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By Rina Kim

The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of lead salt in the low overpotential region (–0.35 V vs. Ag/AgCl). The similar behavior was observed in the presence of ore containing 0.25% galena. In contrast, the gold oxidation kinetics retarded at –0.35 V (vs. Ag/AgCl) in the presence of silicate and lead-bearing mineral under certain conditions. Likewise, the lead addition was not functional for the high sulfur ore. This was attributed to the oxidation of the sulfides to the elemental sulfur, which subsequently formed a passivating layer on the gold surface. The results were evidently affirmed by the electrochemical tests and X-ray photoelectron spectroscopy (XPS) analysis.

By Mizraim Uriel Flores, Elia Guadalupe Palacios, Sayra Ordoñez, Iván Alejandro Reyes, Ister Mireles, Martín Reyes, Francisco Patiño, Hernán Islas, Víctor Hugo Flores

This paper presents the characterization of a sample of mercury jarosite that was synthesized by slowly adding Hg(NO3)2H2O into a Fe2(SO4)3nH2O solution. X-ray diffraction (XRD) analysis performed on the sample confirmed that the compound presents a crystal phase corresponding to mercury jarosite. Analysis through Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS) determined that the precipitate is composed of mercury, sulfur, iron and oxygen. It is made up of spherical particles with an average size of 38 μm; these particles are made of rhombohedral micro-crystals with sizes ranging between 1 and 2 μm. Chemical characterization was performed through dichromatometry analysis, gravimetry and atomic absorption spectroscopy (AAS), thus obtaining the following composition: 27% Fe3+, 37% SO4 2− 14% Hg2+, 22% OH− + H3O+ + H2O. The following approximate formula of the compound was determined from chemical analysis: [Hg0.39(H3O)0.22]Fe2.71(SO4)2.17(OH)4.79 (H2O)2.09.

Mar 1, 2017

By James P. Bennett, Jinichiro Nakano, Anna Nakano, Hani Abu El Hawa

Carbon feedstocks used in power, chemical and metallurgical industries typically contain numerous minerals or impurities that liquefy during high temperature processing to form slag as a byproduct. Slags have many industrial applications, for example, as construction materials and for element recovery. In addition to other variables, the extent of slag utilization is dependent on its com- position and post treatments. In this work, the in fluence of temperature and phos- phorus additions on phase evolution in coal slag was investigated. Synthetic slag mixtures with varying AlPO4 contents (0–14 wt%) were heated from 1380–1470 ° C in air, then water-quenched to preserve the phases formed. SEM/EDS, XRF and XRD analyses were performed before/after testing to gain insight about slag chemistry and phases present. It was found that coal slag exhibited a large solubility of phosphorous, affecting morphology of mullite formed under the conditions studied. Results obtained and their significance are discussed.

Mar 1, 2017

By B. Zeytuncu, O. Yucel, O. H. Celik, M. H. Morcali

"The Taguchi method was used as the experimental design to determine the optimum conditions of cementation behavior of the ruthenium chloride solution. Cementation was carried out using metallic zinc powder. The experimental conditions were studied in the range of 25-45°C for reaction temperature (A), 30--60 min for reaction time (B), 0.5-1.5 for pH of solution (C), and 30--50 mg for zinc powder (D). Experimental parameters and their levels were determined in the light of preliminary tests. Orthogonal array (OA) L9(34) consisting of four parameters each with three levels, was chosen. The optimal conditions found for ruthenium, such as a reaction temperature, reaction time, pH of the solution and mass of zinc, are respectively: 45°C, 45 min, 1.5 and 50 mg. Under these conditions, the ruthenium cementation efficiency obtained by theoretically and experimentally was in good agreement, which were 99.8% and 99.7% respectively."

Jan 1, 2013

By Ying Qin, Shujing Zhu

The characterization of adsorption of natural and composite bentonite in lead aqueous solution has been studied. The results showed that adsorption of both natural and composite bentonites strongly depended on the pH values of the solution. At lower pH values, the mechanisms that govern the adsorption of bentonites were dissolution of crystal structure and competition between the metal ions and the H+. To composite bentonite, the lead ion removal capacity was close to 250 mg/g. At higher pH values, formation of lead hydroxyl species might lead to either participation to the adsorption or precipitation onto the bentonites. Hence, a rapid increase in the equilibrium removal capacity of lead was obtained when pH > 7.0. An increase in the initial lead ion concentration led to the increase in the equilibrium adsorption capacity increased to a certain degree; and then, a plateau was obtained at higher concentrations. As a result, the adsorption performance of composite bentonite was better than the natural bentonite in both physical and chemical changes. The data fitted well with both Langmuir and Freundlich isotherms.

Mar 1, 2017

By M. X. Huang, Y. Z. Li

The titanium diboride (TiB2)-reinforced steel composite, designed for automotive applications, exhibits a combination of high isotropic Young’s modulus and low density as compared to existing advanced high strength steels (AHSS). The steel-based composite is produced by in situ precipitation of TiB2 particles during eutectic solidification followed by hot rolling, and its microstructure displays a homogeneous distribution of both large primary TiB2 and small eutectic TiB2 particles in the ferrite matrix. Instead of interfacial debonding, particle cracking is the primary mode of damage, revealing very high interfacial strength. To investigate the intrinsic interfacial strength, a hybrid method combining both nanoindentation and finite element analysis (FEA) was used. A micron-sized sample containing a single crystal TiB2 attached to the ferrite matrix was fabricated by focused iron beam (FIB), and was compressed using nanoindentation with a flat indentation tip. By combining the compression and FEA results, the interfacial strength was therefore determined.

Mar 1, 2017

By R. C. Nascimento

It was investigated the effect of the addition of bentonite on the physical propertiesof pellets produced from fines of manganese ores. Cold-bonded pellets were produced. Pellets bearing up to 1 wt% of bentonite were submitted to strength compression resistance tests, fatigue of pellets to impact and maximum height of fall tests. A correlation of resistance of the pellets and time for curing were stablished. The produced pellets match the conditions for raw materials used in electric smelting hrnaces to produce manganese based ferro-alloys.

Jan 1, 1995

By Alexandre Bonan

The paper reports on the results of a kinetic study on the oxidation reaction of aqueous free cyanide ions with H202, in the presence of Cu(2+) catalyst. The variables and respective ranges studied were the following: (CN) ° = 10 -100 mg/l pH = 10 -11 (H202/CN) mol ratio = 1 -3 (Cu/CN) mol ratio = 0 -0.25 The results lead to the development of a semi-empirical model whish incorporates both the useful oxidation reaction and the parallel alkaline decomposition of H202.

Jan 1, 1992

By Bin Xu, Qian Li, Xin Min, Xiaoliang Liu, Yongbin Yang, Tao Jiang, Yan Zhang

The ringing characteristics of acid and alkaline iron ore pellets powder in kiln were studied by the thermodynamic calculation using software FactSage7.0, roasting experiments using briquetting method and analysis of SEM-EDS. The thermodynamic calculation demonstrated that liquid phase could be generated from alkaline pellets powder at a lower temperature and the amount of formed liquid phase was much more than that from acid pellets powder at the same temperature. Roasting experiments indicated that the compression strength of alkaline pellets powder briquettes were also higher than that of acid pellets powder briquettes. Additionally, the analysis of SEM-EDS suggested that the alkaline pellets powder briquette presented more liquid phase and a more compact structure comparing with the acid pellets powder briquette, which was consistent with the results of thermodynamic calculation and roasting experiments. Hence, in comparison with acid pellets powder, alkaline pellets powder is much easier to ring in the kiln.

Mar 1, 2017

By Lu-ming Zhao, Li Zhao, Yu Wang

Mould flux is a vital functional material which is based on silicate including flux and framework material. The effects of magnetic field intensity and frequency on viscosity of mould flux were tested by rotational viscosity tester and a measurement device for electromagnetic characteristics of mould flux viscosity under high temperature conditions. The results show that: with the magnetic field intensity rising (0 –30 mT), the viscosity of mould flux increases by 1.3–1.8 P. With the frequency rising (6–12 Hz), the viscosity of mould flux is increased by 1.2–1.4 P. When the binary basicity is 1.08, the viscous flow activation energy increases with the increase of the magnetic field intensity and frequency. It can be the main reason for the increase of mould flux viscosity that the electromagnetic forces disrupt the ordered structure of mould flux and make the ion migration rate increase.

Mar 1, 2018

By Staff

The uninitiated, first-time visitor to the Copper Cliff Smelter of The International Nickel Company frequently finds it strange that the world's largest nickel producing works is located at a site seemingly named in honour of another metal. Industry-wise persons who know The International Nickel Company through its nickel producing, fabricating and sales organizations can be just as surprised to learn that Inco's annual copper production from the Sudbury area mines nearly equals that of nickel. But when the history of the mines and smelters of the Sudbury district is reviewed it is impossible to separate the stories of copper and nickel. In fact, going even further back in time (I), it was due to the similarity in appearance of the nickel bearing mineral niccolite (NiAs) to that of copper ore that led nickel to be tagged with the rather uncomplimentary name of kupfer-nickel or Old Nick's Copper - The Devil's Copper. This was in approximately 1650 and it would take another hundred years, until 1751, before Axel Cronstedt of Sweden obtained nickel in its pure form and permitted it to take its own place in the family of metals. One hundred more years passed before mining came to northern Ontario and approximately one hundred thirty before the beginnings of development of the Sudbury Basin.

Jan 1, 1976

By Musa Karakus

Ceramic build-ups are synthetic mineral deposits formed in critical locations in or near the throats of inductor units in channel induction furnaces, the preferred melting and holding furnaces used in iron foundries. The build-ups are undesirable because they slow down melt circulation, increase power consumption and cost. and decrease the quality of the metal. This study involved the determination of the mineralogy of build-up samples and the quantitative measurement of phase abundance in those build-ups by cathodoluminescence microscopy. These undesirable deposits usually are hard and dense and contain variable amounts of entrained metallic iron. The non-metallic phases dominantly consist of oxides and silicates of several refractory elements, AI, Mg. Ca, Si, and Fe. Minor amounts of the sulfides of Ca. Mg, Fe and REE elements, especially Ce and La. and the oxides and silicates of Ce and La elements are locally present in the build-ups. The build-up samples were found to be ideally suited for study by cathodoluminescence, which has provided an easy means for rapid re-cognition of the phases present in the build-ups. The phase compositions were determined by electron microprobe analysis. The phases identified and their characteristic cathodoluminescence shown in the ceramic build-up samples were: spinel (bright green, blue-green, and red). forsterite (red and purple), periclase (dark reddish-brown, blue. and orange), corundum (red, blue, orange, and white), anorthite (yellow, yellow-green, blue, and blue-purple), hibonite or calcium hexaluminate (dark green), mullite (dull red-brown), gehlenite (deep blue), silica(dark brown, pink, purple, red. and blue), monticellite (light violet blue and light pale yellow-orange), silicon carbide (orange), oldhamite (bright yellow and orange). Ce-La silicate phases (purple), and glass (orange, dull red, and purple). Non-luminescent phases were: hercynite, Fe-oxides, Ce-La-oxides, Fe-sulfides, and metallic iron.

Jan 1, 1989

By A. González

Arsenic is one of the main contaminants present in Chilean copper concentrates and its abatement represents a challenge for the process metallurgy, particularly under the strong environmental requirements in the global community. The possibility to form ferric arsenate directly from a gas phase by means of a heterogeneous reaction between an arsenic gas bearing and iron oxide was studied at laboratory scale. A thermodynamical analysis for the system Fe-As-O-S has been initially made, in order to obtain the stability conditions for the ferric arsenate or other FeAsyO2 type compounds. Experiments were made using an hematite sample suspended in a thermogravimetric device. AS4O6 gas generated from solid AS2O3 that was passed through the iron oxide sample and its instantaneous weight change was recorded directly. A kinetic study for the AS4O6 volatilization was made to control the gas composition. A chemical control between 300 and 600°C with an apparent activation energy of around 14 Kcal/mol As2O3 was determined. The samples after the reactions were chemically and XRD analysed. Arsenates detected corresponds to complex compounds. Results shows a dependence on temperature and oxygen content in the gas phase. The kinetics for iron arsenates formation is slow, reaching an arsenic capture of 6% after 80 minutes of reaction when an oxygen content of 50% is fed continuously at 800°C and 3,56% As in the gas. Experiences made at the same temperature but under higher oxygen content in a closed reactor, allowed arsenic capture close to 60%. For higher temperatures the capture is considerably lower.

Jan 1, 2003

By J. Rastas

The recovery of lead, silver and gold from existing and potential zinc process residues using a sulfidization-flotation method was investigated on a laboratory scale. The following residues were tested: neutral leach residue, high acid leach residue, and hematite residues. The sulfidization of lead and silver is carried out at low pH by the addition of a stoichiometric amount of sulfide at a controlled rate. To increase the particle size of the sulfides, seeding with synthetic lead and silver sulfides -is employed. The flotation is carried out at pH 2-4 using low pH-collectors such as dithiophosphates and dithiophosphinates. Special attention must be paid to the role of oxygen in the conditioning stage. The effect of different parameters on both the sulfidization and the flotation has been evaluated. Recoveries of 85-90, 90-95 and about 80 % were obtained for lead, silver and gold, respectively. Typically, concentrates containing 50-60 % lead, 3-5 kg/t silver and 10-15 git gold were produced.

Jan 1, 1990

By Min-Min Lin, Bing Xie, Hong-Yi Li, Yang Yang

After precipitation of ammonium vanadates from vanadium-containing leaching liquor, vanadium (V(V)) and chromium (Cr(VI)) exist in the waste water in form of vanadate ions and chromate ions. In order to efficiently extract and recover V(V) and Cr(VI) from waste water, an environment-friendly method based on anion exchange was investigated in batch tests using macroporous weak base resin Dex-V. The adsorption conditions optimizes in detail, including the effect of pH, initial metal concentration, resin volume, contact time and temperature. The ion-exchange adsorption process for both V(V) and Cr(VI) showed maximum capacity at pH 3.0 for an initial concentration of 100 mg L−1, and reached equilibrium after about 40 min of contact at 298 K. The maximum adsorption ratio under the optimum conditions for V(V) and Cr(VI) was 98.98 and 99.87%, respectively. Result shows that the established method is a promising alternative for simultaneous extraction of vanadium and chromium.

Mar 1, 2018

By Kejun Liu

Platinum and palladium are usually dissolved together and followed by separation. In this study, the selective leaching of platinum and palladium from a secondary resource, such as dental waste, by using chloride solution (hypochlorite and chlorate) has been developed. Results indicate that about 100% of palladium could be initially extracted by the combination of 0.3 mol/L sodium hypochlorite (NaClO) and 0.068 mol/L sodium chloride (NaCl) at pH 1.2 and 298K in 1.5 hours, or the combination of 0.005 mol/L sodium chlorate (NaClO3) and 6 mol/L hydrochloric acid (HCl) at 298K in 0.5 hour. About 100% of platinum could be extracted from the residue by the combination of 0.47 mol/L sodium chlorate (NaClO3) and 12 mol/L hydrochloric acid (HCl) at 298K in 2 hours.

Jan 1, 2003

By R. H. Eric, A. Chaendera

Gas jet was blown through bottom nozzles of a 1/5th scale CLU model in the presence and absence of slag. Kerosene and water were used to simulate the slag and metal phases respectively. Mixing time increased with increasing bath height and with a decrease in the gas flow rate. It was related to bath weight, bath height and gas flow rate. Slag increased mixing time by about 16% and the mass transfer values by about 32%. Mass transfer rates were higher near the bath surface and in the gas-liquid plume region. They increased with increasing gas flow rate and with a decrease in bath height. A relationship showing the dependence of derived mass transfer coef ficient on the gas injection rate was established. Turbulence characteristics inside the bath liquid were established to vary with location, vessel geometry and gas injection rate.

Mar 1, 2017

Achieving continued economic growth with social equity within the natural limits of the Earth's 'eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By De-qing Zhu, Feng Zhang, Jian Pan

Sintering performance of a series of sinter blends with high ratio of limonite was investigated. The metallurgical performance and mineralogy of product sinter were also examined. The results show that good sintering performance could be obtained when the ratio of limonite was below 43% in the blends of iron ore fines, while good microstructure and metallurgical properties were achieved under optimum sintering conditions. In contrast, sintering performance will rapidly deteriorate when the ratio of limonite is elevated up to 63% in the blends.

Mar 1, 2017

By S. N. Monteiro, C. M. F. Vieira, A. P. N. M. de Sa, J. P. D. Vitorino

"This work has as its objective to characterize an ash waste and to evaluate its incorporation into a clay to produce bricks and roofing tiles. The waste is a type of fly-ash resulting from the incineration of a selected part of urban garbage, which is basically constituted of organic matter and plastics. The waste was submitted to mineralogical and chemical characterization. Compositions were prepared with incorporation of the waste in amounts of up to 20wt.% into athe clay. Rectangular specimens were prepared by extrusion and fired in a laboratory furnace at 900°C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The results showed that the waste is predominantly composed of quartz and calcium compounds. The incorporation of the ash was deleterious to the evaluated properties of the clay. It is suggested that the incorporation should be made in amounts below 5wt. % to avoid deleterious effect in the mechanical strength and water absorption of the clayey ceramic.IntroductionThe world attention has turned to a subject of great concern today, the production and disposal of large amounts of industrial wastes as well as wastes of various sources. When deposed in an unsuitable place, these wastes can cause considerable harm to human health and to the environment. Our planet suffers with air pollution, groundwater and soil contamination as well as silting of rivers and lakes with the growing amounts of our society wastes.The recycling of waste materials is of great interest to the industries, mainly due to the environmental agencies legislation. One of the practices for correct disposal of these wastes being investigated is to incorporate into red ceramics, such as bricks and roofing tiles. The natural variability of the characteristics of the clays associated with the relatively simple processing techniques and also the low performance required for the products allow the presence of relatively high levels of impurities in clayey ceramics."

Jan 1, 2011