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By William Petruk

The development of automatic image analysers brought the application of image analysis into process mineralogy because the analysers can measure parameters more easily, quickly and accurately than by manual grain counting techniques, and can also collect data unobtainable by manual grain counting. Data from ore specimens and mill products are used to predict and to define the behaviour of minerals during processing. The analyses are generally performed on the basis of either surface areas or linear intercepts of grains in polished or thin sections, and the data are computer processed to give mineral quantities, liberations, size distributions, and characteristics of middling particles. For analysis, the minerals must be detectable and discriminatable from each other. An image editor is usually used when minerals are not easily discriminated. In addition BSE-8EM photographs have been used where the silicate minerals could not be discriminated from the mounting media. Methods of analysis, typical results, and their applications are discussed.

Jan 1, 1982

By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By Xinhua Wang, Xuefeng Liu, Die Yang, Lifeng Zhang, Wen Yang

"CSP thin slab continuous casters are well used in recent years. The control of heat transfer in the mold is very important because it is correlated with several slab defects. The mean heat flux of CSP mold was studied based on the plant production data of LCAK steel and weathering steel. The effect of various operation conditions on the heat flux was analyzed and discussed. The results showed that the heat flux was 2.1-2.6 MW/m2 on the wide face and 1.2-2.2 MW/m2 on the narrow face for the casting of LCAK steels. During the casting of weathering steel, the heat flus was mostly 2.05-2.5 MW/m2 on the wide face and was 1.1-1.8 MW/m2 on the narrow face. The heat flux depended largely on the casting speed. The heat flux on the wide face increased obviously with increasing casting speed when the casting speed was relatively low; however, at high speed, the heat flux increased slowly or kept constant. At low casting speed, the heat flux depended little on the superheat of the molten steel. The mean heat flux depended little on the level fluctuation at continuous casting mold.IntroductionCSP thin slab continuous casters are used more frequently in recent years for its low cost of construction and manufacturing. The structure of CSP mold is very different from that of conventional thick slab casting mold, inducing the difference of heat flux between them. There have been some studies about the heat flux of thick and medium slab casters [l, 2]. Heat transfer in the mold is very important for the solidification of molten steel because it is correlated with several slab defects such as slab break-out, longitudinal crack, and surface depression. Moreover, higher casting speed is desired to improve the productivity. The control of solidified shell is extremely important. The heat flux is largely influenced by several casting parameters such as the cooling intensity of the mold, the casting speed[3], the mold flux powder [3, 4] and the carbon content of steel as well [5]. The investigation on the heat flux and affecting parameters can help to understand the solidification of molten steel in the mold."

Jan 1, 2013

By C. J. Newman

Prior to 1995, the smelting process at the Kennecott Utah Copper Corporation (KUCC) smelter consisted of Noranda reactors and Pierce-Smith converters. In the consideration of expansion opportunities, the existing process did not lend itself to a program geared towards processing the total output of KUCC mining and milling operations. During 1989 and 1990, a number of smelting options were evaluated. The final selection was the Outokumpu flash smelting process, coupled with the new Kennecott-Outokumpu flash converting technology. Facilities were designed and installed to process 1:0 million tonnes per year of copper concentrate, with the ability to expand to 1.2 million tonnes per year. Following the shutdown of the smelter facility utilizing the Noranda technology in May 1995, the flash smelting, furnace commenced operation in June with the flash converting furnace startup following a few weeks later. The smelter has achieved design production targets and environmental goals. Current operating rates are at or above design rates for concentrate and matte processing. Emissions are lower than the permit levels and equate to less than 3.5 kg of SO2 per tonne of copper. This paper outlines the design, construction, startup and the first two years of operation of the modernized KUCC smelter.

Jan 1, 1998

By James M. Fragomeni

"The mechanical behavior of an Al-Li alloy was studied and related to the extrusion processing parameters, the plastic metal flow during defonnation, the anisotropy, and the microstructure. The extrusion temperatures, strain rates, extrusion ratios, billet temperatures, and extrusion geometries were varied during processing and correlated with the microstructure and properties. The extrusion processing variables were related to the mechariicar behavior, anisotropy, and microstructure through the ZenerHollomon parameter i.e., the temperature compensated strain rate. Based on optical and electron microscopy studies it was found that regardless of the extrusion conditions, the various microstructures for the most part were unrecrystallized for both the as-extruded and the solution heat-treated conditions. Smaller grain sizes were correlated to larger Zener-Hollomon parameters. The extrusion temperature and ratio did not significantly affect the strength or ductility as did the section geometry, which had a large affect on these mechanical properties. The anisotropy of the properties varied substantially when comparing the extruded longitudinal versus transverse grain orientations.IntroductionThe extrusion process also has a substantial influence on: the microsfructure and mechanical properties of a material that is Athens, Ohio, 45701 fonned The plastic defonnation that occurs during the extrusion process alters the grain size, crystallographic texture, anisotropy, subgrain size, dislocation density and various other microstructural features. Often the material being extruded is not homogeneous, therefore variations in the microstructure and properties occur across the cross-section of the final extruded product. The mechanical properties and microstructure can also vary with length since it is hard to maintain a constant temperature throughout the extrusion process. The extrusion temperature often varies from the heat generated during the extrusion process. The demonstration material that was extruded for this .study was an aluminum alloy containing 2.6wt, % lithium and 0.09wt.% zirconium. This alloy was strengthened by heat treatment causing nucleation, growth, and coarsening of coherent metastable o' (Al3Li) precipitates in the microstructure. The ? precipitates which are a consequence 9f artificially aging the AlLi alloy, are spherical, ordered, and coherent with the aluminum matrix and impede the dislocation glide inotion during plastic defonnation. Theo particles grow homogeneously in the matrix, and have the Cu3Au (L 12)"" superlattice crystal structure. Aluminum-lithium alloys are used primarily for aerospace structural applications since they have attractive properties such as a lower density and higher elastic modulus than conventional 2XXX and 7XXX alloys."

Jan 1, 2000

By P. N. Anyalebechi

"The effects of solidification rate, initial melt hydrogen concentration, and grain refining on porosity formation in aluminum alloy 2024 have been investigated with unidirectionally cooled laboratory-size ingots. The ingots were prepared from melts containing hydrogen concentration of 0.059-0.27 cm3/100 g and solidified at 0.2-37 °C/s. As expected, the amount of porosity, average pore size, and pore number density increased with increase in melt hydrogen concentration and decrease in solidification rate. However, the effect of solidification rate was greater at the very low melt hydrogen concentration (0.059 cm3/100 g). These results are consistent with reported effects of solidification rate and melt hydrogen content on porosity formation in other aluminum alloys. Interestingly, addition of grain refiner slightly increased the amount of porosity and the average pore size, especially at solidification rates above 1°C/s. IntroductionIn shaped castings and wrought products fabricated from ingots, billets, bars, or slabs of aluminum and its alloys porosity formation is a problem. This is because it compromises their tensile strength, fracture toughness, and fatigue properties [ 1-18]. The pores are usually the crack initiation and propagation sites [6,8,9] and the largest pores tend to dictate the fatigue life of the aluminum products [9,10,14]. Porous regions within an aluminum product probably yield first due to the reduced tensile load bearing capacity, causing the concentration of the strain near the voids which subsequently results in premature fracture. In aluminum alloy ingots, billets, bars and slabs porosity formation is particularly problematic because of its persistence through fabrication and potential for reappearance or exacerbation during subsequent thermal treatment processes before and/or after fabrication [19]. In fact, persistence of microporosity is a serious problem in large thick plates of wrought aluminum alloy products that must be rolled from correspondingly large direct-chill or electromagnetic cast ingots. Some of these thick plate products are machined into large aircraft components that are required in service to withstand multi-directional stresses and to possess high fatigue strength, fracture toughness, resistance to stress corrosion cracking, and strength in the short-transverse direction [1,20]."

Jan 1, 2011

By Jinrong Zhang

Major components of soil were tested for their ability to attenuate cyanide. Feldspar, kaolinite, plagioclase and bauxite are found to degrade cyanide at an appreciable amount mainly through adsorption. A soil near a mining site in northern Nevada was studied in detail using a tall column. Many species of cyanide were anlyzed to determine the mechanisms of the reactions of cyanide with soil. Volatilization, adsorption, oxidation, precipitation and complexing were quantitatively identified, being 5 to 10, 11.7, 4.2, 7.3 and 4 per cent of the total cyanide added, respectively. It is found that the oxidation of cyanide to cyanate is due to the catalytic effect of nickel and copper leached from the soil. Precipitation of metal-cyanide complexes occurred at low pH values.

Jan 1, 1991

By M. C. Flemings, S. B. Brown

"Metallurgy, as all of material science and engineering, rests on the intellectual foundations of processing-structure-property-performance relationships. Today it is widely recognized that processing has been too long neglected and presents exciting opportunities for exploitation. New processes, many of them already in the laboratory, will be exploited in the year 2000 and beyond, for near net shape forming and for achieving-new metallurgical structures and composite structures. Process modelling will alter the way we think about process and product design. Processes themselves will increasingly be automated and controlled by computers, altering the nature of the workplace and the tasks of the metallurgical engineer of the future. IntroductionInnovations in metal processing is hardly a new phenomenon, with the field thousands of years old. Nonetheless, the next few decades offer particularly important opportunities to improve our ability to process these materials. We appreciate today the variety of processing paths available to us, including vapor-, plasma- and electro-deposition, multiple phase and casting technologies, and non-equilibrium processes, and how these affect structure at the atomic level and at higher levels of aggregation. We understand the basic physical mechanisms involved far better than even before and have remarkable new abilities to predict, control, and simulate the kinetics underlying processes, and the processes themselves.The following sections describe these new opportunities in greater detail. First, we examine developments in the modelling of metal processing. We then consider some implications associated with process control and automation. Finally we present what we consider to be particularly promising metal processing technologies, and conclude with a few summary comments."

Jan 1, 1988

By Simon N. Lekakh, D. G. C. Robertson

A new integrated CFD-combined reactors approach is proposed for the description of processes in metallurgical vessels. CFD simulations were used to obtain the melt flow pattern in the vessels (ladle, tundish, and continuous caster mold). From these simulations, the characteristic curves were derived: (i) the residence time distribution curves (RTD) for flow-through systems (at tundish exit or at dendrite coherency surface in the mold) and (ii) the mixing curves for closed systems (ladle). In the next step, the melt flow was represented in a “combined reactors” system consisting of a combination of unit reactors (Plug Flow, Mixer, and Recirculated Volume). An inverse simulation was used to define the volumes of the reactor units and the melt flow rates between them by fitting to the characteristic curves from both methods (CFD and combined reactors). The suggested approach is demonstrated for multiple designs of Ar-stirred ladles, tundish, and SEN. This methodology can be used to enhance traditional post-processing CFD analysis and also as a tool for on-line process control.

Jan 1, 2014

By J. B. W. Bailey

The Noranda Horne smelter in Quebec, Canada has change considerably during the last two decades to accommodate varying custom concentrate receipts, closure of the Horne mine, better working conditions, environmental programmes, new technology and increased energy and labour costs. This paper highlights the reasons for changing the smelter from two calcine charged and one wet charge reverberatory furnaces fired by coal to a smelter using. tonnage oxygen oil, natural gas and coal in a single wet charged reverberatory furnace and a Noranda Process continuous Reactor. The current operation 1 described, including three major topics; the use of oxygen/fuel burners on the charge banks of the reverberatory furnace which has increase the smelting rate from 680 to 1100 tonnes of concentrate per day; the oxygen enrichment of the Noranda Process converting air to achieve smelting rates of over 1800 tonnes of concentrate per day; the converting of the mixture of 73 percent copper matte produced from the Noranda Process and the 33 percent copper matte produced from the reverberatory furnace.

Jan 1, 1983

By O. Norman Lotter

There are many scales of innovation in the pursuit of concentrator performance improvement, including paradigm change, inventive change and incremental change. All are important, but the last is low risk, low cost and has a relatively high probability of success, given the right metallurgical skills. Seeking continuous improvement is also essential to ensure that performance does not decline over time due to ore type changes, personnel changes, equipment wear and other factors. When properly implemented, these small gains offer a very high rate of return for the project cost because they are made from marginal, not total, operating costs of the plant. To be effective this approach requires plant trials that use designed structure and appropriate statistics to test the observed differences arising from the old and new process treatments, be they a change in flotation reagent, in grind, pulp density, etc. However the pursuit of small but financially significant performance gains is often regarded as fruitless because of the range of variance in plant data, and the consequent difficulty of ‘proving’ that a benefit has been achieved. Opportunity for improvement is thus sometimes relegated to the realm of the impossible, or at best, treated with skepticism. Operations managers prefer to look for the larger gains, which are easier to demonstrate and prove. Unfortunately, these are seldom to be found; rather, a large gain can be more easily made by executing a series of small recovery improvements that are together equivalent to the ephemeral single large gain. In this paper we advocate a policy of continuing improvement driven by rigorous performance testing protocols and a formal ‘risk analysis’ approach to judging the efficacy of changes implemented in the plant. Following these simple procedures allows rational decisions to be made on the basis of quantifying risk and reward. In particular we consider the choice of hurdle rate for decision-making which best balances risk and reward. It is shown through case studies from actual industrial practice that this approach is practical and delivers significant financial value to the operation.

By Samuel Senanu, Benjamin Agyei-Tuffour, Lifeng Zhang, Eivind Øvrelid, Adegboyega Nathaniel Femi

"The solar grade silicon ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. The hard inclusions lead to wire breakages during the cutting of the ingot in wafers. The main kinds of inclusions found in solar grade silicon have been investigated using vacuum filtration: needle-like Si3N4 and lumpy SiC inclusions. Clusters of SiC inclusions and Si3N4 are also found. Surface observations of the scraps before polishing reveals that Si3N4 inclusions are usually bigger and in some cases can be about a few millimeters. SiC inclusions are usually smaller, ~200µm but can be ~500µm in some cases. Inclusions observed after filtration are mainly SiC with diameters ~10µm. Through the vacuum filtration, 99% inclusions can be removed 99%. The possible mechanisms of filtration are cake filtration for the larger sized Si3N4 and SiC inclusions and deep-bed filtration the SiC inclusions. For the directional solidified silicon ingot, an approximate distance of ~10mm gave an encouraging cutoff thickness. The inclusions sizes were below 10µm. Introduction The search for an alternative source of energy to fossil fuel has led to a dramatic increase in the demand for solar energy due to its high dependability (abundant in nature) and environmental friendliness 1). During the last 5 to 10 years, the annual worldwide production of solar cell by the photovoltaic industry has increased to an annual rate of 30 to 40 percent 2). A necessary condition for the maintenance and even an increase of this growth rate is a decrease in the cost of feedstock for the solar cell production 1). The total international production in 1997 was 130 MW worth more than $500 million. In 2004 the consolidated world total production of PV cells increased to 1146 MW or around. $7 billion (Figure 1) 3). Silicon is currently the most dominant semiconductor material used in the PV industry. As shown in Figure 2 3), solar cells consist of two types of material, often the p-type and n-type silicon. Light of certain wavelengths are able to ionize the atoms in the silicon (causing atoms to either gain or lose electrons) and the internal field produced by the junction separates some of the positive charges (“holes”) from the negative charges (electrons) within the photovoltaic device. The holes are swept into the positive or p-layer and the electrons are swept into the negative or n-layer. Although these opposite charges are attracted to each other, most of them can only recombine by passing through an external circuit outside the material because of the internal potential energy barrier. Therefore if a circuit is made, power can be produced from the cells under light because the free electrons pass through the load to recombine with the positive holes."

Jan 1, 2008

By Minh H. Pham

This paper presents a technique for imaging the extent of solidification of molten metal flowing in a cooled pipe based on the concept of eddy currents. A 3D mathematical model, which relates the geometry of solidification to the scattered field induced in a solenoid external to the pipe, is derived. The model is described by a set of integral equations which are solved numerically using the moments method. An iterative algorithm is developed to reconstruct the solidification distribution image. Experimental measurements have shown that the eddy current technique is sufficiently sensitive for practical purposes.

Jan 1, 2001

By Jiang Diao, Xuan Liu, Tao Zhang, Bing Xie

In the present study, the oxidation process of vanadium and chromium bearing hot metal was investigated by using CaO-FetO-SiO2 slags at 1653K in MoSi2 furnace. The results indicated that both the vanadium distribution LV and chromium distribution LCr were of the orders of 2.2~2.4 with the basicity range of 1.32~1.78 and FeO weight percent range of 28%~45%. Both LV and LCr decreased with increasing basicity and decreasing FeO weight percent. The phosphorus distribution LP was of the order of 1.34~1.56. However, LP increased with increasing basicity and decreasing FeO weight percent. The oxidation ratio values of V and Cr in hot metal were above 84% and the values of P were nearly 50%. In other words, it means the addition of CaO in vanadium slag provided a certain ability of dephosphorization along with keeping high oxidation ratios of V and Cr.

Jan 1, 2015

By Xie Zhang, Jiang Diao, Xiaojun Li, Bing Xie

"Vanadium is widely utilized as an important element to improve the quality of alloyed steels in iron and steel industry. Moreover, the crystallization process of V-containing spinels plays a significant role due to the aim of achieving a fairly larger size of spinel crystals in vanadium extraction. Thus, a comprehensive exploration and discussion on the competitive precipitation and growth of vanadium, chromium and titanium spinel crystals in vanadium slag during a cooling process were carried out in the present study on the basis of a crystallization kinetic model. To be more specific, the abilities of forming crystal, precipitation order and suitable temperature range for crystallization of the three kinds of spinels were discussed with both theoretical and experimental methods.IntroductionVanadium is an important element which is used almost exclusively in ferrous and non-ferrous alloys due to its excellent physical properties such as high tensile strength, hardness, and fatigue resistance [1]. Various kinds of processes of vanadium extraction from V-containing hot metal are available at present. However, only four processes which are the Highveld process (South Africa), the Pan-steel process (China), the NTMK duplex process (Russia) and the New Zealand steel process (New Zealand) take the dominant positions [2, 3]. Although the type of reactor and the initial vanadium content in hot metal are different in these techniques, they share the same principle that vanadium is oxidized by oxygen into vanadium slag."

Jan 1, 2012

By Wang Chen

COREX process is briefly introduced. A static model combining a set of mass and heat balance equations has been developed. Taking the specified inputs from the graphical user interfaces, the model is capable of calculating the consumption of raw materials and fluxes, the volume and composition of the slag and the volume and composition of the generator gas. The model enables the examination of the changes of materials and energy flows induced by the variations of operational parameters and raw materials chemical analysis. The model allows a detailed process analysis and adjustment of the plant operation and can thus be used to improve plant operation.

Jan 1, 2008

By F. H. (Sam) Froes, C. Suryanarayana, K. C. Russell, C. M. Ward-Close

"Far from equilibrium synthesis allows development of novel crystal structures and microstructures, leading to achievement of enhanced physical and mechanical properties. A number of ""far from equilibrium"" techniques are reviewed with emphasis on the amount of departure from equilibrium. The ability of two such techniques, mechanical alloying (MAl, and physical vapor deposition (PVD) to develop novel structures are discussed in detail. For the MA process emphasis is placed on intermetallic compound compositions. Solubility extension, beyond rapid solidification (RS) levels, is found in terminal compositions but not for the intermetallics. Nanostructure-sized grains (< 100nm) form which can be retained after ""low temperature"" compaction. On continued milling in many cases the nanometer-sized grains transform to an amorphous structure. Ordering is destroyed by MA, except in those intermetallics with large negative enthalpies of formation. For the PVD process, a review of application to terminal light alloy compositions is presented. This includes a new high-temperature aluminum alloy, layered materials with nanometer spacing, corrosion-resistant magnesium alloys and low-density titanium compositions. IntroductionTo enhance the mechanical property combinations of advanced structural materials innovations in process/synthesis are required [1-6]. In this paper the capability of various ""far from equilibrium"" synthesis techniques [7,8] to produce novel constitutional and microstructural effects, and hence potentially enhanced physical and mechanical properties, in advanced materials is presented. The application of two such methods, mechanical alloying (MA) and physical vapor deposition (PVD) is discussed in detail. For the MA process emphasis is on intermetallic compositions with consideration given to solid solubility extension, microstructural refinement, amorphization, and formation of intermetallic compounds. For the PVD process application to terminal light alloy compositions is discussed."

Jan 1, 1994

By Rudolf Keller

"EMEC Consultants is developing a process to extract oxygen, aluminum and silicon from lunar anorthositic soil. The process will provide oxygen in space for propulsion, aluminum as a structural material, and possibly silicon for the construction of solar cells.The evolution of the process concept in the course of our present NASA-sponsored SBIR effort is discussed. A molten salt electrolysis producing aluminum and oxygen is the central step; inert anode technology is to be employed. Silicon will be produced by reducing the anorthite, CaAI2Si20S' with aluminum. In a steady-state operation, all components of the ore added have to be removed from the process, and the removal of calcium is a major topic of our experimental studies.Utilization of Lunar ResourcesUtilization of lunar resources may play an essential role in the exploration of the solar system and the conquest of space. High costs are involved in overcoming Earth's gravity to supply missions in space. Even at a low projected cost of $ 300 for transporting a pound of payload into Earth orbit -- today's costs are many times higher -- it appears attractive to use resources in space to produce needed materials. Processing of lunar resources on the lunar surface is an obvious possibility.Oxygen is a product of major interest. It is required for support of human life in space. Even greater quantities may be needed for propulsion, to conduct further missions into space. To satisfy this demand for oxygen through lunar processing requires a quite different solution than to supply oxygen on Earth, where oxygen gas is abundant and easy to extract from air or water. On the lunar surface, solid oxide materials have to be used. Hydrogen reduction of ilmenite and subsequent electrolysis of the resulting water is being studied [1]. Other suggestions include fluorination of lunar soil [2], reduction with lithium and electrolytic decomposition of the resulting lithium oxide [3], and aqueous HF leaching [4]."

Jan 1, 1988

By Shu Xinqian, Zhou Weining, Shan Zhiqiang, Feng Jifu

"Modified calcination conditions on the extraction of rubidium resources from muscovite (KAlz[AlSi301o](OH)2) ore are systematically studied. The impact of various factors on the rubidium leaching rate is also analyzed, including the agent types, roasting time, the mass ratio, roasting temperature, etc. The results indicate that the best agent is a combination of sodium chloride and calcium chloride, its mass ratio ofmuscovite/NaCl/CaClz is 1:0.25:0.25. Calcined at 8500 for 30 minutes, the rubidium leaching rate is up to 90%. The reaction of muscovite ore with the chlorinating agent CaC12 has been studied by TG/DSC, the calcined intermediates are identified by XRD, and the surface morphology before and after leaching is characterized by SEM. Rubidium chloride products can be obtained with a purity of 92% by using t-BAMBP extraction, hydrochloric acid reextraction and purification.IntroductionRubidium is one ofrare alkali metals, which is found in 1981 by German R.W. Bunsen and G.R. Kirchhof. Rubidium includes the following features: atomic number is 37, each atom weight 85, the body-centred cubic lattice, each unit cell has two metal atoms, and the density is 1.532g/cm3. The properties of low melting point (312.46 K) and malleability make rubidium have a strong chemical activity and photoemission. Rubidium provides a main material for manufacturing phototube with a wide range oflight waves, which possess high sensitivity and stability. Efforts are being made to carry out research on rubidium ion gngine, magnetic flux generators and thermoelectric transudcer, etc. Rubidium exists in muscovite ore(KA12[AlSh01o](OH)2 (monoclinic system and hexagonal layered structure) as isomorphism and replace the large radius of the potassium atoms, as well as part of rubidium locate between structure layers. The complex components bring great difficulty in comprehensive recycling."

Jan 1, 2013

By Rina Kim

The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of lead salt in the low overpotential region (–0.35 V vs. Ag/AgCl). The similar behavior was observed in the presence of ore containing 0.25% galena. In contrast, the gold oxidation kinetics retarded at –0.35 V (vs. Ag/AgCl) in the presence of silicate and lead-bearing mineral under certain conditions. Likewise, the lead addition was not functional for the high sulfur ore. This was attributed to the oxidation of the sulfides to the elemental sulfur, which subsequently formed a passivating layer on the gold surface. The results were evidently affirmed by the electrochemical tests and X-ray photoelectron spectroscopy (XPS) analysis.