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By B. K. Mishra, Avijit Biswal, B. C. Tripathy, Abhijeet Singh, K. Sanjay, T. Subbaiah

We studied theeffect of anode substrates such as pure lead (Pb), lead antimony (Pb-Sb), and lead-silver (Pb-Ag) on the structural and electrochemical properties of electrolytic manganese dioxide (EMD). X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and chemical analyses were used to determine the structural and chemical characteristics of the EMD samples. The charge-discharge profile was studied in 9 M KOH using a galvanostatic charge-discharge unit. In all the substrates the current efficiencies were more than 99% except with Pb-Sb where it was 90%. Results revealed the nature of the substrate strongly affected the morphology of the deposited material which in turn affected the electrochemical properties of the EMD samples. XRD analyses revealed that the nature of the anode did not affect the crystal structure of the deposited EMD and all the samples were predominantly ?-MnO2, which is electrochemically active for energy storage applications. The EMD deposited on lead substrate showed superior discharge capacity of 245 mAhg-1 when compared with other substrates.

Jan 1, 2014

By Flávia Paulucci Cianga Silvas, Otávio da Fonseca Martins Gomes, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Jorge Alberto Soares Tenorio, Guilherme Apostólico Bortolini, Stoyan Gaydardzhiev

"Printed circuit boards (PCB) are particularly problematic to recycle because of the heterogeneous mix of organic materials, metals, and glass fiber. PCBs are found in almost every electroelectronic equipment and their recycling process involves a pre-treatment to separate the products which contain targeted metals. In this work, a physical processing involving sequential shredding and hanuner milling were used to obtain a comminuted sample from scrap printers PCBs. The thus prepared sample was analyzed for particle size distribution and by optical microscopy as well was subjected to pyrolysis, leachabilty and chemical composition determination by XRF. The metals concentration was determined by ICP and AAS. The PCBs have been also analyzed by SEM-EDS (micro-analysis and X-ray mapping). The results show that the studied PCBs are lead free, multilayer with 4 copper layers, have 45% of metals and the copper is present in significantly higher concentration than the rest of the metals.IntroductionThe global generation of e-waste (electrical and electronic equipment waste - WEEEs) grows at a rate of about 40 millions of tons per year [ l].Among this e-waste there are PCBs that are present in almost all electronic equipment. Their composition is heterogeneous and varies according to several factors, including: kind of EEE, when and where it was produced, fabrication technology [2], etc. In printers, the PCBs represent about 6.6- 8 wt.% [3].The PCBs treatment may include physical, pyrometallurgical, hydrometallurgical, ectrometallurgical and more recently bio-hydrometallurgical process. Normally there is a combination between these processes [2, 4, 5, 6, 7, 8, 9, 10].The diversity between the different PCBs composition complicates the recycling process since the composition of metal and others materials can vary according to the models. So characterization is an indispensable step before any processing of PCB to begin. Owing to the above said, the main goal of this work has been set to characterize representative samples of PCBs from printers through physical, chemical and microstructural analyses."

Jan 1, 2014

By R. S. C. Smart

Surface chemical factors, including the balance of hydrophobic (e.g. collectors) and hydrophilic (e.g. oxidation products, precipitates) species, are major control determinants in flotation rates of specific minerals and therefore grade and recovery. There are a number of challenges involved with the surface analysis of different mineral phases from process streams in a flotation facility. The first is to collect samples that are representative of the process and retain their surface chemistry prior to introduction into the instrument. The second challenge in studying the surface chemistry of specific minerals is to find reliable methods of mineral phase recognition. In surface analysis of mineral particles, confident mineral selection can be difficult with many multi-metal minerals and with precipitated, adsorbed, reacted and contaminant species in the outermost molecular layers. The third challenge is to provide a statistical surface analysis of multiple grains of the same mineral. Methods to achieve these aims are described. Principal component analysis (PCA) of ToF-SIMS data provides improvement in phase recognition, particle selection and associated variations in surface species. Specific examples from both lab and plant operations, demonstrate that this technique can be utilized to differentiate surface chemical factors promoting (hydrophobic species) or inhibiting (hydrophilic species) flotation. A study of copper ion transfer (inadvertent activation) from chalcopyrite to pyrite and sphalerite clearly identified a statistical difference in copper intensities between the sphalerite and pyrite phases corresponding to their flotation response. The PCA analysis applied to concentrate and tails samples collected from the Inco Matte Concentrator demonstrated extensive CuOH and NiOH transfer between chalcocite and heazlewoodite minerals. The statistical analysis has been able to identify mechanisms controlling recovery and selectivity. High intensity conditioning (HIC) tests in which sphalerite was separated from a complex sulfide ore gave a 5% increase in the overall Zn recovery. The PCA/ToF-SIMS statistical analysis revealed the discriminating depressant action of adherent aluminosilicate (gangue) fine particles and adsorbed ions on the surface of sphalerite grains. HIC conditioning resulted in the removal of these gangue fines improving surface collector attachment efficiency.

Jan 1, 2014

By A. Otsuki

This paper describes the evaluation method of dispersion and coagulation of silica nano-particles by means of interactive force apparatus. The apparatus measures the size of fine particles in aqueous solution or organic solvent of high concentration and/or low optical transparency. Other conventional apparatus for size measurements (such as, apparatus utilizing dynamic light scattering) are difficult to measure the size of particles in such conditions accurately, due to multi-scattering of light in the sample solution or solvent. The apparatus measures the interactive force between two surfaces, i.e. the gold-coated glass hemisphere and the brass flat plate, (which is fixed at the bottom of the sample cell). The apparatus has three parts, i.e. main part (which consists of electric balance, hemisphere and flat plate), control part (i.e. personal computer, piezo-stage controller and voltage supplier), and detecting part (i.e. multi-meter and oscilloscope). During the measurement, electric field is applied between the hemisphere and flat plate, and thus dielectric particles are arranged toward the direction of electric field in the area between two plates. When the two plates are close to each other, two different forces (i.e. repulsive force and attractive force) will alternately act on particles due to the structure change of the particles. The repulsive force occurs when the structure of particles is stretched by compressive force; whereas the attractive force occurs when the aggregate structure is broken. The cycle of the repulsive and attractive forces is a primary size of particle or size of aggregate, which depends on the degree of agglomeration. The measured size of particles, which is varied depending on their degree of dispersion and coagulation, determined the characteristics of the silica particles. In this research work, the effect of size and concentration of particles in aqueous solution on the degree of dispersion and coagulation of the silica particles were investigated. Spherical silica particles were selected for this investigation due to their variety of size. This apparatus can be used to evaluate the degree of dispersion and coagulation of other nano-particles in various solvents in many process industries.

Jan 1, 2014

By D. Auerswald, M. Kotze, V. Yahorava, T. Udayar

Uranium can be recovered from lower grade uranium ores (<800 mg/kg U3O8), leach residues, and waste dumps cost-effectively via resin-in-pulp (RIP). Using this technology, no solid/liquid separation or washing of the leach residues are required. Furthermore, the uranium recovery can be higher than with conventional methods. RIP technologies have, however, been perceived negatively due to concerns around potential resin fouling and losses. This paper highlights the advancements made in RIP and discusses a number of potential applications where the technology could deliver economic and consequential environmental benefits by reducing the uranium levels in the waste.

Jan 1, 2014

By S. Q. Zhu

A newly developed coal flotation collector ZFC and its flotation characteristics for five different coals were introduced in this paper. ZFC is an emulsion composed of 27% diesel oil, 70% water and 3% surfactants. The main surfactant is synthesized with oil which is environmental favorable and reproducible. Compared flotation experiments show that, at the same dosage, ZFC give 2%~5% recovery promotion than typical collector with only a slightly ash content increment, but saving 70% diesel oil. Zeta-potential and Wetting heat measurement indicate that the surfactant helps the interactions between oil and coal particles, the industrial application tests in several coal preparation plants demonstrate that ZFC is suitable both in technical and economical aspects.

Jan 1, 2014

By S. Owada

A national project of ?Establishing ?Green-Hydrogen (G-H)? Society in Honjo-Waseda Area? is now being developed by Waseda University together with four other universities and ten companies. The project involves three tasks of technological development of, (1)?G-H? production, (2)?G-H? refining, transportation and storage, and (3)?G-H? utilization. This paper focuses the first task of ?G-H? production from aluminium dross. We developed the physical treatment process by combining selective grinding with vibrating rod mill and electrostatic separation, in order to produce two kinds of materials, one is metal aluminium concentrate to recover it and the other is raw material to produce ?G-H? and aluminium hydroxide which can be generated by the treatment with sodium hydroxide aqueous solution. Here, we described the concentration mechanism of metal aluminium in the selective grinding and electrostatic separation and proposed a separation flowchart for optimizing the ?G-H? system in Honjo-Waseda area.

Jan 1, 2014

By N. Tsoni

The separation and recovery of fine and ultra-fine particles during the processing of mineral commodities by conventional separation methods is difficult and inefficient. This is due to the problems posed by the very small size of the mineral particles. The fine and ultra-fine mineral particles are either generated during size reduction processes or are necessitated by liberation size. This problem is expected to deteriorate, as deposits of even lower grade are processed. The inefficiency of the conventional separation methods with regards to the processing of very fine particles leads to the loss of considerable quantities of mineral commodities to the tailings. Novel methods and techniques as well combinations of known methods have been tested over the years. Among them, selective aggregation, along or in combination with flotation, has been given much attention. This study deals with the application of hydrophobic agglomeration as a separation method for very fine particles. The selected mineral system is magnesite/quartz, due to its sensitivity to physi-cochemical separation methods. The aim was the selective agglomeration of magnesite using sodium oleate. Tests on single minerals revealed that separation seems feasible and efficient. The parameters examined were: pH, quantity of sodium oleate, conditioning time, and, finally, settling time. Tests carried out on artificial mixtures of the two minerals, under various proportions, confirmed the results obtained from single mineral tests but they were slightly inferior. Finally, hydrophobic ag-glomeration tests were carried out on single and artificial mixtures of minerals using sodium oleate and petroleum as reagents. The results show that the addition of petroleum improves the results. In conclusion, hydrophobic agglomeration can be applied successfully even for fine particles of difficult-to-be-separated systems such as magnesite and quartz.

Jan 1, 2014

By Christopher Robben, Alexander Mosser

"X-ray transmission (XRT) sorting has been introduced into the minerals industry in 2006 and has found various applications in diamonds, industrial minerals and metal ore processing since. The technology offers planar projections of the atomic density of single particles similar to the principle known from airport scanners, but being capable of treating up to 150tph per metre working width. In 2010, a pilot operation using a belt-type sensor-based sorter went into production at the Mittersill mine to treat the fraction 16-28mm. After an optimisation phase, the results were superseding expectations and therefore in 2012 a bigger production plant was set up. Two XRT-based sorters are parallel in operation since. One is treating the fine fraction 16-30mm while the other one is treating the coarser fraction 30-60mm after the secondary crushing stage. The XRT sorters are operated with the objective to reject barren waste before it enters the mill and flotation plant. 105,000tpa of waste material are rejected per year and can be sold as aggregate for road construction. This means that about 22% of the run-of-mine ore are rejected at an early stage with a waste reject grade lower than 0.03wt%WO3. The installation has not only led to lower specific operating costs but also led to reduced tailings disposal in an environmentally sensitive area. This allows the mine to reduce its headgrade which allows for a longer mine life. Alternatively it is possible to produce more tungsten concentrate, which is delivered to the smelter. This article will introduce the technological principle of XRT-based sorting and will discuss the flow-sheet of the Mittersill mine. Experiences that have led to the current plant design are described as well as the impact it has on the operation."

Jan 1, 2014

By J. Roth

The increasing demand of the filler industry regarding fineness and better delaminated products led to the development of a series of different grinding machines, which differentiate basically by the grinding mechanism as well as the kind of classification. Spiral jetmills grind, as it is well known preferably by delamination, therefore a spiral jetmill with integrated dynamic classifier has been developed. Especially the enhancement of the functional properties of the used industrial mineral fillers is a factor of highly increasing importance. These properties are very often bound to the platy shape of the minerals expressed by the aspect ratio. The developed Spiral Jetmill shows sufficient ability for such delamination and therefore increases in aspect ratio. In a series of comparative tests the suitability and advantages of this system regarding achievable fineness down to the submicron range as well as the conservation or even improvement of the aspect ratio of different minerals has been studied. As an emphasis on the results application tests with certain materials in the plastics field have been conducted. Due to the fact that in this range the required specific energy for achieving the necessary fineness increases exponentially another target is to optimize the grinding efficiency. A special feed control system provides on one hand a sufficient load inside the mill to obtain maximum utilization of the applied energy and on the other hand to prevent the mill from overfilling and coming with this a poor classification. The integrated classifier is a combination of a high speed motor with directly attached classifier wheels. This unit on one hand grants the necessary high circumferential speed of up to 190 m/s for providing an exact top cut of the ultrafine products and on the other hand gives the required operational reliability for continuous operation. Hard grindable impurities, which enrich inside the mill chamber, can be rejected from the process leading to an even cleaner product. Comparative tests on a talc product with certain free quartz impurities showed a significant improvement of the final product with respectively low loss on rejected material. This effect again had a beneficiary impact on the suitability of the final product when used in plastics application.

Jan 1, 2014

By G. V. Sedelnikova

Biohydrometallurgical studies were performed on the sulfide gold-arsenic concentrate obtained in treatment of refractory ore from a deposit located in northern Russia. Gold is disseminated in sulfides-arsenopyrite, pyrite and antimonite (their content is 10.0%, 30.4% and 0.7%, respectively). Gold extraction is only 11.8% by cyanidation. Results are given for test bacterial oxidation of the concentrate in continuous mode at temp. = 28~32°C using mesophilic bacteria and at temp. = 32~38°C using the association including moderate thermophilic bacteria. The paper shows that the use of moderate thermophilic bacteria allows to speed up sulfide biooxidation and reduce its time to 96 hours compared to leaching at temp. = 28~32°C for 110~120 hours. The optimal range of pH = 1.5~2.0 of biooxidation process was determined where bacterial solutions are produced with the molar ratio Fe:As > 3 necessary for precipitation of hard-to-solve, environmentally safe arsenical precipitates. Electron microscopy showed that sulfide biooxidation results in liberation of disseminated gold with nanoparticle-level sizes. High sorptive activity of carbonaceous matter and other compounds of bacterial residues cause low gold extraction into cyanide solution ? 28.7%. 10% resin load makes it possible to extract 88.1% Au. Aeration of pulp in calcareous medium enhances extraction to 95.7% and decreases cyanide consumption from 17kg/t to 8 kg/t.

Jan 1, 2014

By T. M. Bhatti

The main purpose of present study was to characterize the dissolution of uranium from low-grade black shale with indigenous isolated strain of Acidithiobacillus ferrooxidans (BSAF-01). The nature of shale is quartzite-schistose and contains uranium content of 0.005% U3O8 (50 ppm U3O8). Uranium is present in the tetravalent oxidation state (U4+) in the shale matrix. The main minerals identified are graphite, quartz, pyrite, mica minerals (phlogopite, biotite, sericite, and chlorite), microcline, K-feldspar and kerogen (hydrocarbon-compounds). Bacterial oxidation of pyrite was an acid-generating system and produced sulfuric acid and ferric sulfate during this biological phenomenon. A series of bioleaching experiments were conducted in shake flasks for leaching of uranium from black shale. The leaching experiments were performed at 50% pulp density using indigenous Fe- and S-oxidizing bacterium (Acidithiobacillus ferrooxidans). Bioleaching data revealed that about 90% ~ 95% U3O8 was leached out from black shale ore. Uranium dissolution from shale depends on pH (pH 1.5~1.9), redox potential (=500 mev) and the concentration of Fe2+ and Fe3+ ions in the leaching environment. The oxidative leaching of U4+ involves a redox reaction with Fe3+ as an oxidant and bacterial re-oxidation of Fe2+ in acidic leaching environment. Uranium leaching efficiency was attributed to the sulfuric acid and ferric sulfate production during bacterial oxidation of pyrite.

Jan 1, 2014

The additive property of dispersion variances was found experimentally by D.G. Krige using data from the gold deposits of the Witwatersrand. In this property, called ?Krige?s relationship?, the dispersion of a small unit, v, within the deposit is equal to the sum of the dispersion of v within a bigger unit, V, and the dispersion of these units, V, within the deposit, D. It is known that the variance of the grades decreases as the support increases, the so-called volume-variance relationship. To analyse volume-variance and Krige?s relationship, the methodology herein proposed combines blending piles and geostatistical simulation to simulate the in situ and the pile grade variability. Variability reduction in large piles is based on the volume-variance relationship, i.e. the larger the support, the smaller the variability (assuming perfect mix). Based on a pre-defined mining sequence to select the blocks that will form each pile for each simulated block model, the statistical fluctuation of the grades derived from real piles can be simulated. Using this methodology, one can evaluate within a certain time period the expected grade variability for various pile sizes, and also calculate the Krige?s relationship between the small blocks and the piles of different sizes. A real case study using a large Brazilian iron ore deposit illustrates the methodology and demonstrates the validity of the results.

Jan 1, 2014

By Z. G. Song, C. Y. Sun, X. R. Zhang, Y. Yu

In skarn type scheelite deposit, there are calcium minerals with floatability similar to scheelite, such as calcite, fluorite, etc., which are difficult to separate. Heating cleaning method developed by Petrov has been widely applied in processing rough concentrate of scheelite for nearly half a century, but there exists a general lack of full understanding of the interaction between floatation reagent and mineral particles surfaces. The mechanism on separation of scheelite and calcium minerals in heating cleaning process was investigated by mineral flotation experiments, XPS analysis, as well as solution chemistry and crystal chemistry calculations. The results showed that the sequence of minerals floatability using sodium oleate as collector and a large amount of sodium silicate as modifier in heating flotation test was scheelite > calcite > fluorite, which was the same as solution chemistry calculations based on Gibbs free energy vs. pH and also the same as Ca-X intensity order by crystal chemistry analysis. There are two sides about the mechanism of heating cleaning method: one is that the adsorbed collector on calcium minerals surface is desorbed more easily than scheelite, and the other is selective dissolution of calcium ions from the mineral surface because of Ca-X intensity difference in heating and stirring process.

Jan 1, 2014

By R. Perlman

This paper describes the various new computer-aided techniques being used by economists in the construction of economic models. It discusses the relevance of these techniques to mining industries. In particular, it describes their role in making it possible to obtain better estimates of future price and demand developments on the markets on which metals are sold, and how these estimates can be used to improve forward planning by mining companies.

Jan 1, 2014

By M. Steyn

The coordination compound tetrakis(1,3-diphenyl-1,3-propanediona to)zirconium(IV), [Zr(DBM)4], (DBM = dibenzoyl methane/1,3- diphenyl-1,3-propanedionol) was synthesized and characterized by single-crystal X-ray diffraction. [Zr(DBM)4] crystallizes in the monoclinic space group P21/c (a = 24.769(4) Å, b = 10.216(5) Å, c = 19.314(4) Å, and = 101.541(5)°). The coordination geometry around the zirconium atom, formed by the eight O-donating atoms of the four -diketonates, is found to be a near-perfect square antiprism. Crystal packing is stabilized by C?H... interactions throughout the crystal lattice. This structure is a noteworthy example of the application of ambient condition synthesis of zirconium compounds in N,N&apos;-dimethylformamide (DMF) as reaction and crystallization solvent, highlighting the possibilities of aerobic condition metal purification through chelation.

Jan 1, 2014

By O. Alonso-Gonzalez, F. Nava-Alonso, A. Uribe-Salas, R. Pérez-Garibay, C. Jimenez-Velasco

A current problem in gold production is the presence of copper minerals which dissolve during conventional cyanidation practice. The dissolved copper causes several problems in the different stages of the process. This issue is the base for copper elimination/recovery methods such as the Sulphidization, Acidification, Recycling, and Thickening (SART) process, which is currently used in gold production plants around the world. Even though the process is well established, new challenges appear as the composition of the solution varies from ore to ore, in some circumstances affecting the performance of the SART process. This work presents a thermodynamic study and experimental tests performed to understand the role of the initial copper concentration and sulfur addition, on the efficiency of the copper removal. For a constant cyanide concentration, an increase in the initial copper concentration causes a decrease in copper removal; high sulfur/copper molar ratios favor copper removal. We demonstrated that the cuprous sulfide formed from solutions with high ionic strength, presents better sedimentation rates than solutions with less ionic strength. For solutions with low sedimentation rates, the use of some pretreatment is necessary to facilitate the sedimentation such as addition of flocculants, particle recirculation and the used ultrasonic pretreatment.

Jan 1, 2014

By G. B. Harris

It has long been appreciated that chloride chemistry has a number of advantages over the more traditional sulphate route for both extracting and separating metals. Modern materials of construction, coupled with the development of a more cost-effective and efficient hydrochloric acid regeneration technology mean that chloride-based processes are now more competitive and attractive. Such processing routes are able to recover more of the contained metal values in a feed, including iron in a benign and/or marketable form, and particularly the so-called rare and rare-earth elements which are increasing in demand in our electronic age. These factors, therefore, add appreciably both to the overall economics of a project, but also offer a much more sustainable approach to our dwindling natural resources. Additionally, chloride-based flowsheets can be much more environmentally-friendly, offering practical alternatives to two of the biggest headaches faced by the industry, namely cyanide usage and the generation of red muds. This paper presents a brief theoretical background, focusing on the latest developments of ferrous iron oxidation and the low-temperature, selective hydrochloric acid regeneration process, which is the key unit operation for any chloride flowsheet, and discusses in general the advantages of the chloride approach. Several recently-developed flowsheets, which have been tested at the miniplant level, are presented for gold, base metals, titaniferous magnetites and lead-silver ores wherein the advantages of considering a chloride approach are highlighted.

Jan 1, 2014

By Ö. Genç

In this paper, full-scale mill data collected from three different circuit configurations in cement plants demonstrated the size reduction performance of dry ball mills in relation with the ball size classification achieved by the classifying liners used in the grinding compartments. Findings indicated that, breakage rates at the last 2 ~ 4 meters of the mill are not sufficient to give reasonable size reduction ratios for the production of fines. Application of only damming rings without classifying liners resulted in inverse ball size classification which lead to reduction in size reduction performance thus specific breakage rates.

Jan 1, 2014

By K. S. McClure, S. B. Chitralekha, R. B. Gopaluni, Chmylek. T., S. L. Shah

This is a tutorial paper on industrially successful approaches for nonlinear process monitoring. Online process monitoring is essential to continuous operation of plants at high efficiency. The problem of process monitoring is one where an impending but undesirable process condition has to be identified and used to alert process engineers. This problem has traditionally been solved by practicing engineers using statistical techniques that detect a change in the underlying correlation structure of process variables. For linear correlation structures, algorithms such as principal components analysis, independent component analysis and partial least squares have been proposed. However, many industrial processes exhibit nonlinear correlation structure between the process variables. In this tutorial we describe various nonlinear monitoring techniques and elaborate on two recently developed methods, namely Support Vector Machine and Local Linear Embedding. The two methods are evaluated by application on two experimental case studies, a SAG mill and a polymer extruder.

Jan 1, 2014