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By Irsan Chandra

It is generally recognized that the gold thiosulfate leaching system requires the presence of copper and ammonia in order for acceptable leaching kinetics to be observed. However, the presence of copper and ammonia complicate the chemistry of the system as thiosulfate is rapidly oxidized by oxygen under these conditions. In addition, the environmental impact of ammonia would need to be considered before the adoption of this system. This paper describes fundamental studies into the thiosulfate oxygen system. The two reagents for this system are thiosulfate and oxygen, and leaching is carried out at pH < 7. It will be shown using electrochemical techniques that both the reduction of oxygen and the oxidation of gold-to-gold thiosulfate are hindered. Thus, if leaching is to work under these conditions, then both half reactions need to be improved. The use of additives, such as thiourea and lead have been shown to dramatically improve the oxidation of gold and the reduction of oxygen respectively. The leaching of gold in the presence of such additives is discussed.

Jan 1, 2003

By C. H. Quan

Solvent extraction tests were carried out on a rare earth chloride solution derived from monazite processing to determine the effect of extractant and diluent on the distribution coefficients between organic and aqueous phases, and the separation factor between rare earths. The extractants were 20% by volume di-2-ethyl-hexyl phosphoric acid (DZEHPA) or 2-ethyl-hexyl phosphonic acid (Ionquest® 801). Four Shellsol diluents were tested ranging from nil to 100% aromatic content. D2EHPA gave the highest rare earth extraction for a given pH but was less selective than Ionquest. The geometric mean separation factor between adjacent rare earths varied from 2.41-2.56 for D2EHPA to 2.62-3.01 for Ionquest. The nil-aromatic diluents (Shellsol 2037 and 2358) gave better separation factors in Ionquest but, in D2EHPA, were slightly inferior to the 100% aromatic diluent Shellsol AB. Yttrium behaved as a pseudo-heavy rare earth with a distribution coefficient lying between Ho and Er, as expected from its ionic radius.

Jan 1, 1992

By E. Açma

Sivas-Divrigi flotation plant has a capacity of 90,000 tpy. Beneficiation of the tailings of iron ore magnetic separator seems to be attractive, because of its Cu, Co, and Ni contents. In the experimental work, sulfidic flotation concentrate is produced from these tailings. A roasting-leaching-H2S precipitation procedure is used to treat this concentrate, containing 0.55% Cu, 0.51% Co, 0.74% Ni, and 0.027% Zn. Sulfatizing roasting is carried out in a rotary furnace at 690°C. Roasted product is leached with 10 gpl HzSOl at 70°C and 30% pulp density. For the precipitation of desired metal, H2S is bubbled through the concentrated solution of repeated leaching, under controlled temperature and pH. Final metal recoveries of 91% Cu, 91% Co, and 50% Ni, and 92% Zn are attained. Roasting gases with their 13% SO2 content are suitable for H2SO4 production and the leach residues can be integrated with the iron ore processing plant as they contain 57.4% Fe and very low non-ferrous metals.

Jan 1, 1993

By M. Olper, M. Maccagni, C. J. N. Buisman, C. E. Schultz

The key point of the CX-EWS process is the conversion of lead compounds, contained in the active mass of spent batteries, into lead sulphide. The obtained lead sulphide is leached with ferric fluoborate electrolyte to dissolve lead and oxidize the sulphur from sulphide to the elemental form. The lead-rich solution is fed into a diaphragm electrolytic cell depositing lead and regenerating ferric fluoborate. The introduction of sulphate reducing bacteria technology in the sulphidization step of the battery paste improves dramatically the economics of the CXEWS process, reducing the costs of chemicals, avoiding gypsum disposal and minimising the unit operations of the process. This paper describes in detail this technology change with reference to the economics of the process.

Jan 1, 2000

By Stephen R. Brown

Current conditions in the copper market demand that mine and plant operators make budgeted production targets at the lowest possible unit costs. For those companies bringing new production capacity on-line, achieving budgeted production levels as quickly as possible after start-up is vitally important to minimize unit costs and to begin a positive cash flow. Whether the objective is to simply improve unit costs or successfully start-up a new, complex plant, success will be strongly influenced by .the skill levels of the operators :and supervisors. The only way to assure return on plant investment, and to survive during depressed metal prices, is to ensure that plant operators have the knowledge to effectively run the plant. Technology available in computer-based, multimedia training systems, including: interactive animation, videos, voice-overs, schematics, and text can now be used to train operators at their own pace using plant-specific information. Additionally, it has been shown that learning through multimedia provides a higher degree of long term retention than more traditional learning methods.

Jan 1, 1999

By M. C. Ruiz

The leaching behavior of chalcopyrite concentrate in acidic CuC12-NaCI-O2 solutions was investigated. Experiments were conducted under continuos flow of oxygen at atmospheric pressures. The results indicated that among the variables temperature has the largest influence on the dissolution of chalcopyrite in this medium, and high copper extraction can only be obtained at temperatures near the boiling point of the solution. It was also found that the stirring speed did not influence appreciably the dissolution of chalcopyrite. An increase in the oxygen flow rate up to 0.1 1/min increased the copper extraction. The total chloride concentration affects the dissolution of chalcopyrite up to about 4 M. Copper extraction of 93 % was obtained in leaching chalcopyrite of size fraction -400 # Tyler at 105 OC in 2 hours.

Jan 1, 1997

By Supachai Surapunt

The distribution behavior of V A minor elements (As, Sb and Bi) in the smelting stage of the Mitsubishi process were evaluated thermodynamically based on thermodynamic data and operating data. The fractional distributions between the gas, slag and matte phases considered as the degree of vapor saturation of 1.0 are as follows: 53.8, 27.2 and 19% for As, 23.6, 56.6 and 19.8% for Sb, and 91.3, 1.1 and 7.6% for Bi, respectively. Arsenic is mostly distributed to the gas and slag phases. It is effectively eliminated by volatilizing and slagging. Antimony is mainly in the slag phase, which is suitably removed by slagging. Bismuth is easily vaporized to gas phase. The degree of vapor saturation has a large effeet on the distribution behaviors of the three elements between the three phases. The amount of a minor element in the charge has an effect on the distribution of As but no effect on the distributions of Sb and Bi. Increasing matte grade and temperature results in the change of distributions for As and Sb, significantly. The change in the distribution ratio between slag and matte phases also considerably affects the distributions of As and Sb. The distribution behavior of Bi is not significantly changed by the change in matte grade, temperature and distribution ratio.

Jan 1, 2003

By P. T. Velu

Solubility of metal oxides in the molten salt electrblytes is an important parameter in the electrochemical processing of metals and alloys. The efficiency of an electrochemical process primarily depends on the quantity of metal oxide present in the electrolyte in the dissolved form and its thermodynamic properties. The activity of CeO2 was calculated using the free energy of fusion of CeO2,{ AG°m, CeO2. The AGOm,CeO2 }was deduced from the values of enthalpy, heat of fusion and melting point of Ce02. The activity coefficients of CeO2 as a function of temperature and melt composition were calculated. The thermodynamic data such as integral molar enthalpy, entropy and Gibbs energy of formation were calculated as a function of composition and temperature.

Jan 1, 1994

By Xiaodi Huang, Matthew Andriese, Zheng Zhang, Jiann-Yang Hwang, Zhiwei Peng

"The thermal decomposition and regeneration behaviors of wüstite were investigated by in situ high temperature X-ray diffraction (HT-XRD) under non-isothermal condition at heating rate of 4 K min-1 in vacuum ranging from 294 K to 973 K. Wüstite on heating decomposes to magnetite and iron up to 823 K, above which it exhibits marked tendency to regenerate. Investigation of thermal stability of the reaction system shows that the decomposition proceeds under kinetic reaction control while the regeneration is under thermodynamic control. Kinetics study based on the Coats-Redfern integral approximation method indicates that the decomposition reaction follows a Komatsu-Uemura model-based diffusion-controlled kinetics with activation energy of 32.860 kJ mol-1. The thermodynamics analysis of regeneration reaction demonstrates that wüstite regenerates at lower temperature than stoichiometric ferrous oxide.IntroductionOwing to its importance in preparing various magnetic ceramic/metal nanocompostites or nanocrystals with high values of coercivity for the application as recording media, wüstite (non-stoichiometric ferrous oxide) has been attracting the attention of scientists over a long period [1-6]. The thermal behavior of wüstite was investigated by several researchers and phase transformations due to thermal decomposition and regeneration of wüstite during the heating in a specific temperature range was observed [7-9]. In spite of wüstite being found to dissociate to magnetite and iron at temperatures lower than 848 K and then regenerates at higher temperature, a clear understanding of the reaction mechanisms is clearly lacking [9]."

Jan 1, 2012

By N. Krishna

The utilization of Electrochemical Impedance Spectroscopy (EIS) in conjunction with Atomic Force Microscopy (AFM) is a powerful surface characterization technique to study the role of sulfur formation during acidic oxidation of chalcopyrite. It has been established that the chalcopyrite dissolution kinetics is controlled by the formation of passive sulfur layer during leaching. The objective of the study was to characterize the intermediate sulfur layer formation at different oxidation conditions in acidic solution. The chalcopyrite samples were subjected to anodic oxidation and the oxidation process was analyzed using impedance spectroscopy. The sulfur growth on the chalcopyrite surface during oxidation was further analyzed using Atomic Force Microscope for sulfur roughness and grain size, peak height and sulfur growth.

Jan 1, 1999

By Y. F. Jia

Arsenic constitutes a major contaminant for the hydrometallurgical industry. Its removal and immobilization from process effluents typically involves lime neutralization and co-precipitation with ferric iron (Fe (III)/As(V)>3). Alternatively, precipitation of scorodite (FeAsO4?2H2O (cr)) may be applied to arsenic fixation. The mechanism of arsenic fixation in the former process has been suggested to be surface adsorption. Unequivocal characterization of these products is difficult because of their amorphous nature hence a variety of methods need to be applied including the particularly powerful method, extended x-ray absorption fine structure (EXAFS) spectroscopy. In this study, we have investigated the preparation of arsenate-adsorbed ferrihydrite with the purpose to compare its structure to that of Fe(III)-As(V) co-precipitates and scorodite (both amorphous and crystalline). Furthermore the solubilities of these Fe(III)-As(V) solids are measured as a function of pH. Their structures are elucidated and correlated to their solubilities and thereby the application of these findings to the practice of arsenic removal and disposal is assessed.

Jan 1, 2003

By Laila A. Guirguis

Impurities are removed from crude phosphoric acid (57.75% P2O5) with a mixture of low and high molecular weight alcohols, one of which is hydrophilic and the other is hydrophobic i.e. methanol and hexanol. In a single stage, the phosphate values segregate to the high molecular weight alcohol fraction and the impurities segregate to the low molecular weight alcohol fraction. The optimum ratio for the extraction is found to be 0.5 part methanol, one part impure acid and four parts hexanol where an extraction percent of more than 95% is achieved. Re-extraction of the phosphate value from the solvent is obtained by 6% phosphoric acid and the different factors affecting the re-extraction process have been studied. Finally, the purified acid is concentrated under reduced pressure and passed through activated carbon column, whereas the alcohols are re-circulated. The produced phosphoric acid was found to be in good match with the international specifications of food grade quality acid. A technological flow sheet is elucidated.

Jan 1, 2006

By P. E. Donaldson

Since 1992, Falconbridge has made available to the international copper industry, Kidd Creek&apos;s licensed refinery process technology under the name of the Kidd Process. This has resulted in the supply and installation of permanent cathodes and associated product handling equipment to refineries in Canada, the United States, South Korea, Chile and Mexico. These installations accommodate both electrorefining and electrowinning processes. The growth and industrial acceptance of the Kidd Process has generated technical advancements in the areas of product random sampling, corrugation, marking, labeling, product tracking and data acquisition. In a different area, the expanded development of custom materials processing at Kidd created a need to advance technologically. The process-related problem of high nickel concentrations in refinery electrolyte compromised an increase in current density to >300 A/m2. The need for nickel removal resulted in Kidd Creek&apos;s newly developed Nickel Recovery System. The effective and economical extraction of nickel, along with reduced antimony and bismuth levels, reduces bleed stream volumes and/or neutralization costs and simultaneously produces a marketable nickel carbonate product.

Jan 1, 1999

By Ian M. Ritchie

Cementation or metal displacement reactions such as Cu2+ + Fe Cu + Fe2+ are among the oldest known hydrometallurgical reactions. They are still used in the recovery of some metals and in the purification of process liquors and waste water streams. However, they are often more complex than the stoichiometric reaction would suggest because they involve the simultaneous deposition of one metal onto a second which is dissolving. For example, sometimes a cementation will not take place, even though it is thermodynamically favoured. On other occasions, a cementation reaction will start but come to a halt as the depositing metal blankets the reacting surface. On yet other occasions, side reactions, catalyzed by the deposit, can be important. In this paper, the electrochemical basis of cementation reactions is described. The conditions for each of the complications encountered in these reactions are described and illustrated by examples drawn from a number of hydrometallurgical processes. The cementation reaction between activated carbon and gold thiosulfate is also briefly described, this reaction being unusual in that no dissolution of the carbon occurs.

Jan 1, 2003

By Jiechao Liu, Lijian Luo, Yubao Ma, Bo Zhang, Yanfeng Yang, Xin Hong, Luming Liu, Jienan Liu

Reduction kinetics of stainless steel slag in iron bath smelting reduction was studied at the temperature of 1500℃ ~ 1650℃. It was concluded that the reduction process consisted of two parts. That is to say smelting reduction was controlled by stainless steel slag melting initially and by interface reaction later. In order to increase smelting reaction rate, the melting point of slag should be decreased at the first stage and adjust the liquidity of slag at later stage. Smelting reaction rate will be accelerated by means of optimize the slag content. The optimal reduction result that all most all of the chromium in slag been recovered was obtained in temperature was 1500℃, basicity of slag was 1.0~1.2, the value of Al2O3+MgO was 25%.

Jan 1, 2015

By Xiaohui Li, Lianyun Liu, Hongmin Zhu, Chunfang Zi, Kai Huang, Hongjie Li

"The dissolution kinetics of steelmaking slag in pure water was studied, and the relative influential factors were investigated. The dissolution behavior of slag particles in water was well described by Noyes–Whitney equation, and for this kind of sparingly soluble rigid mineral this simple model was extensively applicable to describe their dissolution process. Experimental data were also obtained to confirm the significant promotion effect on the growth of some algae.1 . IntroductionIt has been found that the population of phytoplankton distributed in the ocean was significantly related to the concentration of some elements [1]. For example, silicon and iron were very low in the high-nitrate low-chlorophyll (HNLC) areas, which was the main factor limiting phytoplankton and other biomass growth in these open ocean surface water [7]. The silicon and iron-rich test also confirmed that the supply of these elements had the direct effect on the growth of phytoplankton processes at HNLC areas [2-8]. So in order to promote the growth of phytoplankton in these ocean areas, providing some of these elements into these ocean areas is a natural idea for choice. Steelmaking slag is a good resource for consideration because it usually contains silicon, iron, phosphorus and other elements that are necessary for the growth of phytoplankton [8-10].Haraguchi has proposed the following idea that [5-6], if steelmaking slag can be spread to the open ocean, the trace components like silicate, iron and phosphate as the indispensable nutrients for the growth of phytoplankton, will be leached into the sea water, not only promoting the growth of phytoplankton, but also making good use of these huge amount of steelmaking slag produced every year. Based on this idea, they have carried out studies in recent years and they found that silicon and iron in the slag could be extracted into seawater effectively and play a positive role in the growth process of many algae. About the dissolution of the steelmaking slag, the Japanese scholars' research work mainly focused on the thermodynamic analysis of its dissolution possibility, and in the process of dissolution they tried to adjust the pH value of the seawater by continuously adding hydrochloric acid, which was deviated from the natural conditions of dissolution, and so the laws drawn under these special conditions can not give the identical guide to the practical application. Therefore, it is quite necessary to investigate the dissolution behavior of the steelmaking slag in the seawater at the normal pH range without adjustment to simulate the dissolution possibility under the natural conditions. In the present study, the silicon extraction behavior from the steelmaking slag was investigated and the dissolution kinetics in this process was also discussed in detail. Further studies were also performed here to evaluate the promotion of steelmaking slag on the growth of algae."

Jan 1, 2011

By Gerson de Araújo Filho

This paper shows the use of tires as fuel to be employed into blast furnaces. The tires can substitute coal or even charcoal in the blast furnaces tuyeres. The injection into tuyeres, besides the contribution for energy generation, can also produce gas for iron oxide reduction. The tires, as powder to be injected into blast furnaces, contributes for an environmental use of this waste, which helps to obtain a high value product as well. So, the advantage of using such material is that it is waste and has lower cost for preparation. The obtained results showed that the tires have good combustibility. This one was obtained in a model that simulates the same conditions occurring in the blast furnaces tuyeres; these used raw materiais include tires and mixtures of tires with coal or even with charcoal.

Jan 1, 2006

By Anand Kumar, Pradeep kumar Jha, Suman Kant, Pradeep Kumar

"It has been a major challenge to reduce the intermixed grade formation during ladle change-over operation in continuous casting process of tundish steelmaking. The F-curve generated by step input of the tracer (new grade steel) tells about the intermixed grade amount for different grade specifications. Use of flow modifiers is beneficial in reducing the intermixed grade because of the change in slope (in different time zones) and position of the F-curve due to their placement at tundish bottom. Present study aims at investigating the role of dam placed before the outlet in a multi-strand tundish with reference to the slope behavior of F-curve in different time zones during the teeming operation plays an important role in determining the intermixed amount.Introduction In Continuous casting process, the old grade steel remaining in the tundish (reservoir between ladle and mould) from the old ladle gets mixed with new grade steel from new ladle and leads to intermixed grade which is considered to be of inferior quality. Although formation of intermixed grade is inevitable with the sequential method of casting, its amount can be controlled by changing the flow behavior of steel inside the steel. Intermixing in a slab caster tundish was simulated using 3-D numerical model based on k-å turbulence equation and compared their result with that of water model experiment Yeh and Hwang [1]. Huang and Thomas [2] reported that quantity of residual fluid in tundish affects the composition distribution in the transitional slab and thus the intermixed length. Huang and Thomas [3] developed three sub models to predict mixing in tundish, liquid core of strand and solidification. Thomas [4] developed a one dimensional model to simulate the final composition distributions in slab caster of continuous casting and investigated the effect of process variables on the intermixing. Alizadeh mehdi et al., [5] simulated of the intermixing phenomenon for slab casting for three different sub models. Goldschmidt et al. [6] developed a numerical model that predicted the location of the intermixed steel in a four line round caster. Lan and Khodadadi [7] studied for the transient fluid flow of liquid steel, heat transfer and solidification during the flying tundish change process. Cho and Kim [8] developed a mixing model to predict the outlet concentration of the tundish during grade transition. Most of the work reported in the literature has dealt with intermixing in slab caster tundish. Billet caster units are more often being used by steel industries due to growing demand of billets. The multiple outlets lead to varying degree of intermixing with time owing to their different distance (location) from the inlet. Use of flow modifier to minimize the intermixed amount, however has also not been discussed in detail so far. Further no work has been reported regarding effect of slope of F-curves obtained through different outlets on intermixing. Hence keeping these objectives in mind attempt has been made by authors to analyze the slope of Fcurves after dividing them into three different time zones and the effect of these time zones on intermixing."

Jan 1, 2012

By Natasa Mitevska

The statistical analysis of the slag composition influence on copper losses to discard slag in the reverberatory furnaces No.1 and No.2 in the RTB BOR, Copper Smelter and Refinery (Yugoslavia) is presented in this paper. The model for the slag basicity calculation is determined, and connected to the copper distribution coefficients between the matte and slag phase. The influence of all components on the slag structure is also illustrated.

Jan 1, 2003

By Norimasa Yamasaki, Masao Kurosaki

"The effects of plating conditions on the crystal orientation of electrodeposited zinc were investigated by varying elecyrolyte flow rate and current density. Precipitation of the Zn (00 • 2) basal plane is promoted at lower current density and higher flow velocity. Effect of the flow velocity on the mass transport was evaluated based on the polarization measurement in which Cu was used as the tracer. As a result, it has been clarified that the crystal orientation of electrodeposited zinc can be uniquely arranged by the overvoltage (iU0.5) that can be simply calculated by considering -the current density and boundary layer thickness. At the same time, the electrode potential during electrodeposition that can be calculated by using a model based on the competitive reactions of hydrogen reduction 'and zinc reduction exhibits an extremely good correlation with the crystal orientation of electrodeposited zinc.Introduction Electrogalvanized steel sheet has better surface properties than hot-dip galvanized steel sheet, and is used in home electric appliance and automobile applications. Factors such as crystal morphology, crystal orientation and surface roughness have a large influence on its appliance, formability and corrosion resistance [1-3].Electrolysis, condition, bath composition and alloying elements are reported as factors that affect the crystal orientation of the electrogalvanized coating. Factors that can be controlled on time in the production site are electrolysis condition that-is current density and plating solution flow velocity.Some studies[4-6] report that the crystal- orientation of the Zn(00 • 2) plane is increased by promoting, the mass transfer of zinc ions in the plating solution or decreasing the concentration overvoltage, but did not investigate in detail the plating solution flow conditions in the plating cell nor quantitatively determine the effects of both current density and plating solution flow conditions on the crystal orientation of ' electrodeposited zinc."

Jan 1, 2000