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By Pedro Lobarinhas

In the present work a two dimensional computational model is derived for the description of the time dependent heap leaching process. The flow inside the heap is calculated using the diffusion equations for the flow in porous media. The soil conductivity is also estimated assuming a close packed structure for the grain packing inside the heap. These equations, with appropriate boundary conditions, are solved using a time step splitting scheme. From this calculation the amount of leaching reagent in contact with the ore at any position inside the heap can be calculated and, once coupled with appropriate reaction equations, the amount of metals extracted can be computed and leaching agent concentration updated. The model is tested with available experimental data and the results have shown to be in a very good agreement. The model predicts all the transient features of the data.

Jan 1, 1999

By Hubert Bril, Priscilla Pareuil, François Bordas, Emmanuel Joussein, Jean-Claude Bollinger

"According to the legislation, valorization type, origin and characteristics of waste material, various standard procedures are available to evaluate environmental impacts. A Mn-rich slag was sampled from a metallurgical plant. After its characterization (elementary analysis and mineralogy), five standard procedures were carried out (i.e. TCLP, EN 12457-1). Each fixed parameter of the standards was systematically studied in a large range: pH, Liquid/Solid ratio, contact time. For example, EN 12457-1 led to a low ME mobilization, increasing with the L/S ratio, the contact time and an acidic pH. As a conclusion, the representativeness of the considered parameters and their potential variations are predominant to assess of the real environmental impact during slag reuse. Introduction Recent studies have been carried out about environmental impacts of waste containing metallic elements (ME) because of their potential mobility [1-7]. Indeed, slags are either dumped or valorized in various activities such as building materials. In order to assess environmental risk, various standard procedures are used depending on country legislation, origin of waste and valorization way. Results of leaching tests are linked either to special legislation (e.g. Dumping: EC, Council Decision 2003/33/EC, Construction products: EC, Council Directive 89/106/EEC) or to legal levels used in drinking water (Directive 98/83/CE) when leachates could migrate to groundwater. If ME in leachates are lower than drinking water authorized levels, the waste will be considered as non-hazardous. On the contrary, if the leachable amounts exceed them, the question about the risk has to be posed. Beyond the abundance of leaching tests available, variety of operational conditions induced by these regulatory tests does not make the choice easier. According to operational conditions induced, ME release could vary from one test to another one. ME concentrations in leachates depend on pH, Liquid/Solid ratio, contact time and particle size [3]. To highlight the importance of these operational parameters, potential risk for valorization of a manganese-rich slag was assessed by comparing several standard leaching protocols [8-12] with a global study dealing with the influence of operational conditions. For each regulatory protocol, the most influential parameters (L/S ratio, pH, particle size and contact time) have been studied in a large range."

Jan 1, 2008

By Marcello M. Veiga

Informal gold mining operations in the Amazon emit about 100 tonnes of mercury annually because of poor amalgamation practice. Lack of information and the complexity of mercury transformations hinder effective action to prevent such pollution and/or monitor its extent. In the past, mathematical equations have been formulated to deal with the correlation of natural variables and mercury in biota but often, the error range is too great to provide useful models. Projection of physico-chemical variations in an environment subjected to mercury emissions onto the extent of bioaccumulation is fraught with many uncertainties and unknowns such as internal correlations between variables and the site-specific nature of biota contamination. Often assumptions about closed systems are invalid when applied to natural environments. This work presents a heuristic approach to this problem in which amalgamation methods and natural variables are dealt with using an IF-THEN rule-based system that concludes about levels of emission and risk of bioaccumulation. The system is able to handle uncertain or vague data and yet still provide useful output. Belief in mercury oxidation or dangerous conditions are examined using Fuzzy Logic techniques and Inference Equations. These belief levels are derived from thermodynamic equilibrium data together with field observations of natural variables. This procedure can reduce the need for sophisticated analytical equipment and can provide information and diagnosis to non-technical people.

Jan 1, 1994

By C. Cánepa

In the treatment of many problems related with the optimization of a given ore dressing process, microscopic studies can provide invaluable assistance. Such studies are generally carried out through mineralogical determinations both qualitatively and quantitatively. Frequently the solution of a specific problem requires the combination of these in adequate proportions. Often the nature? of the problem poses some conditions regarding the way the microscopic determinations are made in order to yield useful information. Most publications applied to mineral beneficiation show results of ore microscopy without mentioning the methodological details involved in the determinative work and therefore it is not possible to judge their reliability and/or their relevance. As methodology must necessarily change from case to case, it is very important for the microscopist to identify first the direct and indirect mineralogical information required to solve the problem. Without such guidelines selection of methods for the qualitative and/or quantitative determinations cannot be made.

Jan 1, 1981

By Daowu Yang, Zhuo Ren, Hui Liu

"In this paper, the photochemical catalysis degradation effect of photocatalyst obtained by charcoal-supported nano TiO2 (nano TiO2 / charcoal) on the formaldehyde in the air was studied. The influences of the nano-TiO2 loading and the photoreactor structure on the efficiency of photochemical catalysis degradation of formaldehyde was reviewed.The nano - TiO2 / bamboo charcoal adsorption of formaldehyde, as well as the influences of a certain amount of formaldehyde after adsorption on its photochemical catalysis effect were discussed. The sol preparation process of Ce-doped nano-TiO2 was described. Experimental results indicated that: the surface of bamboo Charcoal still has a strong formaldehyde adsorption capacity after Supported by Nano TiO2.After adsorbing formaldehyde, the photochemical catalysis degradation efficiency of formaldehyde of the catalyst at a steady state is basically the same with new prepared catalysts’. When the thickness of the catalyst layer of the multi-ladder-type structure photoreactor is 2mm, the interval is 20mm, the absorption efficiency of formaldehyde of Nano- TiO2 / bamboo charcoal is the best . Nano-TiO2 undoped Ce responded with no degradation of formaldehyde after 2 hours, while the degradation rate of formaldehyde of the Ce-doped nano- TiO2 reached 15% 2 hours late, and the formaldehyde decontamination of the equipment reached 94%.IntroductionEmerging out of home decoration in the distribution of formaldehyde, benzene, ammonia and other indoor pollutants have been proved to be very harmful to the human body. Photocatalysis can eliminate air pollutants, in particular, can effectively degrade the air volatile organic compounds, it is a new method of air purification developed in recent years. the biggest advantage of photochemical catalysis degradation is green, this method can be available at normal temperature and pressure to degrade formaldehyde and other organic matter into carbon dioxide and water without secondary pollution.Nano-TiO2 have become the most studied photocatalyst due to its stable, non-toxic harmless, superior photochemical catalysis properties [1]. Initially nano-TiO2 powder was used as a photocatalyst, but it’s difficult to recover and easy to wear and tear [2,3]. Later, the TiO2 was used in the form of film loaded on some carriers, such as glass beads [4]. As the photochemical catalysis reaction occurred on the catalyst surface, only the organic matter adsorbed on the catalyst surface can be degraded, so the catalyst was requested that must have a strong adsorption. Combined the adsorption properties of bamboo charcoal and the photochemical catalysis activity of nano-TiO2 together. Made the photocatalyst by loading the nano-TiO2 on bamboo charcoal to degrade organic matter in the air. Nano-TiO2 semiconductor photocatalyst has a strong catalytic oxidation due to the photo generated hole of the surface [5,6],and has a potential application. Some studies have shown that nano-TiO2 photocatalysis activity can be increased by doping certain metal ions [7,8].The aim of our work in this study was to use bamboo charcoal load Ce-doped nano-TiO2 photochemical catalysis oxidation to degrade formaldehyde,and design a multi-ladder structure photoreactor, also prove the availability of the device from the theoretical and experimental."

Jan 1, 2011

By Lucas Lopes da Costa

In this work, a natural foam extracted from the Amazon buriti palm tree is investigated as possible substitute for synthetic foams. The basic physical and mechanical properties of this biofoam were evaluated. Its sponge-like structure was characterized by the amount of pores and morphological aspects. It was found that the buriti biofoam displays a very low density of the order of 0.1 g/cm3 with a relatively good compressive strength. This would be suitable for several engineering applications and as a new material with the potential for replacing currently applied synthetic polymeric foams.

Jan 1, 2010

By Abbas H. Mirza

Arsenic and selenium are found in low quantities together with other metals in several nonferrous metallurgical process streams such as scrubber blowdown solution, acid plant wastewater, gas cleaning plant water, etc. Normally, the other metals in these streams are present as cations and can be precipitated by conventional lime treatment and sulfide polishing. However, arsenic and selenium are invariably present as anions, AsO33-and AsO43 in the case of arsenic and SeO32 and SeO42 for selenium. Conventional lime treatment removes most of the arsenic, but it does not remove selenium. The present paper reviews the processes and technologies developed to date on the removal of arsenic and selenium from metallurgical process streams.

Jan 1, 1996

"Mechanical alloying (MA) synthesizing technology and thennohydrogen processing (THP) were utilized to produce nanocrystalline Ti-MMC's reinforced by TiB intermetallic compound by using TiH2-B powder mixtures. Powders MA'ed up to 8 hours were examined by X-ray diffraction and SEM study. All MA'ed powders afterwards were HIP'ed at 700, 800 and 950EC for 1 hour. Detailed XRD, SEM and TEM study of the samples were carried out to determine the structure and micrography of the Ti-TiB MMC material processed by MA+THP approach followed by HIP'ing at high temperatures.IntroductionThe fiber reinforced titanium base composites [1,2] which possess a great resistance to high temperature have been investigated. In these studies fibers of C and SiC were used as reinforcing materials. However, these fibers react with Ti-matrix at elevated temperature resulting in product formation at the interface between the matrix and the fiber. Because of the chemical reactions, strength of the product MMC material diminishes.In conventional techniques of whisker reinforced composite material production, the mixtures of matrix metal powders and dispersed fibers are consolidated by hot pressing, HIP and/or hot extrusion. These techniques, however, have some shortcomings. Hard and brittle fibers could be broken during mixing cycle of the processing. Consolidation techniques could also be the cause for fiber breakdown. Attaining of the uniform dispersion of fibers into the metal matrix is not an easy process. The chemical reactions at elevated temperature exposures in the interface between the matrix material and fiber reinforcement cause product formations leading to poor mechanical properties."

Jan 1, 1998

By He Zhi-jun, Ning Zhe, Pang Qing-hai, Zhang Jun-hong, Zhan Wen-long

In this study, Raman spectroscopy was utilized to investigate the evolution of char structure in pulverized coal (PC) during microwave irradiation. The results indicated that though microwave treatment was carried out at low powers of 132W or 264W, significant variation in char structure was still observed. Char structure turned out to be more irregular firstly under microwave irradiation. However, char structure of superior regularity was obtained with the extension of irradiation time. It can be conclude that short time microwave treatment may facilitate the chemical activity of coal, while long time microwave irradiation on PC may deteriorate its combustion or pyrolysis property.

Jan 1, 2016

By R. M. Taylor

Lime addition to acid mine drainage (AMD) leads to precipitation, predominantly of metal hydroxides and calcium sulfate, and is the benchmark for remediation by precipitation. Geo2 Limited of Melbourne, Australia has developed and patented a novel alternative precipitation scheme based on the formation of mixed valency, M(I1)-M(III), hydroxide sulfate salts. When the composition of AMD is appropriate, the Green Precipitate Process provides a useful and more effective alternative to conventional liming. The characteristics and utility of the Green Precipitate Process are described in terms of the underlying chemistry, and a case study where the Green Precipitate process outperforms conventional liming. A mobile pilot pipe reactor rig which was built by Geo2 to demonstrate the process, and used successfully in both Australia and the United States, is described.

Jan 1, 1998

By Rafael Colás

Computer visualization can be employed in industry as an aid to the understanding of the complex interactions between variables encountered in production. The examples of ingot casting of rimming steel and that of hot rolling of low carbon steel strip are presented. Both processes are mathematically modeled, and their results are presented in a graphical way. Such models have been proven to be an asset in quality improvements and increase of productivity as the personnel involved get a better understanding of their job.

Jan 1, 1993

By Nathaniel R. Quick

"Nd: YAG, KrF excimer, and Cu-vapor lasers are used in air to synthesize conductors and semiconductors as a second phase in silicon carbide and aluminum nitride. Conductor resistivities as low as 104 O-cm are formed in these substrates; the resistivities for the untreated substrates range from 10 11to 1014 O-cm. The silicon carbide conversion is relatively independent of wavelength while the aluminum nitride conversion shows a dependence on wavelength over the range 248 nm to 1064 nm. Silicon carbide conductors, evaluated over the range 15 K to greater than 300 K, exhibit metal like conductivity; resistivity increases with temperature. Silicon, carbon, and oxygen are identified as the principal chemical species associated with the conductor in SiC substrates while aluminum, nitrogen, and oxygen are identified as the principal chemical species associated with the conductor in aluminum nitride substrates. The silicon carbide system, which has the less complex phase diagram, is evaluated in more depth to explain the synthesis mechanism. Oxygen was principally on the surface and increasing SiC conductivity is associated with decreasing spacing between 5 µm, or less, diameter carbon globules. This technology is proposed as a replacement for metallization in electronic packages, sensors and devices. INTRODUCTIONCeramics are commonly used for multichip module, hybrid and multilayer electronic packaging; semiconductor device and sensor applications because of the insulating, conducting, semiconducting, or superconducting properties that these materials possess (1,2) The majority of ceramics, however, have not been known to exhibit conductive or semi conductive properties when exposed to rapid thermal heat processing. A ceramic and process which through selective conversion can combine two or more of these electrical properties to eliminate the need for metallization is of interest to both the commercial and military sectors."

Jan 1, 1994

By Takeshita. Takuo

"In this work, the progress of the HDDR process is discussed mainly on the Nd-Fe-B magnet system. There are three technologies being used for the Nd-Fe-B permanent magnet production; the sintering technique, the rapid quenching annealing and the HDDR process. The HDDR process utilizes· the HDDR phenomenon, in which hydrogen absorbing intermetallic compounds go through as they are heated in hydrogen atmosphere, Hydrogenation - Decomposition Desorption - Recombination. In the HDDR process, these four steps in the HDDR phenomenon are processed by choosing suitable reaction conditions regarding to hydrogen gas pressure, temperature, rate ·of desorption and etc., and we can produce permanent magnet powders of good magnetic properties with microstructures consisting with sub-micron size crystalline grains. In the anisotropic magnet powders, the sub-micron size crystals are being mostly aligned in the crystallographic c-axis direction. Possible applications of the HDDR process to other systems are also discussed.Microstructures of the Nd-Fe-B Permanent MagnetsIt is well known that magnet properties of magnetic materials are very sensitive to their microstructures [l]. This is seen in almost all magnet materials from soft magnetic materials and hard magnetic materials to magnetic memory materials. In this regard, the production technology is very important for the control of microstructures of permanent magnets The Nd-Fe-B magnet is the most powerful permanent magnet as a practical permanent magnet, and its coercivity force is much dependant on the microstructure as is the case for other permanent magnets."

Jan 1, 2000

By K. Noda

Tamano Smelter of Hibi Kyodo Smelting Co., Ltd. started its operation adopting the Flash Smelting Furnace with Furnace Electrodes (FSFE). Thereafter, it developed a coke combustion technology based on C() concentration control, which made possible a low cost and high productivity operation without using electrodes. However, increase of treated concentrates and upgrading of matte grade for production expansion started to cause difficulties in operation control with then existing operation control system. This paper outlines recent improvements for stable operation of the Tamano Type Flash Smelting Furnace (T-FSF), such as computer aided operation guide system.

Jan 1, 2001

By Kazuteru Tozawa

Surface tension, density and viscosity coefficient of acidic copper sulfate solutions simulating electrolyte solution for electrolytic production of copper have been measured and are summarized as a function of the solution composition and temperature. Nickel sulfatc is taken to be a representative coexisting sulfate that affects the physical properties of the copper sulfate electrolyte solution. The sulfates in the solutions, including sulfuric acid, increase the physical properties under consideration. Gelatin, representing organic additives for electrolyte solution, was found to sensitively affect the surface tension of the solution at low concentration of up to 200mgIL. The surface tension was markedly lowered by the addition of gelatin and the increasing concentration of gelatin led to a more pronounced decrease in the observed values. The surface tension gradually increases with time after addition of gelatin and the increase is enhanced by higher acid concentration and higher temperature. The observed change in the surface tension is considered to reflect the preferential adsorption of gelatin to the bubble-solution interface and the decomposition of gelatin due to hydrolysis to form various molecules having smaller molecular weights.

Jan 1, 2003

By den Bulck A. Van

In Europe, 50% of the copper originates from recycling. High-Cu containing scraps are regularly rich in impurities like Fe, Ni, Sn and Pb. Many high-Cu containing scraps are fed directly into anode-furnace casting installations or furnaces with limited refining capability. The impurities levels of the anodes produced in these processes should however remain acceptable for further electro-refining. The distribution of Sn between copper and slag has been investigated for conditions relevant to copper converting. Unlike previous studies, this work focuses on the behavior of Sn relevant to fire refining conditions, which are essential for anode refineries.In this study, liquid Cu–1Sn and CuOx–FeOy–SiO2 slag, with CaO additions, were equilibrated at 1300 °C in vacuum sealed SiO2 ampoules. After metal–slag equilibration, the samples were quenched in water. The composition of the slag and Cu metal was investigated with Electron Probe X-ray Microanalysis. The distribution coefficients of Sn between slag and Cu metal were determined as a function of slag composition.

In the new flowsheet for Inco Limited's S02, Abatement Project at the Copper Cliff, Ontario operations, a copper/nickel sulphide flotation concentrate will be flash smelted, then converted to Bessemer matte. As in current practice, this will be slow-cooled and separated into components by magnetic separation and flotation. The copper content will emerge as a chalcocite concentrate (impure Cu2S), containing some nickel. This copper sulphide will be converted to copper metal.

Jan 1, 1993

By R. G. Reddy

The effect of solid particles on viscosity behavior of Na2O-O-B2O3-SiO2 melts of composition XSio2/XNa2o =0.5 and in the temperature range of 900- 1150 K was studied. Samples were analyzed by X-ray diffraction and optical microscopy. The results showed that a crystalline phase (NaBO2) was formed and its amount increases with decrease in X,, from 0.50 to 0.25. The experimental viscosity values were compared with the predicted values using our viscosity model developed earlier. At low temperatures, for low content of B2O3 , the experimental values exhibits a large deviation from the predicted values. It was concluded that the deviation was due to the formation of solid particles in the molten slags. The existence of these solid particles increased the viscosity values significantly. A new viscosity model was developed to include the effect of solid particles.

Jan 1, 1993

By Edward P. Hagarty

The Hazardous and Solid Waste Amendments (HSWA) of 1984 added Subtitle I to the Resource Conservation and Recovery Act (RCRA), authorizing the Environmental Protection Agency (EPA) to develop and implement a new regulatory program for Underground Storage Tanks (USTs) containing petroleum and other regulated substances. Technical standards required for release detection, prevention, and correction as necessary to protect human health and the environment were promulgated as described in 53 Federal Register 37082 (September 23, 1988). Virginia State Regulations (VR 680- 13-02) and U.S. Army Regulations require that a Corrective Action Plan and a Site Clearance Report be prepared to explain the details of remediation of any contaminated media. Construction of new buildings is proposed in two different areas at Fort Myer in Arlington, Virginia, where USTs containing gasoline, diesel and heating oil were located. Tightness testing performed on these USTs in September 1991 indicated that some of the tanks were leaking. Many of the tanks were removed for permanent closure. Initial Abatement (excavation of contaminated soil) was &ed out immediately. A detailed Site Characterization Study which included Hydropunch", field screening using immunoassay, and pilot test - dual phase (water and soil gas) extraction was conducted. Environmental media were analyzed for volatiles, semi-volatiles and metals. A detailed risk analysis (RA) was performed to determine risk-based clean up levels for benzene, toluene, ethylbenzene, xylenes (BTEX); polycyclic aromatic hydrocarbons (PAHs); and methyl-tertiary butyl ether (MTBE). The RA also discussed the presence of lead in the soil. Before constructing any buildings in these contaminated areas, remediation must be conducted in accordance with the State, Federal and other applicable regulations. The remedial alternatives evaluated included Vapor Enhanced Groundwater Extraction, Soil Vacuum Extraction, Soil Washing, Soil Steaming, Active and Passive Ventilation SolidificationlStabilization, Vapor Barrier Construction, and Excavation with Off-site Disposal. This paper discusses: (a) delineation of soil contamination @) risk analysis (c) evaluation of remedial alternatives and selection of the most appropriate technology and (d) consideration of various regulatory issues.

Jan 1, 1994

By R. J. Kuczynski

The U.S. Bureau of Mines Reno Research Center operated a batch pilot plant to demonstrate high-temperature cyanide leaching for recovering platinum group metals (PGM) from automobile catalysts. Approximately 1,600 kg of used pellet, monolith, and metal support catalyst containing 1,680 g (54 tr oz) of PGM were processed. Forty-five-kilogram batches of used catalyst were leached with sodium cyanide solution at 160° C for 1 h under basic conditions in a countercurrent processing sequence to dissolve the PGM. Extractions from the used pellet catalyst ranged from 94 to 95 pct for Pd, 95 to 97 pct for Pt, and 64 to 81 pct for Rh. Extractions from the used monolith catalyst ranged from 7B to BB pct for Pd, 75 to 90 pct for Pt, and 43 to 71 pct for Rh. Heating the pregnant leach solutions to 275' C for 4 h destroyed the PGM-cyanide complexes, resulting in over 99.7 pct of the PGM precipitating from solution. The PGM precipitate was predominantly a powder metallic concentrate, typically analyzing greater than 50 pct PGM. Heating destroyed cyanide to less than 0.2 mg/L. Both the pellet and monolith residues were evaluated for disposal using the EPA Toxicity Characteristic Leaching Procedure.

Jan 1, 1995