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By N. Verbaan, E. Bourricaudy, M. Dry

"Starfield Resources is developing a novel circuit for the recovery of nickel, copper, cobalt, iron oxide, sulphuric acid and precious metals from the Ferguson Lake deposit in Nunavut, Canada. In this deposit, pentlandite is too finely disseminated in pyrrhotite for the production of a smelter-grade nickel concentrate at an acceptable nickel recovery, so established technology is not applicable and a novel chloride-based circuit is under development. The enabling aspect of this circuit is the hydrolysis of ferric chloride to hematite, releasing gaseous hydrochloric acid that is recycled. Conventional steps are used for separating and recovering the valuable metals from the chloride solution generated. This paper briefly outlines the circuit and presents the results of experimental work on the enabling steps, viz. the oxidation and hydrolysis of iron chloride to hematite and gaseous hydrochloric acid.IntroductionThe Ferguson Lake bulk sulphide ore body in Nunavut, Canada, owned by Starfield Resources Inc., contains significant amounts of base and precious metals but its mineralogy is such that it is not amenable to conventional processing. Pentlandite, for example, is too finely disseminated in pyrhhotite for even modem techniques such as fine grinding and improved flotation reagents to be effective [ 1] and extracting the value requires processing the entire bulk sulphide, including the pyrrhotite. To give the project a total green footprint, in terms of both carbon emissions and acid rock drainage, Starfield imposed the following requirements:• No reactive tailings to generate acid rock drainage.• No gaseous emissions other than normal atmospheric constituents.• No liquid effluents.• No regular consumption of fossil fuel.• High recoveries of all the valuable metals."

Jan 1, 2011

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 Dariusz Kopyci ski, Józef Dorula

The study proves that by introducing the iron powder and disintegrated steel scrap to low-sulphur cast iron still before the inoculation carried out with a conventional graphitising inoculant, the mechanical properties similar to those obtained during the inoculation treatment carried out on cast iron with the recommended high sulphur content are achieved. The said operation increases the number of crystallisation nuclei for dendrites of the primary austenite. In this case, the iron particles act as substrates for the nucleation of primary austenite, due to a similar crystallographic behaviour of the regular face centred cubic lattice The more numerous are the dendrites of primary austenite, the less free space is available in the interdendritic spaces for the formation of graphite eutectic grains, which makes the structure more refined (more eutectic grains) and the mechanical properties higher.

Jan 1, 2016

By T. Shimizu

In Japan, the emission standard of selenium in effluent was set at a maximum of20 mgll in Feb. '94 for the first time, and it is scheduled to be further decreased to a maximum of 0.1 mg/I from Feb. '97 due to tightening of the Water Pollution Prevention Act. Selenium (IV) and (VI) are generally found in effluent from precious metals refineries. Although selenium (IV) can be easily eliminated by some reducing agents, selenium (VI) is more difficult to be reduced. Therefore, many smelters are having difficulty in complying with the new emission standard. At Mitsubishi Materials' Naoshima smelter, the behavior and the elimination of selenium in effluent have been extensively investigated. As a result, it was found that two strategies were particularly effective. One of them is improving the overall operation of precious metals refinery, that is, feeding uniformly the effluent to the waste-water treatment plant, reducing the effluent volume by recycling and recovering more selenium (IV) in the effluent. The other is eliminating selenium (VI) in the effluent from the precious metals refinery. It was found that selenium (VI) can be effectively reduced by using hydrazine under high? sulphuric acid concentration and high temperature conditions. By using these measures, it is considered that Naoshima Smelter will be able to comply with the new emission standard.

Jan 1, 1996

Today’s world relies upon advanced green technologies that are made of critical elements with unique properties. Examples include rare earth elements (REEs) that are critical in the manufacturing of wind turbines and electric/hybrid vehicle batteries, key components of a greener future that face supply uncertainty and near zero recycling. To tackle their supply challenges, activities have begun for urban mining from waste electrical and electronic equipment (WEEE) that contain considerable amount of REEs, but their current level of recycling is less than 1%. Current recycling practices use either pyrometallurgy, which is energy intensive, or hydrometallurgy that utilizes large volumes of acids and solvents and generates large volumes of hazardous waste. In this study, we developed a novel and sustainable process to recycle REEs from WEEE, NiMH batteries in particular. The developed process relies on supercritical fluid extraction (SCFE) utilizing CO2 as the solvent, which is abundant, safe, cost effective, and inert. The effect of seven operating parameters, namely temperature, pressure, residence time, sample to chelating agent ratio, agitation rate, complex formulation, and methanol addition on REE extraction efficiency was investigated, and optimum operating conditions were determined. This work is the first to utilize a very efficient and safe process that runs at low temperature to extract metals from postconsumer products with minimum hazardous waste generation, while offering about 90% leaching efficiency for REEs. We expect our process to find widespread applicability in urban mining of REEs using green chemistry.

By Andrey Tarasov, Erki Unn, Valery Paretsky

"The stability of the markets of energy resources and labor in countries of the Baltic Sea Region including Estonia is determined to a significant degree by the use of combustible shales as fuel and their distillation resulting in generation of up to 70% of non-recyclable waste. The objective of this business plan is to substantiate the investments for establishment of a new facility in Estonia for waste-less and environmentally safe processing of fossil minerals and man-made products generated in the shale industry, as well as other hazardous wastes. The proposed facility will use a basically new waste processing technology developed in Russia - i.e., processing in sparged molten slag This technology eliminates any release of harmful pollutants to the environment and a facility using this technology does not require, therefore, any sanitary protection zone.IntroductionIn the Baltic region, and first of all in Estonia and some other European territories, there are large natural deposits of combustible shale, which due to the lack of other own resources of energy and hydrocarbons for the chemical industry is burned and distilled with low technical and economic efficiency generating large amounts of toxic and highly toxic wastes and intermediate products. Currently, the penalties for disposal of such wastes have grown to such an extent that shale burning and distillation might become unprofitable. This might result in suspension of the given operations, which in turn will affect in an adverse way the markets of energy resources and labor market in those countries. Furthermore, in addition to the “shale problem”, Estonia, similarly to most member countries of the European Union, faces the challange of environmentally safe processing of highly toxic wastes, such as municipal solid wastes, oilpolluted materials, medical wastes and infected materials, spent rubber tires, etc. These wastes are at present stored or processed with release of a significant quantities of extremely toxic cancerogenic substances (dioxins, furans) or collected and exported for treatment at an extremely high cost and with a loss of valuable components contained in these types of waste and often with return of supper toxic processing products."

Jan 1, 2008

By G. Roderick Eggert

Material criticality reflects the degree to which a raw material is both necessary and subject to supply-chain risks. This study compares the criticality of selected raw materials from the differing perspectives of the manufacturing sectors of China, the European Union, Japan and the United States.

By Brian R. Green

Resin-in-pulp (RIP) technology has been developed for recovery of gold. It is now time to look forward to the potential for application of the technology to other situations. Some cases have been identified and have merited preliminary testwork. Four examples, which illustrate the potential of RIP, are dealt with in this paper. These include removal of metal-cyanides from pulps, recovery of manganese that is difficult to wash from filter cakes, recovery of nickel from low grade pulps, and recovery of zinc from process residues. The discussion includes descriptions of the problems, factors that affect the choice of resin, and factors that will affect the economics of the process.

Jan 1, 1998

By Zhang Jianliang, Zuo Haibin, Gao Bing, Wang Zhe

"As a result of the shortage of coking coal and the quality decrease of coke, it is important to know how to make better use of highly reactive cokes. The co-gasification behavior of highly and lowly reactive coke for blast furnace is investigated. The results show that: In the middle stage of reaction, the weight loss ratio of highly reactive coke reacted together with lowly reactive coke is higher than that of it reacted individually. However, the weight loss ratio of lowly reactive coke is lower. The weight loss ratio of highly and lowly reactive coke is almost the same as that of the weighted average. The scanning electron microscope analysis indicated that the reaction degree of surface and interior of lowly reactive coke is relatively uniform with the reaction time increased. And the reaction degree of surface of highly reactive coke is obviously higher than that of interior.IntroductionIn blast furnace iron making process, coke functions as heat supplier, reducing agent, carburizer and skeleton. With development of blast furnace iron making technology, the skeleton function of coke is becoming more and more important in requirements of large scale furnace and high pulverized coal injection. High reactivity coke is usually produced by cheap coal with bad quality, and is not good for blast furnace process. The reactivity of coke is mainly determined by the coals used, and the resource of good quality coking coal is limited and is non-renewable. In order to fulfill the need of blast furnace, a lot of research have been done to improve coal matching using new kinds of coal to enlarge resource, in which coking coal and fat coal are reduced, whereas low price coal with bad caking property are used to lower the cost, and this would inevitably increase the reactivity of coke [1-4] Blast furnace iron making would still be the main stream for a predicted future, and high reactivity coke would correspondingly be used more and more, so it has great importance to study how to use high reactivity coke in blast furnace."

Jan 1, 2013

By Afrodite Ntziouni, Vassilia Kasselouri – Rigopoulou, Athanasia Kyritsi, Konstantinos N. Pistiolas, Stamatia Gavela, Konstantinos Kordatos, Lazaros Iliadis

"The present study deals with the production and characterization of rice husk ash (RHA) and its use in the synthesis of zeolite of type ZSM-5. Rice husk was combusted in various temperatures with aim to find the suitable conditions for the production of amorphous silica. The resulted amorphous silica ash was then utilized as a starting material for the synthesis of ZSM-5 zeolite using the low temperature and atmospheric pressure process. The method led successfully to the synthesis of highly siliceous zeolite of type ZSM-5. The produced material was characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM).IntroductionRice husk is a major by-product of the rice-milling industries and it is usually used as a fuel for steam generation due to its high calorific power. During its combustion, rice husk ash (RHA) is produced. Knowing that the annual rice world production is over 615 million tons (2005), thus resulting in a potential production of more than 22 million tons of RHA [1], it can be understood that the RHA disposal is a crucial issue towards the environmental protection. However, due to the high silica content, RHA can be used as an alternative cheap source of silica for many uses, including as filler in polymers [2], concrete [3] and synthesis of zeolites [4-7].The burning of rice husk in air results in the formation of RHA with content in SiO2 that varies from 87 to 97% depending on the burning conditions, the rice variety, the climate and the geographic area [8]. Some small amounts of inorganic impurities are always present in the ash along with unburned carbon. The unburned carbon can be removed from the ash by further heating treatments in high temperatures, but this usually leads to the crystallization of the amorphous silica to cristobalite and/or tridymite [9]. The crystallization of the contained silica of the ash is also occurred when the burning conditions of husk are uncontrolled [10]. This crystallization is a disadvantage towards the preparation of silicon based materials, because the silica ash is rendered inactive in its crystalline form [11]."

Jan 1, 2008

By Ruixiang Wang, Jinhui Li, Youjun Xiao, Daoling Xiong, Hao Chen

"Leaching solution prepared from spent battery materials contains large quantities of valuable metals, such as Cu, Ni, Co, Mn and Fe. Therefore, recovery of valuable metals from acidic polymetallic aqueous solutions is of great importance for every plant. In this work, a method is introduced of recovery of Ni, Co and Mn from polymetallic solution prepared by leaching spent battery material. The basic concept includes copper was removed through replacement by iron powder followed by iron precipitation in goethite method. The experimental results show that Cu can be removed 99% at least through replacement by Fe powder, and the removal of Fe can achieve 99% by goethite method. At the same time, the loss of Ni, Co and Mn are about 2%, 3 % and 2%, respectively. The process of differential removal of metals can be selected as the treatment alternative that combines simplicity, efficiency and reliability with low capital and maintenance costs. The purified solution which only contains Ni, Co and Mn can be used to prepare NixCoyMnz ternary system precursor.1 IntroductionNickel and Cobalt are very important metals which are applied in many fields, such as energy material and support material for some new material field. The world demands for such metals is progressively increasing, while raw resources are being depleted and with the constraints raised by the Law and related legislation assigned to protect the environment from hazardous wastes in the world. Nowadays study on reutilization of waste materials has great significance for achieving secondary resources recycling and preventing environmental pollution. There are many hydrometallurgy methods applied for dealing with these wastes, while they usually contain large quantities of valuable metals, such as Cu, Co, Mn and Ni, as well as impurities, such as Fe, Zn, and etc. Therefore, proper treatment of these leaching solutions prior to their discharge is of great importance, so that the contained valuable metals can be recovered.Separation and extraction of metals from leaching solution can use some methods through solvent extraction[l,2], ion exchange[3,4], precipitation with sulfide[ 5] or alkali[ 6] and electrolytic recovery[?]. Among the appropriate treatment alternatives, replacement and differential precipitation is the most attractive treatment that combines simplicity, efficiency and reliability with low capital and maintenance costs."

Jan 1, 2011

By Matthias Schnitzler, Herbert Pfeifer, Ralf Bolling

"To transform metals high temperatures are usually needed. A fast and efficient heating can reduce the C02 emitted. The fastest way to heat metals is called direct flame impingement (DFI). The flame impinges upon the item being heated. For this method it is important to know the shape and length of the flame. Laser-induced fluorescence (LIF) technology allows measurements of a two-dimensional field without influencing the reaction or the flow. Commonly used is the measurement of OH-radicals, an indicator of the reaction zone.In the presented study measurements of a turbulent diffusion flame are shown. The position of the reaction zone and the influence of the distance between the item being heated and the burner are investigated. Conventional measurements and LIP-measurements are compared and the potential of DFI to increase the efficiency of heating metals is discussed.IntroductionDuring industrial heating processes a fast and efficient heating technology is required. Two important aspects are the NOx emission and the energy efficiency. The direct flame impingement (DFI) technology has the highest heat transfer rate possible with a gas/air flame. The turbulent high velocity flame jet impinges upon the item being is heated [ 1]. Due to the high heat transfer rate furnace and exhaust gas temperatures are lower. Therefore the energy efficiency is increased and the amount of NOx emitted is reduced.Hydroxyl- (OH-) radicals are an intermediate product that is generated during the combustion of hydrocarbons [2]. They are commonly considered as an indicator for the reaction zone and position of heat release. Figure 1 shows the hydroxyl-mole fraction in dependence of the distance along the gas flow. The figure clearly shows how fast the OH-concentration increases in the reaction zone. Figure 1 also shows that OH-radicals are present in the post combustion region, however in smaller concentration [3].The laser-induced fluorescence technology serves to measure the spatial distribution of OH-radicals in a two dimensional cross-section area of the flame. Therefore the flame dimensions and location can be determined with high spatial resolution without influencing the flow or the reaction [ 4,5]."

Jan 1, 2012

By Wankun Wang, Shixing Wang, Jinhui Peng, Zebiao Zhang

"Germanium leaching from germanium dust and fume was carried out using sulphuric acid. Response surface methodology (RSM), based on a five level, four variable central composite design (CCD), was employed to obtain the best possible combination of liquid/solid ratio (Xi: 2-10), leaching time (X2: 1-5 h), sulphuric acid concentration (X3:3.15-15.75mol/L) and leaching temperature (X4:50-90 *C) for germanium leaching. The obtained experimental data were fit to a one-order polynomial equation using multiple regression analysis and also analyzed by analysis of variance (ANOVA). The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The optimum extraction conditions were: liquid/solid ratio of 10, leaching time of 1 h, sulphuric acid concentration of 15.75 mol/L, and leaching temperature of 87.8 'C. Under these conditions, the germanium leaching extent was 65.14%, which is in close agreement with the value predicted by the model. The samples were characterized before and after leaching using X-ray diffraction (XRD).IntroductionResponse surface methodology (RSM) is one of the relevant multivariate techniques which can deal with multivariant experimental design strategy, statistical modeling and process optimization [1-15]. It is used to examine the relationship between one or more response variables and a set of quantitative experimental variables or factors. This method is often employed after the vital controllable factors are identified. It is also used to find the factor settings that optimize the response. Designs of this type are usually chosen when a curvature in the response surface is suspected [6], The process optimization of the sulphuric acid leaching of germanium from germanium dust and fume has not been reported in the literature. Hence the present work intends to assess the effects of variables such as liquid/solid ratio, leaching time, sulphuric acid concentration and leaching temperature and to identify the optimum conditions using RSM. The characteristics of sample before and after leaching are assessed using the advanced analytical instruments such as X-ray diffraction (XRD)."

Jan 1, 2012

By Yasuhiro Konishi, Kazunari Mizoe

"This paper describes a new processing of ultrafine, magnetic ferrites from sulfuric acid pickling solution in steel industry. In the ferrite processing, the iron (II) in the pickling solution was first oxidized to iron (III) by using the acidophilic thennophile Acidianus brierleyi. The bio-oxidized pickling solution was treated with solvent extraction to separate the iron (III) into the organic solution of tertiary aliphatic monocarboxylic acid. After that, the carboxylate solutions of iron (III) and other metal (cobalt) were hydrolyzed and precipitated ultrafine particles of crystalline ferrites at l90°C and l. 3 MPa for 20 min.IntroductionHot-rolled steel sheet has always a layer of oxides on its surface. The oxide layer arises as scale in hot rolling processes in steel industry, and the scale consists of the three iron oxides such as hematite Fez03, magnetite Fep4, and wustite FeO. Pickling removes chemically the scale layer that adheres to the steel surface. For normal steels, pickling is carried out in 15-20% hydrochloric acid at 60-70°C or in 20-25% sulfuric acid at 95-100°C. When steel is pickled with sulfuric acid, the scale oxides dissolve to give iron (II) sulfate.Spent pickling solutions are hazardous wastes containing a large amount of dissolved iron (II) and sulfuric acid, e.g., about 40 kg/m3 of dissolved iron (II) at pH 0. In typical commercial processes, spent pickling solution is usually cooled evaporatively to 5°C, and then to 0°C to crystallize iron (II) sulfate as its heptahydrate. After the crystallization operation, the sulfuric acid can be reused in the pickling operation.In this paper we describes a new processing of ultrafine, magnetic ferrite from sulfuric acid pickling solution, in order to recover dissolved iron (II) in the form of a valuable product. In the ferrite processing, the iron (III) was first supplied by the microbial oxidation of iron (II) in the pickling solution, and then the biooxidized pickling solution was treated with solvent extraction to separate the iron (III) into the organic carboxylate solution. After that, the carboxylate solutions of iron (III) and other metal (cobalt) were precipitated crystalline ferrites under hydrothermal conditions."

Jan 1, 2000

By Noboru Masuko, Sachiko Ono

"The structure and composition of anodic films formed on aluminum in a borate solution have been investigated by using TEM and SIMS with respect to the effect of current density and electrolyte temperature. The film is composed of a boron-containing outer layer and a boron-free inner layer with disc-like crystals present at the interface. The thickness of the film formed at constant current density up to an identical voltage, decreases with increasing current density. The thickness increases remarkably with elevated temperature. The transport number of Al3+ estimated from the thickness ratio .of the cuter to the inner layers is 0.4 when the film is formed at the current density of 20 Am-2 at 60°C. It increases slightly with increasing current density and decreases significantly with increasing temperature. Content of boron in the outer layer increases 1.5 times when current density .increases 10 times. These changes in film structure and composition with electrolysis conditions must have a significant role in the determination of electric properties of anodic alumina films as a capacitor material.IntroductionThe growth of anodic alumina film in ·a neutral electrolyte proceeds at both film/electrolyte and film/substrate interfaces giving a duplex structure. The oxide layer formed at the former interface includes electrolyte anions while a-pure alumina layer is formed at the latter interface. The thickness ratios of each layer respectively represent transport numbers of Al3+ and 0 2 - (1). The film thickness and the incorporated anion content as well as transport numbers of both ions must affect the dielectric properties of the film as a capacitor material. However, the correlation between film structure and electrolytic conditions is not fully understood (2). For the further clarification of anodic film growth mechanism, more detailed characterization of anodic films in relation to electrolytic conditions is advantageous. In the present paper, therefore, the effect of current density and electrolyte temperature on the microstructure and composition of anodic barrier films formed in a neutral borate solution was studied. The films were characterized by direct observation using transmission electron microscopy (TEM) and depth profiles of constituent elements obtained by secondary ion mass spectroscopy (SIMS)."

Jan 1, 2000

By Djalma Souza, Rubén Sánchez, Regina Maria Pinheiro, Carlos Maurício Fontes Vieira, Sergio Neves Monteiro

"This work has for objectives to characterize a waste generated in the form of sludge during the treatment of the effluent of a paper making industry and to evaluate the effect of its incorporation up to 10 wt.% on the properties of a clayey body used for brick production. For the characterization of the waste the following techniques were used: X-ray diffraction, X-ray fluorescence, differential thermal analysis and termogravimetric analysis with mass spectrometry. Specimens were prepared by uniaxial pressing at 20 MPa before firing at 750 °C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The results showed that, in agreement with the characteristics of the waste, its recycling into red ceramic can contribute to decrease the consumption of fuel during the firing stage. However, the waste changes the physical and mechanical properties, generating a deleterious effect on the water absorption and flexural rupture strength of the ceramic.IntroductionAccording to the Brazilian Association of Pulp and Paper, in the last 10 years, the global production of paper grew 35%. Brazil produced 8,2 million tons of paper in 2004 and held the position of the seventh largest world manufacturer of pulp, with about 9,4 million tons per year [1]. The pulp and paper industry generates effluents that present problems related to their disposal, even after the treatment. Among the solid wastes generated by this industry, the main waste is the primary sludge from the effluent treatment plant (ETP).After the initial treatment the decanted solids go through a dewatering stage, generating the solid form denominated primary sludge. This sludge resembles a paper paste of dark gray color when humid, and clear gray color when dry. This primary waste is composed basically of kaolin, pulp, traces of chemical substances and water. This waste generated in the pulp and paper industry depends on the characteristics of the process and of the employed techniques. It can vary significantly from one industrial unit to another, even in the case that the final products are similar. Its composition is approximately 60% of kaolin and 40% of pulp, and these percentages can vary in some moments as a function of the process [2,3]."

Jan 1, 2008

By Selvin Yesilay, Munevver Caki, Canbora Bayraktar, Bekir Karasu, Rahmi Imrak

"In this study, the utilization capability of the solid wastes taken from a commercial roof tile and brick factory in Eskisehir of Turkiye has been investigated in the production of stoneware bodies which can be formed by slip casting. At the first stage, X-ray fluorescent (XRF) and X-ray difractometer (XRD) analyses of the wastes were performed. Depending upon the results, a body recipe with an optimum casting concentration was adjusted. The bodies obtained from prepared slips were fired at 1160 oC as glazed and unglazed forms. Then, they were undergone certain tests in order to determine their firing shrinkage values, water absorption levels and optical parameters. To establish what kind of phase formations occurred after firing as a result of waste incorporations into bodies XRD analysis was conducted. Additionally, effects of such a compositional modification on the microstructure of the bodies were examined by a scanning electron microscope (SEM). Consequently, it was concluded that fired roof tile and brick wastes could be evaluated in both glazed and unglazed stoneware bodies. Introduction Stoneware is the general name applied to many wares fired between 1150 and 1300 °C. It has a different and denser structure than those of ceramics produced at lower temperatures. Fired stoneware possesses a lower water absorption value. When matured at a high temperature, it gives a possibility for the use of feldspar as a main ingredient [1-2]. Colors of stoneware can be brown, red, white and most of the times beige. Firing usually takes place in oxidation atmosphere but also reduction can be rarely used. This naturally has an effect on the body colors [3]. Earth, which contains clay minerals, becomes plastic mud when mixed with water, has a capability to be easily shaped and can be hardened without cracking if fired at 900-1000 °C, is referred as one of the brick and tile raw materials [4]. Natural and aesthetic appearances of buildings obtained with brick and tile products, which make them preferable especially for construction sector, are of importance. Because clays being main raw material of that type of productions generally do not exist as pure materials in nature, their usability depends on their mineralogy and impurities they contain [5]."

Jan 1, 2008

By Doon Gibbs

In this talk, we review highlights of x-ray magnetic scattering studies performed during the last decade, concentrating at the beginning on experiments on the rare earth metal holmium.(1-4) Besides intrinsic interest in the x-ray scattering cross-section and its description, studies of this type are motivated by the possibility that new structural and magnetic properties of rare earth metals might be revealed, and that new techniques may thereby be developed. As a result, interest in x-ray magnetic scattering experiments. has grown rapidly during the last 10 years particularly, with the regular application of synchrotron radiation techniques- Magnetic scattering experiments have by now been performed at most of the x-ray synchrotrons around the world. In addition, insertion .device beamlines dedicated to x-ray magnetic scattering experiments are planned at each of the next-generation storage rings presently under construction in the United States (APS), Europe (ESRF), and Japan (SPRING-8). Generally, the results of x-ray magnetic scattering experiments may be analyzed within two regimes of the incident x-ray energy, namely, in the limit of high x-ray energies, when the incident x-ray energy lies above the excitation energy of any absorption edge, and at resonance, when the incident energy lies near an absorption edge. In the high energy limit, the amplitude for x-ray magnetic scattering has the simple form [L(Q)?A + S(Q)?B](5-7) Here, L(Q) and S(Q) refer to the Fourier 'transforms of the atomic orbital and spin magnetization densities, respectively, and the vectors A and B depend on the incident and scattered wavevectors and on the: incident and scattered polarization vectors. 7) Because the vectors A and B are not identical, the polarization dependence of the orbital contribution to the magnetic cross-section differs from that of the spin contribution. This leads to the possibility that the orbital and spin magnetization densities maybe distinguished, in x-ray scattering experiments. The same distinction is not directly possible by neutron diffraction techniques (in dipole approximation, where the polarization dependence of the orbital contribution is identical to that of the spin contribution), and is important to a fundamental understanding of the electronic structure of magnetic materials. A particular

Jan 1, 1992

By Bradford C. Wesstrom, Omar Araujo

"Impurities from an electrolytic refinery are typically extracted from the electrolyte utilizing conventional electrowinning cells. These cells are arranged in series with cascading solution flow and are commonly referred to as liberator cells. The Freeport McMoRan Copper & Gold El Paso Refinery has optimized the removal of arsenic in cascading liberator cells by utilizing two separate feed solutions. The primary feed solution is recycled liberator electrolyte and the secondary feed solution is ""neat"" tank house electrolyte. The secondary feed solution is added based on the voltage response across the individual cells utilizing independent variable frequency drive (VFD) pumps. When the voltage across a cell changes, a signal is sent to the VFD pump to maintain a cell voltage of 1.98 volts. By maintaining this voltage the copper content in each cell exits at 2-4 grams per liter. This safely optimizes the arsenic removal as copper arsenides on the liberator cathodes.IntroductionDuring the electrolytic refining of copper, impurities from the copper anode report both to the bottom of the electrolytic refining cell as slimes and to the electrolyte. The impurities which enter the electrolyte are arsenic, antimony, bismuth and nickel. The impurities that report to the electrolyte during the electrolysis process gradually increase. As these impurities increase, they are incorporated into the refined copper cathode. There are many processes that have been used to remove these impurities from refinery electrolytes. Some of them are listed as follows: solvent extraction, ion exchange, hydrogen sulfide reduction, bioreactor, adsorption onto a low - solubility metal-oxide hydrate, adsorption onto activated carbon and EMEW cells. The conventional process used by the copper refining industry for controlling the level of impurities in electrolyte involves multistage electrolytic cascading liberator cells. In these cascading liberator cells copper, arsenic, antimony and bismuth are removed as various mixed deposits from the electrolyte. Removal of these impurities is achieved through an increase in voltage resulting from the depletion of copper in the electrolyte through electrowinning. With this higher voltage, the Group Vb elements, arsenic, antimony and bismuth are deposited on the copper cathode and report as slimes to the bottom of the cells. Nickel is removed in a subsequent process."

Jan 1, 2012

By J. P. Downey, L. G. Twidwell

"The high density sludge process (HDS) is a commercially proven acid rock drainage wastewater treatment process that is based on acid neutralization and metal precipitation. Previous studies have established that metal removal efficiencies in precipitation-based wastewater treatment applications can be improved through metal ion adsorption on ferrihydrite and/or aluminummodified ferrihydrite. This study was conducted specifically to determine whether the metals removal efficiencies at an existing industrial facility could be improved by promoting ferrihydrite and/or aluminum-modified ferrihydrite precipitation during the pH adjustment stages of the HDS process. The metal tenors of the treated wastewater samples are compared with those obtained through baseline experiments, which were designed to simulate the conventional HDS operation. The subject metals were: aluminum, arsenic, cadmium, copper, iron, manganese, nickel, and zinc.IntroductionThe HDS process is commercially proven ARD wastewater treatment technology that involves raising the wastewater pH by adding hydrated lime, caustic soda, or another alkaline substance. In addition to neutralizing the acidity, many dissolved metals precipitate as pH is elevated. Waste volume is minimized by capturing and immobilizing the precipitated solids.However, ARD streams characteristically contain multiple dissolved metal species. The response of various metals to pH adjustment in the HDS process is neither uniform nor quantitative, so minor to trace concentrations typically remain in the treated wastewater following solid-liquid separation. The effectiveness and applicability of the process would be improved if a means were found to further reduce the metal concentrations.Previous research and industrial applications have proven that metal ion adsorption on ferrihydrite (FH) and/or aluminum-modified ferrihydrite (AMF) increase metal removal efficiencies. Ferrihydrite and AMF are considered ideal for cation and anion adsorption from an aqueous solution at the appropriate pH [1]. Ferrihydrate adsorption of dissolved heavy metals is widely practiced throughout the world [2, 3]. It is established that FH and AMF effectively adsorb As contained in aqueous solutions [4]. Arsenic removal by adsorption on FH is the U.S. Environmental Protection Agency’s (EPA) Best Demonstrated Available Technology [5]. Twidwell and Leonhard also demonstrated that heavy metals (Cd, Cu, Ni, and Zn) are effectively removed from solution by coprecipitation/adsorption using AMF and FH [6]."

Jan 1, 2008