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By C. M. Wai

Metal species in solid and liquid materials can be extracted by supercritical carbon dioxide containing a suitable ligand. This in situ chelation-supercritical fluid extraction technique offers, several advantages over conventional solvent extraction including minimization of organic liquid waste generation and exposure of personnel to organic vapors. One unique feature of this technique is that metal species can be removed from solid materials directly using supercritical carbon dioxide as a solvent. Several ligand systems including dithiocarbamates, ß-diketones, organophosphorus reagents, and macrocyclic compounds have been tested for metal extraction in supercritical carbon dioxide. This novel extraction technique may have important applications for metal recovery and mineral processing.

Jan 1, 1996

By Min-Min Lin, Bing Xie, Hong-Yi Li, Yang Yang

After precipitation of ammonium vanadates from vanadium-containing leaching liquor, vanadium (V(V)) and chromium (Cr(VI)) exist in the waste water in form of vanadate ions and chromate ions. In order to efficiently extract and recover V(V) and Cr(VI) from waste water, an environment-friendly method based on anion exchange was investigated in batch tests using macroporous weak base resin Dex-V. The adsorption conditions optimizes in detail, including the effect of pH, initial metal concentration, resin volume, contact time and temperature. The ion-exchange adsorption process for both V(V) and Cr(VI) showed maximum capacity at pH 3.0 for an initial concentration of 100 mg L−1, and reached equilibrium after about 40 min of contact at 298 K. The maximum adsorption ratio under the optimum conditions for V(V) and Cr(VI) was 98.98 and 99.87%, respectively. Result shows that the established method is a promising alternative for simultaneous extraction of vanadium and chromium.

Mar 1, 2018

By Yuya Nakai, Kuniaki Murase, Kazuhiro Fukami, Atsushi Kitada, Ken Adachi

The resources of vanadium –titanium magnetite in China are very abundant, most of which are used to prepare titanium-rich materials. Titanium pigment, electric welding bar and titanium sponge are made from titanium-rich materials such as synthetic rutile and titanium slag etc. To fully utilize titanium resources, many production methods of titanium-rich materials were proposed. In this article, authors review on methods of preparing titanium-rich materials which are Electric Smelting Process, Reduction-rust Process, Selective Chlorination Process, Acid Leaching Process, and sum the advantages and disadvantages of them. Existing problems and possible tendency of production methods of titanium-rich materials are also discussed.

Mar 1, 2018

By Yuchun Wang

In principle, supported liquid membranes could be an exceedingly elegant separation process. However they tend to fail by displacement and emulsification of the organic solution in the pores, which allows mixing of the feed and strip solutions. We have stabilized supported liquid membranes comprising moctylamine in nylon and PVDF supports by covering the pores with semi-permeable polyamide films, using an in-situ polymerization technique. Scanning electron microscopy demonstrates that the polyamide films are sensitive to production conditions and the nature of the support. The transport properties of stabilized supported liquid membranes for Cr(VI) are compared with those of unstabilized membranes.

Jan 1, 1998

By A. V. Tarasov

The nonferrous metals industry has been a sector with one of the highest growth rates during the recent years. The prospects for the Russian metals industry during the period until 2010 are associated first of all with a growing domestic demand for its products. The technological level of the metallurgical operations in Russia is relatively low in comparison with industrially developed countries: the average energy requirement is higher by 20% to 30%; the amount of generated waste in the process of rolled products manufacture is twice as high; the average labor productivity is lower by 2.5 to 3.0 times; the overall negative environmental impact is twice as high. Improvement of the technological level of the nonferrous metals production under the conditions of market economy is possible by application of innovative technologies for the development of this sector. The main trends for development of the nonferrous metals sector are: - meeting of more stringent requirements to the quality of concentrates; - more complete recovery of associated elements as commercial-grade products; - development of continuous process lines based on autogenous, resource-saving and environmentally safe processes; - use of combined technologies, including pyrometallurgical, hydrometallurgical and upgrading processes; - expansion of the fields of application for nonferrous metals and their alloys.

Jan 1, 2006

By Z. Jing, C. Jun

High-purity Bi2O3 was prepared via extraction-preparation stripping method use BiCl3 leaching solution. Parameters such as oxalic acid concentration, phase ration, aging duration, feeding duration, were examined for their effect on the size and morphology of precipitate. The precipitate was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry and thermal gravity analysis (DSC-TGA) and infrared spectroscopy analysis (FT-IR). Bi2O3 was characterized by elements analysis, particle size analysis and scanning electron microscopy (SEM). Bi2O3 product of 680 nm was obtained using 15 g/L oxalic acid, 1/1 phase ration, 0 min aging duration, 0 min feeding duration and calcinating at 500 °C for 2 h.

Mar 1, 2018

By Donald Voit

"The reaction between zirconia/zircon, coke, and chlorine involves a slow reaction between the coke and the zirconia/zircon and a fast reaction with chlorine. Because of the fast chlorine reaction, the reaction rate for zirconia/zircon is nearly independent of chlorine concentration for most conditions. The reaction between zirconia/zircon and coke is particle size controlled and related to the degree of physical contact between the zirconia/zircon and the coke. Since particle-particle contact is critical, compaction of finely ground coke and zirconia/zircon produces the highest reaction rates. Uncompacted, coarse coke and zirconia/zircon has the slowest reaction behavior with static bed tests.SummaryZirconia reacts with chlorine in the presence of carbon to form zirconium tetrachloride, carbon monoxide, and carbon dioxide. A similar reaction occurs with zirconium silicate with the additional formation of silicon tetrachloride. The reaction rate depends primarily on temperature and the intimacy of contact between the zirconia and the coke. The reaction is multi-stepped with a slow reaction between coke and zirconia to form an intermediate that reacts rapidly with chlorine, causing the order of the reaction for chlorine to be near zero. Chlorination rates in the range of 1 µmole/hr/cm2 are seen for fluid bed reactors. Plug flow, and static bed reactors have reaction rates of the order of 1 mmole/hr/cm2, where the area is based on the zircon surface area in plug flow and fluid bed reactors and the boat cross sectional area in a static bed. Chlorination rates measured in zirconia/coke briquettes are higher with rates as high as 400 mmole/hr/cm2 reported. High chlorine diffusion resistance, not accounted for in the analysis of experimental results, has led to a lot of confusion in the literature interpretation of chlorination data.In general coke and zirconia/zircon particle size, coke and zirconia/zircon intimacy, coke to zirconia/zircon ratio, chlorine concentration, and temperature are important variables for chlorination. Decreasing the coke and zirconia/zircon particle size generally increase the reaction rate. The coke to zirconia/zircon ratio affects the reaction in a more complex way. Increasing the chlorine concentration generally increases the reaction rate, but the effect appears to be more related to the concentration dependency of diffusion than to its role in the kinetics. The reaction rate increases with temperature but the exact behavior is complicated by temperature effects on diffusion."

Jan 1, 2011

By Chengyi Ding, Xuewei Lv, Senwei Xuan, Chenguang Bai, Kai Tang, Gang Li, Yang Xu

Perovskite easily forms during sintering of vanadium titanium magnetite (VTM) and is unfavorable for the following blast furnace. Steelmaking can concomitantly produce a great quantity of oxidized scale composed mainly of FeO and Fe3O4. Calcium ferrite (CaOFe2O3, CF) can be formed by oxidized scale with lime in air atmosphere and then added to the VTM during sintering. X-ray diffraction (XRD) results indicated that perovskite is not generated at low temperature but only when the temperature increases to 1473 K in the CF–TiO2 system. Therefore, VTM sintering can be performed with a low-temperature process with doping of CF. Perovskite formation is mainly divided into two steps. First, CF melts and produces CaO. TiO2 and CaO then combine to produce perovskite. This paper also discussed the reaction mechanism of CaO–Fe2O3–TiO2 ternary system to compare the generation routes of perovskite.

Mar 1, 2018

By Jorge A. S. Tenorio, Chuanwei Zhuo, Joner O. Alves, Yiannis A. Levendis

"The ever increasing number of automobiles and the consequential increase in consumption of tires have generated a pressing environmental issue, concerning the disposal of unserviceable tires. The worldwide disposed of waste tires is approximately 1 billion units per year and this amount is expected to increase by 2% each year. This work presents a microstructural characterization of nanomaterials synthesized in a catalyst system from the effluent of burning waste tire chips in a horizontal two-stage laminar-flow furnace. Controlled combustion of waste tire chips took place at temperatures of 900 or 1000 °C, and stainless steel meshes were used to synthesize the nanomaterials at 1000°C. Produced materials were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalyst meshes were covered by materials with diameters of 20 to 200 nm and lengths of about 40 µm. They possessed structures similar to those of carbon nanotubes.IntroductionThe motor vehicles on the road have been increasing annually. World motor vehicle production in 2009 approached 62 million units. Consequently, the consumption of tires has also been on the rise; about 1.4 billion units were produced around the world in 2007 [l]. The disposal of scrap tires is a serious environmental problem. The worldwide disposed of waste tires is almost 1 billion units per year with an expected increase of around 2% each year. However, less than 7% of produced waste tires are recycled (excluding reuse, retreading or incineration). The waste rubber tires are a thermoset polymer, which cannot be reprocessed like thermoplastics polymers, therefore the recycling of this material requires special techniques that demand big investments [2, 3].A solution to the disposal of waste tires is the sequential pyrolysis/combustion process. Past research showed that waste tires are an attractive potential fuel due the high heating value (29-3 7 MJ/kg), which is comparable, or even higher to those of typical bituminous coals [ 4, 5]. Pyrolysis is a process wherein the material is thermally decomposed at elevated temperatures at the absence of an oxidizing gas. Combustion is characterized by the addition of the oxidizing gases during the process. Several studies indicate that the pyrolysis and combustion processes for the tires treatment have a great energy conversion potential [4, 5, 6]."

Jan 1, 2011

By Z. Yang, R. W. Smith, Jr. Wharton

"Microorganisms have the ability to remarkably adsorb and/or absorb heavy metal ions. Hence they are being studied widely as a means of removing metal ions from aqueous solutions both in order to clean up toxic streams and to recover valuable metals from these and other streams. It is often difficult to harvest organisms such as bacteria and unicellular algae since they are usually too small to be readily screened out. Froth flotation may prove to be a feasible method to harvest such organisms subsequent to the ad/absortion of the metal Ions. The present paper discusses the surface/electrokinetic properties of microorganisms and the modifier-collect conditions under which they should float. The zeta potential of the green alga Chlorella vulgaris was measured in the presence of AI(III) and Pb(II) ions and in the presence of dodecylammonium chloride and sodium dodecylsulfate. Present and past data suggest that the organisms should behave similarly to other finely divided, charged (polar) solids with their behavior sometimes modified by the non-polar surface regions present.IntroductionThe overall field of bioengineering is growing at a remarkably accelerating rate. Hydrometallurgy and mineral processing are included among those disciplines where there has been actual or proposed commercial use of bioorganisms. Further, the actual or proposed use includes bacterial enhancement of leaching of a number of different types of ores (1-5), modification of the flotation or oil agglomeration separation of minerals by bacteria (6,7) and microorganism (algae, bacteria or fungi) concentration of metal ions present in effluent or other mineral processing or hydrometallurgy aqueous streams (8-23)."

Jan 1, 1988

By Renate Wellen, Olgun Guven, Mariane Y. T. Oide, Julyana Satana, Francisco Valenzuela-Díaz, Esperidiana Moura

Poly[(ethylene)-co-(vinylacetate)] (EVA) is a thermoplastic copolymer composed of randomly distributed polyethylene and polyvinyl acetate sequences within the molecular chain. EVA combines toughness with excellent flexibility, impact and puncture resistance. Because of these properties, this material is largely used for foam production as padding in equipment for various sports and as a shock absorber in sport’s shoes. This work aims to study the influence of clay reinforcement on the performance of recycled polymer foams. The blend containing recycled HDPE (high density polyethylene) and recycled EVA (70/30 wt%, respectively) reinforced with 2 wt%of clays were prepared by melt extrusion, using a twin-screw extruder to obtain the composites. The composites and foaming agent were fed into a special single screw extruder for foaming. The samples of HDPE/ EVA/Clay foams were characterized by tensile test, Field Emission Scanning Electron Microscopy (FE-SEM), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), density measurement and the correlation between the results was evaluated.

Mar 1, 2018

By A. Broussaud

An original methodology has been developed for steady state simulation of selective grinding and mineral liberation in rod and ball mills. Three fundamental aspects of the methodology are presented successively : modeling ore texture, modeling grinding and its selectivity, and modeling mineral liberation. The methodology for modeling ore texture includes the conversion of 2D data into 3D reconstructed information and the use of the BILCO coherent material balance software. The models for grinding Simulation are classified into three levels, corresponding to three levels of available experimental data. All models account for grinding selectivity and for variations of engineering para-meters and operating conditions. An algorithm has been introduced to forecast mineral liberation, compatible with accurate simulation of selective grinding, which generates reasonable results.

Jan 1, 1987

By Yamei Han, Jiang Du, Jinhui Peng, Mengbi Fu, Libo Zhang, Zhengfu Zhang

"A continuously pilot synthesis by microwave-heating was used in preparing the cathode material LiNi113Co113Mn11302 for Li-ion battery, which used Ni1/3Co1/3Mn1/3(0H)2 and LizC03 as raw materials. Decomposition of the raw materials and synthesis of LixNi113Co113Mn11302 would be fmished in single roasting process. In addition, using microwave-heating would reduce the reacting time largely. Furthermore, the yield of LixNi1/3Co1/3Mn1/302 synthetized in single roasting process was 50 kg. Meanwhile, the effects of Li:(Ni+Co+Mn) molar radio (Li:(Ni+Co+Mn)=l.06, 1.075, 1.09, 1.15) was studied in this paper. XRD, SEM and EIS were used in characterizing the cathode material. The results showed that the best Li:(Ni+Co+Mn) molar radio was 1.075. It was found that the LiNi113Co113Mn11302 synthetized with Li:(Ni+Co+Mn)=l.075 had homogenous distribution of particles and ideal layered structure. The galvanostatic charge-discharge(O. l C, 2. 75-4.3V, vs. Lt /Li) tests showed that the initial discharge capacity of the LixNi113Co113Mn11302 was 159.5mAh·g-1, and the discharge capacity was 157.6mAh·g·1after10 cycles.IntroductionRecently, as the cobalt was expensive and the restriction of dynamic power, the commercial cathode Li2Co02 which was expensive, toxic, and high pollution had exposed its defects[1·2l. Since T.Ohzuku[3l first reported the layered LiNi113Co113Mn11302, this material had high reversible capacity and caused the attentions of researchers[4l. Its reversible capacity was l 60mAh/g and 200mAh/g in the voltage range of 2.75-4.3V[5-61. But for the present, preparing LiNiwCowMnw02 by traditional had lots of disadvantages, such as the long heating time, the high cost and the volatizing of lithium and so on[7-9l. According to these, traditional prepatation wasn't good for sustainable development and energy conservation."

Jan 1, 2013

By Larry G. Twidwell, Jannette L. Chorney, Bryce D. Ruffier, Katelyn M. Lyons, Daniel W. Gaede, Ryan J. Foy, Jerome P. Downey

The Army Research Laboratory (ARL) has an interest in the recovery and processing of rare earth elements. At Montana Tech, elevated temperature chlorination of rare earth oxides is presently being investigated as a potential methods leading to the selective separation and recovery of rare earth elements from mineral ores and concentrates. After preliminary evaluation, ytterbium oxide was selected as a representative surrogate material for more extensive chlorination studies. Methods used to determine the conversion and recovery include X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis. These data have been used to establish and confirm process conditions that consistently yield high conversion efficiencies. Based on the promising results, further experimentation is underway to ascertain the metallurgical response of other rare earth oxides and carbonates to the roasting process. The end goal is to create a robust process for industrial application that has greater efficiency and reduced costs as compared to current practice.

Jan 1, 2015

By Onuralp Yucel, Osman Halil Celik, Hakan Morcali

In this study, some experiments were performed for the dimensional control, pre-treatment, getting salt, metallic aluminum and aluminum oxide into the solution of 15 kg aluminum black dross obtained from a private company which recycles aluminium drosses. Water leaching experiments are done for removing salts and aluminum nitride. Temperature stirring speed, solid-liquid rate are investigated while water leaching experiments. Removing of AlN is provided at 25 °C at a rate of 42.48%, at 80 °C at a rate of 86.4%. Leaching experiments performed with NaOH. NaOH concentration and time was analyzed. Efficiency of including metallic aluminum into the solution is determined to be 98% approximately. Melting (fusion) experiments were performed with NaOH at high temperatures to include aluminum oxide in the structure of the remaining after dissolving process into the solution and after dissolving the resulting structures in water, efficiency of including aluminum into the solution is determined to be 85%.

Mar 1, 2018

By W. Drummond

The cooling of smelter gases by air dilution, adiabatic evaporative cooling and indirect heat exchange is discussed with reference to the process, to the subsequent cleaning of the gas. and to the use of the heat extracted from the gas. The method of reducing the effect of acidic sulphide formation on the corrosive properties of the gas and the dust and the development of surface cleaning mechanisms?are discussed. The development of indirect recuperators using air, water or steam cooling, made possible by the control of surface fouling is traced. The application of the modern Waste Heat Boiler to the new sulphide smelting processes is discussed with respect to the natural and forced circulation concepts. Case histories are presented to illustrate mistakes made with respect to designs produced without recourse to sensitivity analysis and without an appreciation of "worst process? conditions".

Jan 1, 1992

By Mike Johnson, Greg Andrews, Niels Verbaan, Ernesto Bourricaudy, David Dreisinger

Search Minerals has developed a Direct Extraction Process for recovery of rare earths from the Foxtrot and Deep Fox deposits in Labrador Canada. The process includes crushing, acid treatment, water leaching, impurity removal, precipitation of an intermediate rare earth product and finally re fining of the intermediate product to produce a high purity mixed rare earth oxide (*99% total rare each oxides). The Direct Extraction Process has been validated in an extensive demonstration pilot plant program at SGS Minerals. A total of 3 tonnes of material was processed to produce final mixed rare earth product. The results of the demonstration pilot plant program are reported.

Mar 1, 2018

By Lilong Zhu, Shaoda Zhang, Qian Wang, Shengping He

The effects of ZrO2, Y2O3 and Sc2O3, which are transition metal oxides, on the melting temperature, viscosity at 1300 °C, and break temperature of three mold fluxes (two weak-reactive type and one non-reactive type) designed for the high manganese and high aluminum steels, and one another conventional CaO-SiO2 based mold flux is studied. The results indicate that the melting temperature and viscosity increases slightly, and the break temperature increases dramatically with the addition of ZrO2, Y2O3 and Sc2O3 content in the conventional CaO-SiO2 based mold flux system. While, the addition of ZrO2, Y2O3 and Sc2O3 in the weak-reactive or non-reactive mold flux systems has a negligible in fluence on the melting temperature, viscosity and break temperature, suggesting that these transition metal oxides are possible to regulate radiation heat transfer without changing the basic properties of mold fluxes.

Mar 1, 2018

By Y. Suzuki, J. Nagao, Y. Ueda, K. Shimokawa

"A Ti- Ni intermetallic compound could be formed rapidly from Ti and Ni powder compact with SHS process. Microgravity experiments using a drop shaft are carried out, This report shows the effect of microgravity or high gravity on formability of an intermetallic compound. It is concluded that the specimen forms a porous and nearly amorphous alloy by rapid cooling under microgravity but with rapid cooling under high gravity after microgravity, the specimen forms a uniform and dense structure with better crystallinity.IntroductionTi - Ni inter1etallic co1pounds have been produced and have beco1e si1ilar to the a1orphous and porous structure as a result of the SHS (Self Propagating High-te1perature Synthesis) process under 1icrogravity. SHS process is being applied to the synthesis of cera1ics and inter1etallic co1pounds (1). The technique is characterized by a large a1ount of heat being emitted within a very short ti1e interval as regards the sistering reaction. One SHS process, acco1panying 1elting by a reaction was observed, and that was due to the quick heating of a Ni-Ti co1pact containing 50 ato1ic percent of Ti under a low pressure (2-4). In this report, we have researched the use a drop shaft which is 1ore effective during a short ti1e under 1icrogravity and high-gravity, so as to obtain high dense speci1ens with the exception of porous specimens (5). Mechanical properties of each specimen were esti1ated from these 1icro-structures with a discussion about the effect of changing gravity regarding 1elting and solidification of the Ti-Ni intermetallic comounds."

Jan 1, 1996

By Varadarajan Seshadri

The performance of mould fluxes in satisfying its quality requirements can have a significant effect on the efficiency of the continuous casting process and on the surface quality of the products. This performance is affected by various parameters including the characteristics of the mould fluxes, the quality of the steel being cast and the operational conditions of the caster. The extremely complex relationships involving the parameters mentioned above make it very difficult to have simple criteria for selecting mould fluxes for casting a certain grade of steel in a continuous casting machine. These difficulties led steelmakers and mould flux suppliers to select mould fluxes based mainly on plant trials. In the present work, a software to help in the analysis and development of mould fluxes for continuous casting was developed_ This software includes several models for prediction of mould flux viscosity and consumption. A mathematical model was also used to predict the heat flux through the mould flux. The proposed methodology was applied to continuous casting of crack sensitive steels_ Some of the results given by this software are presented, discussed and compared to plant data.

Jan 1, 2003