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By J. M. Tourre

Recently, interest in rare earth based oxide powders for electronic applications has risen dramatically. Considerable research has been devoted to the chemical synthesis of these compounds to improve the control of physical and chemical characteristics of the powder. In most cases, a high degree of homogeneity, purity and reproducibility is necessary in order to obtain good application properties. The synthesis parameters can control particle size, surface area, and morphology as well as the degree of homogeneity and application properties. Rhone-Poulenc, a world leader in the production of separated Rare Earth chemicals has developed a flexible process to produce a wide variety of compounds. The different processes for the synthesis of YBa 2Cu 3 O 7 will be discussed and compared to the RP process in term of product quality, cost and flexibility.

Jan 1, 1992

By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2SiIMgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (PIM) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2um is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ fonning process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm3 and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

By Cody Burcher-Jones

The recovery of rare earth elements (REEs) through heap leach/in situ techniques from so-called ion adsorption clays (IACs) is attractive due to their inherent simplicity. However, the underlying mechanisms of these processes are poorly understood. In this study, the deportment of REEs in a typical IAC material has been investigated and was found to concentrate in the phyllo-layers of the clays, especially hallyosite, and was readily desorbed by various ion-exchange reagents indicating various potential routes to liberate them. Here we are reporting the use of seawater (0.5 M NaCl), spiked with various amounts of (NH4)2SO4, and found better extraction using a reagent mixture than NaCl on its own. Further, the leaching of REEs from a bed of clay material was investigated over time to understand the rate of transport through the stagnant material. Results indicate that REE release is likely to be controlled by diffusion through the clay material, while desorption in agitated systems is rapid. A degree of fractionation between different REEs can be observed during diffusion. Nonetheless, the successful operation of in situ leach operations for this type of material would depend primarily on how easily solution cocktails can be made to flow through the bed material.

By Peter Woodall, Paul Telford, Pengfu Tan

"Arsenic enters the Mount Isa copper circuit in the form of arsenic rich minerals in concentrates from both the Mount Isa and Ernest Henry copper mines. Arsenic is a volatile metal, and will partition in the copper smelter between smelter off gases, slag and anode. Most of the volatile arsenic will report to Isasmelt Electrostatic Precipitator (ESP) or Waste Heat Boiler dusts where it will form a re-circulating load within the smelter. ESP dust is produced at a rate of 15,000 - 20,000 t/y and is currently removed from the precipitator and leached in the new ESP Dust Recovery Plant to separate copper and arsenic from the ESP dust. This paper describes the laboratory test works of ESP dust leaching, neutralisation and cementation processes. The planttrial, commissioning and operation have been presented as well.1. IntroductionThe flue dusts generated in the process of copper smelting contain appreciable amounts of copper and other valuable metals including precious metals. These flue dusts also contain appreciable amounts of arsenic trioxide where arsenic occurs in the ore body. The copper smelters processing concentrates generate residuals, such as ESP dust, containing arsenic trioxide. ESP dust contains impurities such as arsenic and bismuth which are harmful to the copper refining process if they report to anode. These impurities are fumed off in the smelting process and report to the dust as arsenic and bismuth oxides.The content of arsenic in the feed of Mount Isa copper smelter is about 0.1 % to 0.4%. Arsenic is a volatile metal, and will partition in the copper smelter between off gases and anode. Most of the volatile arsenic reports to Electrostatic Precipitator (ESP) and Waste Heat Boiler dusts where it will form a re-circulating load within Mount Isa Copper Smelter. Unless arsenic is bled from the smelter circuit, it will build up to a point where both anode quality and smelter hygiene are adversely impacted."

Jan 1, 2011

By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2Si/MgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (P/M) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2JIm is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ forming process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm) and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

By Hiroshi Nakazawa

An acid mine drainage in abandoned Horobetsu mine in Hokkaido, Japan, contains arsenic and iron ions; total arsenic ca.10ppm, As(III) ca. 8.5ppm, total iron 379ppm, ferrous iron 266ppm, pH1.8. Arsenic occurs mostly as arsenite (As (III)) or arsenate (As (V)) in natural water. As(III) is more difficult to be remove than As(V), and it is necessary to oxidize As(III) to As(V) for effective removal. 5mL of the mine drainage or its filtrate through the membrane filter (pore size 0.45m) were added to arsenite solutions (pH1.8) with the concentration of 5ppm. After the incubation of 30 days, As(III) was oxidized completely with the addition of the mine drainage while the oxidation did not occur with the addition of filtrate, indicating the microbial oxidation of As(III). In this paper, we have investigated the microbial oxidation of As(III) in acid water below pH2.0.

Jan 1, 2006

By James Bennett, Jinichiro Nakano, Anna Nakano

Previous empirical research demonstrated that by mixing gasification and metallurgical slags at a specific composition in a CO2 enriched environment, enough exothermic heat would be generated to transform CO2 to CO. The process capacity may be limited by the availability of the slags, however, it could be used to supplement existing energy or chemical production to reduce overall carbon emission. In this study, computational simulations were performed to explore optimal process conditions based on effects of individual slag constituents and thermal input for maximal gas conversion rate, heat production, and volume increase. In simulated conversions of CO2 to CO and H2O to H 2, comparisons were made by varying CaO, FeO, versus V2O3 slag constituents. The result indicated the optimal slag composition may be obtained by appropriate source selection and mixing of gasification and metallurgical slags in order to maximize carbon reduction and/or H2 production.

Mar 1, 2017

By Michael Meyer

In the past shredder fluff was discarded in landfills, but shrinking landfill space and the partly hazardous content of the fluff as well as its caloric value, all resulted in efforts to turn this waste problem into a an energy resource. In order to produce a fuel, the inorganic compounds have to be removed. Extensive analyses and particle size measurements were made on fluff from various shredder. For optimal separation all particles are reduced to a uniform, relatively small size. In a subsequent combined - screening and air classification - process, successful separation into organic and inorganic fractions is achieved. The inorganic fraction is treated in a heavy media or an eddy-current separator to recover the valuable metals, while the organic fraction is now suitable for thermal processing, such as fluidized bed gasification and using the resulting carbon as a chemical reagent.

Jan 1, 1995

By Weizhi Zeng, Michael L. Free, Sayan Sarkar, Prashant K. Sarswat

Black Phosphorus was recently discovered as a 2D material and it exemplified huge prospects for application in electronics, optoelectronics, photonics and catalysis. It is a direct band semiconductor with tunable band gap varying from 0.35 eV (bulk) to 2 eV (single layer). But the layer dependent band gap of black phosphorus restricts it to make use of the full spectra of sunlight for absorption. First principle calculations were performed using ‘Quantum Wise Atomistic Toolkit’ package with Perdew-Burke-Ernzerhof (PBE) exchange-correlation for black phosphorus doped with non-metallic dopants of B, S and Se and metallic dopants of Ti, Mg and In. It has been found that doping with non-metallic impurities result in a small diminution of the band edges (0.96–0.57 eV), whereas doping with metallic impurities decrease the band edge drastically (0.85–0.025 eV). Moreover, it was also observed that dopants with an even number of valence electrons incorporated a metallic nature of black phosphorus, whereas dopants with odd number of valence electrons further attributed to its semiconducting features. Thus in a holistic discernment, black phosphorus with the incorporation of some dopants in appropriate amounts can absorb more visible range of the optical spectra, making it ideal for use in photovoltaics.

Mar 1, 2017

By K. Alibhai

Greek laterites, which generally had nickel concentrations of < 1 %, are amenable to chemical leaching,. although there is considerable variability in the ease of leaching with different ore types. With low grade ores(< 1 % Ni content); >70% of the nickel was leached in columns with a strong selectivity for nickel over iron. Heterotrophic microbially assisted leaching could be a viable alternative to classical hydrometallurgical and/or pyrometallurgical techniques, with a very high recovery (greater than 80% ) being found with some of these mineral microbial interactions. Critic acid was probably the effective chelating agent.

Jan 1, 1991

By Ryuhei Masuda, Kenji Oosumi, Yasuhiko Watanabe, Yutaka Nagakura, Tomoya Ohzono

"In order to promote recycling of aluminum scrap, it is required to remove inclusions that have a remarkable influence upon the product quality. An internal filtration technology using a new filter, which is made by coating an adhesive on the surface of the conventional filter, has been developed as a new removing technology for inclusions.The technology has made it possible to remove inclusions as small as 10-20µm in the molten metal, which have been impossible to be removed by the surface filtration technology using conventional filter, An inclusion removal rate of up to 90% has been attained.The technology will contribute not only to recycling of aluminum products but also to the improvement in the quality of current products."

Jan 1, 2000

By A. Block-Bolten

Copper concentrates from northern Peru contain large amounts of arsenic and antimony in the form of sulfosalts like enargite, tennantite and tetrahedrite. These impurities affect up to 30% of Peruvian copper production. Under the sponsorship of the Instituto Geologico Minero y Metalurgico in Lima a project to separate copper from arsenic without pollution of the environment is being carried out at the National University of Trujillo in Peru. The U.N.T. process is unique in the respect of using .low melting salts as solvents, and sulfides of metals with high cation potential as destructors of the complex sulfosalt molecules. Laboratory scale experiments have given encouraging results but interesting and difficult problems developed on scale-up. The process is pyro-hydrometal-lurgical and under certain circumstances its economics are promising.

Jan 1, 1981

By Marcelo A. Martorano, Moyses L. Lima, João B. F. Neto

"Directional solidification is an essential refining step to obtain solar grade silicon from metallurgical silicon. This step can be carried out in a Bridgman furnace, where nearly constant temperature gradients and solidification velocities are imposed on the solid-liquid interface. In the present work, this directional solidification was conducted in a static furnace, in which large temperature gradients and low solidification velocities were enforced to increase macrosegregation. The resulting ingots were analyzed regarding their macrostructures, microstructures and chemical composition. Using measured cooling curves in the ingot as boundary conditions, a mathematical model based on the concept of a stagnant liquid layer at the solid-liquid interface was implemented to predict the macrosegregation profiles. The chemical analyses of the ingots show macrosegregation of several impurities to the ingots top. The mathematical model indicates that liquid convection plays an important role in stabilizing the planar solid-liquid interface, increasing the macrosegregation of impurities.IntroductionMost of silicon used for photovoltaic (PV) energy production is obtained by chemical processes, such as, Siemens and its derivations [1]. However, these chemical processes have drawbacks related to relatively high energy consumption and investment costs, and to safety and environmental problems. In order to overcome these difficulties and to fulfill the silicon demand for PV applications, several metallurgical routes are under development [2] to produce silicon of enough purity to PV applications (SoG-Si) from metallurgical grade silicon (MG-Si).Metallurgical routes involve different steps among which the directional solidification is pointed out as a fundamental one [1]. Directional solidification can cause macrosegregation of impurities to the last part of the ingot to solidify. The impurity segregation during solidification is related to the low solute partition coefficient (k0) between liquid and solid silicon. Most of the impurities in MG-Si have k0 << 1, except for boron, phosphorus and oxygen, which require specific steps of the metallurgical routes to be eliminated. The equilibrium partition coefficient and the solubility limits for the most important impurities in MG-Si are shown in table 1"

Jan 1, 2014

By Anette Mueller, Thomas Schnellert, Sérgio C. Angulo

"The use of automatically sorting technique, to separate gypsum components from recycled material of processed construction and demolition waste (C&DW), is motivated by environmental and economical aspects. Only if the gypsum can be separated the aggregates can fulfill the environmental requirements and also the structural characteristics according to the standards. Furthermore, the separation of red brick can also improve the quality of the aggregates.This paper aims at analyzing the separation of gypsum components and red brick by using the color sorting technique. The impacts on the composition and the envelope density of recycled aggregates are described. Depending on the gypsum content the application of two processing stages (rougher-cleaner) can be necessary to produce aggregates with sufficiently low gypsum content. Additionally, the separation of red brick and concrete is successful. So, the color sorting may be a promising technique to upgrade the quality of mixed C&DW aggregates.IntroductionConstruction and demolition waste (C&DW) is a mixture of different materials. Such mixtures can be used only in low grade applications. If the material is used as certified material for road construction or as aggregate in concrete the concrete particles must be separated from the other building materials. This paper aims at analyzing the separation of gypsum components and red brick by optical sorting. The needed stages of sorting for getting a product quality according to the German Standards are deduced.Gypsum is a building material that is increasingly used for interior works in Germany like it is shown in figure 1 [1]. At present the content of gypsum in C&DW is estimated at about 1 %. Assessments on the basis of material streams of gypsum and concrete and their life spans show that higher gypsum contents of about 3 % must be expected in future [2]. Also in other countries the use of gypsum has grown considerably in the last decades. From the characterization of C&DW available in some cities in Brazil, 4 to 15 % of total amount of C&DW that may arrive at the recycling plant to be processed is excessively contaminated by gypsum. In one of these cities, the average content of gypsum in the C&DW before processing was as high as 2.1 % [3]."

Jan 1, 2008

By Hiroyuki Sano, Chikabumi Yamauchi, Mitsuru Tanahashi, Toshiharu Fujisawa, Shin-ya Iwahori

"Pyrometallurgical process using Cu2O-based slag was proposed as a recycling process for copper scrap. However, it is difficult to remove nickel from copper by oxidative refining. Therefore, it is necessary to reduce the concentration of nickel in copper before the oxidative refining. In the present work, the copper enrichment stage in this recycling process, where copper scrap melt is separated into the Fe-C-Cu melt and the molten copper, was taken up and the compositions of both melts were measured. Based on the above results, the distribution ratios of nickel between the Fe-C-Cu melt and the molten copper were calculated. Furthermore, the optimum condition of copper enrichment stage was discussed from the viewpoint of nickel removal and copper recovery. The possibility of recovering 4N-purity copper by using this recycling process was confirmed.IntroductionRecycling is well known as a method for saving resources and reducing environmental damage. More than 99% of copper is used in metallic form - as metal or copper alloys[l]. High-grade copper scrap is directly re-melted and reused, while low-grade copper scrap is transported to copper smelters to be pyrorefined and electrorefined. Nevertheless, a great amount of copper is being stockpiled in the cities and should be recycled in the near future. At that time, the current recycling process will face new problems due to the increases in the recycling rate to the smelters. This includes insufficient combustion heat to melt copper scrap and ·almost no benefit in electrorefining because the scrap does not contain gold and silver. Thus, an alternative pyrometallurgical method for copper scrap refining will be required."

Jan 1, 2000

By Shengli Wu, Wei Huang, Xinliang Liu, Kaifa Zhang

The slagging behavior, the phase of primary blast furnace slag and its transformation law of structure for the single furnace burden were studied in this paper. The results showed that the formation of primary slag was controlled by CaO/SiO2, Al2O3 content, MgO content, reducibility, iron content and porosity of the furnace burden. Fayalite (2FeO•SiO2) was easily formed from acid ferrous furnace burden while kirschsteinite (2(Fe,Ca)O•SiO2) was produced from alkaline ferrous furnace burden

Jan 1, 2015

By M. I. Kalashnikova

Gipronickel Institute has developed the technology of treatment of difficult to concentrate sulphide Pb-Zn concentrates (Zn-19,9%, Pb-8,4%, Cu-0,34%, Fe-8,8%, Ba-6,8%, S-18,7%, Ag-106 g/tonne). The technology consists of pressure leaching, impurity removal from leaching solution, electrowinning and Pb-Ag containing cake treatment. Despite low zinc content in initial concen-trate the technology allows production of solution which is suitable, after standard procedure of impurity removal, for electrowinning with production of zinc grade SHG. Comparing to the standard technologies the flowsheet developed provides the lesser expenses per zinc unit because of decreasing of liquid to solid ratio at pressure leaching stage. The initial concentrate is characterized along with low content of principal metals by high con-tent of barite, which makes flotation of pressure leaching residue more difficult. That is why in this case the hydrometallurgical treatment was chosen. At optimal parameters of chloride leach-ing found during laboratory experiments the principal components extraction was 99.5% for Pb and up to 92% for Ag.

Jan 1, 2006

By R. W. Hammack

Results for the treatment of a problematic mining wastewater using bacterial sulfate reduction (BSR) are presented. Specifically, a BSR pilot treatment plant (250 L per day) was used to treat Berkeley Pit simulant to discharge standards with the selective recovery of separate Cu- and Zn-sulfide concentrates. Concentrates recovered in these tests contained greater than 50 % of the target metal and met specifications for sale to existing smelters. The biological component of the treatment was found to be surprisingly robust. Scaling and solid/liquid separation problems were encountered but considered normal for sulfide treatment. For Berkeley Pit water, capital costs for BSR treatment was found to be comparable to high-density sludge lime treatment. The value received from the sale of recovered copper ands zinc concentrates paid for all the operating costs.

Jan 1, 1999

By D. L. Stewart

"Melt loss is usually one of the highest individual cost items in the operation of ah ingot casting facility. While melt loss and the resulting cost for the entire facility is usually well known (at least via standard cost accounting), dross generation and melt loss for individual unit operations within the plant are usually not known. Thus, the financial impact of various practices, alloys and scrap types is not known. Development of an accurate, relatively low-cost technique for measurement of melt loss at commercial scale would aid in understanding melt loss for existing units, as well as evaluation of the melt loss impact of alternate processes.This paper will describe a methodology developed at Alcoa for accurate and inexpensive measurement of melt loss at commercial scale. The methodology has been used to evaluate the impact of scrap type, melting practices, and dross treatment technology on melt loss."

Jan 1, 2000

By T. V. Jayaraman

Fe-Ga alloys, with compositions around 27.5 at % Ga, can be heat treated to obtain ? (ordered bcc), DO19 (ordered hexagonal), and L12 (ordered fcc) ordered structures. Our earlier work using polycrystalline samples had shown that magnetostriction is strongly influenced by ordering in this alloy. Here more detailed study of the correlation between ordering and magnetostriction using single crystals of Fe 27.5 at. % Ga alloys is reported. Single crystals of Fe 27.5 at % Ga were grown using Bridgman single crystal growth technique. X-ray and electron diffraction were used to study the ordering in this alloy. Magnetostriction measurements were carried out at no load conditions. Elastic constants were measured using Resonant Ultrasound Spectroscopy.

Jan 1, 2006