Search Documents

By Bowen Li

Copper vermiculite is a special nanomaterial with excellent antibacterial and antifungal performance. By means of ion exchange, copper vermiculite containing up to 5.8wt% copper was prepared. The chemical and mineralogical characterization of the material was investigated in this study based on the XRD, AAS, TEM and EDS analysis, as well as the calculation of crystalline parameters and crystal chemical formula. Cu2+ and Mg2+ have similar atom radius and same electrovalence. Correspondingly, the structure character of copper vermiculite is very close to that of standard Mg-vermiculite. Most of the CU21 may have occupied the interlayer cationic positions in the form of hydrate in vermiculite. However, some may have entered into octahedral coordinate positions. The values of au and bo of the copper vermiculite crystal cell have no obvious change compared to that of original vermiculite micropowder, but the Co value decreased slightly, which is desirable for the stabilization of the Cu2+ in copper vermiculite.

Jan 1, 2003

By D. Majuste

This paper describes an experimental approach to evaluate the effect of organic impurities or even additives on metal electrowinning and product quality. In addition to electrowinning tests and electrochemical measurements, the approach includes organic analysis by Fourier Transform Infrared spectroscopy and gas chromatography; video monitoring of the reaction interface; and product characterization by using scanning electron microscopy, crystallographic texture and bending tests. The mechanical behavior of metal cathodes was assessed with a customized bending device that is able to bend the cathodes up to angles similar to that of the stripping machine. In this work, the effect of a potential organic impurity, lubricating oil, on the production of electrolytic zinc is taken as a case study. The findings of the investigation allowed a better understanding on the role of this organic on energy consumption and product quality and a qualitative prediction for the behavior of Zn cathodes during the stripping operation. Simple control and optimization procedures resulted in significant energy savings.

By N. Pradhan, B. K. Mishra, B. D. Nayak, B. K. Mohapatra, R. K. Mohapatra

"Present study is about use of a group of Iron[Fe(III)] Reducing Bacteria (IRB) to convert the goethite (a-FeOOH) present in the original lateritic Nickel ore to magnetite under an anaerobic condition and subsequently release the bound Co(III) and Ni(II) through leaching. The lateritic Nickel ore contains 0.8% Ni, 0.049% Co, 1.92% Cr, 0.32% Mn and 50.2% Fe. An anaerobic dissimilatory Fe(III) reducing bacterial consortium capable of using acetate as carbon source (electron donor) and lateritic ore as terminal electron acceptor, changes the initial light brown color of the ore to dark brown. The change in color is due to the conversion of goethite to magnetite, which was confirmed by XRD. When the IRB treated sample was subjected to both bioleaching and acid leaching, it shows a greater recovery of Nickel and Cobalt values as compared to untreated original lateritic Ni ore. Further a magnetic separation method was used to separate the magnetic part of the treated lateritic ore and subjected to acid- and bio-leaching for better recovery of Nickel and Cobalt.IntroductionIt has been known that micro-organisms have the potential to reduce metals but more recent observations have shown that a diversity of specialist bacteria and archaea can use such activities to conserve energy for growth under anaerobic conditions [12]. Natural Fe(III) oxides are high in surface area and are reactive [1]. Fe (III) oxides adsorb a wide range of metal cations and anions by complexation to surface hydroxyl groups [17], and function as the primary redox buffering solid phase in many sediments and subsurface materials [5].Recently a number of bacteria have been isolated based on their ability to use metal ions, including Fe(III), as electron acceptor under anaerobic conditions. These are capable of producing energy by coupling the oxidation of organic compounds to reduction of Fe(III). Iron[Fe(III)]-Reducing Bacteria (IRB) have been isolated and identified from a wide variety of environments including freshwater and marine aquatic sediments and submerged soil [8]. The biogeochemical cycle of iron is linked to those of the trace metals, as many trace metals coassociate with Fe(III) oxides or reduced iron phases (e.g., magnetite, siderite, or iron sulfide). IRB can utilize Fe(III) oxides as terminal electron acceptors for respiration [18]; thereby reducing all or a fraction of the solid. The reductive portion of the iron biogeochemical cycle in non-phototropic environments (e.g., sediments and subsurface materials) is driven by the direct enzymatic reduction of Fe(III) oxides to Fe(II) by dissimilatory iron reducing bacteria [13,14]."

Jan 1, 2009

By Mark Tjerkstra

In ,1993, the WMC Resources Ltd.-owned Kalgoorlie Nickel Smelter, underwent a capacity upgrade. This capacity increase was offset by .air quality control restrictions limiting the smelter's availability to 80%. As the direct. result of this limitation, WMC Resources Ltd commissioned a double absorption contact ,acid ,plant for the desulphurisation of furnace waste gas in August 1996. The history and the impact of the acid plant on S02 emissions and air quality is reviewed. General descriptions of the other aspects of the Kalgoorlie Nickel Smelter's Environmental Project are also included in the paper. Information on 'the design features? and operating practices that relate to or contrast with practices at operations visited by KNS personnel prior to acid plant commissioning provide the paper's focus. Smelter operation has changed markedly from unstable operation prior to 1997 to continuous" operation with little down time due to mechanical or process failures resulting in increased smelter availability to more than 90%

Jan 1, 1998

By Larry M. Southwick

Steel mill electric arc furnace dust is a RCRA listed hazardous waste and its treatment and/or disposal are regulated by a complex set of rules. These regulations were originally established to encourage recovery and recycling of valuable components. For EAF dust, the more valuable constituents include zinc, lead, cadmium and iron. In fact, current trends are in the opposite direction, as the regulations have complicated the ability to commercialize new treatment technologies and created substantial roadblocks and liabilities for processors. As a result, almost half of the EAF dust generated in 1997 will be landfilled. The problems are compounded by difficult processing requirements, less than sterling examples of technology development and mechanical and operating problems. This paper explores some options to simplify the processing requirements and thereby easing difficulties in commercializing new technologies and expediting the recycling of recovered metals. Dust processing usually includes a simple step followed by two complicated steps. The simple step is fuming of heavy metals away from iron and other residues. The complex steps are (1) separating and purifying the heavy metals and (2) upgrading the iron residue. The first complex step can be simplified by producing an intermediate product that is amenable to processing by zinc refiners. This route benefits from the currently underutilized (by dust processors) resource offered by refiners, who have experience in and existing processes for separation and purification of zinc-based heavy metals. Various processes and their associated product options are reviewed and compared. Future directions for dust processing developments are suggested.

Jan 1, 1998

By Batric Pesic

Calcium silicate slag (Di-Cal) and magnesium oxide condensate (MgO) are the by-products of magnesium smelting operations, As these oxides have acid neutralizing and metal precipitating properties, it was decided to examine their reactions with (a) individual heavy metals and (b) with a mixture of metals in solution, The resulting solid reaction products were further tested with respect to the stability of the contained metals, The stability of the solid precipitates were examined as a function of the method of precipitation and as function of the solution pH With respect to the method of precipitation, the performance of Di-Cal and MgO was compared to the performance of lime, an industry standard for heavy metal precipitation, Four different pH solutions (4,0, 5,0, 7,0 and 1 LO) were used to study the effect of pH on the stability of the precipitates. It was found that Di-Cal, in most cases, produced the most stable precipitates and thus, outperformed lime, Metal precipitates prepared by the addition of MgO were the most soluble for each metal studied, except for Se,

Jan 1, 2001

By Rajesh Kumar Mishra

About 500,000 troy ounces of Platinum Group Metals (PGM) will be available for recycling each year from spent automobile catalytic converters in North America alone. Platinum Group Metals? from spent catalyst can be extracted by Hydrometallurgical, Pyrometallurgical or Gas Phase volatilization processes. This paper is a review and comparative study of various processes investigated for PGM extraction. A number of processes described in this paper have already been commercialized. The technical and environmental aspects of the important processes are discussed.

Jan 1, 1989

By SIMON TIMBILLAH

The chalcopyrite-molybdenite (Cu-Mo) flotation industry is increasingly turning to organic depressants as suitable replacements for inorganic reagents, such as NaHS, due to environmental and safety concerns as well as high consumption rates of the inorganic reagents. This presents an opportunity for improvements or design and synthesis of alternative reagents. Disodium carboxymethyl trithiocarbonate (Orfom® D8) depressant is an organic depressant with a carboxylate group on one end and a trithiocarbonate group at the other end. Fundamental results are shown regarding the interaction of the Orfom® D8 depressant in the bulk flotation of a Cu-Mo concentrate from an operating North American mine. Cyclic Voltammetry on pure copper and Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) measurements on pure chalcopyrite with Orfom® D8 depressant treatment are also reported. Through such characterization techniques a potential adsorption mechanism of Orfom® D8 on the mineral surface was identified and its depressant characteristics in the Cu-Mo flotation systems explained.

By David Melgaard

A significant emerging recycling, waste minimization problem stems from legacy waste from the nuclear weapons program and from production of power using nuclear fuel. Premium quality metals used in nuclear plants become contaminated, making them unsuitable for reuse. Consequently, decontamination studies were conducted to evaluate the decontamination capacity and partitioning effeetiveness of Electroslag Remelting (ESR). Eight laboratory melts were conducted to evaluate the efficacy of using ESR to transport radionuclides from the liquid metal phase to the liquid flux or slag phase. To determine the decontamination effectiveness, several surrogate compounds for uranium, plutonium and other fission products were added to the melts. During the melts, the melting rate was varied, typical slag additives were used, and two different slag compositions were evaluated. The resultant post-test ingots and slag were then analyzed to determine the partitioning of the surrogates. ESR generally proved very effective in removing contaminates from the metal with a few noted exceptions. -

Jan 1, 2003

By Chris Twigge-Molecey

As emission constraints for metallurgical plants become more difficult to meet; control of major, multi-vessel, flue systems become more critical. Control instabilities can result in significant loss of system capacity or emissions to the environment. This paper will discuss the use of dynamic simulation techniques to optimize both the design and control strategies for these systems. A significant ,safety hazard is associated with pressure excursions from process upsets or equipment failures. Pressure rise rates of up to 10 kPajsec can occur. These cannot-be followed by conventional controls. Fail-safe high speed venting is required to protect both the furnaces and operating personnel'. Design options, sizing techniques and practical problems are discussed.

Jan 1, 1992

By Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes are considered one of the most promising alternatives to well- established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic- containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (DoD). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003

By Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes? are considered one of the most promising alternatives to well-established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic-containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment-technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (000). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003

By D. H. Magoon

The zinc smelter of Cominco Ltd. at Trail, B.C. Is the largest In the western world. A total of 550.000 tonnes of concentrate are proceed at the smelter annually. Approximately 80% of the zinc concentrate is roasted and the remainder Is treated by aqueous oxidation preaaure leaching. The zinc concentrate roasting and sulphur dioxide gas processing plants have undergone many changes over the years. This paper describes the processes and equipment currently used for concentrate roasting, S02 gas cooling and cleaning, mercury removal, sulphuric acid production liquid S02 production, and tall gas S02 scrubbing. The recent Installation of an advanced process control system for the operation of these Integrated processes Is also described.

Jan 1, 1990

By Guanghui Li

In the paper, the recovery technology of gallium from zinc-leaching residue by cold-bonded coal-based direct reduction process following magnetic separation was developed. The results show that the scattered metal Ga can be concentrated obviously after the reduction of zinc-leaching residue briquette and magnetic separation of reduced product. At the same time, the volatilization of Zn in the residue is enhanced during the reduction. When the residue, bear¬ing 18.60% Zu.21.18% Fe and 527 g/t Ga, was reduced with coal at 1100°C for 150 min, the results of Zn volatilization of 9842% and Ga recovery of 89. 10% were obtained in reduction. After magnetic separation of the reduced product, the concentration of Ga in sponge iron is 2164 g/t, and the separation recovery of Ga reaches 92.42%. The enriched mechanism of Ga during reduction -separation process was studied by using electron microscope, scanning elec¬tron microscope, energy spectrum and mineralogical analysis. The investigations show that there is no formation of independent phase of Ga during reduction process. The Ga occurs mainly in metallic iron phase (the concentration of Ga in metallic iron phase is 0.04%-0,4%), in addition, there exists a little Ga in poorly crystalline sulphide (o.08%-0./5Y& Ow). But Go does not exist in most of glass and silicate phase. The affinity of Ga for metallic iron is the enrichment basis of Go in reduction, and it is also in favor of recovering Go during magnetic separation. Key Words: Gallium Zinc-leaching Residue Cold- Bonded Direct Reduction

Jan 1, 2003

By Edward Rosenberg

The synthesis and characterization of silica polyamine composites modified with a variety of sulfur containing ligands is described. The two most successful ligands in terms of sulfur in-corporation and mercury capture are ethylene sulfide and carbon disulfide. The ethylene sulfide forms either an amino mercaptane or a polysulfide upon reaction with amino groups on the composite. The carbon disulfide undoubtedly forms a dithiocarbamate functional group upon reaction of the amino group under basic conditions. Both materials posses excellent capture kinetics and capacities for mercury, Once captured, the mercury is extremely difficult to remove from the composite materials, even with concentrated acids, and they easily pass the TCLP test. The materials are compared with related thioether modified silica polyamine composites and appropriate potential applications are discussed.

Jan 1, 2003

By John J. Mortvedt

Application of some by-products of the metals industry which contain plant nutrients to agricultural lands could constitute resource recovery instead of costly disposal. Some industrial by-products contain appreciable concentrations of heavy metal contaminants, such as Cd, Cr, Ni, and Pb. After land application, these metals may be absorbed by plants and enter the human food chain or be leached to groundwaters. Plant uptake of these heavy metals varies with plant species:, soil pH, soil texture, and the particular metal. Certain leafy vegetables can absorb significant amounts of heavy metals, while absorbed metals are usually poorly translocated to cereal grains. Allowable heavy metal concentrations in fertilizers now are not regulated, but EPA is considering such regulations. Heavy metal impurities in animal feed supplements are regulated by the states; so some by-products may not be permitted for this use.

Jan 1, 1992

By Michael S. Moats, Scott C. Campin, J. Brent Hiskey

"Electrochemical techniques are a valuable means of analyzing the passivation of commercial copper anodes. Electrochemical impedance spectroscopy (EIS) provides information concerning transport and reaction phenomena occurring at an electrode surface. Commercial. copper anodes of varying compositions have been examined using EIS. Experiments were conducted in a flat cell with an electrolyte of 40 gil Cu2 + and 160 gil H2S04 maintained at 65 DC. Impedance spectra were obtained at the potentials characteristic of the open circuit voltage and passive region for each anode. The spectra of the passivating films exhibited a flattened resistive/capacitive loop at middle to high frequencies and an inductive loop at low frequencies. An equivalent· circuit utilizing an inductor-resistor series in parallel with the double layer capacitance and charge transfer resistance was adequate in modeling the impedance data. The influence of anodes impurities on the components of the equivalent circuit is discussed and correlated with a hi-layer passivation model.IntroductionPassivation of copper anodes during industrial electrorefining has received considerable attention in the past few decades. Great strides have been made in understanding the roles of anode impurities [1-25], electrolysis parameters [20,26], and electrolyte chemistries [20,26]. Even so, passivation still occurs even in the most modem of refineries. The exact cause of passivation is not fully understood. It is known that the anode surface becomes covered by a passivating film. This film has been proposed to be CuS04'&5H20, Cu20, or mixed oxides. The localized concentrations of Ft, Cu+, and Cu2+ ions determines which phase is more favorable. The presence of these ions is controlled by the reaction kinetics and diffusion of species through the slimes layer.Reaction kinetics between Cu, Cu +, and Cu2+ are based on the dissolution mechanism of copper. There exists four different models to describe the dissolution of pure copper. The classical model of Mattsson and Bockris [27] involves two single electron transfers with the cuprous-cupric reaction being the rate detennining step. More recently, Wong, Collier, and MacFarlane [28] used ac impedance to elucidate a more complex mechanism involving the affect of pH and anions. Their findings indicate that the formation of cuprous ions in solution, Cu(I)so~ is favored over Cu(1I) ions adsorbed to the electrode surface in the presence of sulfate and as pH increases from pH 1 to pH 5."

Jan 1, 1997

By Vinay Kumar, Manis Kumar Jha, J. Rajesh Kumar, Archana Kumari, Rekha Panda, Jin Young Lee

Rare earth metals (REMs) play a significant role in the manufacture of permanent magnets, fluorescent lamps, catalysts, medicines, super alloys etc. Recently, China, which controls 97% of world trade in REMs, imposed restriction on its export. Consequently, the global demand of REMs is escalating and is expected to exceed the supply by 40,000 tonnes annually. Present review paper reports the flow-sheets of commercial processes based on pyro-hydro and hybrid techniques as well as systematic research for process development to recover REMs from primary and secondary resources. This review paper also reports the recommendation and future prospective to fulfill its demand and supply gap keeping in view environmental prospective.

Jan 1, 2014

By Brajendra Mishra

Molten Salt electrolytic processes offer unique opportunities to extract and refine metals where gaseous or metallothemlic reduction, hydrometallurgical extraction and aqueous electrolytic methods are thermodynamically constrained. Production of aluminum and magnesium by molten salt electrolysis are well known commercial processes. Several other reactive metals, such as lanthanides and actinides, as well as beryllium and calcium, make use of molten salt processing for extraction and refining. This presentation describes the science of molten salt chemistry and electrochemistry for winning and refining of several metals. In addition, recovery of metals from waste process salts by molten salt reduction as well as oxidation have been discussed. Material issues in design of molten salt reactors have been included. Various applications have been presented through case studies. Experimental data have been included to justify the suitability as well as limitations of these specific processes.

Jan 1, 2003

By Zhihua Wang

Through metallurgical calculation and process analysis based on metallurgical theory, it is aimed to raise the concentration of smelting oxygen and improve the update speed of reaction interface, accelerate the reaction and achieve a high-intensity smelting at the stage of converting. The PM plant has launched a theoretical research on model of high-intensity converting aiming at increasing the oxygen concentration of converting, carried out transformation of Kaldo furnace converting system, performed a series of industrial trial operations, conducted multiple rounds of tracking test and data comparison in reducing the furnace cycle, lowering the unit consumption of fuel and stabilizing the furnace lining life. The move has practically tested and verified the correctness of high-intensity smelting theory.