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By Shulan Wang, Xuan Liu, Li Li

"Electrochemistry of Fe(III) in 69CaCl2-12CaF2-19KF and 81CaCl2-19KF (mole percentage, %) was investigated at 827 oC on molybdenum electrode by cyclic voltammetry, chronoamperometry and galvanostatic electrolysis using Fe2O3 as the Fe(III) source. The reduction of Fe(III) to Fe was conducted in one step and controlled by diffusion process. Fe(III) shown greater reduction rate and diffusion coefficient in molten 81CaCl2-19KF than in 69CaCl2- 12CaF2-19KF. Galvanostic electrolysis of Fe was performed in both molten salts with a cylindrical cathode rotating at 200 r/min and dendritic iron deposit was obtained.Keywords: iron; electrolysis; electrochemistry; molten saltIntroductionThe production of iron and steel causes huge emissions of CO2. Iron electrowinning in molten salts with dissolved Fe2O3 using an inert oxygen evolving anode is an alternative process to reduce or eliminate the formation of CO2. Research on novel process of producing metal has been reported recently [1-2] by using CaCl2 as the main electrolyte and dissolving CaO in CaCl2 due to the high solubility of CaO in the melt. This process has been used in preparing many active metals and alloys [3-14]. In the present work, the electrochemical behavior of iron in CaCl2-KF was studied and transport property of iron ion in the melt was discussed.ExperimentalCaCl2,CaF2 and KF (in analytical purity) were dried in air for 48 h. Mixed salts used in experiments were placed in a graphite crucible (??58 mm inner diameter). The graphite crucible together with the salts was heated at 473 K for 12 h in a furnace with flowing Ar (99.99%) before further heating. Temperature inside the furnace was measured by an S type thermocouple. Electrochemical measurements, such as cyclic voltammetry and chronocoulometry, were performed in a three electrode cell by EG&G PAR273A potentiostat/galvanostatand. Galvanostatic electrodepositon of iron was conducted in a two electrode cell. Molybdenum (??2 mm) and iron (??5 mm) were used as the working electrode (WE) and the reference electrode, respectively. A graphite crucible and a magnetite rod (??25 mm ) consisted of 100% magnetite and sintered at 950 oC in argon atmosphere for 2 h with electrical conductivity of 366 O-1m-1 at room temperature were used as the counter electrodes in the galvanostatic electrolysis experiment. Carbon (??10 mm) was used as the counter electrode in electrochemical measurement. The deposits were washed in distilled water bubbled with argon and dried in air before being characterized by X-ray diffraction (PW3040/60 diffractometer) and scanning electron microscope (SEM, SSX-550)."

Jan 1, 2014

By Matthew Tunnicliffe, Akram Alfantazi, Paul Nesbitt, Farzad Mohammadi

"Lead and its alloys are proper candidates for anodes in electrowinning processes mainly because they are insoluble in the leach solutions and relatively cheap. However, the annual cost of corrosion problems associated with these anodes is millions of dollars. In this study lead-silver and lead-calcium anodes were tested under typical nickel electrowinning conditions and the effect of chloride on the corrosion performance of the anode materials was investigated. Corrosion rates of the anodes were calculated using the discharge plateau (reduction of lead dioxide to lead sulfate) after galvanostatic experiments. It was found that lead calcium anodes have the highest corrosion rate both in the presence and absence of chloride. Surface morphology of the electrodes was studied using SEM and the corrosion products were characterized using XRD.IntroductionLead (Pb) is usually the preferred material for commercial anodes since it is insoluble in the leach solution and the costs are manageable. One advantage of using an insoluble material as an anode is the higher purity of the cathodic deposits and better quality of the end product. During nickel electrowinning, metallic nickel is deposited on the cathode while oxygen evolution reaction (OER) takes place on the anode. In practice, relatively high potentials are necessary for the reaction to proceed at the desired rate because of the high overpotential of OER on lead. Lead anodes get oxidized in typical electrowinning conditions and usually have two to three years of lifetime. Although the price of each anode is insignificant, the overall cost of corrosion of these anodes is considerable, which is due to the large number of anodes used in a plant, typically two to three thousand. Therefore, corrosion is a significant problem associated with lead anodes in commercial nickel electrowinning plants and industries show interest in addressing this problem. Corrosion of lead electrodes in acidic environments has been previously the subject of many research studies [I-7]. It has been reported that, during the anodic polarization of lead, several phases may be present on the surface, depending on the potential range that is being studied [8]. Lander showed that lead is oxidized at potentials higher than 0.252 YsHE with tetragonal lead monoxide being the main reaction product [9]. At 0.666 YsHE lead can transform to lead dioxide; however, it is not stable and transforms to lead sulfate and lead oxide. At potentials higher than 1.684 YsHE, lead dioxide is eventually a stable phase and forms a protective layer on the surface [I 0, 11]. Under conditions of a typical nickel electrowinning plant, usually a 200 A/m2 current density is passed through the electrodes."

Jan 1, 2012

By Toshiyuki Hashida, Victor M. Lopez-Hirata

"Small-punch tests and determination of fracture toughness JIC were conducted at 4 and 77 K on new cryogenic JN1, JJ1 and JK2 austenitic stainless steels, after isothermal aging. Equivalent fracture strain ?qf determined by measuring the reduction of thickness in the small-punch test specimen. A linear dependence of JIC on ?qf was found in these new materials. Regression analysis of experimental data produced the following linear relation JIC = 1304.1 ?qf + 8.09 [kJm-2]. An analysis of present work relation was pursued on the basis of material properties and evaluation method of he. Results showed that the slope value has a strong dependence on material yield strength and JIC evaluation method. This linear relation is useful for the evaluation of fracture toughness JIC, measuring the equivalent fracture strain ?qf by means of small-punch test. Thus it can be useful for assessing the degradation of fracture toughness in small areas such as, the heat-affected zone in welded components.IntroductionCryogenic structural materials for superconducting magnets of fusion nuclear reactor are required to possess a good combination of strength and toughness. The mechanical properties are required beyond the capability of conventional austenitic stainless steels [1]. New cryogenic JN1, JJ1 and JK2 austenitic stainless steels were developed by the Japan Atomic Energy Research Institute (JAERI) [1]. The structure of superconducting magnets is constructed by welding of 200 = thick plates of these steels, which are solution treated at high temperatures and then water-quenched to avoid intergranular precipitation. However, the welding process involves heating and cooling [2], which cause microstructural changes in both base metal and weld. In this heterogeneous microstructure, it is important to estimate the fracture toughness of these materials at cryogenic temperatures. Therefore, it is necessary to evaluate the effect of aging process on the fracture toughness behavior of these new steels. To determine the cryogenic fracture toughness, the elastic-plastic JIC value has been co=only used [2]; however, the specimen size is much larger than heat-affected zones in welded components. Small-punch (SP) testing method, employing miniature specimens, has permitted to evaluate the fracture toughness behavior at different temperatures in different nuclear reactor materials [3,4]. Mao et al. [5,6] and Misawa et al. [7] found a linear relation between JIC value and equivalent fracture strain ?qf, determined by SP method in non-ferrous alloys and ferritic steels at room temperature and austenitic stainless steels at 4 and 77 K, respectively. So that, this kind of correlation would be very useful to assess the fracture toughness JICe values by means of SP test in small zones of welded components."

Jan 1, 2012

By M. R. Baren

Unpublished results obtained by Baren on thermodynamic properties of sulfur in liquid Fe. Co. Ni. Fe-Co. Fe-Ni. and Co-Ni are reevaluated. correlated. and interpreted on the basis of recent developments in thermodynamics of alloys:. Existing reliable data are reviewed and compared with the? present results. Sulfur obeys Henry's law up to 0.04 mol fraction. and in this range the standard Gibbs energy of solution of sulfur is expressed as a linear function of temperature for each pure metal. The activity coefficient of sulfur in each binary metal solvent 1s correlated with the composition of alloy.

Jan 1, 1983

By Thomas R. Wildeman

Experimental methods for studying vapors over solid minerals are reviewed and an especially developed method using atomic absorption is described. The method is used to study vapor pressures over Te. Ag, Au, Ag2Te, and AuTe2 from 250°C through 10S0oe. Vapor pressures observed and, concurrently. sintering properties are significantly altered by the form of the solid. The vapor pressures of the tellurium compounds reveal complex processes occurring on the surfaces of the solids. The data given also point out a method of recovering precious metals from their telluride minerals w

Jan 1, 1987

By A. D. Zunkel

The zinc in electric arc furnace dust (EAFD) arises from the fuming and oxidation of the zinc present, mainly as galvanizing, in automotive scrap. The dust is collected from the electric furnace offgases in bag filters and is classified by the EPA as a hazardous waste (K061). As more zinc is used in galvanized sheet on automobiles and more automobile scrap is recycled via the EAF, the more zinc will be available for recovery and recycling. EAFD will become a more prevalent and important source of zinc compared to the traditional zinc sulfide concentrates ifit can be cost effectively processed.

Jan 1, 1995

By S. Seetharaman

The present paper presents. the concept of micro-models and illustrates the application of the same in the simulations metallurgical processes. Development of micromodels requires access to accurate thermodynamic, thermophysicaland kinetic information for the relevant systems with suitable models to extrapolate the data as functions of temperature and composition. Experimental measurements and modelling of the thermodynamic properties, sulphide capacities and viscosities of oxide melts carried out in the department are presented. The incorporation of these models in process models, with special reference to ladle refining of steel is illustrated. Typical example of micro-modelling of solid-gas reactions is also presented.

Jan 1, 1999

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 K. Dzieciol

The paper presents a study about three image correlation methods ?common cross-correlation, mutual information and phase-correlation ? applied to characterize microstructures reconstructed with X-ray tomography. It is shown that phase correlation is not only the fastest, but also the most sensitive method for detection of similar microstructure features, cavities in the present case. A new image correlation indicator is proposed, which takes into account both the phase shift and the amplitude of similar features in compared images. Some preprocessing aspects related to the tomographic reconstruction and filtering out of characteristic noise are also discussed.

Jan 1, 2009

By James B. Pfeiffer

TETRA Technologies, Inc., has applied its HDS? metals precipitation system to control a mine drainage problem. The effluent from the mine contains primarily zinc, manganese and iron, plus varying small amounts of cadmium, copper and lead. The flow from the mine averages 350 gpm, and varies considerably depending on season and weather conditions. The plant was designed to treat 1000 gpm of the water and generate a dense sludge suitable for recycling. The HDS? system contains a number of reactors, followed by post filtration and meets stringent metals discharge criteria as specified by New Source Performance Standards.

Jan 1, 1994

By Michael K. Rhodes

A 120 tonne per day BacTech bacterial oxidation plant treating refractory gold concentrates for Gold Mines of Australia's Youanmi project in Western Australia commenced operation September 1994. This was the first commercial application of the BacTech process. A pilot plant trial on concentrates produced from Youanmi ore was carried out at BacTech's laboratory in Perth. Results and measurements from this trial were used by Signet Engineering Pty Ltd to design the commercial plant. This paper cover the results obtained from the piloting, their implementation in the plant design and the initial commissioning of the full scale plant.

Jan 1, 1995

By I. B. Scorzelli

The aim of this paper is to make a detailed mineralogical characterization of a typical brazilian xenotime and zircon from the Pitinga Mine using SEMIEDS techniques, On the other hand, superficial pretreatments with HCI, HN03 and HF were done to evaluate the modifications on surface compositions and the morphology of the particles for flotation purposes, The studies showed that both xenotime and zircon present very small inclusions of thorite; zircon is strongly metamictizated given rise to malacon. The HF pretreatment deeply affected the morphology of the particles as well as the surface properties in relation to flotation.

Jan 1, 1996

By Thomas M. Harris

To avoid the escalating cost of disposal of metals-containing wastewater and residues, new wastewater treatments will focus on the recovery of the metals. A combination of ion exchange and electrowinning can produce water suitable for discharge and relatively pure metals. The use of a chelating resin can enhance the selectivity of both the removal process and the elution of metals from the resin. A new, simple method of preparing a variety of chelating resins is being developed. The materials produced by this method exhibit interesting, as well as potentially useful, elution behavior. The performance of one test resin is described.

Jan 1, 1992

By F. Chabchoub

A mathematical model has been developed to study the influence of process variables on the horizontal Ohno continuous casting process. The model simulates the heat transfer and fluid flow in a wide plate ingot of pure tin. A two dimensional numerical analysis based on a control-volume finite difference approach, the Semi-Implicit Method for Pressure-Linked Equations algorithm (SIMPLER), and an Enthalpy Transforming Model was used. The shape and position of the solid-liquid interface were calculated at different casting speeds, ingot thicknesses, and cooling device characteristics, as well as various mould temperatures. Results of the mathematical model were compared with

Jan 1, 1992

By Reinhard F. Dobner

After a short introduction about the HK's secondary smelter process and explanations concerning the anodes produced the regulation and buffering of bleed will be described and the principles of technology for processing of bleed will be presented. Modernization aspects, especially installation equipment, and the different types of evaporators used will be described in detail. Besides, experience made with acid-resistant materials - stainless steel, enamel, plastics - will be reported. Environmental aspects such as water and air pollution will be outlined briefly and in conclusion the quality of products obtained as well as quality control will be presented.

Jan 1, 1997

By Bora Derin

The synthesis of titanium diboride (TiB2) by carbothermal reductions of TiO2 and B2O3 was investigated. For this aim, TiO2, B2O3 and carbon black powders were dried, weighed out and mixed in stoichiometric molar proportions (TiO2:B2O3:C = 1:1:5). The experiments were carried out in a graphite resistance furnace in argon media using different range of temperature (1400- 1700 °C) and time (0 and 15 min). The phase analyses observation of the products were examined by using XRD.

Jan 1, 2008

By Giuseppe Bonifazi

Minerographic and petrochemical research was carried out on crude ore samples from the complex polymetallic Zn-Cu-Pb sulfide ores of , Sotiel in Huelva province west of Seville, Spain. A computerized image analysis system was used to define the structural and textural characteristics of the ore to obtain information on the degree of liberation of the different minerals (i.e. pyrite, sphalerite, galena, chalcopyrite). Techniques of digital multispectral image processing of reflected light microscopy images were used. Particular structures were identified by means of mineral associations and numerically quantified to obtain useful information for designing beneficiation processes.

Jan 1, 1991

By T. Yoshida

The Ni-MH (nickel metal hydride) rechargeable battery was developed several years ago. Its higher electrochemical capacity and greater safety compared with the Ni-Cd rechargeable battery have resulted in very rapid Increase in its production. The Ni-MH rechargeable battery consists of Ni. Co and rare earth metals, so that recycling is important to recover these valuable mineral resources. In this study. a basic recycling process for used Ni-MH rechargeable batteries has been developed, in which the Ni. Co and rare earth elements are recovered through a combination of mechanical processing and hydrometallurglcal processing.

Jan 1, 1995

By Xiao-hui Fan, Xu-ling Chen, Zhi-yuan Yu1, Guanghui Li, Min Gan, Yun-song Huang, Tao Jiang

Compared with the traditional de-NOx processes by cleaning the waste gas, a new approach for reducing the formation of NOx during sintering process is proposed. Since more than 90vol% of NOx comes from the fuel combustion, the influence of sintering coke breeze pretreated by CO(NH2)2 additive on the NOx emission is researched. As adding CO(NH2)2, the reduction agents (NHi) are generated during the pyrolysis of CO(NH2)2, which reinforce the NOx reduction, And the appropriate content of CO(NH2)2 is 1.0 mass% of coke breeze.

Jan 1, 2015

By Gunther Klamp

Disposal of arsenic compounds from washing acid in metallurgical plants is becoming a severe problem when using lime neutralization. A further problem is the disposal of relatively large quantities of gypsum which is produced during this neutralization step and which Is also conta-minated with other toxic metal compounds. The Sachtleben-Lurgi process removes arsenic and other metals from washing acid in the form of insoluble sulphides. The purified acid contains less than 0.5 ppm of arsenic and can be used for standard sulphuric acid applications. The process Is demonstrated commercially at Sachtleben's acid plant since more than five years.

Jan 1, 1992