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By Ju Shao-hua

Although nowadays gold extraction methods are very abundant, none of them is satisfying, especially, in the field of heap leaching of low grade gold ore. The traditional heap leaching method of cyanide method plays an inglorious role of badly environmental pollution. In this paper, a bran-new and innoxious method of gold extraction system, metal-ammonium-chloride-ammonia (MACA), was proposed, and also analyzed both thermodynamically and practically. Thermodynamically, according to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the thermodynamics of Au-NH4Cl-NH3-H2O system was studied by using the exponential computation method and through MATLAB programming, and the solid figure of its potential - c(NH4Cl) - c(NH4OH) was drawn. The results showed when the concentrate of ammonia is higher than 0.6 mol?L-1, fAu+/Au is only about -0.2 v. Practically, the leaching results of a cuprous gold ore showed that the extraction of gold can reach to 80% in this system. The preliminary results of reduction of the rich solution with copper and zinc powders showed that with deoxygenizing, the reduction effects were relatively good. These new findings and results have established a theoretical and practical base for developing a new process for heap leaching of low grade gold ores in this system. And the new process owns a series of merits such as, non-cyanogens, nontoxic, broader applicability.

Jan 1, 2006

By Tejs Vegge

The lack of suitable means of storing hydrogen for use in the transport sector is generally viewed as a primary showstopper for a hydrogen economy. Recent developments within solid state hydrogen storage in complex hydrides and metal ammines have sparked new hope of a long term solution, but as of now, no materials fulfill all the DoE targets for onboard storage [1]. A detailed physical understanding of the ab-/desorption processes and the role of the essential catalytic additives is an essential prerequisite for the development of new optimized hydrogen storage systems. Here, we illustrate the potential of utilizing the synergy of combining state-of-the-art in theoretical methods and experimental techniques in the analysis and design of materials for hydrogen storage. Recent advances in computer hard- and software has made it possible to treat many of the essential problems in such materials, i.e. structural stability, hydrogen dissociation and diffusion, with high accuracy methods like density functional theory. We rely on such results to guide our synthesis of new materials, and to interpret our experimental results from, e.g. time dependant in situ x-ray diffraction, synchrotron/neutron experiments, and advanced materials testing. Through a continuous feed-back optimization loop between theory and experiments, the obtained nano-scale insight is used to expedite the design and development of novel materials for hydrogen storage.

Jan 1, 2006

By Michael A. Krstich

A soil washing pilot plant to treat soils at the U.S. Department of Energy (DOE) owned Fernald Environmental Management Project (FEMP), was designed based on extensive bench-scale testing. The system's design incorporated a combination of physical separation and' chemical extraction processes and was tested on two soils. The textural composition of the two soils was approximately 20 percent sand, 60 percent silt, and 20 percent clay. Since this grain size distribution was not considered optimum for physical separation techniques, thesoil washing pilot plant had to be designed with selected equipment to provide specific soil size fractions during processing operations. A trommel, vibrating screen deck, centrifuge, and attrition scrubber were used in the system to selectively separate specific soil size fractions at 4.75, 2, 0.3, and 0.02 millimeters (mm). The trammel used high pressure water [1000 pounds per square inch (psi)] during the initial step of the process to reduce soil aggregates to single grain composition, separate out greater than 4.75 mm gravel, and dislodge chemical contaminants from the individual soil particles. The vibrating double-screen deck provided 2 - 4.75 and 0.3 - 2 mm soil fractions that, when combined, averaged greater than 75 percent solids for both soils. The centrifuge was designed to take the less than 0.3 mm soil slurry from the screen deck and produce a particle size of 0.02 mm. The centrifuge produced a high solids stream that averaged greater than 70 percent solids for both soils. These 0.02 to 0.3 mm soil solids from the centrifuge were combined with the 0.3 to 4.75 mm soil solids from the screen deck and processed through the attrition scrubber. The data collected from the pilot-plant operation was used to aid in the design of a full-scale system and was instrumental in formulating full-scale process operations and the selection of equipment.

Jan 1, 1995

Aluminum has experienced significant growth in automotive applications over the last decade as a result of its properties and performance attributes. Looking to the future, the opportunities for continued growth in powertrain and suspension applications plus light weighting of body structures offer the potential for considerable further growth. This represents a growing "energy bank" of aluminum that will become available for recycling at the end of these vehicles' lives. Today, around 90% of the aluminum is recovered and recycled from scrapped vehicles because of its high value relative to other materials. The future growth offers opportunity for new technology and practices, to maximize scrap quality and recycling application. This paper will review the demand for these new technologies and practices and will discuss industry activities being pursued in this area.

Jan 1, 2000

By M. R. Barkhudarov

Semi-solid metal can be formed into useful products of near net shape and high quality. Use of this method has been limited, however, because of the difficulty of working with metal in the semi-solid state, which has strong shear rate, temperature and time-dependent properties. In this paper we describe a thixotropic model and apply it to the problem of small metal droplets impacting on a flat plate.

Jan 1, 1997

By David G. C. Robertson

A new approach is described for the calculation of the kinetics of metal/slag, metal/slag/gas, and metal/matte/slag/gas reactions. The algorithm assumes that equilibrium is achieved at the interface between phases, and uses an equilibrium solver (such as SOLGASMIX) to compute the equilibrium state at the interface at each time step during the reaction. For multiple phase systems a number of unit operations, representing the different phases and interfaces, must be connected together in a reasonalbly complex manner, and the METSIM software package has been utilized for this purpose. The new approach is superior to the SMAK software developed by the author and his co-workers over the past decade, for the reasons discussed in this paper.

Jan 1, 1995

By Sudhir C. Dhara

An attempt has been made on the concentration of Platinum Group Metals (PGM) from the converter matte material by microbial .leaching. Biological oxidation of base metal sulfides such as iron, copper, nickel and free sulfur present in the matte material using Thiobacillus ferrooxidans is an alternative method to concentrate the PGM-and gold. The method which produces a platinum group metals concentrate is comparable to chemical processes and electrochemical process.

Jan 1, 1995

By Jimsher N. Aneli

There are many experimental works on the investigation of temperature effect on the conductivity of polymers filled by carbon materials. However frequently the establishment of current nature in the polymer heterogeneous systems becomes difficult. This fact is explained by complexity of calculation of different physical or chemical phenomena passing in materials at variation of the temperature. Among these phenomena it must be noted some morphological changes in the structure of polymers. These changes reflex on the structure of conductive system of composites. So, it has been shown, that the character of temperature dependence of thermal noises level and conductivity of some polymers filled by carbon black essentially depend on some relaxation transition in the polymeric matrix. In this paper the effect of difference transitions in polymer matrix of filled by carbon black some polymers and rubbers have been investigated in a wide temperature range. The importance of such investigation is due to possibility of application of resistive temperature sensors based on conductive polymeric composites (CPC) to measuring technology. The experiments have been carried out in the cavity with regulation of temperature in the range 110-650K. The resistance of samples was measured by four electrodes method. The samples were obtained by hot pressing of dry mixture of powdered components at chosen temperatures, pressures and cooling time in the case of plastics and by peroxide vulcanization of the elastomers in the case of the rubbers. The samples were produced on the basis of the following thermoplastics: low density polyethylene, polytetrafluoroethylene, polycarbonate and polydimethylmethylvinilsiloxane.

Jan 1, 2006

By Takahiko Okura

"It is said that the energy and resources crisis will come before long because the lifetime of known deposits of crude oil and common metals such as Pb, Zn, Cu is estimated to be less than 50 years. Establishing the sustainable society by means of resources-recycling has become an absolute necessity.The non-ferrous metals industry in Japan has been involved in the resource- recycling business for many years, along with the introduction and enforcement of various legislations to preserve the environment and natural resources. Including process-linkage during various manufacturing activities, the non-ferrous metals industry, the iron-making and cement industries are treating considerable amounts of recycled materials and wastes, in an environmentally-sound and economic manner.The Mining and Materials Processing Institute of Japan has submitted “The present and issues in Japanese non-ferrous metals and recycling industries.”The topic of the paper is to highlight the actual conditions within the resources-recycling structures and the present issues.IntroductionGlobalization has been changing the world, introducing the spike of energy and metals price. In addition, the preservation of the environment has also been strongly facing the crisis and many people have been aggrieved by both shortage and the increment in the price of the meals.In the world of metals, even though their reserves are coming depleted, the production rates are increasing, and then the industry has to enhance their productivity under stricter environmental regulations. The Japanese industry experimented the same scenario some 40 years ago, facing big pollution problems, but concurred them and enhanced the technology to overcome the more severe regulations. It will be fruitful to present the current situation in the Japanese industry for the world. The present issues are also presented."

Jan 1, 2008

By Gaifeng Xue, Jingxuan Zhou, Shangchao Liu

"Both COD and TOC can characterize organic pollution of coking wastewater. In theory, there is a linear correlation between these two indicators. After continuous monitoring TOC and COD of coking waste water, linear regression relationship between of these to indicators was studied with the use of mathematical statistics. And conversion equation between these two indicators was established, and using t-test method for significance testing. The results showed that the linear relationship of COD and TOC was significant. Also interval estimation of equation slope and intercept were given in the condition of 95% confidence level. A linear regression equation established can be used to indirectly convert TOC to COD with high precision and accuracy.IntroductionBoth chemical oxygen demand (COD) and total organic carbon (TOC) are measure of the degree of characterization for organic pollution of water bodies. The current COD standard analytical methods is Potassium dichromate titration method [1] . there are some disadvantages in this method, such as only part of organic matter in the water bodies being oxidated, the refluxed steps, a long time needed for each measurement, high cost. It is the most important that sulfuric acid silver and mercury sulfate reagents used in the measurement may easily lead to secondary pollution. In contrast, the measurement of TOC is by the method of combustion or Photocatalytic Oxidation. The result could be easily got from the instrument. There are some advantages in this way, such as easy operation, short time and little expenses for each measurement and no secondary pollution 121• In addition, the measurement of TOC has higher degree of precision and accuracy than the measurement of COD both in the determination of calibration standards and actual samples. The meaning and contrast of TOC and COD are listed in the table 1."

Jan 1, 2013

By Junji Shibata

Through-hole copper plating is performed to make a multi-layer printed circuit board. The through hole plating is first carried out by Pd catalyst treatment, followed by copper non-electric plating. The amount of Pd catalyst used in one plant is about 0.25-2 m3/month (8 g/dm3 PdCl2 base) depending on the plant scale, and the cost of the catalyst reaches 17,000¬I35,000 US$/month. In this study, the flow and material balance of a Pd in Pd catalyst treatment process was investigated. About 60% of Pd catalyst adheres on the through-hole and other part of setup, while 25% is released into the washing liquor. Pd in the washing liquor should be collected by a suitable method like a pressure filtration using diatomite. The material balance of Pd in Pd catalyst treatment process and the recovery method of Pd from waste solution containing Pd catalyst was investigated.

Jan 1, 2003

By Xuewei Lv

An intelligent recognition and quantification system for the micrographs iron ore sinter was developed in the current paper. The average distribution parameters in a gray histogram of minerals by a Gaussian gray distribution model were obtained. The feature curves of the gray histogram of two minerals were achieved by combining the two density functions. The feature indexes, such as the number and position of the peaks and the valleys of two minerals in different ratios, were quantified by differentiating the distribution functions. This algorithm is able to extract the feature of the minerals adequately and accurately for recognizing the composition and phases of the minerals intelligently.

Jan 1, 2009

By Kunio Nakahara, Kashiwagim Junichi, Takao Hayashi

"There are many problems for electronic devices and parts which were caused electrostatic damage by static electricity. It is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating. Mitsui Mining & Smelting Co., Ltd. developed metal oxide type electroconductive pigment PASSTRAN (trade mark) Type-IV which is barium sulfate coated with SnOz(Sb) thin electroconductive layer. This paper shows about pigment characteristics and film condition of antistatic transparency paint which contained PASS TRAN.L.IntroductionRecently rapid development of electronics technology diffused electronic devices and products to Office, Factory, Laboratory and our life. But the other side, there are many problems for electronics parts which were caused electrostatic damage under static electricity. Demand of antistatic materials were become lager by this situation.There is close relationship between surface resistivity of material and static electricity. If the surface resistivity of object is enough low (under 109 Q /Sq), static electricity is dissipated quickly. So it is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating.1) There are many type of electroconductive materials, for example, carbon black, metal powder, electroconductive polymer and so on. Especially, carbon black is used for general purpose by reason of its low cost, but it has big problem of black color. It can not get any color without black, and it caused contamination of carbon.In recent years, metal oxide electroconductive pigment (ECP) was developed and used for special purpose which demands transparent coating or easy dispersion to make ECP paint or endurance under hard environment and so on. Mitsui Mining & Smelting Co., Ltd. developed electroconductive pigment PASSTRAN Type-IV which is BaS04 coated with electro-conductive Tin oxide layer."

Jan 1, 1998

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Xingbin Li

A direct hydrometallurgical process of extraction molybdenum and nickel from molybdenum-nickel ore by pressure water leaching without reagent was studied. The extraction of Mo and Ni from molybdenum-nickel ore by oxygen pressure leaching, which exploit the characteristic of molybdenum-nickel minerals contain high concentration amorphous sulfide which has highly active, and make the most of easily oxide to sulfuric acid and sulfate at low temperature and excess oxygen presence of the amorphous sulfide. Under oxygen pressure conditions, considerable molybdenum and almost all the nickel were extracted into solution in the leaching process. The results show that with the leaching time for 3~4h, temperature at 150o C, liquid-to-solid ratio of 2mL/g, mineral granularity of 0.074mm, oxygen partial pressure of 0.4~0.5MPa without other reagent, molybdenum leaching percentage can be over 80% and nickel leaching percentage can be more than 97%. Furthermore, about 80% sulfur in the Mo-Ni ore has been transformed into sulfuric acid.

Jan 1, 2014

By René Bustamante

A GPSS/H simulation is beeing done for a traditional smelter of copper, which envolves a reberberatory furnace, a set of Peirce Smith converters (PSC) and a refining furnace. The objective is to try different plant layouts, being the handling of liquid material at high temperature one the mainly concern, this envolves a study of the ladles and cranes used. Some of the modifications that can be evaluated through the model is the role of oxygen potential when tonnage oxygen is used, number of cranes, PSCs in operation, etc.

Jan 1, 1992

By Jiakai Zhang

Many postconsumer electrical and electronic equipment wastes contain a considerable amount of rare earth elements (REEs); however, the current level of REE recycling from them is limited (<1%). Neodymium–iron–boron (NdFeB) magnets, used at both small- and large-scale, from computer hard disk drives and small tools to wind turbines and cars, are a good example of such waste materials that contain high content of neodymium (Nd) and dysprosium (Dy). These elements are considered critical metals because they are the main building block of emerging green technologies that will allow for GHG emission reductions. Because demand for these green products is increasing around the world, the demand for REEs is increasing quickly, putting their supply at risk in the near future. Thus, it is critical to develop efficient, robust, and cost-effective processes to recycle these elements from this class of electronic waste materials. Here, we performed a thorough characterization of a N52–NdFeB magnet to identify its composition, crystal structure, and morphology. Furthermore, we developed an efficient hydrometallurgical process to extract Nd and Dy with high efficiency (more than 95%).

By Susana Caballero, Lourdes Yurramendi

Air Pollution Control (APC) ashes from Municipal Solid Waste Incineration (MSWI) plants need to be treated prior to landfilling due mainly to their heavy metals content. This research evaluates the capacity of the APC residues to sequester carbon dioxide, while the ash becomes stabilized for storage. It has the benefit of using two wastes, with no addition of any raw material. APC samples from different MSWI plants were treated by gas/solid accelerated carbonation at different temperatures and carbon dioxide concentrations to evaluate the residue behaviour to the process. The extent of carbonation was evaluated by means of weight gain upon carbonation and by the measurement of the final carbonate content. The APC residues were analyzed before and after the treatment in order to know their composition and their leaching behaviour according to the criteria for the acceptance of wastes at landfills established by the European Council Decision 2003/33/EC.

Jan 1, 2008

By Christian Trassy, Pierre Proulx

"Inductive plasmas are now commonly used in material processing: spraying, powder synthesis, densification or spheroidization. An inductive discharge presents, in the coil region, recirculation eddies due to the Lorentz forces, resulting in an axial backflow. If the central jet is strong enough to ""pierce"" the recirculation this axial backflow disappears on the centerline, but the external layer of the injection flow is skimmed by the remaining eddy, and particulates are rejected to the discharge periphery. To avoid this disadvantage, it is common to introduce the injection pipe inside the discharge, so that its outlet is positioned after the recirculation eddy. The powders remain confined in the axial zone, to the expense of shortened residence time.In order to increase the efficiency of the particle trajectories, a double flow injector has been designed. It enables the particles to travel closer to the axis, while the outer schrouding gas is skimmed and passes through the electromagnetic eddies. This injector is made up of two concentric tubes. The powders are injected with the carrier gas in the inner tube. A schrouding gas is injected in the annular space between the inner and the outer tubes. The powder is confined to the vicinity of the axis, resulting in a more homogeneous thermal treatment.Tungsten powders have been spheroidized with and without this device. Using the double flow injection, the spheroidization yield has been increased from 70 % up to 95 %.The design of such an injection device has. been studied and improved using numerical modelling. Another useful tool, a visualisation technique described elsewhere, has been used for the experimental study, that drastically simplifies the comparison between experimental and theoretical results: injecting yttrium oxide into the discharge results in a colorful display of the 4000 K isothenn: the ""cold"" zone, below 4000, appearing as red, and the ""hot"" zone as blue. Furthermore, it is of great industrial interest since it is a very cheap and efficient way to obtain a picture of an important isotherm."

Jan 1, 1999

By Fathi Habashi

Laboratory autoclaves for hydrometallurgical investigations are available in a variety of sizes, models, and materials of constructions. They vary in sizes from 25 mL to 2 liters for laboratory studies and 5 to 50 gallons for pilot plant work. They are essential tools for studying aqueous oxidation of sulfide concentrates, dissolution of oxide minerals at high temperature and pressure and hydrothermal precipitation reactions. The maximum pressure and temperature at which any pressure vessel can be used will depend upon the design of the vessel and the materials used in its construction. Since all materials lose strength at elevated temperatures, any pressure rating must be stated in terms of the temperature at which it applies. A review of existing models and their accessories will be given.

Jan 1, 2000

By Xi-Shan Li, Qian Li, Yong-bin Yang, Li-na Cui, Tao Jiang, Jie Ge

"With regard to control environment pollution in the roasting pretreatment of sulfur & arsenic-bearing gold concentrate, roasting of double-layered pellet was proposed. In the paper, the characteristics of double-layered pellet roasting were studied. Removal and solidification rates of sulfur and arsenic were investigated as primary factors. The result indicated that the removal and solidification rates of arsenic reached up to 95.91 % and 98.95% while the sulfur was 97.19% and 97.90% respectively on the premise of adopting slaked lime as solidified agent at temperature of 6000, the package proportion of 2.14 and roasting time of 3h. However, pyrite and arsenopyrite were transformed to hematite and magnetite and product of solidification mainly consisted of calcium sulfate, calcium arsenate and calcium sulfite within optimum roasting parameters.IntroductionUtilization of refractory gold resources has been gradually concentrated on with the depletion of the gold resources which are easy to deal with in the world [1]. Sulfur and arsenic-bearing gold ore is a typical refractory gold one, in which ultrafme gold is encapsulated in the structure of metal sulfide minerals [2,3], so it gives poor recovery through direct cyanide leaching. These refractory ores need pretreatment before the process of cyanide leaching to undermine lattice structure of pyrite and arsenopyrite containing gold [4] so that the gold could touch with cyanide solution [5]. Among various methods of pretreatment, conventional roasting method is most effective, but this process generates gases such as S02 and As203 harmful to environment. Therefore solidification roasting was proposed to solve this problem occurring in the conventional roasting at the end of last century."

Jan 1, 2013