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By C. R. Palmer

The Bureau of Mines investigated the use of ion-exchange technology for the recovery of precious metals from cyanide leach and spent electrolytic solutions. This research included adsorption of gold and silver on both weak-and strong-base anion-exchange resins. The effects of nickel, mercury. and iron on precious metal loading of strong-base resins were also determined. Due to the nonselectlvity of strong-base resins, selective elution also was investigated. Both commercially available and experimental weak-base anion-exchange resins were tested. None of the commercial weak-base resins tested were suitable for a caustic-cyanide system owing to their low recovery of precious metals at pH 10 or above; however, three experimental resins have possible application. Continuous tests conducted with mill cyanide solution in a multicompartmented ion-exchange column using strong-base anion-exchange resins adsorbed nearly 100 pct of the precious metals as well as the iron and nickel. During the elution of this loaded resin the iron was first removed with NaCI plus NaOH; then nickel with dilute H2S04 or HCl; finally gold and silver with thiourea in dilute HCl.

Jan 1, 1988

By Sharif Jahanshahi

Calcium ferrite slags are often associated with Professor Yazawa due to his pioneering work on the thermodynamics of this type of melts. Over the past years CSIRO has invested some effort in studying physico-chemical properties of such melts to fill in some gaps in our knowledge and explore opportunities for application of the understanding developed. These investigations cover thermodynamics, transport properties of calcium ferrite based slags, as well as the kinetics of reactions of such slags with refractories. The present paper provides an overview of some of these studies and highlights some of the interesting behavior of such melts. The oxidation state of copper and arsenic in calcium ferrite based slags are predominantly Cu+ and As3+, respectively, at oxygen potentials below 10.1 atm. The concentration ofCu2+ in such slags becomes significant at oxygen potentials of greater than 10'1 atm at 1300 ?C. The activities of CuOo.s and AsOl.S in calcium ferrite slags show strong deviations from the Raoultian Law, while that of CoO is very close to ideal behaviour with respect to pure solid CoO. Addition of Si02 to calcium ferrite slags can have significant effects on the activities of FeO and Fe2O3 and hence the stability of magnetite phase. Transfer of oxygen in calcium ferrite slags is fast with diffusivity of 2xlO?3 cm2/s at 1350 °C and activation energy of 16 kcal/mol Presence of solid phases, such as magnetite, has pronounced effect on the viscosity of calcium ferrite slags. The observed dependence on solid loading and shear rate indicates deviation from Newtonian behaviour. The interfacial tension between copper mattes and calcium ferrite slags is strongly dependent on the matte grade, with the determined values being much lower than the corresponding ones for interfacial tension between similar mattes and iron silicate slags. MgO, Cr2O3 and MgCr2O4 have low solubility in calcium ferrite slags and their solubility increases with increasing copper oxide content of the slag at 1300 °c. The oxidation state of the slag has strong effects on phase transformation, dissolution rate and disintegration of refractories in calcium ferrite slags. Other key factors with major impact on slag-refractory interactions include viscosity and surface tension of slags as well as the contact angle between slag and refractory material.

Jan 1, 2003

By Sharif Jahanshahi

Calcium ferrite slags are often associated with Professor Yazawa due to his pioneering work on the thermodynamics of this type of melts. Over the past years CSIRO has invested some effort in studying physico-chemical properties of such melts to fill in some gaps in our knowledge and explore opportunities for application of the understanding developed. These investigations cover thermodynamics, transport properties of calcium ferrite based slags, as well as the kinetics of reactions of such slags with refractories. The present paper provides an overview of some of these studies and highlights some of the interesting behavior of such melts, The oxidation state of copper and arsenic in calcium ferrite based slags are predominantly Cu+ and As3+, respectively, at oxygen potentials below 10-7 atm. The concentration of CU2+ in such slags becomes significant at oxygen potentials of greater than 10-7 atm at 1300 °C. The activities of CuO0.5 and AsO1.5 in calcium ferrite slags show strong deviations from the Raoultian Law, while that of CoO is very close to ideal behaviour with respect to pure solid CoO. Addition of SiO2 to calcium ferrite slags can have significant effects on the activities of FeO and Fe2O3 and hence the stability of magnetite phase. Transfer of oxygen in calcium ferrite slags is fast with diffusivity of 2x 103 cm2/s at 1350 °C and activation energy of 16 kcal/mol. Presence of solid phases, such as magnetite, has pronounced effect on the viscosity of calcium ferrite slags. The observed dependence on solid loading and shear rate indicates deviation from Newtonian behaviour. The interfacial tension between copper mattes and calcium ferrite slags is strongly dependent on the matte grade, with the determined values being much lower than the corresponding ones for interfacial tension between similar mattes and iron silicate slags. MgO, Cr2O3 and MgCr2O4 have low solubility in calcium ferrite slags and their solubility increases with increasing copper oxide content of the slag at 1300°C. The oxidation state of the slag has strong effects on phase transformation, dissolution rate and disintegration of refractories in calcium ferrite slags. Other key factors with major impact on slag-refractory interactions include viscosity and surface tension of slags as well as the contact angle between slag and refractory material,

Jan 1, 2003

By Susumu Okabe

Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the' side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.

Jan 1, 1998

By G. E. Lagos

This paper analyses the scope and instruments employed by the Basel Convention for regulating the transboundary movement of hazardous wastes, the present and projected hazardous waste regulations of Chile, reviews the Chilean import/export trade of wastes of the period 1985-1995, and discusses, the influence that the Basel Convention has had on mining trade, its perceived benefits and costs, and possible effects on Chile's trade of the application of the Convention's Decision III/l. There is no quantitative estimation as to the effect of the Convention on the general volume of imported or exported materials destined for recovery, recycling, reclamation, or reuse. All recycling imports, with the possible exception of residues of petroleum oil, which occurred during the decade 1985-1995, can be classified tentatively as non hazardous. The entry into force of the Convention has had several effects on Chile's trade. It has brought home the need to have a comprehensive hazardous waste legislation, it has been a base for applying import restrictions, which in all likelihood, would .have otherwise not been applied, The benefits and costs of this import restriction, as well as those of the multilateral export ban are analyzed.

Jan 1, 1999

By A. Elizabet Serna

The weak acid is a by product obtained in a pre-treatment of gases from a copper smelter prior to sulfuric acid manufacture and the main components of this weak acid are: sulfuric acid. copper, arsenic. antimony, bismuth and iron. Usually, this effluent is neutralized with lime and the solid residues are stored in a landfill as a hazardous waste. This work was directed at determining the optimal conditions to recover copper from weak acid using a cementation process before the neutralization of the effluent. The variables investigated are: Effluent temperature, iron scrap amount and acid concentration versus reaction time. The results of these experiments show that the cementation process of copper and the co-cementation of impurities such as arsenic, antimony and bismuth were in accord with the theory of the electrode potentials.

Jan 1, 1996

By Ludovic Charpentier

Production of metallic wires directly from liquid jets would avoid drawbacks of extrusion (space needed, damaging, cost?) and enable recycling. But liquid jets tend to break, due to capillary instabilities, unless a solid layer (coating or start of solidification) surrounds it. We recently developed a process to produce tin wires, cooled by water flow parallel to the jet. Superficial oxidization of tin produces a glass coating around the jet. Studies showed the length of wires increased when increasing speed of tin jets, and that water average speed should be the closest possible to the jet one to have smooth fibers. Producing 1 mm diameter wires is possible. The length of wires is limited by the experimental setup, which does not provide possibilities to coil the wire. Most of other metals do not generate glass-like oxides. The lack of coatings makes it necessary to reduce the capillary instabilities to obtain fibers.

Jan 1, 2006

By Jing Zhan, Tian-zu Yang, Wei-feng Li, Li-Hua Jiang, Shi-yan Xu, Jian-yang Huang, Chuan-fu Zhang, Yan-qing Fan

The amount and activity of coal, reduction temperature and other parameters of the process of bottom-blown reduction of liquid high lead slag were investigated in laboratory. Methods to strengthen the bottom-blown reduction process were studied by industrial production. The results were in the follows: the reduction temperature was 1150℃; reduction time was 1.5h; the reductant was anthracite; lead content in slag was controlled to 2%; the rate of coal was 7% and gasification loss of coal in high temperature was severe; liquid lead slag reduction rate was faster with coal; prolonging the reaction size had little effect on reducing lead in slag; the size of the reactor can be further reduced.

Jan 1, 2015

By Oscar J. Restrepo

Through reactions in solid form at high temperatures, using iron oxide (Fe3O4) and chromium oxide (Cr2O3) in fixed proportions as precursors, the compound was synthesized with spinel structure type FeCr2O4. For different temperatures synthesis was conducted the characterization of the material obtained through X-ray diffraction (XRD), spectroscopy UV-VIS-NIR, scanning electron microscopy (SEM), energy dispersion analysis of X-ray (EDX) thermal analysis (DTA / TGA) and magnetic susceptibility of alternating current. The changes in the spectra of reflectance changes are related to the phase identified, the degree of crystalline structure, the spatial order of cations and the magnetic behavior obtained.

Jan 1, 2009

By David T. Hobbs

Large quantities of highly alkaline, radioactive, liquid wastes are stored in underground tanks throughout the Department of Energy complex. These wastes will be pretreated to separate radionuclides and the remaining decontaminated liquid wastes incorporated into solid waste forms for permanent disposal. Significant savings in disposal costs could result by recovering .the sodium as sodium hydroxide for reuse or disposal as nonradioactive waste. Recent testing demonstrated an electrochemical separation process for the recovery of sodium hydroxide from alkaline waste solutions; The separation process uses ion-selective membranes to separate sodium from the bulk of the waste constituents under an applied electrical field. The sodium is recovered as a 10-15 wt % solution of sodium hydroxide. Results of bench-sc3Ie and pilot-scale tests with simulated and radioactive waste solutions are presented.

Jan 1, 1999

By Ting Liu, Qian Li, Peng Deng

The wastewater containing Hg2+ and Pb2+ does great harm to the environment and human bodies. Traditional wastewater treatment cannot fundamentally put a stop to heavy metals pollution for producing secondary pollution. In this paper, Hg2+ and Pb2+ in wastewater were removed and recovered by sulfide precipitation- flotation. Sodium sulfide was used as precipitant and butyl ammonium aerofloat was used as collector. Results indicated that Hg2+ and Pb2+ could be reduce to less than 0.03mg/L and 0.16mg/L respectively by both coprecipitation- floatation and fractional precipitation- floatation. In these two methods, fractional precipitation flotation could not only remove Hg2+ and Pb2+ from wastewater, but also could recover mercury and lead effectively. The infrared spectrograms showed that the adsorption between butyl ammonium aerofloat and mercury precipitate or lead precipitate is chemisorption.

Jan 1, 2015

By Gerhard Bayer

X-ray and thermoanalytical studies were carried out on the formation and stability of Ca-, Mg-and Mn-tungstate, and of the corresponding minerals scheelite and wolframite. The tungstates were synthesized by different methods: precipitation from solution, solid state reactions, displacement reactions with solutions and in the solid state. The reactivity of natural scheelite and wolframite with different salt solutions and in mixtures with other minerals was investigated.

Jan 1, 1989

By Patrick M. Eduafo, Brajendra Mishra, Mark L. Strauss

Direct acid leaching of rare earth metals (REMs) from waste lamp phosphors is non-selective, leading to co-dissolution of impurities mainly calcium, phosphorus, silicon, iron and zinc. Calcining the phosphor powder at different temperatures followed by leaching with HCl isn’t efficient for the extraction of all the chief rare earths especially cerium (Ce), lanthanum (La) and terbium (Tb). Therefore, multi-stage leaching operations are required for the separation of the REMs in phosphor dust. This paper will outline a new process for extracting Ce, La, Tb, Eu and Y from waste fluorescent lamps using a three-stage leaching and separation process. A flowsheet has been developed which shows this process is selective and efficient.

Jan 1, 2015

By J. H. Puffer

The copper mineralization of the Mesozoic Passaic Formation of New Jersey is typical of copper deposits in eastern North American Mesozoic sediments. Most such deposits are located at the base of the first of several basalt flows that are interbedded with continental, red-bed sediments. The copper mineralization is similar in most respects to that of the Keweenawan Basalts of the Lake Superior area. The first basaltic flow units of the eastern North American Mesozoic basins, and the Keweenawan Basalts, are continental quartz tholeiites of similar chemical composition and copper contents. The copper minerals and associated zeolite facies metamorphic mineral assemblages of these two rock units are also approximately the same. Stoiber and Davidson (1959) suggested that Keweenawan copper was mobilized and concentrated during metamorphism. The evidence pertaining to the Mesozoic copper deposits of New Jersey is consistent with such an interpretation and also with DeVore's (1955) suggestion that ore fluids commonly arise as a result of the mobility of metals under metamorphic conditions. There is additional evidence that final metamorphic concentration of Mesozoic copper was preceded by an initial stage of hydrothermal precipitation related to fluids emitted by basaltic magma.

Jan 1, 1987

By Brandon R. Ball

An investigation of the effects of ozone and ozone-induced hydroxyl radical on reducing whole effluent toxicity is described and discussed relative to the application of ozone for industrial water treatment. Results from operation of an ozone system treating industrial effluent from a lead and zinc mine in Colorado are presented. The mine discharges 1,000 gpm of wastewater into a tributary of the Arkansas River and has historically exceeded Whole Effluent Toxicity (WET) limits and on occasion has exceeded numeric limits for copper, ammonia, and cyanide. Based on results of a Toxicity Identification Evaluation (TIE) conducted on the effluent and individual process waste streams, the source of effluent toxicity is believed to be primarily associated with organic reagents used in the milling process. Based on test results, an applied ozone to COD ratio of 3: 1 by weight and a contact time of 30 minutes was found to be effective for reducing whole effluent toxicity at pH 11 but not at pH 7, indicating oxidation by hydroxyl radical to be the dominant mechanism responsible for toxic-ity reduction. At an applied ozone to COD ratio of 3:1 and a pH of 11, toxicity was improved from 0 percent survival to 100 percent survival for Ceriodaphnia dubia and fathead minnow (Pimephales promelas) based

Jan 1, 1996

By Hiroaki Kawamura, Takeshi Yoshikawa, Kazuki Morita, Yutaka Yanaba

"To develop an alternative metallurgical process for phosphorus removal in the production of solar-grade silicon (SOG-Si), slag treatment of metallurgical-grade silicon (MG-Si) was conducted, followed by acid leaching. Phosphorus-doped silicon alloy or MG-Si containing certain amounts of phosphorus and calcium was reacted at 1723 K and 1773 K with CaO--CaF2 of several compositions. Phosphorus removal from the molten silicon into the slag phase was confirmed by reduction to phosphide ions, P3-, and phosphate ions, P3-. These ions were separately determined using a wet chemical analysis method developed by ourselves. The highest phosphorus distribution ratio obtained was 2. 7 after reaction for 18 h with 17.5 mass% CaO--CaF2 slag. We then conducted acid leaching of the silicon and achieved removal of a large fraction (over 90 % ) of the phosphorus, which was much higher than that obtained by ordinary oxidizing slag treatment.IntroductionIn recent years, the production of solar cells has been increasing rapidly. Because of this, the demand for solar-grade silicon (SOG-Si) has also been growing rapidly. The development of lower-cost mass production processes is therefore needed to provide silicon feedstock. Phosphorus is one of the impurities in metallurgical-grade silicon (MG-Si). Because of its large segregation coefficient (kp = 0.35) [l ], it is difficult to remove phosphorus using a solidification refining process. Vacuum melting is considered to be a promising method for removing phosphorous from MG-Si [2], but the issues of high cost and large energy consumption have still to be resolved.Slag treatment is often used to remove impurity elements by oxidizing reactions during general oxidation refining processes. For example, phosphorus in molten steel is removed into a slag phase as phosphate ions, PO4 3-l-, by the following reaction:"

Jan 1, 2013

By Frederick W. DeVries

The author was invited by "60 Minutes Australia" to provide on-site technical background on cyanide, mining, and the environment, in their investigation of the January 30, 2000, spill at the Aurul gold-recovery site in Baia Mare, Romania. Some remarks on the incident ?and its implications surround a showing of the fourteen-minute telecast. The thrust of the TV reporter was that aspects of the dam implied the owners' use of standards Jess than would have been met for installations in technologically more advanced locations (like Australia). As a result, the public-relations impact is one of embarrassment for the world mining industry.

Jan 1, 1998

By Ladislav Bebar, Tomas Parizek, Radek Dvorak, Petr Stehlik

"More and more sweeping environmental regulations initiate research, development and introducing into operation up to date technologies for cleaning off-gas and flue gas generated in various branches of industry and municipal waste treatment. The following systems based on novel types of equipment are shown: thermal and catalytic treatment of waste gases polluted by VOC (Volatile organic compounds) and carbon monoxide (alternatively NOx), catalytic filtration for efficient destruction of PCDD/F (dioxins) and potentially NOx, wet cleaning of flue gases polluted by SO2, HCl and HF with a original type of homogenizer “O-element”, integrated equipment for cleaning waste gases polluted by solid particulates, SO2, HCl, HF and heavy metals (alternatively NOx or PCDD/F). The outstanding features of all equipment mentioned above are low investment and operating costs together with high removing efficiency of pollutants. These units can be used mainly in incineration plants, refineries and other chemical plants. The paper represents a review based on papers published in reputable international journals and a monograph under preparation as well as on experience from industrial applications.IntroductionIn the recent years, more and more emphasis is put on preserving clean environment. One of the most closely monitored objects of general public attention are exhaust gases, containing a number of undesirable compounds like NOx, CO, SO2, HCl, HF, fly ash a PCDD/F. These harmful species are created in chemical processes mainly in the industry, transport and energy sectors. There is therefore a strong impetus for abatement of these harmful pollutants. Sectors of industry are thus subject to emission regulations specific to various types of units. In the framework of increasing demand for a clean environment, the concerned legislation is becoming increasingly strict and requires removal of pollutants by modern methods that would ensure efficient abatement of emissions at reasonable investment and operating costs.Attention is focused chiefly on methods for decreasing harmful emissions from thermal waste treatment facilities processing industrial and municipal waste that may be subsequently applied in other sectors of industry. Units for the thermal treatment of waste not only provide means of its disposal, but may become also important sources of energy, provided that strict emissions limits are satisfied. Figure 1 compares emission limits given by the legislation for municipal waste incinerators and limits for a selection of energy sources with heat capacity up to 50 MW (see EU regulation 200/76/EC). The Figure implies that the values of emission limits for waste incineration are mostly comparable with emissions from the combustion of natural gas. Thanks to the continuing improvements of the methods for removal of harmful pollutants, the emissions from waste incinerators are typically deep below the limits."

Jan 1, 2008

By Pinakin C. Chaubal

An industry ? university consortium was set up to develop advanced tools necessary to understanding of the various phenomena occurring in the hearth of the modern iron making blast furnace. The major driver for this work was to provide the technological support required to extend campaign life of blast furnaces, which, by current agreement is tied to the life of the furnace hearth. The hearth wear is significantly affected by the hot metal velocity, temperature distribution and refractory temperatures. Due to the difficulty in making measurements inside the hearth, novel approaches to gain a fundamental understanding of the detailed physical and chemical processes in the hearth must be developed. The approach used in this project was to develop a 3-D CFD (Computational Fluid Dynamics) model coupled with extensive validation efforts. The CFD model is being utilized (1) to understand the phenomena in the hearth, (2) to understand the impact of changes in the internal conditions of the hearth on wear patterns; and (3) to design a monitoring/controlling system for prolonging campaign. In this paper, the results will be reviewed.

Jan 1, 2006

By William K. Tolley

The U.S. Bureau of Mines (USBM) is investigating hydrometallurgical processing techniques to recycle metals from semiconductors and other advanced materials. Cadmium and tellurium were recovered from mixed CdTe/CdS scrap produced in the manufacture of thin-film photovoltaic devices. Cadmium and tellurium dissolution was achieved using hydrogen peroxide in dilute sulfuric acid. Leaching the scrap in 2.2 N H2SO4 yielded 99% Cd extraction and 98% Te extraction. Sulfur remained in the leach residue primarily in the elemental form. Elemental tellurium was precipitated from the leach liquor by adding Na2S2O5. Cadmium sulfate was recovered by evaporation. A preliminary process evaluation suggests that the process may have economic potential. Alternative recovery schemes are discussed.

Jan 1, 1995