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By H. Deveci

Bioleaching/biooxidation is essentially a dissolution process with the involvement of acidophilic bacteria acting as the "catalyst" to accelerate the dissolution of metals from sulfide minerals. The contribution of bacteria to the metal dissolution is closely controlled by the growth of bacteria, which is itself affected by the physico-chemical conditions within the bioleaching environment. There are a number of operating parameters controlling bioleaching processes, which are required to be maintained within a certain range in the leaching environment whereby the activity of bacteria with the resultant oxidation of sulfide minerals can be optimized. In this regard temperature, acidity, oxidizing conditions, availability of nutrients, oxygen and carbon dioxide, surface area and presence of toxic ions are of prime importance for control and optimization of bioleaching of sulfide ores/concentrates. Bioleaching processes are temperature and pH dependent with optimum metal dissolution occurring in a particular range where the bacterial strain is most active e.g. mesophiles at 35-40°C and pH 1.6-2.0. Provision of nutrient salts is required to maintain the optimnm growth and hence metal dissolution with the quantity of nutrients apparently being dependent on the availability of substrate i.e. head grade/pulp density of an ore/concentrate. Oxygen transfer is one of the most critical factors since the oxygen levels below 1-2 mgll may adversely affect the oxidizing activity of bacteria. Bioleaching rate tends to improve with increasing the surface area at low pulp densities but, in practice. the pulp density is limited to -20010 w/v. Increasing concentrations of ions such as cr may also adversely affect the oxidative activity of bacteria. Keywords: Bioleaching, Biooxidation, Acidophilic bacteria

Jan 1, 2003

By Tomás Vargas

The catalytic role of Thiobacillus ferrooxidans in the dissolution of chalcopyrite was studied by leaching pure massive samples of this sulfide with a pure strain of Thiobacillus ferrooxidans (ATCC 19859). Monitoring of the bacterial activity showed that an important fraction of the total bacteria generated during leaching remained attached to the chalcopyrite surface. Bacteria grown in the system, which were the offspring of bacteria adhered to chalcopyrite, was well explained as the result of the utilization of ferrous ion and sulfur as energy sources. The potential for indirect and direct action was fully utilized by the existing bacteria and the leaching process was controlled by the kinetics of chalcopyrite dissolution.

Jan 1, 1990

By Anna Franzkowiak, Dean Gregurek, Alfred Spanring, Angelika Ressler

In order to determine the most suitable refractory products and improve the lining lifetime for the diverse furnaces used in the nonferrous metal industry, corrosion tests are performed at RHI’s Technology Center. The practical facilities include the cup test, induction furnace, rotary kiln, and drip slag test described in this paper, which enable a comprehensive understanding of the chemo-thermal brick wear on a pilot scale. The corrosion trials are performed with actual slags generated during operations at a customer’s plant. To determine the highest influencing wear parameter, every single test is combined with a detailed mineralogical investigation and thermochemical calculations performed using FactSage. Based on the results, tailored refractory solutions for the nonferrous metal industry can be provided in combination with trials conducted at the customer’s site.

Jan 1, 2014

By Richard S. Kunter

Artech Recovery Systems, Inc has developed a low pressure and temperature? leach process called the "Cashman Process" to extract metals from arsenical flue dusts and residues and fix the arsenic in an environmentally stable form as ferric arsenate (scorodite). The process was pilot tested at Hazen Research in an integrated plant including continuous recycle from August 1989 to October 1989 during which several tons of flue dust were processed. Based on this pilot program, the process was deemed technically feasible and produced commercially salable products. Residues from this pilot program were subjected to a long-term stability test jointly designed by PTI environmental services and the USEPA. The process, its versatility, and the nature of the products is discussed in some detail.

Jan 1, 1992

By Mark Tjerkstra

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

Jan 1, 1998

By Laurent Cohen

Since the 1970s, Solvent Extraction (SX) in hydrometallurgical processes has been a key enabling technology in the production of high-purity metals. Examples include copper, rare earth oxides, uranium, cobalt and nickel. Notwithstanding incremental improvements in extractant formulations, few breakthroughs can be recounted in this industry outside of the initial amine-, oxime- or phosphine-based reagent chemistries. However, the advent of lithium-ion batteries and their stringent requirements for critical materials (lithium, cobalt and nickel) offer new challenges and opportunities for SX. Solvay recently introduced a new extractant for lithium, CYANEX® 936, and developed unique modeling software capabilities in cobalt/nickel separation using CYANEX® 272, zinc SX using DEHPA® and rare earth separations using CYANEX® 572. This paper discusses trends in SX and provides insight on processing of critical materials essential to energy sources. It also summarizes the technical and economic benefits based on extractant selection and advances in modeling.

By Kenneth L. Nash

The control of solubility of waste actinide ions, by conversion to highly insoluble mineral phases has been demonstrated in the laboratory. Actinide metal ions are removed from neutral pH solutions by a combined ion exchange-decomposition-mineralization process based on the application of the naturally-occurring hydrolytically unstable.polyphosphate organic compound phytic acid.

Jan 1, 1999

By S. M. Hay

The zinc content of blast furnace and basic oxygen furnace dusts is low compared with electric arc furnace dusts and it is generally not economical to treat the dusts to recover zinc. However, they have a high iron content and removal of the zinc would allow recovery of the iron values. A literature review and thermodynamic analysis was undertaken and, as a result, several smelting options were identified. This paper describes experiments undertaken to develop understanding of metallurgical aspects of these processes which are not amenable to theoretical analysis. Dusts from an Australian steelworks were characterised in order to determine their mineralogical make-up and the form of the iron. The processing aspects investigated in the laboratory were slag-metal equilibrium and solid-state pre-reduction using reducing gases of compositions expected from bath-smelting processes. Particular attention. was paid to the deportment of zinc, sodium, potassium, phosphorous and sulfur between the phases formed during smelting and pre-reduction. The smelting results indicate that less than 10% of the zinc, sulphur, sodium and potassium report to the metal. About 99% of the zinc and potassium and about 80% of the sodium could be volatilised from the dusts by reducing them at 1,000°C with mixtures of CO, CO2, H2 and H2O even when metallic iron was not formed. The experiments indicate that smelting of blast furnace and basic oxygen furnace dusts should produce hot-metal of a composition which can be blended into the main stream of hot-metal in the steelworks.

Jan 1, 1994

By J. Rajek

The novel multi-component, multi-particle, multi-phase precipitation model developed recently is used to predict the precipitation kinetics in complex 9-12% Cr steels investigated within the European COST 522 project. These steels are used for tubes, pipes, casings and rotors in USC (ultra super critical) steam power plants for the 21st century. In the computer simulations, the evolution of the precipitate microstructure is monitored over the entire production heat treatment starting with the casting process, including austenizing, several annealing treatments and in-service conditions. The main interest lies on the concurrent growth and coarsening interaction of different types of precipitates. Keywords: Precipitation kinetics, heat treatment, power plant steels, simulation

Jan 1, 2003

By Melinda Channel, Alan W. Weimer, Jonathan R. Scheffe

"There is a need to develop cost effective renewable energy processes for the production of clean fuels that can simultaneously mitigate the U.S. energy/global environmental security issue. If H2 can be obtained cost effectively via the splitting of water using concentrated sunlight, then it’s possible to operate a fuel cell using renewable H2 or to synthesize other fuels based on renewable H2 for generating electricity or for running internal combustion engines. For example, H2 can be reacted with sequestered carbon dioxide (CO2) to produce syngas (H2/CO) via reverse water gas shift (RWGS), i.e. H2 + CO2 ? CO + H2O. The syngas can be catalytically methanated to form synthetic natural gas (SNG) or it can be catalytically reformed to produce liquid fuels such as “green” gasoline via the MTG process (syngas? methanol ? gasoline). The desert SW United States is home to world class sunlight. Fundamental ferrite thermodynamics will be reviewed, an example of the beneficial effect of ferrite surface area on reaction kinetics will shown, and process economics will be investigated for a 100,000 kg/day facility to produce H2.Introduction and Background ThermodynamicsSpinel ferrites of the form MxFe3-xO4, where M generally represents Ni, Zn, Co, Mn, or other transition metals, have been shown to be capable of splitting water according to the two step cycle shown below:MxFe3-xO4 + solar thermal energy ? xMO + (3-x)FeO + 0.5 O2 (1)xMO + (3-x)FeO + H2O ? MxFe3-xO4 + 2H2 (2)This is an inherently clean and sustainable process, as the only net inputs are solar energy and water, and the net outputs are hydrogen and oxygen. Ferrite water splitting cycles are advantages compared to other high temperature water splitting cycles, such as the ZnO/Zn and Mn2O3/MnO cycles, because thermal reduction has been demonstrated at significantly lower temperatures[1, 2]. As a result, overall efficiency may be increased due to the fact that radiation losses increase as the fourth power of temperature, and material considerations for reactor design should be more flexible. Additionally, cycle repeatability has been demonstrated with relative ease as compared to other thermochemical cycles [3-6]. However, the amount of hydrogen per mole that is generated is significantly less than for other high temperature thermochemical cycles due to the fact that only Fe3+ is capable of being reduced at the temperatures of interest[6]. In addition, water oxidation kinetics appear to be very slow, likely due to diffusion or surface area limitations created by near surface oxidation [6, 7]."

Jan 1, 2010

By Alan P. Prosser

The heap leaching of gold ores by cyanide solution was simulated by computer program. The program uses only basic m1neralogical and chemical data; no process testwork data, such as column leach results, are required. The simulation can be used to forecast the consequences of various changes before and during the testwork, design and operation stages of a particular ore-process system. Also, data about the state of different parts of the heap at various times help create an understanding of what is happening. The effects of mineralogical and process variables on the overall performance of the ?heap leaching process are illustrated. Comparisons are made to column leach tests and production data. The potential of the simulation strategy is discussed for making better use of operating experience and for suggesting specific research objectives. It has become clear that more attention should be paid to other metals that dissolve in the solution.

Jan 1, 1989

By S. Seetharaman, Du Siehen

"In the processing of molten metals, it is extremely important to monitor continuously the concentration levels of various minor elements. In the production of common metals like copper, iron and aluminium electrochemical sensors involving solid as well as liquid electrolytes are being increasingly used to measure the concentrations of minor elements. The present paper deals with the electrochemical principles underlying these measurements and the possible errors involved. One of the major difficulties in the case of the solid electrolytes is to correct for the consequences of the electronic contribution to the conduction of the electrolyte.The application of the electrochemical sensors for molten metals processing involves designing of these probes to withstand the industrial operating conditions. In this respect, significant achievements have been made with respect to the design of oxygen probes for liquid metals in general and liquid copper in particular. Some of the salient design features are discussed in the paper. The application of auxiliary electrodes for impurities in molten metals like phosphorus in copper and silicon in iron are taken up. The development of oxygen sensors for slags is given special attention. Recent developments in the field of sensor technology, as applied to metals processing are highlighted.1. IntroductionThe rapid technological advancement today require precise control of the process parameters and the impurity levels. Most of the molten metals processing in industrialized countries are often steered by suitable computer models, either phenomenological or simulations based on theoretical principles. These models often require that the process parameters are continuously monitored so that the progress is followed and modified suitably as and when required. It is common practice to measure temperatures by incorporating temperature sensors at the various strategic points of the reactor. In the case of monitoring the composition changes in the various phases, the method of sampling followed by routine chemical analysis involves a time lag as well as uncertainties in sampling and analysis. In this respect, electrochemical sensors have the advantage of generating accurate data when properly applied and increasing attention is being paid in the development of electrochemical sensors for various common species in molten metals processing. In the present paper, the developments in this area over the years are outlined and typical process applications are discussed. A greater emphasis will be laid on sensors based on oxygen conducting electrolytes and their application to the production of common metals like iron and copper."

Jan 1, 1996

By E. Ozberk

The copper and nickel smelting industries are important contributors to the technical and economic well-being of Canada while some of the smelters are among the largest sources of sulphur dioxide emissions in Canada. A review of the operations in six smelters - Falconbridge Limited, Falconbridge, Ontario; Hudson Bay Mining and Smelting Co. Limited, Flin Flon, Manitoba; Inco Limited, Copper Cliff, Ontario and Thompson, Manitoba; Noranda Mines Limited, Horne Division, Noranda, Quebec and Gaspe Mines Division, Murdochville, Quebec - have shown that about 80% of the total sulphur input to these smelters was emitted to the atmosphere in 1980. A simultaneous review of the existing and emerging technologies which can directly or indirectly reduce the sulphur dioxide emissions indicated that it is possible to reduce the emissions to below 20% of the sulphur input to these smelters. This can be achieved by varying degrees of modifications to the smelting operations and installing sulphur fixation facilities at significant costs which may increase the metal production costs. This would consequently make the competitiveness of the Canadian copper and nickel producers more difficult in the already tough world metals market.

Jan 1, 1983

By R. H. Lien

The Bureau of Mines, U. S. Department of the Interior, is investigating chemical and biological decontamination of complex wastewaters such as tailings pond water containing 280 ppm CN and 5 ppm Se as well as significant concentrations of arsenic, copper, iron, silver, and zinc. The most effective chemical procedure involves cyanide oxidation using hydrogen peroxide or sodium hypochlorite followed by selenium reduction using ferrous hydroxide. The effluent contains <l ppm CN and 20 ppb Se; concentrations of other major contaminants meet EPA drinking water standards. Preliminary research indicates that biological cyanide oxidation is possible even in highly alkaline solutions (pH 10.5) containing high cyanide concentrations; indigenous bacteria destroyed 85 pet of the cyanide. Exploratory research shows that other bacteria removed up to 79 pet of the selenium from chemically oxidized, low-cyanide water. These promising results may lead to a final processing scheme that involves a combination of chemical and biological techniques.

Jan 1, 1990

By Clemens Schmetterer, Patrick J. Masset

"The surface tension represents an important property for the modelling of high temperature processes. In this study the surface tension of two Al2O3 – CaO – SiO2 model slags and the influence of the admixture of 5 up to 30 wt.% FeO were studied. The surface tension measurements were carried out using the sessile drop technique on BN substrates under Ar atmosphere (10-6 atm O2) up to 1500 °C.IntroductionThe aim of VIRTUHCON1 is the virtualization of high temperature conversion processes, a task that requires thorough understanding of these processes. In many of these conversion processes slag plays an important role to control the properties of the product, to protect the reactor lining or simply as waste. Slag surface tension is one of the materials properties that is needed for the description of such processes, since it influences the interactions between the components in the reactor, e.g. at the slag – Fe interface in the blast furnace.Surface and interfacial tensions have thus received considerable attention in research, but the number of investigations in this particular pseudo-quaternary system is surprisingly low. Furthermore, the literature data are subject to different measurement conditions and techniques which complicates the data analysis and comparison.The slag atlas [1] offers a compilation of the available literature until 1986 (shown in Table I), but literature search has not revealed more recent studies of this system until now. For example, Elliott and Mounier [2] determined the surface tension of ACSF slags using the double tube maximum bubble pressure technique at 1200 °C. They kept their slags in contact with Cu-S-F mattes, and the slag therefore contained a certain amount of sulphur which acts as a surfactant and lowers the surface tension. The compositions of their slags were scattered over a wide composition range and they did not use a common ACS base mixture for their tests, either. The surface tension values vary between 417 and 446 mN/m, but due to the reasons just mentioned no trend in the measurements can be observed and the influence of FeO admixture on the surface tension cannot be deduced. Further information including the temperature dependence is available from Pavlov et al. [3], Ishchanov and Shushkov [4] and Murav’eva and Kaplun [5]; the diagram on page 446 in Ref. [1] has been drawn from these sources. Both positive and negative temperature coefficients are reported in these works. SiO2 is the only pure constituent that has a positive temperature coefficient [6], but a correlation of the temperature coefficient with the SiO2 content was not found to be conclusive."

Jan 1, 2011

By Takafumi Kondo, Satoshi Yamashita, Noboru Masuko

"Aqueous oxidation of phosphite ions to phosphate ions with dissolved oxygen was examined at 80° C and pH 4.5 mainly from the stichiometric point of view. Dissolved oxygen alone can not oxidize sodilim phosphite in aqueous solution, but when sulfur dioxide is coexistent, cooperative oxidation for both sulfite and phosphite can occur in aqueous solution. Sulfur dioxide itself is well known as a reducing agent, but it also reacts as an oxidation-promoting agent for other species under a certain condition. So sulfur dioxide is· a promising cheap reagent for waste phosphite processing.IntroductionIn a liquid-phase oxidation reaction using the dissolved oxygen gas, the eoexistence of a copper salt is required generally. Recently, it was reported that the oxidation reaction progressed by using mixed gas of sulfur dioxide and oxygen without the copper catalysis, and the attention has been collected1·3). The present authors also noticed the phenomenon since the early time and have been studying on the reaction mechanism of sulfur dioxide in liquid phase oxidation 4l. It was found that; by using the SO2-O2 mixed gas, the oxidation of phosphite ions to phosphate ions proceeded efficiently in sulfuric acid solutions. In the present report, the applicability of SO2-O2 mixed gas as a cheap oxidizing agent to the industrial processing of the waste solution of electroless nickel· plating is investigated. It is well known that the sulfur oxide dissolved in aqueous solution is oxidized ·by the oxygen in the air to sulfuric acid according to the following equation"

Jan 1, 2000

By Peter G. Cooper

"During 1987, the feasibility of modernising the ER&S smelter at Port Kembla, NSW, Australia was studied. The selection of appropriate technologies to carry the smelter into the 21st century considered issues such as capital cost, existing infrastructure, feed mix, capacity, product quality, flexibility and potential for further development. Both hydrometallurgical and pyrometallurgical process schemes were considered. Some novel combinations were assessed but ultimately rejected. Final technology selections included proven smelting and anode furnace processes, pyrometallurgical slag cleaning and modifications to existing equipment. This process scheme balanced risk against development potential within the constraints imposed by the existing plant.BackgroundThe Electrolytic Refining and Smelting Company of Australia (ER&S) has operated a custom copper smelter at Port Kembla since 1908. Existing technology includes a sinter plant/blast furnace, three small Peirce Smith converters, two reverberatory anode furnaces and a conventional tankhouse. These process units were all installed prior to 1960 and have proven to be flexible enough to process the wide variety of domestic feed materials purchased by ER&S.However, by the early 1980s, threats to domestic concentrate supplies highlighted the need for major changes to reduce operating costs to world competitive levels. Various studies in the ensuing years failed to identify an economically attractive solution. Furthermore, pressures were increasing to improve the environmental performance of the smelter.During 1986 the options for redevelopment were again considered and by the end of 1987 technologies for the retrofit had been selected and a full feasibility study was completed."

Jan 1, 1988

By Pesic. Batric

A novel chitosan-pyridoxal-epichlorohydrin was synthesized and evaluated in our laboratories. The evaluation was achieved by performing kinetic and equilibrium studies of copper sorption. The parameters examined were pH, temperature, concentration of copper, particle size and selectivity of copper sorption against iron, zinc, cadmium and cobalt. It was found that pH was the most important parameter, and sorption of copper increased with pH increase in the range pH 2.5-6.0. The low activation energy of the sorption reaction, 1 1.13 kJ/mole (2.66 Kcal/mole), showed that temperature was not an important parameter. The synthesized chitosan was selective against iron, zinc, cadmium and cobalt. The selectivity with respect to last three metals was achieved by the kinetic difference of sorption, as sorption of copper was much faster than for other metals. Iron (Fe2+) does not adsorb on chitosan. The mechanism governing the sorption of copper is intraparticle diffusion. This finding was supported by the dependance of copper sorption on the square root of time, the low activation energy, and the fit of experimental data in the diffusion through the product layer equation.

Jan 1, 1994

By J. Bostjancic

As wastewater discharge regulations become more stringent, power plants, manufacturing plants and other industrial sites are looking for ways to reduce makeup water requirements and to recycle and reuse as much wastewater as possible. In some cases, environmental regulations require zero liquid discharge, meaning all wastewater must either be retained on site or reduced to solids for disposal off site. Zero liquid discharge or "closed-loop" wastewater treatment systems using evaporators and other process equipment have been well-accepted in recent years. Often overlooked is the fact that zero discharge is not just the latest fashion--many commercial zero liquid discharge systems have been in operation since the mid-70&apos;s. This paper will give specific examples of zero liquid discharge operations from 1974 to the present, showing how evaporation equipment and processes have changed to meet the requirements of industry and environmental regulations.

Jan 1, 1996

By J. L. Jambor

Previous crystal-structure determination of magnesian annabergite (Ni,MgMAsO4)2 8H2O indicated that ordering of Ni and Mg occurs in non-equivalent octahedral sites; such ordering supports the possibility of miscibility gaps on the Ni3(AsO4)2 8H2O -MgiAs04)2 8H2O. (annabergite-hornesite) join. In a predecessor study based on analyses of natural specimens, it was proposed that solid solution is incomplete both for annabergite-hornesite and annabergite-erythrite [Co, (AsO4)2 8H2O]. In the current study, syntheses by use of a slow-addition technique and aging of the precipitates indicated that the annabergite-erythrite solid solution is complete, and that no miscibility gap is present on the annabergite-hornesite join to at least 58 mol % Mg. Thus, interpretation of the compositions of these phases in oxidized mill-tailings impoundments can be done with the normal precautions for homogeneity, and without the added concern of the possible presence of miscibility gaps in the ternary system.

Jan 1, 1995