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By Cao rong-jiang, Tang Xin-he

"In ordinary manufacture process of tungsten powder, a preferable intermediate product used is ammonium paratungstate (APT). The particle size of tungten powder made from it through W2OO58 is larger than 1. 0 um. In order to obtain ultrafine tungsten powder with narrow size distribution, a new type of tungstate, hydraziniull tungstate, was studied. Its formula is 5(N2H5)2O·12 WO.s , with tetragonal crystal structure of a=5.821 , c=18. 468. Three methods for preparing hydrazinium tungstate (ART) were set up and ART can be produced by current industrial APT process with little modification of operation and without any change of equipment.Under certain PH and operation condition of the solution from which ART was produced, an autoreduction of tungsten occured, which produced a lower valency tungstate with blue color when ART was heated at different temperatures, in N atmosphere, tungsten bronze, tetragonal W0290 and W02.7E could be obtained respectively. They all have the superiorities, in the production of tungsten powder, of superfine size and narrow size distribution [average size of 0.5um or even smaller.The rate of autoreduction of ART is very fast at elevated temperature. The reduction reaction, which gaves tetragonal WO290, could be handled smoothly without explosion. To research their behaviors at autoreduction temperatures and the products of autoreduction will be new advances of tungsten chemistry and may also serve tungsten industry with new processes and materials."

Jan 1, 1988

By Jr. Santafé, Lucas L. da Costa, Felipe P. D. Lopes, Sergio N. Monteiro

"Residual vegetable fibers as leftovers from crops, industrial activities and consumable items are realistic options to be incorporated into low cost polymeric composites with the aim of replacing other commonly used materials. The present work assesses the technical properties of epoxy composites reinforced with residual fibers from the coconut fruit, also known as coir fibers. Based on these properties, an evaluation was carried out on these coir fiber/epoxy matrix composites to be used as building panels and furniture in comparison with conventional materials.IntroductionThe utilization of waste from industrial activities is presently recognized as important way in preventing environmental pollution as well as developing new products. This utilization would also generate employment and contribute to environmental improvement in global scale. Among such wastes, those from lignocellulosic materials represent a considerable potential for practical application. In fact, about 2.5 billion tons of these materials are currently available [1], and their fiber content is an important option for composites fabrication. Actually, lignocellulosic fibers are now replacing synthetic fibers as reinforcement in resin matrix composites owing to specific advantages such as low cost, biodegradability and renewable characteristics [2,3]. Moreover, as abundant waste, some of these lingocellulosic fibers could help reducing the use of traditional materials like wood and plastics in many industrials applications. This would prevent further stress on the environment caused by depletion of dwindling resources associated with forests and petroleum."

Jan 1, 2008

By Rick Honaker

Rare earth elements (REEs) contained in coal and associated mineral matter exist in several forms including micro-dispersed minerals, ion adsorption onto clay surfaces, and chemically bound. Tests found that REEs can be effectively recovered from certain components of three coal sources by leaching under mild conditions followed by solvent extraction. A range of pH values were evaluated at solution temperatures of 25 and 75 °C. When using 1.2 M of sulfuric acid, nearly 85% recovery of the REEs was extracted from the middlings material collected from an operating plant. Acid leaching of a second middling source from another plant resulted in 60% of the total REEs being recovered under the same leaching conditions. Solvent extraction treatment of the leachate produced from six different coal sources resulted in products containing up to 50% total REEs from feedstocks starting with around 300 ppm.

By P. Meyers, F. DeSilva, L. Gottlieb

A number of tests looking at lead removal using ion exchange resins of various types from various aqueous streams have been undertaken. The tests focused on strong acid cation (SAC) and weak acid cation 0N AC) resins. It was found that the mechanism of lead removal is partly by lead filtration rather than solely by ion exchange in a large portion of the applications studied. This is not surprising since lead carbonate is essentially insoluble and almost all water supplies contain at least some carbonate alkalinity. Regeneration of lead from exhausted resins containing significant amounts of lead may not be practical in some cases because of the large chemical and waste volumes involved. Since lead, .·along with many other very insoluble metals, is often present as a suspended solid rather than in ionic form, ion exchange is probably not always the best technology for bulk lead removal.

Jan 1, 2000

By C. A. Young

The remediation of cyanide (CN-) and nitrate (NO)-) anions in mine and agricultural waters by various photolytic methods has been reviewed and investigated. Photolytic methods such as direct photolysis, homogenous photolysis, and heterogeneous photocatalysis are briefly described and compared. Results and discussions show that each method has certain advantages and disadvantages. For each method, Eh-pH diagrams prove useful for determining reaction mechanisms. Preliminary results obtained for cyanide oxidation and nitrate reduction show that homogeneous photolysis can be superior due to faster kinetics than the other methods. The photolytic methods were individually, not simultaneously, tested and compared. Differences in concentrations of products were obtained and attributed to differences in photoconversion efficiencies and other inherent characteristics of .the photolytic methods. Various reaction mechanisms are proposed in accordance with the literature as well as measurements obtained from solution analysis using ion selective electrodes and ion chromatography .

Jan 1, 1995

By J. Bostjancic

As wastewater discharge regulations become more stringent, power plants, manufacturing plants and other industrial sites are looking for ways to reduce makeup water requirements and to recycle and reuse as much wastewater as possible. In some cases, environmental regulations require zero liquid discharge, meaning all wastewater must either be retained on site or reduced to solids for disposal off site. Zero liquid discharge or "closed-loop" wastewater treatment systems using evaporators and other process equipment have been well-accepted in recent years. Often overlooked is the fact that zero discharge is not just the latest fashion--many commercial zero liquid discharge systems have been in operation since the mid-70's. This paper will give specific examples of zero liquid discharge operations from 1974 to the present, showing how evaporation equipment and processes have changed to meet the requirements of industry and environmental regulations.

Jan 1, 1996

By Laurent Cohen

Since the 1970s, Solvent Extraction (SX) in hydrometallurgical processes has been a key enabling technology in the production of high-purity metals. Examples include copper, rare earth oxides, uranium, cobalt and nickel. Notwithstanding incremental improvements in extractant formulations, few breakthroughs can be recounted in this industry outside of the initial amine-, oxime- or phosphine-based reagent chemistries. However, the advent of lithium-ion batteries and their stringent requirements for critical materials (lithium, cobalt and nickel) offer new challenges and opportunities for SX. Solvay recently introduced a new extractant for lithium, CYANEX® 936, and developed unique modeling software capabilities in cobalt/nickel separation using CYANEX® 272, zinc SX using DEHPA® and rare earth separations using CYANEX® 572. This paper discusses trends in SX and provides insight on processing of critical materials essential to energy sources. It also summarizes the technical and economic benefits based on extractant selection and advances in modeling.

By Hideaki Tokuyarna

Recovery of metal such as V, Ni and Fe from oil fly ash is important for efficient use of natural resources and protection of environment. Leaching of metals from fly ash followed by ion exchange of leached metals has been examined to develop a process which can selectively recover V and Ni from the fly ash. Experiment of leaching with water, HCI, H2S04 and NaOH leads us to propose a two-step leaching process as an effective and mild operation. The first step is leaching with water for removal of Ni, Mg, A1 and Zn and the second step is leaching with acidic solution for the recovery of V. The metals V and Ni are then separated from other metals in each leached liquor by ion exchange. Advantage of this separation process is that acidic leachant can be reused, which contribute to save separation energy.

Jan 1, 2002

By Karin Soldenhoff

Recovery of uranium in conventional ion exchange circuits, using strong base or weak base resins containing quaternary or tertiary amine functional groups, is based on an anion exchange mechanism. In saline liquors, chloride competes with uranium for the active resin sites and reduces resin loading. This results in significant negative impacts on the IX process in terms of plant throughput and operating costs. In this paper we present the results of a study on the recovery of uranium from an acidic in situ leach liquor containing approximately 9 g/L chloride. A range of resins was tested, and a high capacity strong base resin was identified with significantly enhanced loading compared to conventional resins. Other process-relevant criteria such as loading kinetics and elution efficacy are also discussed. The process developed was successfully tested during a recent ion exchange pilot plant operated in conjunction with a field-leach trial.

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

Sinter is an important iron-bearing material charged into blast furnace. Calcium ferrite (CF) is one of the most significant liquid phases in fluxed sinter. The isothermal reduction kinetics of CF and CF8M (n(CaO):n(Fe2O3) = 1, wt%(MgO) = 8) with 30% CO and 70% N2 gas mixtures at 1123, 1173, and 1223 K were investigated through thermogravimetric analysis in this study. Rate analysis illuminates that the reduction processes of CF and CF8M are mainly expressed as a typical two-stage reaction. Sharp analysis indicates that CF and CF8M reduction is expressed by the Avrami–Erofeev equation presenting a 2D shrinking layer reaction. The apparent activation energy values of CF and CF8M reduction are 46.9 and 31.8 kJ mol−1 individually based on model-free method.

Mar 1, 2018

By Chao Li, Shi Sun, Hongxu Li, Jiaqi Fan, Qi Liu

With the great demand of consumer electronics (CE) and electric vehicles (EV), cobalt has become one of the more scarce energy metals.The recovery of cobalt from a copper converter slag, which contained over 2.4% Co and was accumulated as industrial waste, by reduction-sulfurization smelting was explored. Quantitative analysis of treated slag showed that activated carbon and ferrous sulfide can be used to settle cobalt into matte as Co–Fe alloy. The experiment was carried out at 1673 K with a reducing atmosphere of burning electrode graphite crucible. It was found that the recovery of Co would increase within creased added activated carbon, was unaffected at higher carbon additions, and for low additions of carbon increased at higher FeS additions. Over 95% Co, 99% Cu and 62% Fe could be settled into matte. Preliminary separation of Co from converter slag by pyrometallurgical smelting is proposed.

Mar 1, 2017

By Dietrich Gross

This paper describes an advanced oxy-fuel combustion technology for re-melting aluminum that significantly reduces energy consumption and emissions. This oxy-fuel combustion technology developed by Jupiter Oxygen is a patented process for combustion of fossil fuels with pure oxygen while excluding air, thereby creating an undiluted high flame temperature and increased efficiency for process heating in industrial furnaces. This unique process has led to improved heat transfer and longer residence time while maintaining the same process temperatures as with air combustion. The energy efficient combustion process allows aluminum companies to operate at a substantially lower cost due to a dramatic fuel savings of up to 70% for natural gas and waste oil (1). The results of more than 10 years of day-to-day experience utilizing the Jupiter Oxygen Corporation oxy-fuel combustion technology licensed to Jupiter Aluminum Corporation in the aluminum re-melting business are discussed.

Jan 1, 2008

By Guangqing Zhang

The paper presents results of a systematic study of synthesis of titanium oxycarbide and its chlorination. Titanium oxycarbide was produced by carbothermal reduction of titania in hydrogen, argon and helium. Formation of titanium oxycarbide started at 1200°C in all gases. The reduction was the fastest in hydrogen. Formation of titanium oxycarbide in hydrogen was close to completion in 120 min at 1300°C, 60 min at 1400°C and less than 30 min at 1500°C. Reduction in argon and helium progressed at a similar rate and reached 90-95% after 300 min at 1400-1500°C. The chlorination of titanium oxycarbide was ignited at 150-200°C. Chlorine partial pressure and gas flow rate strongly affected the chlorination rate. Chlorination of titanium oxycarbide produced with carbon to titania molar ratio 2.5 at 235-400°C was close to 100% in 30 min.

Jan 1, 2009

By Ahmet Geveci

In this work it is aimed to assess the plant analytical data which appeared during efforts to decrease the effect of carry-over slag (basic oxygen furnace slag) that can not be prevented to leak during tapping of steel in the ladles. While the amount changes, carry-over slag that escaped to ladle, consists of appreciable amount of reducible oxides (?FetO? and MnO) which act as oxygen source for steel bath. By using aluminum dross, containing %30-35 metallic aluminum, which is a non-recoverable process outcome (discard) for most of the aluminum factories, slag reduction behavior will be analyzed together with other parameters such as reaction time, initial amount of total Fe+MnO, amount of reducing agent and reducing effect of soluble aluminum in steel bath while obtaining a slag composition which promotes higher desulphurization capacity and inclusion removal for liquid steel.

Jan 1, 2006

By Kejun Liu

Platinum and palladium are usually dissolved together and followed by separation. In this study, the selective leaching of platinum and palladium from a secondary resource, such as dental waste, by using chloride solution (hypochlorite and chlorate) has been developed. Results indicate that about 100% of palladium could be initially extracted by the combination of 0.3 mol/L sodium hypochlorite (NaClO) and 0.068 mol/L sodium chloride (NaCl) at pH 1.2 and 298K in 1.5 hours, or the combination of 0.005 mol/L sodium chlorate (NaClO3) and 6 mol/L hydrochloric acid (HCl) at 298K in 0.5 hour. About 100% of platinum could be extracted from the residue by the combination of 0.47 mol/L sodium chlorate (NaClO3) and 12 mol/L hydrochloric acid (HCl) at 298K in 2 hours.

Jan 1, 2003

By Naoki Hiroyoshi

It is generally accepted that ferric ions are effective for leaching chalcopyrite as an oxidant and ferrous ions contribute to the leaching only as a source of the oxidant ferric ions. However, this paper shows that ferrous ions are more useful for leaching chalcopyrite than oxidant ferric ions in sulfuric acid solutions in air at ambient temperatures. Leaching experiments and dissolved oxygen consumption measurements were carried out with a very pure chalcopyrite and 0.001 - 1 mol dm-3 sulfuric acid solutions containing 0 - 0.1 mol dm-3 ferric or ferrous ions at 303 K. Chalcopyrite oxidation with dissolved oxygen was promoted by ferrous ions but suppressed by ferric ions. As a result, the amount of extracted copper was larger with ferrous ions than with ferric ions. Effects of Thiobacillus ferrooxidans on the ferrous promoted chalcopyrite leaching were also investigated and discussed based on the experimental data.

Jan 1, 1999

By P. Henry

A novel electrochemical cell has been developed for the recovery of MnO2 from residue of pyrolusite ore leading loaded with Fe, Al Ni, Co and Si impurities, This new process can be considered as an alternative to the traditional methods : S02, H2O2 or bioleaching. It has been observed to proceed fairly rapidly and could prove to be a more economically viable process, as well as being more environmentally acceptable. Electrochemical characterization and kinetic studies have shown that MnO2 is effectively leached by electrogenerated ferrous ions at high current density from a pulp containing less than 5 g8 Fe. The chemical reactions are : Cathode (inox) : 2F23+ + 2e ? 2 Fe2+ Bulk: MnO2 + 2 fe2+ 4H+ ? Mn2+ + 2 Fe3+ + 2 H2O Anode (Pb-Ag) : H2O ? ½ O2 + 2H+ + 2e Global: MnO2 +2H+ Fe2+ = Mn2+ + H2O + 1/2 O2 The catholyte (MnO2 pulp) circulates upward in the expanded mesh cathode separated from the sulfuric acid solution anolyte by a separator which shows high mechanical resistance, low porosity, low potential drop, and reasonable cost. Laboratory and mini-pilot tests have led to the construction of an OT crating pilot plant (100 kg/hr) able to leach more than 95% of Mn, Ni, Co at 1000-1200 A/m2, 50°C with high faradic yield (> 95 %) and low power consumption (3.2 kWh/kg kWh/kg &4D). New applications like the treatment of spent Zn-Mn batteries, polluted soils, spent catalysts and oxide ore (cobalt, nickel) with electrogenerated redox species are now investigated at a laboratory and mini-pilot scale.

Jan 1, 2000

By Lori Bassman, Cassandra George, Cullen McMahon, Md. Zakaria Quadir, Michael Ferry

"Complete and accurate analysis of subgrain microstructural features must include three-dimensional information. Three-dimensional electron backscatter diffraction (EBSD) data can be used to characterize these features; however their boundaries first must be determined. This cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast Multiscale Clustering (FMC) is an established image processing technique that we have combined with quaternion representation of orientation to segment this kind of data. Segmentation algorithms often have issues handling images with both distinct and subtle boundaries. Our implementation of FMC addresses this by using a novel distance function and statistical analysis to take into account the variance in orientation of each feature. Although FMC was originally a twodimensional image processing algorithm it can be generalized to analyze threedimensional data sets. As an example, a segmentation of microbands in cold-rolled aluminum is presented.IntroductionThree-dimensional electron backscatter diffraction (3D-EBSD) is a method for mapping the local crystallographic orientations of points in a volume. The technique uses a dual beam platform consisting of a focused ion beam (FIB) and SEM with EBSD, where FIB is used for serial sectioning and EBSD for orientation mapping of 2D slices. These 2D slices may then be stacked to create a 3D volumetric data set.Typical uses of such a data set include characterizing the geometries and crystallographic orientations of surfaces between structures in 3D [1-5]. This involves identifying boundaries accurately, either in 2D slices with subsequent 3D reconstruction (as illustrated in Figure 1) or in the 3D data set. All such data sets present the challenges of i) aligning data slices to correct for instrument drift, ii) identifying relevant boundaries, and iii) implementing appropriate smoothing or interpolation algorithms. The focus of this paper is boundary identification."

Jan 1, 2011

By Y. W. Chung, W. I. Chia

"The interaction of water vapor with single crystal Ni3(Al,Ti) and polycrystalline Ni3Fe, with and without the presence of oxygen, has been studied with Auger electron spectroscopy, photoemission spectroscopy, thermal desorption and isotope exchange. Water dissociates to produce atomic hydrogen above 200 K on both Ni3(Al,Ti) and Ni3Fe surfaces. For Ni3(Al, Ti), the reaction is structure-sensitive. Pre-adsorbed or co-adsorbed oxygen on Ni3(Al,Ti) and Ni3Fe significantly suppresses hydrogen production due to water dissociation. This suppression process occurs more efficiently on Ni3Fe than Ni3(Al, Ti).IntroductionOrdered intermetallic compounds such as aluminides, silicides and titanides are very attractive for structural applications at high temperatures. This is because these intermetallics tend to form adherent oxides in oxidizing environments which protect the base materials from excessive oxidation and corrosion. In addition, they have low density, relatively high melting points and good high-temperature strength. However, the moisture in air severely embrittles many ordered intermetallics such as FeAl [1-3], Fe3A1 [4,5], C03Ti [6,7], (Co,Fe)) V [8], Ni3Si [9], Ni3(Si,Ti) [10], Ni3(AI,Mn) [Ill, and Ni3A1 [12-14], resulting in low 'ductility and brittle fracture at room temperature. Recent studies by Liu and coworkers (see review by George and Liu [15]) provide a qualitative description of the mechanism for this moisture-induced embrittlement. During elongation testing, cracks are formed, thus exposing fresh alloy surfaces. One or more active components of the alloy react with water vapor in the environment to produce atomic hydrogen which penetrates into crack tips and causes hydrogen embrittlement. This is similar to that proposed for moisture-induced embrittlement of aluminum alloys [16]."

Jan 1, 1996

By Naiyang Ma

"High oil concentration is one of the major barriers for recycling of mill scale of steel hot rolling mills. It is of vital importance to find cost-effective technologies of reducing oil concentration in mill scale in order to recycle the mill scale without causing detrimental effects on production and environment. This paper discusses in-process separation of mill scale from oil at steel hot rolling mills. Formation of mill scale and status of oily wastewater at hot rolling mills are reviewed in the first place. A mathematical model is then formulated to relate oil concentration in mill scale to physical properties of mill scale, chemical and physical properties of wastewater and interacting parameters between mill scale particles and wastewater. From this model, three approaches of in-process separation of mill scale from oil are derived: (1) avoiding contacts between mill scale particles and oily wastewater, and (2) maintaining low oil concentration in wastewater, and (3) collecting mill scale in upper streams of wastewater flows. In-process separation of mill scale from oil might have advantages of lower capital cost, lower operating cost and less additional environmental concerns, compared to other strategies of separating mill scale from oil.IntroductionHot rolling is an inevitable step in producing finished steel products. Figure 1 schematically shows a steel hot rolling process. Semi-finished steel products, slabs here, are reheated first, and then the reheated slabs are discharged from the furnaces and transported on hot rolling trains to descaling units for removing scale with pressurized water. After being descaled, the slabs are rolled by roughing mills. After treated with cropping and the second descaling, the slabs are finally rolled into finished products, coils here, by finishing mills."

Jan 1, 2012