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By D. M. Fermino, C. G. Bastos Andrade, M. G. Fernandes, F. R. Valenzuela-Diaz

Treatments with high concentration solution of inorganic acid at temperatures under boiling point are a usual method for clay minerals structure modification. For many industrial uses bentonites must be cleared of impurities. In the present paper, a sample of Brazilian bentonite from Vitoria da Conquista, Bahia was modified by mild acid attack using hydrochloric acid under moderate conditions (90 °C, reaction times of 1, 6, 12, 18 and 24 h in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5 M, acid solution/clay ratio of 1 g/10 mL). The attacked samples were characterized by CEC, XRF, SEM, EDS and Stereomicroscopy. The purpose of these attacks is to reduce the concentration of impurities with minimal damage in clay minerals structure. The modified bentonite presented good results and tends to be a good economic and environmental alternative to manufacturing products with high added value such as polymer/clay nanocomposites, cosmetics and medicines.

Mar 1, 2017

By R. F. Hammen

Copper is one of the most widely used metals in industrial processes and is also present in most mining operations. Extraction of copper from solutions often proves difficult due to the presence of complexing agents. ChromatoChem, Inc. has developed a Solid Phase Extraction (SPE) support (HiPAC) for removal and recovery of metals from wastewater. The HiPAC SPE support employs chelating agents covalently coupled to a long linker molecule. Several solutions containing copper and complexing agents were tested including 1) copper and carbonate, pH 9.8, 2) mixed metals and anions with copper and cyanide, pH 11, and 3) copper and the chelating agent EDTA, pH 11. The copper was extracted from solutions one and two at high pH, but the EDTA containing solution needed the pH lowered to make the copper available for capture. In each example, the copper concentration was significantly reduced by HiPAC SPE treatment.

Jan 1, 1994

By Antonio de Ita, Isaias Hilerio, Miguel Barron

"The influence of an unconventional lance with a central nozzle on the multiphase fluid flow in a steelmaking converter is studied in this work by means of computer simulations. The lance has four peripheral supersonic nozzles and a vertical central nozzle. Besides, the oxygen flow in the central nozzle is considered independent from the main oxygen supply. Transient two-dimensional numerical simulations were carried out considering just molten steel and gaseous oxygen as the existing phases. Numerical results show that bath agitation and droplet generation are enhanced as a result of the central nozzle. However, the performance of this lance strongly depends on the distance of the lance tip to the molten steel surface and the velocity of the oxygen jet.IntroductionCurrently, two thirds of the world crude steel is produced through the steelmaking oxygen converter [1]. Given the unquestionable economic importance of this technology, any improvement or optimization proposal is welcome. In the majority of current oxygen converters a top oxygen supersonic jet is blown onto the molten steel through a water-cooled lance to eliminate by oxidation some impurities such as carbon and phosphorus. Conventional lances have inclined peripheral nozzles whose number depends on the converter capacity. During the process, a large amount of gases evolves, forming metal droplets and a metal-slag-gas emulsion [2]. The droplets and the resultant emulsion increase the reaction interfacial area, promoting in this way carbon removal and dephosphorization of the molten steel bath [3]. However, during the blowing stage, the emulsion rises towards the lance and converter mouth and frequently forms layers which accumulate in the lance, reducing the life of the lance tip [4, 5]. It is possible that some freezing of the molten metal occurs due to the low oxygen injection temperature, however there are no reports on this. Besides, frequently undesirable operating phenomena such as spitting and slopping may arise as a result of inappropriate blowing practices or bad lance design. In the oxygen steelmaking industry, novel lances design are needed in order to enhance the decaburization rate and the slag formation and, at the same time, preventing operating practices that decrease productivity and move away the shop from safety standards."

Jan 1, 2012

By Brent W. Madsen

The acid-ferric sulfate leaching of low-grade sulfide copper mine waste provides more than 10 percent of the U.S. supply of new copper, but recoveries and leaching rates are very low. In Federal Bureau of Mines research to improve the leaching process, experiments on 5- to 10-ton lots of mine-run ore were more revealing than bench-scale tests on fine ore. This report discusses the results obtained by leaching run-of-mine and minus 6-inch plus 112-inch samples of low-grade chalcocite-bearing mine waste. The samples were leached for 461 days and 61.6 and 37.7 percent of the copper was extracted from the minus 6-inch plus -112-inch and run-of- mine samples, respectively. A mixed kinetics model was applied successfully to the leaching of the sample with the fines removed where bulk solution transport was not rate controlling. The model, when applied to the run-of- mine ore, gave somewhat higher predicted copper extractions than experimentally determined. Subsequently, oxygen was introduced into the run-of- mine ore, leaching continued for an additional 312 days, and an additional 53.0 percent of the copper was extracted. Before the leaching experiment was dismantled and the residue sampled, the ore was treated with sulfur dioxide and its permeability was improved markedly. The results of each of these procedures are interpreted in relation to the attendant condition of the test.

Jan 1, 1976

By Guillermo Rios, Arbizum Cristina, Joa Viflals, Alba Sunyer

"Atlantic Copper is one of the largest copper producers in Europe. Its production facilities are located in Huelva (Spain) and account for the smelting of over one million tpy of concentrates to produce up to 260 ktpy cathodes and 900 ktpy of sulphuric acid. During copper concentrate smelting, the slag coming from the flash furnace and PS converters are treated in an electrical slag cleaning furnace. As a result of the treatment of the off gases from this furnace, approximately 2,000 tpy of a Zn-rich filter cake are produced and are sent to authorized waste managers. This paper describes the characterization of this material and the preliminary results of a new process to recover zinc as a pure zinc hydroxycarbonate while lead is collected as an indium-rich anglesite product. The behavior of impurities (Cd, As, Tl, Sn, Sb, Bi, Cu, Se, Te) in the leaching, solution purification and precipitation steps is also reported.IntroductionThe Atlantic Copper Metallurgical Complex in Huelva (Spain) was commissioned in 1970 with a capacity of 40,000 tpy of copper from concentrate. In 1975, the old blast furnaces were replaced by Outokumpu flash smelting furnace (FSF) technology, and the copper refinery capacity was increased to 108,000 tpy. Between 1994 and 1996, an expansion project was carried out to increase the copper from concentrate and cathodes to 250,000 tpy and 215,000 tpy, respectively. This expansion basically consisted of a new sulphuric acid plant, replacement of the anode furnaces by two 400 t units, redesign of the slag cleaning furnace (SCF), an increase in the electrolytic cells to 1,120 and implementation of ISA permanent cathode technology. Furthermore, a debottlenecking project has led to a capacity of 1,000,000 tpy of fresh concentrate since 1997. Meanwhile between 1995 and 1998, a cathode production rate of 260,000 tpy was reached as a result of a progressive increase in the current density in the refinery."

Jan 1, 2012

By Isadora Dias Perez, Denise C. Romano Espinosa, Flávia P. Cianga Silvas, Jorge A. Soares Tenório, Mónica M. Jiménez Correa

In view of the rising generation of wastewater containing metals, sustainable and clean techniques to recover them are being researched. This study investigated the adsorption of aluminum, cobalt, chromium, copper, iron (III), magnesium, manganese, nickel and zinc presents in a synthetic ef fluent by chelating ion exchange resin Dowex XUS43605. The resin was tested in columns experiments and was analyzed the flow rate (0.45, 0.66 and 1.11 BV/h), at pH 1.5 and 20 °C. After loading the column, the elution experiments occurred with 1 M of H2SO4 and 4 M of NH4O. The concentration of the metals in solution was obtained by X-ray fluorescence spectrometry energy dispersive (EDX). The results showed that the breakthrough experimental curves demonstrated that the main metals (aluminum, cobalt, manganese and zinc) were immediately broken through just after the initiation of the feeding, while the breakthrough of copper began later. Therefore, the study showed that the chelating resin could be used to treat contaminated effluents with metals.

Mar 1, 2017

By K. P. Nishad

The origin of many casting defects can be traced at the mold filling stage. Entrapped air/gas pockets and oxide film formation are notable examples. In the present work, the mold-filling process is simulated using a mathematical model, built on a multi-physics based commercial package PHYSICA. The simulation code has the capability to solve multi-phase problems. The numerical model addresses a complicated dynamics of filling operation including free surface flow and subsequent flow behavior and is based on conservation of mass and momentum. The Free surface is modeled using the scalar equation method (SEM). The model is validated with benchmark experimental results from the literature. The role of turbulence and the pouring rate on variables affecting sites prone to oxide film formation are investigated using a simple but novel technique. Key findings of the work are presented.

Jan 1, 2006

By Christian Hecker

An Eh-pH electrochemical sensor developed for on-line pH and redox potentials copper sulphide flotation process control was studied. The electrochemical sensor cell includes two metallic platinum electrodes, a metallic antimony electrode and a high impedance reference cell which are polarized with a potentiostat. For pH and redox potential determinations, the Sb and platinum electrode potentials are measured, respectively, against the polarized electrochemical reference system. The behaviour of this electrode configuration has been investigated in a laboratory scale. An electrochemical sensor device has been succesfully installed and checked in El Teninte Colon Concentrator's SAG line feeding the copper flotation rougher circuit.

Jan 1, 1999

By S. Aguayo-Salinas, J. L. Valenzuela-García, A. L. Leal-Cruz, M. I. Pech-Canul, M. T. Certucha-Barragán

"The aim of this research was to carry out a comparative and systematic study of the degradation of cyanide by hybrid natural/biodegradation and biodegradation methods using a mixture of Pseudomonas sp and Bacillus megaterium native bacteria. Bioreactors consist of filled columns with contaminated ore containing 100 ppm of total cyanide. In the biodegradation tests a mixture of bacteria was inoculated into the biodegrading solution. Results of cyanide degradation show a similar asymptotic behavior in both the hybrid (opened system) and biodegradation (closed system) methods; however, for the same period of time (72 h) the permissible maximum levels (1-2 ppm of cyanide) are only attained in the closed system. While in the closed system the cyanide levels are reduced from 100 to 1.5 ppm, in the open system, cyanide decreases from 100 to 2.4 ppm.IntroductionOne of the most important tasks of mining industry is the treatment of the wastes generated in mining operations. Accordingly, industrial waste waters and ores represent a complex problem and a great challenge. In addition to ethic and communitarian considerations, there are laws that prohibit or regulate the contamination of water and air. Moreover, they establish that the restoration of wastes must be considered as a necessary operation cost [1]. Currently this important problem is being addressed by the mining and metallurgical industries using different approaches; mainly they are focusing on the treatment of waste waters and ores generated by the leaching process in which cyanide is used as a leaching agent for the recovery of precious metals as gold and silver. Cyanides have toxic characteristics and thus negatively impact the environment when they are discharged to the ground without previous treatment. While there are some processes in current use there are others that have only been proposed and that allow cyanide degradation, transformation to less toxic compounds and/or the complete elimination of cyanide. The second group includes a variety of techniques that use natural, chemical and biological treatments. Natural treatments consist of the passive abandoning of the heap and of its washing with water. Since these processes are slow and generate great volumes of water partially contaminated, then other alternatives should be considered."

Jan 1, 2008

By A. J. Meir, Paul G. Schmidt

"We present a novel approach to the mathematical analysis and computational simulation of fully three-dimensional, nonlinear, viscous, incompressible MHD flow in complex configurations involving several liquid and solid conductors. Such configurations arise in numerous metallurgical processes. Employing the current density rather than the magnetic field as the primary electromagnetic variable, it is possible to avoid artificial or highly idealized boundary conditions for electric and magnetic fields and to account exactly for the electromagnetic interaction of the flow region with the surrounding space. In addition, the approach lends itself naturally to finite-element based discretization techniques. As an application, we simulate the stationary flow of an electrically conducting fluid around a solid spherical particle of arbitrary conductivity, in the presence of crossed uniform electric and magnetic fields, and compute the Lorentz, pressure, and viscous forces exerted on the particle. This problem arises in connection with the electromagnetic filtration (purification) of molten metals before the casting stage.IntroductionNumerous metallurgical processes are governed by MHD effects resulting from the macroscopic interaction of liquid metals with applied or induced currents, electric and magnetic fields. Frequently these effects are technologically exploited in order to drive or to control the flow of metallic melts. Typical examples include the electromagnetic stirring of molten metals before the casting stage [1]; electromagnetic turbulence control in induction furnaces [2]; electromagnetic damping of buoyancy-driven flow during solidification [3]; and the electromagnetic shaping of ingots in continuous casting [4]."

Jan 1, 1999

Convential smelting of copper - cobalt - iron sulphide concentrates result in th eoxidation of cobalt and iron, which are subsequently lost into the slag. The emission of SO2 bearing gas from smelting causes serious health and environmentsl problems. In this investigation, three different types of copper - cobalt - iron sulphide concentrates, derived from froth flotation, were investigated, the concentrates, each containing more than 40 wt % percent gangue material, were directly reduced in the presence of lime and corbonin the temperature rnage of 1073 K - 1573 K, fo rthe production of an alloy containing copper, cobalt and iron. We demonstrate the basic principles of process physical chemistry for the recovery of alloy by carrying out a detailed process analysis utilising the predictions from thermodynamic equilibrium and results from the kinetics of reduction reaction. The effect of temperature on the reduction kinetics and alloy formation were determinedand analyzed in detail.

Jan 1, 2012

By M. Omneya El-Hussaini, M. Galal Abdel Wahab, A. Mohamed Mahdy, M. Fathi El Shahat

"Lead-zinc mineralization is distributed in Egypt along the Red Sea coast between El Qusier and Ras Banas. A representative sample from Um Gheig was collected and ground to -60 mesh for the mineralogical study. It contains hemimorphite (Zn2SiO4.H2O), sphalerite (ZnS), galena (PbS), calcite (CaCO3) and dolomite (CaMg(CO3)2) beside the gangue minerals gypsum (CaSO4.2H2O) and hematite (Fe2O3). Cadmium seems to be incorporated in the crystal structure of the zinc-lead minerals. The chemical analysis of Um-Gheig representative sample revealed that, it contains 16% zinc combined with 0.1% cadmium, 2.3% lead and 0.1% boron beside other elements.Pug and agitation leaching were performed on samples ground to -200 mesh to achieve the maximum dissolution efficiency of cadmium with respect to other elements. Cadmium leaching efficiency reached 90% by using 40% H2SO4 at S/L ratio 1/2 and stirring time 2 hours at 80o C. Cadmium was then separated as yellow precipitate of CdS from the sulfate leach liquor containing 0.9 g/l Cd, 145 g/l Zn, 0.15 g/l B and 0.01 g/l Pb. Separation of cadmium was carried out by direct precipitation using Na2S as well as H2S. The recovery of 94% cadmium free of zinc was achieved.IntroductionLead-zinc ores occur in Egypt in a few localities distributed along the Red Sea coast between El Qusier and Ras Banas. Um-Gheig Pb-Zn ore is a replacement deposit in limestone and calcareous sandstone in the basal series of the Middle Miocene rocks. The reserve of the ore deposits has been estimated by Soviet and German Experts to be about 900,000 Ton, Bishai [1]. As has been mentioned, zinc is a common element and cadmium is comparatively rare in almost zinc minerals. It was estimated that zinc is 200 times as abundant as cadmium. According to Bodas [2] about 2.1% of cadmium was carried by the Zn mineral hemimorphite (15.3% Zn) in Thailand. Also, Onal et al., [3] found that 164 g/t Cd was carried by Pb–Zn ore sample containing 10.17% Pb and 10.98% Zn from Aladag in Turkey. Cadmium metal has gained great importance due to its wide applications in civil and navy purposes as well as in nuclear field. It is characterized by its ability to absorb thermal neutrons during the chain reaction inside the nuclear reactors. It is also used in the manufacture of sheets which directed the chain reactions [4]."

Jan 1, 2008

By John Hollow

The Fort Knox Mine is an open-pit operation, located in Alaska, which started commercial production in March 1997. A conventional Mill processes 38,000 tpd of a low grade (1.0 g/t Au) free milling gold ore with a low sulphide component (below 1%). Gold production (11% from gravity and 89% from cyanidation) exceeds 400,000 ounces per year. Short retention time (20h), low temperature (7oC) and low grade make high leaching kinetics critical for the performance of the process. In April 2001, the treatment of True North ore, which represented 14.4% of the mill throughput and contained more sulphide in the form of pyrite, arsenopyrite and stibnite, resulted in a substantial drop in the average gold extraction from 87% to 72.6%. Laboratory investigations indicated that the addition of lead nitrate increased gold extraction to 91.7%. Further investigations were initiated to determine the leaching parameters and the nature of the problem. Subsequently, a lead nitrate addition scheme was implemented at the Fort Knox Mill that resulted in 2002 gold production being in excess of 31,000 ounces higher than that estimated for the non-lead nitrate reagent scheme. This paper presents the results of laboratory investigations and modifications in plant operating practices.

Jan 1, 2003

By Yongzhong Xiao, Tiejun Chun, Jian Pan, Deqing Zhu

"An innovative process of reverse floatation-direct reduction-low intensity magnetic separation was developed to effectively beneficiate the superfine run-of-mine (ROM) ore mined from Hunan Province, China. Mineralogy was measured that the ROM ore is of superfine low grade hematite ore type, assaying 27.2wt%Fetotal and with main valuable minerals of hematite occurring at size between 3 to 5µm. The upgrading results show that the final iron concentrate, assaying 88.3wt%Fe total and 94.5% metallization degree was obtained at an overall iron recovery of 69.9% under the following conditions: rough concentration by grinding of ROM up to 88.7% passing 0.074 mm and reverse flotation at pH=9.4, 100 g/t starch and 200 g/t dodecylamine (DDA), and coal reducing the rough concentrate pellets containing 12% calcium containing complex additive at 1200 oC for 120 min, and finally magnetic separation of the reduced pellets by grinding up to 89.2% passing 0.043 mm at 0.08 T field intensity.IntroductionWith the rapid development of iron and steel industry in China, there has been a soaring demand for iron ores in the past decade. The imports of iron ores have increased from 148 million ton in 2003 to 628 million ton in 2009 [1]. Iron making industries increasingly demand for high grade raw materials to improve product quality and reduce operation cost. However, availability of high grade natural ores is limited and enrichment of lower grade ores is necessary to meet the demand. Therefore, large quantities of superfine low grade iron resources are necessary to utilize in China at the moment."

Jan 1, 2011

By Masaaki Naito

The Japanese steel industry has a long history of introducing new and innovative technologies in the field of ironmaking. The new technologies introduced during the past ten years include technologies to use cheaper and lower-grade raw materials and fuels, measures to prolong the service life of blast furnaces and coke ovens, promotion of energy saving, use of wastes and solutions to environmental problems. This report outlines the condition of production and technological trends and technical development themes in ironmaking technologies.

Jan 1, 2006

By Shadia J. Ikhmayies

"Tin oxide (SnU2) thin films of thicknesses in the range 100-600 nm were prepared on glass substrates by vacuum evaporation at ambient temperature. The films were characterized by transmittance measurements, X-ray diffraction (XRD), scanning electron microscope (SEM) observations and energy dispersion X-ray analysis (EDAX). It is found that the films have high transmittance and non sharp absorption edges. XRD diffractograms showed that the films are amorphous and the SEM micrographs showed that the surfaces are smooth, uniform and well covered with the material. The EDAX analysis showed that the films are deficient in oxygen. Indirect optical bandgap energy and Urbach tailing in the bandgap was observed, and the width of the tail, which is related with disorder and localized states, was estimated.IntroductionTin oxide is an n-type wide bandgap semiconducting material with a direct bandgap energy of 4 eV and an indirect bandgap of 2.6 eV [1], where inherent oxygen vacancies act as an n-type dopant [2], Tin oxide thin films have been used for transparent electrodes in photoelectric conversion devices namely amorphous silicon solar cells, liquid crystal displays, gas discharge displays, etc. [3]. Perfectly amorphous thin SnO2 films show good electrical response to reducing gases in air and could, hence, be applied to construct semiconductor gas sensors where the metal oxide films function as a monograin-eqivalent active layer [4]. Amorphous SnU2 can also be used in extended gate field-effect transistors (EGFET) as a pH sensor, where the sensitive part is made of the SnO2/Al structure. This device can be used to detect and to quantify any kind of substance that can produce or consume protons, like an enzymatic reaction, therefore showing a large range of applications as biosensors [5].There are different methods to prepare SnO2 films, such as atomic layer deposition (ALD) [6], reactive magnetron sputtering [7], chemical vapor deposition [8, 9], dip coating [10], spray pyrolysis (SP) [3, 11-14], and evaporation [8], The thermal evaporation method was chosen to produce SnO2 thin films in this work because deposition by this technique does not present any compositional problems. In addition, it is a low temperature technique, which increases the probability of producing amorphous films. To increase this probability, the films were deposited at ambient temperature."

Jan 1, 2012

By Sergio N. Monteiro, Artur C. Pereira, Foluke S. de Assis

Jute fibers are among the lignocellulosic with great potential for use in polymer composites. In this work, polyester matrix composites incorporated jute fabric were investigated for their flexural behavior. Specimens with up to 30% in volume of jute fabric were bend-tested until rupture. The results showed an increase in both the composite mechanical strength, principally to a polyester composite reinforced with 30% in volume of jute fabric. A fractograph analysis by SEM disclosed a moderate adhesion mechanism between the jute fabric and the polyester matrix. This mechanism is apparently responsible for the improved performance of the composites.

Mar 1, 2018

By M. J. Adam

The U.S. Bureau of Mines has investigated the partitioning of complex minerals to simpler phases using sulfidation reactions for selective extraction of mineral values. This report describes research in which thermal processing of the complex Ti-bearing mineral ilmenite (FeTi03) resulted in partitioning of the valuable Ti metal to the simpler compound rutile (TiO2). Samples of ilmenite were blended with elemental S for thermal treatment at various temperatures under controlled atmospheres in an effort to dissociate the Fe from the ilmenite complex. Product characterization revealed that the Fe was partitioned 'from the ilmenite, forming a rim of pyrrhotite/pyrite (FeS/FeS2) on a rut il e core. The products were agate milled and then subjected to cursory magnetic and flotation techniques in an attempt to physically separate the partitioned phases. Partitioning results and phase concentration data are reported relative to thermal treatment variables and physical separation techniques.

Jan 1, 1991

By Fernanda de Paula, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Carlos Maurício. F. V, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Jan 1, 2015

By Guo Xueyi

The morphological characteristics of the nickel particles electrodeposited from chloride dominant aqueous solution was investigated. The effects of the electrolyte constituents, the parameters for the electro-deposition on the morphology of the nickel particles were addressed. It is evidenced that not only the particle size but also the morphology of the deposited nickel particles strongly depend on the electrolyte constituents and technical operation conditions. The electro-crystallization mechanism of the metallic nickel particles deposited at high current density was elucidated. The ultra-fine nickel particles with flake, nodular or dendrite shape may be produced by controlling the duration for electro-deposition.

Jan 1, 2003