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By Baozhong Ma, Yonglu Zhang, Yongqiang Yang, Chengyan Wang, Yongqiang Chen

During the past decades, slurry electrolysis (SE) has been implemented commercially for the processing of bismuthinite and complex Pb-Cu bearing gold concentrates. Recently, SE was proven effective for the treatment of As-rich antimonic gold concentrates. Laboratory test results suggest over 98% of the antimony was extracted, while the extraction of arsenic and gold was less than 0.5%, and that of iron was less than 6%. Moreover, the cathode antimony contained over 98% antimony and less than 0.3% arsenic. Considering the disadvantages of traditional 3 kA slurry electrolysis baths, such as smaller electrode area, reduced capacity, and greater electrode deterioration, the authors have developed an innovative 12 kA slurry electrolysis bath equipped with mesh and fence type titanium alloy electrodes. Furthermore, the technique was successfully used within a pilot scale plant yielding results similar to those observed in the laboratory. The technique yielded ametallic antimony ingot of 99.9% purity after arsenic removal via the addition of Na2CO3.

Jan 1, 2014

By W. K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating improved technology for mineral flotation. A variable often neglected in flotation control is redox potential. The use of redox control is illustrated by the separation of molybdenite from chalcopyrite. Laboratory testing showed that redox potential had a greater effect on product quality than collector addition. A significant need in froth flotation is greater reliability of the sensors used in measuring and controlling redox potential in mineral slurries. The USBM has developed an automated method for removing scale and reconditioning gold redox-sensing electrodes. Fouled electrodes are anodically polarized to 1.2 V versus the AglAgCI reference potential to remove scale. The electrodes then are conditioned by a brief potentiodynamic treatment to re-establish electrochemical equilibrium. In laboratory tests, this technique removed calcarious deposits from gold electrodes and reconditioned them for useful service in approximately 10 min. In plant practice, this technique would obviate the need for plant operators to manually polish electrodes, and also should result in greater reliability in redox measurements. Inexpensive, automated equipment to condition electrodes in a plant setting is described.

Jan 1, 1995

By D. E. Larson

The U. S. Bureau of Mines has developed a image analysis methodology to correlate the energy consumed during the grinding of an ore to the mineral liberation achieved. Energy consumption values are obtained using a laboratory-scale ball mill equipped with a torque sensor, and an automated image analyzer is used to determine the liberation present in ground products. By combining liberation information with energy consumption data an appraisal can be made of the energy required to liberate the mineral(s) of interest. Results of tests performed on a complex sulfide material determined the effects of grind duration on the liberation achieved and the energy efficiency.

Jan 1, 1995

By Wayne Bell, Matthew Andriese, Shuqian Xie, Jiann-Yang Hwang, Zhiwei Peng

"Pyrolyzed carbons are generally known as good microwave absorbers and their dielectric properties still remain to be fully explored. In the present study the dielectric properties and dielectric polarization-relaxation phenomenon of a typical activated carbon was investigated. The experimental results indicate the complex permittivity is highly dependent on temperature and frequency. The decrease of permittivity with increasing temperature from room temperature to ~100 °C is probably ascribed to the release of the water vapor adsorbed on the surface of activated carbon, and the variations of permittivity with temperatures between 100 °C and 450 °C in the frequency range of 300 MHz to 3000 MHz are mainly attributed to the decreased relaxation time of dielectric polarization.IntroductionPyrolyzed carbons have been identified as excellent microwave absorbers owing to their high dielectric and electrical loss under microwave irradiations. Among them, activated carbon continues to attract more and more attention from researchers. Due to its special physical properties, the production, modification and regeneration of activated carbon with the assistance of microwave have been widely studied over the last few decades [1-6]. However, only few attempts have been applied to explore the dielectric properties of such materials due to the complexity and variability of their organic precursors and activation processes [7,8]. In order to shed a light on this problem, a typical sample, Norit® A Supra USP powdered activated carbon, was adopted to perform dielectric characterization, which may provide useful information for its wide application in the fields of purification, energy (hydrogen) storage and so on."

Jan 1, 2011

By S. Illendula, B. Q. Li, R. A. Mirshams

"An integrated mathematical model is developed to represent the thermomechanical behavior of the materials and microstructure evolution during metal forging. The model development is based on the finite element solution of the thermoviscoplastic deformation of metals coupled with the internal state variable model describing the microstructure evolution involving work hardening, recovery, recrystallization and grain size distribution. The procedures for the integration of the microstructure model into the macro finite element model are described. Computed results for both macro and micro phenomena during metal forging, such thermomechanical deformation such as velocity field and effective strain rate and materials characteristics such as distribution of grain size and recrystallization volume fraction, are presented.1. IntroductionThermomechanical behavior and material microstructural evolution are two critical, interrelated aspects associated with metal workpiece undergoing large plastic deformations such as encountered in forging processes. In much of the modeling work up to date, these two aspects have been addressed separately. Die designs and forging processes are investigated using finite element based thermomechanical models while material dynamics during forging is studied, more often than not, as a separate subject. For many industrial applications, especially those involving novel, light and high strength materials, it is critical to combine these two aspects into a single, integrated model so that materials dynamics and thermomechanical deformation during forging processes can be considered simultaneously [1], thereby providing required information for intelligent process design and optimal process control."

Jan 1, 1998

By R. G. Reddy

To better understand the behavior of bacterial-mineral interfacial reactions, a thermodynamic model based on the- studies of bacteria adhesion on mineral surfaces has been evaluated. The bacteria adhesion to the mineral surface would be increased by l ' d1;1creasing the change in Gibbs free energy of adhesion and it would be reduced if the change in Gibbs free energy of adhesion of the system is increased. From the combination -of Young's equation and equation of state, the change in Gibbs free energy of adhesion -for bacterium-mineral system- was calculated. Influence of liquid surface tension, mineral surface tension on the change in Gibbs free energy of adhesion and consequently bacteria behavior on mineral systems- has been discussed.

Jan 1, 1991

By P. Gray

Process and engineering development of the Warner Zinc Process over the past two decades has proceeded alongside the world-wide collection and analysis of operating and cost data of current processing practices from sulphide ores to refined metals. Study of these data shows that recoveries are dependent on mineralogical characteristics of the sulphide matrix and point to the inadequacy of differential flotation as a tool for preparing feed for smelters. The paid-for return at the mine on the combined metal values in zinc rich sulphide ores rarely exceeds 80% and increasingly runs as low as 50-60%. Surveying the possible alternative ways of improving these performances leads to the conclusion that the Warner Process is the only technology in sight that could meet a target of 90% paid-for recovery and that its development has now reached a point where it can be a fully practicable process for all mixed sulphide ores.

Jan 1, 2000

The direct removal of lead ions from D2EHPA-kerosene using metallic zinc as the reducing agent was evaluated. The electrochemical process, called galvanic stripping, is a potential alternative stripping technique when standard chemical methods are not adequate. Four parameters found to be important in the rate of lead removal were studied in a factorially designed experiment. The variable evaluated included D2EHPA concentration, temperature, zinc surface area and solution agitation. Temperature and surface area were found to be the most significant, while agitation and D2EHPA concentration had less influence on the reaction. An activation energy of 22.5 Kcal/mole was calculated indicating a chemically-controlled process. The reaction was also sensitive to the concentration of oxygen in the system. The zinc required was considerably in excess of stoichiometry, possibly due to the dissolution and redeposition of lead: In general, the results were encouraging and demonstrated that lead impurities could be removed from D2EHPA using cementation type reactions.

Jan 1, 1995

By Hector Henao

To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni-S alloy and the CaO-Ah03 based slag melted in a MgO crucible at 1873 K under controlled Pso2 of 10.1 kPa and pO;, in a range between 2.5x,IO,2 and 10.1 Pa by using CO-C02-S0Z gas mixtures. The content of nickel in the slag at POz of 10.1 Pa, above which solid NiO is expected to precipitate in the equilibrium state, was found to be 4.1 mass% and the contents of sulfur and oxygen in the nickel melt were 0.4 and 0.2 mass%, respectively. It was clarified that increase in the temperature reduces the solubility of nickel in the slag and the contents of sulfur and oxygen in the alloy. The distribution of minor elements such as gold, silver, copper, cobalt, iron, arsenic and antimony between the Ni-S alloy and the CaO-AI20) based slag was also studied. The distribution ratios of iron and cobalt, defined by (%X in slag)/[%X in alloy] where X is the minor element, are larger values than that of nickel, while those of copper, silver and antimony are similar to that of nickel. The distribution ratios of arsenic and gold are lower than that of nickel in the higher range of oxygen partial' pressure.

Jan 1, 2003

By Henrique Kahn

The Anitapolis alkaline massif in southern Brazil underlies a sub circular area of 6 km2. Bore-hole data show a concentric rock distribution, with mafic rocks in the central part and felsic rocks in the border zone. The rocks are covered by talus and weathered material, 30 m thick on average, and very inhomogeneous in composition. Phosphate mineralization associated mainly with two levels of the weathering mantle and with fresh rocks. A preliminary ore-type classification was based on distribution of apatite, feldspar, vermiculite, biotite-phiogopite, calcite, pyroxene, amphibole and analcime, determined by semiquantitative diffraction method. Technological tests performed on eluvial ore samples from three adits resulted in a subdivision of ore-types based on the difference in behavior due to mineral characteristics during mineral pr

Jan 1, 1991

By Yousef Mohassab, Manoranjan Misra, Monalisa Panda, Eman Wahbah

This work studies the removal of arsenic (V), arsenate, and arsenic (III), arsenite, from aqueous solution using calcined Quintinite-3T. The two adsorbents Quintinite-3T was prepared, calcined at different temperatures, and characterized by XRD, BET, and SEM. The surface area of the calcined Quintinite-3T was 193.4 m2/g. The particles size ranged from 12 to 56 nm for the uncalcined Quintinite-3T and from 24 to 42 nm for the calcined Quintinite-3T. Kinetic analysis, adsorption isotherm, and factors affecting the adsorption were investigated. Calcined Quintinite- 3T retained As(v) and did not release it back to water even after an entire month.

Jan 1, 2016

By Baokuan Li, Fang Wang

"Comparing with the single electrode in electroslag remelting processes, two series-connected electrodes have the advantage of little inductance, lower power consumption and higher melting rate, which was widely used to produce superalloys and specialty steels. Detailed understanding of the electromagnetic field distribution is essential for both improving ingot quality and saving electric energy. In the present work, a 3D finite element model was developed for the magnetic field, electromagnetic force, current density and Joule heating field of electro slag remelting processes (electrode, slag and ingot) with two series-connected electrodes using Maxwell equation, Lorentz law and Joule law. The results show that the maximum current distribute occur at the middle of electrode, due to the interaction of selfinduced and mutual-induced of two series-connected electrode; associated magnetic flux density on the inner side of electrode increase and the outer decrease; The maximum joule heating is at the interface of slag and electrode. The parameter study shows that if the current frequency is greater than 35Hz, the current density in inner electrode tend to linear distribution; with the increasing of original current, The maximum current density near the wall in electrode will increase linearly; with the increasing of electrode innnersion depth and decrease of slag cap thickness and the maximum of the joule heat in slag will increase.IntroductionElectroslag remelting processes(ESR) are widely used to produce superalloys and specialty steels [l-3l_Two pair, four pair or six pair electrodes in electroslag remelting processes is common in casting large scale ingot, which has the advantage of little inductance, lower power consumption and higher melting rate, comparing to singe electrode. They have the same essence with two electrodes in ESR.Compared to the single electrode ofESR, the other electrode is added which can decrease the reactive resistance and power consumption in the two electrodes of ESR. It is a complicated metallurgy process with a series physical and chemistry phenomenon from the molten of steel to the solidification of ingot [4-71_ These physical and chemistry phenomenon originated the effect of alternating current of high intensity. The rule of the alternating current of high intensity which revealed the law of physical and chemistry phenomenon in ESR is the precondition of improving ingot quality and saving electric energy. Jihe Wei and Yongli Ren[S-9lstudied the distribution of electromagnetic field in single electrode ofESR with Maxwell equation and relative electromagnetic theory. It had the limitation that take the electrode and mold as infinite conductivity. A detail analysis of Electromagnetic fields in ESR had been conducted by Patel A D [JO-llJ using general stream-function formulation. It is difficult to extend to three dimensions which could not be used widely. Daniel V [lZJ and Kharicha A [BJ only analysis the current density associated magnetic flux density field and temperature field without the whole irlformation of electromagnetic field. Maopeng Geng [l4J considered the current density and temperature field of the real and fake electrodes in ESR without skin effect. As to the complication of the two electrodes of ESR, it is rarely reported the electromagnetic field and Joule heating field of the two electrodes in ESR. The rule of effect of electromagnetic and modification of numerical simulation should be studied in depth."

Jan 1, 2011

By Alessandro Blasi, Massimo Morgana, Corradino Sposato, Pietro Garzone, Giuseppe Devincenzis

The rare earth elements are essential for a diverse and expanding array of high-technology applications, which constitute an important part of the industrial economy of the 21st century. As a matter of fact, rare earth has been listed in the category of strategic elements in many countries becoming a core business for international research. Experimental tests have been carried out on a bench scale battery of mixer settler composed of 24 stages, each one with a volume of 150 ml. These trials have been performed at room temperature checked by a micro-climatic control system. The battery was setted in two sections: extraction and scrubbing section. Rare earths concentrations were obtained by ICP-OES analysis made on aqueous phase and on the stripped from organic phase. We obtained a complete separation of light rare earth (La, Ce, Pr, Nd) in two sub-groups: La/Ce and Pr/Nd.

Jan 1, 2014

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 O. A. Ogunseitan

The contamination of aquatic ecosystems by mercury wastes is one of the most serious forms of environmental pollution associated with the metal mining and electrochemical industries. The transformation of inorganic mercury to alkylated species is a reversible bacterially-mediated process. The production of methylated mercury is of ?major public health and eco-toxicological concern because these forms of mercury are highly toxic ?and they bioaccumulate in aquatic organisms. We determined the response of the genetic determinants of mei:cury transrormation by Pseudomonas species (that predominate in contaminated soils and sediments), to the concentration and species? or available mercurfiations. By combining selective isolation and gene. ?probe techniques, the intrinsic genetic potential for mercury detoxification in a contaminated environment ?can be estimated. We determined that genetic units required for mericury volatilization (merA ?for mercuric reductase) are naturally amplified in response to mercury. Mercury-resistant bacteria that tolerate up to 100 ug Hg(Il)/ml of medium contain about 10 times more DNA fragments encoding merA than in unadapted bacteria. The exposure of bacteria to methylated.Hg (10 ug/ml lake water) produced increases (up to 10 times) in .genetic units, and higher levels of genetic expression (up to 50 times) per ml of lake water for the mercury reductase system, than on-induced lake water. The findings suggest that in environments where methylated Hg may accumulate as a result of bacterial activity, the reverse reaction which leads to the removal of mercury through volatilization from the system, may be achieved by inducing genetic ?amplification and expression of the mercuric reductase gene system.

Jan 1, 1991

By L. J. Cabri

The level of mineral exploration activity for platinum in recent years, especially in North America, has ranged widely. Exploration programs have been based on a variety of ore deposit models and deposit types. These range from the classic magmatic model for sulfide/oxide deposits and their associated placers, through hydrothennal models for bonanza-type deposits, to low-grade mineralization potentially amenable to lower cost bulk mining methods. The platinum-group element (PGE) distribution in these different deposit types is not well-known however, and PGE determination is fraught with analytical difficulties. To properly assess a prospect or to achieve effective recovery by mineral processing, it is important to determine the mineralogical distribution of the PGE.

Jan 1, 1988

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By Luben Xie, Lin Hu, Qiang Wang, Min Gan, Tao Jiang, Wenqi Li, Yi Wang, Xiaohui Fan

"The mineralization behaviors of typical fluxes are studied by investigating the microstructures with optical microscope. The results show that the reactions begin with between iron ore and lime, limestone with small particle to form primary liquid. Then coarse limestone, dolomite and serpentine take part in reaction under the action of primary liquid. Limestone is the easiest to mineralization, next dolomite, and the last is serpentine. The higher basicity and smaller fluxes size favor the mineralization process of dolomite and serpentine.IntroductionThe purposes of adding fluxes into sintering are that:(1) to increase the basicity of sinter, so as to reduce even eliminate addition fluxes into BF(blast furnace) and decrease the coke ratio of BF[1,2]. (2) to decrease the melting point of sintering mixture to ensure sintering can be carried out at a lower temperature and reduce the energy consumption. (3) to improve the qualities of sinter by forming binding phase with iron ore fines [3].Flux is another significant component for sinter besides iron ore, especially for high basicity sinter[4]. The proportion of flux is usually higher than 10% in sinter mixture(excluding return mine).There were many reports about the influence of the flux types on sintering, such as limestone, dolomite, lime and so on[5-7]. It is very important to choose suitable fluxes for iron ore sintering. Although the effect of flux size on sintering also has been researched, the mineralization behaviors of the fluxes in the sintering process has not been illuminated. The paper will study the mineralization behavior of fluxes in sintering."

Jan 1, 2011

By J. Leon-Torres, D. M. Stefanescu, P. A. Curreri, S. Sen

"Experiments were performed under terrestrial gravity (lg) and during parabolic flights (10·2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce rnicrostructural and macrosegregation maps.In all cases positive segregation occurred next to the chill because of the shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient.A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium.The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results."

Jan 1, 1999

By Gus Van Weert

The cost of oxygen is a major and common factor in the hydrometallurgical processes developed or proposed tor the oxidation of refractory pyrites. This cost involves charges for the generation and the transfer of the 02 to the mineral slurry. Bio-oxidation faces considerable design demands which require large scale equipment to be resolved. Nitric acid assisted oxidation offers low cost oxygen units; this method of pyrite oxidation deserves a closer look for large scale plants treating pyritic gold ores and concentrates.

Jan 1, 1990