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By S. Agatzini-Leonardou

The objective of this work was to prove repeated loading capacities and investigate the selectivity of physically stabilized algal biomass from Spirulina platensis and Chlorella sp. for the removal and recovery of cobalt, nickel and chromium from laterite heap leach liquors. The testwork was carried out on a bench scale in small glass columns and proved that it was possible to immobilize the biomass on the highly porous surface of pumice stone (kissiris). Nickel and cobalt could be removed from pure aqueous solutions of each metal by the immobilized cyanobacterial biomass. Nickel and also cobalt biosorption was sensitive to the initial solution pH. Cobalt recoveries up to 80% were achieved after 5 loading cycles, from low concentration solutions, at pH 6.0. Nickel removal was complete under the same conditions, whereas chromium sorption was ineffective. Desorption of the metal loaded columns was effected by dilute sulfuric acid. The algal species giving the best adsorption capacities for the metals under consideration was selected for further experimental work with real laterite heap leach solution produced by column leaching. A statistical analysis of all obtained results was conducted using the fraction of metal removed as response. The ratio "mass of metal removed to mass of protein contained in the immobilized cells" was determined as well. The described method might be applicable for recovery of cobalt and nickel from diluted laterite heap leach solutions, such as heap wash waters, or for their removal from waste streams of a hydrometallurgical extraction process.

Jan 1, 1997

By C. B. Piazzarollo

Red Ceramic materials are widely used in Civil Construction in Tropical Countries. However, these materials have high porosity and low mechanical strength. Thus, in order to improve these properties, recycle mineral wastes was incorporated into clay from Campos - RJ, ornamental rock waste, from the gneisses cutting of Cachoeiro - ES, 150 km from Campos. After the addition of up 10% of waste in clay mass, ceramic pieces were produced and subjected to the tests of porosity (P) and flexural strength (FS). The test material contains 53.3% clay and 67% waste slit. The X-ray diffraction identified the presence of kaolinite, quartz and feldspar for the clay and, for the waste, quartz and orthoclase. The results of FS and P showed that the residue influenced, positively, the ceramic piece, with strength gains especially from 920º up to 960°C.

Jan 1, 2015

By Christopher B. Vierrether

Reflected light microscopy, scanning electron microscopy, and electron microprobe analysis have been used to determine the mineralogy, phase percentages, grain sizes, textures, and partitioning of cobalt and nickel in two cobalt-nickel rich mattes. These mattes were prepared by submerged bath smelting from a flotation cobalt-nickel concentrate containing 4.8% cobalt and 5.1% nickel. The concentrate was derived from lead-zinc-copper ores of the Viburnum Trend, southeast Missouri. Eleven discrete phases have been distinguished in the matte samples, three of which contain significant cobalt and nickel. The phases are cobaltpentlandite ((Co,Ni,Fe)9S8), cobalt-bearing marmatite ((Co,Fe,Zn)S), shandite (Ni3Pb2S2), bornite (Cu5FeS4), galena (PbS), magnetite (Fe3O4), pyrrhotite ((Co,Ni,Cu,Fe)1_xS), chalcocite (Cu2S), CuPbS phase, metallic copper, and metallic silver. Cobaltpentlandite and cobalt-bearing marmatite- occur in coarse grains (50 µm) that would separate readily during grinding, but shandite contains small (5 - 10um), abundant inclusions of pyrrhotite and bornite.. Some mineralogical variations between the two matte samples were due to differing degrees of oxidation during smelting,

Jan 1, 1988

By Muammer Kaya, Sait Kursunoglu

"The aim of this study was to investigate the effectiveness of ascorbic (C6H8O6) / oxalic (C2H2O4) acid as a reductant for the simultaneous recovery of zinc and manganese from a spent and mixed zinc-carbon and alkaline battery powder in sulphuric acid leaching. The effects of sulfuric acid concentration, ascorbic/oxalic acid dosages, reaction temperature and leaching time on the zinc and manganese dissolutions were investigated according to 2k full factorial experimental design; then, a simple optimization study was carried out for the best reductant. The optimum reductive acid leaching conditions were determined at 3 hours leaching time, 70°C leaching temperature, 0.5M sulfuric acid concentration, 13 g/L ascorbic acid dosage, 1/20 g/mL solid/liquid ratio and 200 rpm stirring speed. Under these conditions, the dissolution efficiencies were 99.9% for Zn and 99.3% for Mn. When our results were compared with the previous results, our findings were better than previous studies.In addition, the manganese dissolution kinetics was undertaken, and the activation energy was found to be 7.04 kJ/mol. Selective precipitations of Zn and Mn from acid solutions were carried out using NaOH and KOH. Using 3M NaOH as precipitating agent at room temperature and at pH 8; 95.4% of Zn and at pH 10; 93.7% of Mn were precipitated from the leaching solution. Under the same conditions, using 3 M KOH at pH 8; 91.6% of Zn and at pH 10, 96.4% of Mn were precipitated. Based on the experimental results obtained, an appropriate flow sheet was proposed to recover zinc and manganese."

Jan 1, 2012

By Kafui Nyavor

Acid mine drainage (AMD) is presently the biggest single environmental problem facing the mining industry. New and expanding metal mines in most parts of the world have to demonstrate their ability to contain this problem to obtain operating permits. Conventional methods of controlling acid mine drainage have primarily been limited to collecting the drainage and neutralizing with alkaline materials which do not provide a permanent solution to the AMD problem. Since acid mine drainage results from the oxidation of sulfides in the presence of oxygen, water and iron-oxidizing bacteria, controlling any of these three factors contributing to pyrite oxidation provides a potential at-source remedy for reducing or preventing acid mine drainage formation. Physical properties such as hydrophobicity also play an important role in the attachment of bacteria, adsorption of oxygen, water, and other ions that subsequently lead to the oxidation of pyrite. In this communication, the suppression of pyrite oxidation by treatment with fatty acid amines (FAA) was investigated. The FAA treated pyrite samples were tested at various conditions of temperature and pressure. At an elevated oxygen pressure of 500 psi and a temperature of 600 C, less than 0.2% oxidation was obtained for the FAA treated pyrite samples, while over 1.2% oxidation was obtained for the untreated samples in 10 hours of oxidation time. Accelerated column oxidation tests at ambient condition showed that FAA mated samples reduced pyrite oxidation by at least 75% in 81 days.

Jan 1, 1994

By C. Pereira

Spent nuclear fuel (SNF) can be treated in a molten salt electro refiner for conversion into metal and mineral waste fonns for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission product cations from the molten salt. Breakthrough of cesium and the alkaline earths occurred more rapidly than was observed for the rare earths. The effluent composition as a function of time is presented, as well as results for the distribution of fission products along the length of the column. Effects of temperature and salt flow rate are also discussed.

Jan 1, 1996

By Jack S. McPartland

The recent developments on the concentration and recovery of gold from leached gold thiosulfate solutions by solvent extraction, reduction-precipitation, and electrochemical deposition are reviewed in this paper. Alkyl phosphorus esters have been found to extract gold only in alkaline thiosulfate solutions, The recovery of gold increases with thiosulfate concentration in the aqueous phase and with alkyl phosphorus esters concentration in the organic phase with aliphatic hydrocarbon diluents. The addition of ammonia improves the extraction. The extraction of gold with amines in either aliphatic or aromatic diluent decreased in the following order: primary>secondary>tertiary amines. Increase in the extractant concentration at high pH increased the extraction of gold. At pH < 9, the primary amine, RR&apos;CHNH2 with 1&apos;9-23 carbon atoms is the main extractant with TBP as the synergistic reagent and at pH >9, the primary amine shows a synergistic effect on the extraction of gold&apos; with TBP. TheAu(I) ions in thiosulfate solution are reduced by sodium borohydride (SBH) to metallic gold, with particles in the sub micron range, At an SBH/ Au ratio of 6.25, pH = 6, and at room temperature, the I e ppm Au(I) in a solution of ] 0 gil thiosulfate was completely reduced to metallic gold in about 60 minutes.

Jan 1, 1999

By H. Kamarudin

The behaviour of cassiterite-sulphosuccinamate flotation system was examined in the light of zeta potentials measured by micro-electrophoresis method. It was observed that sulphosuccinamate substantially affects the zeta potentials of cassiterite, lowering its i.e.p. to pH 2.5 and indicating a specific adsorption and/or chemical interaction. The optimum concentration for flotation, as seen in micro-flotation tests, was found to be associated with the most effective lowering of the zeta potentials, the optimum pH being 3.0. The effect of cations in the pulp was examined for the presence of ferrous, ferric, aluminium and lead ions. The ions ferric and aluminium were observed to create an intense effect of increasing the potentials to positive side, possibly due to adsorption of cation hydroxy complexes, as indicated by their respective species distribution diagrams.

Jan 1, 1994

By M. Pakala, Z. Fan, Ray Y. Lin

Deposition of hard chromium coatings using electrodeposition is accompanied by emission of hexavalent chromium mists which is a carcinogenic. Hence alternative chromium deposition technologies are being investigated. Sputter deposition is a strong candidate to economically deposit hard chromium coatings in an environmentally friendly way. Chromium coatings of 2-3 µ m thickness were deposited on plain carbon steel coupons using RF magnetron sputter deposition. Depositions were carried out with 0 to 22 vol% nitrogen in the plasma. Structure of the coatings was studied using x-ray diffraction analysis With increasing nitrogen contents, formation of the two nitride phases was observed. The pure chromium phase was detected in coatings with up to 7% nitrogen in the sputtering gas. The solid solution of nitrogen in the pure Cr phase coating was identified by shifts of Cr x-ray diffraction peaks to higher d-spacing. The microhardness of the coatings deposited at a substrate temperature of 200°C showed an increase in hardness with increasing nitrogen content from 600 kgf/mm2 (5.9 GPa) at 0% nitrogen to I250 kgf/mm2 (I2.25 GPa) at 9.5 % nitrogen and a subsequent decrease in hardness to I 100 kgf/mm2 (11 GPa) beyond 9.5 % nitrogen in the sputtering gas. This corresponds to the formation of the hard Cr2N phase, at 9.5 % nitrogen, and CrN phase, at I5.7 % nitrogen. The reported bulk hardness values of Cr2N and CrN are I600 kgf/mm2 (I5.7 GPa) and I 100 kgf/mm2 (11 GPa) respectively. For pure Cr phase coatings, there is a slight increase in hardness for coatings deposited at 7. I % nitrogen from that without nitrogen in the sputtering gas. This could possibly result from the solid solution strengthening of the Cr lattice by nitrogen. For films deposited at 200°C, phases of the deposited films seem to be the overwhelming factor in controlling the microhardness.

Jan 1, 1998

By Michael L. Sorokin

The various methods of converter slag cleaning operation are analysed from the thermodynamk point of view: cleaning using coal, cleaning using combustion products of natural gas and cleaning in presence of matte. All calculations were done, applying the developing computer procedure based on the free energy minimisation algorithm. Three-suffix Margules equations were used to calculate thermodynamic properties of melts; The calculations resulted in recommendations for the practical appliance.

Jan 1, 1995

By Luciano E. Ramírez, Jesús L. Valenzuela, José R. Parga

"An innovative process for removing copper cyanide complexes including silver and zinc from cyanidation circuits has been developed. The technology was based on the inducing the nucleated precipitation of copper and silver in a tube serpentine reactor, using sodium sulfide as the precipitate and sulfuric acid as pH control. The results showed that pH had a great effect on copper cyanide removal efficiency and the optimum pH was about 3 to 3.5. At this pH value copper cyanide removal efficiency could be achieved above 97 and 99 % ,when influent copper concentration ions were 650 and 900 ppm respectively. In this process (sulphidizaton-acidification-recycle-thickening), the cyanide associated with the copper cyanide complexes is released as HCN gas under weakly acidic conditions, allowing it to be recycled back to the cyanidation process as free cyanide. This system was successfully commercial applied at Minera William in Mexico.IntroductionThe recovery of gold and silver from minerals and concentrates with cyanide is an important hydrometallurgical process, which has been studied for more than 124 years. Patented by MacArthur in 1888 [1], the process relies on the fact that gold dissolves in aerated cyanide solutions to produce the gold cyanide complex. The stoichiometry by wich this reaction occurs is known as the Elsner equation as shown here. Silver is accomplished in the same fashion."

Jan 1, 2012

By Marco Zurco, Claudia M. Mendez, Alicia E. Ares, Carlos E. Schvezov, Carlos M. Rodriguez

"Zinc-Tin alloys were solidified in horizontal form and the obtained results were analyzed. During solidification the distribution of temperatures were measured by using thermocouples located strategically along the length of the samples. From the measured temperatures the following parameters were derived; the local temperature gradient, the cooling rate and the velocities of the liquid and solids fronts. Comparing the structure of the samples and the values of these parameters it was found that the temperature gradient reaches minimum values of as low as - 0.6 °C/cm, and velocities of the fronts of around 0.1 cm/s. In addition, the grain size was measured along the samples. The results are presented and discussed in the frame of the results previously obtained for other alloys.IntroductionGenerally solidification leads to two types of grain morphologies: columnar and equiaxed. The origin of each one has been the subject of numerous theoretical and experimental researches in the field of metallurgy for many years [1-7]. The columnar-to-equiaxed transition, CET, is considered as an object of high technological relevance with respect to the directional solidification of metallic alloys. This structure transition may be sharp or gradual and it has been reported to be dependent on thermal conditions associated with the casting process, including melt convection, heat transfer coefficients at the metal-mold interface, growth rates, thermal gradients, cooling rates, transport of solute, alloy composition, melt superheat, mold temperature, mold design, casting size, casting geometry, and the concentration of nucleating particles. As a consequence, it is critical for industrial applications to understand the physical mechanisms which control this transition during solidification. Many studies highlight the importance of the relative growth of the equiaxed and columnar grains and develop expressions or numerical procedures to describe a criterion for the CET. A number of experimental investigations reported in the literature suggest that the CET occurs when GL in the melt reaches a minimum critical value [5-7]."

Jan 1, 2012

By S. Seetharaman

In the processing of molten metals, it is extremely important to monitor continuously the concentration levels of various minor elements, In the production of common metals like copper, iron and aluminium electrochemical sensors involving solid, as well as liquid electrolytes are being increasingly used to measure the concentrations of minor elements The present paper deals with the electrochemical principles underlying these measurements and the possible errors involved. One of the major difficulties in the case of the solid electrolytes is to correct for the consequences oldie electronic contribution to the conduction of the electrolyte. The application of the electrochemical sensors for molten metals processing involves designing of these probes to withstand the industrial operating conditions. In this respect, significant achievements have been made with respect to the design of oxygen probes for liquid metals in general and liquid copper in particular. Some of the salient design features are discussed in the paper, The application of auxiliary electrodes for impurities in molten metals like phosphorus in copper and silicon in iron are taken up. The development of oxygen sensors for slags is given special attention. Recent developments&apos; in the field of sensor technology, as applied to metals processing are highlighted.

Jan 1, 1996

By H. L. Fraser

A review of the possibilities of performing microchemical analysis in thin sections using a combination of scanning transmission electron microscopy and energy dispersive spectroscopy of x-rays is given. Particular attention is paid to the factors that limit accurate analysis at the highest spatial resolution. As an example of the use of these techniques applied to a potential problem in minerals processing, the identification of iron pyrite and pyrrhotite particles in Illinois, Herrin #6 coal is presented.

Jan 1, 1981

By Jie Li, Zhongliang Tian, Xun Hu, Kai Zhang, Yanqing Lai, Hongliang Zhang

The Al-Sc Alloys show many advanced properties for a wide range of engineering applications. But the metal Sc must be added into the metal Al in the form of the Al-Sc master alloy, which is usually produced by the thermal reduction process. In this paper, the decomposition voltages of Sc2O3 and Al2O3 in Na3AlF6-K3AlF6-AlF3 melt were calculated based on the Nernst equation. And the Al-Sc master alloy was prepared in the melt at 950°C by electrolysis. The results show that the Al-Sc master alloy can be prepared by the co-deposition of Sc3+ and Al3+ at the cathode if the concentration ratio of Sc2O3 to Al2O3 in the melt is more than 2:1 under the condition of the aluminum electrolysis. SEM and ICP analysis of the product indicates that the Al-Sc master alloy is made of the phase Al and the phase Al3Sc.

Jan 1, 2016

By N. Y. Ma

Solid wastes produced in ironmaking and steelmaking off-gas cleaning systems often contain zinc. The zinc level in these solid wastes is generally too high to recycle the wastes for iron through blast furnaces, but too low to economically treat the wastes for zinc through zincrecovery facilities. The behavior, status, and distribution of zinc in the ironmaking and steelmaking off-gas cleaning systems have been analyzed from three aspects: thermodynamics of zinc condensation, oxidation and deposition, correlation of zinc concentration with particle size and density, and aerodynamics of dust particles in the off-gas cleaning systems. Theory and supporting data show that spontaneous separation of zinc from iron-bearing dust occurs in the ironmaking and steelmaking off-gas cleaning systems. Dry off-gas cleaning systems provide the most favorable conditions and environments for zinc to separate from the dust. If highefficiency dry separators were applied and appropriately arranged in the off-gas cleaning systems, zinc would be concentrated, and the majority of the solid wastes could be recycled for iron recovery through blast furnaces.

Jan 1, 2008

By Varadarajan Seshadri

A physical model based on similarity principles was constructed for simulating the RH degasser of CST (Companhia Siderurgica Tubarao, Vitoria, ES, Brazil) to evaluate the circulation rate of the metal which essentially defines the degree of exposure of the metal to vacuum in the chamber and thus of the refining rate. The circulation rate on the other hand will influence the decarburization rate and removal of dissolved gases like nitrogen and hence it is essential to optimise this parameter to get maximum refining efficiency with minimum refming times, thus improving the productivity of the secondary refining process. Mixing characteristics in the ladle is evaluated by pulse tracer addition using conductivity-meters located at the down leg as well as at several locations in the ladle. The influence of gas injection through nozzles in the upleg with simultaneous bottom injection of gas as well as nozzle blockage on the circulation rates were investigated. Also simulation experiments of kinetics of decarburization were carried out using C02 adsorption-desorption process in sodium hydroxide solution as circulating fluid and the effect of, bottom gas flow rate in this case was also evaluated. The results were carried over to prototype and to optimize the process.

Jan 1, 2003

By N. Voennann

Stillwater Mining Company operates an electric furnace at its smelter in Columbus, Montana to treat a Ni-Cu-platinum group metal concentrate along with secondary PGM bearing materials. Hatch Associates has designed several improvements to this furnace, which was originally built by others. Implementation of these relatively low cost improvements has resulted in substantial increases in furnace availability and capacity, along with reduced unit costs. ? The improvements included: ? Installation of water-cooled copper cooling elements to stabilize refractory wear and increase furnace life.- ? Improved furnace &apos;bindings, to enhance the furnace&apos;s structural integrity by improving the contact between the refractory and cooling elements, and by promoting tight brick joints resistant to matte or slag leaks. ? Adjustment of the electrode regulator to allow higher furnace power levels. ? Installation of an automated air-slide (aeration conveyor) feed system to evenly distribute the furnace feed in an insulating layer on the bath surface. This "black-top" practice reduces unit energy costs and makes available additional smelting capacity.- ? Electrode seals to reduce ingress of air that absorbs heat before exiting the furnace in the off-gas stream. The saved energy can be used to smelt additional concentrate. This paper describes the above furnace modifications, and the benefits derived from their implementation.

Jan 1, 1998

By C. J. Newman

The Kidd Creek Copper Smelter has been expanded from its original design of 59,000 tonnes of copper per year to over 120,000 tonnes per year. Modifications to the process gas handling system and acid plant have been made to accommodate this higher production rate and to generally optimize the operation. The gas handling system associated with the continuous smelting process is discussed in terms of boiler accretions and modifications to minimize their impact on operations; design changes to effect reductions in high pressure drop duct configurations; material changes to overcome corrosion and plant additions to improve gas cleaning capability. The acid plant is reviewed with references to changes? made to accommodate the increased SO2 gas strength resulting from the higher smelting rates.

Jan 1, 1992

By J. M. Demarthe

MINEMET RECHERCHE (IMETAL Group, formerly Le Nickel-Penarroya-Mokta) has studied on a laboratory scale and patented a new process to recover metal values -copper- from sulphide ores and concentrates. It combines a cupric leaching, solvent extraction and copper sulphate electrowinning according to the main following steps - A direct and selective leaching of copper sulphide ores or concentrates at atmospheric pressure with cupric chloride to form cuprous and ferrous chlorides and elemental sulphur. Pyrite remains in the sulphur residue. - The leach solution is separated into two parts -In the first one, air is injected to precipitate iron as goethite. The oxidation step can be easily realized at atmospheric pressure by maintaining an excess of cuprous and-ferrous chlorides in the liquor. Copper is extracted from the second part as cupric ion by an LIX reagent. Direct injection or air in the mixing chamber maintains good extraction conditions, so that only one mixer settler is required. - Iron, in the form of ferrous ion, is not coextracted. - Copper is stripped from the organic phase, transferred into a sulfuric phase and sent to sulphate electrowinning cells, which are now conventional in copper metallurgy. - Only electricity and air are required. After a feasibility study, the next step will be to develop it on a pilot and commercial scale.

Jan 1, 1976