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By Ricardo Melamed

Metallic mercury has been extensively used for gold recovery. Although the solubility and mobility of metallic mercury is low, this metal can undergo many transformations, leading to mercury contamination in humans. The complexity of Hg chemistry in the environment reflects its different possible oxidation states and species, with different physical-chemical properties. The interaction of Hg in the terrestrial system, as well as in the aquatic environment, is important to understand the mercury cycle. This paper reports data on the adsorption of Hg onto an Oxisol soil. Results show that the interaction of Hg(II) at the soil-solution interface depends strongly on ligand concentration in solution, which can affect Hg mobility. The presence of the chloride anion in solution increases the mobility of Hg(II) through the soil, due to a relative lower affmity of mercury chloride at the oxide surface. In the absence of chloride, Hg(II) form strong complexes with the surface, and its adsorption behaviour is similar to the adsorption of other hydrolizable cations.

Jan 1, 1996

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 C. -S. Jiang

In most copper refineries, addition agents are added at predetermined rates with no further monitoring of their activity or concentration in the electrolyte. Increasingly stringent cathode quality requirements, and a desire for better process control in tankhouse operations, have recently directed a number of refineries to search for a better addition agent control strategy. Extensive development work has been carried out at the Noranda Technology Centre for the monitor in of glue and thiourea in copper refinery electrolyte using cyclic voltammetry (cv~. Data from both synthetrc and commercial electrolytes are presented, showing the ability of CV to produce reliable and easily identifiable fingerprints of addition agent concentrations in copper refinery electrolyte.

Jan 1, 1991

By R. M. Reynolds

Engitec Impianti, S?.p.A. of Milan, Italy has successfully designed, constructed and has in operation state-of-the-art battery breaker systems at two European locations. A third facility i:s partially completed in Toronto, Ontario, Canada. The CX system crushes whole batteries, separates the various components and desulfurizes the battery paste. The system also produces sodium sulfate from the sulfuric acid and lead sulfate contained in the batteries. Actual plant operating data indicates that the desulfurized paste contains less than 0. 6 percent sulfur and less than 0. 5 percent antimony. The CX system utilizes mechanical screening and an up-flow hydrodynamic separator to accomplish the component separation. Sodiwn hydroxide or sodium carbonate is used for desulfurization. The sodium sulfate brine is evaporated and crystallized to produce clean anhydrous sodium sulfate suitable for use by detergent or glass manufacturers. Plant data also indicates that an increase in furnace productivity of about 25 to 30 percent is achieved using feed from the CX system. The desulfurized paste is very suitable for electrolytic processing as an alternative to pyrometallurqical processing.

Jan 1, 1990

By Rui Mao, Ke-Xin Nao, Jian-Liang Zhang, Xiang-Nan Xu, Meng-Fang Wei

"In this research, fundamental characteristics of dust and sludge containing iron from the dusting system of sintering process, blast furnace, oxygen converter and rolling process in steel enterprise were studied by chemical analysis, X-ray diffraction analysis, optical microscope analysis, scanning electron microscopy analysis, particle size analysis and other analysis means. Development direction of resource utilization for dust and sludge containing iron from steel enterprise was put forward on the basis of above study.IntroductionDust and sludge containing iron for steel enterprise mainly come from the dusting system of sintering process, pelletizing process, blast furnace, oxygen converter, rolling process and other related process. Iron content of dust and sludge is between 30% and 70%, and they also contain certain content of carbon, calcium oxide, magnesium oxide and harmful elements [1-3]. Output of dust and sludge is determined by raw materials conditions, technological processes, equipment configuration and management level. Dust output in sintering process accounts for about 2% to 3% of the sinter production, while dust and sludge from iron making and steel making process respectively take up 3% to 4% of hot metal and crude steel production, and the solid waste from rolling process accounts for about 0.8% to 1.5% of the output of rolled products [4,5]. Dust and sludge contains Fe, CaO, MgO, C and other valuable resources, it will not only result in the waste of resources, but also cause serious pollution to environment ifthe dust and sludge are not recycled. China's crude steel production in 2012 is about 700 million tons and output of dust and sludge containing iron is nearly 60 million tons, so, it is of great significance to have a resource recycling for dust and sludge containing iron from steel enterprise."

Jan 1, 2014

By Kevin Trumble, David Johnson, Kyungjean Min

The electrolytic manganese dioxide (EMD) production through electrodeposition from manganese nodules by reduction leaching in H2SO4 medium using sucrose as reductant followed by purification through 2-stage precipitation methods is described. The purified leach liquor was the starting solution for electrodeposition. Influence of in situ addition of a cationic surfactant Cetyltri-methylammonium bromide (CTAB) (0–500 mg dm −3) on the surface morphology and electrochemical properties of the EMD was examined. The XRD patterns of the deposited material were indexed to the c-MnO2 phase. FESEM results demonstrated that in the presence of CTAB uniform nanofibrous type grains were formed. Higher concentration of CTAB in the electrolytic bath however, drastically decreased the current efficiency (CE) and increased the energy consumption (EC) during electrodeposition. Under the optimum CTAB concentration of 100 mg dm −3 the obtained CE and EC values were 87.64% and 1.70 kWh/Kg respectively.

Mar 1, 2018

By Oscar J. Restrepo

Through reactions in solid form at high temperatures, using iron oxide (Fe3O4) and chromium oxide (Cr2O3) in fixed proportions as precursors, the compound was synthesized with spinel structure type FeCr2O4. For different temperatures synthesis was conducted the characterization of the material obtained through X-ray diffraction (XRD), spectroscopy UV-VIS-NIR, scanning electron microscopy (SEM), energy dispersion analysis of X-ray (EDX) thermal analysis (DTA / TGA) and magnetic susceptibility of alternating current. The changes in the spectra of reflectance changes are related to the phase identified, the degree of crystalline structure, the spatial order of cations and the magnetic behavior obtained.

Jan 1, 2009

By Suzanne Young

The effect of LiF additions on liqt.1id1.:1s temperature and electrical conductivity over a wide range of cryolite bath ratios (1.0 to 1.5 weight ratio) was investigated. Results did not agree with multi-regression equations reported by Dewing and Choudhary over the entire region. New regression equations were developed. Reasons? are given for the differences. The models are used to discuss the economic implications of LiF additions to Hali cell electrolytes.

Jan 1, 1985

By Gen Kamimura, Hiroyuki Matsuura, Wonjin Choi

Control of non-metallic inclusions in terms of morphology, number density or composition is essential to produce steel products having the desired mechanical properties.Though many studies have been conducted to clarify various properties and evolution mechanisms of inclusions at steelmaking temperature, it has been reported that the states of inclusions in final products are significantly different from those in crude steels for some steel grades. The present study has focused on the evolution of oxide and nitride inclusions in solid Fe–Al–Ti–N alloys during heating to increase the understanding of inclusion evolution in a simplified metal system. Compositional and morphological change of initial inclusions, as well as precipitation and growth of new inclusions have been observed even when the alloy was in a solid state.This behavior has been observed due to the change of thermodynamic stability and solubility of existing phases in inclusions.

Mar 1, 2017

By Yong J. Kim, J. M. Park

"Solid/melt interface shape during continuous casting process has a strong influence on the resulting microstructure of the ingot. The interface shape is primarily governed by the heat flow condition between the molten metal and mold (or container). The roll of the microstructural transition resulting from various solid/melt interface shapes is discussed using the Sn-22.6wt%Pb alloy. Three different types of mold such as cold mold, resistantly heated mold, and electromagnetically heated mold were used to generate those interfaces having different curvatures. Experimental measurements of complete temperature profile along the axis and surface of the ingot during downward continuous casting are presented to determine the solid/melt interface geometry. The results provide an explanation of the ingot property with emphasis on microstructure.IntroductionA large scale of continuous casting process of alloys often has a rather deep V channel type of solid/melt interface resulting from a limited heat flow condition. As a result, the deep V type solid/melt interface shape entraps defects such as pores and inclusions and also creates canter segregation. In order to reduce the defects concentration, electromagnetic stirring(EMS) mechanism has been applied to the melt in the channel[l]. Speith and Bungeroth introduced first experimental EMS device to the continuous caster in 1952.[2] Today, with wide ranges of benefit, a large variety of such technique is available. Electromagnetic field on the melt can be divided into three aspects. First, eddy current is induced on the metal surface by alternating magnetic field with high frequency, which results in heating the metal. Second, electromagnetic body force which is generated by the magnetic field and the eddy current reduces the melt pressure on mold or support the melt not to contact with the mold[3,4,5]. This force is used for electromagnetic casting process(EMC). Finally, it causes stirring in the melt. Many research efforts have been done on the EMC process to improve surface quality of slab[6] and control meniscus shape where three phases such as melt, solidified metal, and mold powder coexist[7,8]. However, the eddy current heating effect on the surface of the ingot was less considered. It is worth noting that induced eddy current on the surface of slab melts the solidified shell and thus changes the heat flow condition between the mold and melt. Mold heating effect was first proposed by A. Ohno[9] and its processing conditions were identified in details[ 10, 11]. The so-called Ohno process is based on the fact that by keeping the mold temperature slightly above the melting temperature of the liquid, no grain can be nucleated on the mold wall[12]."

Jan 1, 1998

By W. D. Cho

The slag chemistry in steel processing plays an important role in terms of the removal of impurities including alumina particles. In the present study, the dissolution of solid aluimina particles in CaO-based fluxes at the temperatures between 1450 and 1550 °C has been investigated to determine dissolution kinetics and mechanism. Alumina particles were added directly in the slags and the size of alumina particles was measured as a function of time using optical and scanning electron microscopes. The dissolution rate has also been obtained as a function of Si02, CaF2, MgO and MnO contents in the slags. The diffusion boundary layer between alumina and bulk slag phase has been observed and analyzed using SEM and EDX. In addition, some experiments have been performed for the dissolution of alumina in BaO-based fluxes.

Jan 1, 2003

By Xinlei Jia, Wenming Guo, Yanling Zhang

A large amount of stainless steel dust rich in Fe, Cr, and Ni has been being generated in China. Smelting treatment is accepted as a practical method for the recovery/reutilization of these second resources, during which Fe, Cr, and Ni is reduced into one metal phase and then separated from the residue slag. Based on the typical compositions of stainless steel dust, the residual slag can be termed as CaO-SiO2-MgO-Al2O3 system. In this paper, the activity coefficients of Cr in Fe-Cr-Ni-C (-Si/Al) melt and the properties of CaO-SiO2-MgO-Al2O3- 1%CrO system thermodynamically approached. Then, in laboratory experiments, the recovery ratios of Cr and its distribution behaviors between Fe-Cr-Ni-C melt and CaO-SiO2-MgO-Al2O3 slag system were examined.

Jan 1, 2015

By Chuanguang Bi, Wenbin Dai, Hongtao Wang, Mansheng Chu, Zhenggen Liu

Coke oven gas (COG) injection is considered as one of feasible measures to reduce carbon emission of BF. The effects of COG injection on the reduction of iron-bearing burdens were numerically simulated by means of multi-fluid BF model, which revealed that with increasing COG injection rate, solid temperature gradually decrease, in-furnace H2 concentration increases, the reduction of magnetite and wustite by H2 is evidently accelerated, the reaction rate of wustite by H2 reduction is enhanced and the reduction degree of mixed burdens is strengthened. Under this hydrogen-enriched condition, metallurgical properties of iron-bearing burdens were experimentally investigated. The GB/T13242-91 test results showed that with increasing COG injection rate, the reduction swelling index of oxidized pellets decreases while the reduction ratio of pellets increases. The softening-melting tests suggested that softening interval of mixed burdens increases from 163.6 to 228.3 °C while melting interval decreases from 147.3 to 92.4 °C. The cohesive zone moves downwards and becomes narrow. The permeability of mixed burdens is improved. In terms of metallurgical properties of iron-bearing burdens, COG injection benefits to improve BF performance.

Mar 1, 2017

By Uchil Jayagopal, M. Krishna, P .. V. Krilpakara, S. Manjunath

"There have been a pioneering efforts over the last forty years in the development of metal matrix composites (MMCs) as a new engineering materials, having improved properties, light weight characteristics and competitive costs compared to traditional materials. Following recent advancements in casting technology and the use of melt stirring device by foundries, discontinuously reinforced MMCs where prominent alloys are reinforced with particulates or short fibres and the being employed ·in the production of castings targeted for automotive and aerospace application.The ZA-27 alloy has a high strength compared to zinc or alluminium alloys with a lower melting temperature. The main objective of the present research is to study the effect of quartz particles on the mechanical behaviour of ZA-27 alloy composites. The results showed that the ultimate tensile strength, hardness, Young's modulus of the composite gradually increased with increase in the weight percentage of the quartz reinforcement. However overall ductility decreased with an increase in quartz reinforcementIntroductionMetal matrix composite (MMCs) offer outstanding benefits as they combine metallic properties with ceramic properties there by yielding improved physical and mechanical properties.1Among the various type of MMCs particulate reinforced composite are the most versatile and economical2. By suitable choice of metal matrix and particulate system a wide range of properties combination can be obtained such as strength, modulus, fiiction.al resistance, tribological performance and machinability. These composites are capable of replacing conventional alloys in a considerable range of applications. They also offer significant saving in energy and resources"

Jan 1, 2000

By Qian Xu, Xionggang Lu, Xingli Zou, Zhongfu Zhou, Shuhua Geng, Hongwei Cheng

Herein we report an electrochemical route from oxides (SiO2, TiO2)/sulfide (MoS2)/carbon mixture precursors to Mo-Si-Ti-C composites in molten salt. The electrochemical process was carried out in molten CaCl2 at 800 °C with a potential of 3.1 V, and a graphite-based anode was used in the electroreduction process. The reaction mechanism and the influences of the stoichiometry of the initial mixture precursor on the morphology and phase composition of the final products were investigated. It has been found that Mo5Si3/MoSi2/Mo3Si/Mo, Mo5Si3/MoSi2/Mo2C/SiC, and Mo5Si3/Mo2C/Ti3SiC2/TiC/Mo composites can be electrosynthesized directly from their oxides/sulfide/carbon mixture. The preliminary experimental results suggest that the electroreduction process can be used for the controllable electrolytic production of alloys/carbide-containing composites from oxides/sulfides/carbon precursors.

Jan 1, 2016

By Jewel Gomes

Produced water (PW) is salty water trapped in the reservoir rock and brought up along with oil or gas during production. It subsists under high pressures and temperatures, and usually contains hydrocarbons and metals. Therefore, it must be treated before being discharged to surface water. Different techniques are being used to treat PW through phase separations, system control and design, and chemical treatments. In this paper, we discuss our experimental results on treating PW through electrocoagulation (EC). The performance of EC was investigated for the reduction of chemical oxygen demand (COD) and metal ions. Effects of different electrodes, residence time, current density, and pH were also studied to optimize the treatment conditions. Different kinds of cleansing agents, such as lime and borax were used to break the buffering effect encountered during treatment. FTIR, SEM/EDS, and XRD were used to characterize the EC-floc and thus to elucidate removal mechanisms.

Jan 1, 2009

By Anna Wasilkowska

The study concentrates on the effects exerted by microstructure, deformation history and uniaxial stress conditions (temperature, stress state, strain rate) on the mechanical properties offerritic TRIP-aided steels for automotive applications. In low-alloyed TRIP-steels it is quite difficult to separate the effect of the austenite to martensite phase transformation from the influence of the ferritic matrix contributing to the yield stress and uniform elongation. Investigation of transformation kinetics of retained austenite as a function of the deformation temperature show that using the parameter k to characterize the retained austenite stability allows to identify regious of different temperature sensitivity separated by a transition temperature of 10±5°C. The observed low strain-rate sensitivity of the flow stress is an intrinsic property of the ferritix matrix and points to defomtation governed by slip. The ultimate tensile strength is much stronger affected by temperature than the yield stress. The influence of the temperature on the elongation is complex, because of the heating of the specimens by 60-l20°C at moderate and high strain rates. The increase of the total strain can be understood in terms of thermal softening of the ferrite. On the other hand, the steep increase of the stress during dynamic testing is an effect of accommodated elastic and plastic strains in the matrix. The strain- hardening exponent is dependent on the conditions imposed during testing. The martensite transfomtation rate is lower and the critical stress for martensite nucleation is much higher under compression compared to tensile loading. In secondary tensile tests, the yield stress increases steeply, and the ultimate tensile strength and the total elongation depend linearly on the amount of pre-straining. The results confirm that in the range of 8=10-4 s-l the TRIP-effect governs room temperature plasticity. Keywords: TRIP-steels, mechanical properties, strain rate sensitivity, temperature sensitivity, austenite stability

Jan 1, 2003

A study was undertaken to remove the Se from waste solutions using a raw form of the biomass called Iota Chips derived from the seaweed, Eucheuma spinosum. Removal of Se from solutions was investigated as a function of time, pH, conc. of Se in solution (0.1 to 100 ppm) and lota Chips to liquid ratios of 10-2 to 10-5. For solutions containing initial conc. of 0.1 ppm Se, with the addition of Iota Chips at a solid to liquid ratio of 10-3, the Se conc. decreased to 0.03 ppm in about 3 hours. Iota Chips absorption capacity to the Se and its application to the treatment of the metallurgical processing effluents are discussed.

Jan 1, 1992

By Yong Hack Lee

Nonferrous smelting processes have been through a rapid transformation since the beginning of 1980. The copper smelting technology has changed from the conventional Blast Furnace process to the Flash Smelting and MIB process. In the field of lead smelting, the technology has changed from the Blast Furnace Smelting to the Direct Smelting such as QSL and KIVCET. In 1992, Onsan Refinery successfully commissioned Direct Smelting QSL technology for lead. The QSL could produce more than 160,000 ton per year of lead bullion from lead concentrate and various residues. Moreover, since the year 2000, the TSL (Top Submerged Lance) Technology utilizing the same Direct Smelting process has been successfully commissioned to treat lead concentrate as well as lead sulfate residue produced from a hydrometallurgical zinc plant. This paper presents and compares the energy flows of lead smelting processes such as a conventional process and the Direct Smelting Processes plotted on the Pb-O-S phase diagram. The oxygen potential diagram suggests how to control the oxygen potential in the fum ace. Also, it describes the recent operational experience in the TSL plant of Onsan Refinery with necessary mass balance of key elements.

Jan 1, 2003

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-Al2O3 based slag melted in a MgO crucible at 1873 K under controlled Pso2 of 10.1 kPa and Po2 in a range between 2.5x 10-and 10.1 Pa by using CO-CO2-SO2 gas mixtures. The content of nickel in the slag at Po, of 10.1 Pa, above which solid NiO is expected to precipitate in the equilibrium state, was found to be 4, I mass% and the contents of sulfur and oxygen in the nickel melt were 0.4 and 02 mass%, respectively. ft 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-Al2O3 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