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By Michael G. King

The primary non-ferrous metals industry is the principal supplier of the minor metals selenium, tellurium and bismuth. It is also a major supplier of antimony. These minor elements are recovered from by-products of base metals production. To ensure that these elements remain available, the cost of production must be compatible with four other factors - method of production, available supply, technological niches, and product stewardship. This paper first describes the relationship between the copper industry and the production of tellurium and selenium. The more complex relationship between the lead industry and bismuth production is then discussed, followed by comments on antimony availability. Product stewardship programs are essential to the growth or certain specialized markets for these metals. Smelters and refineries of non- ferrous metals will play a major role in the recycling of scraps and wastes from these markets. Examples on how such materials can be recycled are given in the paper.

Jan 1, 1995

By Hanlu Xie, Liang Yu, Ping Wang, Yuanchi Dong

"The leaching process is the first step when recycling BF slag as raw material for some other products. While studying the kinetics of the BF slag leaching process, a fractal phenomenon was found, which indicated some interesting mechanism in the process. The result suggested a new understanding of the leaching process in detail which useful for the industrial applicationIntroductionTypical composition (wt. %) of blast furnace slag varied in a pretty wide range: SiO2 30–40, Al2O3 10–20, CaO 30–40, MgO 5–10.The ground granulated slag is commonly used as base of roadway (mixed with natural inert for paving, soil stabilization, etc.) or one of the resources of Portland cements because of its good hydraulic activity [1]. To recycle the slag economically, the selective recovery of some components of the slag may be considered. As main components exist in the slag, silica [2, 3 and 4] and alumina [4] recovery was first considered.While recovering of silica from the slag, silica gels are recovered selectively from the leaching solution deriving from the treatment of the slag with waste sulfuric acid. After separation of the exhausted solid of leaching, the silica gel is precipitated from the solution at pH 3.2. Although the silica gels obtained by this procedure contain many impurities and need some more work afterward, it is the first and important step for the process.In the prior work [5], silica extraction using blast furnace slag had been investigated, focused on the pH value of selectively silica extraction. In the present work, kinetics of the leaching process was focused. It is important to design an economical process.ExperimentalThe composition of the slag and the calcined gels has been determined by a LINK860 (Oxford Instruments, Oak Ridge, TN) energy dispersive spectrometer (EDS) in conjunction with a CAMBRIDGE S250-M2 (Cambridge Instrument Ltd., Cambridge, U.K.) scanning electron microscope(SEM). The leaching of slag and the precipitation of silica gels have been conducted at atmospheric pressure in a stirred reactor placed at temperature controlled by a heated water bath."

Jan 1, 2008

By Jürgen Antrekowitsch

Typical zinc oxides recovered from wastes like steel mill dusts and neutral leaching residues are of a low quality because of impurities like fluorine, chlorine, lead and others. Therefore, they are not comparable to technical grade zinc oxides produced in “French” or “American Process”. Some new developments, most of them still in pilot scale, try to establish processes where higher qualities of the product should be achieved. Zinc oxides are not only supposed to be an input material for electrolytic zinc production. Far more, they should find their way into the zinc oxide market as a substitute for technical grade zinc oxides. Furthermore, a new field of application for these oxides has been investigated at the department of Nonferrous Metallurgy, University of Leoben. Because of a higher acceptance concerning different impurities in relation to zinc winning electrolyses, a use in electrolytic galvanizing shows an interesting option. Therefore, synthetic zinc oxides with different impurities were generated to study the effect of these impurities especially on the quality of the zinc layer. Typical steel sheets, as used for car bodies, were electrolytically galvanized and the resulting layer was analysed, as main impurities compounds of fluorine, chlorine, iron, lead and calcium were used for the investigations. Beside the layer quality, the current efficiency and the possible galvanizing speed were examined. The results give an indication, weather such an alternative application can be feasible from a technical and economical point of view or not. 597

Jan 1, 2008

By Osvaldo A. Bascur

Several new hydrometallurgical plants have been built in the past years. They have implemented new processes to treat new type of ores. New technologies have been used to improve metallurgical performance from the start. The cycle times between knowledge generation and innovation are often neglected in the traditional capital expenditures and building of these new process plants. The paper reviews several implementations in which they have started with new ways of using information management from the beginning. The implementation of a real time performance management infrastructure is reviewed to assist in the implementation of mine to product strategies, metallurgical mass balances, solvent extraction composition statistical process control, methods to minimize organic losses, reduce variable costs and to improve metal extraction. Several examples are provided to improve operations by simplifying the access and analysis of information from assets and metallurgical processes. Continuous improvement and innovations have been enabled to minimize start times and for faster troubleshooting and resolution of operational problems.

Jan 1, 2006

By F. Leclerc, V. Rebeyrolle, M. Revil-Baudard, A. Jardy, M. Založnik, H. Combeau

"Since the quality of Vacuum Arc Remelted ingots is linked to their chemical homogeneity and metallurgical structure, a modeling study of the solidification during VAR has been undertaken. It is based on the solution of the coupled transient heat, momentum and solute transport equations during the remelting of a cylindrical ingot. Solidification mechanisms implemented in the model include a full coupling between energy and solute transport in the mushy zone, and accounting for nucleation and finite diffusion of solutes at the microscopic scale, in both solid and liquid phases. This modeling can be applied to actual multi-component alloys. In this paper, the macrosegregation in Zircaloy 4 ingots is investigated. To validate the model, one single melt of a homogeneous electrode has been specifically performed. The comparison between the predicted macrosegregation and the experimental results shows the importance of accounting for solutal convection to forecast properly the macrosegregation in remelted ingots.IntroductionVacuum Arc Remelting of zirconium alloy ingots is a key step in the manufacturing process of fuel assembly components in nuclear reactors. The control of the chemical homogeneity is indeed fundamental to ensure the quality and the in-reactor performance of the final products. Despite the use of electromagnetic stirring to homogenize the liquid melt composition, chemical heterogeneities develop in the mushy zone during the solidification stage. One of the main challenges for zirconium producers, as well as titanium producers, is to master the VAR process in order to control the macrosegregation in remelted ingots. Macrosegregation results from the association of microsegregation and transport phenomena. The latter are primarily due to the flow in the liquid and mushy parts. It is now well established [1-4] that the hydrodynamics of the melt pool in a VAR ingot depends on the combined action of the followings: thermal and solutal buoyancy, self-induced electromagnetic force and the periodic centrifugal force caused by the angular movement generated by the stirring. However, for zirconium alloy ingots, the effects of thermal and solutal buoyancy forces on macrosegregation through their influence on the flow in the mushy zone have not been clearly identified."

Jan 1, 2012

By Liping Li

A comprehensive three-dimensional two-phase mathematical model was developed to represent a channel type reactor with intense bottom gas agitation. Tracer dispersion and particle tracing methods were used to conduct the analysis based on the solution of the Navier-Stokes equations. Different operational parameters, such is gas volume flow rate. bubbler separation aspect ratios and liquid Input flow rates, were investigated for the purpose of reactor optimization. The numerical calculations were compared with experimental results obtained at the University of Missouri and a good general agreement was observed. Relatively low longitudinal mixing was observed characterizing the system as a "plug-flow" type reactor, in contrast to the intense vertical mixing, under the conditions investigated. Some general mixing characteristics are also discussed In connection to the behavior of other metallurgical reactors.

Jan 1, 1996

By F. Mucciardi

With the increasing trend to continuous smelting and converting, granulation of copper matte is gaining prominence as a means of decoupling the smelting and converting operations. Moreover, granulation is also being seen as a possible avenue to using higher grade oxygen in converters. By feeding cold solid matte, the oxygen concentration can be increased to compensate for the lower enthalpy feed. This leads to a higher grade of SO2 in the off gas and a lower total flow rate. Current granulation technology relies on the cooling of a falling matte film by water jets. This technology while effective has several drawbacks including those related to safety. Noranda and McGill University have developed a new process (patent pending) for solidifying copper matte (or slag). It overcomes many of the negatives of current technology. The system is based on an air cooled twin roll caster. This: new system uses no water and instead incorporates heat pipe technology to transfer the heat from the solidifying matte to the cooling air to produce a thin strip of 1 to 2 mm in thickness. Testing of a prototype unit demonstrated its viability. This paper describes this newly developed, twin roll casting system that is completely waterless. The advantages of this process as well as the findings from several tests are also detailed.

Jan 1, 1999

By Donato Firrao, Giorgio Scavino, Paolo Matteis

"The fatigue behavior of two high-strength sheet steels used to produce car bodies, a dual-phase steel and a TWIP one, both with ultimate tensile strength close to 1 GPa, is investigated.Unnotched tensile specimens are fatigue tested at room temperature with constant load amplitude and zero load ratio, in order to determine their 1 million cycles fatigue limit, both in the asfabricated sheet condition and after the resistance spot welding of one small homologous sheet square onto the calibrated length of the tensile specimen. Moreover, pre-cracked compact tension specimens are tested with load ratio 0.1 to determine the Paris fatigue crack growth curve.The fatigue results are completed with crystallographic, microstructural, tensile, and fractographic examinations, and the influence of the microstructure and of the welding processes is discussed.IntroductionCar bodies are increasingly made with high-strength weldable steels, in order to reduce vehicles' weight (to save fuel and reduce air pollution) and to improve the vehicle occupant safety in case of car crash. The main mechanical requirements of these steels in service are fracture strength and energy absorption, relevant for crashes, as well as fatigue endurance, relevant for ordinary car usage. [1]Steel sheets for car-body applications are usually made by continuous casting, hot rolling, cold rolling, continuous annealing (or other continuous heat treatment), and protective coating (in some cases). The sheets are then cold formed (deep drawn) to produce car body parts. Finally, the car bodies are built by assembling several deep-drawn parts, often consisting of different steels, usually through the Resistance Spot Welding (RSW) process, whereby two or three overlapping sheets are welded by local Joule-effect heating [2].Dual-Phase (DP) steels are widely used, low alloy steels with a microstructure consisting of ferrite and martensite, obtained from a final heat treatment which consists of heating at an intercritical temperature and then quenching. [3,4]"

Jan 1, 2012

By Honorio Oliveros Gómez, Oscar Jaime B. Restrepo

"Colombia produces nine tons of electronic waste per year and there are approximately 60 tons accumulation generated in the last nine years. This work aims to establish a general methodology in the laboratory to recover gold, silver and platinum group present in electronic waste, also explore other forms of recovery of metals contained in electronic waste. We selected seven types of electronic cards present in the computers, which have their parent desoldering electronic components. Initially, we characterized the components of the cards through X-ray diffraction and SEM, to identify the metal species and composition. Tests were conducted laboratory hydrometallurgical recovery of metals. This paper proposes a methodology for laboratory-scale work.INTRODUCTIONColombia produces nine tonnes of electronic waste per year and build there in about 60 tons generated in the last 9 years [1], Computers, TVs, audio equipment, monitors, cell phones, remote controls, printers and operated toys battery, among others are part of this inventory, which mostly comes to landfills, because the lack of legislation to control the final destination of waste electrical and electronic equipment, and lack of efficient technologies to recover materials [2]. Under these circumstances which have environmental implications, technological and economic recovery is essential metals present in the electronic cards of computers, by hydrometallurgical with subsequent base metal electrodeposition [3]. Pyrometallurgical route is discarded by major implications for economic and environmental [4]. Recovery From this perspective, the determination of the metal fraction and the relationship between the different metals, using the SEM characterization techniques - BSE and XRD is indispensable [5] It follows with electrolytic dissociation processes in the leaching and electrodeposition [6], and unit operations in the laboratory to carry out successfully these processes on a larger scale. Were randomly selected computer twenty-four postcards for nine types of cards have different functions in the computer, which, through the absorption desoldering technique, they broke the resistance (thermal, surface, photoresist, power), capacitors (ceramic, electrolytic), diodes (silicon, germanium, high frequency), transistor (NPN, PNP), processors, integrated (high, medium and low frequency), the RAM card and pin parallel port serial"

Jan 1, 2011

By Yongxiang Yang, Yanping Xiao, Robert G. Harskamp

"Stricter environmental regulations demand for safer treatment and disposal of incineratior fly ashes. So far no sound technology and processes are available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the MSW (Municipal Solid Waste) incinerator residues. The objective of the current research is to better understand the behaviour of the environmental harmful elements during low or high temperature treatment, and to find an optimum route for an efficient processing of the incineration fly ash. In the present study, the fly ashes including boiler ash and ESP (Electrostatic Precipitator) ash sampled from a MSW incinerator were washed with warm water, and the residues were dried and sintered or vitrified at high temperatures. The solutions from ash washing were analysed, and will be treated for salt extraction and purification. The ash residues before and after thermal treatment were also analysed. The results of vitrification and thermal behaviour were compared with those from the ashes without pre-washing. It was found that water pre-washing is an efficient way to remove certain water-dissolvable volatile salts such as chlorides, and thus the secondary emissions during vitrification could be reduced. INTRODUCTION The air pollution control residues from MSW incineration are classified as harzardous waste, including boiler ash, ESP ash and filter cake. The boiler ash is the firstly settled flue dust in the dust-collecting equipment under the boiler, the ESP ash is collected by an electrostatic precipitator in the second step, finally the flue-gas is further cleaned by the wet-scrubbers and residues are accumulated in the filter cake. Both the boiler ash and ESP ash are classified as hazardous materials, harmful to the environment due to the high concentrations of environmental hazardous elements. However, due to the different locations of the ash collection, the boiler ash has different compositions compared to the ESP ash, and is considered less toxic. Fly ash is generally toxic and with low bulk density, and has to be treated before final disposal. The current industrial practice is normally the landfilling after partial detoxification such as cement solidification."

Jan 1, 2008

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 Felipe P. D. Lopes, Jr. dos Santos, Sergio N. Monteiro, Frederico M. Margem

"Natural fibers are gaining attention as a class of low cost, biodegradable and renewable materials that also exhibit some interesting properties for specific applications. In particular, the incorporation of some natural fibers in polymeric matrix composites is nowadays providing opportunity of manufacturing a variety of industrial items, for instance automobile interior components. Among these fibers, ramie (Boehmeria nivea) is one of the least investigated and only recently was studied as polymeric composite reinforcement. Therefore, the objective of this work was to evaluate the possibility of ramie waste reinforced polyester composites to replace conventional building materials, such as plywood, plastic boards and gypsum panels in terms of a cost-benefit analysis.IntroductionThere is a growing concern over the environmental questions that are presently affecting our society in a global sale such as climate changes and generalized pollution. Among the solutions for these questions, the replacement of energy intensive materials, especially those long term degradable such as the synthetic fibers, is already being considered [1]. As a consequence, the past decades have witnessed an increase in research devoted to new biodegradable materials obtained from natural resources mainly the biomass. Important examples are the renewable natural fibers as well as composites incorporated with them [2,3]. In addition to their friendly status with respect to the environment, well know natural fibers like jute, sisal, wood, coir, hemp and flax are relatively low cost and recyclable. In recent works [4,5], the use of these cultivated and abundant lignocellulosic fibers was investigated as the reinforcement phase in polymeric composites.Other less know lignocellulosic fibers have also been recently investigated [6,7]. These are fibers that likewise show a potential of incorporation into the polymeric matrix of composite materials. Most of these less know fibers are typical of tropical regions and, in principle, their application in industrialized composites would represent job opportunities for developing countries in Africa, South Asia and Latin America."

Jan 1, 2008

By Yinlun Huang, Cristina Piluso

"Industrial sustainability looks to improve material and energy efficiencies, product quality and variety, and productivity within an industrial zone, thus pursuing the long-term sustainable development of the region. This paper introduces a systems-based modeling methodology, which provides industrial leaders with the ability to evaluate future production options to determine the path with the highest positive impact on both their own sustainability and the sustainability of the overall industrial zone. A comprehensive study on sustainable development of an auto-manufacturing focused industrial zone under uncertainty is illustrated. Introduction Sustainable development refers to a continuous process of improvements that must be followed in order to achieve a state of sustainability. In its most general form, a widely accepted definition of sustainable development was identified in the Brundtland Report as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [1]. Sustainability will occur when the material and social conditions can be maintained or improved for human health and the environment over time without exceeding the ecological capabilities that support them [2]. An industrial zone is defined as a geographic area comprised of a network of industrial sectors, each composed of a number of entities. Such a zone is highly integrated and complex, and contains numerous uncertainties due to each industry’s extreme dependencies on its suppliers and customers throughout the product supply chain. In the context of an industrial zone, sustainable development refers to the continuous process of advancements in the zone, and the entities that comprise it, creating more value, wealth, and profits (economically viable dimension), providing environmentally benign products with less raw material consumption and waste generation (environmentally compatible dimension), and collaboration and a direct relationship among all involved in the supply chain, i.e. the corporations, employees, suppliers, investors, communities, customers, etc. (socially responsible dimension). These are the triple bottom lines of industrial sustainability. In order for economic, environmental, and social sustainability improvements to be successfully implemented within an industrial zone, the industrial decision makers must possess system-wide analysis abilities. The analysis of the sustainable development of an industrial zone involves decisions at the local, regional, or national levels, which are complex and involves handling of ill-defined parameters with a high degree of uncertainty due to the imperfect understanding of the underlying issues [3]. This work focuses strictly on the uncertainties in future zone planning and a method and a scenario based approach that can be used to evaluate the sustainable development of an industrial zone among these uncertainties."

Jan 1, 2008

By Bob Drew, Alfred Spanring, Kirschen. Marcus

"Increasing material conversion and energy efficiency, and decreasing carbon dioxide emission levels are crucial for sustainable production processes in the aluminum, cooper, and steel industries. RHI supports these targets by providing a diverse range of solutions including high quality refractory linings, optimum lining maintenance, and process improvements. In this paper examples are provided of process improvements and increased energy efficiency in copper refining, potential energy savings during electric arc furnace and ladle operations in the steel industry, and increased energy efficiency by improved heat transfer in anode baking furnaces in the aluminum industry. In all cases, RHI’s expertise in close collaboration with the customer resulted in an improved performance of the reactor lining and the actual high temperature process with a positive impact on the material conversion and energy efficiency and as a result a decrease in specific carbon dioxide emission levels.IntroductionRefractory linings play an important role in heat transfer during high temperature processes in for example the aluminum, copper, and steel production industries. Due to constantly increasing energy prices worldwide and the increasing demands for environmental and climate protection, improving the energy efficiency and decreasing emission levels of these energy intensive production processes is of significant importance. In this paper, the contribution of modern RHI lining technologies to energy saving measures and the corresponding reduction of specific carbon dioxide emission are described. The type of current refractory solutions for energy intense processes are illustrated with four examples: Optimization and increase of material conversion and energy efficiency in copper refining, energy saving potentials in both electric arc furnace and transport ladle operations in the steel industry, and heat transfer improvements during the carbon anode annealing process in the aluminum industry. These examples focus on particular production processes operating with a high proportion of recycled copper, steel, and carbon anodes. Increased energy efficiency directly decreases the specific energy related carbon emission levels whereas improvements to the metallurgical processes aim to increase material conversion efficiency and, therefore, decrease specific process related carbon emission levels. Significant energy savings can be achieved by maximizing the refractory campaign length through a combination of appropriate refractory material selection, grade zoning, correct installation, careful preheating, and effective maintenance strategies. Besides the efforts to improve the performance and energy efficiency of customer high temperature processes, RHI continuously promotes the development of new low emission carbon-containing refractory bricks and unshaped products."

Jan 1, 2008

By Erich Hovestädt, Hans-Jürgen Odenthal, Christian Wuppermann, Herbert Pfeifer, Antje Rückert

"During the argon oxygen decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall nozzles and a top-lance. Due to the large amount of the injected processing gas, low frequency oscillations of the vessel can be observed. It is suspected that these oscillations can influence the converter's structure. The exchange of forces between fluid and the surrounding vessel is the focus of this study. An oscillation model was developed and tested, one objective being to limit the computational effort which is necessary for fully coupled and time resolved CFD and FEM simulations. Experimental results obtained from water-model studies as well as from on-sight measurements are available and were used in order to validate the numerical results. The authors' intention is a contribution towards a more in depth understanding of the factors influencing vessel vibration during the AOD process.IntroductionDuring the last four decades the AOD process has been established as a reliable and efficient refining process in stainless steel making. The injection of process gases (O2, N2, Ar) through sidewall nozzles shows advantages in mixing effectiveness compared to other injection geometries e.g. bottom blowing [1]. Stainless steel grades contain usually more than 10% chromium. With decreasing carbon content during the decarburization periods the tendency of chromium oxidation increases according to the varying chemical equilibrium which depends on the partial pressure of carbon-monoxide (CO) in the gas phase. That's why oxygen is gradually replaced by inert gases, usually argon or nitrogen, in order to lower the CO partial pressure and thus to minimize chromium oxidation. Despite the high injection velocity of approximately Ma = 1, the kinetic energy of the gas jets is consumed within a short distance from the nozzle exits due to the large density ratio between gas and melt of approximately 1:8000. With increasing distance to the nozzle exit, the initial horizontal velocity of the gas jet decreases and due to buoyancy force motion of the detached bubbles turns into a vertical direction. Subsequently a gas plume develops with its typical conical shape described by various authors [1-4]. Due to the drag force between gas bubbles and melt also the liquid phase is forced into a vertical motion. Near the free surface and the wall regions the melt flow is deflected in different directions. Subsequently, the typical flow pattern in the AOD vessel arises, as sketched in Figure 1 and described in literature [5-9]."

Jan 1, 2012

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 A. Dell’Era, M. Pasquali, C. Lupi

"An electrochemical cell has been designed to treat very diluted cobalt solutions, i.e. those deriving from recycling processes of lithium-ion batteries. A reticulated vitreous carbon sponge was used as cathode and a Pt-coated Ti net as anode. A controlled potential electrolysis has been carried out in a solution flowing in the cell and maintained at a constant pH of 6.5. Considering the cathode dimensions (10.0 cm * 10.0 cm * 1.25 cm), rather high volumes of solution (>1 litre) can be treated with flow rates up to 1.6 l/min. The process yield is obviously related to the solution concentration; it has been observed that, starting with a solution containing 200 ppm of Co2+, the yield is initially ~35-40%, but it decreases to ~20% when 80% of the initial cobalt content has been electrowon. The yield increases up to ~50% if the carbon electrode is coated by cobalt. The conditions allowing a fast and complete removal of cobalt are outlined. Introduction Industrial liquid effluents containing heavy metal ions arise not only during hydrometallurgical processing, but also in many sector of chemical industries utilizing metal catalysts and process reagents. These waste solutions containing low quantities of metallic ions can be treated by chemical precipitation, solvent extraction, ion exchange, etc. before final discharge. All these techniques could be efficient for complying the aqueous effluents with the severe rules related to the environmental impact, but they can not directly produce metals. Particularly the chemical precipitation presents two main drawbacks, huge amount of sludge prodction and reagent costs to produce this useless and sometime dangerous sludge that have to be considered. Electrochemical technologies can be used for the treatment of effluents polluted by metal ions, showing the following advantages in comparison with other processes: 1. recovering of the polluting substances in metallic forms, with subsequent reusing; 2. absence of process slag, which should be subsequently disposed of. In this work an electrochemical reactor with a reticulated vitreous carbon cathode and a platinated titanium net anode has been designed and utilized for removal Co from waste aqueous solutions. Porous materials have been used as electrodes for this cell, as their high specific surface area favours the treatment of these low metal content solutions (1-7). This kind of electrodic material presents very interesting chemical-physical characteristics such as: low density, low thermal expansion and high electrical and thermal conductivities; particularly the reticulated vitreous carbon (RVC) presents a very elevated void volume, rigid structure, good resistance to temperatures in non-oxidizing environments and very low resistance to fluid flow."

Jan 1, 2008

By Shadia J. Ikhmayies

"Nanocrystalline fluorine-doped tin oxide, SnO2:F, thin films were prepared by the spray pyrolysis (SP) technique on glass substrates. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dispersive spectroscopy EDAX and transmittance measurements. X-ray diffraction patterns revealed the nanocrystalline nature of the films where the grain size was estimated based on the Sherrer formula. SEM micrographs showed that the films are uniform and totally covered with the material and they confirmed the nanocrystalline nature of the films. The absorbance was deduced from the transmittance measurements, and its first derivative was used to estimate the optical bandgap energy. Bandgaps larger than the bandgap of the bulk SnO2iF were obtained, indicating the presence of quantum dots. The hyperbolic band model was used to estimate the radii of the nanocrystallites. A comparison between the results of the different methods was performed.IntroductionTin oxide, SnO2, thin films are n-type semiconducting, transparent materials, which have numerous important applications in optical-electronic device technology. The optical transparency of SnO2, together with its chemical and mechanical stability, makes SnO2 films suitable for many other applications, such as transparent conductive coatings, gas sensors and heteroj unction solar cells [1]. In particular, SnO2 thin films have drawn much interest because of their potential application and integration with microsensor devices. Considerable attention has recently been focused on the development of solid state gas sensors based on thin films with a crystallite size smaller than the Debye length of the material, which show increased gas sensitivity and short response times [2]. In many of these applications, a doped SnO2 film is used as an active layer. Among the various dopants, fluorine is often preferred, because fluorine doping results in films with high transparency and good conductivity [1]."

Jan 1, 2012

By Hidekazu Nakagawa

We investigated the anodic dissolution behavior of titanium in TMHA-Tf2N molten salt, which has a wide electrochemical window of about 5 V, in order to develop an electrodeposition method for titanium. By etching a titanium electrode in HF?HNO3?H3PO4 solution, the titanium electrode became electrochemically active, and a redox reaction was observed at around -0.15 V vs. I-/I3- in (TMHA-Tf2N)?HTf2N solution. We identified the redox reaction consists of the reduction of the proton and the oxidation of hydrogen. The diffusion coefficient of the proton in TMHA-Tf2N was calculated to be 6.9 10-8 cm2 s-1 at 50 °C from the cathodic peak current in the cyclic voltammogram. Anodic decomposition of the molten salt was not observed up to 6.0 V vs. I-/I3- on titanium electrode, while it was observed at around 2.0 V vs. I-/I3- on platinum and glassy carbon electrodes. Cathodic decomposition of the molten salt was observed at around -3.0 V on the titanium electrode, as well as on the platinum and glassy carbon electrode.

Jan 1, 2006

By Mrutyunjay Panigrahi, Takashi Nakamura, Atsushi Iizuka, Etsuro Shibata

"The production of FeTi intermetallic alloys from mixed oxide precursors using direct electrolytic reduction was studied. Fe203 and Ti02 powders were mixed in appropriate molar ratios, pressed into small pellets, and then heat treated at temperatures in the range 1000-1300°C. The pellet heat treated at 1000°C was electrolyzed in molten CaCh at 950°C, using a graphite crucible as the anode and the oxide pellet as the cathode, at a potential of 3.0 V. The products of the electrolytic reduction of (Fe,Ti) oxide were examined by XRD, SEM and EPMA. It was found mat the (Fe,Ti) oxide was reduced progressively from the outside to the inside of the pellet until the metallic state was achieved.IntroductionFast and energy-efficient technologies for materials production are essential for the sustainable development of society, and such development is supported by advanced technologies. Since the introduction of titanium and titanium alloys in the early 1950s, these materials have, in a relatively short time, become major materials for the steel, aerospace, energy, and chemical industries. Its combination of a high strength-to-weight ratio and excellent mechanical properties and corrosion resistance make titanium the best material for many critical applications [1]. Titanium alloys are now used in demanding applications such as static and rotating gas-turbine engine components. Some of the most critical and highly stressed civilian and military airframe parts are made of titanium alloys. The use of titanium has expanded in recent years to include applications in nuclear power plants, oil-refinery heat-exchangers, marine components and medical prostheses.Ferrotitanium is one of the most widespread and effective ferroalloys. It is also a well-known hydrogen-storage material and will be extensively used in the future because hydrogen is emerging as an eco-friendly energy source [2], Ferrotitanium is an alloy consisting of iron and titanium, with a minimum titanium weight content of 20% and a maximum titanium weight content of 75%, and is manufactured by reduction or melting."

Jan 1, 2012