Search Documents

By K. Verbeken, E. Wettinck, M. Verhaege

Iron (III) can easily and selectively be removed from acidic sulphate solutions with organo-phosphoric acids like Di-2-Ethyl-Hexyl-Phosphoric Acid [D2EHPA]. Stripping of the iron (III) loaded organic, however, is difficult unless highly concentrated inorganic acid solutions are used. In this paper results are shown for the enhanced stripping of iron from loaded D2EHPA by electro-reduction. The loaded solvent is contacted with a 2 M H2SO4 solution, which is continuously recycled in an electrochemical reactor where iron (III) is reduced to iron(II). As iron (II) is not extracted by D2EHPA, the equilibrium for iron (III)- D2EHPA is shifted towards the aqueous iron (Il)-sulphuric acid solution. The electro-reduction unit is a vessel with separated catholyte and anolyte chambers. The catholyte is the actual stripping solution where iron (III) is reduced to iron (II) on a stainless steel electrode. The anolyte is a 2 M H2SO4 solution where oxygen is evolved on a lead alloy electrode. A sintered glass plug separates the compartments. With this unit, enhanced stripping of iron from the solvent is possible under mild acid conditions [2 M H2SO4], and a concentrated ferrous sulphate solution can be obtained. The results shown have mainly been obtained by studying the parameters affecting the electro-reductive stripping of a D2EHPA loaded organic phase in a batch reactor. From an iron (IH)-saturated 20 vol. % D2EHPA solvent containing ~ 12.5 g/1 Fe (III) over 90% of the iron can be stripped in one stage with a 2 M H2SO4 solution at 50°C. It is shown that in this way it should be possible to obtain a concentrated ferrous sulphate solution which can be processed downstream to recover a pure iron product.

Jan 1, 2000

By W. G. Davenport

Chapter 4 examined Inco (oxygen) flash smelting of pure chalcopyrite concentrate. It showed that the oxygen and flux requirements for auto thermal smelting are readily determined by a matrix calculation. This chapter extends this matrix approach by applying it to a multi-mineral concentrate.

Jan 1, 2001

By Dale Zacherl, Andreas Buhr, Rainer Kockegey-Lorenz

"The microporous calcium hexaluminate insulating material SLA-92 has been introduced as an alternative to refractory ceramic fiber and other insulating refractory materials. Key properties associated with this product include: high chemical purity, long term high temperature stability up to 1500 °C, low thermal conductivity up to 1500 °C, and high thermal shock resistance. The properties of the new material and various applications in the steel and ceramic industries have been reported in previous papers. The current paper summarizes the industrial application experiences with innovative refractories based on SLA- 92 and discusses potential new applications in various manufacturing as well as energyrelated industries.IntroductionSLA-92 was introduced to the refractories industry in 1998 by van Garsel, et al. [1] as a new insulating raw material for high temperature applications, followed by investigations [2] of long term temperature stability for this new lightweight aggregate up to 1500°C.SLA-92 was developed as an innovative alternative to commonly used refractory ceramic fibers. It has unique properties regarding chemical purity and mineral composition and is a microporous, silica-free calcium hexaluminate (CA6 – mineral name: hibonite)."

Jan 1, 2010

By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2SiIMgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (PIM) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2um is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ fonning process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm3 and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2Si/MgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (P/M) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2JIm is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ forming process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm) and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

By Jonkion M. Font

As a comprehensive contribution to the understanding of oxygen-blowing of matte smelting, the copper and nickel solubilities between the FeOx SiO2-MgO slag with saturated SiO2 and the Cu2S-Ni3S2 FeS matte with the NCu/(NcU+NNi) of 1, 0.75, 0.5, 0.25 and 0, in a MgO crucible were investigated at 1573 K under controlled partial pressures of SO2 at 0.1, 0.5 and 1 atm. The partial pressures of SO2, S2 and O2 were controlled by using an Ar-SO2-S2 gas mixture after passing through a sulfur reservoir. It was clarified that, at a given matte grade, the solubility of copper in the slag was independent of pso2 while that of nickel increased with increasing pso2. This notable difference was considered to be ascribable to the chemical formulas of the mono-metallic sulfides in which one copper atom combines with ½ sulfur atom while one nickel atom combines with 2/3 sulfur atom. It was also clarified that, at a given iron content in the matte, the pot and ps2 were independent of the matte species. This was ascribable to aFeS in the matte, which was independent of the matte composition, Ncu/(Ncu+NNi), at a given iron content in the matte.

Jan 1, 1999

By Shaohua Ju, Jin-hui Peng, Ya-jian Wang, Shuai-dan Lu, Li-bo Zhang, Lei Guo

"The granulation of a red mud is of great importance for recycling this material as an adsorbent for waste water or gas. A new granulating process was developed and its effect was evaluated. To reduce the cost of the granulation process, the wet filter cake (containing 25% water) was directly mixed with different cement contents (4%, 6%, 8% and 10% based on wet material). The mixtures were placed in a moist environment for 4 days, and then were washed with deionized water until the pH values of leachants were lower than 9.0. The efflorescence ratio, surface area and particle size of the aged mixture were determined, respectively, by bottle shaking experiments, N2 adsorption and screening. The results showed that the best addition of cement is 2%, and this yielded granulated material with a particle size of less than 2 mm, an efflorescence ratio of 4.83% and a specific surface area of 17.42 m2/g.IntroductionRed mud is a residue of the aluminium industry that is produced during the alkaline extraction of alumina from bauxite by the Bayer process. For every ton of alumina that is produced, the amount of red mud generated can vary from 0.3 to 2.5 tons, depending on the characteristics of the bauxite. In its typical form, red mud is brick red in colour, caustic, about three times as dense as water and, when un-neutralised, has a high pH, typically around pH 13 [1]. It is primarily composed of iron oxide, silica and alumina, along with traces of heavy metals. Red mud particles are quite small; typically 99% will pass through a 0.6 mm sieve and 87% through a 0.038 mm sieve [2],"

Jan 1, 2012

By V. Ramachandran

Over the past 20 years, water treatment plants have been built at various Asarco facilities to effectively handle the process waste streams that need to be bled from the system. The current paper review the several operations with reference to (a) waste streams processed, (b) process chemistry, (c) discharge options and recovery of treated water, and (d) sludge disposal.

Jan 1, 1994

By Huanyu Zhang, Zhancheng Guo, Liqiang Fan, Huiqing Tang

"In this study, a simple process has been developed for zinc oxide recovery from RHF (rotary hearth furnace) secondary dust. The results have shown that a high dissolution efficiency of soluble zinc was achieved with water leach at ambient temperature with a liquid/solid ratio of 10/1 in 30min while 20% of the dust was left as solid residue. The rate of dissolution increased slowly after the dissolution efficiency reached 90%. The leaching process was found to be controlled by external diffusion. After separation, zinc was precipitated in leached liquor by introducing a precipitation agent of potassium hydroxide. The resulting solid was purified and dried at 393K. Zinc powder in the form of ZnO with purity of 98.5 mass% was obtained with an average size of 12.4µm.IntroductionThe RHF (rotary hearth furnace) direct reduction process is widely used in many iron and steel enterprises to deal with various metallurgical dusts [l]. The basic principle of this process is that first various metallurgical dusts (BF dust, EAF dust and so on) are pelletized with a coal reductant, and they are then subjected to a fast reduction using RHF after being dried. Highly metallic pellets are produced and at the same time, nonferrous elements such as Zn, Pb, K and Na are evaporated into the RHF flu gas as secondary dust. Zinc is listed by the Enviromnental Protection Agency as one of the 129 priority pollutants. Therefore, recovering zinc from the industrial wastes is important in terms of enviromnental protection [2-3]. On the other hand, nowadays China is in shortage of zinc resource and the annual output from metal recycle only accounts for some 13% of the total zinc resource. There are many ways proposed to recover zinc from various wastes [ 4-7]. The aim of this paper is to recover zinc oxide from RHF secondary dust by a method with water leach followed by caustic precipitation. This work investigated the influence of the leaching temperature and leaching liquid/solid ratio on the zinc recovery efficiency. The process consisted of three stages: (1) leaching with water; (2) liquor/residue separation; and (3) zinc precipitation in caustic milieu."

Jan 1, 2014

By Luis W. Pommier

The wastes of the plating industry are generated in the process of rinsing the plated objects and during the cleaning of the plating shops. High volumes of hazardous waters are neutralized on site producing recyclable water, generating a metal rich, hazardous, filter cake. Occasionally, a complete plating bath has to be discarded which increases the metal content of the filter cakes. These filter cakes are discarded as hazardous at a cost of over $ 250 per ton. The metals found in the cakes are generally copper, nickel and chromium or zinc, lead and cadmium, assaying from 2% to 15% or even higher content of each metal The metals and their contents are highly variable. Some plating shops discard their products directly to hazardous waste sites, others, have them collected by companies which consolidate wastes from several producers prior to discarding. These wastes, richer in metal content than mine ores, need neither mining nor crushing and grinding for concentration. The commonly found impurities in the mine ores, i.e.: pyrites, arsenic, and valuable metals which are present in minute quantities, are absent in the filter cakes. The processes available to selectively recover the metals from the filter cakes, are discussed based on their technical and economic merits. The flow-sheets include leaching, solvent extraction when required, and electrolytic refining. Examples, showing the separation of copper, nickel and chromium and also of zinc and lead in pilot plants, show the technical and economic viability of the processes.

Jan 1, 1996

By Robert E. Moore

Renewed interest in olivine refractories has led to efforts to characterize them employing modern techniques of experimentation and data analysis. Initial studies have focused on determination of physical and thermophysical properties. Special equipment for the determination of thermal shock resistance and creep behavior have been constructed. Optimal compositions for maximizing various properties are being identified using appropriate statistical techniques. The overall goal is to develop response surfaces for each of a selected group of engineering design and use properties. Development of ?olivine Refractories? in the United States The term "olivine refractories" is used here because it does appear that domestic deposits of this rock will be the focus of renewed interest and "olivinell is the preferred term in this country. There are extensive deposits of high quality olivines extending through parts of Georgia. North Carolina and in the state of Washington. The eastern olivines are much more localized and extensively altered compared to the western materials. The Washington olivines exist as massive rock deposits in the Twin Sisters mountain area northeast of Seattle and their inaccessi-bility has slowed efforts to develop them. The North Carolina olivines have been used in steel plant applications since the 1930's. Geologists use the term "olivine" to describe assemblages of ortho-silicates. 2RO.SiO2, wherein the RO may be MgO. FeO. MnO. etc. When the RO consists essentlally of MgO and FeO. the material is called dunite and. as such, is synonymous with "refractory olivine." Refractory olivines utilizing North Carolina materials were developed for brick products by Birch and Harvey in this country around the mid-1930's. (I) Their work was completely independent of that of V. M. Goldschmidt and co-workers who used massive dunites located in Denmark. (2) These deposits are currently being mined by A/S Olivine of Denmark for the manufacture of a rather complete line of brick shapes for use in steel-plant. glassplant. and cement kiln applications. Birch and Goldschmidt

Jan 1, 1982

By A. Buzaianu, P. Motoiu, G. Popescu, C. A. Popescu, I. Rusu, A. F. Olteanu

"In recent years, the recycling magnesium metallurgy has developed new types of alloys, some of which exhibiting special electrochemical characteristics. Their application has found a fertile field in the energy conversion technologies. The paper introduces some technologic data on the recycling of aeronautical parts and scrap materials generated from the disassembling of magnesium alloy components, attempting to also solve the recycling of magnesium painted parts. The approach is meant to establish a superior quality method for recycling discarded parts or the excess of re-melting material in order to reduce environmental impact and costs. Magnesium-base alloys used as anodic materials are characterized by a high uniformity of the structural properties as well as by superior electrochemical performances, as compared to the ""classically"" used materials: Zn, Pb, etc. In nonconventional applications of magnesium alloys used as sacrificial anodes working in seawater, special alloying elements contribute to improving anodic processes. The influence of these alloying elements on magnesium sacrificial anodes was studied. It was found that the use of recycled materials in anode manufacture could reduce the Mg alloy cost by as much as up to 75% of the cost for virgin material, including the costs for the entire sequence of collection and transportation from a molding factory to a refinery, re-melting and composition adjustment.1. IntroductionMagnesium alloys are valuable materials because they exhibit low density, good forming and machining qualities, particular electrochemical properties and have a high recycling potential. There exists a false idea about the high costs of the use of magnesium alloys, partly justified by the lack of secondary materials suppliers and the insufficient knowhow in the diverse user industries to provide for an efficient substitution of conventional magnesium alloys for multipurpose applications. These circumstances have lately spurred the magnesium industry to develop new alloys and coatings and to improve processing techniques [1]. As a result, magnesium supply has greatly expanded and so have the research and development efforts to achieve complete recycling of Mg alloys.In consumer markets, magnesium is frequently selected because it helps reduce enery consumption. For example, an equal volume part made of magnesium is 23% the weight of a steel part and 64% the weight of an aluminium part."

Jan 1, 2008

By Brian R. Green

Resin-in-pulp (RIP) technology has been developed for recovery of gold. It is now time to look forward to the potential for application of the technology to other situations. Some cases have been identified and have merited preliminary testwork. Four examples, which illustrate the potential of RIP, are dealt with in this paper. These include removal of metal-cyanides from pulps, recovery of manganese that is difficult to wash from filter cakes, recovery of nickel from low grade pulps, and recovery of zinc from process residues. The discussion includes descriptions of the problems, factors that affect the choice of resin, and factors that will affect the economics of the process.

Jan 1, 1998

By Ross McClelland

This paper provides a technical overview on the installation and commissioning of the Ausmelt lead smelting, slag reduction and slag cleaning operations at the HZL Chanderiya site in India. It also discusses theoretical concepts behind the process practices currently in place at HZL.

Jan 1, 2006

By C. T. Yavuz

Higher environmental standards have made the removal of arsenic from water an important problem for environmental engineering. Iron oxide is a particularly interesting sorbent to consider for this application. Its magnetic properties allow relatively routine dispersal and recovery of the adsorbent into and from groundwater or industrial processing facilities; in addition, iron oxide has strong and specific interactions with both As(III) and As(V). Finally, this material can be produced with nanoscale dimensions which enhance both its capacity and removal. The objective of this study was to evaluate the potential arsenic adsorption by nanoscale iron oxides, specifically magnetite (Fe3O4) nanoparticles. We focused on the effect of magnetite particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the adsorption and desorption of arsenic. As particle size is decreased from 300 nm to 12 nm the adsorption capacities for both As(III) and As(V) increase nearly 1000 times. Interestingly, this increase is more than expected from simple considerations of surface area and suggest that nanoscale iron oxide materials sorb arsenic through different means than bulk systems. The desorption process however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for magnetite nanoparticles. This work suggests that magnetite nanocrystals and magnetic separations offer a promising method for arsenic removal.

Jan 1, 2006

By Evan Jamieson

The conditions under which various iron(III) oxy-hydroxides phases precipitate from iron(III) chloride and sulfate solutions at ambient temperatures (<60°C) are reviewed. Many of these precipitates are slow settling and gelatinous but ultimately transform into other more stable or crystalline phases. The phase that forms depends upon the rate of precipitation and pH. A comparison has been made of the iron(III) oxides formed upon the neutralisation of various iron(III) solutions with caustic, slaked lime or slaked magnesia which provide different rates of neutralisation and slowly dissolving solids with localised high pH. Mössbauer spectra of ferrihydrites precipitated under these different conditions are compared and interpreted. Particular attention is paid to the settling rate and settled volume which is likely to relate to industrial thickener and filter performance. It is shown that in pure chloride solutions, poorly settling ferrihydrite is usually produced at 20oC regardless of the choice of base. However in sulfate solutions fast settling precipitates are produced using lime and magnesia but not with caustic. In mixed chloride/sulfate solutions, optimum settling rates occur when the molar ratio of [SO4]2to Fe3+ is about 1:1 and when the sulfate concentration is <0.20 M. It is proposed that ?dense amorphous basic iron sulfate? or well-ordered ferrihydrite is formed on slowly dissolving lime or magnesia surfaces. Implications for industrial liquors are considered.

Jan 1, 2003

By Neil E. Izatt, Ronald L. Bruening, Steven R. Izatt

"IBC has developed environmentally friendly Molecular Recognition Technology (MRT) processes to selectively extract, recover, and purify a wide range of metals from a variety of process streams. The incorporation of MRT into process flow sheets can improve the economics of the processes. MRT separations are effective even at low (mg/L to \i%JV) metal levels. MRT processes are sustainable, being economically viable, energy efficient, and environmentally friendly as well as having a low carbon footprint. Examples of MRT processes will be presented and discussed involving platinum group metals, gold, rhenium, and other metals of interest to the mining community.IntroductionA significant portion of the earth's precious metal resources has been moved during the past century from underground to above ground [1]. This movement has important economic, health, environmental, ecological, and sustainability implications for the earth and its population. There is concern that recycling of certain precious and specialty metals from end-of-life (EOL) electronic wastes (e-wastes), catalyst wastes, mining waste streams, and other waste products such as rechargeable batteries is not adequate to maintain supplies of these metals sufficient for future needs [2-4]. Improved metal recycling rates and more efficient metal recovery from the enumerated wastes would significantly reduce the amount of virgin metals that must be mined to support our lifestyle [5]. More efficient separation procedures in ore processing flow sheets and more effective recovery of metals from low-grade waste streams would reduce metal loss in the mining industry."

Jan 1, 2012

By Andre L. De Vegt

For the past eight years Paques has been engaged in the development and installation of treatment systems based on biotechnological processes to remove sulfur compounds from water, air and gaseous streams. Metal and sulfate can be removed from mine waters using two biological steps: 1. Sulfate reducing bacteria convert sulfate to hydrogen sulfide (HzS). The HzS reacts with the dissolved metals to form insoluble metal sulfide precipitates. 2. Sulfide oxidizing bacteria convert excess H2S to elemental sulfur. Paques has designed and installed a groundwater treatment system for the Budelco zinc refinery in the Netherlands to remove metals and sulfate as described above. The system has been operating since May 1992 treating a flow of 5000 m3/d. A test program, utilizing a large scale pilot plant, will commence in November 1995 at a copper mine in the U.S.A. to remediate groundwater contaminated with sulfate and heavy metals. Biological reactor performance and selective metal recovery will be studied. Sulfur dioxide (S00 can be removed from fluegas using a combination of scrubber technology and the two biological steps. The end product is elemental sulfur. A commercial size biological desulfurization plant has been in operation since July 1994 treating 50,000 Nm3/h of fluegas. Sulfide can be removed from mining waters or anaerobic wetlands using a THIOPAQ® Sulfide Oxidizing reactor.

Jan 1, 1996

By B. Rourke, O&apos

Copper Refineries Ltd. (CRL), Townsville is Australia&apos;s largest producer and exporter of refined copper cathode. This status has been maintained by the implementation of a significant capital works program that increased the production capacity to 270,000 t/y by June 1999. In 1979, CRL was the first in the world to commission the ISA Process Technology which has now been marketed to 47 licensees worldwide. The new tankhouse design has focused particular attention on customer requirements, operational improvements, materials handling and equipment modernisation. Equipment which has been upgraded includes cranes, anode preparation, cathode stripping and scrap washing machines along with the total replacement of the electrolyte and electrical reticulation systems. Side stream electrolyte filtration has been introduced. Improvements to electrode alignment afforded by the conversion to polymer concrete cells, precise electrode location, and the upgrade of the electrode handling machines will ensure that CRL. continues to be one of the world&apos;s major quality copper cathode producers.

Jan 1, 1999

By Jerry L. Smith

Industry on a whole has not been very receptive to government prodding to implement waste minimization programs. Waste minimization has the appearance of substantial benefits, however, there are underlying difficulties and suspicions that need to be addressed before industry will support pollution prevention initiatives. They can be summarized as follows: - Human behavior resists change, uncertainty, and unknowns. - New waste minimization techniques are difficult to find and research. - Calculating the true cost of present waste practices as well as new techniques being considered is difficult and time consuming. - Getting a consensus opinion of all the individuals affected on the course or technique to be employed in a pollution prevention program. New software products have addressed many of the problems associated with implementing pollution prevention programs: They contain research on a large number of pollution prevention techniques and case studies; they generally are accessed by EPA ID number, chemical name, or synonym; and some programs have the option to print a comprehensive written user-specific pollution prevention program.

Jan 1, 1994