Search Documents

By Xinli Wang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Byoung-Gon Kim

"The microwave dielectric properties of silicon dioxide at frequencies of 915 and 2450 MHz were characterized in the temperature range of 24 to approximately 1000 °C using the cavity perturbation technique. It is shown that the relative dielectric constant of silicon dioxide at both frequencies remains almost unchanged below 500 °C, above which there is a slight increase of 2%. The relative dielectric loss factor of silicon dioxide exhibits a strong temperature dependence above 500 °C and increases by approximately 7 and 5 times at 915 and 2450 MHz, respectively. The substantial increase in the relative dielectric loss factor is mainly attributed to the enhanced dielectric polarization and accelerated electrical transport in silicon dioxide at elevated temperatures.IntroductionSilicon dioxide (Si02) is usually considered a microwave transparent material due to its poor absorption capability at room temperature [1]. This characteristic has led to various applications of silicon dioxide in microwave processing of materials and communication. For instance, Si02 has been used to produce sample holders for microwave heating and substrates for electronic devices [2,3]. These applications generally require the material to withstand high temperatures under microwave irradiation. This indicates that microwave absorption capabilities of silicon dioxide at elevated temperatures are also important for its utilization.The microwave absorption capability of Si02 can be determined based on dielectric characterization (permittivity measurement) of the material at commonly used microwave frequencies, 915 and 2450 MHz, in a broad temperature range. To date, however, no detailed work on the dielectric properties (permittivity) of silicon dioxide at high temperatures has been reported. The present work is aimed to study the dielectric properties of silicon dioxide from room temperature to approximately 1000 °C at 915 and 2450 MHz. The results show that the permittivity of silicon dioxide has a strong temperature dependence above 500 °C, suggesting a substantial increase in its microwave absorption capability."

Jan 1, 2013

By C. A. Nogueira, F. Pedrosa, F. Margarido, R. N. G. Guerra

"A hydrometallurgical process for recycling spent Zn-MnO2 batteries was developed, involving leaching with sulfuric acid, purification by precipitation and metals separation for further recovery. Leaching of zinc oxide was easily attained while for manganese oxide was rather difficult depending on temperature and acid concentration. At 90°C and with the liquid/solid ratio of 20 L/kg, more than 95% of zinc is recovered in 30 minutes with 0.5M H2SO4. To attain similar recovery for manganese, higher levels of acid concentration and time are needed (e.g 0.7 M and 2 hours). After leaching a purification step is necessary to remove iron co-dissolved through Fe(III) precipitation. Separation of zinc from manganese by solvent extraction with 1M DEHPA follows in the process route. The countercurrent multistage separation diagram developed allows the production of a zinc electrolyte with 120 g/L Zn and 0.005 g/L Mn, and a raffinate with 16 g/L Mn and 0.013 g/L Zn.IntroductionThe recycling of spent Zn-MnO2 batteries is carried out by dedicated recyclers using several process alternatives [1]. Most of the running processes use pyrometallurgical technologies [2] based on zinc distillation. Alternative treatments by hydrometallurgy have been reported [3-5] but its application is scarce.In order to contribute to the development of alternative solutions, a process for recycling batteries based on Zn-MnO2 systems has been studied. The process is based on the hydrometallurgical treatment of spent batteries in sulfuric acid media (Figure 1). The process starts with the physical processing by shredding using cutting grinders, where the batteries are opened and size reduced, allowing the liberation of the interior electrode particles or pastes. The fines can be then separated and the coarse material containing the steel scrap can be treated to remove the remaining aggregate electrode. The final scrap also contains some plastics and other non-metal materials and can be further valorized."

Jan 1, 2008

By Gjergj Dodbiba, Toyohisa Fujita, Takahiro Kikuchi, I-Chen Wu

"In order to separate molybdenum (Mo) from the high-level radioactive liquid waste (HLLW), Pb-Fe based adsorbents were synthesized. The adsorbents were precipitated by adding sodium hydroxide in mixture of 1 mol/L lead nitrate and 1 mol/L ferric nitrate aqueous solutions. Each precipitate was then filtered, dried and ground to obtain a fine powder, which has been used as an adsorbent. Two main parameters were considered when synthesizing the adsorbents, i.e. the pH value at precipitation of adsorbent precursor and the calcination temperature of Pb-Fe based adsorbent. Moreover, the structures of the synthesized adsorbents were investigated by means of an X-ray diffractometer.The experimental results indicated that the calcination temperature of the Pb-Fe based adsorbent has a great influence on adsorption capacity of the adsorbent for Mo. It was found that when the Pb-Fe based adsorbent was calcinated at 500 oC, the sorbed concentration of Mo was the highest.1. IntroductionThe high-level radioactive liquid waste (HLLW), arising from the reprocessing of nuclear fuel are generally immobilized in an alkali borosilicate glass matrix. Broadly speaking, alkali borosilicate glasses are the matrix of choice for the immobilization of the HLLW, since they permit vitrification of waste stream of variable composition, [1]. Within this frame, the incorporation of molybdenum (Mo) is of particular interest in the vitrification of HLLW. Molybdenum is know to have a low solubility in borosilicate glass compositions and its presence in excess results in the phase separation of a complex yellow molten salt during vitrification, [1]. The formation of so-called “yellow phase” material during the vitrification process is undesirable since it leads to the accelerated corrosion of the inconel crucible liners. Furthermore, the “yellow phase”, which is reported to contain also other fission products, is soluble in aqueous solution providing a potential route for the leaching of radionuclides from the vitrified waste, should it come into contact with water, [1]."

Jan 1, 2008

By Andrew Shabalin, Vladimir Skorohodov, Svetlana Babaeva, ?lga Makovskaya

"At processing of some kinds of wastes (electronic scrap, secondary materials, spent nuclear fuel) in nitric acid solutions, and also in technology of silver refining, the significant amounts of palladium and platinum passes into a solution. The ion-exchange concentration of palladium and platinum in nitric acid solutions (5-500/dm3) are investigated. More than 30 various classes of ionites are tested. The most chemically resistance resins at the given conditions are identified. It is shown, that the maximum sorptive capacity to studied metals at high acidity the complexing, synthetic and inorganic sorbents possess. To definition of platinum metals sorption optimum conditions the kinetics is studied, isotherms of a sorption at various parameters from nitrate solutions are obtained. The conditions of the platinum and a palladium desorption from the pregnant sorbents and its regeneration with the subsequent reuse of materials were defined. The raw materials containing precious metals have very diverse composition and physical properties. Commonly the materials are processed by hydrometallurgical way. If gold or PGMs there are in raw materials to its opening hydrochloric acid solutions are applied. As an oxidizer nitric acid, hydrogen peroxide, gaseous chlorine, etc are used. Nevertheless, at processing of argentiferous materials and preliminary treatment of a waste including the spent nuclear fuel, nitric acid solutions are often used and the specified metals in some extent pass into solution [1]. Therefore selective extraction of PGMs from nitrate solutions is an actual problem. In the present work the ion-exchange concentrations of palladium and platinum in nitric acid solutions (5-500 g/dm3) are investigated. At the testing more than 30 various classes of ionites the most chemically resistance resins at the given conditions are identified. These resins are synthesized on the base of polyacrylate, styrene-divinylbenzene and vinylpyridine. For a selection of the most effective resin among what are made in Russia and overseas, a number of ionites with various functional groups were studied. Influence of functional groups type on a PGM sorption is shown for extraction of a palladium as an example (table 1). The presented data shows, that palladium concentration in a phase of ionites depends on sorbent type. If the increasing of solution acidity essentially reduces palladium sorption by sulfonic cation-exchange resins (KU-2×8) than its sorption by strongly basic anionites is approximately equal. Intermediate position is occupied by complexing sorbents. The latter (AN-31, SN-3, ANKB-35, Lewatit TP 207, Purolite S 930) are the most effective for extraction of PGMs from nitrate solutions from the point of view of capacity value. According to [2], solution behavior of Pt (II) and Pd (II) are similar. As is known from coordination chemistry, ligand environment of the metal ions substantially impacts to character of electronic spectra. The figure 1 shows the results of measurements of optical density of platinum bearing solutions with various concentration of nitric acid at ?=400 nanometers"

Jan 1, 2008

By M. Ashraf, P. J. Hazell, A. A. H. Ameri, J. P. Escobedo-Diaz, N. N. Elewa

A novel methodology to estimate the dislocation density in cubic metals by using microhardness measurements has been established. The proposed methodology is based on the Indention Size Effect (ISE) phenomena and strengthening mechanisms of materials at the micro-level. The methodology was validated by using experimental data of lean duplex stainless steel 2101 alloy. The results are confirmed via X-ray diffraction measurements and they substantiate that the proposed approach can be used as a general method to estimate dislocation density in metals.

Mar 1, 2017

By Rajesh K. Mishra

In secondary precious metals refining, the feed to the plant itself is a waste generated in manufacturing processes. Constant changes in manufacturing processes produce ever changing feed materials to the secondary PGM (platinum Group Metals) refineries. After extracting the precious metals, secondary wastes are generated. The discharge of effluent is dictated by both the PGM losses in wastes and the regulatory mandates. This paper will discuss some. of the conventional as well as some newer approaches to face both the challenges.

Jan 1, 1995

By Linping Yu

A simplified ED process was developed for organic acids recovery from cyclohexanone waste in this paper. In this regard, the one-stage ED was investigated directly without pretreatment, such as ion-exchange or nanofiltration to removal of foulants. The current efficiency and the energy consumption in the ED process for the recovery of carboxylic acids from cyclohexanone waste is theoretically analyzed and experimentally tested. The concentration of recovered carboxylic acid is related to many parameters and still needs more work to be determined.

Jan 1, 2009

By Kurt Westerlund

Cooling of hot sticky gases with solids in a circulating fluidized bed called FLUXFLOW is described. Fluxflow is used for gas streams from metallurgical reactors, e.g., Isasmelt copper in Australia and TBRC for lead in Sweden. The features and potential of this technology in metallurgy and waste treatment ie described. The FluxfLow la a new, cost efficient high availability solution to treat hot sticky gases that has made new gas handling and heat recovery flow sheets available to the process industry.

Jan 1, 1994

By Natasa Mitevska

The distribution coefficients of Ag, As, Au, Bi, Co, Cu, Ni, Pb, Sb, Se, Te, and Zn between copper matte and slag from the reverb furnace No.2 at the Copper Smelter and Refinery, RTB BOR (Yugoslavia), are presented in this paper. The influence of the matte grade on the minor elements distribution coefficients between copper matte and slag is analyzed. The minor elements distribution in the slag phase along the slag melt depth and the furnace length is also determined.

Jan 1, 2002

By H. P. Wang, E. M. Perry

"Analytical solutions for investigating the solidification of casting problems with initial superheat and natural boundary conditions have been derived using an integral method. There are two moving interfaces in the solution field, one for the phase change line and the other for the superheat line. Two coupled nonlinear differential equations, representing two moving layers, were calculated by the Runge-Kutta numerical integration scheme. The solutions are in terms of six dimensionless parameters: phase change number, two Biot numbers for interfaces, diffusivity ratio, and dimensionless superheat temperature and time. Parametric studies on these parameters have been conducted to provide generic information about this phase change problem. This analytical information is extremely useful for validating numerical solutions. A simplified I-D finite element model was constructed for the purpose of comparison. The excellent agreement between the analytical and finite element solutions has proven that they are mutually validated.This validated finite element modeling tool was then used for modeling an investment casting process of a super-alloy with a simple geometry: a two-step plate. The nonlinear latent heat release, a common property of alloy materials, was approximated by several piecewise linear segments. The transient temperature response of this 2-D finite element solution, including a metal/mold gap resistance, shows excellent agreement with experimental data.This fundamental work provides a solid basis for further work on the development of a process modeling tool for the complex investment casting process.IntroductionAt present, the investment casting process is used in a variety of industries. In the aircraft engine industry, in particular, investment casting is used to produce parts ranging from turbine blades to engine frames. Because a large single casting can replace many component parts that require machining, fabrication, and assembly, this one-piece casting approach becomes a very cost-effective manufacturing process.The main constraint in using this process for mass production is the long design-to-production lead time. The standard rigging design is still an art, based on the experience of casting experts, rather than on scientific methods. Many trials are often required before making a sound final casting. In order to .reduce the number of expensive casting trials, the development of computer-aided tooling technology is needed.The fundamental physics describing this manufacturing process can be simply described. They reduce to a solid/liquid phase change problem, with two parts - first, the thermal balance of the initial superheat temperature of the molten metal and the preheat temperature of the ceramic shell through heat conduction, and second, the energy release from the mold surface to the ambient by radiation."

Jan 1, 1986

By Philip Thompson

"Carefully planned laboratory test programs provide valuable data regarding the amenability of low grade gold ores to heap leaching. The most common laboratory test is the column leach test. The overwhelming problem associated with this type of test is the limit on the test column height. Most laboratories use a three (3) meter (10 foot) high column as a standard test due to building ceiling limitations, sample size limitations, etc. This paper presents a case study in which an ore sample was tested in a 1.5 meter, a three meter, and a six meter high column to determine the effect of column height on the test results. Other important factors such as sample preparation protocol, preliminary bottle roll testing to determine appropriate crush size, column diameter requirements, and leach solution analyses, are also discussed.IntroductionColumn leach testing has been used for years by many laboratories to determine the amenability of low grade precious metals bearing ores to heap leaching. However, the test work can be compromised by poor planning, misinterpretation of results, and extrapolation of data beyond the reasonable boundaries of the experiment. Preliminary test work should be performed prior to column testing. This preliminary work provides valuable information regarding the response of the ore to cyanidation and aids in the design of the column tests.The sample should be screened into various size fractions prior to testing. The fractions are assayed to determine the gold content of each size fraction and of the overall sample. The most valuable preliminary test is the bottle roll cyanidation test which is usually performed on five kilograms of coarse sample in a large rolling bottle which can accept material up to 50 millimeters top size. The residue from this test is screened at different sizes to determine the distribution of unleached gold in the residue. Comparison of the gold distribution in the leach residue with the distribution of gold in the feed at the same size intervals provides an indication of the appropriate crush size for the sample. The overall gold extraction from the sample at the crush size tested is also determined from these data. Lime and cyanide requirements can also be estimated from this test. The viscosity of the bottle roll pulp and the size distribution of the feed and leach residue can also suggest whether agglomeration of the ore will be required prior to column testing. Ores which contain significant amounts of clays (greater than 5 percent) will generally require agglomeration to prevent plugging of the test column."

Jan 1, 1997

By Thomas F. Hagelien, Stein Tore Johansen, Svend Graadahl

"The dross appearing at the surface of an aluminium melt consists, in addition to aluminium, of mainly oxide films but also other non metallic inclusions. The inclusion particles are often poorly wetted by the metal and accumulate at the metal surface. However, in impeller stirred reactors for melt refining stirring may be exceedingly strong and inclusions accumulated at the metal surface may be entrained into the bulk metal. Concerning inclusion removal, such effects may deteriorate the effectiveness of melt refining.In this paper we investigate the surface entrainment of buoyant particles in a water model of an impeller stirred refining reactor. Under varying operating conditions the particle concentration in the bulk liquid is measured by laser light attenuation. The observed entrainment of particles is explained theoretically and metallurgical consequences of the findings are discussed.IntroductionIn the modern cast house continuos metal refining and casting is well established. One of the most distinct advances in metal refining has been the introduction of degassers which introduce bubbles into the metal. The bubbles act to remove dissolved elements together with nonmetallic inclusions. In the most efficient degassers stirring by different kind of rotors is applied to increase mass transfer and inclusion removal. However, it has been known from experience in the cast house that for violent stirring the concentration of some types of inclusions may increase from inlet to outlet of the reactor. This phenomenon has so far been attributed to production of dross in the reactor due to oxidation of metal. Due to removal of inclusions by bubbles the dross layer inside the reactor must be expected to increase in thickness by time. The removed inclusions and produced oxides due to strong stirring is removed at regular interval by the operators of the degasser. However, a fundamental understanding of the phenomena which take place in and below the dross layer is lacking. In the present work we add buoyant particles to the surface of a refining reactor and investigate how these particles may be entrained and dispersed into the liquid depending on the flow conditions. Similar investigations for gas stirred ladles have been performed by Taniguchi et al [1] who found that below a critical gas flow rate all particles are trapped at the surface. Above the critical gas flowrate the surface velocity are sufficiently high to entrain the particles. In this situation it looks like all particles are ready for the melt and a balance between terminal velocity and turbulent dispersion determine the concentration in the liquid."

Jan 1, 1999

By Kunihiko Takeda, Kimio Imaizumi, Tsuyoshi Arai

"The study on the preparation of mono-dispersed liquid droplet was performed using ultrasonic as one of the steps of producing the perfectly mono-dispersed particle. The ultrasonic system was a 33.6kHz ultrasonic generator, an amplifier, an electric distortion element, and a bolted Langevin type horn installed in .a cell. For the first time, a liquid pillar under a nozzle of the cell ·was stably formed. Then, dense and coarse parts were alternatively constructed by oscillating the wavelength of the ultrasonic.· The diameter of those liquid droplets were found to be· perfectly uniform, therefore, it was measured by ""multiplex photography"" using a synchronized stroboscope with the ultrasonic.- From the results, more than 30,000 of perfectly uniform liquid droplets in 1 second were observed by this method.IntroductionRecently, research on the control of physical form is done in various fields of industry. Some examples are the processing technology of the minute compound material of micro-machines and integrated circuits, and the form control of molecule size like catalysts. There is a need for such material to take on various forms in correspondence to its use. ""Form control"" as used in this study will indicate ""research on physical chemistry factors which determine the size of the material"" and will refer to the contour uniformity of comparatively little particles. A well-known method of preparing particles is to spout a mist of liquid and slurry from a nozzle l) 2). Particles for metals, catalysts and food have been prepared by this method. In this case, although an approximate particle diameter can be decided by controlling the nozzle diameter and the violent outflow velocity, it is not easy to completely control ·the contour and to prepare a particle with uniform diameter. ·However, the preparation of perfectly uniform particles is necessary for solders for the adhesion of electronic wiring 3), ion exchange resins4), catalysts and so on. Large quantities of fine particles and super-fine particles are generated when manufactured in the usual way. Large quantities of these fine· particles and super-fine particles have polluted the internal and external' environments of factories. The products yield' ·decreases, also. From such a background, this study examines the preparation of perfectly uniform particles that could be· collected -100% as products. Recently, NASA has succeeded in the preparation of perfectly uniform particles in zero gravity 5). But the preparation of 'perfectly uniform particles by this method is difficult, and it can not be used in general industry"

Jan 1, 2000

By G. Kugler, M. Tercelj

"The use of the up-to date light alloys and their development are in the sharp ascent especially in transportation industry. In the last years the use of the magnesium alloys for the various purposes was strongly increased. The aim of present research was to study the influence of solidification rate on hot workability and on obtained mechanical properties of AM60 magnesium alloy. The study was also focused on possibility to omit prior homogenisation process which would result in cost reduction. The solidification of gravity cast alloy has been investigated with various methods of the thermal analysis: in situ simple thermal analysis and simultaneous thermal analysis. In order to reveal optimal hot working conditions the deformation behaviour was studied in the temperature range 200-450°C and strain rates between 0.001-lOs-1. Mechanical properties have been studied with tensile and impact toughness testing.IntroductionIn recent years, the increased demand for magnesium alloys has been mainly driven by the need of automotive and transportation industry to reduce the weight, as this is the most important parameter to reduce the energy consumption. Beside their very low weight in comparison to other metals, the magnesium alloys are characterized by good machinability, corrosion resistance and good mechanical properties, and can thus compete with aluminium alloys and for some applications even with steels. Due their decreased workabilty they are typically used as cast alloys, but in recent years also the research of their wrought state has become more extensive [1-7]. Decreased hot workability of magnesium alloys originates from their hexagonal close-packed structure. One of the most popular magnesium alloys with great potential for many applications is AM60 (MgA16Mn), which is predominately used for casting. But its application could be increased if the mechanical properties, could be improved. This can be done by hot working. Namely it is well known that wrought microstructure is characterized by better mechanical properties in comparison to as-cast state. On the other hand due to its low hot workability the homogenization process is required prior hot deformation, which results in increased production costs. Thus the aim of the present research was to study the influence of solidification rate on hot workability of AM60 alloy in order to improve its mechanical properties and to check the possibility of producing near-net-shape casting products omitting homogenisation process by employing small additional deformations after casting. Within the framework of this research the solidification of gravity cast AM60 alloy has been investigated with various methods of the thermal analysis."

Jan 1, 2011

By M. Kobayashi, Y. Nishisu

"Fine multicomponent particles of yttrium and europium were synthesized through the precipitation from homogeneous solution, and the various characteristics related with the fluorescence were investigated. The morphology and the fluorescent characteristics of the synthesized particles were affected by ionic species in the stock solution. In the presence of sulfate ion, some parts of the precipitated particles were aggregated, and _the fluorescent characteristics were not good. On the other hand, in the presence of chloride ion or nitrate ion, the particles precipitated were almost monodispersed, and, the intensity of the fluorescent emission were strong after calcination. Further, these particles were also very attractive as the red phosphor in the mercury-free fluorescent systems.Introduction Eu doped Y oxide particles have been widely investigated for the application to the fluorescent lamps and displays: Recently, the fluorescent lamps are pointed as harmful electric equipments because of using mercury for excitation. Therefore, the use of the mercury in the fluorescent- system will be limited or prohibited worldwide in near future. Then, the development of the mercury-free fluorescent lamp is strongly required without delay. Inert gas such as neon and/or xenon seem to be applicable as new excitation element that replaces the mercury. However, in case xenon the excitation wavelength,' 146 and 172nm, is different from that of the mercury, 254nm, and then, the commercial phosphors which are used in the present fluorescent lamp system are not available. Therefore, the invention of the novel phosphors is essential for the development of the mercury-free fluorescent lamp. Further, the controls of the size and shape of the particles precipitated are also important, because the homogeneity of the size and the shape is very important for the fabrication of the layer of the phosphor particles. That is to say, the development of the phosphor particles with controlled components, size and shape is essential. The precise control of size and shape improves the packing density, and so, the screen performance of the lamp [1]. In addition, these phosphor particles should be also useful for the application of the flat-plane displays, for example, PDP, etc. [2,3]. In the present work, first, the particles including yttrium and europium for the precursor for red phosphor were prepared through precipitation from homogeneous solution. This process was precisely controlled for the control of the components, size and shape of the particles precipitated. Next, the particles precipitated were calcined, and then, their fluorescent properties were characterized. As a result, some of them showed the possibly available characteristics as the red phosphor for mercury-free fluorescent lamp system. These experimental results are presented in this paper."

Jan 1, 2000

By Yang Tian-zu

Sodium pyroantimonate which is widely used as the clarifier in the glass industry and as the synergist in anti-flaming industry respectively has a production history of about 30 years in China. At present there is the production capacity of about 20,000 tons per year in China and China is chief producer of sodium pyroantimonate. In this work the production processes adopted by the producers of China, the operation conditions and the product qualities of sodium pyroantimonate prepared by different preparation methods have been summarized, and on the basis of comparing the advantages and disadvantages for each process the most advanced method - the air-oxidation method was introduced in detail. The production processes of sodium pyroantimonate mainly include the method of oxidation by sodium nitrate, the oxidation method of hydrogen peroxide, the potash salt method, the chlorination method and the air-oxidation method etc. The method of oxidation by sodium nitrate in which the crude antimony oxide, sodium carbonate and sodium nitrate are separately used as the raw material, the flux agent and the oxidant, has the advantage of short and simple technological process, but low grade quality of sodium pyroantimonate and bringing about serious environmental pollution are the disadvantages and this method has been substituted by other methods. Sodium pyroantimonate can be directly prepared by the hydrogen peroxide oxidation method with the advantages of simple technological process, high grade quality of the product and little environmental pollution. High grade quality of sodium pyroantimonate can be also synthesized by the potash salt method, in which industrial antimony white, the hydrogen peroxide, potassium hydroxide and sodium hydroxide are applied as the starting material. The disadvantages of these two preparation methods are high production cost and high requirements on the raw materials. The chlorination method with the crude antimony oxide, hydrochloric acid and chlorine as the raw material has the advantages of low production cost and high grade quality of the product. However complex process, high requirement of anti-corrosion for the equipments and producing plenty of waste water limit its application. The air-oxidation method with stibnite/jamesonite concentrate, sodium sulfide, and sodium hydroxide as the raw material and atmosphere as the oxidant is a newly developed method and its advantages are low production cost and the complex raw material can be treated by this method and its disadvantage is that the quality of sodium pyroantimonate is lower than that prepared by the oxidation method of hydrogen peroxide and the potash salt method.

Jan 1, 2006

By Hong N. Vu, Jitka Jandova

"Gypsum and limestone methods were examined in this study to process zinnwaldite wastes originating from dressing Sn-W ores mined in the Czech Republic. These wastes containing 0.20-0.30% Li and 0.10-0.20% Rb were subjected to magnetic separation to obtain a zinnwaldite concentrate with 1.36% Li and 0.94% Rb. It was observed that processing of the zinnwaldite concentrate with gypsum resulted in almost 96% recovery of Li into aqueous liquors, whilst rubidium extraction was only 25%. At the same time, it is possible to extract almost 92% Li and Rb from the identical zinnwaldite concentrate if the concentrate is processed by limestone method. Lithium carbonate, a final product of both methods was recovered from the refined sulphate solution using K2CO3 as a precipitation agent and/or from unrefined hydroxide solution using gaseous CO2. In the continuation of this study, rubidium will be separated from carbonate solutions after Li2CO3 precipitation as RbAl(SO4)2, an intermediate for Rb2CO3 production. IntroductionLithium is used as an alloying constituent in lightweight alloys, as a heat transfer medium in nuclear reactors and as a component in primary and secondary batteries. With the development of a new generation of electric vehicles, the lithium demand will dramatically grow. Lithium chemicals find extensive application in many industrial branches such as metallurgical, glass, ceramic and pharmaceutical industries. Rubidium compounds are predominantly used in psychiatry and medicine, in magneto-optic modulators, solid-state lasers, phosphors and components of electrolytes for fuel cells. The four most important lithium minerals are amblygonite, spodumene, petalite, and lepidolite. Spodumene LiAlSi2O6 (6.0-7.5% Li2O) and petalite LiAlSi4O10 (3.5-4.5% Li2O) belong to aluminosilcate minerals. Lepidolite (Li.Al)3(Al.Si)4O10(F.OH)2 (3.30-7.74% Li2O), lithium mica, is the most important representative of the mica minerals, a subgroup of the aluminosilicates. It frequently contains 3–5% Rb2O and eventually caesium. Zinnwaldite, which has the general formula K(Li.Al.Fe)3(Al.Si)4O10(F.OH)2 (2-5% Li2O), is regarded as a variety of lepidolite with a high iron content. Commercial amblygonite is a complex phosphate (Li.Na)Al(F.OH)PO4 (up to 9.88% Li2O), however, its deposits have not been commercially exploited because of their small size. Natural brines with a high lithium chloride content are important in the industrial production of lithium [l]"

Jan 1, 2008

By F. Raupp-Pereira, G. G. Cunto, J. A. Junkes, D. Hotza, V. P. Della

"The present work investigated the valorization of wastes as alternative raw materials for ceramic industries. Different industrial wastes based on the SiO2-Al2O3-CaO system and classified as non-hazardous were selected: sludge from varvite cutting process, sludge from gneiss breaks processes, sludge from filtration/clarification of potable water and a clay classified also as waste. All as-received residues were characterized by X-ray fluorescence, differential thermal analysis, thermogravimetry and particle size distribution. The applicability of these materials in ceramic formulations was then evaluated. The formulated mixtures were subjected to forming by pressing and extrusion followed by thermal treatment. After optimization of the processing conditions, the properties of the samples sintered at different temperatures were also evaluated. The waste materials studied proved to be alternative raw materials to natural mineral resources for the ceramic industry.IntroductionOne of the most important problems that have accompanied the humanity in recent decades is the environment’s degradation. In the same context, the natural resources exploration and technological development are phenomena which, if aren’t controlled, can cause ecological disequilibrium with unpredictable consequences [1]. It is in this perspective that recycling of various wastes assumes relevant importance.The recycling, understood here as the waste process reuse, is a common practice in the First World countries, where the raw materials have strategic aspects and the disposal techniques of solid wastes have considerable economic costs. In Brazil, the ecological conscience begins to be aroused due to, in the last ten years, the implementation of stricter laws for environmental control, in general, and licensing of waste generating from industrial activities, in special. The terms “residue” or “waste” are normally used to describe what remains of a production process; when an application for this material is not found. When wastes or residues are susceptible to be incorporated as raw materials or energy sources in a new material production, they can be understood as by-products [2].The valorization of industrial wastes is important, due to the need to pollute less and give an ecologically correct destination for wastes. The waste recycling, independent of its kind, presents several advantages in relation to using primary natural resources, such as reduction in the volume of raw materials extraction, lower energy consumption, lower levels of pollutant emissions and improvement of the health and safety of the population. The most visible advantage of recycling is the preservation of natural resources, extending its life and reducing the destruction of landscape and ecosystems [3]."

Jan 1, 2008

By Bret Boster

Facilities at Amax Gold's Sleeper Mine process some 330 kt of high grade ore and 4100 kt of low grade ore annually to produce 6.8 t of gold and 7.8 t of silver. High grade ore is processed in a conventional milling facility employing gravity concentration, CIC and CIP unit operations for gold and silver recovery. Low grade ore is processed using heap leaching and carbon adsorption methods.. Presented are the evolution and descriptions of the Sleeper processing facilities and discussions of selected' operating results.

Jan 1, 1989

By Aïda Espinola

This work is part of a research program concerning the study of heavy metal removal and selective recovery from electroplating waste waters in the Guanabara Bay ecosystem, preventing the potential noxious retarded effect of landfill, specially in a country of heavy rainfall. A flow-throw cell was employed to adapt to the limits established by the local legislation for disposal in rivers and seas. The cell design is presented and preliminary results show that this cell may be applicable for the decontamination from copper.

Jan 1, 1994