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The kinetics of the oxidation of cyanide by manganese dioxide was studied using a rotation disc electrode system. The rate? of the half-cell reaction of cyanide oxidation is increased at higher hydroxide concentrations. An addition of copper up to 0.001 mole/l was found to enhance the diffusion current, especially at a high hydroxide concentration (0. 1M). A similar enhancement of the reaction rate is also achieved with nickel added at levels up to 0.01 mole/l. Manganese dioxide however requires a i:ow pH to achieve reasonable reduction rates. Leaching studies indicated that the initial reaction rate is strongly dependent on pH, initial concentration of cyanide. Using manganese dioxide cyanide could be oxidized at neutral pH's and ambient temperatures.

Jan 1, 1989

By Patrick M. Eduafo, Brajendra Mishra, Mark L. Strauss

Direct acid leaching of rare earth metals (REMs) from waste lamp phosphors is non-selective, leading to co-dissolution of impurities mainly calcium, phosphorus, silicon, iron and zinc. Calcining the phosphor powder at different temperatures followed by leaching with HCl isn’t efficient for the extraction of all the chief rare earths especially cerium (Ce), lanthanum (La) and terbium (Tb). Therefore, multi-stage leaching operations are required for the separation of the REMs in phosphor dust. This paper will outline a new process for extracting Ce, La, Tb, Eu and Y from waste fluorescent lamps using a three-stage leaching and separation process. A flowsheet has been developed which shows this process is selective and efficient.

Jan 1, 2015

By Pertti Koukkari, Nagendra Tripathi, Karri Penttilä, Justin Salminen

A computational fluid dynamic model for a novel flash ironmaking process based on the direct gaseous reduction of iron oxide concentrates is presented. The model solves the threedimensional governing equations including both gas-phase and gas-solid reaction kinetics. The turbulence-chemistry interaction in the gas-phase is modeled by the eddy dissipation concept incorporating chemical kinetics. The particle cloud model is used to track the particle phase in a Lagrangian framework. A nucleation and growth kinetics rate expression is adopted to calculate the reduction rate of magnetite concentrate particles. Benchmark experiments reported in the literature for a nonreacting swirling gas jet and a nonpremixed hydrogen jet flame were simulated for validation. The model predictions showed good agreement with measurements in terms of gas velocity, gas temperature and species concentrations. The relevance of the computational model for the analysis of a bench reactor operation and the design of an industrialpilot plant is discussed.

Jan 1, 2014

By Chang Wei, Zhigan Deng, Yizhao WANG, Cunxiong Li, Gang Fan, Xingbin Li

During the process of hematite precipitation, the transformation of Na jarosite convert into hematite has been studied in a batch reactor at different temperatures, ranging from 170°C to 200°C with 3h of the retention time in the presence of 30g/L Fe ( ) and 4g/L Na+. The composition of precipitation was seriously depended on the temperature, at 170°C hematite and sodium jarosite are the reaction products of iron precipitate, with an increasing in reaction temperature the sodium, sulfur content in precipitated decreased and sulfur mainly exist in forms of SO4 2-, and when temperature over 200°C hematite was the only phase in product. An increasing temperature was not only beneficial to iron precipitation, also conducive to jarosite conversion to form high quality hematite precipitate.

Jan 1, 2016

By K. R. Robilliard

An outline is given of the problems facing tlile lead and zinc industry from the viewpoint of the range of residues currently produced from electrolytic zinc, blast furnace and other processes. Smelting approaches available using top submerged lancing technology are discussed and analysed. Pilot plant results for a range of lead and zinc-bearing materials are presented.

Jan 1, 1992

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 Geir Wedde, Anders Sorhuus

"Vast quantities of energy are released as heat to the environment from industrial operations. Many countries target waste heat recovery to mitigate CO2 emission. Exhaust gases from industries such as primary aluminium smelting, carry a substantial portion of the waste heat generated. For a cost efficient capture of more valuable heat (higher exergy), heat exchangers should operate on the exhaust gases upstream of the gas treatment plants. Heat exchange surface would be exposed to dust laden gases with risk of fouling. Heat exchangers of innovated design and operation have overcome the potential of excessive fouling rates. Heat exchangers of the ""shell and tube"" design have been demonstrated for exhaust gases from ferroalloy as well as primary aluminium smelters. In addition to the heat recovery, gas cooling results in smaller gas treatment plants with lower costs and reduced emission. The aluminium experience is exampled in the paper.IntroductionIndustrial usage of energy continues to grow as a result of increasing volumes of production, a trend that is likely to continue in the coming decades as living standards keep rising globally. World energy consumption (Figure la) is to grow 49 % by 2035 (ref. 2010) as reported by EIA [1]. The industrial sector consumes somewhat more than 50% of the total world energy consumption predominantly the energy increased demand comes from non-OECD countries in Asia. The industrial consumption by production of metals iron and steel accounts for 14 % and for non-ferrous metals 3 % mostly for aluminium production (Figure lb). Aluminium production will be discussed in this paper as an example of an industry with large quantities of waste heat to recover"

Jan 1, 2012

By Leonid M. Lerner

High temperature aluminum Alloy 8009 is a rapidly solidified/powder metallurgy aluminum-iron-vanadium-silicon alloy. This alloy in combination with hard oxide aluminum film has unique engineering properties which may recommend its use in compressors and impellers for aerospace applications. Various anodizing processes (including Sanford Low Voltage DC+AC Process) for these task will be evaluated and normal chemical composition, physical properties, and macrostructures of 8XXX aluminum alloys will be presented.

Jan 1, 2006

Acid generation from reactive sulphide mineral tailings has become a major environmental problem in the mining industry. Initiation of chemical and biochemical oxidation reactions of the sulphide mineral leads to acid generation. A novel concept of safe disposal and utilization of reactive fine mill tailings is presented in this paper. The paper also presents the results of a preliminary laboratory experimental .study of the concept. The tailings are agglomerated using portland cement as a binder. The cold bonded agglomerates are encapsulated with other chemical additives to act as acid neutralizers, oxygen and ironoxidizing bactericides., The primary. factors influencing the choice of bacterfoides to inhibit the acid generating bacteria are their costs, toxicity and environmental friendliness. The paper discusses the utilization of agglomerated' products as aggregates for underground backfill, or as gravel for surface land cover.

Jan 1, 1991

By Wenliang Cao, Jidong Li, Mingjie Zhang, Yiyong Wang

In CaC12-CaF 2 System, we studied the electrode process and discharge mechanism of preparation of Al-Ca alloys by fused salt electrolysis with CaO as raw material. The change of back electromotive force after adding CaO was measured by continuous pulse oscillograph method and the discharge process mechanism was also investigated by cyclic voltammetry. The finial results indicate that back electromotive force decreases by 0.6V after CaO of 1 % is added and there was a peak of oxidation current ahead of the potential at which the negative chlorine ions precipitated. According to thermodynamic calculation, it was determined that current peak was caused by the CO2 produced by 0 2 - ionic discharge due to CaO addition.

Jan 1, 2014

By Leiv Kolbeinsen, Stian Seim, In-ho Jung

"The current work presents new experimental data in the iron-unsaturated region of the FeTiO3-Ti2O3-TiO2 slag system. The samples are prepared by melting pure reactants in a high frequency induction furnace that employs a cold crucible. A similar experimental set-up has been described in literature and proven suitable to investigate high titania slags. The FeO content of the samples range from 3.7 to 21.8 wt% and the Ti2O3 content range from 3.6 to 30.1 wt%. The liquidus temperatures of the samples are measured in-situ by a spectropyrometer and range from 1450 to 1645 °C.In addition, an improved thermodynamic database for the FeO-Ti2O3-TiO2 system has been developed. Ternary parameters have been included and optimized to fit previously published experimental data. This optimization minimizes the discrepancy between experimental data and thermodynamic calculations as previously discussed in literature. New liquidus projection plots are proposed for the FeO-Ti2O3-TiO2 and the FeTiO3-Ti2O3-TiO2 systems.IntroductionIlmenite (FeTiOs) smelting is a relatively small industry world-wide. However, a reasonable focus on the process has been applied in Norway due to the location of one such smelter in Tyssedal, which is located in the western part of Norway. The process is essentially carbothermal reduction, where most of the iron in the ilmenite is reduced to its metallic state, and the titanium oxide is concentrated in the slag product. The metallic iron is sold as a high purity pig iron and finds applications in cast products. The slag concentrate is further processed for the production of TiOvpigment and/or titanium metal. This further processing can be performed through different routes according to the purity of the slag concentrate."

Jan 1, 2012

By Jae-Ho. Lee

Mercury is a toxic contaminant encountered in the extraction of gold from mercury-containing ores. It is found in the leach solution of CIP circuits and in the cathodes of the electrolyte cells used to electrodeposit the gold. The research conducted has examined the potential for selective removal of mercury from synthetic Au-Hg-CN electrolytes containing only gold, only mercury, and both gold and mercury. Cyclic voltammograms were obtained for mercury- coated copper electrodes with these cyanide electrolytes. Exchange current densities were determined from the voltammograms in the low overpotential region. Laboratory scale batch- electrolysis at constant current was also conducted for the electrolytes containing only mercury and both mercury and gold, at 20 and 50°C and from which the kinetic behavior associated with the process was analyzed. The surface of cathode before and after electrolysis was also characterized and a copper mercury intermetallic (CyHg,) was identified. Gold codeposited with mercury during the later stages of electrolysis. The results of this work corroborate that the mercury-amalgam copper electrode offers a viable electrochemical technique for the selective removal of mercury, however a high-surface-area cathode-cell would have to be utilized to provide for the desired selectivity.

Jan 1, 1994

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for SO2 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as EI Teniente Converter and EI Teniente Slag Cleaning Furnace,

Jan 1, 2003

By Wei-feng Liu

On the basis of the brief introduction of the gold-antimony concentrate smelting process in China, some problems in the original process were analyzed and the corresponding improvements were introduced in this paper, such as the treatment of antimony matte, the refinement of gold-silver alloy, the concentrating gold from gold-antimony alloy, the treatment of soda slag. The roasting method that was used to treat the antimony matte was transferred to the ore dressing method. The solvent extraction was used to refine the gold-silver alloy instead of the electrolytic method. The technology of selective chlorination leaching under controlling potential was applied to concentrate gold from the gold-antimony alloy and gold-lead alloy instead of the electrolysis method. Soda slag was recovered by the second reducing smelting method substituting for the mixed-salt method of sodium arsenate. After those improvements, the process has been done smoothly; the direct recovery rate of metals has been greatly increased. Meanwhile the procedure

Jan 1, 2008

By Steven C. Torma

The present article reviews some of the technologies available for recycling high-energy yield explosives loaded projectiles. These activities lead to reduction of military ammunition stockpiles and their conversion into commercial and industrial applications. The recycling technologies involve dismantling and separation of ammunition components into recyclable metals, plastics, paper and explosive materials. The metal 1 ic components will be sent to smelters, where they will be converted to products that can be used in a variety of industries, such as construction, automotive, housing and so on. Plastics and paper will be recycled and reused. Explosives will be recycled to be used for industrial purposes in the mining industry. Propellants (ammonium nitrate and ammonium perchlorate) can be ground to small particle size and treated to be used in the agricultural industry as fertilizer. In addition, some of the excess explosive material recovered in the demilitarization process may be incinerated to produce energy for steam production for heating purposes, or for production of electricity. Furthermore, this article reviews the developments in the bioremediation of explosive contaminated soils and industrial effluents.

Jan 1, 1994

By Serdar Aksu, Fiona M. Doyle

"CMP will be an essential process in the production of integrated circuits containing copper interconnects. This study aims to improve our mechanistic understanding of the role that organic chelating agents might play in the reactive slurries used in copper CMP. Copper dissolution behavior in EDTA arid glycine was first examined by producing potential-pH diagrams for the copper-water-EDTA and copper-water-glycine 'systems. The results of potentiodynamic polarization experiments were then considered in light of these diagrams. . In-situ polarization experiments were conducted to gain insight into the electrochemistry of copper during dynamic polishing in slurries prepared from EDT A and glycine.IntroductionCopper has recently started to replace aluminum as the interconnect metal in integrated circuits. Copper interconnection offers faster and more reliable integrated circuits due to its higher electrical conductivity and superior electromigration resistance (1). The damascene method is used to form multilevel interconnects in the manufacture of integrated circuit devices with copper metallization (2, 3). Copper is deposited by CVD or electroplating into vias and trenches etched in the interlayer dielectric (IDL), over a diffusion barrier usually made from titanium, tantalum or their nitrides. Chemical mechanical planarization (CMP) then prepares the wafer for the next deposition step, by removing excess copper and planarizing the surface. During CMP, the wafer is rotated and pressed against a rotating platen covered with a polishing pad. Chemically active slurries containing submicron size abrasive particles (Si02, Al20 3, ceria, diamond, etc.) are applied. Both the mechanical action of the abrasive particles and the chemical action of slurry constituents remove material from the wafer surface. Planarization results because material is removed faster from protruding regions on the surface than from recessed regions. Since CMP can globally planarize .the entire wafer, it has become one of the key technologies for producing integrated circuits with copper metallization."

Jan 1, 2000

By Kandipati Sreenivasarao

Ion flotation is a promising separation process for continuously removing toxic metal ions from dilute process effluents. After treating the effluent with appropriate surfactant(s), the metal- bearing species adsorb onto the surface of rising gas bubbles and can be collected as foams. Suitable collectors have been identified for most of the elements of the periodic table. However, a better understanding of the thermodynamic, kinetic and engineering principles that determine the performance of ion flotation systems would facilitate commercial utilization of this technology. A model system of sodium dodecylsulfate-ethanol has been studied for the removal of Cu (11) from dilute solutions, using laboratory-scale flotation columns. This paper reports the effects of the air flow rate, solution height, foam drainage zone height and col1ector:metal ion ratio on the flotation kinetics, ultimate recovery of metal, flotation product grade, foam losses and effluent quality. Preliminary results for Pb (11) removal are also reported.

Jan 1, 1993

The generation of acid mine water is? due to the oxidation and weathering of sulfide bearing tailings and overburdens. Ferrite precipitation prooess has been applied to treat acid mine water. The conventional ferrite preC1pitatlon requires air oxidation at high temperature, or long aging time or addition of magnetite powder ,as promoter. In this investigation, a modified ferrite, precipitation process is developed by which magnetic ferrite can be produced at an ambient temperature. Acid mine waters from Berkeley Pit (Montana, U. S. A.) and from Noranda Tailings (Quebec, Canada) were used. The co precipitation of heavy metals from these two acid mine waters is studied as a function of FeIM molar ratio, oxidation time and settling rate under applied magnetic field. The investigation indicates that the modified ferrite co precipitation can remove substantially all of the, dissolved metal ions from acid mine water. The ferrite product obtained after precipitation' is characterized by XRD, SEM, BET and saturation magnetization. The results show that spinel ferrite, precipitation can be achieved at room temperature and the saturation magnetization of ferrite product from,acid mine water is comparable to that of pure ferrites.

Jan 1, 1995

By W. G. Davenport

All Outokumpu flash furnaces burn some hydrocarbon fuel. Hydrocarbon combustion supplements heat from Fe and S oxidation and provides local heating in cool; parts of the furnace. Adjustment of hydrocarbon fuel combustion rate is an effective way of controlling furnace temperature. More oxygen and more oxidation of Fe?and S in the flash furnace continue to diminish the need for1hydrocarbon fuel. Still, as Tables 2.1 and 3.1 show, all flash furnaces use it. Oil is the most common fuel -natural gas, coal and coke are also used. This chapter demonstrates how hydrocarbon fuel is included in our flash furnace matrix. It shows that: (a) three new variables, mass hydrocarbonfoel. mass CO2 in offgas and mass H2O in offgas are inserted (b) carbon and hydrogen balances are added (c) hydrocarbon fuel quantity is specified (d) ,the oxygen balance is modified to include CO2 and H2O (e) the enthalpy balance is modified to include hydrocarbon fuel, CO2 and H20.

Jan 1, 2001

New method for processing of copper and nickel production feed has been developed and tested at pilot unit having 10 t/hr capacity. The process allows single-stage treatment of ore feed including that with high magnesium oxide content and resulting in the production of rich matte, high-grade matte, or moralised alloy for further leaching, as well as dump slag and off-gasses suitable for production of elemental sulphur, liquid sulphur dioxide, or sulphuric acid. Tests results and principal technical and economical parameters are presented.

Jan 1, 2006