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By Yu Yamashita

There have been increasing in melting recycled scraps in copper smelting processes, and thus growing interests in the chlorine behavior. In this study, chloride dissolution in FeO-Fe2O3-SiO2slag (SiO2sat.) at 1523 K has been measured with varying in PCl2 from 1.13x10-8 to 1.30x10-7atm. and the oxygen partial pressures encountered in typical copper smelting furnace, i.e. PO2=10-8 to 10-10 atm. Discussion is made on the chloride capacity of FeO-Fe2O3-SiO2 slag in terms of its characteristics and the dissolved chlorine species. It has been shown that the mostreasonable dissolution reaction and chloride capacity can be expressed by the following reactions, where chlorine dissolves in the form of Cl-; here, aO2-, oxygen ion activity, is shown a function of oxygen partial pressure in the atmosphere. [ ]

Jan 1, 2006

By Thomas Havlik

It is proposed to realise the direct leaching, during which will be generated elemental sulfur and not sulfate or sulfuric acid as end product, under conditions that sulfur will not cover the leaching surface and Hot hinder the leaching course. The following improvements have been considered: -use of organic sulfur solvents -ultra high-frequency leaching -ultrasonic leaching -use of surface detergents or surfactants in leaching processes -simultaneously crushing and leaching These proposals are under investigation and preliminary results are promising

Jan 1, 1996

By Yanping Xiao

In submerged-arc furnace (SAF) for smelting chromite ores into ferrochrome, there exist large temperature gradients and wide distributions of mineralogy and compositions in the furnace, due to the complexity of feed structure and electrical-thermal-chemical interactions. This leads to various zones in the furnace and thus different reaction mechanisms. In the present paper, the behaviour of chromium in the submerged arc furnace is discussed in various reaction zones, including solid state chromite reduction in the packed bed zone, chromite dissolution and reactions in the smelting and coke bed zone, and recovering chromium from slag to metal. In the gas-solid reaction zone, the reaction mechanism is discussed based on the experimental observations and analysis. In the smelting zone, the behaviour of partially reduced chromite and slag formation are analyzed based on the information in literature. The slag in FeCr process contains mainly Al2O3, MgO, SiO2, CaO and CrOx, featured by chromium with both divalent and trivalent oxidation state, which plays an important role for chromium recovery into metal. The factors influencing the slag and metal interfacial reactions and the chromium recovery are addressed.

Jan 1, 2006

By Jan G. H. du Preez, C. Viviers, B. J. A. M. van Brecht, H. E. Rohwer, Nicole M. Sumter

"At the basis of metal ion separation lies some particularly metal ion specific chemical property which lends itself towards exploitation. This could be in the form of an anionic complex or a neutral chelate complex. In the former a cationic centre with a particularly high affinity for the complex will have to be designed. In the latter case a stereospecific chelate ligand containing the correct symmetry and type of donor atoms will have to be designed. In both above cases the ""active centre"" can be entered in a from that it can function in different media of hydrophobicity, eg a precipitant, a resin or a solvent extractant. Recent results obtained in this laboratory will be used to illustrate how the above variables can be exploited to develop improved processes for the separation of base metal and platinum group metals.IntroductionThe separation of metal ions in hydrometallurgy can be performed broadly speaking with two major aims. Firstly the separation/removal of a certain group of metal ions, either as a means of preconcentration or as a removal from effluent as part of a purification process and, secondly the removal of a specific metal ion from an industrial stream in order to produce a specific metal in a pure form. This latter operation is by far the most difficult of the two and is becoming more so in the light of the fact that the world is moving in the direction of lower grade ores and increasing pollution. Such a process can be divided into three essential parts, firstly the molecular one in which an active centre is required to obtain specificity, secondly a matrix within which this active centre must function, i.e. as part of a resin or solvent extractant and thirdly the design of the total system to optimize the realization of the operation."

Jan 1, 1996

By Luis W. Pommier

The wastes of the plating industry are generated in the process of rinsing the plated objects and during the cleaning of the plating shops. High volumes of hazardous waters are neutralized on site producing recyclable water, generating a metal rich, hazardous, filter cake. Occasionally, a complete plating bath has to be discarded which increases the metal content of the filter cakes. These filter cakes are discarded as hazardous at a cost of over $ 250 per ton. The metals found in the cakes are generally copper, nickel and chromium or zinc, lead and cadmium, assaying from 2% to 15% or even higher content of each metal The metals and their contents are highly variable. Some plating shops discard their products directly to hazardous waste sites, others, have them collected by companies which consolidate wastes from several producers prior to discarding. These wastes, richer in metal content than mine ores, need neither mining nor crushing and grinding for concentration. The commonly found impurities in the mine ores, i.e.: pyrites, arsenic, and valuable metals which are present in minute quantities, are absent in the filter cakes. The processes available to selectively recover the metals from the filter cakes, are discussed based on their technical and economic merits. The flow-sheets include leaching, solvent extraction when required, and electrolytic refining. Examples, showing the separation of copper, nickel and chromium and also of zinc and lead in pilot plants, show the technical and economic viability of the processes.

Jan 1, 1996

By Jimsher Aneli

The investigation of some peculiarities of conductivity dependence on filler type and amount in the polymer composites has been conducted. It is established, that conductivity of composites based on phenolformaldehide resin essentially depends on proportion of double fillers: graphite + carbon black, graphite+ andesite, contained in composites. It was shown, that these composites characterized by synergetic effect ? non additive influence of fillers concentration on the conductivity of composites. Some other properties of composites contained binary fillers (effect of temperature and pressure on the conductivity) have been investigated.

Jan 1, 2006

By William Petrul

Image analysis studies were performed on mill products from laboratory flotation tests of the Zn-Pb ore from the Faro deposit in Yukon, Canada, to determine mineral liberations at specific grinds and to predict recoveries at optimum flotation conditions. The minimum and optimum grinds for liberating sphalerite and galena were predicted from size analysis data for the minerals in large ore pieces, and determined by image analysis studies of the mill products. The determined optimum grinds are about 2 Tyler mesh sizes larger than predicted because sane of the fine grained sphalerite and galena occurs in interstices between coarser grained pyrite and is liberated when the pyrite grains are broken apart. Materials balance calculations were performed on the analyzed values for the liberated and unliberated sphalerite and galenaa to determine their distributions in the mill products. The laboratory flotation tests recovered 74% of the sphalerite and 83% of the galena in Zn and Pb concentrates respectively. The mineral evaluation study indicates that the optimum recovery for sphalerite and galena are 85 and 83% respectively. The company is currently recovering 80% 'of the sphalerite and 82% of the galena.

Jan 1, 1989

By Jackson Jenkins

The second survey of world copper SXEW plants has been completed. Solvent extraction and electrowinning data published in 1996 has been updated and leach data from seventeen plants is now included. The following pages list the results of the thirty- two plants that responded to the survey. Selected information is summarized in graphical form.

Jan 1, 1999

By A. V. Tarasov

In order to improve the efficiency of hydrometallurgical processing of pyrrhotite concentrates, an integrated set of research has been carried out to investigate the use of sulfur dioxide in individual unit operations and as a leaching agent in the autoclave process as a substitute for oxygen. Treating iron-containing raw materials for production of nonferrous metals are based on the selective reaction of SO2 with iron sulfides and oxides. Iron is dissolved as sulfate, which can be treated in a separate circuit to produce iron-containing pigments or it can be disposed of after neutralization. Nonferrous and precious metals contained in pyrrhotite concentrate do not react with sulfur dioxide and remain virtually completely in the solid phase, i.e. high-grade sulfide concentrate to be treated by hydro- or pyrometallurgical methods. Elemental sulfur formed in the process of leaching is separated from the pulp in granulated form as a result of the use of special surfactants. The process of sulfide concentrate leaching with the use of sulfur dioxide is conducted at temperatures above the sulfur melting point (119°C) with distributed feeding of surfactant and under a partial pressure of sulfur dioxide of up to 0.3 to 0.5 MPa.

Jan 1, 2006

By Vinay Kumar, Jae-Chun Lee, Rakesh Kumar, Manis Kumar Jha, Archana Kumari, Pankaj Choubey

Present work is a part of developing novel recycling technique for waste printed circuit boards (PCBs) i.e. the liberation of metals from PCBs by organic swelling followed by the treatment of resin to remove/ recover hazardous soldering materials. In order to recover the hazardous metallic constituent lead from the liberated resin, initially the leaching studies were made using fresh solder containing 63.9% Pb and remaining tin. Experimental results obtained in different conditions viz. time, temperature and acidity showed -97.20% of lead dissolution with 6M HNO3 at solid to liquid (S:L) ratio 1:10 (g/mL) and temperature 90°C in 75 minutes. The result of the studies validated with crushed PCBs shows that almost total lead and tin was leached out with 6M HNO3 and 6M HC1 respectively at S:L ratio 1:10 (g/mL) and temperature 90°C within 50 minutes. The results will be useful for the treatment and safe disposal of PCBs resin.

Jan 1, 2011

By Shadia Ikhmayies

In this work Thermo-Calc software was used to calculate the phase diagram of the Fe–Si system. The deduced phase diagram includes twenty fields, where three fields represent pure phases; two solid solutions and a liquid phase. There are several fields of two co-existing phases; mixed solid phases, and mixed solid with liquid phases. A set of eutectic and eutectoid points were found, where transformation reactions and temperatures were identified. The results were compared with results in the literature and good agreements with some differences were found. This study is a step to understand the phase diagram of Ca–Fe-Si system for refining metallugical grade silicon (MG-Si).

Mar 1, 2018

By X. J. Wu

Effects of various factors such as diaphragm materials, composition of electrolytes and current density on copper electrowinning from cupric chloride solutions was investigated. It is found that the crux of this process is to prevent the dissolution of copper by cupric ion and the formation of suspended CuCl precipitate. A process with high difference of copper concentrations between the feed solution and the spent electrolyte was selected. With this process, in which the feed solution contains 90 g/dm3 [Cu"], 3M NaC1, and 10mg/dm3 bone glue, and the spent electrolytes contains 10 g/dm3 [Cul, a very smooth and dense copper cathode can be produced with current efficiency above 93% and energy requirement less than 1.7 kwh/kg Cu at 25°C with N2 sparging. If a slightly higher energy requirement is permitted, smooth and dense copper cathodes can be produced at the current density up to 800 A/m2 with the identical solutions.

Jan 1, 1991

By Derek Fray

Molten salts have been used for the extraction of metals since the 19th century but, recently, many interesting processes have been investigated using mixtures of molten salts and different cathodic materials. In several existing processes, the cation is simply discharged from melt but, in some cases, complications arise when the electrode potentials of the cations are relatively close. For example, the co-deposition of sodium with aluminium in the Hall-Heroult process is discussed in terms of electrode potentials of the components in the molten electrolyte. Similar considerations will also be given to the anodic reactions with respect to chlorine, oxygen, carbon dioxide or monoxide evolution from chloride-oxide melts. In some cases, the cathodic product interacts with the cathode to produce new and exciting products such as nanotubes from carbon or titanates and reduced titanium oxides from titanium dioxide. Depending on the electrode potentials, it is also possible to completely change the cathodic reaction from discharge of the cation in the salt to ionisation of the anions in the cathode. Examples are given of the reduction of metal oxides to produce metals, high technology alloys and nanomaterials and the cathodic refining of liquid metals.

Jan 1, 2006

By T. Taniguchi

The existing Mitsubishi Process line at Naoshima Smelter and Refinery has been operating successfully since 1991, and its present production capacity is 270,000tpy of copper. Furnace relining works have been carried out every two years to coincide with the compulsory bi-yearly boiler inspection, but the next target is to extend the furnace refractory life to four years, while still undergoing the mandatory boiler inspection every two years. Although the damage of hearth bricks beneath lances in the Smelting furnace was a matter of concern, it was reduced by controlling gas velocity and evening solid distribution to each lance. The life of bath level bricks in the Converting furnace was also a concern, but four-years continuous use of the bricks was achieved in the course of the last two campaigns. Several other improvements were also carried out to the cooling systems during the shutdown in 2005 to ensure longer campaign life. This paper summarizes recent improvements implemented to enhance the advantages of the Mitsubishi Process.

Jan 1, 2006

By G. St-Amant, V. Cloutier, E. Ghali, S. Jin, G. Houlachi

During the casting of lead-silver anodes, variations in cooling rates result in the formation of an uneven microstructure. The slowly cooled areas (SCA) have a coarser microstructure than that of the remaining part (called "the general zone"). The effect of anode microstructure on the electrochemical behavior was investigated using galvanostatic, potentiodynamic and electrochemical impedance techniques. The results show that the resistances for the two steps of the oxygen evolution reaction on the slowly cooled areas of Pb- Ag anodes are higher than that on the general zone. The double layer capacitance for the first step of the oxygen evolution reaction (OER) and the pseudocapacitance of the second step of OER on SCA are smaller than those on the general zone. The potentiodynamic results show that the amount of lead dioxide formed on the SCA is greater than that of the general zone of the anode. The potential decay curves after 30 minutes of galvanostatic polarization at 45 mA/cm2 show that the corrosion potential of the SCA is 200 mV lower than that of the general zone. This can lead to perforation because of the formation of a galvanic cell with a small anode and a large cathode.

Jan 1, 2000

By Nedam Abed

A fundamental study of the sonochemical leaching of chalcopyrite in ferric ion media has been performed to understand and quantify the effects of sonication and other parameters on leaching reactions. The study covers sulfate and chloride media. The main leaching reaction: CuFeS2(s) + 4Fe3+(aq) Cu2+(aq) + 5Fe2+(aq) + 2S(s) (1) was found to be dependent on temperature and initial particle size, but less dependent on ferric ion concentration. Leaching kinetics were not affected by ferrous ion concentration or the amount of chalcopyrite added. Leaching was performed under a variety of sonication and leaching conditions. Reaction stoichiometry was confirmed through detailed wet chemistry analysis and mass balance calculations. The use of ultrasound activation showed a clear improvement in leaching kinetics and amount of copper extracted, sonication having a catalytic-like effect on the leaching reaction. Compared to experiments without sonication, reaction rates were 2-3 times faster at the same temperature, and could be faster by a factor of 20 for the same initial particle size. Regardless of initial particle size, the amount of copper extracted was comparable under sonication, and could be twice that under chemical leaching, implying the avoidance of fine particle grinding. Sonochemical leaching was found to be only temperature dependent, where the best copper extraction was at 75C. Leaching was further enhanced by the use of a grinding aid. The leaching behavior of chalcopyrite particles remained similar with and without ultrasound activation, implying that the known passivation mechanism in the oxidative leaching was not eradicated. Sonication resulted in coarse particle breakage (ultrasonic milling). Sonication did not contribute to particle passivation, as affirmed from different leaching procedures and sonication in aqueous and organic media. Parabolic leaching kinetics were confirmed for leaching experiments.

Jan 1, 2003

By F. Sekula

Tetrahedrite and siderite are two main valuable minerals present in the silver Mária Bana deposit. The tetrahedrite concentrate prepared from it by flotation has certain specific properties from the metallurgical point of view. Siderite is concentrated in the flotation tailings. The paper presents results of the laboratory and pilot-plant testing of the combined hydrometallurgical and pyrometallurgical methods proposed for treatment of the tetrahedrite concentrate and siderite waste. The testing conditions were based on thermodynamic analysis of the reactions that proceed in the process. The proposed technology makes it possible to separate copper from sulphur, mercury and iron in a straightforward way. Copper, after its refining, can be subsequently treated in the finishing operations. At the same time it is a valuable source of precious and noble metals. The siderite-containing flotation tailings can be converted to iron of the technical purity and slag. The proposed method is a good starting point for the development of the closed-cycle technology.

Jan 1, 2006

By Biserka Lucheva, Tzonio Tzonev

"Recycling of aluminum scrap and dross is significant in the economic and energy saving, as well as in the environmental protection. Recovery of metal aluminum depends on many factors. The aim of this work is to investigate experimentally the metal recovery under different conditions. The processing of aluminum dross was carried out in DC electric arc rotary furnace. The optimal technological parameters are determined. It is turned out that the presence of crushing refractory bodies during the processing of the aluminum dross in the rotary furnace increases the degree of aluminum recovery with about 10 %.IntroductionCompact and granular aluminum dross are used for the fulfillment of the experiments, which were obtained by salt free melting of aluminum scrap. The only preliminary preparation of the compact dross is crushing them into proper size, in compliance with the size of the opening for furnace charging and removing of fraction – 1 mm. The granular dross is subjected to sieving also with the purpose to remove the fraction – 1 mm. In these conditions the content of the metal phase in the compact dross is 72 %, and in the granular – 77 %. The processing of aluminum dross was carried out in DC electric arc rotary furnace (Figure 1).The purpose of this research is to investigate experimentally the metal recovery under different conditions and to establish the dominant factors, which need to be controlled."

Jan 1, 2008

By Yunqing Tian, Wenbin Huang, Weidong Zhang, Xiaopeng Wang, Gele Qing, Xiangjuan Duan

Pellet production requires iron ore concentrates have fine particle size, high specific surface area and good balling performance, so iron ore concentrates appropriate for pelletizing is limited compared to sintering. In order to extend the iron ore resources for pelletizing, the iron ore fines for sinter are studied in this paper.The effect of grinded iron ores o npelletizing, roasting and pellet quality were studied in this paper. The bond grinding index of iron ore fine is between 12.5 and 16.98 kwh/t. The grinded iron ore fine has good balling performance, the drop number and compressive strength of green pellet were improved with increase of grinded iron ore fine ratio. The compressive strength of roasted pellets were decreased with increase of grinded iron ore fine ratio, however it can be reached 2500 N.P −1 while proportioned with more than 80% of magnetite iron ore concentrate.

Mar 1, 2018

By Ahmad Umar

A variety of ZnO nanostructures such as sea-urchin-like structures composed of nanowires and nanorods, nanocombs, nano/micro spheres and cages, star-shaped ZnO nanostructures, flower-shaped nanostructures, needle-like nanostructures etc. have been synthesized applying two different fabrication techniques i.e. thermal evaporation and cyclic feeding chemical vapor deposition techniques at different reaction parameters such as reaction temperature, growth period, reactant concentrations, types of source material and substrates etc. It was observed from the experiments that the morphologies of the grown structures were highly influenced by the reaction parameters and fabrication techniques and specific morphology can be obtained at particular reaction parameters in a specific synthetic procedure. Extensive morphological investigations of the obtained products demonstrate that the grown structures are single crystalline and having a wurtzite hexagonal phase. Room-temperature photoluminescence spectra of all the deposited products exhibited good optical properties. Finally, the growth process of the fabricated structures were proposed and discussed in detail.

Jan 1, 2006