted in a Philips rotating specimen holder which allowed the rotation of the sample in the plane of the diffraction surface and the integrated intensity measured using a scintillation counter and a pulse-height analysis sys-tem. The superconducting transition temperatures were determined by means of self-inductance techniques.' EXPERIMENTAL RESULTS AND DISCUSSION The Role of Tin Loss in the Degradation of Super-conductivity. The loss of tin during high-temperature annealing can be effectively suppressed by annealing under high hydrostatic pressures. Accordingly, a series of experiments were performed under pressures of approximately 30kbars. This pressure was the minimum under which high-temperature experiments could be safely performed in the particular pressure apparatus employed. Experiments were also designed to test high-pressure effects on the superconductivity behavior of NbJSn. The results of the high-pressure annealing experi-ments are summarized in Table I. All samples were prepared as described earlier. They were reacted and homogenized at 1000°C for 24 hr under argon at-

Jan 1, 1967

By Larsen. Edward P.

The principle of "bed blending" in the agglomeration of materials is about 56 years old, but de- spite all education via technical papers, operating reports and results from functioning installations, the concepts of blending are still somewhat vague. Confusion exists between "mixing", "blending," and the basic role of each. The terms "blending" and mixing" are often used interchangeably, yet they describe two different processes. As properly understood and applied, a blend is a combination of different varieties of material which produces a desired quality, or the mingling of different elements to form a harmonious whole. In other words, blending is a process of combining granular materials by mechanical means, wherein the final product, or a portion thereof, must contain an exact proportional amount of every one of the several different materials which contributed to the mass and wherein all particles are so thoroughly intermingled with each other as to have lost their individual identities and become a part of the whole so that when a portion of the blend is taken at any time it will be substantially identical, chemically and physically, to any other portion taken throughout.

Jan 1, 1962

The mineral resources of Hamersley Iron are structurally complex with fluctuations in mineral chemistry. Besides orebody charact- eristics, mineral recovery is also affected by stringent product quality demands from the competititve steel industry. Under such conditions, a geological ore reserve estimate has little meaning because it is unqualified and presupposes the defini- tion of ore. A system was developed in Hamersley - the Mine Planning Technique - to optimise recovery from available resources. This incremental planning method reduces a geological reserve statement into a simple, logical sequence of events. While there are limitations in the method used, the benefits are enormous. Among its' numerous applications, the schedule - the end product of the technique - plays an important role at Management level in decision making and policy formulation on all aspects of resource exploitation.

Jan 1, 1979

By Vincent A. Scovazzo

Benchmarking is a business management process that seeks improvement through the study and reapplication of practices conducted by industry leaders. This discussion presents objectives and organization of benchmarking applied to mining geomechanics. Similar procedures have been successfully applied to mining companies, laboratories, and research organizations involved in mining geomechanics throughout the world. Benchmarking is a structured process that allows an organization to learn from the "best" in the field. The objectives of benchmarking vary depending on the company's targeted areas for improvements. Typical goals include ground control cost reduction, enhanced safety, optimization of geotechnical staffing, development of state-of-the-art design procedures, or the adoption of the "best in the field" geotechnical data management. Once the objective of the study is established and the practices and procedures to be benchmarked are identified, a benchmarking team is formed from internal and outside specialists. Benchmarking in geomechanics is fundamentally different than in most other fields because of the effects of local geologic conditions and regulations, both of which must be understood by all on the benchmarking team, before a comparative analysis can be made.

Jan 1, 2000

Discussion of the paper of BOYD DUDLEY, JR., presented at the New York meeting, February, 1915, and printed in Bulletin No. 96, December, 1914, pp. 2767 to 2782. H. 0. HOFMAN, Boston, Mass.-At the close of the paper Mr. Dudley said that his experiments in the laboratory had shown that it was possible to separate nickel from copper by means of a chloridizing roasting, but that in order to demonstrate a process of this kind, work upon a large scale would have to be carried out. I think it was in 1913, that experiments of this kind were carried out at the works of the Pennsylvania Salt Manufacturing Co., Philadelphia, in a Wedge furnace, and at Sault Ste. Marie in a Sjöstedt furnace. They showed a satisfactory separation of nickel and copper. The ore was first subjected to an oxidizing roast, then mixed with pyrite and salt, and given a chloridizing roast. A. H. Carpenter published in the Engineering and Mining Journal, vol. xcvii, p. 1085 (1914) the details of this work. The conclusion arrived at is, that if you subject sulphide ore to an oxidizing roast, finishing at the temperature at which all nickel sulphate is dissociated, i.e., 764° C., then mix it with pyrite and salt, and subject the mixture to a chloridizing roast between 600° and 700° C., you can chloridize a high percentage of the copper without chloridizing any of the nickel, and obtain thereby a satisfactory means of separating the two.

Jan 5, 1915

By M. S. Moats

"The effects of commercial copper electrorefining additives (glue and thiourea) on the electrochemical removal of bismuth are of importance in copper production. It was found that Bi(III) electrodeposition occurs readily from acidic sulfate solution via a diffusion-controlled quasi-reversible reduction. The diffusion coefficient of Bi(III) was measured and found to be less than reported values of copper in similar solutions. The presence of thiourea and/or glue was found to accelerate or de-polarize Bi(III) reduction on stainless steel as compared to the inhibition or polarization of Cu(II) reduction. The additives also inhibited the dissolution of the Bi-Cu co-deposit during cyclic voltammetry. During short term deposition studies, the additives increased the concentration of Bi in co-deposited Cu-Bi products from solutions with low concentrations of Cu (<2 g/L). Bi deposition was significantly suppressed by increasing the Cu(II) concentration in the solution. The formation of a copper layer on the stainless steel electrode appeared to significantly suppress the reduction of Bi(III). This study demonstrates that glue and thiourea depolarize the deposition of bismuth on stainless steel. Therefore, the additives could be used to improve Bi impurity removal during third stage liberation.INTRODUCTIONThe production of high purity copper has been steadily increasing due to the wide application of the metal and its alloys in electrical and electronic products, infrastructure construction, industrial machinery and equipment, general products and transportation (Moskalyk et al., 2003). Most high purity copper is manufactured from copper sulfide mineral concentrates and/or scrap via a pyrometallurgical process followed by electrorefining (Navarro et al., 1999). During the electrorefining process, cast anodes of 99-99.5% purity are electrochemically dissolved into an acidified copper sulfate solution while high purity copper (>99.99%) is plated on stainless steel blanks or copper starter sheets (Davenport et al., 2002). The control of cathode deposit growth (purity and morphology) while maintaining a high current efficiency is of significant importance for copper refining (Ilkhchi et al., 2007). At typically applied current densities for industrial copper electrorefining, mass and charge transfer play important roles in the quality of cathodic products (Hiskey et al., 1998). If the real current density at some surface points is substantially higher owing to uneven current distribution, then rough spots can and will grow faster leading to nodules (Suarez et al., 1992). Nodulated deposits tend to capture solution and anode impurities (slimes) resulting in unacceptable cathode quality (Afifi et al., 1987). Furthermore, these nodules can grow until they eventually contact the anode leading to short circuits and current efficiency reduction (Ilkhchi et al. 2007)."

Jan 1, 2016

By J. M. Tobin, L. H. Cadoff, L. M. Adelsberg

The reaction between liquid zirconium and graphite at temperatures above 2000 °C has been investigated. The reaction products were found to be carbon-saturated zirconium metal and ZrC which formed between the graphite and the metal. Parabolic growth behavior was observed for the ZrC Phase at all temperatures of this investigation. The parabolic growth constant at temperatures between 2000° and 2860°C was measured to be 1.83 exp 84,300/RT) sq cm per sec. The reaclion mechanism was proposed to be the rapid carbon saturation of the liquid metal and the formation of ZrC at the metal-carbide interface with diffusion of carbon through the ZrC, the "rate - determining step" of the reaction. The concentration-independent diffusion coefficient of carbon in ZrC, (DZrC), was expressed as 0.95 exp? 78,700/RT) sq cm per sec. This value mas calculated using the temperature-invariant ZrC phase fields proposed in the literature. The [ZrQiq)] — [ZYQiq) + ZrC] phase boundary over the temperature range 2000° to 2800°C was determined and the ZrC + C eutectic temperature was found to be 2890° ± 50°C. ThE Group IV and VB transition-metal refractory carbides are of interest because of their high melting points, high temperature strength properties, and relative inertness in certain corrosive environments. The present-day understanding of these materials, however, is limited by the general unavailability of accurate and reliable physical and chemical property data. This is due primarily to the difficulties associated with the preparation of suitable, high-density, high-purity carbide samples, and the achievement and control of uniform high-temperature environments. Accurate measurement of temperature is also an important factor limiting the reliability of reported data. The Zr-C reaction was selected for investigation because of the high melting point (>34000C) and favorable nuclear properties of the reaction product, ZrC. The direct reaction method afforded an opportunity to obtain kinetic data on the fully dense carbide. In this paper, layer-growth techniques were used to estimate the diffusivity of carbon in ZrC and to investigate the phase equilibria in the Zr-C system at temperatures above 2000°C. EXPERIMENTAL PROCEDURES AND DATA Crystal bar zirconium (99.9 pct Zr), purchased from the Nuclear Materials and Engineering Corp., and ZTA graphite (99.9+ pct) were used in this study. The analyses of the materials are listed in Table I. A schematic of the high-temperature carburization apparatus is shown in Fig. 1. The sample was a zirconium metal charge in a 1/2 -in.-ID graphite crucible which was capped with a tightly fitting graphite stern. The crucible and stem were designed to closely approximate black-body conditions. The graphite crucible was packed in lampblack (outgassed 1 hr at 2100°C) which provided insulation and thermal stability to the system. The inert atmosphere was maintained by a constant flow of high-purity argon or helium gas. The nozzle-diffuser section on the top flange was sufficient to prevent back-diffusion of air into the system. Chemical analysis of the carburized samples revealed oxygen and nitrogen concentrations of less than 44 and 20 ppm, respectively. The sample was heated by induction with a Westing-house 5 kw-450 kc power source. Temperature was measured with a Milletron two-color pyrometer which was sighted into the crucible by reflection from an overhead front surface mirror. Optical losses due to glass absorption and light reflection at air-glass interfaces were minimized by the employment of the dynamic-gas seal. It was found that no correction was required for the front surface reflector. The pyrometer was calibrated periodically against a U.S. Bureau of Standards tungsten ribbon secondary standard. Temperatures inside the crucible were also calibrated against the Zr-ZrC eutectic (1850°C)1 and the Nb-Nb2C eutectic (2335°C)2,3 temperatures and agreed to within ±10°C of these values. The temperature was controlled by manually adjusting the power input; variations of

Jan 1, 1967

THIS issue is about Chuquicamata and the new sulphide plant. Chuquicamata is moving into a new cycle of productivity; she has begun to give up the sulphide copper which lies deep-seated beneath the oxide ore zones in large but yet unknown quantity. After forty years of production, Chuqui may be likened to a strapping youngster, with adolescence and maturity still ahead. Mining operations are being projected-not for decades -but for generations. Although there are still many years of open-pit mining ahead, planning of future underground mining has been started. The bottom of the orebody is still unknown, but enough work has been done to show that Chuqui is one of the largest known copper orebodies in the world. Until recently, only the oxide ores have been mined and these have been treated at the rate of 50,000 to 60,000 tons per day by leaching. Construction of the sulphide plant was timed to coincide with reduction in production of oxide ores. The new sulphide concentrator and smelter, designed in keeping with the magnitude of the orebody, will be brought on the production line at the rate of 30,000 tons per day. The capacity of the plant now planned can be expanded to treat 60,000 tons of sulphide ore. Little wonder that Chuqui is a name legendary in the remotest mining circles. But to those who have known her more intimately, and there is hardly a mining camp without a Chuqui graduate, she means much more. She is an orebody that has made engineers. Reposing at 10,000 ft on the western flank of the Andes in the arid northern reaches of Chile, water is scarce, common fuels absent, and volcanoes and earthquakes add drama and hazard. It is these natural difficulties which have created the fascination and challenge which have caused many engineers to devote their lives to unlocking this treasure house of nature.

Jan 1, 1952

By Brian Maroney

In this paper an overview of the California Department of Transportation&apos;s (CALTRANS) bridge design criteria is presented. Special emphasis is focused upon seismic design and retrofit criteria. Topics include earthquake load definitions, foundation and structure type selection, structural earthquake analysis, and structure behavioral requirements.

Jan 1, 1993

By Ke Yang

In Chinese coal mines, extraction of deep, highly gassy soft coal seams sandwiched between soft floor and soft roof in complicated geology is commonly encountered. How to safely and efficiently excavate such seams is a very significant and important problem. It has been a focused research area in recent years. By combining the characteristics of fully mechanized longwall mining methods such as large cutting height and mining along the dip, an integrated method and technologies for the Zhangji Coal Mine were developed. This technology includes the design of a complicated geological exploration system, optimization of mining method and working face parameters, control of rock pressure and high levels of gas, reliability model of the production system, and selection and compatibility of equipment. Engineering practice shows that the integrated technology was successful in mining these complicated seams. This study not only enriches the mining method, but also improves the coal mining practice, especially ensuring both safety and productivity under complicated geological conditions.

Jan 1, 2009

By Gordon M. Matheson, Douglas A. Anderson, David K. Miller

"Traditionally, analysis of vibrations from blasting has been focused on peak particle velocity fordetermining the likelihood of both annoyance and damage. The US Bureau of Mines, in RI 8507,indicated the importance of frequency in vibration. Methods of controlling the vibration by reducingthe vibration concentrated in certain frequency bands using delays have been successful over the past decade."

Jan 1, 1997

By T. R. Ellis

The author attempted to concurrently apply the US Uniform Standards of Professional Appraisal Practice (USPAP) and the Australian VALMIN Code to a complex mineral property appraisal assignment and previously to some modest assignments. This led the author into many severe difficulties. These difficulties included the high standards needed in the work of others and information and statements required from the client under the VALMIN Code. The exercises highlighted many positive features of both sets of standards. However, the author concluded that, without modification, VALMIN is incompatible with USPAP and the US regulatory environ¬ment. The author found that VALMIN violates US legal decisions regarding real property appraisal due to its requirement to include many items of business value. The US Securities and Exchange Commission&apos;s prohibition on reporting quantitative resource estimates proved to be a severe problem under VALMIN. Some VALMIN requirements could not be met due to the extent and quality of documents specified. Implications and thoughts regarding the development of a set of US minerals appraisal standards are discussed. Management considerations for complex mineral-property appraisal assignments are also presented.

Jan 1, 2000

By Clifford Frondel

THE aluminum oxide known as corundum has several varieties that have been used as gem materials since ancient times. These include the red variety called ruby, the blue variety sapphire, and the asteriated types of ruby and sapphire. Asteriated sapphire was known to the ancients under the name of astrios, and descriptions of this gem were given by Pliny and other early writers. The relation of these gem materials to each other as varieties of a single species, corundum, was first clearly established by Haüy in 1805 and J. M. Güthe1 in 1809. Natural gem corundum is obtained principally in Ceylon, Siam, Burma, India, and Australia. Star sapphires and rubies always have been highly prized and in recent years have become particularly popular in the United States. Natural star rubies of large size and fine quality are extremely rare and rank with large and fine emeralds and diamonds as the most valuable of gem stones. Interest thus attaches to the recent success in commercially synthesizing star sapphires and rubies of a size and perfection unmatched by nature.

Jan 1, 1954

By M R. Lane, M L. Cramer, N P. Wines

Increasing attention is being focused by regulators and industry on the residual environmental liabilities associated with mining projects following site relinquishment (termed surrender in Queensland). Even sites that have been rehabilitated to a high standard and to the satisfaction of the regulator are not completely risk free and may require some degree of ongoing management. As well as ongoing monitoring and maintenance costs, considerations should include how costs associated with potential risk event occurrence can be quantified and, if considered material, how provisioning should be undertaken to minimise the risk to the state and to taxpayers. In Queensland for example, once a resource site is fully rehabilitated and meets its environmental authority conditions or rehabilitation completion criteria, the tenure and environmental authority can be surrendered. During the surrender process any ‘residual risks’ resulting from the use of the site for the resource activity must be considered, and, if requested, a payment given to the government to cover any ongoing management and risk costs. Accent Environmental, in conjunction with Lane Associates, was engaged by the Queensland Government as part of the government’s financial assurance framework reforms to develop an innovative, ‘one-size fits most’ Residual Risk Calculator for the Queensland resources industry. The calculator is an Excel-based tool that uses detailed user inputs to estimate post-surrender management requirements and liability at resource sites. If residual environmental risks associated with rehabilitated mine sites can be identified, quantified and managed through pragmatic regulatory tools and effective provisioning, site relinquishment/surrender can be achieved without compromising environmental and social outcomes or exposing the state to unreasonable financial risk. The effective management of residual risk can also help facilitate operations as well as relinquishment/surrender of sites where a ‘walkaway’ solution may not be otherwise technically feasible.

Aug 2, 2023

By Michael Bourassa, Sonja Felderhof, Normand Champigny, Steve Vaughan

Introduction -Comparison of International Reporting Standards (Sonja) -Legal and Due Diligence Requirements for Reporting (Steve) -Flexibility to Recognize International Reporting Standards (Michael) -Obligation of SRO’s to Discipline (Michael) -Impact of Sarbanes Oxley on Reporting (Normand)

Jan 1, 2003

By Phillip R. Mulligan, Kevin Gantz, Aaron J. Ward, allen shirley, Sean Treadway

Understanding the impulse transferred into a structure by the coupled two-phase loading produced by an explosive charge buried in soil is of interest for various applications. The most common impulse measurement technique involves a buried explosive charge and a steel plate/test structure suspended above the charge. Upon detonation of the charge, the soil and overpressure heave the plate into the air. The plate’s trajectory and velocity provide the necessary information to calculate the total impulse transferred from the charge configuration.

Jan 1, 2016

By A. B. Cecala

Over the past decade, a substantial effort has been made to improve the air quality inside enclosed cabs of both underground and surface mobile mining equipment to reduce respirable dust exposures to the equipment operators. As part of this effort, the National Institute for Occupational Safety and Health, (NIOSH) completed a comprehensive laboratory study which determined the significant factors for cab filtration and pressurization systems. From this information, a major underground mining equipment manufacturer designed a filtration and pressurization system which was incorporated into the enclosed cabs of its equipment. A long-term evaluation was performed on the effectiveness of this filtration and pressurization system to improve the air quality in the enclosed cabs of two different pieces of equipment, being a face drill and a roof-bolter machine, at an underground limestone mine. This long-term evaluation demonstrated a significant reduction in dust levels comparing outside to inside cab respirable dust concentrations. During this evaluation, a modification to remove one of the filters on the roof-bolter machine simplified the design without sacrificing the system?s efficiency. Testing using particle count instruments performed during non-production time periods on both pieces of equipment indicated Protection Factors greater than 100 when comparing respirable-sized dust particles inside the enclosed cab relative to outside.

Jan 1, 2012

By M. Saba

In cyanide leaching procedure, achieving an acceptable efficiency for silver and gold is very time-consuming, thus, enough studies have not been performed for optimization and modeling of this process. The kinetics of cyanide leaching includes two steps: first step comprises a sharp slope while the other has a slight increasing trend. In the present study, in order to reduce the time and cost, the cyanide leaching process of a sulfide silver/gold ore was optimized in the first period. The applied parameters and their ranges are: temperature 20-40 (°C); time 1-8 (hrs); cyanide concentration 1-2 (mole cyanide / mole Cu); the percentage of solid to liquid 1-2 (%) and pH 10-12. For design of experiments fractional factorial 2(5-1) was used. Also four center points were applied to increase the accuracy of the model. In addition, by analysis of variance (ANOVA) the most effective parameters were identified and the optimized condition was determined. A regression model was proposed to describe the effects of independent variables and their interacting role on silver recovery. Results showed that the model was linear for silver and nonlinear for gold. In the gold recovery process, the two important parameters are time and pH with the former being more effective. Due to the existence of cyanide ions in the medium, temperature and cyanide concentration have less influence in the gold recovery process. Solid to liquid ratio, in addition, comprises a slight negative impact on the procedure. This emphasizes the different kinetics of silver/ gold cyanide leaching. Finally, using the optimum condition the amount of silver and gold obtained were 61% and 67% in 8 hours, respectively. While in general conditions, the results were 37% and 54% in 24 hours, respectively. Keywords: cyanide leaching, refractory gold/silver ore, modeling, optimization

Sep 1, 2012