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By S. Mattlgod

Self-assembled monolayers on mesoporous supports (SAMMS) have been developed for the removal of heavy metals and some transition metals. The thiol functional groups were assembled on the internal and external surfaces of mesoporous silica with a uniform pore size of about 55 A. The mesoporous supports provide high surface area (>900 m2/g) needed for high metal loading in chemical separation. Self-assembled monolayers of organic molecules bond to the ceramic substrate with prescribed densities, and with terminal functional groups for excellent molecular selectivity. The unique characteristics include: (1) High metal absorption capacity, up to 3.2 mmol/g of SAMMS. (2) Fast Hg-binding kinetics (reducing mercury concentration from 0.5 ppm to 0.5 ppb in less than 5 minutes). (3) High selectivity in the presence of a range of cations, anions, and organic species. (4) Applicability in both aqueous and non-aqueous solvents. (5) Flexibility in surface chemistry. The materials can be designed to adsorb heavy metals, transitional metals, and radionuclides. (6) Chemical stability, and potential for regeneration or waste storage. This paper discusses the results on mercury adsorption.

Jan 1, 1999

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By C. Lupi

Electric arc furnace dust generated during the production of steels is regarded as hazardous waste because of the presence of leachable elements such as Cr, Pb, Cd .... Different processes are available according to the management policy chosen by the steelmaker: disposal. recycle and/or recovery. The feasibility of an hydrometallurgical Zn recovery process on fumes generated during the pyrometallurgical treatment of EAF dust has been investigated. The recovery of metallic iron, chromium and nickel as molten metal provides fumes very rich in zinc oxide ( 63.1% ) and poor in zinc ferrite. This secondary dust is still an hazardous waste and represents the raw material for the recovery of Zn and Pb. The waste material is first leached in 1.5 M sulphuric acid at 30°C to provide a Zn, Fe and Mn rich aqueous solution and a Pb and Ca sulphate rich sludge. The iron is eliminated by precipitation because is harmful to the following electrowinning process. The ftltered and purified leached solution is acidified in order to obtain good electrowinning conditions. A pure cathodic deposit of zinc is then produced in an electrolytic cell at laboratory scale.

Jan 1, 1996

By Junji Shibata

Heavier rare earth, which is contained in a small amount in ores such as bastnesite and monazite, has been accumulated as a heavier rare earth residue without doing separation and purification due to the lack of suitable methods. The heavier rare earth residue includes seven rare earth elements such as Tb, Dy, Ho, Y, Er, Tm and Yb. Separation and recovery process of Dy, Y, Tm and Yb from leached solution of the heavier rare earth residue was investigated by using a column method with solvent impregnated resin. The solvent impregnated resin was prepared by impregnation of organophosphorous extractant whose trade name is PC-88A into a macro porous resin, Amberlite XAD-7. It was almost impossible to separate them in simple adosorption and elution steps. However, we attained to individually separate Dy, Y, Tm and Yb from the leached solution first by changing eluent concentration gradually from pH2 to 0.02kmol/m3 HC1 in the elution step, and secondly by using a development column and changing eluerit concentration in the elution step. The separation process flow was proposed for a heavier rare earth residue by using the solvent impregnated resin method.

Jan 1, 1998

By Pan Gu, Zhen Zhang, Jiang Diao, Bing Xie, Hongyi Li

Viscosities of FeO-SiO2-V2O3-CaO-P2O5 slags have been measured at the temperature range of 1673 K to 1773 K (1400°C to 1500°C). This investigated system represents the major components of basic vanadium slag that is an important intermediate product of a novel vanadium extracting process, in which removal of phosphorus and extraction of vanadium can be achieved from the vanadium-containing hot metal simultaneously. It was found that higher CaO/SiO2 ratio resulted in lower viscosity in the composition range of interest. Also, the viscosities increase with the increasing P2O5 concentration. The varying viscosities can be attributed to the modification in complexity and polymerization of the slag network. The variation of apparent activation energies are in tune with the viscosity measurements. The results of this work revealed the effect of CaO/SiO2 and P2O5 on the viscous properties of FeO-SiO2- V2O3-CaO-P2O5 slags and therefore provide the theoretical foundation for the control of the coupling de-P and V-extraction process.

Jan 1, 2016

By Linfeng Zhou, Rong Sun, Guanghui Li, Zhiwei Peng, Tao Jiang

Dust, or airborne particulate matter, from metal smelting can be either mechanically or thermally generated and it negatively affects the indoor air quality as well as the fugitive emissions from the plant. The thermally generated dust is often referred to as fume and it is typically generated whenever liquid metal comes into contact with air. For practical reasons, such as vehicle access, etc. it is often difficult to collect 100% of the fume. It is therefore highly desirable to develop processes and optimize operational procedures so that fuming can be kept to a minimum. In this series of experiments, the mechanism of active oxidation and fume formation from liquid silicomanganese under an impinging air jet in the temperature range 1400-1600°C has been explored. Characteristic properties of the fume have been established; particle diameter, shape, size distribution, and elemental composition are reported. The oxidation process is described in terms of vaporization, oxidation and agglomeration. In the boundary layer, two competing mechanisms seem to be operative in parallel: a direct oxidation of Mn vapor, and a two-step oxidation of silicon. The thermodynamic and kinetic conditions governing the two mechanisms are discussed.

Jan 1, 2016

By Xingye Guo, Yeon-Gil Jung, James Knapp, Zhe Lu, Jing Zhang, Li Li

La2Zr2O7 is a promising thermal barrier coating material due to its low thermal conductivity and superior high temperature stability. In this work, Bilayer La2Zr2O7 and conventional 8 wt% yttria stabilized zirconia (8YSZ) coatings were deposited using plasma spray technique. Both singlelayer La2Zr2O7 and double-layer 8YSZ/La2Zr2O7 coating architectures were designed. Thermal cycling and thermal shock tests were used to evaluate coatings’ thermomechanical properties. All La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. In the jet engine thermal shock (JETS) tests, the SCL La2Zr2O7 and DCL dense 8YSZ/La2Zr2O7 coatings were fully delaminated. In contrast, the DCL porous 8YSZ/La2Zr2O7 coating sample only partially delaminated on the edge. This is because of the porous 8YSZ layer provides strain compliance. The findings will help to propose efficient thermal barrier coating systems.

Jan 1, 2016

By P. Hanniala, J. Sulanto

"The requirement for the reduction of sulphur dioxide emissions from copper smelters is becoming more and more important. Therefore, the most important question in smelting technology will be how to produce even, high strength SO2 gas in smelter and how to combine smelting and converting. The best sorution in certain cases is to eliminate converters totally.Outokumpu is already responding to this challenge. As a result of extensive research work, Outokumpu Oy has developed the Flash Smelting Process for direct smelting of blister copper from concentrates in one step.The newest process development is the Kennecott-Outokumpu Flash Converting process, where solidified copper matte is converted into blister copper. The production of low volume high SO2 content gases, separation of smelting and converting operations to allow increased on-line availability, and simplified process control are the major benefits of the process which translates to reduced smelter capital and operating costs.Also, it has been studied the use of the same Outokumpu furnace for smelting and converting alternately when the production capacity is low.In this paper, the developments and improvements of the Outokumpu Process are described from the operation and investment cost standpoints"

Jan 1, 1988

By Shaohua Ju, Huang Chang-yuan, Lu Shuaidan, Peng Jin-hui, Wu Guoqin, Yaqian Wei, Zhang Li-bo

"The contrastive studies of microwave and conventional roasting copper residue from zinc hydrometallurgical was carried. The experimental results showed that the microwave roasting has the higher dechlorination rate in the same condition such as temperature, heat preservation time and atmosphere. When the samples with 100 mesh grain size, the Cl content turned from 14.27% to 1.33% and the dechlorination rate achieved over 90% at 400°C with 2h microwave roasting. And in the same conditions, the materials' dechlorination rate after conventional roasting just reached around 78%. The phase changes of the roasting process was investigated with X-ray diffraction analysis.IntroductionCl element can be accumulated gradually in the solution of Zinc hydrometallurgical system. When Cl content in electrolysis solution comes up to 100 mg/L, the stability of electrodeposits process would be severely affected [ 1]. It would not only accelerate the consumption of cathode and anode plate, elevate the power consumption, but also cause serious corrosion of device, increase production costs and lower the quality of electrolytic zinc [2]. Thus, C1- contained in the solution should be removed before electrodeposits."

Jan 1, 2013

By Dan Adams

A number of gas-liquid processes require high intensity agitation systems to provide uniform blending and dispersion of reactants in order to achieve desired end products. Processes such as hydrogenation, fermentation, and minerals processing have used conventional down pumping or radial agitation systems with some success. In 1996, LIGHTNIN introduced the concept of Up-Pumping to the industrial marketplace as an improved mixing technology for these applications. For processes requiring gas-liquid mass transfer, such as those listed above, conventional mixing technology requires the use of gas introduction devices (sparges) below impellers. These devices can be a maintenance concern due to plugging and erosion in the presence of solids. Up-Pumping impeller systems are able to draw in a significant amount of gas from the headspace, much more so than conventional vortexing impellers designed for headspace gas incorporation. This paper will demonstrate the effectiveness of Up-Pumping impeller systems that have the potential to eliminate need for sparge devices entirely. It demonstrates the ability of Up-Pumpers to re-entrain gas for higher utilization compared with conventional impeller technology. This is significant in applications using costly gases such as enriched oxygen or hydrogen, reducing overall operating costs of production.

Jan 1, 2003

By B. C. Tripathy

The effects of alkali metal ions Li+, Na+, K+and transition metal ions Cr3+ and Mo6+ on the cathodic current efficiency, deposit quality, crystallographic orientations, deposit morphology and polarisation behaviour of the cathode during nickel electrocrystallisation on stainless steel substrate from aqueous sulphate solutions containing boric acid were investigated. The alkali metal ions had virtually no effect on the cathodic current efficiency, deposit quality, crystallographic orientations, deposit morphology and cathodic polarisation. On the other hand, there were significant variations in the current efficiency and deposit characteristics when Cr3+or Mo6+ were present in the electrolyte. Current efficiency decreased by more than 10% even at lower concentrations (> 100 mg/L). Similarly purity of the deposits was affected by the presence of either of the metal ions. In the presence of Cr3+, there was progressive shifting of the nucleation potential of nickel towards more negative values, whereas, in the case of Mo6+the nucleation potential shifted initially towards positive values in the concentration range 2-40 mg/L, but then towards negative values when its concentration exceeded 40 mg/L.

Jan 1, 2003

By K. Takahashi, G. Dodbiba, T. Fujita, N. Sato, S. Matsuo, K. Okaya

Different materials are used for manufacturing various parts of a cellular phone. Considering that a great number of mobile phones are being discarded every year, it is important to recover these materials and then recycle them in order to save resources. The primary objective of this work is therefore to find and suggest ways on how to recover various materials from discarded cellular phones for recycling. Much effort, for example, has been put in recovering and recycling tin oxide (ITO), a mixture of indium (III) oxide, (UI2O3) and tin(IV) oxide from the discarded liquid crystal displays (LCDs). Here we report a simple and cost-effective process, which includes a HC1 treatment process for altering the structure of the indium (III) compound into a chlorideinduced indium compound, in order to facilitate the vaporization of indium at a relatively low temperature. The experimental results indicated that 96.2 % of indium can be recovered from ITO, when the sample was heated at 973 K for 90 minutes. In addition, some thermodynamic calculations were also carried out in order to better understand the mechanism for chlorideinduced vaporization of indium.

Jan 1, 2011

Most of the world's zinc metal is produced via the roast- leach-electrowinning (RLE) process. The process is well established, but most of the sulphur in the sphalerite concentrates reports in the acid, which has to be stored and/or sold. There are significant incentives to develop a simpler process with much reduced acid generation. Ferric ion is a well known oxidant for most sulphides, in particular sphalerite, and it converts the sulphide to elemental sulphur. Based on stoichiometry, however, the amount of ferric ion needed to achieve acceptable zinc extractions is prohibitive for downstream zinc recovery from the leach solutions. The process suggested here makes use of less-than-stoichiometric ferric sulphate additions because the ferric ion is regenerated by sparging SO2/O2 mixtures. This regeneration can be effected in-situ in the leach vessel or outside the leach vessel. An example of the application of this new process is presented for a Canadian sphalerite concentrate assaying 60% Zn. The effects of temperature, ferric concentration and ferric ion regeneration are presented. Options to recover zinc from the leach solution are also briefly discussed.

Jan 1, 2000

By Manuel Pérez-Tello

A mathematical model to represent the expansion and fragmentation of copper matte particles oxidized under flash converting conditions is presented. The model assumes the particles to be initially nonporous, have a constant mass prior to fragmentation, and travel at a constant velocity throughout the reaction chamber. The model requires the specification of five parameters: the particle expansion rate, a fragmentation diameter factor, a fragmentation size distribution parameter, and the fractions of the finest and the coarsest particles in the feed that undergo fragmentation. The model predictions show good agreement with experimental data collected in a laboratory flash converting furnace over a wide range of experimental conditions. The evolution of the size distribution of the particles along the reactor length was computed, and the model parameters were correlated with the experimental operating variables. Model predictions indicate that particle residence time is an important factor in the generation of dust. The presence of two maxima in the particle density function may be attributed to turbulent conditions prevailing in the furnace, which cause particles to follow very different trajectories within the furnace even if they are injected at the same location.

Jan 1, 2006

By J. Antonio Barrera-Godinez, S. E. James, J. Sun

The solvent extraction separation of iron from a zinc sulfate medium using DEHPA was investigated. After loading, the ferric ions were reduced in the organic phase using metallic zinc. The ferrous ions produced could be easily stripped into a sulfate solution with pH values in the range of 1.4 to 2.0. The small, laboratory scale pilot system used in this study allowed for continuous cycling of the organic and strip aqueous solutions. It was possible to establish and evaluate a series of steady state conditions under selected operating paiameters. The effects of processing parameters such as solution chemistry, flow rates, zinc metal loading and pH on iron recovery and efficiency were also evaluated. Under proper conditions, it was possible to remove about 5 g/L iron from the organic phase in one stage and to produce a concentrated iron sulfate strip solution containing ferrous ion concentrations in the range of 90 to 130 g/L. Preliminary feasibility tests were also made on electrowinning metallic iron from the strip solutions and crystallizing ferrous sulfate as a means of making a marketable iron product.

Jan 1, 2000

By Sergio Demetrio

Based on the current reality of the copper smelters industry, besides the advances that have been and are expected for the next few years, the authors present a futurist vision of the processing of copper concentrates and copper smelters in the years 2000. Outlined new development strategies and ways of improvement in this business, including research, development and management of the works that today posses characteristics of a profitable operation, as well as the changes expected with respect to the entry of new actors and the creation of new products The authors finally bet for small or tailor-made smelters with ad hoc technology for their raw materials and few units to coordinate -devoted to specific concentrates using high technology and low manpower. Considering the in-situ hydrometallurgical route, as well as the pyrometallurgical route in works or conversion facilities that buy or process white metal and produce copper and other metals associated with this such as gold and silver, besides sulfuric acid, plants which should be strategically located in zones with high sulfuric acid price to make this a product which contributes to the profitability of the business.

Jan 1, 1999

By Christopher Solnordal

A mathematical model was developed to simulate the performance of the reaction shaft at BHP-Billiton?s Olympic Dam copper flash smelter. In order to have confidence in the predictions of the mathematical model, validation was performed by comparing and reconciling the predictions from the model with the results from a campaign of sampling and plant measurements. The model was based on the computational code CFX4.4 utilizing a combustion sub-model purpose-built by CSIRO. The combustion sub-model employed the concept of a composite particle which contained the three components of the solid charge: concentrate, flux and returned dust. Plant measurements were made and samples taken immediately below the burner and through a port halfway down the reaction shaft. Parameters measured included temperature, solid loading and SO2 concentration in the gas. Comparison of the measured and predicted values then showed that: predicted far field gas temperatures were within ±50C of measured values; predicted temperatures in the central plume were lower than measured, and, the predicted plume width was slightly smaller than measured. An optimum composite particle size of 19 m was identified for use in future modeling work at Olympic Dam.

Jan 1, 2006

By Florian Kongoli

The liquidus surface of multicomponent slags is an important parameter in various smelting and converting processes. It helps not only to optimize the slag, chemistry of current processes and their fluxing strategies, but also to determine the availability of new slags for more advanced technologies. In a series of our previous publications, the liquidus surface of some multicomponent iron oxide slags has been quantified at several constant oxygen potentials and the effect of the latter, ignored until that moment, was quantified along with the effect of some minor components. In this work, the liquidus surface of some iron oxide slags is quantified at constant CO2/CO ratios. This is a new convenient way for the quantitative description of the slag liquidus surface and the effect of several fluxes, especially in those processes such as slag solidification, where oxygen potential changes continuously. This type of diagram also describes more dynamically the effect of oxygen potential, clarifies the relation between CO2/CO ratio and oxygen potential in terms of the liquidus surface, which is not widely understood by metallurgist today, and reduces the gap between laboratory work and industrial experience.

Jan 1, 2002

By Reza Rahimi, M. Nili Ahmadabadi

"Because of high cost and shortage of primary resources of Ni-base superalloys, revert alloys can be used as a part of charging materials for production of superalloys ingots. The current study is based on recycling of IN738LC, a Ni-base superalloy, using 30% and 50% reverted alloy and balanced amount of virgin raw materials. Therefore, it has been attempted to cast an alloy with references to standard chemical composition and mechanical properties. After charging and casting in vacuum melting furnaces, chemical composition verification and non-destructive tests (i.e. Penetration and Radiography Tests), quality of samples were evaluated at elevated temperature by stress-rupture test. Results acquired from chemical composition and mechanical test indicate that cast ingots using 30% and 50% reverted alloy is reliable and consistent with the quality control requirements.IntroductionIn recent years, there have been many fluctuations in cost and availability of raw materials which are extremely determining in Ni-base superalloys production. Accessibility to the high purity metals such as Cobalt, Molybdenum, Tantalum, Niobium and etc. have been problematical during the past decades. Therefore, shortages of critical raw materials beside the economical considerations motivated the alloy suppliers and investigators to study and find alternate sources such as reclamation and recycling of scraps [1].There are a lot of reasons for the necessity of recycling; perhaps the most justifiable one is that consumers themselves produce scraps. For example, the weight of a finished superalloy product could be less than one-third of the cast alloy weight and in the case of complicated machined parts; this portion may reach to one-tenth [2]. High values of constituents, reduction of energy consumption and environmental concerns have all strengthened the obligation of recycling in Ni-base superalloys.Because of the high degree of risk in usage of improper materials for production of turbine blades, a delicately controlled program for recycling is needed. Depending on the type of scraps, this program can define the recycling procedure, required instruments, allowable percentage of scrap for usage and finally confidence level of the process."

Jan 1, 2012

By Noboru Masuko, Sachiko Ono

"The structure and composition of anodic films formed on aluminum in a borate solution have been investigated by using TEM and SIMS with respect to the effect of current density and electrolyte temperature. The film is composed of a boron-containing outer layer and a boron-free inner layer with disc-like crystals present at the interface. The thickness of the film formed at constant current density up to an identical voltage, decreases with increasing current density. The thickness increases remarkably with elevated temperature. The transport number of Al3+ estimated from the thickness ratio .of the cuter to the inner layers is 0.4 when the film is formed at the current density of 20 Am-2 at 60°C. It increases slightly with increasing current density and decreases significantly with increasing temperature. Content of boron in the outer layer increases 1.5 times when current density .increases 10 times. These changes in film structure and composition with electrolysis conditions must have a significant role in the determination of electric properties of anodic alumina films as a capacitor material.IntroductionThe growth of anodic alumina film in ·a neutral electrolyte proceeds at both film/electrolyte and film/substrate interfaces giving a duplex structure. The oxide layer formed at the former interface includes electrolyte anions while a-pure alumina layer is formed at the latter interface. The thickness ratios of each layer respectively represent transport numbers of Al3+ and 0 2 - (1). The film thickness and the incorporated anion content as well as transport numbers of both ions must affect the dielectric properties of the film as a capacitor material. However, the correlation between film structure and electrolytic conditions is not fully understood (2). For the further clarification of anodic film growth mechanism, more detailed characterization of anodic films in relation to electrolytic conditions is advantageous. In the present paper, therefore, the effect of current density and electrolyte temperature on the microstructure and composition of anodic barrier films formed in a neutral borate solution was studied. The films were characterized by direct observation using transmission electron microscopy (TEM) and depth profiles of constituent elements obtained by secondary ion mass spectroscopy (SIMS)."

Jan 1, 2000