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By Fiseha Tesfaye, Pekka Taskinen

"A thermodynamic study of the equilibrium phase assemblage AgBi3S5-Bi2S3-S was made by an EMF-technique, using the RbAg4l5 solid electrolyte. The ternary phase was synthesized from the pure Ag2S and Bi2S3 in an evacuated silica ampoule and grinded into powder and mixed with appropriate compositions of B12S3 and S, in a series of experiments, for pressing in to pellets. The pellets were assembled to form the galvanic cells Pt (-) | Ag ] RbAg4ls | AgBi3S5+ Bi2S3 + S + (C) I Pt (+). The EMF-measurements were made in the temperature range 299 - 460 K.In this paper, thermodynamic functions of the ternary phase AgBi3S5 (pavonite) have been determined. The agreement between the obtained results and the literature values were established.IntroductionThe complex group of ore minerals constitutes from trace amounts to a major proportions of sulfosalts. Although the sulfosalts rarely form massive ore bodies, they are commonly associated with rich sulfide ore minerals for the base and precious metals and widely distributed in a metal poor sulfide minerals [1]. For instance, Ag-bearing sulfosalts are encountered in ore minerals for the production of the base metals and are common sources of silver. Nevertheless, thermodynamic properties of the sulfosalts are poorly known.Reliable thermochemical data are essential for quantitative modeling of the chemical behavior of the sulfosalts in equilibrium with sulfides, which in turn would promote the optimization of complex minerals treatment and extractive metallurgy of the valuable metals."

Jan 1, 2012

By Jenq-Gong Duh, Jyh-Wei Lee

"Hard chromizing process is a method for developing a surface modified coating providing wear, corrosion resistance and high temperature surface protection. Two carbon steels with 0.45 wt% and 0.95 wt% carbon contents, respectively, were chromized with pack cementation process at 950'C for 4 and 9 hours, respectively. The phase transformation and microstructure phenomena of chromized coating layer and matrix of two steels were studied with X-ray diffractometer and electron probe microanalyzer. (Cr,Fe)23C6 and (Cr,Fe)7C3 carbides and (Cr,Fe)2N1-x nitride phases were observed on the chromized surfaces. The thickness of chromized layers obeyed the parabolic rate law. The mechanism and diffusional kinetics of the chromizing process were proposed. The diffusivity of chromium in the (Cr,Fe)7C3 carbide phase was calculated using the moving boundary method.IntroductionChromizing process is one of the surface treatment technologies that can produce a chromium contained surface layer with sufficient corrosion and wear resistance on the steel matrix [1-7]. The relatively low cost and no ""line-of-sight"" restrictions are main advantages of chromizing. Adequate bonding strength of these coatings to the substrate was reported [7]. Chromizing process can be classified into soft chromizing and hard chromizing [2]. Soft chromizing is applied to steels containing less than 0.1wt% carbon through which chromium will be diffused. High temperature oxidation resistance improvement is the main purpose of soft chromizing process. On the contrary, the hard chromizing can be applied to steel containing more than 0.3wt% carbon, and very hard chromium nitride and carbide layers will be formed on the surface, which are very resistant to wear, corrosion and temperature [5-7]. In the previous studies on the Fe-Mn-Al-Cr alloy [5,7] and carbon steels [6], the thickness (X) of chromizing layers was analyzed and found the parabolic rate Jaw prevailed:"

Jan 1, 2004

By E. Ilgar

"Deposition studies were conducted in acid copper electrolyte to determine the influence of chloride ions on cathode morphology. A statistically designed screening test was carried out in the absence and presence of 20 ppm CI- using a three factor, two level factorial design, in an electrolyte containing 36 gl'! Cu2+ and 150 gl-! H2S04, The independent variables evaluated were agitation; current density and temperature and their influence on surface roughness was determined. The copper deposited at current densities where activation was the primary control mechanism appeared similar in morphology whether stirring was used or not. The addition of 20 ppm CI- to the electrolyte gave rougher deposits under the same conditions. In the mixed control regions, considerably rougher, dendritic deposits were obtained when CI- was present. Agitation was effective in reducing the copper surface roughness both in the apparent activation and mixed control regions in the presence ofCI-. The results of this study showed that 20 ppm Cl- polarized the copper deposition at low overpotentials but caused depolarization at higher overpotentials.IntroductionChloride ion is inherently present in copper electrolyte, either as an additive or from other sources such as make up water. The behavior of the chloride ion is well documented in electrorefining operations, but its role in copper winning is less obvious. However in both cases there is evidence that cathode growth and solution chemistry are strongly influenced by its presence. The mechanism and electrochemical action of the Cl"" have been shown to be very complex, therefore a better understanding of its influence on electrocrystallization is essential for improved cathode deposit growth control. It was proposed that Cl"" polarizes the copper deposition reaction at low concentrations due to CuCI formation but depolarization occurs at higher concentrations due to the formation of a soluble CuCI2"" complex [1,2]. Franklin [3] reviewed the mechanism of additives in the electrodeposition process and proposed that the Cl"" complexed with copper, adsorbed on the cathode as an induced anion leading to an increase in the reduction rate. At cathodic overpotentials less than 100 mY, lppm NaCl had a polarizing effect, i.e. an increase in impedance of the charge transfer step. At higher Cl"" concentrations up to 100 ppm, depolarization occurred as evidenced by a decrease in impedance, which was attributed to soluble cuprous complexes [4]."

Jan 1, 1997

By Chang Wei, Zhigan Deng, Jiqiang Liao, Minting Li, Hongsheng Xu, Yan Song, Cunxiong Li, Xingbin Li

"Abstract: Direct ?otation of oxidized zinc-lead ore is characterized by recovery of zinc and lead only around 55% and 50%, respectively. Mineralogical analysis shows that the sample used in the present study is a carbonate hosted zinc-lead ore, with a zinc and lead carbonate content that accounts for 80.14% and 75.63% of the total minerals, respectively. The carbonate hosted zinc-lead ore was hydrothermally sulfidized with elemental sufur and the experimental data indicated that under the conditions employed up to 75% zinc and 82% lead sulfidation extent were achieved. As a result of pre-sulfidation followed by flotation, the recoveries of zinc and lead into flotation concentrate were over 90%. A flotation concentrate was obtained with 52% Zn and 37% Pb from the materials which was treated by sulfidation.IntroductionSulfide ores are the primary source of zinc and lead, and they are becoming depleted; thus, metallurgical investigators are interested in using abundant oxidized zinc-lead ore reserves. The high-grade zinc-lead oxidized ore, which normally has a zinc content higher than 15%, can be disposed of by acid leaching and electrolysis. However, the low-grade ore, which has a zinc content lower than 10%, is difficult to smelt with pyrometallurgy and hydrometallurgy, and the processes are very complicated and expensive in terms of production flow and energy consumption. Therefore, making the low-grade oxidized zinc-lead ore more beneficial has become more important in recent years. Flotation is the most common process, and the primary method of recovering zinc and lead from sulfide or oxide minerals. It is well known that there is a difference between sulfurized and oxidized minerals regarding their separation by flotation. Flotation of zinc and lead oxidized minerals is extremely complex because of the similarities in the physicochemical and surface chemistry of the constituent minerals. There are no known direct-acting collectors capable of producing single metal concentrates [1-3]."

Jan 1, 2012

By Susumu Okabe

Top blow injection has been applied to continuous copper smelting and converting by Mitsubishi Materials Corporation since 1974. In this process, injected feeds are captured by and dispersed in the molten bath immediately and effectively, and the reaction is enhanced by the agitation of the bath. The continuous motion of the molten bath, however, may cause severe damage of furnace lining materials, if the injection is not controlled and the furnace is not designed properly. In order to suppress refractory wear, especially at the bath line, surface wave of the molten bath should be moderated. A cold model study was carried out with water bath in a cylindrical vessel and the physical model was derived which correlates the oscillation of gas jet impingement on the bath surface and the surface wave. It was found that a half of the proper frequency of the gas jet impingement coincides the proper frequency of the surface wave.

Jan 1, 1998

By P. Hajiani

Rare earth elements (REEs) are critical materials in many leading-edge technology products. However, REE separation outside China has remained a challenge in addressing environmental concerns of current production. The author has worked on a technique employing the emphasised variability in the electrophoretic mobility (μi) of REE for the purpose of REE separation. In continuation of the results presented in IMPC 2016 [1], this contribution summarizes the progress achieved in 2016 and 2017. The major goal was to increase the REEs concentration by a factor of 1000 and to attenuate the consequent drawbacks, specifically joule heating effect. Amphiprotic hydroxylic solvent was selected to replace water, which has a major impact on the complexation mechanism and buffer requirement. Non-aqueous media result in a significant drop in the specific molar conductivity of the electrolyte, whilst μi reduces several times only. Moreover, a quasi-steady state electrophoretic separation in conjunction with temperature gradient focusing is adapted to improve scalability.

By Zhijing Zhang

Long-term thermal stability of ionic liquids is essential for reliable performance of ionic liquids in any engineering applications. TGA studies were carried out on a series of ionic liquids with different cations and anions such as 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-hexyl-3-methylimidazolium chloride ([C6mim]Cl), 1-hexyl-3¬methylimidazolium tetrafluoborate ([C6mim]BF4), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim]PF6), 1-octyl-3-methylimidazolium hexafluorophosphate ([Csmim]PF6), and 1-butyl-3-methylimidazolium bis(trifluromethanesulflonyl)imide ([C4mim][Tf2N]). The short-term thermal stability of ionic liquids was evaluated by measuring the onset temperature of decomposition of ionic liquids, and the long-term thermal stability of ionic liquids was also evaluated by weight loss of ionic liquids over a long period of time at various temperatures. The experimental results showed that the long-term thermal stability of ionic liquids decreased with increasing temperature and was significantly lower than the onset temperature of decomposition of ionic liquids.

Jan 1, 2002

By M. K. Patel, K. A. Pericleous, M. Molaei

"The future trading of carbon credits and increased financial cost necessitates substantial cuts in incidental C02 emissions in the production of metals (iron, steel, aluminum, zinc, lead). Although greener methods of production are being developed, in the short term the use of point-source C02 extraction using existing technology remains attractive. Accelerated natural carbonation, in a fluidized bed is a feasible technological route investigated in this research. CFD modelling has been used to study the efficiency of C02 capture in a fluidized bed reactor containing a CaO solid sorbent. A Lagrangian/Eulerian scheme describes describe CaO particle trajectories and exchange of mass, momentum and energy with the carrier gas, with a typical off-gas composition. Different reactor geometries are considered (with uniform, stepped and gradually expanding cross-section), to maximize conversion for a given particle loading and size distribution (100-200 microns). Removal efficiencies of up to 80% are demonstrated, making this a viable process.IntroductionBased on Intergovernmental Panel on Climate Change (IPCC) reports, the major cause of climate change and global warming is due to a high level of C02 concentration in the atmosphere resulting from fossil fuel combustion, particularly in coal-fired power plants [1]. Carbon capture and storage is therefore the most important action proposed to reduce C02 from combustion flue gases. In this process, carbon dioxide is captured and may then be regenerated as pure C02 and conducted to a permanent storage, or simply stored as a solid carbonate [2]. Capture and storage of C02 has an economic penalty and the main cost of this penalty is associated with the capture plant. Capturing C02 with a lime-based solid sorbent (CaO) is a very promising technique, due to the low cost and the wide availability of the reactant. In this process, the CaO reacts with C02 based on the following reaction in a reactor called a Carbonator:"

Jan 1, 2012

By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By Ho-Jung Shin

The influence of cooling rate from 1873 to 1473 K on the size and morphology of austenite grains was studied using a Fe-O.I5 % C-I.5 % Mn alloy. The experiments were carried out at three different cooling rates of O.33KJsec, O.67KJsec and air-cooling. The austenite grain showed an isotropy at 0.33KJsec but maximized anisotropy at O.67KJsec and become much less. anisotropic. In order to account for these phenomena, a model was developed for estimating the size and morphology of austenite grains as a function of cooling rate. The driving force for the )( phase formation from 0 phase is caused by undercooling degree due to cooling rate and energy barrier is restricted to the misfit strain energy which is caused by mismatch between )( phase and 0 phase. The )( phase from 0 phase could be formed on not random orientation index systems but specific orientation systems depending on cooling rate.

Jan 1, 2001

By Tatiana Pereira Moreno, Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"Nowadays, End-of-Life (EoL) Liquid Crystal Displays (LCDs) are traditionally disposed in landfills. The increasing access to LCD technology over the last years by Brazilian consumers has intensified LCD' s disposal as an environmental and economic issue. This study aims to characterize used LCDs to identify the main components for recycling. Characterization was performed through scrap disassembly and its components were identified, separated, and weighted. LCDs were disassembled and the following divisions were applied: screen, metal frame, polymeric frame, polymeric sheets and electronic part. Some techniques were used to determine the concentration of Indium in the LCD, the glass/plastic ratio and the different kinds of polymers that compose the screen. The techniques used for characterization included inductively coupled plasma optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). This method, when applied to a wide range of LCDs, can allow the development or improvement of an EoL management of LCD.IntroductionWaste Electrical Electronic Equipments (WEEEs) are waste from discarded equipment, such as computers, monitors and cellphones [1]. Over the past years, treatment of WEEE has been emphasized. It occurs due to the technology's advancement that leads to an even larger increase of WEEES [2].Among WEEEs, there are the liquid crystal displays (LCD). LCD technology is applied in cell phones, tablets, computers and monitors. Nowadays, it's the most well known technology when it refers to monitors, due to its advantages over the Cathode Ray Tube (CRT) technology. Some of them are energy saving, smaller size and no radiation emission [3].This feature in the LCD's global market along with the speed at which electronic equipment becomes obsolete affects society economically and ambiently.This issue becomes even more serious when considering the final destination of the liquid crystal displays. LCDs are lead to landfills as other WEEEs. Besides the different materials long degradation time, the environment is damaged by the disposal of the potentially reusable and hazardous materials [ 4]."

Jan 1, 2014

By Huanyu Zhang, Zhancheng Guo, Liqiang Fan, Huiqing Tang

"In this study, a simple process has been developed for zinc oxide recovery from RHF (rotary hearth furnace) secondary dust. The results have shown that a high dissolution efficiency of soluble zinc was achieved with water leach at ambient temperature with a liquid/solid ratio of 10/1 in 30min while 20% of the dust was left as solid residue. The rate of dissolution increased slowly after the dissolution efficiency reached 90%. The leaching process was found to be controlled by external diffusion. After separation, zinc was precipitated in leached liquor by introducing a precipitation agent of potassium hydroxide. The resulting solid was purified and dried at 393K. Zinc powder in the form of ZnO with purity of 98.5 mass% was obtained with an average size of 12.4µm.IntroductionThe RHF (rotary hearth furnace) direct reduction process is widely used in many iron and steel enterprises to deal with various metallurgical dusts [l]. The basic principle of this process is that first various metallurgical dusts (BF dust, EAF dust and so on) are pelletized with a coal reductant, and they are then subjected to a fast reduction using RHF after being dried. Highly metallic pellets are produced and at the same time, nonferrous elements such as Zn, Pb, K and Na are evaporated into the RHF flu gas as secondary dust. Zinc is listed by the Enviromnental Protection Agency as one of the 129 priority pollutants. Therefore, recovering zinc from the industrial wastes is important in terms of enviromnental protection [2-3]. On the other hand, nowadays China is in shortage of zinc resource and the annual output from metal recycle only accounts for some 13% of the total zinc resource. There are many ways proposed to recover zinc from various wastes [ 4-7]. The aim of this paper is to recover zinc oxide from RHF secondary dust by a method with water leach followed by caustic precipitation. This work investigated the influence of the leaching temperature and leaching liquid/solid ratio on the zinc recovery efficiency. The process consisted of three stages: (1) leaching with water; (2) liquor/residue separation; and (3) zinc precipitation in caustic milieu."

Jan 1, 2014

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 F. Leuzzi

Asbestos is a natural mineral fibre which has been known and utilized commercially for about a century. From the forties, it was employed on an ever-increasing scale throughout the mechanical engineering, building, paper-making and plastics sectors, to name but a few. There are essentially five minerals which provide fibres for industrial applications, namely, the chrysotile variety of serpentine and the amphiboles such as riebeckite, anthophyllite, cummingtonite-grunerite (amosite) and tremolite. About a fifth of the world's asbestos output was once taken by Europe for the manufacture of asbestos-cement products, reinforced plastics, paper and cardboard, panels, soft insulation and spray-on powders. However, in the sixties and seventies the hypothesis regarding the pathogenic nature of asbestos fibres started to gain ground. Moreover, between the sixties and eighties the EU issued a series of regulations designed to bring about a steady decrease in asbestos consumption. This line of action has culminated in recent years in a whole set of directives banning the use of asbestos in all products. This created a major problem, namely, how to clean-up the several million tons of various types of asbestos products in various states of conservation existing in Western Europe. CORDIAM (Pat. RM95 A 000269 and Pat. RM96 A 000782 in the name of ECOTEC S.r.1.) is one of the thermal inertization techniques recently proposed for this purpose. The process provides for the low-temperature ceramization of the toxic-harmful material. Of course, with such a great variety of waste materials and the volumes to be treated, as well as the need to ensure the correct dimensional design of the thermal sections of the treatment plant, it is necessary to know as much as possible about the thermal behaviour of the wastes concerned. This paper details the steps taken firstly to ascertain the thermal behaviour of such materials as may be encountered in day-to-day practice and secondly to examine the influence of the main process parameters on the preliminary design of gas- or fuel-oil-fired rotary kilns of the kind used for waste treatment.

Jan 1, 1999

Today’s world relies upon advanced green technologies that are made of critical elements with unique properties. Examples include rare earth elements (REEs) that are critical in the manufacturing of wind turbines and electric/hybrid vehicle batteries, key components of a greener future that face supply uncertainty and near zero recycling. To tackle their supply challenges, activities have begun for urban mining from waste electrical and electronic equipment (WEEE) that contain considerable amount of REEs, but their current level of recycling is less than 1%. Current recycling practices use either pyrometallurgy, which is energy intensive, or hydrometallurgy that utilizes large volumes of acids and solvents and generates large volumes of hazardous waste. In this study, we developed a novel and sustainable process to recycle REEs from WEEE, NiMH batteries in particular. The developed process relies on supercritical fluid extraction (SCFE) utilizing CO2 as the solvent, which is abundant, safe, cost effective, and inert. The effect of seven operating parameters, namely temperature, pressure, residence time, sample to chelating agent ratio, agitation rate, complex formulation, and methanol addition on REE extraction efficiency was investigated, and optimum operating conditions were determined. This work is the first to utilize a very efficient and safe process that runs at low temperature to extract metals from postconsumer products with minimum hazardous waste generation, while offering about 90% leaching efficiency for REEs. We expect our process to find widespread applicability in urban mining of REEs using green chemistry.

By P. M. Tyroler

At INCO's Copper Cliff Nickel Refinery, nickel is extracted by using the INCO Pressure Carbonyl (IPC) process. The resulting IPC residue containing copper, nickel, cobalt, iron, sulphur, precious metals, selenium and tellurium is further processed at a hydrometallurgical plant. This plant treats approximately fifty metric tons per day of IPC residue. The components of the feed are separated in a number of steps and a precious metals concentrate, nickel-cobalt carbonate, a selenium-tellurium intermediate and copper cathodes are produced. An iron-arsenic waste stream is also produced and discarded to tailings. The hydrometallurgical processes include pres- sure leaching, cementation, precipitation, thickening, filtration and electrowinning. This paper describes in detail the individual steps of the flowsheet.

Jan 1, 1988

By Sacha Neven

Submerged lance technologies combine high intensity processing characterized by rapid mixing and reaction rates using a simple reactor design. The Isasmelt technology uses a central submerged lance to inject oxygen-enriched air and fuel into a bath thus creating large gas bubbles and intensive turbulence and splash. The lance is equipped with swirlers to increase gas velocity and heat transfer. This enables the formation of a frozen slag layer on the lance which protects it from the aggressive environment. Water models as well as high temperature reactors were used to validate the Davidson-Schiiler model on bubbling. Frequencies and pressure amplitudes were measured in a wide range of gas flow rates: from m3/sec using a water model to more than 30 m3/sec in an industrial process. Agreement with the model was satisfactory. The experiments however also clearly showed that cross-flow and bubble wake induce slightly higher frequencies. No influence of the use of swirlers on the bubbling frequency was observed in the water models.

Jan 1, 2002

By Shanlu Yang

In this study, laser-GTAW hybrid welding was used to the lap joint of galvanized dual-phase (DP) 980 steel in a gap-free configuration. The effects of welding parameters such as the laser power, the distance between the laser beam and the electrode torch, the arc current on the quality of hybrid welds were fully studied. The reason for the formation of different weld defects arises from the development of the highly-pressurized zinc vapor at the interface of two metal sheets. Experimental results demonstrated that the elongated molten pool introduced by the GTAW can suppress the formation of spatters to some extent. However, the hybrid laser-arc welding process still suffers from a large amount of spatters that degrade the weld quality. Furthermore, it was found that the weld quality was enhanced with the increase in the laser beam-arc distance and welding current.

Jan 1, 2009

By K. Fagerlund

In this work, the rate of dissolution, melting behaviour and phase separation of silica flux with molten slag and matte were investigated. Mutual dissolution between high-grade matte and silica was chemically determined. Silica dissolution rates ,in various iron silicate slags was determined using the rotating rod method. The reaction and separation phenomena of slightly oxidised chalcopyrite samples and cuprous sulphide-magnetite mixtures with silica sand were examined all about 1350°C. The samples were water quenched, and polished specimens were studied and analysed using a light optical microscope ,and a scanning electron microscope with energy dispersive spectrometer. The silica dissolution rate in slag was found to increase with decreasing silica content and increasing ferric iron content. The reaction rate of silica sand' with matte was found to increase with increasing oxidation degree and magnetite content of matte:

Jan 1, 1998

By Harrison Hodge

In the Bayer process for alumina production, between 2–35% Al2O3 is lost with bauxite residue due primarily to incomplete dissolution of aluminiumbearing minerals during caustic leaching or the precipitation of sodium alumino-silicate solids. The recovery of sodium and aluminium from the residue, and particularly from the contained sodium alumino-silicates, is becoming an increasingly critical issue from both an environmental and economic standpoint. Lime-soda residue sintering followed by selective leaching has been proposed as a method to recover sodium and alumina. The factors influencing the sintering mechanisms and kinetics, and the subsequent leaching have not been well described to date. In this study, the physical and chemical changes taking place during isothermal sintering of bauxite residue in air, particularly at short reaction times are investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD). The impacts of these changes on the recovery of valuable materials are reported.