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By T. V. Swaminathan

Monazite sand is normally processed by, the caustic soda route to produce mixed rare earths chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earths chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earths chloride rather than the natural rare earths chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earths chloride, cerium p thorium and uranium from Rare earths + thorium hydroxide obtained by treating monazite based on stepwise hydrochloric acid extraction, was developed in our laboratory. The process involves drying of the mixed rare earths-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions.

Jan 1, 1989

By Mitsutaka Hino

The contents of gangue minerals, such as Al2O3. P2O5, crystalline water and so forth in the iron ore imported to Japan tend to increase year by year. Though the increments of such gangue contents arc approximately 0.1-0.2 mass%, some problems for the blast furnace operation in ironmaking process have already been reported, In order to clarify the mechanism of harmful effect caused by the small increment of gangue minerals, mainly Al2O3. on the blast furnace operation, the dripping behavior of Fe,O-CaO-SiO2-Al2O3-MgO slag from the iron funnel, which simulated the micro-porosity in sinter ore, has been observed with the wide range of basicity, Al2O3, Fe2O and MgO contents. The effect of MgO on the dripping behavior of slag has been summarized in this paper. It was found that the addition of 2mass% MgO resulted in large increase of hold-up on the most of the conditions. When Fe2O content was less than 20mass% and the basicity was lower than 0.8, MgO lowered the hold-up even if the slag contained 10mass% Ah03. Every slag hold-up showed the minimum at the basicity of less than unity on the conditions of constant Fe2O and Al2O3 contents, This trend became remarkable when the slag contained 2 mass% MgO.

Jan 1, 2003

By Leiting Shen

The thermodynamics of tungsten ore decomposition in mineral acid and alkaline solutions were studied. The published thermodynamic data of tungsten minerals were collected and assessed. The Gibbs energies of CaWO4 (−1538.43 kJ/mol), FeWO4 (−1053.91 kJ/mol), MnWO4 (−1206.08 kJ/mol), H2WO4 (−1003.92 kJ/ mol), and Na2WO4 (−1455.58 kJ/mol, aq) at 25 °C were adopted in the calculation using HSC software. The results show that CaWO4 is decomposed more readily in Na2CO3 solution than in NaOH,while FeWO4 andMnWO4 aremore reactive inNaOH solutions. Froma thermodynamic point of view, tungsten ore decomposes easily in acid solutions despite most ΔGo T increasing slightly with temperature. Oxidizing Fe2+ to Fe3+ in acidic solutions facilitates decomposition of FeWO4, and the reaction of CaWO4 in H2SO4 solution occurs more easily than in other mineral acids, due to the formation of sparsely soluble CaSO4. The results fit well with the experimental data and industrial experience previously reported in the literature.

By Taufiq Hidayat

Accurate description of complex phase equilibria provide the foundations for the improvement of non-ferrous pyrometallurgical smelting and recycling processes. Recent advances in microanalysis and experimental techniques enable accurate phase equilibria characterisation. Quantitative microanalytical techniques including Electron Probe X-ray Microanalysis and Laser Ablation ICP-MS enable the concentrations of major and minor elements present in different phases in samples to be accurately measured providing data that cannot be obtained using bulk chemical analysis techniques. High-temperature equilibration experiments coupled with the subsequent analysis of elementary reactions at micro- and macro-scales ensure the attainment of equilibrium conditions, and therefore, ensure true phase equilibria information is obtained. Examples of the application of the improved methodology on the investigation of phase equilibria of low-order and complex, multi-component gas/slag/matte/metal/solids Cu2O–PbO–ZnO–Al2O3–CaO–MgO– FeO–Fe2O3–SiO2–S systems and the distribution of minor element are provided. The experimental study is closely integrated with thermodynamic database development for the above system. Example of implementation of the research outcomes into industrial operations is demonstrated.

By W. L. Dalmijn

The processing of scrap and scrap cars starts with size reduction by a hammermill, or shredder. After the liberation the magnetic fraction is removed. The remaining non¬magnetic fraction mixed with other materials is screened and each fraction is processed separately. The increased use of plastic has a negative effect on the recovery of metals and waste production. At Huron Valley, Belleville Michigen, USA, the non-ferrous fraction from 5 million obsolete cars per year, containing 200,000 tons of non-ferrous metal, is processed. Aluminium Is recovered with a heavy medium separation process and concentrated with eddy current separators. The remaining heavy non-ferrous fraction is concentrated by a new combination of eddy current separation and image processing. After this separation process the zinc fraction is melted and refined and the copper, brass, stainless steel and other high-quality concentrates are sold to the secondary industries. The recycling of car scrap has become an important source of metals and materials for the secondary. materials processing industry.

Jan 1, 1995

By E. Gutierrez-Miravete

Hot pressing processes are widely used to shape metallic, ceramic, and glass components. The process is an essential step in manufacturing ceramic fibre-glass matrix composites. The paper describes the use of computer simulation by the particle method, to the analysis of the deformation and flow of glass during hot pressing. The hot glass is represented by an assembly of interacting particles which deform in response to the applied pressure. The results, which should be regarded as complementary to continuum-based studies, provide useful insight about the hot pressing process.

Jan 1, 1990

Physical and chemical methods were investigated to tower thorium levels in Eneabba Ilmenite from the natural levels of 180-500 ppm to give Becher Process synthetic rutile with less than 100 ppm thorium. Chemlcal treatments, but not physical separations were successful. A pilot plant trial of a sodium hydroxide leach (25M NaOH at 75°C and 40 wt% solids for Ih) followed by a sulphuric acid leach (3M H2S04 at 90°C and 60 wt% solids for 211) confirmed that thorium could be removed to below 100 ppm. However, the activity of the ilmenite was not lowered to the same extent

Jan 1, 1996

By Qinmeng Wang

The oxygen bottom blown copper smelting process is a new technology which has been widely applied to the copper production in China. In this work, a computational thermodynamics model for this technology has been established, based on smelting mechanism and theory of Gibbs free energy minimization. The calculated results from the model agree well with the actual industrial data, indicating that the model can be used for the predictions under different operating conditions. The tendencies of the key parameters (such as Cu losses and Fe3O4 content in slag) and the distribution ratios of the minor elements (such as Pb, Zn, As, Sb and Bi) can be predicted by adjusting the oxygen/ore ratio charged into the bottom blown copper smelting furnace. The model can be used to monitor and optimize the industrial operations of the oxygen bottom blown copper smelting process.

By S. S. Ibrahim

The left behind material after the combusion of fossel fuel in some power stations in Cairo; weighing tens of tons every years, was investigated. The material called "Fly Ashes" containing 7.5% Ni, 10.0% V and 9.50% Cr; could be considered as a promising source of such valiable elements. As well as the small grain size (050 70 "m) of the material, and besides the complexity of their formation history, hydrometallurgical methods appeared to be the effective technique to deal with. Yet, preconcentration is possible by means of magnetic and gravity separation methods. The end product is assaying 16.60% Ni and 20.2S!; V with weight recovery of about 60.15%.

Jan 1, 1995

By Sergey Shabala

Green leaf tissues convert solar energy into the energy of chemical bonds of sugar molecules during the process of photosynthesis. The efficiency of this conversion can be much higher than efficiency of any of the currently known silicon-based solar panels. Importantly, vast amounts of CO2 are assimilated during this process. The efficiency of photosynthesis is critically dependent on the availability of a large number of nutrients, among which metal cations such as K, Ca, Mg, Cu, Zn, Fe, Mn, and Ni play a key role. In this paper I summarize basic requirements and major functions for each of these essential nutrients in plant photosynthesis, both at the whole-plant and molecular level. I will talk about how these requirements may be affected by the global climate trends and discuss the prospects of creating artificial photosynthetic “bioreactors” for efficient energy conversion and CO2 assimilation.

Jan 1, 2009

By D. E. Roberts

Over 425 million used automotive oil filters are discarded in the United States each year. Estimates prior to this research claim that 10% are recycled with the remainder typically being landfillcd. Surveys conducted with ferrous scrap users and oil filter processors as part of this research reveal that at least 15% are currently being recycled as ferrous scrap. Oil filter scrap is not being used by many operations because of concerns with scrap consistency and quality. These concerns stem from trials conducted in the infancy of the oil filter recycling movement. Consistent scrap quality depends both on the content of the used oil filters and the processing technique used to produce the scrap. Technology has advanced since the first recycling trials were conducted by steelmakers. Several different types of scrap are available, including pucks, bricks, cubes, and shred. This research conducted at the University of Missouri-Rolla investigated the content of used oil filters and compares the recyclability of different oil filter sizes and designs. Filters vary by application and vary between manufacturers for a particular application. An understanding of the scrap itself as well as the concerns and problems of both oil filter recyclers and oil filter processors is necessary to increase the number of used oil filters being recycled.

Jan 1, 1996

By L. Becze, S. J. Hock, G. P. Demopoulos

"Regeneration of HCl from chloride solutions is commercially practiced by high temperature (800-900 °C) pyrohydrolysis associated with high energy consumption and capital cost. As an alternative to pyrohydrolysis a novel low temperature ( <200 °C) non-autoclave hydrolytic process has been studied in this research work, which comprises two steps. In the first step, ferrous chloride is oxidized by oxygen at 1;150 °C, followed by hydrolytic decomposition of ferric chloride to coarse hematite particles and superazeotropic hydrochloric acid (8-9M) operated at approximately 180 °C. This paper provides a summary of the laboratory results related to both oxidation and hydrolysis and presents a newly designed conceptual process flowsheet.IntroductionRecovery of base, noble and rare metals from ores and secondary materials (slags, dusts, residues) by chloride-based hydrometallurgical processes holds a lot of promise if a low cost HCl process becomes available. This is particularly so due to the high activity of HCl or more accurately activity of hydrogen ion [1] in concentrated chloride media and the formation of chlorocomplexes allowing for effective leaching under atmospheric leaching conditions and simultaneous ease of metal separation. However, during leaching significant amount of iron, which is associated with most of ores and secondary materials, goes into the solution. Hence, the obtained leach solution has to be treated to convert iron chlorides into easily filterable iron oxide and simultaneously produce concentrated hydrochloric acid. Apparently the critical operation of these processes is the regeneration of the lixiviant (HCl). Currently in the industry, its regeneration is accomplished by high capital and intensive pyrohydrolysis which operates at 700- 900 °C. Aimed at lowering the operational cost of pyrohydrolysis a process called PORI [2] was developed and tested in pilot plant scale in the 1970s for the purpose of treatment of pickle liquors without, however, resulting in industrial application."

Jan 1, 2011

By Atul Kurnar

In the present research a two-cell polymer electrolyte membrane fuel cell stack (PEMFCS) with SS-316 bipolar plates has been tested. Different flow field designs were studied and a modified multi-parallel channel design is proposed. The stack is stable within ±3 mV even after 1000 hours of continuous operation, indicating efficient water management and effective removal of any metal ions from the stack. Also no iron is detected in membrane electrode assembly (MEA) by EDAX analysis after 1000 hours of cell operation. Results indicate that high operating pressures beyond 138 kPa didn&apos;t significantly increase the performance of cell, however added much to the pressurization cost of the system. Tests at different temperatures showed that at temperatures below 80°C, external humidification could be completely removed. The prototype stack is also tested under variable load conditions simulating highway-driving schedule. The experimental efficiency of PEMFCS is 48%, which is in good agreement with the model predicted efficiency of 53.8 %. Results show that 59% of the total losses are due to ohmic polarization in the cell. Further analysis on applications of the stack in automotive transportation system is in progress.

Jan 1, 2002

By Robert L. Stephens

"It can be argued that one of the most important property of any material is cost, since this property detennines the applications for which a material can be considered. Despite growing demand and production for commodity metals such as copper, nickel, zinc, lead, and tin, the cost of these metals has been steadily decreasing in real terms. The only way that metal miners and producers can remain financially viable in the long term is by continuing to lower their cost curve through the implementation of new metals production technologies. This paper reviews technological developments in the production of copper, nickel, zinc, lead, and tin that have or threaten to redefine the cost curves for these metals.DisclaimerThe opinions expressed in this paper the author's, and are not necessarily those held by the author's employer, Cominco Ltd.IntroductionThis meeting will discuss many novel technologies and processes for producing metals and materials with specific properties that will enhance the applications ranges for the material or will allow entirely new applications to be developed. However, in every real-world case, the cost of the new material or process is an important property that determines which applications the material or process can be used in. Other properties that are important depend on the applications.A recent press report (1) discussing the potential replacement of aluminum radiators with copper radiators in pickup trucks and sport utility vehicles provides an interesting example to reinforce the importance of cost in materials selection. In this case, the displacement of aluminum by copper is being considered because of the more favorable heat dissipation characteristics of copper. Heat dissipation has become more important due to the development of hotter-burning V-8 and V-6 engines. For this application, engineers also consider cost, weight, size, durability, and manufacturing process. The report stated that the development by the International Copper Association (ICA) of the ""CuproBraze"" manufacturing process for heat transfer products was an important development. This technology produces 845 radiators that weigh less, are more uniform in quality, and are potentially more compact. They are also expected to cost less in high production quantities than copper units produced in the past, last three to four times longer than soldered copper radiators, and the process also eliminates the use of lead solder from the manufacturing process."

Jan 1, 2000

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process. The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By Jorge Alberto Soares Tenório, Flávia Paulucci Cianga Silvas, Denise Crocce Romano Espinosa, Ivo André Homrich Schneider, Erika Gusmão, Daniella Cardoso Buzzi, José Roberto de Oliveira

"This study evaluated the Salvinia sp action on metals biosorption in a synthetic sample of acid mine drainage (AMD) in order to determine the time and amount of metals uptake. Biosorptives tests were realized varying the contact time of 5, 20, 60 and 240 minutes. And keeping constant the follow parameters: pH (2.6), biomass concentration (1g.L-1), temperature (25°C) and agitation (175rpm). In order to quantify the metals concentration captured by biomass, the AMD samples will be analyzed by ICP. Biosorbent, Salvinia sp., will be characterized before and after the biosorptives tests through analysis of SEM and IR. The micrographs indicate the occurrence of micro-precipitation and changes in biomass physical structure. The infrared spectra indicate changes in functional groups present in the biomass before and after the biosorptives tests.IntroductionThe current emphasis on environmental sustainability leads the industry in general, to treat their waste. The human activities are increasing, highlighting the industrial and mining activities, and have promoted the contamination of soil, waterways and groundwater by metals (1). The waste must undergo treatment processes aimed at reducing pollution, and therefore, less aggression ecosystems.This means the importance of studies of economic and effective methods to eliminate these metals from wastewater generated. The bioindicators are good investments in this area. The aquatic weeds are plants that inhabit swamps up from truly aquatic environments. They have several morphological and physiological adaptations that enable them to colonize the various aquatic environments. They are used as bioindicators of water quality and have also been used in decontamination of aquatic environments, production of biomass for livestock feed, fertilizers, soil and fish tanks (2)."

Jan 1, 2012

By A. Kontopoulos

The extraction of nickel and cobalt from low-grade greek laterites by sulfuric acid leaching has been studied. Batch and continuous mini-plant atmospheric leaching as well as pressure leaching techniques were employed. Atmospheric leaching at temperatures as high as 95 OC generally resulted in low Ni extractions (up to 82%), high acid consumption (650-850 kg/t ore or 80-100 kg/kg Ni) and high Fe co-dissolution (30%). Pressure leaching at 260 OC increased Ni extraction to over 98%, with minimal Fe co-dissolution (2.5%); acid consumption was 300 kg/t ore (31 kg/kg Ni). Detailed experimental results and conceptual flow sheets for atmospheric and pressure leaching are presented.

Jan 1, 1991

By K. G. Wang, M. E. Glicksman, P. Crawford

"We formulate the mathematical solution to late-stage multi particle diffusion in finite systems. The transition from finite system behavior to that for an infinite system is established. Large-scale simulations are reported regarding the dynamics of phase coarsening. Even in the case of a small volume fraction (Vv = 10-4), the particle size distribution is broader than that for the well-known Lifshitz-Slyozov limit at zero volume fraction. We also report the first simulation studies of extremely low volume fraction, for which corresponding experiments, as well as other simulations, do not exist at present for comparison. However, in the case of moderate volume fractions (Vv = 0.1), the fiucutations in the volumetric growth rate of particles are extracted from our simulations. These simulations provide additional insight into the statistical nature of diffusion interactions, including multiparticle stochastics during microstructural evolution.IntroductionPredicting microstructure evolution in alloys remains one of the cornerstones of materials science. Phase coarsening is a common process in microstrucural evolution that leads to a decrease in the excess total interfacial energy of the system. The system typically consists of separate and identifiable units, or domains, such as second-phase particles distributed in a matrix. During phase coarsening, larger particles grow at the expense of small particles. Over time, this ""competition"" results in an increase in the average size of the particle population, and in a concomitant decrease in the number of particles.Particle size and microstructure of many cast alloys depend on similar coarsening processes. Indeed, properties of these materials, such as strength, toughness, ductility, and electrical conductivity, depend on the material's average particle size and particle size distribution (PSD). Understanding and controlling microstructures in two-phase systems are clearly of widespread technological importance."

Jan 1, 2001

By Jose Hector Figueroa P.

Mexicana de Cananea, S.A de C.V. is a major copper producer mining a large deposit of the disseminated porphyry type considered one of the largest copper resources of the world with 2.7 billion tons of 0.60% copper for the mill plus 4.1 billion tons of averaging 0.26% copper for leaching. Mining of low grade sulfide leach ore, has been an important part of the overall production of the open pit mine which started in 1944. Before this time all the mining in Cananea was by underground methods. The leaching process in Cananea began on the 1920&apos;s with in situ operations in the underground mine and small dumps up to the 1950&apos;s. Large scale leaching operations began in 1960 and the copper solutions produced were treated in precipitation plants until 1,980 when the first SX/EW Plant was put in operation in Cananea. Leaching action is essentially ferric-bacterial, with no fiesh acid added to the leaching solutions. Traditionally, 5540% copper extraction is recovered fiom ROM, 70- 120 meter high leach dumps in 80 months of leaching. Cananea has successfully improved copper recoveries by implementing several actions that include: 1. Stripping of old dumps. 2. Leaching of old dumps through slotted casing. 3. Crushing conveying leach ore to minus 8 inch and stacking it in 30 meter lifts. As result of these actions, copper recovery has been increased&apos; to about 70% of total copper with actions 1 and 2 and up to 85% in half the time by crushing-conveying the leach ore, based on the same solubility index of the run-of-mine ore. This paper describes the above actions that were implemented to enhance the leaching recoveries from. sulfide leach dumps and the economics of such actions.

Jan 1, 1999

By R. Tunold, Y. J. Zhang

"The cathodic kinetics of aluminum deposition from aluminum chloridealkali chloride melts was studied by use of electro-cnemical transient techniques at 700 °C. Aluminum deposited as an insoluble product on a glassy carbon electrode and as a partly soluble product on a tungsten electrode. The deposition was found to be a simple diffusion controlled process involving the exchange of three electrons. The diffusion coefficient of aluminum chloride was calculated - 4.sx10-s cm2 ·S-I in AlCl3 -NaCl-LiCl melts and 2.6x10-s cm2 ·S-' in AlCl3 -NaCl-KCl melts. For AlCl3 -NaCl-CsCl system the diffusion coefficient exhibited some uncertainty due to nucleation. The determined rate constant of aluminum deposition reaction was on the order of 10-' -10-2 cm'S:' Constant potential electrolysis was carried out. TiB2 was well wetted by aluminum. The species of melts penetrated into graphite and glassy carbon but not into tungsten. The diffusion coefficient of species in glassy carbon was evaluated.IntroductionAluminum chloride electrolysis is attractive for its power saving of 30%. Different process to circumvent the conventional chlorization to obtain aluminum chloride economically, such as directly chlorizating mixture of Al~03 and C in a cell with A-shaped laminated bipolar electrodes by rising chlorine (1), or by use of a composite anode (2), will promote the electrolysis technology to be realized industrially. With the appearance of the Alcoa process periodically there are studies on the kinetics of aluminum deposition. Some discrepancies seem to exist on the mechanism of aluminum deposition. Borne studies (3,4,5) showed that the deposition of aluminum was hindered by diffusion process in the melts. M.Gabco et a1. (6) claimed a preceding dissociation of a complex being the rate controlled step. This paper presents our results on the mechanism of aluminum deposition from the study by use of transient techniques and some results from constant potential electrolysis."

Jan 1, 1988