ELECTROCHEMICAL PROCESSING OF MINERALS, METALS AND MATERIALS

Authors: Przemyslaw Los, Michal Gieron, Slawomir Ruta, Przemyslaw ZaprzalskiNanometallurgy S. A., PolandIn our previous studies we have shown that potentiostatic (and potentiostatic pulse) electrolysis could be applied to obtain copper powders and nanopowders of high purity from copper industrial electrolytes. On the basis of the results a new, patent pending technologies of electrorefining and electrowining have been developed. In this paper for the first time the pilot scale test results of the technology will be presented. The properties of the cathodes obtained using a new process as well as some of its important parameters will be discussed. The new method can be implemented in the existing copper refineries without essential changes in the tank houses apart from the power supplies (rectifiers) which should fulfill certain specific requirements. There are many advantages of our process in comparison to the existing galvanostatic electrorefining and electrowining namely much higher cathode current densities can be used to obtain commercially pure (grade A) copper deposit with very high current efficiencies which can eventually contribute to factory foot print reduction and/or production scale-up. Other positive aspects of our technology result from the fact that stainless steel cathodes can be used, cathodic copper is received in broad spectrum of copper content in electrolyte from 50g/liter to 1mg/liter with the commercial purity of >99,9%, there is no co-deposition of Arsenic, there is no evolution of AsH3 gas. New layouts of electrorefining and electrowining plants will be discussed.

Broadly speaking, a liquid crystal display (LCD) contains several electro-conductive electrodes, which are sandwiched between two glass planes. These electrodes are made mainly of indium tin oxide (ITO), which is is a mixture of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2). Considering that indium(III) oxide has a higher (s. P.) sublimation point (s. P. Of In2O3: 2273K) than indium(III) chloride (s. P. Of InCl3: 573K), the authors are putting forward a chloride-induced vaporization process in order to recover In, which is one of the most valuable component of the obsolete LCDs. The aim was not only to increase the recovery but also reduce the energy consumption of the process. The process includes a HCl treatment process for altering the structure of the indium(III) compound into a chloride-induced indium compound, in order to facilitate the vaporization of indium at a relatively low temperature. The chloride-induced indium compound is then vaporized. Finally, the vaporized indium compound is condensed as on a cooled surface of the apparatus and then recovered. The experimental results indicated that, by using this process, 84.3 % of indium can be recovered from LCDs of the discarded cellular phones. In addition, some thermodynamic calculations were also carried out in order to better understand the mechanism for chloride-induced vaporization of indium.

Corrosion inhibition property of N-(phenylcarbamothioyl)benzamide (PCB) on mild steel in 1.0 M HCl solution has been investigated using chemical (weight loss method) and electrochemical techniques (potentiodynamic polarization and AC impedance spectroscopy). The inhibition efficiencies obtained from all the methods are in good agreement. The thiourea derivative is found to inhibit both anodic and cathodic corrosion as evaluated by electrochemical studies. The inhibitor is adsorbed on the mild steel surface according to Langmuir adsorption isotherm. The adsorption mechanism of inhibition was supported by spectroscopic (UV-visible, FT-IR, XPS), and surface analysis (SEM-EDS) and adsorption isotherms. The thermodynamic parameter values of free energy of adsorption (∆Gads) reveals that inhibitor was adsorbed on the mild steel surface via both physisorption and chemisorption mechanism.

Anticorrosion property of N-(phenylcarbamothioyl)benzamide (PCB) on mild steel surface in 1.0 M HCl solution has been investigated using chemical (weight loss method) and electrochemical techniques (potentiodynamic polarization and AC impedance spectroscopy). The effectiveness of the inhibitor from all the methods are in good agreement. The thiourea derivative is found to inhibit both anodic and cathodic corrosion as evaluated by electrochemical studies. The inhibitor is adsorbed on the mild steel surface according to Langmuir adsorption isotherm. The adsorption mechanism of inhibition was supported by spectroscopic (UV-visible, FT-IR), and surface analysis (SEM-EDS) and adsorption isotherms. The thermodynamic parameter values of free energy of adsorption (∆Gads) reveals that inhibitor was adsorbed on the mild steel surface via both physisorption and chemisorption mechanism. The layer formation on mild steel surface was confirmed by XPS analysis.

A study on the evaluation of the effectiveness of atrazine degradation by in situ electrochemically generated ozone was conducted. Continuous atrazine degradation tests were conducted in a horizontally mounted column packed with washed sand. The purpose of these tests was to determine whether the in situ electrochemical production of the oxidants •OH/O3 is effective at reducing the atrazine concentration in the transported flux across the bed. The porous bed parameters (porosity and dispersivity) and the mean residence time of a KCl tracer in the column were determined. Atrazine degradation runs to evaluate the degradation efficacy as a function of the applied current were conducted. Fractional oxidations of atrazine of 75% and 80% were accomplished in a column containing a porous media for 0.4 A and 0.6 A respectively. The work demonstrates the potential applicability of the continuous system for in situ atrazine degradation in underground waters, and provides a basis for the future development of this technology.

Copper is a metal almost always present in gold mining effluents, since many gold ores are associated to pyrite, arsenopyrite and copper sulfides, such as chalcopyrite, chalcocite, bornite, enargite, covellite, besides native and copper oxides/carbonates. As these minerals are, in some extent, soluble in cyanide solutions, they consume dissolved oxygen and cyanide, competing with gold and silver leaching and slowing down precious metals dissolution rate. Furthermore, copper-cyanide complexes interfere with subsequent recovery processes and increase the bullion contamination. In this paper, the recovery of copper from gold mining waste streams with a lab-scale flow-by electrolytic cell was investigated. Stacks of stainless steel and titanium meshes were tested as cathodes and a ruthenium oxide layered titanium grid was used as anode. Tests with both synthetic solution and a real gold mining effluent have shown that under favorable conditions, more than 99% of the copper and all the residual gold and silver can be removed from solution in less than one hour. A preliminary analysis indicated that power consumption can be paid by the metallic copper recovered.

The cathode copper spiral elongation (SEM) is one of the parameters of the quality of copper grade A. The direct control of SEM value on the process of electrolysis is not possible due to the absence of the information about the dependence of the precipitated copper SEM on the electrolysis parameters (current density, electrolyte composition, temperature, its circulation rate, etc.). Thus, it is advisable to use the information on admixtures content in cathode copper for preliminary assessment of SEM value being in correspondence with LME requirements. For this purpose it is necessary to reveal the correlation between SEM value and the content of some admixture in copper or of their groups. In case positive relation is revealed the control can be carried out by the copper chemical composition. The task was solved with the use of Principal Components Analysis (PCA) in order to process the information on the chemical composition of the cathode copper from world-known producers of two classes. The first class – 25 copper refining operations producing copper certified by LME as grade A copper that is with assured SEM value being more than 400 mm. The second class consisted of 12 operations that had no copper brand of such quality. As soon as by its chemical composition the cathode copper of all producers corresponded to grade A, the brand absence was taken as the evidence of copper quality unconformity by SEM value. In the result there was revealed the correlation between SEM value and the content of nickel, sulphur, selenium and tellurium in copper. The correlation between SEM value and such electrolysis parameters as current density, circulation rate and electrolyte temperature is absent. The correlation between SEM value and admixtures content was verified by direct experiments, where there was used copper with variable content of the abovementioned admixtures.

Protection of the global environment, and in particular providing a sustainable source of clean water is a necessity for human survival. The wide use of heavy metals by modern industries has generated by-products containing heavy metals. Specifically, large quantities of arsenic containing compounds are being discharged into the environment. This study has been carried out to determine the feasibility of arsenic adsorption on iron species by Electrocoagulation (EC) process using the Langmuir’s Isotherm. Thermodynamic parameters such as changes of Entalphy, Entropy and Free Energy were calculed. The adsorption process found to be exothermic and spontaneous. The full potential of EC as an alternative wastewater treatment technique to remove arsenic from mine water showed more than 99 percent of removal without adding any chemical reagents. Experiments were conducted to determine the optimum operating conditions such as current density, conductivity, pH and retention time. In this study, X-Ray Diffraction and Scanning Electron Microscopy, were used to characterize the solid products that revealed the expected crystalline iron oxides (lepidocrocite, magnetite, goethite, iron oxide).

Metal (Cu2+ and Pb2+) electrodeposition was carried out under super gravity field. The deposition rate of metal increased obviously with gravity coefficiency (G), which was ascribed to the increase of limiting current density (id) and decrease of diffusion layer thickness (δ). Based on the enhanced effect of super gravity field on metal electrodeposition, electrolytic copper powders and electrochemical extraction of metal ion were performed under super gravity field. Current efficiencies of metal electrodeposition increased, while cell voltages decreased. Super gravity technology can be used in many fields, such as electrowinning, the preparation of functional coatings and the treatment of heavy metal wastewater, to advance the traditional electrochemical engineering.

This paper introduces a novel anode for electrowinning of copper, zinc, nickel, cobalt, PGM and other metals from aqueous acidic solutions. The anode comprises an oxide catalytic layer formed on a titanium substrate, and the catalytic layer is prepared by thermal decomposition of a precursor solution. While the oxide catalyst is compositionally similar to those of well-known dimensionally stable anodes (DSA), it consists of nano iridium oxide particles dispersed in amorphous tantalum oxide, which is quite different from commercially available DSA-type anodes. The novel anode shows a low oxygen evolution potential, which is at least 0.15 V lower than DSA-type anodes and at least 0.5 V lower than traditional lead alloy anodes in sulfuric acid solutions. Such potential reductions result in electric energy saving by 29% for copper electrowinning, by 18% for zinc electrowinning, and by 11 % for cobalt electrowinning, compared to lead alloy anodes. The anode also makes it possible to suppress some unwanted side reactions such as the deposition of lead oxide or manganese oxide on the anode, which are usually observed during oxygen evolution in commercial copper or zinc electrowinning. It is concluded that the developed anode is highly catalytic and selective to oxygen evolution, and it can change the electrowinning processes into more environmentally friendly ones.

Electrodeposition of metal requires mass transport of ions to the cathode surface. Mass transport of ions is interrelated to the current density, applied voltage, and the morphology and characteristics of the deposit. Nucleation and growth of electrodeposits strongly influence the final structure and morphology of the deposit, and from a commercial perspective the associated tendency to produce rough cathodes, incorporate contaminate particles, and create shorts within cells. In this study effects of mass transport from convective flow, diffusion, and smoothing additives on nucleation and growth of electrodeposits have been evaluated using a combination of experimental techniques and modeling.

Ilmenite is one of the primary sources of titanium dioxide, while titanium-rich slag generally is one product of ilmenite concentrate smelting process. In the present investigation, ilmenite concentrate and titanium-rich slag are pretreated by the alkali activation, and leached by moderate acid solutions in order to decrease the environmental loads arising from the titanium dioxide production. The mechanism of the alkali activation and acid leaching process is studied by X-Ray diffraction and chemical composition analyses. The results show the acid dissolution efficiency (ADE) of the activated concentrate and slag is significantly influenced by the ratio of NaOH-to-concentrate or slag of the alkali activation. The formation of Na+ layered intercalation compounds during the alkali activation with the higher ratio is one of the important reasons for the higher ADC of the activated ilmenite and Ti-rich slag.

The reduction mechanism of CaWO4 to W in molten eutectic CaCl2-NaCl electrolyte has been studied. Within the scope of this study, cyclic voltammetry and constant potential electrolysis tests were performed to determine the reversible cell potential. Analyses of the experimental results revealed that at least 2.2 V was required to compensate the accompanying cell reaction and the electrode polarizations. A cell reaction was proposed by associating the experimental results and the Gibbs Energy changes of the possible reactions.

The effects of hydrogen processing on the microstructure and the tensile properties of welded joints of BT20 titanium alloy were investigated. The results show that some δ-hydrides are formed after hydrogenising at 600℃ and 700℃ for 3h, respectively. Complete α+H→β(H) transmission occurs during hydrogenizition at 800℃ for 30min. A lot of metastable β(H) and martensite α" are generated by water quenching. β(H) and α" gradually decompose to α and δ by eutectoid treatment. The decomposition effect becomes heavier by rising the eutectoid temperature. Hydrogen is removed and recrystallization occurs in the process of dehydrogenisng at 750℃ for 8h in vacuum. After dehydrogenising at 750℃ for 8h in vacuum, the refinement of large grains in the fusion area is very obvious, but the original large grain boundaries are observed vaguely. After annealing in vacuum, with the increasing of hydrogen content tensile strength and plasticity decreased when the temperature of hydrogenization was 650℃. Through hydrogenising at 800℃for 30min and quenching into water, then eutectoid at 300℃ for 8h, and dehydrogenising at 750℃ for 8h in vacuum, the ultimate strength decreases and the elongation increases a little in the joints by hydrogen treatment compared with those untreated.

Cyanidation is the dominant means of recovering gold from its ores. In recovering gold from copper-containing gold ores by cyanidation, some copper minerals readily dissolve in cyanide. These can have a detrimental effect on the process efficiency and economics (high cyanide consumption and poor gold recovery). And restrictions on the discharge of cyanide and copper cyanide complexes to tailings dams due to environmental concerns. Because the high copper concentrations contain in solutions, various processes have been developed or investigated to recovering and recycling the cyanide and/or copper. This work presents some result of the remove and recovery of copper from cyanide solutions to obtain a new product, copper nano-compounds. These nanomaterials were obtaining by modified sol-gel method from the industrial cyanide solution. The results indicate that multicomponent particles can be obtained directly from cyanide solutions, opening a new emerging field for obtaining new products with high added value applications, for example, in catalysis.

Nonferrous metallurgical slag for fire-refining nickel or copper has increased year after year as a deposit, has appeared some environmental problems. On the other hand, it also has been considered a potential resource for steelmaking because a lot of Fe and Ni element existed in the slag, many researches had been carried out previously. However, these attempts had been not successful because the slag is hard-reduced in solid, and easy to form foaming-slag in liquid using carbothermal-reduction method. In this work, we try to use a new method, carbothermic-electrochemical reduction（CER）, for investigation of Ni-Fe alloy prepared from Jinchuan slag as a nonferrous metallurgical slag. Results showed the CER method is used to recover valuable metals from the molten slag, which can avoid the formation of foaming slag, and obtain a carbon-free Ni-Fe alloy. Secondly, the Jinchuan slag was pre-treated before using CER, in which 94.02% sulfur can be removed from the slag in the oxidized process, 95.04% metal oxides can be reduced in the slag in the reduced process, according to requirements for CER. Finally, the pretreatment slag was more reduced using CER method to obtain a Ni-Fe alloy that composition satisfies standard of Q460NH weather steel from China, Japan or America.

A thermodynamic analysis of the organic matter (chemical oxygen demand - COD) removal from synthetic oil-water emulsions by the electrocoagulation process was performed with the objective of determining the most stable ionic species at the diverse pH and aluminum concentration conditions, in order to identify the possible removal mechanisms. A mathematical modeling was also developed to evaluate the COD abatement. The thermodynamic analysis suggests that the predominant species during the reactive stage are the amorphous aluminum hydroxide (for the mononuclear speciation of aluminum) and the positively charged trimeric species, Al3(OH)45+ (for the polynuclear speciation of aluminum). The emulsion destabilization probably occurs by charge neutralization, carried out jointly by the polynuclear species and by positively charged aluminum hydroxide. This sorption mechanism is likely the primary coagulation mechanism during the reactive stage. The formation of aluminum hydroxide and/or oxide during the stabilization stage may also take place, which suggests the gradual change of the dominant removal mechanism to sweep flocculation. The mathematical model involved the three fundaments of electrocoagulation: Electrochemistry, coagulation and flotation. By comparing the experimental values of COD with those calculated by the model it was found that the model was able to adequately predict the concentrations of organic matter (COD) present in the emulsions and satisfactorily describe the electrocoagulation process.

Production of Titanium by Electrorefining of Titanium OxycarbideDaniel Jewell (a), Michael Kurtanjek (b), Derek Fray (a)(a) Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ(b) White Mountain Titanium Corporation, Augusto Leguia 100, Oficina 812, Santiago, ChileContinuing global developments in all areas of society have produced an insatiable demand for materials with superior characteristics for use in ever more challenging environments. These needs have predominantly been met by the development of new materials with novel structures or compositions, e. G. CNTs and high-performance alloys. An alternative approach is to improve the production of existing materials which already possess the desired properties but which cannot currently be economically produced; Titanium is one such material. Titanium is highly desirable as a result of its exceptional combination of outstanding properties which meet the exacting requirements of many demanding applications. Unfortunately, the difficulty of extracting the pure metal from its ores has prevented its widespread use, and for more than a century an efficient electro-extractive process has been sought. In 2000, the publication of the FFC-Cambridge Process[1] re-ignited the dream of low-cost titanium, but despite significant investment for over a decade, operation of the process at the industrial scale has, to date, eluded the industry. Recently, a novel electro-refining method[2-4] has arisen as a potential alternative route to cheap, large-scale titanium production and is currently under investigation at the University of Cambridge. This method, called the Chinuka Process, uses a titanium oxycarbide anode, produced by carbothermic reduction of titanium ores, and gives a purified titanium deposit on the cathode. Advantageously, the process can be applied to refine lower grade ores that contain impurity levels far above the specifications required for other titanium extraction processes. The results of recent work on the Chinuka Process at the University of Cambridge will be presented, detailing oxycarbide production, process operation and parameters, cathodic purity, and current efficiency. Analysis will include XRD, SEM/EDX, IGFA, ICP, and XRF measurements. Current challenges and scale-up will also be discussed. References:1. Chen, G. Z., Fray, D. J., and Farthing, T. W., Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature, 2000. 407: P. 361 - 364.2. Fray, D. J. And Jiao, S., Treatment of Titanium Ores. WO 2011/015845 A2 (2011)3. Jiao, S. And Zhu, H., Electrolysis of Ti2CO solid solution prepared by TiC and TiO2. Journal of Alloys and Compounds, 2007. 438: P. 243 - 246.4. Martinez, A. M., Osen, K. S., Skybakmoen, E., Kjos, O. S., Haarberg, G. M., and Dring, K., New Method for Low-Cost Titanium Production. Key Engineering Materials, 2010. 436 (Cost-Affordable Titanium III): P. 41 - 53.

Pulse Electrotechnologies (named also "Pulsed Power") are the major direction of development of various manufactures of XXI centuries. One of "Pulsed Power" directions is an influence on materials of superstrong electromagnetic fields. As an example is no thermal action of strong electric fields on medical, biologic and natural mineral objects. In Russia, like elsewhere in the world, development of primary gold deposits is considered a first-priority line of development for gold mining industry. Most of the gold-containing ores characteristic of Russian gold deposits are resistant ores with gold content varying between 3 and 5 ppm, usually showing quite low gold and silver recovery by cyanidation. Processing resistance of gold-containing mineral complexes is related to the presence of gold particles of submicrometric (< 1.0 mkm) and nanometric size (~10-100 nm), mostly associated with pyrite and arsenopyrite. Let’s review some kinds of known technique of natural media modifications, which are closely related to the method proposed in this paper. The electrochemical methods should be mentioned first. The essence of these methods consists in the increase of defects concentration and arising of a great number of microcracks under the polarization processes of sulfide and oxide minerals with semiconductor properties. The defects concentration raise and microcracks emergence are caused under these conditions by the electrochemical reactions which take place on the mineral grain boundaries. In practice, the electrochemical action is performed in the process of grinding by the application of direct current of 3-6 A/m2 density and of 6-12 V voltage inside the ball mill. The electric power consumption in this case amounts to 0.2-0.4 kWh/ton and the degree of disclosure increases by 20-25%. Considerably better results were obtained under the ores exposure to the accelerated electron beam with energy of 1-2 MeV and current density of 1-5 mkA/cm2 before grinding. The physical background of the effect is the electric charge of the natural media of weak conductivity. This causes the emergence of microcracks, which lead to the softening of mineral components. The 20-80% increase of grinding efficiency, as well as the 15-20% raise of technological characteristics is observed under these conditions for all types of ores. Noteworthy that the most complicated technological process is the disintegration process of so called resistant ores and beneficiation products. For example, 50-60% of noble metals contained in the raw material cannot be extracted in spite of the increased fineness of grinding. One of the noteworthy attempts to solve this problem was the irradiation of the ore by the microwave generator. The microwave generator provided a continuous radiation of 0.9-2.5 GHz frequency. The roast of the medium up to 360 oC increased the yield of gold in several experiments but no convincing results were obtained. In UHF treatment, heterogeneous (non-uniform) absorption of microwave energy by different components of the mineral complex results in embrittlement of the mineral matrix and destruction of its skeleton along the intergrowth boundaries, which "unseals" the valuable components, making them easier to extract. In addition, intense physicochemical processes occur on the surfaces of the sulphide samples exposed to UHF treatment: Pyrite oxidizes to hematite and elemental sulphur, and arsenopyrite oxidizes to magnetite, arsenic sulphide and (minor) SO2, which helps increase gold recovery up to 95%. However, excessive UHP heating results in unwanted effects, such as fusion and sintering of the material and closure of as-formed cracks. In addition, this procedure is energy-intensive, with energy consumption of at least 3-5 kWh per ton required to provide for plant capacity of 5-10 tons per day. Magnetic pulse treatment of gold-containing ores is meant to reduce energy expenditure for milling and increase gold recovery. This technique is realized by passing the ore (or pulp) through a dielectric pipeline segment enclosed in a system of electromagnetic coils which, constantly generates electromagnetic field pulses with repetition frequency up to 50 Hz. It is worthwhile to implement this technique in ore processing just before milling and to include it in the cyanidatlon procedure, which proves to yield a 1-1.5% gain in gold recovery in all. A group of researchers affiliated in the Electrophysical Institute of the Uralian Branch of Russian Academy of Sciences (Yekaterinburgh) designed a plant for electrohydraulic treatment of resistant materials by nanosecond pulses with a positive polarity, a magnitude of up to 250 kV, and a repetition rate of up to 300 Hz. This device does perform the mechanism of nanosecond breakdown of water (the electrohydraulic method proposed by L. A. Yutkin) with suspended microparticles, yet having significant limitations on efficiency, capacity and energy consumption, and some other technological restrictions. In essence, electrohydraulic treatment is realized through exposing the test material immersed in liquid, to shock waves generated by electrical breakdown of the liquid, with an aim to destruct the resistant particles. The essential disadvantages of this method are the necessity of performing the process in a liquid medium with solid-to-liquid ratio S: L=1:1, which decreases plant capacity and increases energy consumption, and non-controllable changes in ionic composition of the aqueous phase of the pulp. In particular, experiments with samples of stale tailings from the Uchala concentration plant revealed a sizable increase in concentration of Cu, Zn and Fe ions in the aqueous phase of the pulp after electrohydraulic pulse treatment, which may disturb further processing and have negative environmental sequels. All the above discussed high-energy treatment methods have the following disadvantages in common: High energy consumption, overheating of the material subject to processing, and certain intensification of sulphide leaching with uncontrollable passage of metal ions into the liquid pulp phase. In this report we present a treatment method developed by IPKON RAS (Moscow) researchers in collaboration with specialists from number of other organizations, which appears to be free of the above listed disadvantages. This non-traditional, highly efficient and environmentally safe method of breaking up mineral complexes with disseminated fine gold is based en non-thermal action of nanosecond High-Power Electromagnetic Pulses (HPEMP) on resistant gold-(PGM)containing ores and beneficiation products. The application of HPEMP irradiation in dressing of resistant gold-containing ores appears attractive as this technique provides for a significant increase in precious metal recovery (30-80% for gold and 20-50% for silver), therewith helping reduce both energy consumption and the cost of products, as shown in previous works. This study deals with three plausible mechanisms of disintegration of fine disseminated mineral complexes under the action of nanosecond HPEMP with high electric field strength Ep ~10(7) V/m. The first mechanism consists in loosening of the mineral structure due to electrical breakdown effects, which only occurs in cases where small, highly conductive inclusions are hosted in dielectric media. The second mechanism is related to development of thermomechanical stresses at the boundary (interface) between the dielectric and conductive mineral components. The third mechanism, assuming essentially non-thermal action of HPEMP on mineral complexes, is related to electromagnetic energy absorption by thin metallic films or layers much thinner than the characteristic skin layer. Results of experimental studies of the mechanisms of non-thermal action of HPEMP with nanosecond leading edge and pulse duration and high electric field strength on complex natural mineral media are presented. Experimental data are presented to confirm the formation of breakdown channels and selective disintegration of mineral complexes as a result of pulse irradiation, which makes for efficient access of lixiviant solutions to precious metal grains and enhanced precious metal recovery into lixivia during leaching. We studied the influence of HPEMP on the technological properties of particles of refractory gold- and silver-containing ores and beneficiation products from Russian deposits. Preliminary processing of gravity concentrate of one deposit ore with a series of HPEMP resulted in significant increase of gold and silver extraction into lixivia during the cyanidation stage, with gold recovery increased by ~31% (from 51.2% in a blank test to 82.3% after irradiation) and silver recovery increased by 47% (from 21.8% to 68.8%). Gold recovery from stale gold-containing dressing tailings increased after pulses-irradiation from 6.3-52.6 % to 43-91 %. Several series of tests performed in IPKON RAS tougether with Minning and Metallurgical Center of the Zapolyarnyi Affiliate of "Norilsk Nickel" Corporation yielded an absolute gain in noble metals recovery from the beneficiation products of disseminated copper-nickel ores, up to 75% for gold and 52-67% for platinum-group metals, with resultant gold recovery as high as 88.3% and with resultant palladium recovery as high as 70% and resultant platinum recovery as high as 82%. In this case the desired technological effect has been achieved due to use of a preliminary HPEMP-irradiation and the subsequent comminution during 15 minutes and specific gravity processing in the "Knelson" centrifugal concentrator.

The electroplating industry generates annually huge of sludge that contain an important concentration of heavy metals, therefore, requires disposal, treatment or appropriate destruction of such hazardous wastes. In this work, we evaluated the concentration and recovery of nickel and chromium from sludges generated for automotive industry and pickling parts. For this an electrochemical-electrokinetic reactor has been implemented. NH4Cl was used as electrolyte and it was demonstrated that this species favors de selective separation of nickel and chromium. The separation and concentration of each metal seems to be an alternative for the treatment of industrial sludge, not only for the economical values, but for the reduction of metals content in these hazardous materials.

Aluminum alloy tank, wrapped with CFRP (Carbon Fiber Reinforced Plastic) is mounted in a new fuel-cell car. Since such tanks are manufactured using a forming method, cracks are easily formed inside the tank, shortening its life period. However, it is difficult to polish the inner surface of aluminum alloy tank; Therefore, the effective inner polishing method has not been introduced yet. This research is aimed to improve durable years of hydrogen tanks applying Electrochemical Chemical Mechanical Polishing (E-CMP) technology to remove such cracks of aluminum alloy. This paper presents initial results of our continuing investigations on the processing properties of E-CMP for aluminum alloy.

The oxidized copper ore from Canaã dos Carajás has been stocked since the beginning of the extraction of copper sulfide ore, which is concentrated up to a 30 % content through flotation and negotiated by Vale Company. Lately, the application of heap leaching and leaching under pressure in autoclaves for copper recovery has been studied for both copper oxide and copper sulfide. Wishing to study the behavior of the oxidized ore by leaching with sulfuric acid, tests in laboratory scale have been realized and, through those, important data, such as concentration, liquid-solid relation, and time of contact, have been collected for optimizing the process. And also data such as: Influence of the mixer rotation, and of granulometry, as well as the determination of the isotherm of equilibrium, number of probable stages by the method of McCabe and Thielle and the mathematic model of kinetics and extraction. In the presentation of this work the methods utilized in the tests and the obtained results are shown. For such tests samples of two different types of ore were used; Those ores have medium contents and are often found in the mine. These data will serve for future tests in heap leaching and column leaching of the same ore.

Corrosion damage is commonly observed in a wide range of aluminum alloys and structural steels that are being used for aerospace and naval structural applications. Corrosion generally involves the formation of pits, pit growth, and nucleation of cracks from pits. There is no sensor or probe available in the literature that can measure stresses around pits in order predict the nucleation of cracks. The objective of this study is to investigate the stresses induced by corrosion pits in aluminum alloys and structural steel, and analyze the stresses under different loading conditions. Corrosion experiments were carried out on aluminum alloy samples and imaged through Atomic Force Microscopy (AFM) to obtain the pit profiles and to investigate the correlation between pits and stresses. An analysis procedure was developed using CAD and finite element analysis to predict stresses resulting from corrosion pits. Based on the analysis, it was observed that the stress distribution and levels on the corroded surface varied due to irregularity in the corrosion process. The results obtained indicate that the stress initially increases and reaches a plateau with increasing corrosion time and the stress magnitudes are different in aluminum alloys in comparison to structural steel. From these stresses it is possible to estimate the initiation of cracks, from which the failure life can be estimated. The results of stress analysis and their relation to corrosion degradation will be discussed in the presentation.

Nechvoglod O. V., Selivanov E. N., Mamjachenkov S. V. An alternative way for the extraction of copper and nickel from sulphide intermediate products is an electrochemical processing of granular sulfide-metal alloys. The method is excluded the formation of sulfur dioxide. The granulated matte processing technology with the ratio Cu / Ni = 2 has offered by electrochemical method. It includes granulating copper-nickel matte, electrolysis to produce copper powder, cleaning solutions, electrochemical nickel powder obtain, washing elemental sulfur from the slurry. Preparation of copper-nickel matte to an electrochemical dissolution by means of granulating method allows to be obtain ultrafine granulation structure which increases the rate of electrochemical oxidation and provides a greater reaction surface of the material. The method of anodic dissolution of sulfide alloys is enable matte processing at a wide range of the ratio Cu / Ni. The basic element of technology is electrolysis conducted at the anode current density of 25 A/m2, cathode - 400 A/m2 and voltage on the cell 2.5 V. The electrolysis is accompanied by a transition of copper, nickel, iron and cobalt in the solution, the formation of copper powder and the anode slurry containing sulfur in elemental form. The proposed method can be used for processing nickel matte and matte white.

The present work proposed a novel process route towards the extraction of metal values from slag, low-grade ores and other oxidic materials such as spent refractories by using molten salts. The thermodynamic principles and feasibility of this process were proved by both theoretical thermodynamic studies and experimental Cyclic Voltammetric studies. Preliminary experimental investigations were also carried out on the extraction of CrFe alloy from industrial EAF slag and chromite ore, and extraction of Cu/Fe values from CuO, Cu2S and CuFeS2, and results are very promising, which showed that the metal values can be extracted by using this process. Industrial possibilities and improvements were also discussed in the present work.

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