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By Takeshi Nagano

Copper pyrometallurgy in Japan has experienced quite fundamental changes in last fifteen years. The severe environmental restriction coupled with increase of energy costs accelerated the development work of the new continuous process in Mitsubishi Metal Corporation. After several years of pilot plant test work the commercial plant was put into operation at Naoshima Smelter in 1974, the design capacity of which was 4,000 tonnes of copper per month. Many modifications and improvements have been incorporated into the process and 7,200 tonnes per month of copper production was achieved in 1983, proving that continuous process was much more economical than conventional process. It is now possible to design and operate the continuous process in wide range of capacity. This paper will review the process and describe the progress of the process in these 10 years. 311

Jan 1, 1985

By D. Raghavan

In recent years, the environmental issues related to the landfill shortage received considerable importance. Many polymeric solid wastes have high resistivity to chemical and biological degradation, and options are sought by which these wastes can be recycled and reused, or reduced in volume. The present study investigated the biodegradation of polyethylene by Aspergillus niger, and biodesulfurization of rubber by pure and mixed cultures of Thiobacillus thiooxidans and Thiobacillus ferrooxidans. The fungus, A. niger, was found to metabolize portions of polyethylene. Quantitative calorimetric measurements revealed that the amorphocity of the sample decreased during biodegradation. Removal of sulfur from synthetic rubber samples containing 2 to 15% sulfur, was studied in shake flask experiments and the associated oxygen consumption was studied in Warburg respirometers. The mixed bacterial cultures were more effective in the desulfurization of rubber samples than the pure cultures of T. thiooxidans and T. ferrooxidans. The data obtained in these studies may have far reaching consequence for the development of new effective processes regarding the remediation and management of discarded polymeric packaging wastes and car tire rubber materials.

Jan 1, 1993

By M. C. Furerstenau

Adsorption behavior of various surfactants on sulfide minerals is very much affected by the nature of the surface of the mineral. Since sulfides are naturally meta-stable, oxidation occurs when they are exposed to air, especially in aqueous environments. As a result. oxygen assumes a major role in sulfide flotation. Mechanisms of adsorption of various thiol collectors on sulfide minerals have been reviewed. The electrochemical behavior of various sulfide minerals has also been reviewed. Flotation behavior of galena, chalcocite, sphalerite, pyrite, chalcopyrite and pentlandite has been presented together with the. flotation of copper sulfide- nickel sulfide ore.

Jan 1, 1993

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 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 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 Craig A. Johnson

Cyanide speciation and behavior have been examined at three active heap leach operations, three heaps undergoing rinsing, and three sites with cyanide contaminated groundwater, all in the southwestern U.S. Data from these studies demonstrate that strong cyanometallic complexes of iron and cobalt can play ?an important role in cyanide behavior throughout the lifetimes of heap leach operations. In active circuits, we find evidence that significant amounts of cyanide combine with iron and cobalt to form strong cyanometallic complexes, and that these species can be adsorbed, probably onto iron hydroxides, or precipitated as insoluble cyanometallic compounds. When spent heaps are rinsed, the release of this cyanide is likely controlled by the slow kinetics of desorption from, or dissolution of, solids that have gone largely uncharacterized. We find evidence that strong cyanometallic complexes can give rise to transient free cyanide in some settings by rapid photo dissociation where heap rinse effluent is exposed to sunlight in open channels or translucent sample bottles. Thus, these species can complicate the ,preparation of spent heaps for decommissioning, even where regulatory standards ?are based on weak acid dissociable cyanide. There is a critical need for information on the form and stability of adsorbed and precipitated cyanide in spent ore heaps, on the concentrations of strong cyanometallic complexes in mineral processing effluents -particularly the complexes of cobalt, and on the natural attenuation of iron and cobalt cyanometallic complexes in both surface and subsurface waters.

Jan 1, 1998

By Malsuzaki. Kenji

A mathematical simulation model of the Imperial Smelting Furnace operation has been developed for purpose of improving the furnace operation. The model consists of top, shaft and bottom regions. Analysis in the shaft region is based on differential heat and materials balances taking account of reaction kinetics and heat transfer rates, and those in the top and the bottom regions are based on heat and materials balances under a steady-state condition. Longitudinal distributions of process variables such as temperatures of gas, sinter and coke, gas composition and fractional conversion under a practical operating condition were calculated. With this model, the furnace performance under various operating conditions also can be shown reasonably predicted.

Jan 1, 2003

By Kenji Matsuzaki

A mathematical simulation model of the Imperial Smelting Furnace operation has been developed for purpose of improving the furnace operation. The model consists of top, shaft and bottom regions, Analysis in the shaft region is based on differential heat and materials balances taking account of reaction kinetics and heat transfer rates, and those in the top and the bottom regions are based on heat and materials balances under a steady-state condition, Longitudinal distributions of process variables such as temperatures of gas, sinter and coke, gas composition and fractional conversion under a practical operating condition were calculated, With this model, the furnace performance under various operating conditions also can be shown reasonably predicted,

Jan 1, 2003

Several processes are now available for the recovery of free and WAD cyanide from gold plant solutions and pulps. In the past, the incentive for evaluating cyanide recovery in gold plant flowsheets has been economic. In many cases, it has been possible to demonstrate (at least in the laboratory and on paper), an improvement in process economics by; (i) reducing the costs of tailings detoxification, (ii) recycling cyanide at lower cost than the purchase/delivery price of new cyanide, and (iii) generating additional revenue via by¬product sales. Despite these convincing arguments, few cyanide recovery plants have been built at operating gold mines. Also, there is arguably an even more compelling reason for mining companies to consider cyanide recycling. With the growing storm of negative public opinion that the use of cyanide in the mining industry is attracting - following several highly publicized spills over the last couple of years - the time has come for the gold industry to demonstrate environmental diligence and stewardship in the use of this commodity that is so vital for their industry. There is no doubt that the widespread implementation of cyanide recycling will reduce the impact of the cyanidation process on the environment, both by reducing the risk of spills (with less cyanide being transported from manufacturing plants to gold mines), and by reducing the loading of toxic and non-toxic metals and ions in the tailings. In this paper, the various processes that are available for cyanide recovery are discussed, along with the process chemistry. Results of several laboratory and pilot plant trials that have been conducted over the last few years are also presented.

Jan 1, 1998

By A. M. T. S. Bandara

The solubility of rare earth (RE) salts in aqueous solutions depends on many factors including the type of cations and anions in solution, their concentrations, temperature and the type of solid precipitated. Experiments were conducted using anhydrous La2(SO4)3 and Ce2(SO4)3⋅8H2O as solids and lanthanum(III) perchlorate prepared by dissolving La2O3 in HClO4 solutions as RE-sources. Solutions of H2SO4, H3PO4 and their mixtures in the presence or absence of Na+, Ca2+, Fe(III) or Al(III) as perchlorates served as test solutions. Saturated solutions and precipitated solids were assayed and characterized using standard techniques to show that the La(III) and Ce(III) ions precipitate as hydrated sulphates, phosphates or double salts with sodium, depending upon the solution composition. The change in solubility of RE-salts with solution composition and temperature is the result of the composite effect of changes in solubility products (pKSP) of salts, pKa of acids and other equilibrium constants for ion-association.

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

By Kafui Nyavor

The indirect, and the direct contact mechanisms of bacteria oxidation of sulfides were studied using Thiobacillus ferrooxidans and pyrite. The aim was to determine which of the two generally aeeepted mechanisms played a dominant role, if any, during acid mine drainage (AMD) formation from the oxidation of sulfide minerals. The results show that at a pH of 4.5 where T. ferrooxidans are quite active, but where initial chemical oxidation of pyrite to Fe2+ is limited, the bacteria were unable to directly oxidize pyrite to any significant extent. Whereas, in the presence of Fe2+, T. ferrooxidallS assisted oxidation of pyrite by the indirect mechanism was observed and sustained over the pH and Eb range where the bacteria is active. The results lead to the conclusion that the direct contactmechanism of pyrite oxidition by T. ferrooxidans is insignificant. The predominant, and possibly the only, pathway involves the indirect bacteria oxidation of available Fe2+ to Fe3+, which in turn oxidizes FeS2 to generate additional Fe2+ and acidity in a cyclic process.

Jan 1, 1996

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 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 Heikki K. Jalkanen

Thermodynamic properties of copper-iron mattes and slag-matte distribution of copper and some minor matte constituents (Ni, Co, Mo, As, Sb and Bi) are discussed on? the basis of equilibrium measurements: a change from. oxidic to sulfidic solubility as the predominant form of dissolution of copper takes place as matte grade decreases. Distribution coefficients of minor matte constituents are complex functions of sulfur and/or oxygen potentials?. The distribution behaviour of different? metals can be qualitatively derived from their affinities to copper and stabilities. of their sulfides and oxides. The equilibrium results are compared with commercially observed values. from Outokumpu.Oy flash smelting furnace.

Jan 1, 1983

By Jan Smit

Sulphidic copper concentrates are generally processed by pyrometallurgical means; while oxidative pressure leach processing of such materials has been shown to be technically feasible, there has traditionally been little incentive to choose this route in favour of a smelting option. However, for concentrates with elevated arsenic levels, oxidative pressure leaching offers distinct advantages, as smelter air emission standards and restrictions on concentrate importation have tightened. The current state of pressure leach technology allows for high copper extractions from arsenical copper concentrates, while producing an environmentally stable process residue, without atmospheric emissions of sulphur dioxide or arsenic. In its studies on pressure leaching of copper concentrates, Sherritt has shown that arsenical feed materials can be converted into environmentally stable residues, with excellent copper extractions. The results of recent batch and pilot plant test work are discussed, including the deportments of copper, arsenic and precious metals.

By In-Hyeok Choi

Currently, spent V2O5–WO3/TiO2 catalysts contribute significant amounts of solid waste following increasing levels of global demand. V2O5–WO3/ TiO2 catalysts usually consist of TiO2 anatase as a supporting oxide, vanadium as a catalytic agent, and other promoters such as tungsten, silicon, and calcium. Although vanadium is the main catalytic agent, a relatively high content of tungsten (WO3, 7–10 wt%) typically exists compared to vanadium (0.5–1.5 wt%). Considering the irreplaceable properties and industrial importance of tungsten, a feasible method for the recycling of spent V2O5–WO3/TiO2 catalyst should be established to utilize it as a secondary source. This paper presents a process to recover tungsten from spent V2O5–WO3/TiO2 catalyst. The processes proposed here involving roasting, decomposition using HCl, ammonia leaching, and crystallization. Within the process, ammonium paratungstate (71 wt% as WO3) is obtained as a final product. The total yield rate of tungsten from feedstock was found to be 96.3%.

By T. Feldmann

Despite the ubiquity of applications for germanium, there is a lack of practically useful solubility data in acidic solutions. Previous studies were done at ambient temperature and only for commonly used acids (H2SO4, HCl). Hence, an investigation of the solubility of GeO2 in different acids was undertaken. Several inorganic and organic acids were studied in the concentration range of 1–11 mol/L and at 23, 40, and 60 °C. In the case of H2SO4 and HCl previous data was confirmed. Lower acidity resulted in a higher solubility for Ge at all tested temperatures. Tests done at 40 and 60 °C and low to moderate acidity levels, gave slightly increased solubility values at higher temperatures compared to 23 °C. This wasn’t the case at higher acidity levels, i.e., the solubility curves at different temperatures converge at high acidity. Lastly, a relationship of water activity and GeO2 solubility in different acid media was established.

By Raymond F. Dalton

Despite the ready availability of numerous zinc sources, the process of solvent extraction- electrowinning (SX-EW) has as yet found little favour in the zinc industry. It is suggested that this is largely due to the previous lack of availability of suitable selective reagents having the particular features required to enable them to fit in to a solvent extraction-electrowinning based process for zinc, particularly with regard to strength and selectivity for zinc over iron. This paper describes work on the development of new selective extractants for the recovery of zinc from both sulfate and chloride aqueous solutions and suggests how they might be integrated into new zinc processes.

Jan 1, 1994