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By J. D. Miller

Low-level radioactive contaminated soils (10-500 pci/gm) created by defense-related activities at certain superfund sites, such as Nevada Test Site (NTS), is a current environmental concern. Many of these contaminated sites may require appropriate cleanup and restoration, which could cost billions of dollars and put tremendous pressure on our limited financial resources. Therefore, the development of a selective flotation process to separate such radionuclides from contaminated soils should be considered. In this study, both a pure depleted UO2 sample and three synthetic UO2/soil mixtures were used to evaluate surface chemistry features and to examine the possibility for the flotation of fine UO2 particles from selected soils. It was intended that this model system would be a reasonable representation of contaminated soils such as those found at the Nevada Test Site which are reported to be contaminated by PuO2 fallout. The effect of reagent schedule, particle size distribution, and surface charge are discussed with respect to the flotation separation of the UO2/soil mixtures. It was found that both commercial fatty acids and reagent grade sodium oleate are effective collectors for UO2 flotation provided the pH is adjusted to the range of pH 8-9. The bench-scale flotation results successfully demonstrated that froth flotation technology can be used to remove UO2 from such model contaminated soils with appropriate flotation chemistry conditions which depend on the soil characteristics and other pretreatment procedures. In the best case, 90.2% of the UO2 was removed from a UO2/NTS soil mixture (119 ppm UO2) and the soil reduced in UO2 contamination from 119 ppm to 17 ppm in a single stage bench flotation. The impact of clay slimes present in the soil is revealed by the results which show that, for example, for a deslimed soil (28x400 mesh and 100 mg UO2/kg soil) 85¬90% UO2 recovery can be obtained with a reduction in contamination to 4.6 mg U02/kg soil.

Jan 1, 1995

By Ehsan Vahidi, Fereshteh Rashchi, Ataollah Babakhani, Alireza Zakeri

"The synergistic effect of Cyanex 302 on solvent extraction of nickel and cadmium from sulfate solution with D2EHPA diluted in kerosene was investigated with the aim of increasing separation efficiency. Experiments were carried out within a pH range of 0.1-5.0 using sole D2EHPA and D2EHPA-Cyanex 302 mixtures in different ratios. Increasing Cyanex 302 to D2EHPA ratios in the organic phase caused a left shifting of the extraction isotherm of cadmium and a right shifting of the extraction isotherm of nickel. As a result, optimum separation was found with a Cyanex 302 to D2EHPA ratio of 0.1M:0.5M. In the present system, effect of a modifying reagent such as TBP was studied. The influence of various diluents including kerosene and carbon tetrachloride was also investigated.IntroductionBatteries are popular sources of portable energy. Ni-Cd batteries are manufactured in two main groups of small domestic cells and large industrial batteries with 80% being in domestic use. Ni-Cd cells have various uses, for example in cordless electric utensils, cordless telephones, airplane engine starters, and communicational distribution systems [1].Depleted Ni-Cd batteries are classified as hazardous waste since nickel and cadmium are heavy metals and suspected carcinogens. Given the risk associated with uncontrolled disposal, directions for issuing legislation on disposal and recycling of used batteries have been made in industrialized countries [2]. Recycling of Ni-Cd batteries is important from both economic and environmental points of view. Different methods have been used for recycling these wastes through pyrometallurgy [3], biotechnology [4,5], and hydrometallurgy [1,2].Due to the advantages of hydrometallurgical processes, several studies have been implemented on leaching and solvent extraction (SX) of the used Ni-Cd batteries. Leaching of batteries is usually done in sulfate or chloride media; while solvent extraction has been used in different extractants: two-stage solvent extraction by D2EHPA and Cyanex 272 [6]. Solvent extraction of Cd from leach solutions has been studied using various extractants; Cyanex 301 [1], D2EHPA [7], Cyanex 302 [8], Cyanex 923 [9], Cyanex 272, Tops 99, PC88A [10]. Application of phosphorus based extractants for the solvent extraction studies of Ni such as TOPS 99 [11], D2EHPA [12], Cyanex 272 [2], has been investigated. Separation of Cd(ll), Ni(II), and Co(ll) from chloride leach liquor of spent batteries [13], were explored in the earlier studies. Cd extraction with D2EHPA involves co-extraction of both Ni and Co [14], which causes issues in the separation process efficiency."

Jan 1, 2012

By Yuanbo Zhang, Ruijun Wang, Qian Li, Zhao Jing, Guanghui Li, Zhengwei Yu, Chen Liu

The high content of sodium and potassium in sinter is harmful for blast furnace ironmaking. Reductive sintering technology can remove more alkali metals than conventional sintering process. In order to improve the removal ratios of Na and K, reductive sintering with both CO-containing flue gas circulation and carbon-bearing pellet was conducted in this study. Experimental results show that all indexes except the VSV and P were improved in reductive sintering with CO circulation. Flue gas circulation technique combined with carbon-bearing pellets were beneficial to reductive sintering, because it could maintain good sintering indexes and enhance the removal of Na, K. The best removal ratios of Na, K and reduction degree of iron oxides were 20.37%, 63.73% and 23.76%. In reductive finished sinter, silicate mineral becomes the important binder phase, and main iron mineral phases are wustite (FexO) and magnetite (Fe3O4).

Jan 1, 2016

By John M. Gaines

Lead concentrates from the Viburnum Trend in the Southeast Missouri Lead district are sintered prior to smelting to bind the particles together homogenize the feed, and reduce the sulfur content. Good sinter forms competent masses about 4 to 6 inches across, that hal!e about 15% porosity and good mechanical strength to withstand transport and the weight of the overlying load in the smelter. Bad sinter has poor mechanical strength and forms fine fragments that retard the circulation of reducing gases in the furnace and lengthen the time required for reduction. The productivity of the lead smelter depends on good sinter feed. Because some lead sinter plants produce bad sinter about 20% of the time, this applied mineralogy study has been undertaken to determine the mineralogical and microtextural differences between good and bad sinter. A reflected light microscopic study of 130 polished sections has shown that good and bad sinters differ distinctly in their mineralogy, tex1ure. and character of, porosity. Good sinter consists of hardystonite, franklinite. lead-zinc-bearing magnesium-calcium silicate, lead silicate matrix, and large crystals of calcium-magnesium-iron silicate, together with minor amounts of lead oxides, lead-zinc silicate, metallic lead, specular hematite, magnetite, lead-iron-bearing zincite and zinc-Iead-magnesium-bearing wustite in a tightly intergrown mesh of crystals and with an evenly distributed porosity of 15% to 20%. Electron microprobe analyses show that the principal phases contain lead (or zinc): hardystonite (4-20% Pb) franklinite (2-14% Pb) and lead silicate matrix (65-74% Pb). Bad sinter differs from good sinter in the greater abundance of lead silicate matrix, galena metallic lead, and lead oxides and the lesser abundance of hardystonite, franklinite and calcium-magnesium-iron silicate. Bad Sinter is characterized by a lack of an intimate intergrowth of the constituent phases. Its porosity is much lower commonly 0 to 5% and those pores are concentrated in local areas rather than distributed evenly throughout the sinter.

Jan 1, 1991

By Nolberto Moreno Borjas

This paper outlines the detrimental impact that unblended ore can have on the Ni and Co recoveries and the ore slurry density with real data from the Caron low-pressure ammonia leaching process for the Punta Gorda ore. The author briefly discusses the reason for the decrease in slurry density that the process experiences. The lower metal recoveries in the process that are caused by the unblended ore chemical characteristics and variations are shown with a data base statistical analysis drawn from the results obtained from a pilot test, designed with different ore bypassed from the normal process flow and a similar ore from a similar metallurgical treatment. Keywords: Ni-Co Laterite, Caron Process, Ore Blending, Slurry Density, Metal Recovery

Jan 1, 2004

By Jorge Alberto Soares Tenório, Amilton Barbosa Botelho Jr, Denise Crocce Romano Espinosa, Mónica M. Jiménez Correa

Wastewater from nickel lateritic process still has valuable metals that could be recovered. Using an ion exchange to recovery these metals, the iron becomes a problem due to the fact that it precipitate at pH 2. The aim of this research was to make iron soluble by reducing Fe+3 to Fe+2. A synthetic solution was prepared with sulfate ferric. The reducing agent sodium dithionite was used and the potential was varied (initial potential: 700, 600, 500, 450 e 400 mV) using as a reference the Pourbaix diagram for iron created by HydroMedusa software. The pH was ranged between 0.5 and 2.5, the reducing agent’s concentration was 0.5 M and the reaction time ranged between 30 and 120 min at room temperature. The ferric iron and total iron concentration were verified using a spectrophotometer with 5-sulfosalicylic acid (SSA) to determine Fe(III) and ammonia to determine Fe(II) and Fe(III) in 500 and 425 nm, respectively. The results indicated that total reduction was at 400 mV in any pH between 0.5 and 2, but less than 40% in pH 2.5 at this potential value.

Mar 1, 2017

By Ronald L. Pariani

To date, significant advances have been made regarding the development and commercial implementation of full deposit stripping in the copper industry such as practiced at Copper Refineries, LTD in Townsville, Australia. The paper describes the history and current practice of Electrowinning (EW) plants which may be coupled with solvent extraction. The modular nature and degree of automation are described in relation to the various sizes of operations. Reference is made to the expansion capability of commercial equipment plus associated economics of the mechanical processes for producing full cathode deposits. It is recognized that the technology described may be adaptable to other nonferrous refining areas where feasible. The paper highlights the state of the art in mechanized stripping equipment as applied to current and planned SX-EW plants.

Jan 1, 1987

By K. Morsi, P. Mehra

"Spark plasma sintering has gained a considerable amount of attention over the past decade, due to its rapid sintering rates, and low temperature requirements, but has so far been usually limited to the production of simple geometries. The present paper examines the current-activated production of extended geometries through the process of spark plasma ""extrusion"". Of interest in the present study is exploratory research into the effect of electrical current activation on the reactive consolidation of powder systems to form intermetallic materials.IntroductionSpark Plasma Sintering (SPS) has been the subject of intense research over the past decade [ 1,2, 3,4,5,6]. The process boasts unique advantages which include ultra fast heating rates, shorter sintering times and lower sintering temperatures than needed in conventional sintering. The process is however limited to the generation of predominantly simple geometries. Recently one of the authors investigated the spark plasma extrusion of aluminum, where an aluminum powder compact is directly (Joule) heated through an applied DC electric current. Here extended geometries can be generated under the influence of electric current. A number of heating sources were identified including the heat source from current, i.e. Joule heating, frictional heating and heat from the deformation energy. However in the case of reactive powder systems, an extra ""one-time"" transient heating source can be supplied. By considering combustion synthesis of powders, this heating source is derived from the reaction between elemental powders to exothermically form a product at some ignition temperature [7]. This exothermic energy heats the compact to the maximum ""combustion temperature'', which could be hundreds of degrees higher than the ignition temperature. Hence a high temperature processing window (of short duration due to heat losses to the surroundings) becomes available in which the material is most suitable for stress-induced deformation and consolidation. For reactive spark plasma extrusion, two scenarios can be envisioned. The first is where the reactive powder compact is ignited through the application of current, and extruded within the high temperature processing window (also under the influence of current). The second scenario is to allow the heat of deformation/friction to heat the material during extrusion, to simultaneously force a reaction and consolidation. Here it is expected that the processing window will be very small if feasible."

Jan 1, 2011

By R. R. Odle

A laboratory and pilot-scale investigation of direct smelting of copper concentrates was conducted to determine the effect of concentrate analysis and the degree of roasting on the yield and quality of copper produced in a subsequent smelting step. A stoichiometric :mOdel of direct smelting is presented which predicts the? quantity of copper; slag, and white metal' prOduced'and the distribution of copper in these phases as a function? of the concentrate '(calcine) analysis.

Jan 1, 1983

By R. T. Hernández, I. Hilerio, A. Altamirano, M. A. Barrón

"The principal objective for finishing surfaces is to protect and/or to decorate them. This can be achieved by adding or removing material from the work surface. The addition of aggregated material is called coating or recovering. In this work, mecano-chemical techniques are investigated for surface finishing. For these techniques, barreling or polishing by the friction method will be used. These are the cleaning or finishing processes most used for great volumes of small pieces. These methods improve the surface finishing by eliminating burrs, sharp pointed, tool marks and crusts of casting. They are used to clean metallic pieces, ceramics and polymeric materials. The process is based on rubbing or friction by abrasives. The pieces are arranged in the barrel with an abrasive and an additive (water or chemical additive). The machine produces a rotating movement on the pieces. When the abrasive passes against the surfaces of the pieces, it produces an action of rubbing and impact that cleans the surfaces. The rubbing action is developed when the upper layer of the charge slides to the lower extreme when the barrel rotates. The barrel can be hexagonal or octagonal to facilitate the sliding of the charge. The barrels can be between 15 to 120 cm in length and they can have almost any diameter and velocity of rotation. There are several types of barrel: individual, multiples, and multiple compartments. The barrels are rotated using a wheel spindle or rolling pins, that the can ride horizontally or be tilted to produce an additional movement of the charge.IntroductionShot penning is a cold method in which compressive effects are induced on an exposed surface of a metallic piece, by the impact of a rain of shots directly on the surface of the metal, at great speed under controlled conditions. This differs from cleaning with the help of air, because even when shot penning cleans the surface of the metal, this function is incidental. The main purpose of shot penning is to increase the resistance of the piece to fatigue. The process has other applications: raises the tensile strength and decrease corrosion fracture."

Jan 1, 2012

By Roger Agnew

Sulphide ores mined by Inco Limited in the Sudbury District contain small quantities of cobalt. During beneficiation, cobalt distribution to various streams is similar to nickel. After smelting, nickel is selectively extracted by carbonyl refining and the cobalt remains in the carbonylation residue. This residue is processed in a specialized hydrometallurgical plant to produce precious metal residues, copper cathodes, and a nickel- cobalt carbonate intermediate product. The nickel-cobalt is shipped to Port Colborne where the cobalt is separated as cobaltic hydroxide and refined to metallic cobalt. This paper deals specifically with the recently constructed Electro Cobalt Refinery. The cobaltic hydroxide is dissolved and residual zinc, copper and nickel are removed by ion exchange and organics by a carbon column. The purified cobalt solution is fed to the electrowinning circuit where cobalt rounds are produced on stainless steel mandrels. In the design and construction of the refinery, special attention was directed to materials of construction both for the process equipment and the physical plant, operating control and flexibility, and the quality of the working environment. The end result is an efficient and clean operation which yields a product of excellent quality.

Jan 1, 1988

By Guozhu Ye

Hydrometallurgical zinc recovery from EAF dust has several advantages compared to pyrometallurgical alternatives in terms of low temperature operation, lower energy consumption and higher flexibility. Many hydrometallurgical processes have been suggested and tested over the years without success. The main reasons are: -Low leaching yield of zinc due to the fact that a high fraction of ZnO in the EAF dust exists in the zinc ferrite structure which makes selective leaching of ZnO not possible -Many of the proposals could not handle the halide in the EAF dust To eliminate these two disadvantages, two zinc ferrite elimination concepts have been tested and developed in the REZIN project of the EU 5th Framework Programme. The two concepts for zinc ferrite elimination could be shortly described by the following chemical reactions: A. ZnOFe2O3 + 2CaO = Ca2Fe2O5 + ZnOfree B. ZnOFe2O3 + C = Femet + CO/CO2 + ZnOfree These two concepts were investigated in details in combination with a subsequent leaching step using the novel EZINC process for recovery of zinc from EAF dust. Leaching of pretreated samples has shown great increases of a zinc recovery yield. A zinc recovery of over 90 % could be reached, as compared to about 50 % for no-pretreated samples. This paper will describe the two concepts in details.

Jan 1, 2006

By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990

By D. A. Robbins

The Resource Conservation and Recovery Act. of 1976 (RCRA) requires testing of waste materials as part of the determination of whether these materials are classified and managed as hazardous wastes. The adoption of one standard testing procedure and its application to all types of waste materials has stirred much controversy. In the center of this controversy is the appropriateness of this testing procedure in characterizing non-ferrous metal intermediates and slags. The authors have evaluated the relative availability of metals in several types of copper and lead slags as defined by various testing protocols. Also discussed is the relationship between the chemical character of the slag and the availability of metals to leaching and certain metallurgical practices that can influence metals availability.

Jan 1, 1983

By I. A. Ibrahim

Ilmenite, in its natural form, is an inactive mineral from which the selective removal of iron is rather difficult. The reactivity of ilmenite. so that it can be leached with dilute hydrochloric acid, can be enhanced by chemical reduction in solution using a suitable metal as a reducing agent. The present paper aims at the evaluation of an Egyptian ilmenite ore for the production of synthetic rutile by direct leaching with hydrochloric acid in presence of iron powder. In this process, the titanium and iron contents are dissolved; meanwhile, the dissolved titanium is hydrolyzed and re-precipitated leaving mainly iron in solution. Leaching conditions were optimized to obtain less iron in the final solid product. Addition of sufficient amount of iron powder during leaching reduces the dissolved Fe3+ to Fe2+ and reduces the dissolved Ti4+ to Ti3+. The creation of Ti3+ in solution is assumed to have a role in dissolving the ferric iron and hence increasing the reactivity of the ilmenite ore. Synthetic rutile of about 90% TiO2 and 0.77% Fe2O3 was obtained from ore with a grain size 100% passing 200 mesh and a 5-hour leach time with 20% HCl at boiling temperature (110°C) and 0.11 g iron powder / g ore.

Jan 1, 2003

By W. Petruk

A study was performed to determine whether mineral textures affect are breakage during grinding, and to establish a correlation between are breakage and mineral liberation. A base metal are from the Brunswick No. 12 deposit in New Brunswick, Canada was ground for different periods of time in a laboratory ball mill, and both the unbroken are and the ground products were studied by image analysis. Similar size distributions were obtained for material from the 15-minute grind in a laboratory ball mill (K. 0 67 pm), for the grinding circuit discharge from a commercial mill (K. 0 = 59-72 pm), and for pyrite grains in unbroken are (K,. = 74 pm). This similarity indicates that the 1S-minute grind separated weakly adhering pyrite grains along grain boundaries, and represents the limit of easy breakage for the are. At this grind (15 minutes) large discrete are mineral grains and weakly adhering interstitial fillings aIrong pyrite were liberated. On the other hand, the 15-minute grind neither separated rooderately bonded pyrite grains nor released rooderate1y bonded interstitial minerals from pyritei a 45-minute grind (K.. 31 pm) in a laboratory ball mill was required. For Brunswick No. 12 are, a 45-minute grind in a laboratory ball mill (Keo = 31 pm) is equivalent to regrinding in a commercial mill (K ?? Fl:$ 30 pm). Grinding beyond 45 minutes in the laboratory ball mill broke the are by fracturing pyrite across grain boundaries and by Chipping grain edges. Such intense grinding (longer than 45 minutes) did not markedly increase sphalerite liberation. In contrast, the intense grinding increased galena liberation because a significant proportion of the galena occurs as minute inclusions in pyrite. These findings show that ore breakage and coincident liberation depend upon size distributions, intergrowths, and mode of occurrence of the minerals in an ore.

Jan 1, 1988

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

By Michael J. Nicol

Growing environmental and occupational safety concerns about the use of cyanide in gold processing has increased the interest in more acceptable alternatives. The most likely of these is thiosulfate. However, the thiosulfate process lacks a proven in-pulp method of recovering the dissolved gold, because activated carbon is not effective for the absorption of the gold thiosulfate complex .. Anion exchange resins do offer a possible route for in-pulp recovery. This paper describes work aimed at the evaluation of the effectiveness of commercially available anion exchange resins for the recovery of gold from thiosulfate leach liquors? and pulps. It has been found that strong-base resins are superior to weak-base resins in that they have a larger capacity, which assists in reducing the competition from other anions within a leach solution. Further studies with a selected commercial strong-base resin have shown that competing polythionateanions (particularly tri-and tetrathionate). Lower the maximum possible gold loading but that gold is selectively recovered over other base metal anions in solution. Kinetic experiments found that while? competilig anibns did not affect the initial rate? of gold loading it was important to minimise the contact time of the resin in solution so to prevent displacement of loaded gold by competing anions over longer times. A small-scale resin-in-pulp plant investigation showed gold can be recovered from a leach pulp by a strong-base resin to yield gold loadings of 3000 mg/L, barren pulp containing less than 0.05 mg/L of dissolved gold and. copper loadings of 500 mg/L. Loaded copper was displaced gold and at a loading of 2000 mg/L gold the copper loading was minimal «500 mg/L). The resin was found to recover gold adsorbed on the solids that would, otherwise have. reported to tails if a solid/liquid separation method were used. A patented two-step elution process in which copper and then gold are separately eluted from the resin is also discussed.

Jan 1, 1998

By T. T. Chen

A mineralogical study of copper anodes and copper anode slimes was carried out to elucidate the silver phases present and the behaviour of silver during copper electrorefining. Most of the silver in the anodes is in metastable solid solution in the copper metal. As the copper dissolves, silver also dissolves, but is rapidly removed from solution by a variety of reactions. Some of the silver is precipitated as Ag by cuprous ions and some is precipitated as a complex CU-Ag-Pb-As-Se oxidate phase. Much of the silver, however, reacts with copper selenides to form, progressively, (CU,Ag) 2se, AgCuSe and Ag2se. The reaction commences at the periphery of the selenide grains and progresses inward; the result is commonly a silver-rich species on the outside of a silver-deficient core. Slimes collected periodically throughout the electrorefining cycle show a progressive silver enrichment of the selenides. Traces of Ag2Te also may be present, but the telluride seems to J:ie a rare constituent of most raw anode slimes.

Jan 1, 1989

By Seong-Jong Kim

The formation behavior and corrosion characteristics of anodic oxide films on pure Mg and Mg-AI alloys were investigated focusing on the effects of anodizing potential, Al content, temperature and NaOH concentration. Pure Mg and Mg-AI alloys were anodized for 10 min at 3, 10, 40, and 80 V in NaOH solutions. Mg(OH)2 was generated by an active dissolution reaction at the surface of the specimen and the product was affected by temperature while MgO generation increased with NaOH concentration. Moreover, the current density after anodizing for 10 min at a constant potential decreased with increasing AI content in Mg-AI alloys,

Jan 1, 2003