Search Documents

By Z. Zak Fang, P. Fan, S. Middlemas

"Titanium dioxide (T1O2) has been widely used as pigment in paints, paper and cosmetic products, as well as high-tech applications such as PV Cells, semiconductors, biomedical devices and air purification. T1O2 pigment is primarily produced by the high temperature chloride process, resulting in considerable CO2 emissions. A novel hydrometallurgical process for making T1O2 pigment without direct CO2 emission is investigated. The new method promises to eliminate direct CO2 emissions, consume significantly less energy, and produce minimal environmental waste. The novel process involves molten salt roasting of titania slag, with subsequent washing, leaching, solution purification, hydrolysis, calcination and post-treatment stages, resulting in high-purity anatase or rutile pigments while realizing significantly reduced environmental impacts. Pigment whiteness is critically sensitive to trace amounts of discoloring impurities such as iron and chromium. Several methods for reducing the levels of these impurities are investigated. Energy consumption and emission models are also developed.IntroductionTitanium dioxide (T1O2) is one of the most commonly used minerals in the chemical manufacturing industry. It has been commercially processed since the early 1900's, and has a wide variety of applications. Pigment is used in paints [1], plastics and paper [2], sunscreen [3], cosmetics and even as a food additive [4]. T1O2 has also been used in photovoltaic cells [5], biomedical devices [6], and in air purification [7]. T1O2 pigment has a refractive index of 2.7, which imparts a high level of opacity (and hence whiteness) to whatever material it is added [8]."

Jan 1, 2012

By Leonid N. Shekhter, Corby G. Anderson, Esra Cankaya-Yalcin, Daniel G. Gribbin, Joseph D. Lessard, Larry F. McHugh

"A new process for smelting copper, Looping Sulfide Oxidation™ (LSO™) significantly and positively alters the smelting energy balance. This process uses copper oxide in conjunction with air for the desulfurization of copper and chalcopyrite concentrates. Copper oxide is regenerated in a flash type furnace and then ""looped"" back for the oxidation of the copper concentrate. Heat and material balances show that the Looping Sulfide Oxidation™ process requires significantly lower net energy than conventional technology. This process produces anode copper and higher S02 content off-gases for efficient formation of sulfuric acid. Additionally, the process yields slags with lower copper solubility as compared to the conventional technology.IntroductionBased on the positive results from LSO™ investigations [1], further lab investigations into co=on sulfides and metal oxides were performed. It was discovered that chalcopyrite (CuFeS2) is oxidized with copper (II) oxide. In this reaction over 98.5% of sulfur was removed as S02, while a significantly improved energy balance was observed. This paper intends to analyze both the conventional flash smelting process and the newly developed Looping Sulfide Oxidation™ process, comparing heat and material balance results. LSO™ yields improvements to the energy footprint for copper, opening the door to new copper processing opportunities."

Jan 1, 2013

By C. J. Beyke

The U.S. Bureau of Mines has developed a process for the selective recovery of Pb metal from a mixed Pb-Zn concentrate. The concentrate was leached in recycled H2SiF6 at atmospheric pressure and 95° C with a redox potential of 570 mV (Eh). Eighty-five pct of the Pb was selectively leached from the concentrate while 87 pct of the Zn remained in the residue. Pressure leaching of the concentrate was slightly less successful, with 78 pct of the Pb leaching from the concentrate and 80 pct of the Zn remaining in the residue. Pure Pb metal was successfully electrowon from a purified PbSiF6-H2SiF6 solution with 96 pct current efficiency and 0.69-kW.h/kg energy consumption.

Jan 1, 1991

By Jan Dabrovska

Solidification and cooling of a continuously cast slab and simultaneous heating of a mould is a very complicated problem of transient heat and mass transfer. Nowadays, the solving of such a problem is impossible without numerical models of the temperature field not only of the slab itself, while it is being processed through the whole concasting machine (Caster), but of the mould as well. Two original numerical models have been developed and used in the investigation of a continuously cast steel slab. The first (one of two) 3D model of the temperature field of a concasting is capable of simulating the temperature field of a caster. Experimental research and data acquisition have to be conducted simultaneously with the numerical computation-not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. After computation, it is possible to obtain the temperatures at each node of the network, and at each time of the process. The utilization of the numerical model of solidification and cooling of a concasting plays an indispensable role in practice. The potential change of technology-on the basis of computation-is constantly guided by the effort to optimize, i.e. to maximize the quality of the process. The user can therefore choose any appropriate longitudinal or cross-section of a slab and display or print the temperature field in a 3D or 2D graph whenever necessary. The second numerical model of dendritic segregation of elements assesses critical points of slabs from the viewpoint of their increased susceptibility to crack and fissure. In order to apply this model, it is necessary to analyze the heterogeneity of samples of the constituent elements (Mu, Si and others) and impurities (P, S and others) in characteristic places of the solidifying slab. The numerical model, based on measurement results obtained by an electron micro-probe, generates distribution curves showing the dendritic segregation of the analyzed element, together with the distribution coefficients of the elements between the liquid and solid states. The combination of both models enables the prediction of cracks and fissures in critical points of the continuously cast carbon-steel slab. Both models had been applied in the industrial investigation of a cast low-carbon-steel slab.

Jan 1, 2003

By Jose Castro

The growing demand of scrap to supply the electric arc furnace has driven to search for new alternatives of raw material. The DRI produced using self-reducing pellets has become competitive due to the potential use of a wide range of carbonaceous materials such as coal, charcoal, biomass etc. In this context, the rotary kiln process using improved technologies such as post-combustion and self-reducing burden is a promising source of high quality raw materials. This paper presents a mathematical model of the rotary kiln process designed for self-reducing pellets and post-combustion. The model is based on the transport equation of two-phase flow, energy and mass transfer. The solid material is composed of a typical self-reducing pellet. The model considers the solid phase (C, volatiles, Fe2O3, Fe3O4, FeO, Fe, H2O, SiO2, Al2O3, MgO, P2O5, K2O, Na2O, FeS, CaO and gangue) and the gas phase (N2, O2, CO, CO2, H2, H2O, SO, SO2 and SiO). For each of the above components a conservation equation is solved and the mass and energy transport is accounted. The set of differential equations are coupled by the rate equations describing the kinetics of the several reactions, which take place within the rotary kiln. All the conservation equations are solved based on the finite volume method applied for a three-dimensional cylindrical coordinate system. Simulation results are presented for global parameters such as metallization degree, productivity, gas utilization ratio and calorific value. Inner conditions such as three-dimensional gas and solid temperature patter and compositions are discussed.

Jan 1, 2006

By Sergei A. Degterov

A thermodynamic database for the slag, matte and liquid copper phases in the Cu-Ca-Fe-Pb-Zn-Si-O-S system has been developed for the ranges of compositions of importance to the production of copper. When used with the Gibbs energy minimization software and other databases of the F*A*C*T thermodynamic computing system, this database will permit the calculation of matte-slag-copper-gas phase equilibria that take place during copper smelting and converting. The calculations reproduce within experimental error limits all available experimental data on phase diagrams, activities of components, enthalpies of mixing, matte - alloy miscibility gap and tie-lines. The calculated solubilities of Cu in both S-free slag and slag equilibrated with matte are also in good agreement with experiment under all studied conditions, such as at SiO2 saturation, in equilibrium with Fe, Cu or Cu-Au alloys, at fixed oxygen or SO2 partial pressures and at different contents of Pb, Zn and CaO in the slag. Sulfide contents (sulfide capacities) of the slags are predicted within experimental error limits. The distribution of Pb and Zn among matte, slag, copper and gas has been calculated. The calculations are in good agreement with experimental data and predict the distributions under conditions which are difficult to study experimentally, such as at magnetite saturation or under various oxygen partial pressures and iron to silica ratios in the slag.

Jan 1, 1999

By Henk Dijkman

Existing metallurgical operations can be optimized by implementing engineered bioreactor systems in the process configuration. For instance, metals can be recovered safely and economically from process and waste streams using biogenic sulfide. This paper focuses upon possible applications of high rate biotechnology in metallurgy and mining. Metal recovery from liquid streams (process bleed streams, leach water, waste streams), integrated removal of (fugitive) SO2, treatment of acid blowdown and other options will be described. Practical examples are given. A large-scale application of biotechnology at Pasminco's Budel Zink refinery is described. Here, acid plant blowdown is treated together with electrolyte magnesium bleed. Concentrated zinc sulfide (10 tpd) is produced biologically, eliminating the production of gypsum and closing the refinery sulfur cycle. Recovery of metals from solution at Kovehute Pribram in the Czech Republic is the second practical example. In this case, H2S is produced on-site for metal removal from an alkaline slag dump leachate. At the Caribou mine in New Brunswick, Canada, acid mine drainage is treated with biogenic sulfide. This plant is situated upstream of a lime neutralization plant. As a result, reusable ZnS is produced, the volume of the sludge (gypsum and hydroxides) from the lime plant is reduced by 50%, the sludge is free of heavy metals and the final effluent concentration of heavy metals is in the ppb range. In the second phase of this project, metals will be recovered from stored tailings, resulting in significant revenues.

Jan 1, 2002

By Ivanildo Hespanhol

"DALYs are a measure of the health of a population or burden of disease due to a specific disease or risk factor. It evaluates the time lost because of disability or death from diseases compared with a long life free of disability in the absence of disease. DALYs are calculated as the sum of years of life lost by premature mortality (YLL) and years of healthy life lost in states of less than fully health, i.e., years lived with a disability (YDL), which are standardized by means of severity weights, thus: DALY=YLL+YLD.WHO has established for wastewater use in irrigation (1) the same reference level of health protection as established for drinking water quality (2), i.e., the additional burden of disease from consuming water irrigated food should not exceed 10-6 DALY(Disability-Adjusted Life Years) loss per person per year (pppy). This level of risk means that a single additional case of disease may occur in a population of 1 million, during a life time (70 years). In a individual basis is equivalent to the occurrence of a mild disease during about 31,5 seconds.Such a restrictive risk is almost impossible to be attained in most developing countries which may not be able to afford the cost of wastewater treatment and of other protective measures, even for restrict irrigation.This paper presents proposals to adapt the reference level of risk to local technical, cultural, economical and social conditions of developing countries on the basis of a risk benefit approach."

Jan 1, 2008

By H. Y. Sohn, S. PalDey

"A new chemical synthesis process for the preparation of intermetallic compounds has been developed. It involves the vapor-phase reduction of mixtures of constituent metal chlorides by magnesium vapor to produce intermetallic compounds in the form of fine powder. The advantages of the process include (a) the use of inexpensive raw materials, (b) low reaction temperatures, and (c) products in the form of fine particles. Titanium and nickel aluminides were prepared by this method. The effect of AlCl/TiCl3 partial pressure ratio on the formation of different titanium aluminides was studied. A two-phase mixture containing 80 mol % of TiAl and 20 mol % of TiA13 formed at an AlC13/TiC13 ratio of 10. The amount of TiA13 was maximized to 72 mol% at an AlC13/TiC13 ratio of 16. The maximum conversion of the limiting chloride TiCl3 was 94 % . In the case of nickel aluminides, NiAI, NiAl3, and Ni2Al3 were formed by reducing mixtures of NiC12 and A1Cl3 vapors. The effect of the partial pressure ratios AlCl3/NiC12 and Mg/NiC12 on the formation of nickel aluminides was studied. The maximum content of NiAl obtained was 98 mol % . At the AlC13/NiC12 ratio of 19, a two-phase mixture of 17 mol% of NiAl and 83 mol% of NiA13 was produced. The product particles were very fine in the size range of 0.05 to 0.2 µm.A. IntroductionIntermetallic compounds are attracting much attention [1]. Titanium and nickel aluminides have attracted a great deal of attention from the aerospace as well as automobile industries because of their potential for high-temperature application (e.g., low density, good oxidation resistance, and high-temperature strength retention [2, 3]). Gamma TiAl and two-phase (TiAl and Ti3Al) alloys [4] are used for gas turbine engine rotational components as well as automobile exhaust valves. TiAl3 is one of the most extensively investigated aluminum-rich intermetallics. Nickel aluminides are attractive because of their low densities, relatively high melting point and good high-temperature strength properties. For example, Ni3Al shows increasing rather than decreasing yield strength with increasing temperature [5]."

Jan 1, 1998

By G. J. Abbaschian, A. B. Gokhale, M. M. Kunjapur

"A laboratory scale model furnace was constructed for obtaining radially inward oriented columnar grains in disc shaped castings. The furnace consisted of eleven circular, concentric, equispaced resistance heaters on each half of a split graphite mold. Water or air flowing through a copper pipe along the periphery of the disc constituted the heat sink. After filling the mold, the heaters were turned off consecutively in top and bottom pairs from the rim towards the center, causing the temperature gradients to move inward. Equiaxed structure was obtained at the center by turning off the inner coils together when desired. Sn:15%Pb alloy was used to cast integral blade disc castings using the above technique to obtain dual-property discs with a central equiaxed structure and an outer columnar grain structure projecting inwards from the blades to the rim. A numerical technique was used to predict the temperature profile in the disc during solidification, and good correlation was obtained with the experimentally measured temperature profiles. The corresponding heat transfer coefficient values obtained were h = 544 Wm- 2k-1 (0.013 cal/cm2- ° C-sec) for cooling between metal and chill and h' = 71 Wm- 2k-1 (0.0017 cal/cm2- ° C-sec) for the heat input from the hot mold to the liquid metal. BackgroundHigh temperature alloys used in the current generation of gas turbine engines have evolved through two main stages of development: in 1950's, the increase in the efficiency of gas turbines was paced by improvements in alloy design, which led to the development of Ni and Co-based superalloys (1). By mid-1960's, it was realized that improved alloy chemistry alone was inadequate in meeting the increasingly stringent service requirements. The focus of research then shifted from alloy development to process development, and resulted in the introduction of directional solidification (DS) techniques for the production of turbine blades and vanes (1,2).Under typical operating conditions, the blades and vanes are subjected to aerodynamic loading, while the blades are additionally subjected to high centrifugal loading and vibratory stresses. The primary material requirements for blades may be summarized as follows (1,3):•,High creep resistance•,Good high temperature tensile strength (typically in the range of•,275 to 550 MPa at temperatures in excess of 750°C)•,Resistance to both low cycle and high cycle fatigue (LCF and HCF)•,Resistance to erosion, corrosion, and oxidation•,Resistance to thermal fatigue"

Jan 1, 1986

By Chenhui Liu, Hong-ying Xia, Bingguo Liu, Wei Li, Jinhui Peng, Libo Zhang

"Dielectric property is an important limiting factor in the development of microwave processing of minerals and ores. In this study, we used an open-ended coaxial sensor method to measure the complex permittivity of an ilmenite concentrate (41%TiC>2) and microwave absorption properties from room temperature to 100°C. The results show that the dielectric constant, loss factor and loss tangent increase with temperature rising at 2.45GHz. Microwave absorption properties of this ore are highly dependent on temperature and frequency. Ilmenite concentrate can be used as raw materials to prepare wideband microwave absorbing material. The research will be helpful in explaining the thermal running of microwave dielectric heating the ilmenite concentrate.IntroductionAs the sources of high-grade titanic mineral are decreasing worldwide, the utilization of low-grade minerals such as ilmenite has attracted more attention [1,2]. Because Panzhihua ilmenite has complex minerals and high contents of MgO, CaO, S1O2 , it is difficult to upgrade the ilmenite to titanium-rich slag and farther produce synthetic rutile and titanium dioxide pigment [3]. Therefore, it is desirable to develop new technology for processing ilmenite ore [4]."

Jan 1, 2012

By T. V. Jayaraman, Kranti Kumar, Paul Praveen J., Dibakar Das, A. R. James

"Lead free piezoelectric ceramics with high piezoelectric coefficients are in great demand for sensor and actuator applications. Synthesis and characterization study of one such lead free system, barium zirconate titanate - barium calcium titanate [xBZT-(1-x)BCT] (x = 0.5), via solgel method have been carried out. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of single phase BZT-BCT nanoparticles (<50 nm). The as-synthesized powders were calcined at 1000°C and the powders were pressed into cylindrical pellets. Solid-state sintering of the green pellets at 1550°C for 2 hrs resulted in single phase perovskite structure. Hysteresis loops were obtained which indicates the ferroelectric nature ofBZT-BCT. The bulk ceramic samples with the highest sintered density (~93%) were subjected to electrical poling and the piezoelectric properties ( d33, kp, & i:,) were measured. The structure and piezoelectric properties were investigated and correlated for the given composition of the BZT-BCT system.IntroductionPiezoelectric ceramics are widely used in various sensors and actuators and most of the piezoelectric ceramics, which are presently used, are lead based, which contains at least 60% lead (Pb) by weight. The critical disadvantage of these lead based piezoelectric ceramics is their hazardous effect related to the toxicity of lead, which poses a serious environmental concern starting from their processing to the disposal stage[l]. It is well known that a material to be a good piezoelectric it requires a morphotropic phase boundary (MPB) i.e. the composition induced phase transition between any two ferroelectric phases."

Jan 1, 2013

By H. Kamarudin

The behaviour of cassiterite-sulphosuccinamate flotation system was examined in the light of zeta potentials measured by micro-electrophoresis method. It was observed that sulphosuccinamate substantially affects the zeta potentials of cassiterite, lowering its i.e.p. to pH 2.5 and indicating a specific adsorption and/or chemical interaction. The optimum concentration for flotation, as seen in micro-flotation tests, was found to be associated with the most effective lowering of the zeta potentials, the optimum pH being 3.0. The effect of cations in the pulp was examined for the presence of ferrous, ferric, aluminium and lead ions. The ions ferric and aluminium were observed to create an intense effect of increasing the potentials to positive side, possibly due to adsorption of cation hydroxy complexes, as indicated by their respective species distribution diagrams.

Jan 1, 1994

By A. M. Blount

In 1983, a final ruling of the U.S. Occupational Health and Safety Administration (OSHA) specified that chemicals containing >0.1 % of a carcinogenic substance or > 1 % of a substance hazardous to health must be labelled. Amphiboles of the fibrous or asbestos-type must be quantified at levels of 0. I % whereas the status of non-fibrous types is not finally determined at this time. Tremolite and actinolite can possibly be measured to 0.1 % by XRD, but anthophyllite cannot be so measured. Recently the International Agency for Cancer Research (IARC) has designated quartz as a suspected carcinogen, and its quantity must be measured to the 0.1 % level. Thus, it has become Increasingly important to be able to detect and quantify minerals in bulk samples down to low or "trace" levels. It has been found that minerals needing to be quantified can often be concentrated by microcentrifuge and counted by means of polarized-light microscopy. For example, amphiboles in talc samples can be separated by using a heavy liquid (thallium formate-malonate) of density 2.810. Talc floats, and amphiboles sink. After centrifuging, the denser particles are removed from the bottom with a Pasteur pipette and placed in a clean centrifuge tube. Distilled water is added to the tube containing the denser minerals and the tube centrifuged again. After several washings with distilled water, the sample is removed along with a drop of water to a clean glass slide. A drop of 1 .584 refractive index liquid and a cover glass are placed over the dried sample. The slide is scanned for particles greater than 5 um in length and having an aspect ratio greater than 1:3. These are checked for refractive index, sign of elongation and extinction angle to differentiate them from talc particles on edge and other minerals. Amphiboles have all indices greater than 1.584, and talc has all indices equal to or lower than this value. Alternately the heavies at the bottom of the centrifuge tube can be filtered through a nucleopore filter. After the filter has been washed with distilled water and dried, a 1.584 refractive index liquid renders the filter transparent in two of the four extinction positions so that a count of amphibole particles can be made directly on the filter. The refractive index-density method which is so useful for talc powders should be equally useful for other nonsoluble industrial minerals.

Jan 1, 1989

By Yue Gong, ChuanJie Cai, Jing Chen, Shaobo Zheng, Huigai Li

"MnS-AlN duplex precipitates were successfully extracted from electrical steel slabs by means of non-aqueous solution electrolysis. The three-dimensional duplex morphology became visible using emission scanning electron microscope (SEM) JSM-6700F and energy dispersive spectroscopy (EDS). The precipitation sequence of MnS and AlN in the hot process can be predicted via the three-dimensional duplex morphology. Thermodynamic calculations were carried out on account of the chemical compositions of the steel studied in this paper. The results verified that AlN nucleated on MnS, which precipitated earlier during cooling process of electrical steel. Based on the results, the material compositions and rolling temperature can be adjusted to modify their precipitation timing and morphology. This is conducive to the growth of MnS-AlN duplex precipitates and reducing the obstacles to grain growth. Finally the magnetic property of electrical steel would be improved.IntroductionElectrical steel is a kind of ferrosilicon soft magnetic alloys with extremely low carbon content. It is mainly used in the manufacture of motors, generators, transformers and varieties of teleco=unications equipment. Non-oriented electrical steel requires isotropic high magnetic induction and low iron loss [l, 2]. Precipitates in steel have a great influence on its performance [3]. On the one hand, the indirect effect of precipitates on magnetic properties is to restrict grain growth in high temperature annealing process. On the other hand, the direct effect is pinning of domain wall motion, which leads to increased hysteresis loss."

Jan 1, 2013

By Lauri Holappa

Copper converting is mostly performed in Peirce-Smith converters. The process is still very similar to the original one developed in the early 20th century. It is a batch process in a horizontal cylindrical reactor with air blowing via tuyeres along the length of the reactor side. The Peirce-Smith converter has its roots in Bessemer&apos;s inventions in the 1850&apos;s as he tested both horizontal and vertical vessels for steel converting. However, for steel making a vertical pear-shaped converter with air bottom-blowing was established. In the course of time, there was a distinct necessity for oxygen usage instead of air due to harmful effects of nitrogen to steel properties and its cooling effect. In-bath blowing of oxygen did not succeed, however, and top-blown oxygen converter with oxygen lance (LD or BOF) was first developed in he 1950&apos;s and emerged rapidly to a dominating position. Somewhat later oxygen bottom-blowing via special shrouded tuyeres was developed (OBM or Q-BOP) but has attained only fractional share. Bottom-blowing technique had, however, impact on the current combined blown converters which adopted the benefits of both top and bottom blowing. In copper converting Peirce-Smith type converters have kept their position until today although new processes have been introduced and at least few of them seem to be emerging. In one respect copper converting has a clear leading position i.e. in the progress of continuous converting processes (Mitsubishi, Ausmelt). These processes utilise top-blowing lances instead of in-bath blowing tuyeres. A different principle for continuous converting is flash converting by Kennecott Outokumpu, which makes smelting and converting independent of each others. Solid ground matte is used as a feed for flash converting in a reactor shaft similar to Outokumpu matte flash smelting. A comparable process has been presented by Inco too. The paper discusses principal physico-chemical and process technical similarities and differences in copper and steel converting. Although these processes are metallurgically quite different it seems that during the modem history of ferrous and non-ferrous metallurgy, starting from the 1850&apos;s, the exchange of knowledge between these disciplines has been quite intensive. In long-term perspective, many similarities in the development can be found but also divergences due to different ambient circumstances.

Jan 1, 2003

By M. C. Ruiz

This work outlines the results of leaching studies on a copper concentrate containing chalcocite (Cu2S) and digenite (Cu9S5) with an acid saline solution of cupric chloride oxygenated at ambient pressure. The variables studied included the stirring speed, concentration of cupric ions, concentration of HCI, concentration of chloride ions, oxygen flow rate, temperature and time. The leaching system was found to be very effective for the dissolution of the concentrate. Over 95% of the copper was dissolved in 30 minutes with negligible dissolution of iron. The dissolution of copper increased with the stirring speed up to about 400 rpm and depended little on the total chloride concentration. The oxygen flow rate affected the dissolution of copper only below 0.1 1/min. The concentration of HC1 did not influence the dissolution providing its was sufficient to avoid the precipitation of copper oxychloride. The study of the effect of the temperature showed a maximum in copper dissolution around 90 "C

Jan 1, 1997

By L. Evrard, S. Brouwer, E. Bosly, E. Boydens

"A partial desulfurization roasting process has been tested on a typical copper-zinc sulfide concentrate in a Nichols Herreshoff monohearth pilot furnace whereby the su!fµr is partially removed and iron is to a certain degree preferentially oxidized. The phase changes that occur in the particles during selective roasting at 650°C and 800°C over a range of residence times were investigated by the use of chemical analysis, optical microscopy, X-ray diffraction and electron microprobe analyses. The purpose of this work was to get an insight into the mineral assemblages formed by controlled oxidation roasting and to evaluate if this non traditional approach could be afterwards used to recover zinc, copper and iron by a physical separation method. IntroductionThere has been considerable interest over the years in improving extraction and processing procedures for recovering non ferrous metals especially from polymetallic ores containing copper, lead, zinc and iron sulfides with very fine intergrown phases. Complex sulfide ores, which represent considerable reserves and resources in copper, lead and zinc, as well as precious metals and sulfur, are difficult to treat by conventional physical processes, leading to impure concentrates at low metal recovery. Some methods that can be used to treat such ores were described by G. Barbery (1). Various metallurgical routes generally combining pyro- and hydrometallurgical methods have been explored to develop new processes to recover the metals from zinc-bearing sulfidic ores and concentrates (2, 3, 4). The feasibility of partitioning complex sulfide minerals to simpler phases in order to improve selective extraction of mineral constituents has also been investigated (5)."

Jan 1, 1999

By Naixiang Feng, Shaohu Tao, Zhihui Wang, Yuezhong Di

"A novel vacuum aluminothermic reduction lithium process was developed in present work which used lithium carbonate, alumina and calcium oxide as raw material. The process mainly contained three steps. The first step is that LiA102 clinker is prepared in ambient environment, then metal lithium is vacuum extracted from LiAl02 clinker with aluminum power as reducing agent, and the last step is that alumina is leached from the reduction residue with a mixture of sodium hydroxide and sodium carbonate. The results show that the lithium reduction ratio can be over 95% under the conditions of reduction temperature 1423K, reduction time 3h, and aluminum excess 20%. The main components of reduction residue are CaO· Al203 and 12Ca0·7Alz03. The alumina leaching rate of calcium aluminate in residue is over 80%. High-whiteness aluminum hydroxide can be obtained by carbonation precipitation of the reduction slag leaching solution.IntroductionWith a density about half of water, lithium is with the lowest density of all solids, mere 0.5 g/cm3 at 20 °C [l]. Lithium is widely used in aerospace, aviation, nuclear-generated power and electric battery industry. Nowadays, over 90 % of the world's primary lithium is produced by molten salt electrolysis [2-4]. But the development of molten salt electrolysis will be effected by some factors: cost, environment, and so on. Vacuum thermal reduction may be used extensively in future because of its low-energy consumption, high-purity and short-cycle."

Jan 1, 2013

By Jose M. Gomez-Vega, Osamu Takai, Atsushi Hozumi, Hiroyuki Sugimura

"Ongoing research is reported aimed at improving the properties of mesoporous silica-based coatings on various substrates for optoelectronic or medical applications. Tetraethylorthosilicate (TEOS) was selected as the silica precursor, and amphiphilic triblock copolymers poly( ethylene oxide)- poly(propylene oxide)poly( ethylene oxide) as the surfactant micellar template or structure-directing agents. Cetyltrimethylammonium chloride (CTAC) was also used as a control agent. The effect of the templating agent and type of substrate (glass, Si, and Ti) on the mesoporosity, particularly on the alignment of the mesochannels, has been investigated. Three · different treatments (thermocalcination, photocalcination, and solvent extraction) have been also studied to remove the organic templates.IntroductionThe fabrication of mesoporous silicate-based materials through the utilization of a sol-gel process, where cooperative organization of organic and inorganic species takes place, provides a versatile approach to nanoscaled structures with potential applications in fields such as catalysts, optoelectronics, biomaterials, etc. Compared to conventional low molecular weight surfactants, self assembly of amphiphilic·block copolymers can result in mesostructured materials with larger pore sizes (up to 30 nm).1 Most of the synthetic strategies use silicon alkoxides as the silica precursor, although non-silicate metal alkoxides, e.g; Ti, Zr, Al, and B, have been also used to obtain different mesoporous materials, or even mixed metallic oxide systems. 2 Recently, Yang et al. 3 • 4 were able to synthesii:e a great variety of mesoporous metal oxides ID nonaqueous media using inorganic precursors (metal chlorides) and block copolymers as structure-directing agents."

Jan 1, 2000