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By Bin Xu, Qian Li, Yong-bin Yang, Xiao-liang Liu, Tao Jiang, Yan Zhang

Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

Jan 1, 2015

By Feng Liu

A thermal upgrading process by which nickel value can be concentrated in a ferronickel alloy is a possible alternative to treat Sudbury pyrrhotite (Po) tailings with nickel content of 0.5–1.5 wt%. The basis of this process is precipitation of Ni from Po at high temperature once Fe/S ratio in the iron-deficient Po is shifted towards stoichiometric or near stoichiometric FeS (troilite) either by the addition of iron and/or the removal of sulfur. For the iron addition route, the reaction between elemental iron and nickeliferous pyrrhotite to produce ferronickel alloy and Ni-depleted iron sulfide phase plays a critical rule. In this paper, the formation mechanism of ferronickel alloy was investigated using the diffusion couple technique to better understand the nickel diffusion behavior in the iron and sulfide phases.

By Mukesh Jain

The liquor from potroom wet scrubbers is treated with lime to precipitate the soluble fluorides. The solids after filtration, referred to as scrubber mud, contain in addition to calcium fluoride, alumina, carbon, tars including polyaromatic hydrocarbons (PAH), cryolite and pachnolite and are considered hazardous. This communication deals with the pilot plant scale calcination of scrubber mud with a rotary kiln to obtain non-hazardous fluoride raw materials. Air classification was performed to separate the mudinto aluminarich andcalcium fluoride rich fractions which were then calcined. With proper control of calcination parameters and addition of lime, the carbon and tars were destroyed and hydrogen fluoride emissions were controlled. The calcined products could be used in the steel indusny as a fluxing agent or as a substitute for fluorspar in the production of aluminum fluoride.

Jan 1, 1994

By D. B. Dreisinger

The zinc pressure leach process developed by Sherritt Gordon, Ltd. permits the direct leaching of sulphide concentrates according to the overall reaction, ZnS +H,zS04 +402.+ZnS04+H20 +S0 The kinetics of the leach are affected by three rate controlling steps; ( l) oxygen mass transfer from the gas to the leach solution, (2) homogeneous oxidation of ferric ion to ferric ion by dissolved 011.ygen and (3) ferric ion leaching of zinc sulphide in the presence of a sulphur dispersing detergent (lignin sulphonic acid). Fundamental studies have been conducted to identify the factors that influence the kinetics of each individual rate controlling step. Oxygen mass transfer studies have been directed toward optimization of the agitator configuration for solids mixing and gas pumping from the atmosphere above the leach slurry. The rate of ferrous oxidation by molecular oxygen and the rate of zinc sulphide leaching by ferric ion have been studied over a wide range of temperature and solution compositions. The study of zinc sulphide leaching by ferric ion was supplemented by a series of interfacial tension measurements in the liquid sulphur - zinc sulphate solution system. The various kinetic studies have been summarized in terms of the importance of each rate to the performance of the process.

Jan 1, 1990

By Ling-yun Yi, Yuan-bo Zhang, Bing Hu, Zhu-Cheng Huang, Zhen-yuan Liao

"Nucleation and growth mechanism of iron crystal grain in coal-based shaft furnace direct reduction process by microwave heating were investigated by optical microscope, scanning electron microscope and EDX. The results indicate that microwave has selectivity on various minerals which absorb microwaves. The high temperature in certain area of pellets and thermal stress on the interface of minerals are formed, results in the wustite grain smashed along the joints, and iron crystal grains turned out a spherical shape obviously. The iron crystal nucleus is formed firstly at the edge of wustite, on the interface between grains and in the holes in pellets, and grows gradually while reduction carries on from surface layer to inner core. Microwave heating promotes the rate of transportation and accumulation of the iron crystal grain, increases growth rate of iron crystal grain and contributes to formation of dense iron-jointed crystal texture eventually.IntroductionMicrowave energy as a new energy, which selectively heating materials through internal energy dissipation, has the advantages of heating uniformity, high thermal efficiency, fast heating, clean and pollution-free compared to conventional heating motheds. Microwave energy also has obvious superiority in increasing productivity. Thus, it has been widely used in many areas, including electronics, food processing, chemical, medicine, environmental protection, and family life etc [1]. As a rapidly developed green metallurgical method, microwave heating also has been widely recognized by areas of grinding, pretreatment, pre-reduction, drying, furnacing, metal extraction, and waste materials processing and utilization. Some research achievements are gradually putting into practice, showing great potential in chemical and metallurgical industry [2-3]."

Jan 1, 2011

By D. E. Karvelas

Argonne National Laboratory is conducting research to develop a cost-effective and environmentally acceptable process for the separation of high-value plastics from discarded household appliances. The process under development has separated individual high purity (greater than 99.5%) acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS) from corruningled plastics generated by appliance-shredding and metal-recovery operations. The process consists of size-reduction steps for the commingled plastics, followed by a series of gravity- separation techniques to separate plastic materials of different densities. Individual plastics of similar densities, such as ABS and HIPS, are further separated by using a chemical solution. By controlling the surface tension, the density, and the temperature of the chemical solution, we are able to selectively float/separate plastics that have different surface energies. This separation technique has proven to be highly effective in recovering high-purity plastics materials from discarded household appliances. A conceptual design of a continuous process to recover high-value plastics from discarded appliances is also discussed. In addition to plastics separation research, Argonne National Laboratory is conducting research to develop cost-effective techniques for improving the mechanical properties of plastics recovered from appliances.

Jan 1, 1996

By Marion Dattilo

The search for an improved anode for the electrowinning of lead from fluosi1icic acid medium has led the U.S. Bureau of Mines to investigate composites. Polymer bonded metal oxide powders which may contain catalyst additions were prepared by pressing. These composites display an improved activity toward the oxygen evolution reaction over electrodeposited lead dioxide on titanium, carbon, and nickel substrates. These composite electrodes contain 5 to 10 wt. " binding polymer, with the balance being metal oxides. Lowered anodic potentials achieved using the compnsite anodes resulted in lower levels of lead dioxide deposition during electrowinning.

Jan 1, 1995

By Wenjie Zhu

Chromite ore processing residue (COPR) is a hazardous waste containing high concentration of chromium. We describe here a pioneer trial of detoxification of COPR in column reactor with an indigenous chromate reducing bacterium Leucobacter sp. Ch1, which showed high chromate reducing ability at high pH. Under the optimum conditions, at 30°C and pH 10.0, pH of leachate decreased from 10.3 to 8.3, and Cr(VI) concentration in solution decreased to zero mg L-1, and 76.4% of Cr(VI) was removed from COPR samples. The leaching toxicity of detoxified residue was 1.1 mg L-1 that was lower than national standard of China.

Jan 1, 2008

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 Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

"A cellular model of the plastic deformation of polycrystalline aggregate is proposed and comprehensively described. Representative volume element (RVE) of a solid body, that is being deformed, is described as a population of interconnected units that, in turn, can consist of lower scale level units. Sliding along the various allowed sliding systems deforms simple units, which do not have an internal structure. For consideration of stress distribution within the limits of components, the approach of self-consistent field is used. Rotation of units and moment stresses connected with it are taken into account. Results of computer experiments are analyzed.1. IntroductionMicromechanical models of polycrystals are a link between the research of plastic deformation on micro and macro levels. Computer simulation of inelastic strain of polycrystals has found a great deal of interest as well. Despite the fact that this approach does not allow to obtain macroscopic constitutive relationships that are used in deformed solid body mechanics, it clarifies essential features of the phenomena in many aspects. First of all, it concerns effects stipulated by interdependence of micro-level and macro level of plastic deformation processes. Also, with the computing mechanics, instead of constitutive relationships, the adequate computer models can be used. Broad possibilities for computer simulation of various processes are opened by cellular automata approach. By means of numerical experiments, the cellular automata allows to study the macro behavior of the whole ensemble of cells depending on the local microscopic laws that define evolution of each cell and its interaction with the closest environment.We propose a mathematical model of a polycrystalline aggregate (the cellular model) based on a self-consistent scheme and on the interaction law similar to the one by Berveiller and Zaoui [1]. Our original solution is the self-similar structure of cellular automata that allows modeling of the fractal nature of real materials (Figure 1). The goals of this work are to present the major structures and relations of cellular model of polycrystal and to test this model for its adequacy as for describing known effects and dependencies. Identification of the model and its application for studying of concrete polycrystals are put aside for the future research."

Jan 1, 2001

By Michael J. McGuire

Rostoker, Inc. has developed a process to smelt solid hazardous/non-hazardous inorganic wastes. Near seven hundred experiments were performed. Actual industrial wastes as well as reagent grade chemicals were used. By mixing a multiplicity of these wastes to proper formulations, then furnacing them, it was determined that saleable end products could be reclaimed; metal, fume and slag. The slag, due to its siliceous structure was tested to be leach resistant (40 CFR). This formed the essence of our patent, #5,180,421 "Method and Apparatus for Recovering Useful Products from Waste Streams". What is unique is that a HTMR (High Temperature Metal Recovery) process has been developed that can treat a multiplicity of wastes within the same furnace. The discussion will include a list of waste streams we have treated, details of proper waste formulation and experimental results.

Jan 1, 1994

The results of laboratory, large-scale laboratory and commercial scale investigations regarding the process of slag melts cleaning by oxidizing-reduction gas mixtures with a wide range of Po2 and the use of matte of various compositions as an extracting phase are presented. The copper, nickel and cobalt behavior during the cleaning process has been studied based on SEM and x-ray Microprobe of the quenched slag melts. The general cleaning mechanisms have been found. On the basis of the obtained data the most efficient cleaning methods have been proposed.

Jan 1, 2003

By Satu Strömberg

Four different nickel concentrates were oxidized in a laboratory scale laminar flow furnace in simulated flash smelting conditions. The major nickel- and iron-bearing minerals in the con- centrates were pentlandite, violarite, gersdorffite, and pyrite and pyrrhotite, respectively. Thermal decomposition, ignition and oxidation behavior of nickel and iron sulfides were examined by using optical and scanning electron microscopy. General reactivity of the concentrates was monitored with sulfur removal which was most effective in violarite-based concentrate. Pentlandite-concentrates needed higher experimental temperatures for complete desulfurization and gersdorffite-based concentrate contained 5 - 10 % of the original sulfur even in the most oxidizing conditions studied (1 100°C, 50 vol-% 02). The reactivity of the iron minerals was found to depend on the other minerals present in the concentrate. In this paper, the observed re- action products and mineralogical changes are presented and preliminary conclusions of possible reaction mechanisms of nickel-bearing minerals are discussed.

Jan 1, 1997

By Young-Chul Kang

The Onsan Copper Smelter of LG-Nikko Copper Inc. is a unique plant, which has been operating two smelting processes since 1998. The operation of the first one was started in 1979 with a capacity of 80,000tpy of copper in concentrates utilizing Outokumpu flash- smelting technology. The other one was started in 1998 based on Mitsubishi continuous process with a capacity of 160,000tpy of copper in concentrates. Through several expansion projects, the total smelting capacity of both processes is expected to reach 430,000tpy of copper in concentrates towards the end of 2002. This article describes operation advantages of having two different processes at one plant and comparative operation results in terms of productivity, impurity distribution, energy consumption and environment issues and etc?

Jan 1, 2003

By Frederick T. Wallenberger

"Laser assisted chemical vapor deposition (LCVD) is a new containerless fiber process whereby growth of small diameter fibers or microstructures (microsprings, microsolenoids) occurs directly from the vapor phase. The laser beam has a focal point adjusted to coincide with the tip of the growing fiber inside the reaction chamber. Since the growing fiber is not in contact with reactor walls or foreign materials, it is chemically pure, and suitable for optical uses and uses requiring high structural uniformity. Continuous fibers and multifilament yams are possible. The use -of high reaction chamber pressures (1-10 bar) and a small wavelength Nd-YAG laser made it possible to fabricate small diameter fibers at growth rates >1 mm/s. This paper describes the synthesis of single crystal, polycrystalline and amorphous fibers by LCVD, and provides a comprehensive analysis of phase transformations occurring during their fabrication.IntroductionLaser assisted chemical vapor deposition (LCVD) is a new containerless fiber process [1-10] whereby growth of small diameter fibers or microstructures occurs directly from the vapor phase. The laser beam has a focal point adjusted to coincide with the tip of the growing fiber in the reaction chamber (Figure 1). The diameter of the growing fiber corresponds to that of the laser focus. Depending primarily on the laser energy (Le., the temperature at the growing fiber tip), it is possible to obtain single crystal, poly crystalline or amorphous fibers by this method.Since the growing fiber is not in contact with reactor walls or foreign materials, it is chemically pure, and suitable for optical uses and uses requiring high structural uniformity. Laser assisted CVD is a potentially continuous process; continuous fibers and multifilament yams are possible."

Jan 1, 1994

By Fuxing Yin, Akira Sato, Yoshiaki Ohsawa, Kohji Kawaharai

"INCRAMUTE alloy (nominally 45Mn-53Cu-2Al wt. %) has a specific damping capacity as high as 0.4, through a solid-solution and aging treatment. The damping behavior of the alloy is highly temperature-dependent and shows a peak near room temperature. The inadequate strength in the high damping condition restrains the practical application of the alloy, as structural components. Ferromagnetic MnB particles are dispersed in the alloy during induction remelting the matrix alloy in an argon atmosphere. Surface modification of the MnB particles by mechanical alloying (MA) and suitable control of the addition process cause a homogeneous distribution of MnB particles in the alloy. In the composite containing 2 wt. % MnB particles, temperature dependence of damping capacity is improved, and higher damping capacity is still retained in the temperatures over 60 °C. Meanwhile, the Young's modulus and tensile strength were also increased by about 20%. The roles of the MnB particles in improving both damping behavior and mechanical properties were also discussed.IntroductionMany viscoelastic materials, such as rubbers, polymers and plastics, have the superior ability to damp vibration and noise. However, in the applications as structural materials the high damping capacities of materials are pursued upon the satisfactory mechanical properties, especially those at elevated temperatures. Damping alloys are finding more and more applications in structures where noise and vibration ·should be ·eliminated. Specific damping capacity (SDC), defined as the ratio of the energy dissipated to the maximum vibration energy stored per cycle, is usually used to evaluate the damping capacity of alloys. INCRAMUTE damping alloy, developed by the International Copper Research Association, Inc., has a nominal composition of 45Mn-53Cu-2Al in weight percent. The high damping· microstructure of this alloy is obtained through the solution treatment at 820 °C followed by a water quench and aging at 400°C for 10 hours followed by cooling to room temperature [1]. With the heat treatment, a SDC peak ·vs. temperature of as high as 0.4 was observed in the alloy at the strain amplitude of about 10-3 while a tensile strength of about 500MPa was sustained."

Jan 1, 2000

By Heikki Tuovinen

The total utilization of raw materials and energy is the most important criterion when planning. industrial processes. The main goal is clearly to use the raw materials and energy as effectively as possible in order to make the desired products directly in the primary process itself&apos;, or to recycle unused materials and energy either as such, or after cleaning back into the process. However, few industrial processes are so straightforward. Most processes generate by-streams of materials and energy, which cannot be recycled directly and it is namely these by-streams which tend to remain as wastes. These by-streams are slags, dusts, vaporized metals, liquids, slurries, sludges, gases etc. Most base metal processes produce all these by-products. Waste water and gas emission controls and regulations are tightening all the time, so new processes must be developed to keep pace with these requirements. These processes generate more solid wastes, which must be utilized or at least processed into a harmless form landfilling. Municipal and hazardous wastes also contain valuable materials and energy, which must be used to minimize landfilling. The development of processes for these purposes places even greater demands on research and development. The same principles and methods developed for mining, ore dressing and metal refining processes can also be adapted for research and development work on processes for waste minimization. However, the problems encountered are much more complicated and less familiar, demanding more versatile and accurate tools and equipment. This paper presents principles, examples and some references of R & D work on processes for waste minimization.

Jan 1, 1992

By Ari I. Kogut

Impurity minerals in fluorspar ores and concentrates from a deposit in Southern Africa have been studied by reflected light, transmitted light, and cathodoluminescence microscopy. The principal impurities are quartz, calcite, aegirine, apatite, ankerite, magnetite, goethite, and synchysite [Ca(La,Ce,Nd)(C03l2Fj. Cathodoluminescence microscopy was found to be very useful in studying the character of the fluorite and especially for recognizing the presence of apatite and calcite impurities. Fluorite exhibits blue, calcite shows yellow, and apatite has white, light purple, and pink cathodoluminescence. The cathodoluminescent character of apatite varies with its geological environment and position in the orebody. The results of this microscopic study show that phosphorus present in flUorite concentrates occurs principally in binary locked apatite-fluorite particles. Successive fluorite cleaner concentrates contain progressively smaller amounts of locked apatite-fluorite particles. Free apatite has been effectively partitioned to the final tailings.

Jan 1, 1995

By Torma A. E.

Biotechnological processes are considered to be cost effective especially for situations where the recovery of metals from &apos;Very large volumes containing trace metal concentrations (less than 10 ppm) is concerned. Microorganisms, alive or dead, or their products can be highly efficient and selective biosorbents for metal concentration. It is important that the metal bound to the biosorbent can be stripped by suitable agent(s) and regenerated for repeated use. The stripped solution should be concentrated enough to be introduced into the common metal recovery circuit. The industrial acceptance of biosorption processes is dictated by increased competitive advantage over other processes. This paper reviews the pertinent literature?, regroups the information, and points out future possibilities for the mineral and metal processing industries.

Jan 1, 1992

By N. J. Themelis

The basic chemical, thermal and transport principles that underlie sulfide smelting of. copper, nickel and lead are reviewed. Two basic types of modern smelting processes are distinguished?: flash-smelting, where the predominant reactions occur between oxygen-bearing gas and concentrate particles dispersed therein; and bath-smelting where the concentrate is enveloped and reacted in a turbulent bath of matte, slag and gas. The controlling heat and mass transfer phenomena are discussed, and appropriate correlations are proposed.

Jan 1, 1983