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By S. Kurama

Incorporation of de-watering sieve waste of borax (TSW) from Etibor Kirka Borax Company (Turkey) on the mechanical and physical properties of a commercial floor tile composition was investigated. In order to achieve this aim, TSW was partially employed in place of feldspar in the standard composition up to 20 wt %. The formulated compositions were wet milled, dried, shaped and then fired at 1190C for a total firing time of 38 minutes (from cold to cold) under industrial conditions. It was found that using of TSW up to 15 wt % improved the physical and mechanical properties of final product. The results indicated a good prospect for TSW as a co-flux in floor tile formulations.

Jan 1, 2006

By J. Michael Canty

Over 25 years of US research in Mineral Recovery from Geothermal Solutions have lead to few commercial applications. With the World Bank program in Kamchatka, Russia in September 2005 a step was taken to vitalize and coordinate the many efforts to advance economic mineral recovery systems worldwide. The US Department of Energy is helping to spur on the interest and research needed to realize the many benefits of extracting minerals from geothermal solutions. The excitement of recovery of minerals from geothermal brines has many positive angles. The economics of certain geothermal site is improved if a revenue is arrived from a sellable commodity with the geothermal power. The use of cleaner geothermal brines also improves the capable use of the brine before reinjection. We will review the history of Geothermal in the USA and the opportunities for recovery of different minerals and the markets for them.

Jan 1, 2006

By Michael S. Moats, Alexander Derrick

"The Winand Diagram was developed and has been used for decades to illustrate the interaction between polarization, mass transport and inhibition on the resulting structure of a metal electrodeposit. Recently, Adcock et al. criticized the Winand Diagram and developed their own structural diagram based on nucleation and plating overpotentials. Their work was based on zinc electrodeposition using a galvanostatic staircase method. This work explores the nucleation and plating overpotentials for copper electrodeposition using conditions typical for primary electrowinning and the galvanostatic staircase experimental technique. Additionally, the effects of organic additives and plating substrate on these overpotentials are reported.IntroductionThe control of electrodeposited structures is critically important to modem electrometallurgy operations to insure proper quality and efficient energy use. Electrodeposition of base metals for primary recovery (e.g. electrowinning or electrorefining), while similar to plating for decorative or device manufacturing, differs in the need to produce deposits that cover large areas and grow to significant thickness. Thus, controlling nucleation and particularly growth of electrodeposits is critically important for base metal electrometallurgical operations.The control of nucleation and growth on an industrial scale is most influenced by five parameters - current density, temperature, metal concentration, electrolyte agitation and additives. The effects of these parameters on electrodeposition are interrelated. To describe their effects on the type ofelectrodeposits generated and provide practitioners with a useful tool, Winand developed what is known as the Winand Diagram [1-2]. An adapted version of the Winand Diagram is shown in Figure 1.Winand characterized electrodeposits using Fischer's classification [3] and plotted the various deposit types versus inhibition on a vertical axis and the ratio of current density to bulk metal concentration on the horizontal axis. Inhibition intensity is a complex parameter and is still not well understood even though Fischer introduced the term in 1960 [4]. Often, inhibition intensity is simplified to equal the concentration of organic additive at the deposit surface and is related to the inverse of the exchange current density of the metal being deposited. The ratio of current density to bulk metal concentration is used to represent the ratio of crystallization overvoltage to mass transport of the depositing ion. As such i/iL could also be along the horizontal axis, where iL is the limiting current density of the electrodeposition reaction."

Jan 1, 2012

By Tong Deng

Clean processing of copper converter slags for reclaiming cobalt and copper could be a challenge. An innovative and environmentally benign approach for recovering metal values from such a slag was developed in the present work. Curing the slag with sulfuric acid, without re-smelting or roasting as currently practiced in the industry, made it amenable to leaching, and more than 95% of the cobalt and up to 90% of the copper was extracted, together with iron, by water leaching, leaving silica behind in a residue. Copper in the leach liquor was recovered by cementation with iron, and the dissolved iron crystallized as ferrous sulfate monohydrate. Cobalt in the pregnant solution rich in iron was recovered by either cementation or sulfide precipitation. Chemical and mineralogical characterization of the slag and its products were examined and compared to determine the nature of the changes occurring during curing and leaching. Operating variables were also investigated and optimized.

Jan 1, 2003

By Partha Patra

Extracellular bacterial protein (EBP) from Paenibacillus polymyxa was isolated. Adsorption of bacterial cells of Paenibacillus polymyxa as well as EBP onto pyrite, galena and sphalerite was studied. Both bacterial cells and EBP was found to have different adsorption density for different minerals. Protein from mineral surfaces were extrated and examined through SDS PAGE electrophoresis. Specific group of protein was found to be adsorbing, specific to respective minerals. EBP was fractionated through FPLC. Adsorption studies were carried out with each fractions. Difference in adsorption density was observed for individual minerals. Flocculation and flotation experiment were carried out with these mineral specific EBP. Pyrite was selectively removed from ternary mixture of galena and spharite through flocculation anf flotation using pyrite specific EBP. Mineral specific EBP was found to selectively separated remove pyrite from the complex sulphide mixture.Zetapotential studies were carried out to examine the surface chemical changes of the minerals on interaction with EBP. Hydrophobicity of the minerals were carried out on interaction with bacterial cells as well as mineral specific EBP.

Jan 1, 2006

By Brady Butler

Many high capacity metal hydrides exhibit a high degree of stability in the hydrogenated state. This stability leads to a number of significant design problems with regard to the low temperature kinetics and thermodynamics of dehydrogenation. Nanometric metal hydride materials provide a promising route for increasing the reaction kinetics while altering the thermodynamic stability of the material. The use of nanometric metal hydride materials for hydrogen storage has largely been absent because of the difficulties associated with the synthesis of these materials. In this paper, research results on the synthesis of lithium based metal hydrides by vapor phase reactions are presented. The lithium based compounds that have been made in our lab include nanosized powders of metallic Li, Li₃N, LiNH₂ and LiH. The vapor phase process has also been used to custom engineer Li-based materials with other alloying elements or doping elements. The dependence of the characteristics of these materials on synthesis process parameters is studied. The effects of nanoscaled particle sizes on the kinetics of dehydrogenation and hydrogenation reactions are also explored.

Jan 1, 2006

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 Elizabeth M. Ho

Oxidants are added in uranium leaching in acid media to convert iron(II) in solution to iron(III). Iron(III) has an important role in the leaching of uranium by acting as an electron transfer agent for the oxidation of uranium(IV) to uranium(VI). The oxidation of iron(II) to iron(III) in sulfate solutions using sulfur dioxide/oxygen (SO2/O2) was carried out under typical uranium leaching conditions (pH 1-2, 20-50°C) to confirm literature trends and this work was then extended to the use of SO2/O2 in the leaching of uranium ore. The oxidation rate was found to be dependent on the initial SO2/O2 volumetric ratio and the oxygen mass transfer rate, but was independent of the initial iron(III) concentration above about 200 ppm at pH 2. The presence of 55 ppm organic extractant (Alamine 336) decreased the reaction rate. The oxygen mass transfer coefficient (kLa) for the mixing tank system was measured and was found to decrease with increasing solids density in a 1 g L-1 MgSO4.7H2O solution.

Jan 1, 2003

By He De-wen

The increasing population and living standard in urban areas, have been accompanied with the growing quantity and composition complexity of rubbish, which are causing well-known social effects of pollution, while rubbish (solid waste) is a recyclable resource. To convert rubbish into useful materials, the essential measure is to carry out sorted collection of rubbish. The preconditions of implementing sorted collection are presented in the paper. 1 Characteristics of rubbish composition and amounts of recyclable contents are basic condition to implement sorted collection. 2 The existing available technologies of recycling, economic benefit from recycling, and disposal scheme of residual rubbish are restrained condition for sorted collection. 3 Public understanding and support to sorted collection are the key to success. 4 The government policies to be favorable for sorted collection is the pledge of success. 5 The establishment of a steady solid waste recycling market is also a guarantee to implement sorted collection continuously. 6 To establish management system of rubbish recycling as soon as possible. Further, the methods and procedure of sorted collection are discussed in detail and beneficial comments and theoretical basis to promote sorted collection of rubbish in urban area are presented; it will contribute reference value to municipal solid waste management.

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 A. V. Tarasov

In the course of research aimed at improving the performance of the Vanyukov smelting process (VP) for treating sulfur raw materials in a pilot-scale furnace it has been found that an increase in the calcium oxide content up to 12% to 14% in case of smelting to produce high-grade matte results in a decrease in the copper content of slag by 0.05% to 0.3%. The residual copper content of slag can be computed by a formula taking into account an increase in the calcium oxide content of the feed material and that in the slag. In the course of research for improving the performance of the zinc-containing slag fuming process with blowing of the slag bath with combustion products of natural gas it has been found that the silica and calcium oxide contents have an effect on the degree of zinc sublimation. In case of slag containing 24.4% SiO₂ and 6.95% CaO by weight (SiO₂:CaO = 3.51), the residual zinc content of slag was 3.25%. The minimum residual zinc content of 1.95% was obtained in case of slag containing 22.5% SiO₂ and 14.5% CaO by weight (SiO₂:CaO = 1.55). An increase in the CaO content of slag up to 16% by weight with a ratio of SiO₂:CaO = 1.25 to 1.35 permits minimization of zinc losses in slag by achieving a residual zinc content of final slag in the order of 1%.

Jan 1, 2006

By K. Verbeken, E. Wettinck, M. Verhaege

Iron (III) can easily and selectively be removed from acidic sulphate solutions with organo-phosphoric acids like Di-2-Ethyl-Hexyl-Phosphoric Acid [D2EHPA]. Stripping of the iron (III) loaded organic, however, is difficult unless highly concentrated inorganic acid solutions are used. In this paper results are shown for the enhanced stripping of iron from loaded D2EHPA by electro-reduction. The loaded solvent is contacted with a 2 M H2SO4 solution, which is continuously recycled in an electrochemical reactor where iron (III) is reduced to iron(II). As iron (II) is not extracted by D2EHPA, the equilibrium for iron (III)- D2EHPA is shifted towards the aqueous iron (Il)-sulphuric acid solution. The electro-reduction unit is a vessel with separated catholyte and anolyte chambers. The catholyte is the actual stripping solution where iron (III) is reduced to iron (II) on a stainless steel electrode. The anolyte is a 2 M H2SO4 solution where oxygen is evolved on a lead alloy electrode. A sintered glass plug separates the compartments. With this unit, enhanced stripping of iron from the solvent is possible under mild acid conditions [2 M H2SO4], and a concentrated ferrous sulphate solution can be obtained. The results shown have mainly been obtained by studying the parameters affecting the electro-reductive stripping of a D2EHPA loaded organic phase in a batch reactor. From an iron (IH)-saturated 20 vol. % D2EHPA solvent containing ~ 12.5 g/1 Fe (III) over 90% of the iron can be stripped in one stage with a 2 M H2SO4 solution at 50°C. It is shown that in this way it should be possible to obtain a concentrated ferrous sulphate solution which can be processed downstream to recover a pure iron product.

Jan 1, 2000

By Asok Kumar Das

"In steel making ferroalloys occupies a commanding role for production of varied quality of steel. Ferroalloys enable alloying elements such as chromium, silicon, manganese, vanadium etc to be safely and economically introduced into metallurgical processes thus giving certain desirable properties of the alloyed metal. Their importance grew with the progress of the steel metallurgy which implied more diversified alloying elements, in better controlled quantities, in purer steel. The ferroalloy industry became a key supplier to the steel industry. Production of ferroalloys generally involves the use of Electric Arc furnace(EAF) into which raw materials(e.g. various metal ores, quartz, coke, lime etc ) with relatively fluctuating physical compositions are loaded. Due to this, one of the major environmental impacts of producing ferroalloys is the emission of dust and fume from the smelting process. INTRODUCTIONFerro Alloys are essential ingredients used for refining, de-oxidation, desulphurization and alloying addition in the production of different types of steel and hence Ferro Alloy industry forms a back bone of iron and steel in the world. Indian ferro alloy industry is more than 45 years old. It produces most of the bulk ferro alloys and a large number of special ferro alloys. The present installed capacity of the Indian ferro alloy industry is sufficient to meet the requirement of existing level of indigenous steel production of about 46 million tonnes. Revised National Steel Policy – 2008 envisages production of more than 100 million tonnes of steel by the year 2011-12, at proportionate annual growth rate per annum. The focus of the policy is to achieve global competitiveness not only in terms of cost, quality and product-mix but also in terms of global benchmarks of efficiency and productivity. In order to achieve the objectives of National Steel Policy and also to meet the requirement of ferro alloys, the Indian Ferro Alloy Industry has to gear up in terms of enhancement in production capacity, sourcing of raw materials, up gradation of technology, improvement in productivity, automation / mechanization, customer satisfaction etc."

Jan 1, 2008

By M. G. King

In 1982, Asarco operated six smelters and refineries producing primary copper, lead, zinc, silver and gold. At that time Asarco was still reliant on its custom smelting and refining roots and mined only 25% of its smelting and refining capacity for copper and 10% of its lead smelting and refining capacity. By 1992, Asarco had been reshaped to become largely an integrated primary metal producer operating four smelters and three refineries. Zinc is no longer refined and the mining capacity has been increased to meet 100% of copper smelting and 50% of lead smelting needs. Only one custom smelter is in operation. This paper describes the metallurgical changes and challenges which have occurred in this restructuring of Asarco&apos;s operations while maintaining Asarco&apos;s position as one of the largest non-ferrous metals producers in the world.

Jan 1, 1993

By A. L. Davies

The MTDATA computer software package consists of a rigorous implementation of an algorithm for calculating chemical phase equilibria by the technique of Gibbs free energy minimization and a database of the thermochemical properties of common materials, such as slags, mattes, metals, gases and aqueous solutions. We have used MTDATA to contribute to our understanding of the chemical reactions occurring in several specific unit operations of the Kennecott Utah Copper Garfield Smelter. The following two examples illustrate the range of environments to which the method is applicable. Calculation of the liquidus phase relations of the FSF fayalite and FCF calcium ferrite slags helped in the early diagnosis of several operating problems. Calculation of the deportment of fluorine between the FSF offgas and the FSG scrubber liquor helped in the identification of operating conditions under which significant hydrogen fluoride concentrations could be introduced to the contact section of the acid plant. Without the painstaking assessment of solution phase properties undertaken over many years, these calculations would not be possible.

Jan 1, 1999

By Wen-Ming Chien, Vamsi Krishna Kamisetty, Amrita Mishra, Ivan Gantan, Prathyusha Mekala, Dhanesh Chandra

"The phase equilibrium and characterization studies by using high temperature X-ray diffraction (XRD) and differential scanning calorimetric (DSC) methods have been performed for binary organic thermal energy storage materials. The organic thermal energy storage materials undergo a solid-solid state phase transition before melting which stores large amounts of thermal energy. Two materials [tris(hydroxymethyl)aminomethane(TRIS) and 2-Amino-2-methyl-l, 3- propanediol(AMPL)] were used for this study. Binary samples of AMPL-TRIS were prepared to perform high temperature XRD characterization and DSC studies and the binary AMPL-TRIS phase diagram was developed. The high temperature solid-state phases of AMPL and TRIS were characterized as a disordered BCC structure. It was found there is virtually no solubility of TRIS in AMPL or vice versa below -75 °C. The maximum solubility of TRIS in AMPL is 11% TRIS at 75 °C. The eutectoid transformation was shown at 19%TRIS-81%AMPL composition and at a temperature of 75°C. Lattice expansion calculations on single phase of TRIS and AMPL have been performed.IntroductionThermal energy storage materials can store a large amount of heat due to the presence of thermal transitions from the orientationally ordered to disordered phases occurring before melting. These molecules (such as amine and alcohol derivatives of neopentane) can reorient as a whole about the central carbon atom to form orientationally disordered crystals (ODIC) and their spherical shape makes them reorient relatively easier. Thermal energy storage materials are becoming increasingly important as a renewable energy resource. These molecules undergo large changes in enthalpies at solid-solid transitions. The presence of these compounds with large enthalpy changes are identified as potential thermal energy materials and some of die applications are solar cell systems [1-3]. Binary mixtures have been found as a way to adjust the transition properties in addition to pure compounds [4]. Tris(hydroxyrnethyl)aminomethane (TRIS, C(CH2OH)3NH2) and AMPL, CH3C(CH2OH)2NH2) are two important thermal energy storage materials."

Jan 1, 2012

By Ditze A., C. Scharf

Magnesium type 1 - scrap can be remelted without flux in the presence of different sulfur containing protective gases. Beside the draw back in the use of these gases, that either are contributing to the global warming potential (SF6) or are poisonous (S02), residues like dross and crucible sludge are produced. Dross and sludge now a days must be utilized. Partly these byproducts can be used in the aluminum industry and partly for desulphurisation of hot metal and steel. Another possibility is melting of dross and sludge with flux for the production of a secondary magnesium alloy. Then again residues are generated that must be processed. Therefore, the whole material cycle has to be considered to decide which kind of utilization practice is optimum. Based on experiments this question is discussed and the material balances for fluxfree melting, melting with flux and fluxfree melting plus other utilization of the residues are presented.

Jan 1, 2000

By Rodney L. LeRoy, Michel G. Drouet, Peter G. Tsantrizos

"DROSRITE is a unique process that makes possible economic in-plant recovery of metal from hot aluminum dross. It is environmentally friendly, requiring no salt and producing no C02 or NOx gases. The salt-free residues of the process are suitable for production of calcium aluminate or for other value-added use. The process is highly energy efficient, extracting process heat from energy in the residue and, thus, it does not require an external plasma torch, electric arc or fuel heat source.A DROSRITE pilot unit built by PyroGenesis has been tested with both black and white dross types. The unit was installed at two different aluminum plant locations, and tests were conducted for a total of six weeks ""online"" with hot metal holding furnaces where the dross was skimmed.Results of both of these industrial trials are presented, together with an economic analysis indicating cost savings in excess of $1 70 per ton of dross treated."

Jan 1, 2000

By R. Chiarizia

Third phase formation, i.e., the splitting of the organic phase in two layers, is a common feature observed, under conditions of high loading, for many solvent extraction systems of both analytical and industrial interest. Although this phenomenon has been investigated in a large number of works, a structural and physico-chemical description is still lacking. In this work, small-angle neutron scattering (SANS) data for the tri-n-butylphosphate (TBP)-n-octane,Th(NO3)4-HNO3 solvent extraction system have been interpreted using the Baxter model for hard-spheres with surface adhesion. The increase in scattering intensity in the low Q range, observed when increasing amounts of HNO3 and/or Th(NO3)4 are introduced into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules plus solutes in their polar core. This intermicellar attraction, under appropriate conditions, leads to third phase formation.

Jan 1, 2003

By Guo Xueyi

The reaction mechanism for the manganese dioxide reductive dissolution in acidic chloride media in the presence of ferrous/ferric ions are based on theoretical delineation and dual cell experiments. In terms of the Buttler-Volmer equation and chemical kinetic principles, a electrochemical kinetic equation was deduced, which successfully provided a theoretical basis for describing the role of Cl-, Fe2+, Fe3+ and H+ in solution, as well as their interrelationship in manganese dioxide reductive dissolution. Dual cell experimental studies indicate that the increases of Cl- and Fe2 in solution are helpful to accelerate the couple process; while, Fe3and Mn2+ hinder the coupled reaction to some degree. Higher acidity in solution is beneficial to the dissolution of MnO2. All the dual cell experimental results are consistent with the theoretical deduction. This study will be useful to understand the mechanism for the leaching of manganese nodules from the deep ocean, as well as the leaching of manganese dioxide ore from land.

Jan 1, 2003