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By ZHANG Ting

In view of the high consumption and contamination of traditional vanadium extraction technology, a new process of leaching the converter vanadium slag without roasting with titanium dioxide waste was proposed. Extraction mechanism of P204 in the leaching solution had been researched and single factor experiments show that after a prereduction of Fe, and under conditions: ambient temperature，leaching solution original pH=2.5, phase ratio (A/O)=1:3, shaking time 8min, the extraction rate of V is more than 98.62% meanwhile the separation rate between V and Fe is up to 135.3 in the 20%P204-10%TBP-Sulfonated kerosene extraction system.

Jan 1, 2015

By C. Lupi

"The energy consumption of copper production by electrowinning, generally represents more than 1/4 of the total energy requirement in hydrometallurgical traditional process (roasting, leaching, purification and electrowinning). The considerable saving can be achieved just in this step that requires about 2.2 kWhlkg of the produced copper. To save energy the cell voltage, or more appropriately its anodic component, can be reduced: that is because the anodic voltage represents the main component of cell voltage and so it is largely responsible for the excessive energy consumption in copper sulphate electrowinning.In this work some ways are studied to lower the anodic voltage. First the cobalt ions were added to the sulphate solution in order to study the catalytic effect on oxygen discharge. Then lead alloys anodes (Pb-Ag, Pb-Sb-Ag and Pb-Ca) were used to promote a better oxygen evolution as a result of a different anodic surface. Their behaviour was compared with the PbSb traditional ones. Finally, as already pointed out by several authors for zinc electrowinning, ethylene glycol was employed as anodic depolariser in order to verify its effectiveness in the case of copper electrowinning. By combining all the above-mentioned ways, energy saving ranging from 20% to 27% is achieved.All the tests were carried out on a laboratory pilot-plant for long time to simulate the industrial conditions. The obtained copper deposits were observed by SEM to highlight their morphology."

Jan 1, 1997

By Devon A. Hannan

Thermodynamic modeling calculations were undertaken for the recovery of mercury from HgTe using a vacuum retort reactor. However, discrepancies were noted in the available thermodynamic data which introduced uncertainty in the model results. Consequently, a series of transpiration experiments were first undertaken on the thermal decomposition of HgTe into an inert carrier gas stream according to the following reaction: HgTe(s) Hg(g) + Te(s) From the measured weight loss of the HgTe samples, the Gibhs free energy change for the above volatilization reaction was determined as a function of temperature. The experimentally determined Gibbs free energy values were found to be approximately 30% larger (more posi-tive) than the values available in databases such as HSC Chemistry. By conducting a second-law analysis on the experimental data, the heat of formation of HgTe at 298.15 K and the en-tropyat 298.15 K were determined, which then formed the basis for a new database for the modeling calculations. The results of this study showed that HgTe was more stable at elevated temperatures than was generally indicated in the literature. The new database is given in a for-mat for direct insertion in HSC Chemistry. Using the new database, modeling calculations were conducted to examine the effects of the re-tort pressure and the molar ratio of purge gas to HgTe on the volatilization of mercury from HgTe. A diagram is presented that shows the minimum temperature for 100% volatilization of mercury from HgTe as a function of retort pressure for different molar ratios of purge gas (N2) to HgTe. For example, it was found that the minimum temperature for 100% volatilization could be decreased by 175 K, at a retort pressure of 0.05 bar, if the molar ratio ofN2 to HgTe is increased from 1.0: 1 to 100.0: I.

Jan 1, 2003

By John R. Goode

The fist part of this paper comprises a general discussion on refractory gold ores and their mineralogy. Processing methods now in use are reviewed and test procedures for the important methods are discussed. Factors determining the selection of a process are outlined. The paper includes a survey of production plants using pressure oxidation, roasting and biological oxidation to process refractory ore. The status of processes under development is briefly reviewed.

Jan 1, 1993

By Dan Mancuso

This case study is an example of how Encyle/Texas, Inc. (a subsidiary of ASARCO) responded to various socio-economic forces by converting an idle zinc hydrometallurgical refinery into a metals recycling facility. The facility accepts metal-laden process waste streams and produces various "synthetic ores" which are sold back to industry. Acceptance and reactions by industrial, political, economical and regulatory interests towards the project are also discussed.

Jan 1, 1992

By Jewel A. G. Gomes

Lead has long been an USEPA priority pollutant and an important environmental and health concern because of its toxicity at ppb levels. In light of health and exposure data for lead, the EPA has set standards for Maximum Contaminant Level (MCL) and a MCL Goal (MCLG) as 15 ppb and 0 ppb, respectively. An accurate and rapid measurement of lead in the field remains a technical challenge. In this work, a relatively new method of deploying a nanoband electrode system using anodic stripping voltammetry has been optimized by changing deposition potential, electrolyte, and plating time used for the measurement of Pb(II) in water samples. Green rust has been proven to be an efficient intermediate matrix for removal of lead contaminants. We also report here the removal efficiency of lead using green rust produced by electrocoagulation, both directly and indirectly. Lead containing floc was also characterized through XRD, SEM, and EDAX techniques.

Jan 1, 2008

By D. Lui, B. G. Thomas, B. Ho

"Results from mathematical models and plant experiments are combined to quantify the effect of transverse depressions and oscillation marks on heat transfer in the continuous casting mold. A heat transfer model has been developed to calculate transient heat conduction within the solidifying steel, coupled with the steady-state heat conduction with the continuous casting mold wall. The model features a detailed treatment of the interfacial gap between the shell and mold, including mass and momentum balances on the solid and liquid powder layers. The model predicts the solidified shell thickness down the mold, temperature in the mold and shell, thickness of the resolidified and liquid powder layers, heat flux distribution down the mold, mold water temperature rise, ideal taper of the mold walls, and other related phenomena. The important effect of non-uniform distribution of superheat is incorporated using the results from previous 3-D turbulent fluid flow calculations within the liquid cavity. Results from plant experiments confirm that transverse surface depressions and oscillation marks form at the meniscus and move down the mold. Measurements of mold thermocouple temperatures and breakout shell thickness were used to calibrate the models. The results indicate that the surface depressions and oscillation marks are filled with mold flux, but still have a significant effect on decreasing heat transfer. The predicted mold temperature fluctuations are consistent with measurements. If the depressions become filled with air, their effect is greatly increased. These results should be useful in the difficult task of interpreting transient mold thermocouple signals for on-line quality monitoring.IntroductionMany different types of intermittent surface defects on steel slabs arise during initial solidification in the mold of the. continuous casting machine. These defects include deep oscillation marks, surface depressions, and cracks. They may lead to quality problems, such as slivers, in the final rolled product. In severe cases, breakouts may occur, where liquid steel bursts through a thin section of the shell and drains over the casting machine below the mold."

Jan 1, 1997

By N. A. Barcza

DC plasma-arc technology using a hollow graphite electrode (cathode) has been successfully implemented in the primary metallurgical industry in South Africa up to the 30 MW scale. Mintek has applied its expertise base, established over the past fifteen years, to testing the treatment of metallurgical wastes such as carbon- and stainless-steel plant dusts, lead- and zinc-containing slags, and residues from the base-metal industry. Favourable results have been achieved, and disposable products were produced. The evaluation of numerous wastes indicates that recovery of zinc as metal gives the best economic return from these sources. Direct recovery via a splash condenser or electrolytic zinc extraction from fume are the two preferred alternatives under review. In both instances dehalogenation is an important issue, but can be achieved by suitable treatment processes. The Enviroplas technology provides a flexible, commercially viable approach to the treatment of a wide variety of wastes. Mintek, together with its associate Pyromet CC, are installing a plasma- arc pilot-plant facility with both an ISP lead-splash condenser of about 5 t/d condensed zinc capacity and a combustion chamber to burn zinc vapour to zinc oxide. This will demonstrate the suitability of the Enviroplas technology for treating specific metallurgical wastes, so that customized industrial plants can be engineered based on large-scale testwork.

Jan 1, 1994

By Derek J. Fray

Electric arc furnace dusts, especially those containing zinc ferrite, are notoriously difficult to process to give valuable products and non-toxic residues. The ideal process would remove and recover the toxic non-ferrous metals as pure metals, of commercial value, and non-toxic residue which can be used as a raw material in the steel industry. From an examination of the thermodynamics of the oxides and chlorides of the various elements in the dust, it is apparent that the chlorides of the toxic non-ferrous elements are more stable than the oxides while the reverse applies to the ferrous elements. This offers the opportunity for a complete separation of the zinc, lead and cadmium from the iron oxide. Results are presented for the chlorination of electric arc furnace dusts under oxidising conditions and the subsequent treatment of the chlorides to recover the pure metals and chlorine which can be recycled back to the reactor.

Jan 1, 1994

By T. T. Chen

Raw anode slimes consisting primarily of PbSO4, AgCuSe, Cu3Se2, Cu2-x Se, Cu2O, CuSO4.5H2O, Sn arsenate and Sb-Bi-As oxide are batch-leached with electrolyte-O2 to dissolve Cu. During this process, Cu2O and CuSO4.5H2O are solubilized and the Cu in the selenides is leached with the formation of Ag2Se and Se. A small amount of Cu remains in the Ag2Se, Sn arsenate and Sb-Bi-As oxide. The decopperized slimes are repulped in Na2CO3 solution to convert most of the PbSO4 to NaPb2(CO3)2(OH). The Sn arsenate and Sb-Bi-As oxide partly react, but the Ag2Se is not significantly affected by the Na2CO3 solution. The NaPb2(CO3)2(OH) intermediate phase is dissolved in acetic acid to leave a final product consisting of Ag2Se, Se, Sn arsenate and Sb-Bi-As oxide, together with small amounts of PbSO4, NaPb2(CO3)2(OH) and various gangue constituents.

Jan 1, 1993

By lchiro Aoi, Hideo Nakae, Makoto Yoshida, Makoto Ishino

"The influence 6f gravity on the microstructure of unidirectionally solidified Cu-Pb monotectic, Ag-Si and Fe-C eutectic alloys is studied. In order to examine the influence of gravity in a lg environment, both the upward (opposite to direction of gravity) and downward (direction of gravity) unidirectional solidifications are carried out. The results are as follows: (1) For the upward solidified Ag-Si eutectic alloy, the eutectic Si continuously grows. On the other hand, in the downward solidified Ag-Si alloy, the Si grows discontinuously and disperses into the ex-Ag matrix. (2) No morphological difference in the eutectic growth is observed between the upward and downward solidified Fe-C eutectic alloys. (3) In the case of the upward solidified Cu-Pb monotectic alloy, a banded structure, which consists of Pb-rich layers and Cu-rich layers, is observed. However, such a banded structure -is not observed in the downward specimen. (4) The banded structure is not found in the upward solidified Cu-Pb-0.05 mass % Al and Cu-Pb-0.1 mass % Al alloys. In the Cu-Pb-0.05 mass% Al alloy, a fibrous -L 2 phase grows continuously parallel to the growth direction at low growth rate. Only 500 mass ppm addition of aluminum induces the morphological change of the monotectic L2 phase.IntroductionThe influence of gravity on the solidification of eutectic and monotectic alloys has been investigated in microgravity environments [l-9]. The purpose of these studies was to obtain a homogeneous microstructure of eutectic or monotectic alloys, most of which alloys tend to solidify with macro-segregation under gravity. However, in most of the previous experiments, e.g., in free fall systems, in aircraft or in space laboratories, the growth rate was too high to realize a planar solid/liquid interface. This would be due to the limited time for solidification. Thus, it was difficult to examine the influence of gravity on the planar coupled growth of the eutectic or monotectic alloy. In this study, both the downward U.D.S. (unidirectional solidification by gravity) and upward U.D.S. (opposite direction to gravity) are carried out in order to examine the influence of gravity on the coupled growth in a lg environment [l0, 11]. In the case of the downward U.D.S. using the current Bridgman method, the molten alloy must be confined between the crucible and the solid."

Jan 1, 2000

By J. L. Jambor

Sulfide-rich tailings accumulated in a 4l-hectare impoundment at the Waite Amulet minesite near Noranda, Quebec, have undergone partial oxidation and destruction of the principal sulfides (pyrite and pyrrhotite) in the vadose zone. Mineralogical studies and whole-rock chemical analyses of 18 samples from 3 boreholes along a cross-section of the tailings pile indicate that the principal chemical manifestations of the alteration are a pronounced depletion in sulfide-sulfur, and an enrichment in total Fe as Fe203' Other elements such as Al, Mn, Mg, Ca, Na, and K in the solids show erratic or inconsistent variations, but a trend to Si enrichment in the oxidation zone is clear. The trend is interpreted to be a relative enrichment whereby the proportion of the stable silicate minerals has increased as a consequence of the consumption of pyrite and pyrrhotite in the oxide zone.

Jan 1, 1989

By Zenjiro Asaki, Teruo Tanabe

"To clarify the formation of light rare earth (R =Ce, Pr, Nd or Sm) -Fe compounds in the reduction-diffusion (RD) process, two kinds of experiments were carried out: (a) RD experiment in which briquettes composed of R oxide powder, Fe (particles or wire) and CaH2 were reacted, and (b) immersion experiment, where an Fe plate was immersed into R-Fe melt having the composition of Fe-side liquidus line in Fe crucible. The compound formation was examined by using XRD, SEM and EPMA. The formation rates of RzFe17 measured by the RD experiment were compared with those obtained by the immersion experiment. The growth rates of compounds obtained in the RD experiment for Pr-Fe and Nd-Fe systems were much lower than those obtained in the immersion experiment. This result was explained by the difference of the reduction rates of R oxides by Ca. The parabolic rate constants for the formation of RzFe17 were separated in two groups of (a) Pr-Fe and Nd-Fe systems and (b) Ce-Fe and Sm-Fe systems. This was discussed in connection with the difference of their crystal structures and the driving force of diffusion. The parabolic rate constants for the formation of compounds in Ce-Fe and Sm-Fe systems decreased in the order of RFez, RFe3 and RzFe17.IntroductionTo understand reaction behaviors in the production of rare earth (R) -iron intermetallic compounds, which have excellent magnetic properties, is very important from engineering point of view. And the reduction-diffusion (RD) process<O has recently attracted attention as one of the promising processes to economically produce R-related materials. A few fundamental studies on the compounds formation in the RD process have previously been reported. Qi, Hino and Yazawa(2) observed the formation of R(Nd, Sm)-Fe and R-Co compounds in the process from various view points. Song and Ogawa(3) measured the growth rates of Nd-Fe and Sm-Fe compounds by using Nd or Sm vapor supplied from Nd-Ca or Sm-Ca melts. The authors have also carried out fundamental studies (4)-(8) to clarify the rate and mechanism in the production of R-Fe intermetallic compounds."

Jan 1, 1998

By Wantae Kim, Jaechun Lee, Tatsuya Oki, Sungbaek Cho, Sangbae Kim

"Effect of attrition scrubbing on the recovery of platinum group metals(PGMs) from automotive catalytic converter was discussed. The attrition scrubbing as comminution and separation process was effective for the recovery of the catalyst layer, ?-alumina, from ceramic supporting matrix, cordierite, by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles less than 45µm by attrition scrubbing. The production of fine fraction less than 45µm increased as the residence time for attrition scrubbing increased. The fine fraction obtained at the residence time of 40min contained 19.25% CeO2, 1.93% ZrO2 and 418.8ppp PGMs. The recovery of ?-alumina in the fine fraction increased as the residence time increased. Simultaneously, the recoveries of CeO2, ZrO2 and PGMs increased and reached up to 82.9% CeO2, 78.7% ZrO2 and 78.9% PGMs at the attrition scrubbing time of 40min. The production of the fine fraction and recovery of ?- alumina increased when the solid concentration and initial feed size increased.IntroductionThe automobile catalytic converters contain appreciable amount of PGMs. Currently several million tons of used catalytic converters are disposed annually worldwide, each containing about 0.5-1g of platinum and 1-2g of all PGMs1). The recovery technologies of PGMs from spent catalytic converters have been thoroughly reviewed by numerous researchers since last decades. Two types of methods, wet and dry processes, have been commercially operated. In the wet process, the PGMs on the spent catalytic converters were dissolved mostly in the form of chlorocomplex, MCl6 2-, by contacting with aqueous solutions. Subsequently the resulting solutions are treated to concentrate and the precious metal ions are reduced by introducing metals such as Al, Fe and Zn in the concentrated system2). In the dry process, the spent catalytic converters are melted, in some case with CaO, at an elevated temperature to produce a low viscous slag. The PGMs in the melt are separated by allowing them to adsorb on Fe or Cu having high specific gravity7). Although highly pure precious metals could be obtainable, the recovery technologies of PGMs currently operated seem not to be cost-effective since PGMs embedded in these types of catalytic converters are present in very small quantities."

Jan 1, 2008

By N. Kanari

Reactivity of MgO towards C12+air, C12+N2 and C12+CO gas mixtures was studied up to 1000 °C. Carbochlorination of MgO occurs at temperatures lower than that of its oxychlorination. Effects of gas flow rate, temperature and partial pressure of the carbochlorinating gas mixture on the reaction rate were investigated. The apparent activation energy of MgO carbochlorination is 49 kJ1 mol between 425°C and 600°C. At 550 °C, the apparent reaction orders with respect to C12+CO, C12 and CO, are 2.37, 1.47 and 0.89, respectively. At this temperature, the maximum reaction rate was obtained using a C12+CO gas mixture having a Cl2lCO molar ratio equal to about 0.6.

Jan 1, 1998

By R. W. McCallum, B. Jensen, K. W. Dennis

"There are substantial challenges in the exploration of magnetic materials in the R-TM-X system (R =rare earth, TM= transition metal, X =stabilizing element) where Xis an element which has high vapor pressure, high reactivity, toxicity, or a refractory nature. This research focuses on discovering new phases with high anisotropy and high magnetization through closed diffusion couples inside high purity Fe crucibles. Either vapor-solid reactions or powder metallurgy techniques are then employed to isolate a stoichiometric sample based on a potentially magnetic phase found in the diffusion couple. For this research, X = F, Ca, Sr, Se, Zn, Bi or Cd, TM= Fe, and R = Nd. New ternary phases have been discovered with WDS and EDS, and magnetic transition temperatures have been measured with a SQUID magnetometer and VSM.IntroductionSince the discovery of the RCo5 compounds in the 1960s, rare earth- transition metal (R-TM) magnets have been the main focus of permanent magnetic research over the last five decades. Iron-based magnetic materials were studied next in attempts to avoid the unstable price of cobalt as well as the high price of Sm, the top performer in the RCos and RzC011 series. This hunt eventually led to the discovery of Nd2Fe14B with a theoretical BHmax of 64 MGOe, nearly double that of the previous samarium based magnets. The next few decades were devoted to enhancing the magnetic properties ofNd2Fe14B by the improvement of processing techniques and the additions of alloying elements. The only complete elemental substitution discovered in this system was R1Fe14C, which did not improve magnetic properties. It is probably safe to say that most ternary R-TM-X systems, where Xis any element that may stabilize a ternary phase, have been investigated if they may be prepared by conventional processes such as arc or induction melting. The present study offers a systematic approach to developing a novel diffusion couple technique in which the volatile, reactive or toxic alloying elements are laser welded inside a high purity Fe crucible. This experimental setup will prevent the oxidation of the rare earth element, as well as contain the volatile X element. As the goal of the research was to find new rare earth permanent magnets, only phases which contained greater than 60 wt% Fe were investigated. 247"

Jan 1, 2012

By O. Barbosa F.

The thermochemistry of the systems SCN-H2O, Au-SCN-H2O and Ag-SCN-H2O is discussed. Potential-pH diagrams at 25°C are drawn for each system considering several sets of concentrations of the species involved. The information provided by the potential-pH diagrams is.complemented by distribution curves for each series of gold and silver complexes with thiocyanate. The analysis includes comparisons between the thiocyanate systems and the analogous cyanide systems, pointing out analogies and differences between the leaching of gold and silver with thiocyanate and with cyanide. The possibility of using soluble oxidizing agents such as ferric ions, hydrogen peroxide and Caro&apos;s acid is evaluated. The thermodynamic data used in the calculations and the chemical reactions represented in the Pourbaix diagrams are all reported in three Appendices. The overall results indicate the thermodynamic conditions for gold and silver leaching by thiocyanate.

Jan 1, 1989

By Guan-zhou Qiu, Shui-shi Liu, Yu-feng Guo, Tao Jiang

"The preparation of high-quality synthetic ruitle from electric furnace titanium slag was systematically investigated by activation roasting followed by acid leaching process. The results showed that impurities such as Ca and Mg in titanium slag can be effectively removed and TiO2 grade of the product was markedly improved by the process. High-quality synthetic rutile containing 88.54% TiO2, 0.42% (CaO+MgO) was obtained under the conditions that roasted with 7.5%(wt) H3PO4 at 1000 oC for 2h, followed by two-stage leaching in boiling dilute sulfuric acid for 2h. Mechanism studies showed that anosovite solid solution and silicate minerals were reacted with phosphoric acid in the roasting process. As a result, titanium components in titanium slag turned into rutile (TiO2) and impurities were transformed into acid-soluble phosphate and quartz.IntroductionWith the gradual depletion of natural rutile and the rapid development of titanium industry in China, the natural rutile reserves cannot satisfy the requirement for production of titanium pigment and titanium sponge. Ilmenite is, therefore, becoming main raw material for titanium industry. However, because of its low TiO2 grade, it generally requires preconcentration to titanium-rich material such as titanium slag or synthetic rutile [1-3].Ilmenite resources are extremely rich in Pan-xi area of China, which account for 90.54% of total ilmenite reserves in China [4]. The titanium slag produced by electric smelting of ilmenite concentrate has high contents of Ca and Mg, and is not suitable as a raw material for chloride process and titanium sponge production. Therefore, upgrading titanium slag to prepare raw material suitable for chloride process and titanium sponge production has important significance for the development of China's titanium industry."

Jan 1, 2011

By Thomas P. Battle

Ilmenite (iron titanate) is the source of over 90% of all the titanium produced in the world today. At some point during production of titanium dioxide or titanium metal the iron impurity must be removed. Too often it becomes a waste instead of a product. DuPont and MINPRO have developed a solid-state process which separates the iron and titanium components of ilmenite into different high-purity powders, which can be separated using conventional mineral processing techniques. The main reactor in this process is a unique high-temperature ball mill, where the iron segregates from the ilmenite lattice with the assistance of catalytic quantities of He\. The results of lab, pilot plant, theoretical, and scale-up studies are presented and discussed.

Jan 1, 1996

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the &apos;separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995