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By J. W. Lyman

The U.S. Department of the Interior, Bureau of Mines, investigated methods to recover valuable rare-earth materials from NdFeB magnet scrap. Although several processing techniques were evaluated" the best separation of rare earths from the NdFeB magnet ,scrap was obtained by sulfuric acid dissolution followed by precipitation of recyclable rare-earth salts. Both sodium and ammonium intermediate double-salt precipitates' that can be converted to a variety of useful neodymium products were investigated. The sodium system showed a neodymium recovery of 98 pct, while the ammonium system yielded 70 pct during double-salt precipitation. The iron-rich effluent following the rare-earth recovery was treated to produce sodium and ammonium iron jarosites that can be disposed of or converted to hematite. By following this new procedure, many materials handling and economic disadvantages found with fluoride or oxalate direct precipitation were avoided.

Jan 1, 1992

By Stig Petersson

Slag from the converting of copper matte is usually recirculated to the smelting furnace. This recirculation generally causes disadvantages as magnetite-build-up in the furnace, accumalation of impurities as antimony, lead, nickel etc in the process. The treatment of converter slag in a separate furnace in order to recover the copper and nickel content would be of advantage from several points of view. At the Mining and Metals Division, Boliden, testwork has been carried out to treat converter slag from the PS-converters in a separate furnace. The tests have been performed in laboratory and pilot plant scale. The pilot plant tests have been carried out in a TBRC with charges of 5 tons. Based on these tests a full scale TBRC has been projected in order to treat the slag from the PS-converters. This slag will be reduced with copper concentrates to give a matte and a final slag low in copper and nickel. The background and data from the testwork are presented. Also the lay out, technical data and flowsheets for the projected process are shown as well as some production data from the Rönnskär smelter.

Jan 1, 1976

By R. E. Burleigh

'Gold-telluride mineralization was deposited in quartz veins which cut a Late Cretaceous tonalite pluton emplaced near the southern margin of the Peninsular tectono-stratigraphic terrane in south-central Alaska. The gold-bearing veins formed shortly after the development of a widespread Cu-Mo sheeted quartz vein system. Early mineral assemblages consist of quartz, white mica, pyrite, and arsenopyrite (wall rock only). Subsequently, pyrite. sphalerite, chalcopyrite, zoned tetrahedrite and gold precipitated within multiply fractured veins. Late stage galena, tellurides (altaite, nagyagite, coloradoite), and Pb-Sb or Pb-Cu-Bi sulfosalta with gold constitute bonanza ore assemblages that are variably associated with quartz, white mica, ankerite, and calcite. Fluid inclusion evidence coupled with mineral assemblage paragenesis suggests the depletion of volatiles (C02, H2S) and cooling resulted in the precipitation of high grade gold mineral assemblages.

Jan 1, 1988

By Norbert Patzeh

The demand for nickel is growing and will continue to do so for the foreseeable, future. This will make the construction of new leaching and smelting plants necessary. This paper described a number of possible alternative processes. The first projects with new technology are currently undergoing trials and feasibility studies. Experience from other industrial sectors and from existing plants is being incorporated into these investigations. The question is, to what extent the old nickel producing concepts will continue to be applied in the future. Keywords: Latcritc, rotary kiln, cyclonc rcactor, dust processing

Jan 1, 2004

By J. L. Jambor, H. W. Nesbitt

Oxidative dissolution of pyrrhotite and pyrite is largely responsible for the sulfate-rich waters of the vadose zone in the Waite Amulet tailings. Although the shallowest of the sulfate-rich waters are of the Fe-SO4 type, they change to Mg-SO4-type, near-neutral waters within 1-2 m of the tailings surface. Phyllosilicates and amphiboles are the only minerals present in sufficient quantity to ameliorate the amount of acidity produced. X-ray diffraction and microscopic studies of bulk sample indicate that quartz, chlorite, talc, amphiboles, magnetite, albite, and micas are the major and minor non-sulfide minerals, but their variations with depth do not give clear indications of depletion in the vadose zone. Mineralogical and bulk chemical compositions of the tailings confirm that Fe2O 3 has accumulated in large quantity in the vadose zone, with the Fe having been derived from Fe sulfides. When the effect of Fe2O3 is accounted for, the bulk compositions suggest that SiO2 is slightly more abundant in the vadose zone than in the saturated zone. This may be the result of residual enrichment of siliceous minerals such as quartz and albite in the vadose zone. Weathering of the tailings since the cessation of deposition in 1962 has resulted in a well-defined zone of sulfide depletion and secondary sulfate-mineral development. Although some silicate dissolution is indicated by pore-water compositions, the role of silicates in providing neutralization seems to have been minimal. The contribution by silicate minerals in laboratory tests of neutralization potential may be excessive relative to that in natural settings.

Jan 1, 1999

By O. Forsén

A new cell construction was designed for the study of the electrochemical behaviour of additives in conditions that simulate real copper, electrorefining. The behaviour of gelatine and thiourea was studied by applying different electrochemical methods, i.e. polarization resistance and voltametric measurements. In this study, individual galvanostatic electrolysis experiments were carried out for 120 hours. The organic additives were introduced to the electrolyte at certain intervals and their concentration was varied in the range &om zero to four ppm. An optical microscope was applied for the examination of copper cathode deposit microstructures. The results show that gelatine has a polarizing effect on the deposition potential of copper whereas even small amounts of thiourea depolarize the electrodeposition of copper. The maximum inhibitor efficiency of gelatine was obtained at a gelatine concentration of slightly lower than two ppm. When both gelatine and thiourea were present in the electrolyte, the depolarizing effect of thiourea exceeded completely the polarizing effect of gelatine. If chloride ions were added to gelatine and thiourea containing electrolyte, the electrochemical behaviour of the system was altered drastically. Chloride ions resulted in the prevailing of polarization effect caused by gelatine while the depolarizing effect of thiourea disappeared in this system. The polarizing effect of gelatine increased until chloride ion concentration of 30 ppm was reached. Also, the above electrochemical phenomena could be detected in the optical examination of copper deposit microstructure.

Jan 1, 1995

By Bowen Li, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"Magnetic iron sulfide ore particles heat rapidly by microwave (MW) irradiation generating plasma during oxidation of surfaces. The high temperatures produced by the exothermic event decompose local portions of samples forming a differentiated flux of partially melted silicate (si-mt) with entrained metal-sulfide (sul-mt) droplets. The si-mt forms crystals of olivine (01) in Ca-rich pyroxene (Cpx) melt that resorbs a portion of iron sulfide (Po). The immiscible sul-mt droplets of (Fe,Ni,Cu)1-xS contain magnetic subsolidus Ni-pyrrhotite (Ni-Po) with Cr-bearing ferrospinel (Mag). Sub-micron sized flecks of Au are found on the surface of a sul-mt droplet with scanning electron microscope (SEM).IntroductionSulfide ore deposits supply the world's mineral resource in the production of non-ferrous metals. Particularly, Cu-Ni deposits are chemically enriched in metals from high sulfur saturation during magmatic formation that creates the proper geochemical environment for metals enrichment [1, 2]. The sulfur and oxygen fugacity control redox conditions of a differentiated silicate/sulfur magmatic melt with the concentration of iron playing a dominate role in the chemical partitioning of metals in sulfide liquid [3, 4]. The initial magnetic crystallization of (Fe,Ni)i-xS monosulfide solution (mss) from metal-sulfide liquid has an exclusive effect on the fractionation of mineral assemblages (zoning) [5].Phase equilibria of sulfide melt (sul-mt) components are related by a miscibility gap with mss forming Ni-rich pyrrhotite (Ni-Po) followed by the crystallization of (Fe,Cu)1-xS intermediate sulfide solution (iss) [6]. Precious metals form stable chacogenides and are retained in solution until the final liquid solidifies. The redistribution of metals now occurs by subsolidus cooling of mss and iss that exsolve low-temperature Fe-Cu-Ni bearing mineral assemblages [7]. The proper interpretation of ore genesis increases processing capabilities by isolating chemically enriched zones during extraction and should be used to aid in sustainable mine site development [8-11]."

Jan 1, 2013

By Ian Baker, Xavier Pierron

"Iron aluminides hold great promise for intermediate temperature applications (to ~ 600°C) because of their excellent oxidation and sulphidation resistance and good strength. However, they have poor low temperature ductility, a feature which is exacerbated by water-containing environments. This paper presents an overview of the effects of environment on the ductility of iron aluminides, including the effects of iron aluminum ratio; ternary alloying additions, particularly boron; strain rate; and temperature. The mechanisms involved in water-induced embrittlement are discussed.IntroductionOver the last few years, it has became increasingly evident that the ductility and fracture toughness of many intermetallic compounds, particularly aluminides, are reduced dramatically if they are mechanically tested in either air or in hydrogen-containing atmospheres (1-5). For FeAI and Fe3AI, it has been shown that water vapor, for example in air at room temperature, can form atomic hydrogen by reacting with the Al atoms (1, 2). As a result in iron aluminides, the environmental embrittlement process is quite similar to traditional hydrogen embrittlement. This can be easily demonstrated by either testing an iron aluminide in an environment free of the deleterious species or by testing at high strain rates, both of which result in greater ductility. The purpose of this paper is to review recent progress in understanding environmental embrittlement in FeAI and Fe3AI, and to consider possible environmental embrittlement mechanisms. Greater understanding of this phenomenon will lead ultimately to remedies to this problem which is a major reason for preventing the practical application of these materials. First, some background on the iron-rich aluminides."

Jan 1, 1996

By A. Cullaj

Several industrial sites suffer from the contamination of soils from heavy metals, which are emitted among others by anthropogenic mining and metallurgical activities. Effective and economic physicochemical technologies for remediation of these sites remain complicated and costly. A new alternative remediation technique is the so-called phytoremediation. This is based on the ability of some plants to accumulate very high concentrations of metals from soils and thus providing the basis for a remediation of the contaminated sites. This technique as an emerging branch of natural biotechnology, has several advantages compared to the sophisticated physicochemical techniques of soil remediation. It is not only environmentally friendly but also its costs are quite low since it is solar driven. Furthermore plants can accumulate metals to such levels that the mineral recovery maybe feasible even in conventional Ni refinery or smelting operations. n this work, the potential of many plants to accumulate nickel has been investigated in order to identify the species which offer the best phytoremedial potential for nickel contaminated soils in Albania. Field surveys have been made in five nickel-containing sites in order to identify the nickel tolerant species that have spontaneously grown in contaminated soils. Atomic Absorption Spectrometry measurements were carried out on 145 different plants collected. 16 of them were identified as having an hyper ability to accumulate nickel since they contained more than 10 000 mg Ni per kg (OW). Seven taxa are of Alyssum genus and one of BornmueIIera genus of Cruciferae. The highest accumulation of nickel was present in aerial parts of Alyssum murale var. chlorocarpum Hausskn (25 500 mg/kg or 2.5%) and Alyssum markgrafii O.E. Schulz (23 700 mg/kg or 2.37%). The seeds germinated are more evidenced at A.m.var. chlorocarpum, about 63%. These plants are suggested as the most promising species to be used for phytoremediation purposes in nickel contaminated soils and phytoextraction of nickel.

Jan 1, 2003

By Suchun Zhang

The alkaline oxidation of refractory gold concentrates containing arsenopyrite and pyrite at ambient temperatures and pressures has been found to be accompanied by the simultaneous dissolution of gold without the addition of cyanide. A detailed study has been made of the kinetics of the oxidation of the pure minerals and of several concentrates. The reaction products of the oxidation of arsenic and sulphur have been monitored using chromatographic techniques. In the case of arsenopyrite, thiosulfate, monothioarsenate, arsenate and sulfite are the principal products while thiosulfate has been confirmed to be the dominant product of pyrite oxidation. Gold, either as added powder or as a constituent of the concentrates has been found to dissolve simultaneously during the alkaline oxidation of both arsenopyrite and pyrite, and this appears to be associated with the in-situ formation of thiosulfate as a lixiviant. The effects of temperature, stirring speed, oxygen partial pressure, alkalinity and pulp density on the oxidation of arsenopyrite and the dissolution of gold have also been investigated. Keywords: Gold, dissolution, arsenopyrite, pyrite, alkaline, oxidation, thiosulfate, thioarsenate

Jan 1, 2005

By Arsenio Enriquez, Adrian Deneys

"Rio Tinto through its subsidiary Kennecott Utah Copper Corporation (KUC) and Praxair have implemented the CoJet® gas injection system for copper anode refining. The system provides the capability to melt on average 60 to 70 tons of scrap copper per heat (with acceptable NOx emissions). The system has demonstrated the potential for tuyere-less sulfur and oxygen removal using coherent jet technology.This paper describes the process concept, system development, laboratory testing, implementation, current operation and ongoing developments."

Jan 1, 2009

By Achilles J. B. Dutra, Carlos M. Juarez

"The use of thiourea as a gold leaching reagent has been extensively studied by many researchers, and it has proved to be promising for some cases as refractory ores. Otherwise, the recovery of gold from these solutions did not receive so much attention. In this paper the electrowinning of gold in acidic thiourea solutions was studied by voltarnmetry and chronopotentiometry. An adsorption step was detected prior to Au(I) reduction and the diffusion coefficients at 25°C for Au-TU complex and FD were found to be 1.00 x 10.5 cm2 S-I and 1.98 x 10-5 cm2 S-I respectively. At -0.350 V (SCE) a passivation probably due to TU adsorption was observed. For higher overpotentials hydrogen evolution was the main reaction.IntroductionThe use of acidic thiourea solutions for the extraction of gold and silver has shown to be a promising alternative to the traditional process of cyanidation, specially for certain refractory ores (1-3) and electronic scrap (4). In some cases, the industrial scale was reached (1,5). The thiourea leaching of precious metals presents advantages over cyanidation, as faster kinetics, lower toxicity and lower sensibility to base metals; however the costs due to high thiourea consumption impairs its use.The majority of the publications on thiourea processing of gold is on leaching. Many are review papers (5-7). Recently, the adsorption and desorption of the gold-thiourea complex on activated carbon and ion exchange resins have been studied (8-11).Little research has been done on the electrowinning of gold from acidic thiourea solutions, most of it has been carried on the seventies and beginning of the eighties in the former USSR (12-17) and concerned the eletrolytic extraction of gold in tridimensional cathode cells.The present paper concerns the cathodic behavior of the gold-thiourea complex in the presence of formamidine disulfide in order to provide information on the electrowinning of gold from solutions obtained directly from leaching or from an elution process."

Jan 1, 1997

By Raymond E. Healy

Circuit samples from the HBMS concentrator were assayed for l5elements, and image analysis was done to determine the modal quantities, grain size distributions and liberations of the minerals. Material balancing was done on these data to determine distributions of the minerals in each concentrator stream. The ore was mined during the waning phase of mining and is diluted with backfilled copper smelter slag. The mill feed grades 1.0 wt% Cu and 1.8 wt% Zn. The slag silicate phases contain approximately 1.5 wt% Cu and 6.5 wt% Zn; therefore the Cu and Zn head grades due to chalcopyrite and sphalerite, are only 0.9 wt% Cu and 1.2 wt% Zn, respectively. The recovery of Cu in the Cu-concentrate (Cu-conc.) is only 77.5 %, whereas that of chalcopyrite is 89.2 %. Similarly, the recovery of Zn in the Zn-concentrate (Zn-conc.) is only 40.2 %, whereas that of sphalerite is 71.0 %. The slag accounts for approximately 60 % of the Cu, and 85 % of the Zn in the tailings. The main loss of chalcopyrite is as unliberated grains to the tailings, and the main loss of sphalerite is as free grains to the Cu-concentrate and as unliberated grains to the Cu-concentrate and tailings. Approximately 85 % of the chalcopyrite and sphalerite lost to the tailings. accounting for 8 % and 10 % of the respective minerals in the concentrator feed, occur as middling and sub-middling grains. Extremely fine regrinding would be required to liberate these minerals.

Jan 1, 1989

By M. J. Collins

A hydrometallurgical process has been tested at the Sherritt Research Centre for separation of zinc, lead, copper and precious metal values from the zinc oxide fume leach residue stockpiled at the HBM&S operations in Flin Flon, Manitoba. Zinc is found primarily as zinc femte and sphalerite in the residue, lead as lead sulphate and jarosite, and copper as sulphide and jarositic compounds. Gypsum and siliceous gangue are significant diluents. The separation process includes hot acid, atmospheric and reducing (sulphur dioxide) leaching; zinc, copper and lead flotation; and atmospheric iron removal steps. Zinc is recovered to a high strength zinc sulphate solution and to a zinc sulphide concentrate suitable for feed to a roaster or to a zinc pressure leach plant; lead to a high grade lead sulphate concentrate suitable for feed to a lead smelter, and copper to a high grade copper sulphide concentrate suitable for feed to a copper smelter. Precious metals are divided between the zinc, lead and copper concentrates.

Jan 1, 1993

By S. Ajima

The Naoshima Smelter and Refinery is the most important copper operation of Mitsubishi Materials Corporation. There are a Mitsubishi Continuous smelter and a conventional type of copper tankhouse. The continuous smelter with 240,000 mtpy of anode production was commissioned in May 19914 replacing two existing smelters, i.e an original Mitsubishi Process line and a conventional reverberatory furnace line. In July 1992, the copper tankhouae was expanded for the purpose to close the gap of production capacity between the smelter and the tankhouse. The cathode production capacity was increased from 13,800 to 15,800 mtpm. By these plant modifications, the distribution of minor elements was significantly changed and the impurities load is getting on increase reflecting recent shortage of clean copper concentrates supply. The paper discusses the distribution of minor elements and the impurity control strategy at the smelter end the refinery.

Jan 1, 1995

By Michele L. Bustamante, Gabrielle Gaustad

In recent years, t h e future supply of tellurium has been called into question due to the anticipated rapidly increasing demand from thin film cadmium telluride photovoltaics. Since tellurium is produced as a byproduct of other extractive processes – principally, the electrolytic refining of primary copper sulfide ore – it is important to explore the dynamics of the parent metal extraction and processing – in this case copper – when attempting to answer this question. This research explores the changing landscape of global copper production; introducing system diagramming and the concept of byproduct intensity (BPI) to illustrate concerning downward trends in tellurium supply potential. Upon closer inspection, it is concluding that, while a likely contributor to these downward trends, the increased use of non- traditional copper production techniques alone are not responsible; other factors include market substitution and incomplete data reporting. Additionally, a review of literature on tellurium recovery processing reveals a promising outlook for future supplies; highlighting potential for improvements in yield, which allow producers to make better use of what is available, even in the face of suppressed BPI.

Jan 1, 2014

By Hu Meilong, Liu Lu, Bai Chenguang

Extracting perovskite from high titanium-bearing blast furnace (BF) slag is a green and potential method to recover the second titanium resource. The non-isothermal crystallization process of perovskite in synthesized high titanium-bearing slag was studied in situ by confocal scanning laser microscope (CSLM) with cooling rate of 20 K/min. The results showed that perovskite was the primary phase formed during cooling process in the titanium-bearing synthesized slag (TiO2=23%). Perovskite started to precipitate at 1719 K and finally presented an orthogonal straight lines morphology.

Jan 1, 2014

By J. C. Yannopoulos

The quest for a continuous copper smelting and converting process, which has been going on for a long time, has not as yet reached its objective. The most recent efforts for the development of a continuous copper?making process started about two decades ago. Among the contending proposed processes, four have been piloted and three of them are currently in operation: the WORCRA process., the NORANDA process, the MITSUBISHI process, the OUTOKUMPU process. The WORCRA process, after some long pilot plant tests, failed to develop as an industrial process: The NORANDA process, as currently operating, is a smelting process and not a continuous copper?making reactor as initially conceived. The MITSUBISHI, although the only continuous process, has not been widely accepted. The OUTOKUMPU process can be applied only to a low iron concentrate feed and co?produces blister and high in copper slag. The thermodynamics of these "continuous" systems and the practical problems of their industrial application are reviewed and discussed. The achievement of efficient and inexpensive environmental control should' be the primary objective of any new process development. A review of the environmental problems of the copper industry indicates that the quest for a continuous smelting and converting furnace should be intensified.

Jan 1, 1983

By J. Hamisch

Climate policy regarding perfluorocarbons (PFCs) may have a significant influence on investment decisions in the production of primary aluminum. This work demonstrates an integrated analysis of the effectiveness and likely economic consequences of different climate policy options. In our study we first compare atmospheric observations to the available estimates of PFC emissions for the baseline years 1990 and 1995. We then present projections for regional emissions of PFCs from the aluminum industry using the MIT Emissions Projection and Policy Analysis model under different policy scenarios. Abatement costs for emissions of PFCs and C02 are compared in the context of the Kyoto Protocol.

Jan 1, 1999

By M. Girgis

The behavior of arsenic III during electrolytic refining of copper in acidic copper ?sulphate electrolytes was studied by different electrochemical methods such as, linear potential sweep, cyclic voltammetry, chronoamperometry and chronopotentiometry. The study showed that arsenic behaves as a depolarizing ion and has a deleterious effect on copper deposit. Three substrates; Pb, Cu and Ag were used during the refining process and the electrode kinetics were found similar for both Cu and Pb electrodes while a little difference was found for the Ag electrode. A microscopic study by scanning electron microscope was undertaken to show the influence of arsenic on deposit's morphology. Surface analyses of the deposit were carried out by some electronspectroscopic techniques such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that arsenic coexists with copper deposit at potential?~ -0.25 V.

Jan 1, 1987