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By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting, lime roasting, is being tested fro retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04), oldhamite (CaS), calcium sulfite (CaS03), hematite (FenOs), magnetite (Fe304), and minor amoupts of pyrrhotite (Fel.,S) and pyrite. At 600°C, 650°C and 700°C the main constituents are anhydrite, oldhamite, and hematite. At 750°C, 800°C, and 850°C anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides, calcium sulfite, hematite, and minor oldhamite, magnetite, and pyrrhotite. At 650°C 700°C 750°C and 800°C, anhydrite, oldhamite, arsenic sulfides, and hematite are present. At 850°C, the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CLM) in the determination of the calcium-sulfur- oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RLM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1993

By Sue Ritz

Gold extraction has relied on coconut carbon in adsorption circuits for several decades. IXOS®, invented by 6th Wave Innovations of Salt Lake City, Utah, is a new type of adsorbent that exceeds the selectivity of carbon and improves on the mechanical properties of other available resins. IXOS selectivity against copper cyanide complexes allows it to be used in circuits that currently struggle with copper contamination. IXOS potential to eliminate or reduce the application of SART technology will expand the opportunities to exploit more complex precious metals deposits. This paper will describe the technology behind IXOS molecular imprint, its comparison to carbon adsorption in the field, and the effect of efficiency on long-term recovery from heap leach METSIM simulation software.

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

By I. Gaballah

Cadmium is toxic to plant, animals and humans. The council directive of the European Communities No 8315 13lEEC has fixed an upper limit of 200 ppb for the release of cadmium in industrial effluents. The conventional method of neutralization/prccipitation ( NIP ) is inefficient to reach this limit. The objective of this study is to test the efficiency of the trees modified bark to remove cadmium cations from industrial effluents after the conventional treatment by NIP. Laboratory scale tests with synthetic solutions show that the cadmium removal depends upon pH and initial concentration. About 99.9 %, 99 % and 96 % of the metal are removed from synthetic solutions containing 10, 100 and 1000 ppm respectively. Pilot plant trials ( 1 m3 ) with an industrial effluent bearing about 500 ppb of cadmium lead to the almost complete elimination of the cadmium ( final concentration is lower than the analytical detection limits < 20 ppb ).

Jan 1, 1994

By Patrik Fredriksson

Thermodynamic data concerning FeO-containing slags is of importance in ladle refining of steel. With a view to generate a set of reliable and self-consistent thermodynamic data for these slags, experimental determination of the activities of FeO in binary and ternary slags was carried out using the gas equilibration method involving CO-C02-Ar gas mixtures at steelmaking temperatures. The slag samples in Pt crucibles were quenched after the equilibration and subjected to chemical analysis. The thermodynamic activities of "FeO" in the slags were calculated from the experimental data. The results are incorporated into a thermodynamic description of silicate melts in the present laboratory. The model is based on a Temkin-Lumsden approach and is able to compute the thermodynamics of higher order systems from the lower order ones.

Jan 1, 2003

By Markus A. Reuter, Robert Matusewicz

"Consumer products are a complex man-made mixture of sometimes in excess of 50 elements. In order to recover these complex mixtures of elements either as metals, compounds or energy requires versatile technology in physical separation but also smelting and energy recovery. This paper explores this by referring to the innovative application of Top Submerged Lance (TSL) technology and associated theoretical and environmental aspects to process (recycle) post consumer materials and industrial intermediate products and residues. A diversity of applications has been tested in Ausmelt’s pilot plant in Dandenong and many have gone to commercial scale globally. This paper reviews the varied applications ranging from e-waste recycling, lead and NiCd battery recycling, metals recovery from slags, zinc leach residue processing, electric arc furnace (EAF) dust, Municipal Waste Incinerator bottom ash processing, carbon containing residues such as retort ashes and spent pot liner from the aluminium production process as well as use of the technology for materials such as automotive shredder residue (ASR) and plastics. Introduction The modern resource cycle is a link between primary production of metals linked to the recycling of post-consumer goods. The sometimes complex combinations of materials and metals in consumer products such as televisions depicted by Figure 1, does require a range of technology to recover materials, metals and energy for reuse and/or recycling in an economically feasible as well as environmentally friendly manner."

Jan 1, 2008

By Susan Jacob

The heat of fusion of silver was measured using high temperature differential scanning calorimetry (HTDSC). Heating rate, sample mass, calibration standard and cover gas flow rate were varied to determine their impact on instrument accuracy and reproducibility. Good reproducibility was achieved in most of the runs. Accuracy was not satisfactory in most of the runs, though three runs gave results within 1.7%, 3.3% and 3.5% of the literature value, within the acceptable limits. A larger mass and higher heating rate tend to generate more accurate results.

Jan 1, 2006

By N. El-Kaddah, A. D. Patel, T. T. Natarajan

The phenomenon of particle migration in a conducting fluid under an applied electromagnetic force field finds its application in selective sorting of minerals and more recently in the removal of inclusion from molten metal. This paper deals with the analysis of the expulsion force and the flow around a spherical particle in crossed uniform electric and magnetic fields in .infinite and in confined medium. Analytical solutions will be presented for the electrk and magnetic fields as well as the induced flow at the limit of zero Hartmann number. The flow around the particle was investigated numerically at low and high values of Hartmann number. It will be shown the magnetic field has almost no effect on the velocity field when Hartmann number is less than 1.0. At higher Hartmann numbers the damping effect of the magnetic field was pronounced in the direction of the applied current. It is concluded that Hartmann number has little effect on the net force on the sphere particle.

Jan 1, 1999

By Wenzhou Yu, Cong Zhang, Wenhui Ma, Gang Wang, Kuixian Wei

"A novel technique was successfully developed for nickel further purification by vacuum directional solidification. The removal effect of impurities in nickel was studied based on theoretical analysis and experiments. High removal efficiency of impurities in nickel can be realized according to theoretical analysis. The experimental results show that the vacuum directional solidification treatment could increase the nickel purity from 99.96% to 99.996%. Since vacuum directional solidification could effectively remove the impurities from nickel with low contamination and low cost, it is a potential route to obtain high-purity nickel for commercial application.IntroductionNickel is widely used in metallurgy, machinery, petroleum industry, chemical industry, construction industry, light industry, and other industries for its ductility, medium hardness, ferromagnetism and high chemical activity. Nickel-based alloy is an important material for the key parts of aircraft, tanks, submarines, radars, nuclear reactors and aerospace fields [1-5]. Generally, nickel contains Si, P, S, Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Al, Mn, Mg and other impurity elements, which may hinder the commercial application of nickel. Therefore, it is necessary to refine the crude nickel for the high purity nickel."

Jan 1, 2014

By Y. Ikeda

Typical electric appliances were dismantled into component pieces to study the recyclability of these discarded goods. Types and weight ratios of these component materials were investigated and characterized. The results showed that if they are dismantled properly, these goods could be classified into several groups of similar materials and/or structures, namely those consisting of single materials, metal-plastic combinations, metal-metal combinations and complex combinations of many different materials. By separating each combination into recyclable materials and isolating hazardous materials, it was found that the final waste for disposal could be reduced and the recycling efficiency could be improved markedly as compared to the conventional shredding method. The metal-metal combinations account for 60% by weight of the total metal contents in electric appliances, and therefore, it becomes important to segregate these metals. For the complex combinations, a process consisting of pyrolytic decomposition of plastic contaminants followed by smelting of the residue is proposed. It is anticipated that nearly zero-emission recycling of electric appliances will be achieved by applying this treatment process.

Jan 1, 1995

By Jeong-Soo Sohn

Physical treatment and chemical treatment of spent lithium-ion battery were studied in our research team. Especially we developed two types of acidic leaching for crushed powders containing LiCoO2 of spent lithium ion battery. One of them is sulfuric acid leaching with H2O2 as a reducing agent. The leaching rates of cobalt, lithium and the other metals were above 99 % at the condition of 2 M H2SO4, 10 vol. % H2O2, 75 °C, 300 rpm agitation speed, 250 g/5L solid liquid ratio and 75 minutes reaction time. And the other leaching process is the oxalic acid leaching. In this process more than 99% of Li and less than 1% of Co were dissolved at the condition of 3M oxalic acid, 80°C reaction temperature, 300rpm agitation speed, 50g/L initial solid/liquid ratio and 90min extraction time. Each process has its advantage and disadvantage. In sulfuric acid leaching, leaching reagent is very cheap and cobalt could be recovered into cobalt hydroxide. On the other hand, oxalic acid is more expensive than sulfuric acid but lithium could be dissolved selectively. Also cobalt could be recovered into cobalt oxalate and it could be changed into cobalt oxide after heat treatment. In order to select the effective recycling process, recovery rate and purity of cobalt hydroxide and cobalt oxalate were compared and it was investigated which process was more environment-friendly and economical.

Jan 1, 2006

By W. D. Keller

Scanning electron microscopy (SEM) accompanied by X-ray energy dispersive analysis (XES) is a useful tool in process clay mineralogy. The texture of kaolin, illustrated by SEM, gives a clue to its mode of genesis and probable industrial application. One type of kaolin, originating dominantly by weathering, has an open texture, slakes readily, and is used for filling and coating paper. Another type, in contrast, originates by diagenesis of Al-silicate sediments, and spectacularly resists slaking, thereby enabling it to maintain its bulk density and controlled size and shape of particles after crushing and moistening; this meets an important requirement for the manufacture of refractories. Ratios of elemental Al:Si that may be rapidly determined by SEM and XES yield information on the origin and purity of bauxite and bauxitic clays, and aid in quality control and processing of them. SEM of dissimilar textures of quartz, as in chert and novaculite, are evidence for geothermometry on a stratigraphic scale that is potentially useful in delimiting thermally favorable or unfavorable areas for hydrocarbon exploration, and possibly for unexposed metallic ore deposits.

Jan 1, 1982

By G. P. Chaudhari, F. Warchomicka, M. Dikovits, V. Pancholi, C. Poletti

"The hot formability of a microalloyed steel with 0.16 wt-%C modified with N is studied by using processing maps. Compression tests of cylindrical samples are carried out using a Gleeble®3800 simulator in the range of temperature between 750 -1000°C and strain rates between 0.01-100 S-1. For this alloy, an Ar3-temperature about 740°C is determined by means of dilatometry. Processing maps are calculated using the modified dynamic material model developed by Murty and Rao for different logarithmic strains. For the instability map, the parameter Kj developed by the authors in previous works is used and compared with other instability values. Softening in the flow curves provoked by induced ferrite during deformation at low temperatures and low strain rates is reflected in the n-value. Light optical microscopy (LOM) and electron back scattered diffraction (EBSD) measurements are used to study the microstructure of the hot deformed samples to determine the deformation mechanisms active and to verify the processing maps.IntroductionProcessing maps offer a good possibility to optimize thermomechanical process parameters and to avoid defects in the products. Prasad et al. [1] developed the processing maps using the dynamic material model (DMM) and Murty & Rao [2] modified it. Processing maps consist of two superimposed maps: the dissipation efficiency and the instability map. The processing maps can be used to detect areas with a good hot formability, which are normally related to restoration of the material by dynamic recovery/recrystallization. For a high dissipation efficiency value and no instabilities, a good hot formability is predicted. In the DMM no storage of energy takes place and so the material is considered essentially dissipative, this is only true for high temperatures and high strain rates [1]."

Jan 1, 2012

By J. M. Demarthe

MINEMET RECHERCHE (IMETAL Group, formerly Le Nickel-Penarroya-Mokta) has studied on a laboratory scale and patented a new process to recover metal values -copper- from sulphide ores and concentrates. It combines a cupric leaching, solvent extraction and copper sulphate electrowinning according to the main following steps - A direct and selective leaching of copper sulphide ores or concentrates at atmospheric pressure with cupric chloride to form cuprous and ferrous chlorides and elemental sulphur. Pyrite remains in the sulphur residue. - The leach solution is separated into two parts -In the first one, air is injected to precipitate iron as goethite. The oxidation step can be easily realized at atmospheric pressure by maintaining an excess of cuprous and-ferrous chlorides in the liquor. Copper is extracted from the second part as cupric ion by an LIX reagent. Direct injection or air in the mixing chamber maintains good extraction conditions, so that only one mixer settler is required. - Iron, in the form of ferrous ion, is not coextracted. - Copper is stripped from the organic phase, transferred into a sulfuric phase and sent to sulphate electrowinning cells, which are now conventional in copper metallurgy. - Only electricity and air are required. After a feasibility study, the next step will be to develop it on a pilot and commercial scale.

Jan 1, 1976

By B. P. Sereda

The properties, characteristics and phase structure of chamotte refractories produced with the usage of mullitecorund chamotte and caoline have been given. The comparison of new refractory C-45 obtained by us and refractory C-43 produced by traditional method has done. The physical-chemical properties of refractories is reviewed. The visual porosity, density and pore characteristics of given refractories was calculated. It is established that C-45 has the less gas permeability then C-45 that gives melting units more stability. The petrographical microstructures of refractories have been done. The main phase structures and their influence on refractories properties have been observed. It is established that refractories with mullitecorund chamotte adition has more advantages then refractories gained by traditional method and can be applied to melting units.

Jan 1, 2010

By Baptiste Laubie

Agromining is a phytotechnology aiming at producing commercial metal compounds from low-grade ores thanks to hyperaccumulating plants. The fern Dichranopteris dichotoma is a rare earth element (REE) hyperaccumulator, which naturally grows on former mine tailings in China. It accumulates up to 0.35% of REEs in its aerial parts. Different hydrometallurgical processes are currently developed to recover these elements directly from the biomass or from ashes after combustion. The process presented here consists of a direct extraction by EDTA solution, followed by precipitation with acid oxalic. Optimal precipitation pH and influence of organic matter are determined by modelling and by experimental studies. The final solid contains 4.3% of REEs, with calcium as the main cationic impurity (0.45% of the precipitate). The recovery yield is similar for major REEs and is around 70%. After optimization, upscaling of the process will allow the agromining development to recover REEs from secondary resources with more environmentally friendly techniques.

By Jingbo Liu, Zhimin Wang, Wenchao Li

"IntroductionThe advantages of non-stoichiometric perovskite material are highlighted in many papers[l]and many of this family of materials are well-suited to integration into microsensor devices. Among them, barium titanate is the most promising due to it's piezoelectric, pyroelectric, dielectric properties. Through modification, BaTiO3-based materials can be utilized in many kinds fields, such as surface wave probe; pholoconducting devices, field-effect transistor, permanent memory permanent storage, and ultrasonic transducerl2-3l. In this Paper, a series of BaTiO3-based polycrystals were synthesized by sol-gel processing which appears to be a very promising method for the manufacture of ceramic, because it offers significant advantages such as high purity, chemical homogeneity, controlled particle sizes of ceramics, and lower processing temperatures [4]. In a sol-gel process, alkoxides of the constituent elements show different reactivity toward water so that the preparation of multi-component homogenous system is difficult. In the experiment, inorganic salt was substituted for some of the alkoxides. Acetic acid which is employed for the solvent and catalyst, acts as donor ligand to titanium alkoxide and controls, the hydrolysis polycondensation reaction. Taking these aspects into consideration, we select the system Ba(OAc)2, , La(OAc)3, Ti(O11Bu)4 and acetic acid which is used as both solvent and homogeneous catalyst for the first time.ExperimentalA series of La3+-doped BaTiO3-based nano-crystals were prepared with sol-gel technology using various parameters. The precursor solution was prepared in the presence of barium acetate, lathanium acetate, and titanium tetrabutoxide monomer in butyl alcohol. According to the flow chart (fig. I.), Ba(OAc)2, La(OAch dissolved in the glacial acetic acid (0. lmol/40ml) in a three-neck flask were mixed with a solution of titanium tetrabutoxide monomer in butyl-alcohol(l 7ml/20ml) at room temperature and under constantly, vigorous stirring conditions. In most cases, the resultant solution was golden yellow and stable in the air. To this precursor solution, containing Ba, La, Ti in the desired ratio, water was added incrementally for hydrolysis under continuous stirring until sol was formed. After aging for more than 2 hours, sol was transformed to gel at room temperature. If heated during aging, the gel was formed in a shorter time. The wet gel was allowed to dry at 50°C for more than 10 hours. The dried gel was transparent or light yellow. In order to obtain BaTiO3-based nano-crystals, the amorphous dry gel was calcined at 600°C, 700°C, 800°C, 900°C, 1000°C respectively[5]. The ceramic humidity sensor was formed through the cold-pressed, aged, capsulated routes. The dried gels were crushed in an agate mortar and then pressed into discs of ? 1.5 X l.5mm (l.5mm diameter and l.5mm thickness), then held at about 16.5 MPa pressure for 3 min [6]. The disc was sintered at 1350°C and 1400°C for I hour respectively. During the processing, an Ag-Pt electrode was inserted in the sensor [7]. (See the flow chart.)"

Jan 1, 2000

By T. T. Lin, N. H. Madsen, K. Groom, B. A. Chin

"The objective of this research is to investigate the feasibility of using infrared sensors to monitor the welding process. Data were gathered using an infrared camera which was trained on the molten metal pool during the welding operation. Several types of process perturbations which result in weld defects were then intentionally induced and the resulting thermal images monitored. Gas tungsten arc using AC and DC currents and gas metal arc welding processes were investigated using steel, aluminum and stainless steel plate materials. The thermal images obtained in the three materials and different welding processes revealed nearly identical patterns for the same induced process perturbation. Based upon these results, infrared thermography is a method which may be very applicable to automation of the welding process.IntroductionAutomatic welding is commonplace in industry today. However, most, if not all, involves preprogramming for performance of a repetitive task. These systems are incapable of correcting for perturbations which arise during the welding process. Control of the welding process requires the identification and monitoring of perturbations in a wide variety of parameters. The varied nature of these parameters and the large number of variables involved have thwarted previous attempts at closed loop control of the welding process. The sensor(s) employed by a control system need to meet rather strenuous requirements. First and foremost of these is that such a sensor must be able to identify and discriminate between perturbations that might affect the quality of the weld, including such geometrical perturbations as a change of direction in the seam between the parts being welded, gaps in the seam or a misalignment of the parts being welded. The sensor should also be able to locate and identify contaminants and impurities in the weld puddle and ahead of it while monitoring the extent of the heat-affected zone and the cooling rate of the metal. The sensor(s) should, additionally, be able to perform these tasks in a time frame that is consistent with automatic control of the welding process. This paper presents results that could aid in the assembly of such a controlled welding system."

Jan 1, 1986

By Xuemei Zheng, Aiyuan Ma, Chao Liu, Guojiang Li, Chenyu Sun, Jinhui Peng, Libo Zhang, Yongguang Luo

In this paper, the removal of fluorides and chlorides from blast furnace dusts by water vapor enhanced microwave roasting was investigated, combined with the advantages of microwave selective heating and based on a thermodynamic analysis of zinc and lead halides. According to proposed reactions in the process, detailed experiments were systematically conducted to study the effect of roasting temperature, holding time, air flow, water vapor flow rates, and stirring speed on the efficiency of the removal of F and Cl. The results show that 97.26% of F and 64.23% of Cl could be separated when the condition of the roasting temperature of 650°C, stirring speed of 80 rpm, holding time at 60 min, air flow of 350 L/h and water vapor flow rate of 8 mL/min was optimized.

Jan 1, 2016

By J. H. Puffer

The copper mineralization of the Mesozoic Passaic Formation of New Jersey is typical of copper deposits in eastern North American Mesozoic sediments. Most such deposits are located at the base of the first of several basalt flows that are interbedded with continental, red-bed sediments. The copper mineralization is similar in most respects to that of the Keweenawan Basalts of the Lake Superior area. The first basaltic flow units of the eastern North American Mesozoic basins, and the Keweenawan Basalts, are continental quartz tholeiites of similar chemical composition and copper contents. The copper minerals and associated zeolite facies metamorphic mineral assemblages of these two rock units are also approximately the same. Stoiber and Davidson (1959) suggested that Keweenawan copper was mobilized and concentrated during metamorphism. The evidence pertaining to the Mesozoic copper deposits of New Jersey is consistent with such an interpretation and also with DeVore&apos;s (1955) suggestion that ore fluids commonly arise as a result of the mobility of metals under metamorphic conditions. There is additional evidence that final metamorphic concentration of Mesozoic copper was preceded by an initial stage of hydrothermal precipitation related to fluids emitted by basaltic magma.

Jan 1, 1987