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By U. Meyer, A. Alonso, P. Banios

The sampling of cathodes has changed with the introduction of the ISA-process in copper refineries. A Jernkontoret joint working group of refineries and rod plants from both primary and recycled copper plants has been investigating whether the actual sampling of cathodes is representative for this type of cathodes. As a first stage, samples were sent to the members of the working group with the objective to find an easy basis for a comparison of the results of the next stages. All samples show the same tendency for nearly all elements. In some cases, there may exist differences in calibration and for some elements the detection limits are too high, especially when Optical Spectrometry is used. In the second stage, discs were compared with melted samples to answer the question whether the punching of discs is sufficient for the quality control of the cathode. The analyses of the discs represent fairly well the cathode quality. There are differences between cathodes from different crops. Three punches are sufficient to determine the cathode quality. Finally, samples from various lots of cathodes were compared with samples from the rod produced from these cathodes. The impurity content of the rod corresponds to the impurity content of the cathode.

Jan 1, 2000

By Norihiro Murayama

Syntheses of zeolitic materials were carried out from coal fly ash by alkali hydrothermal treatment as part of the reuse and recycle technologies of coal ash, For the obtained zeolites, the cation exchange capacity and acid resistance, which are very important in the practical use of cation exchanger in aqueous solution, are investigated during this stufY, The cation exchange amounts of the NaP, CaP and K-CHA zeolites are measured for various cations such as K+, Na +, NH4+ Ca2+, Mg2+, Pb2+, Cd2+ and so on. The change in crystallization degree are researched as a function of pH. The simultaneous removal ability of NH4+ and PO43- in solution is examined for an example of the water purification with CaP zeolite. From these results, the characteristic and its mechanism of cation exchange are clarified for the various zeolitic materials obtained from coal fly ash.

Jan 1, 2003

By Li Qihou

Mono-disperse ZnS and CdS nano-particles were prepared by the homogenous precipitation method and the effects of SO42-,NO3- and Cl-ions on crystalline of particles were investigated experimentally. The results showed that these anions had no influence on the crystalline of ZnS, but different crystalline CdS ultrafine particles were produced in different anion systems, where the blend-type CdS was obtained from natrate or sulphate solution, and wurtzite-type CdS from chloride solution. It was ascribed to the coordination of Cl- and Cd2+ that altered the supersaturation of precipitate ions in the solution, the existing growth units and their connecting patterns, thereby producing wurtzite-type CdS with a more stable structure.

Jan 1, 2006

By Denise Cristina de O. Nascimento

Natural lignocellulosic fibers are increasingly being used as polymeric matrix composite reinforcement owing to economical and environmental advantages as renewable and biodegradable materials. Among these, the piassava fiber extracted from a palm tree native of South America stands as one of the most rigid with a potential to be used as composite reinforcement. Therefore, the present work investigates the notch toughness behavior, by Izod impact tests, of epoxy composites reinforced with up to 40 % in volume of continuous and aligned piassava fibers. It was found that the incorporation of piassava fibers results in significant increase in the impact energy of the composite. Scanning electron microscopy analysis showed that the nature of the piassava fiber interface with the epoxy matrix is the major responsible for the superior toughness of the composite.

Jan 1, 2009

By A. P. Pavia

Investigation on profitable ways to recover significant quantities of silver remaining dissolved in highly concentrated chloride solutions frequently pass through the development of solvent extraction (SX) routes. In this work, the general pathways involving Ag(I) extraction by dibutylthiourea (DBT) or tetraethylthiuram disulfide (disulfiram, DSF), from concentrated acidic chloride solutions, are investigated. With this purpose, the dependence of Ag(I) distribution coefficient on ligand and chloride concentrations has been analysed. Furthermore, in order to check whether there is some protonation at any site of DBT or DSF after contact with adequate chloride phases, lH NMR has also been used. The collected spectroscopic data suggest that anionic Ag(I) extraction reactions are not likely to occur. Based on the overall results achieved, proposals for the most probable Ag(I) extraction reactions are made.

Jan 1, 2001

By J. A. S. Tenorio, A. B. Botelho Junior, I. A. Anes, D. C. R. Espinosa, M. A. Caralho

Recovery of metals from reserves with low grade and from waste with high presence of contamination is a challenge to be overcome. Metals like nickel, cobalt and copper could be recovery from nickel laterite leach waste by many different processes. Among recovery processes that could be applied are ion exchange, solvent extraction and precipitation. The aim of this work was recover copper from liquor of nickel laterite by precipitation using chemical reduction. Copper concentration in liquor was 146 mg L −1 and reducing agent used was sodium dithionite 1 mol L −1. Influence of stirring speed was studied between 0–200 rpm. Results indicated a selective precipitation of copper on solution with others metals at 240 mV. The analyzes were conducted in SEM, energy-dispersive X-ray spectroscopy and XRD, that indicated presence of copper and sulfur.

Mar 1, 2018

By Kimio Itagaki, Torn Matsumoto, Makoto Ohtsuka, Kentarou Harada

"The structure and hydrogen-absorption properties of LaNis thin films were investigated in the present study. LaNis thin films were prepared by a sputtering method with a radio-frequency power, Ws, of 50 -400 Wat substrate temperature, Ts, of323 -573 K. Nickel content of the films decreased with increasing Ws, however, there was no dependence on Ts. At low Ws and low Ts, amorphous films were deposited. In other conditions, the films were polycrystalline. The films prepared at high Ws and low Ts, or at low Ws and high Ts, exhibited only a (h k · 0) peak in the X-ray diffraction profiles. This indicates that the c-axis of crystalline films was oriented parallel to the substrate plane. At high Ws and high Ts, the films with columnar structure were obtained. Hydrogen-absorption capacity of the thin films increased with increasing Ws. The pressure plateau did not appear on the pressure-composition isotherms. The films deposited at high Ts represented a higher equilibrium pressure.IntroductionThin films of hydrogen storage alloys can be applied for an electrode of rechargeable battery or fuel cell, a filter for H1 purification and various kind of sensor. Some studies on the preparation of the thin films of LaNi5 intermetallic compound, which is a typical hydrogen storage material, have been done hitherto. Adachi et al. , 2) and Sakaguchi et al. 3) prepared amorphous and crystalline LaNi5 thin films using flash evaporation of alloy powders and measured the pressure-composition isotherm for the prepared film utilizing a quartz crystal mass monitoring (QC:MM) method. It was found that the prepared amorphous film absorbed hydrogen without disintegrating into the powders and the hydrogen-absorption capacity of the films increased with the degree of crystallinity. Sakai et al. 4) reported that the maximum hydrogen storage capacities of amorphous and crystalline LaNi5 thin films, fabricated by a RF sputtering method using combination targets, were about 40 mA h g-1 (LaNisHo.7) and 160 mA h g-1 (LaNi5H2.6), respectively. Uchida et al. 5, 6) prepared LaNi5 thin films using flash evaporation of alloy powders and measured volumetrically the pressure-composition isotherm for the prepared film. It was reported that the hydrogen-absorption capacity of the films changed by the annealing treatment."

Jan 1, 1998

By S. H. Castro

The El Teniente molybdenite plant (Chile), with a nominal capacity of 3,200 tpd of bulk Cu-Mo concentrate, produced approximately 3,385 metric tonnes of Mo during 1998 by using the phosphate Nokes process (LR-744 reagent). This is the only Chilean moly plant which traditionally has depressed copper and iron sulfides with LR 744 reagent, which is a hydrolysis product of P2S5 and NaOH. El Teniente's ore Mo grade is 0.02%Mo and is concentrated to 0.45%-0.50% Mo in bulk Cu-Mo flotation. Subsequently, molybdenite is floated by selective flotation to depress Cu and Fe sulfides, such as chalcopyrite, bornite, digenite and pyrite, to produce typically a 49%-50%Mo molybdenite concentrate. An optimisation program during the last two years was undertaken to improve molybdenite recoveries. Current molybdenite plant technology at El Teniente and use of phosphate Nokes in the process process is reported. Use of phosphate Nokes reagent has increased average Mo recovery from 70.5% in 1977 to a mean 74.7% for the first 4 months of 1999. The global Mo recovery, including bulk flotation, incresed from 42.3% in 1997 to 46.8% in 1998, with a projection of 55.5% for 1999. Mo production per year has increased from 3,181 tons in 1997 to 3,385 tons in 1998 and a projected 4,000 tons for 1999.

Jan 1, 1999

By C. B. Piazzarollo

Red Ceramic materials are widely used in Civil Construction in Tropical Countries. However, these materials have high porosity and low mechanical strength. Thus, in order to improve these properties, recycle mineral wastes was incorporated into clay from Campos - RJ, ornamental rock waste, from the gneisses cutting of Cachoeiro - ES, 150 km from Campos. After the addition of up 10% of waste in clay mass, ceramic pieces were produced and subjected to the tests of porosity (P) and flexural strength (FS). The test material contains 53.3% clay and 67% waste slit. The X-ray diffraction identified the presence of kaolinite, quartz and feldspar for the clay and, for the waste, quartz and orthoclase. The results of FS and P showed that the residue influenced, positively, the ceramic piece, with strength gains especially from 920º up to 960°C.

Jan 1, 2015

By Pedro Henrique L. M. Lopes, Édio Pereira Lima Jr., Fernanda Santos da Luz, Fábio de Oliveira Braga, Sergio Neves Monteiro

Several works have been dedicated to study the ballistic response of multilayered armor systems (MAS), including those using natural fiber composites as second layer. These composites disclosed good ballistic performance, having economic and environmental advantages. In the present work, the objective was to investigate the effect of areal densities of each MAS layer, in the overall performance of a MAS with an alumina ceramic front, a curaua fabric reinforced composite filling, and an aluminum alloy backing the target. Ballistic “backface signature” tests were conducted, varying the areal densities of the MAS layers according to a Box-Behnken design. The results showed a similar influence of the ceramic and aluminum layers in the MAS “backface signatures”, although deformation and failure mechanisms were significantly different. The composite also showed significant participation in the overall MAS performance. Since the composite is cheaper and lighter, a balance minimizing the other layers would be advantageous.

Mar 1, 2018

By Yavuz Ali Topkaya, Aydin Rusen

"In this study, zinc and lead recovery from zinc plant leach residue obtained from Çinkur using hydrometallurgical methods have been investigated by laboratory scale experiments. Considering more than one million tons leach residue (LR) rich in Zn (12.43%) and Pb (15.51%) in the stockyard and environmentally hazardous, it is essentially necessary to process Çinkur LR. Zinc and lead have been recovered in two main stages. As a first step, Çinkur LR was releached by using hot sulphuric acid for zinc recovery. About 72 % Zn was recovered by using 150 g/l H2SO4 at 95 oC in 2 hours with a pulp density of 200 g/l. Secondly, for lead recovery brine (NaCl) leaching tests were performed on the secondary Çinkur LR obtained after acid leaching process. In brine leaching while lead recoveries up to 95 % could be attained at a low pulp density, the maximum recovery obtained was 84.9 % at a high pulp density (200 g/l) with 300 g/l NaCl concentration in 10 minutes at 95 oC. Introduction Zinc and lead have been known and used by humans since ancient times and also they are important nonferrous metals [1]. Zinc and lead have different properties thus they are used in various application areas, ranging from automobiles to construction, from batteries to textile. Zinc and lead deposits are widely distributed in the Earth’s crust. The principal ore mineral for zinc is zinc sulfide, Sphalerite (ZnS), and lead sulphide, Galena (PbS), is the main source of lead in the world [2].Although zinc is generally produced from sulphidic ores (ZnS) or concentrates by Roast – Leach – Electrowinning (RLE) in the world, in Turkey, zinc production is based on zinc carbonate ores (ZnCO3), and at the Çinkur plant zinc was produced from zinc carbonate from its establishment to 1997 due to high reserves of zinc carbonate in that region. Çinkur is the only plant in Turkey that produces Zn from primary ore containing ZnCO3 by Waelz – Leach - Electrowinning route [3]. However, due to depletion of local high grade ores, oxidized ore concentrates were imported from Iran after 1997, until this plant was shut down. Therefore, there are two different leach residues (LR) which are Turkish LR (TLR) and Iranian LR (ILR) in Çinkur stockpiles. It has been estimated that the total amount of leach residue is more than one million tons of which the major part is Turkish leach residue (TLR)."

Jan 1, 2008

By Peter Forschner

Classical Mixing Theory is based on applying many fundamental correlations to standard baffled dished bottomed vertical cylindrical vessels with high degrees of symmetry. Horizontal autoclaves operating at elevated temperatures and pressures have been used for more than two decades. All compartments and especially the first and last compartments are asymmetrical. To date no comparison of the effects of the asymmetric geometry on mixing system design and scale-up has been published. The results of investigating solids suspension, mixing time, momentum transfer from the impeller to feed slurry and feed inlet location in the first autoclave compartment are presented as influences on residence time distribution. CFD modeling was developed and verified with the test apparatus.

Jan 1, 2003

By S. Pirzada, P. R. Taylor

A reactor was designed and constructed to perform experiments on the generation of value added products using a plasma heat source. The engineering drawings were developed to include multiple sample ports for temperature and velocity measurements and view ports were designed to allow the Physics group to make optical measurements. Two methods for feeding solids into the system were developed and installed. Preliminary experiments were performed to characterize the system at various flow rates and power settings. Experiments were performed using zinc metal and oxygen to form zinc oxide. The particles that were generated were characterized chemically using atomic absorption and x-ray diffraction; and physically using scanning electron microscopy. The particles appear to be of value added size; but there is a tendency for the fine particles to adhere to one another forming agglomerates. Additional experimental work will continue the evaluation of the major parameters.

Jan 1, 1988

By E. M. Timoshenko

Autoclave technology can be effectively used for liberation of complex mineral raw materials to transfer valuable constituents into solution for their subsequent recovery or to refine feed material in order to remove deleterious impurities, e.g. arsenic. The high efficiency of autoclave processes is attributed to the fact that they are suitable for processing of refractory raw materials, have low capital costs, high productivity, ensure integrated utilization of the feed materials, produce innovative saleable products, completely eliminate any air emissions, provide low-waste or waste-less technology, mechanization and automation of production processes. In the immediate future, it might be expected that autoclave processes will find use on commercial scale for production of heavy non-ferrous metals in combination with other processes (hydrometallurgical, upgrading, sorption and solvent extraction, electrolytic, etc.) to ensure: - Integrated processing of refractory ores and concentrates (pyrrhotite, zinc, copper-zinc, lead-zinc, nickel-cobalt, copper, pyrite); - Production of metallic powders of base metals as commercial products (copper, cobalt, nickel, etc.), composites on their bases, final products and saleable salts. Processing technologies incorporating autoclave processes, especially at the stage of liberation (chemical upgrading) of raw materials are characterized generally by high overall recoveries of valuable constituents significantly exceeding recoveries common for conventional pyrometallurgical processes (for some elements by several tens of percent).

Jan 1, 2006

By Seung-Whee Rhee

Characteristics of ceramic support made by spent foundry sand-loess mixtures are investigated by bulk density, porosity, durability, and compressive strength. And the basic properties of SFS and loess are estimated. The effect of drying time after cutting process, elevated temperature time, sintering temperature, and sintering time is also estimated to obtain the optimal condition in the process of manufacture ceramic supports. From the basic properties of SFS and loess, the content of SiO2 in furan sand is much higher than that in loess but the content of Al2O3and Fe2O3 in furan sand is much lower than that in loess. In order to make ceramic supports cylinder shape is the most desirable to sustain the properties of ceramic support. If annulus shape has a enough compressive strength, however, annulus shape may be decided. For the optimal condition to manufacture ceramic supports, drying time after cutting process is decided to 24 hrs and elevated temperature time is decided by 9hrs. And sintering temperature and sintering time are decided to 900 and 9hrs, respectively in order to prevent solidification of sand materials.

Jan 1, 2006

By S. N. Monteiro, N. A. Cerqueira, E. B. Zanelato, J. Alexandre, M. T. Marvila, B. C. Mendes, A. R. G. Azevedo, G. C. Xavier

Mortar is a widely used building material and has its application in buildings in extremely vulnerable environments and susceptible to degradation, such as facades. The objective of this work was to evaluate the loss of mechanical resistance to compression and flexure and the loss of mass of the mortars with effluent sludge from paper industry, when exposed to saline environments. The specimens were done with 0, 5, 10 and 15% of incorporation in lime paste and subjected to saline mist equipment that sprays salt solution in cycles simulating natural degradation conditions using literature data. It can be concluded that mortars with a15%incorporation obtained a significant loss of mass and a decrease in their mechanical resistance, which impairs their use in civil construction and influence in other properties of the material, with a level of incorporation of 10% the results within Brazilian standards.

Mar 1, 2018

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By S. N. Monteiro, E. B. Zanelato, J. Alexandre, M. T. Marvila, A. R. G. Azevedo, G. C. Xavier

The incorporation of industrial waste into ceramic tiles is a major trend in the search for alternative raw materials, and also in the search for environmentally correct disposal of waste. In order to evaluate the effect of the incorporation of residues from the ornamental stone industries, in the properties of ceramic tiles, incorporations of up to 40% by weight of the residue in ceramic mass were studied. It is noteworthy that this residue is constituted basically by limestone and its characterization was performed by grain size analysis, Atterberg boundaries, grain density and chemical analysis by X-ray fluorescence. The specimens were burned at 800 °C and the following properties were evaluated: linear retraction, water absorption and bending rupture stress. The results indicated that the residue of ornamental rocks is a material with potential to be used as a component in the mass of red ceramic tiles.

Mar 1, 2018

By Robert E. Moore

Synthetic spinel is proving to be a highly effective refractory for specific applications, but its cost limits applications. Formation of spinel from a raw material such as diaspore or bauxite could provide a simple and less costly starting material. In the study reported here, finely ground (-325 mesh) diaspore from Missouri and bauxite from Guyana and China are combined with hard burned MgO (-325 mesh) in appropriate proportions to yield spinel and spinel with secondary phases. A classical sintering and dilatometer study was completed, followed by a microstructure study to determine completeness of the reactions and morphologies of the reaction products.

Jan 1, 1993

By David G. Dixon, Maziar Eghbalnia

"Gold and silver nanoparticles (NPs) were deposited on pyrite at ambient temperature from colloidal solutions prepared by reduction of hydrogen tetrachloroaurate or silver nitrate by sodium sulfide or sodium tetrahydridoborate. The nanoparticles were characterized using Ultraviolet-Visible (UV-Vis) spectroscopy and the experimental spectra were fitted using Mie - Gans modeling. The modified pyrite was investigated using Electrochemical Impedance Spectroscopy (EIS). Electrodes were prepared from both natural and modified pyrite samples and were modeled using an equivalent circuit (EC) based on the EIS data. The comparison of the results revealed a decrease in charge transfer resistance for the ferric ferrous redox couple associated with the modified pyrite. From this behavior it is concluded that the electronic transport between the nanoparticles and the electrode surface over distances in nanometer scale is enhanced. Nanoparticles below a certain size act as quantum dots due to electronic confmement. Decreased charged transfer resistance at the nanometer scale may be caused by electron transport through tunneling mechanism via quantum dots.IntroductionIn recent years, considerable attention has been focused on the synthesis and study of Metal nanoparticles due to their potential applications in the fields of physics, chemistry, biology, medicine, material science and their interdisciplinary fields[!]. When material is nano-sized, the physical properties deviate markedly from those of bulk material, however, this effect is highly dependent on the particle size, interparticle distance, and morphology of the nanoparticles [2].An extremely small region of space defmed in a semiconductor material in order of nanometers is called a quantum dot, a term coined by Reed [3]. The three dimensional confinement of quantum dots can change properties of the excitons in comparison to free excitons in a bulk material [4]. Nanoparticles behave electronically as zero-dimensional (restricted in all three dimensions) quantum dots when the de Broglie wavelength of the valence electrons and the particle are in the same size range.As Reed [3] explains electrons confined in a plane have no freedom to move the third dimension. Those confined in a quantum wire are only free to move in one dimension, and those confined in a quantum dot are not free in to move in any dimension. An electron inside a cube of material IO nm on a side is confined to a point."

Jan 1, 2012