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By Hong Nguen Vu, Pavla Ovcarí, Peter Fecko, Barbara Tora

"The goal of the work was verification of bacterial leaching on the samples of black coal. From the results obtained it was clear that the coal is very well leached by Thiobacillus ferrooxidans and this technology can be used for coal desulphurization. A leaching time of one month is required, to remove 65% of total sulphur and 85% of pyritic sulphur.Microscopic evaluation of samples from Jaworzno showed, that it should be classed as a coal with low coalification, probably from black coal hemiphase. Macerals of the liptinite group were well distinguishable; they were of a dark brown colour. Evidence of coal mass oxidation was apparent on the fresh sample; in the test samples (during bacterial leaching) small grains were oxidised."

Jan 1, 2003

By Atsushi Shibayama, Toyohisa Fujita, Luo Lin, Toshio Miyazaki

A novel process is developed in this study for separation of tungsten and vanadium from a leach solution of tungsten alloy scraps. Specifically, a magnesium salt combined ammonium solution is employed to precipitate vanadium and impurities in the purification of the leach solution. This separates vanadium from tungsten by rejecting tungsten in aqueous solution. Finally, tungsten is recovered as the form of ammonium para-tungstate (APT). Vanadium is recovered as the form of ammonium meta-vanadate(AMV).

Jan 1, 2003

By John C. Gathje, Rick Moritz, Wilhelm de Beer, Gary L. Simmons

"Froth flotation has a long history of success for the recovery and concentration of a wide variety of minerals of commercial interest. Both the art and science of flotation have progressed greatly, and as our knowledge has increased so has our ability to improve mineral separations and recoveries.One area of interest in recent years has been the flotation of refractory gold ores to recover the goldbearing sulfides. In many instances, the use of conventional air flotation to concentrate these values has achieved only limited success. However, as a result of intensive research, Newmont Mining has expanded the boundaries of flotation, and it can now be used to successfully treat many gold-bearing sulfide ores as well as platinum and palladium ores. This has been achieved through the use of the patented N2TEC technology, which utilizes nitrogen as an inert gas in the flotation process."

Jan 1, 2003

By Kang N. Zhong, Hui H. Luo, Yunan Phosphate Chemical Co., Yi H. Wei, Yao J. Li, Yu L. Wang

"The three kinds of phosphate ores (igneous, metasedimentary and sedimentary) found in China have great differences in flotation flowsheets and reagents suite because of their crystal structure and mineral composition. The igneous and metasedimentary apatites have good floatability with fatty acid as collector and waterglass, sodium hydroxide or sodium carbonate as conditioners. The sedimentary phosphate is very difficult to beneficiate by direct flotation because of their poor floatabilities and relatively high content of MgO and SiO2, even though the dolomite depressants are used sometimes.The differences in floatability of apatites in China are closely related to their differences in specific surface area. The amount of collector to float apatite increases with the specific surface area. Apatite with lower specific surface area showed good floatability at lower collector concentration. Apatite with a higher specific surface area needed a higher concentration of collector. The content of CO3 2- will affect the specific surface area of apatite by distortion of its crystal structure and consequently affect its floatability.Dolomite can be easily rejected from apatite in a weak acidic medium (pH=5), especially in phosphoric acid medium by reverse flotation. Quartz and siliceous gangue in sedimentary apatite can be removed by direct flotation using fatty acid or by reverse flotation using amine. Amine is not practically applied because sedimentary apatite in China is usually very fine and needs fine grinding, which always results in excessive, very fine, stable and non-flowable foam.Based on the floatability of phosphate ore in China, a two-stage flotation process, direct and reverse flotation (D+R), was developed to beneficiate sedimentary ore. For the Haikou phosphate ore containing 25.11% P2O5, 3.46% MgO and 16.5% SiO2, a concentrate containing 31.84% P2O5, 0.48% MgO and 14.8% SiO2 can be obtained through a continuous D+R test at a recovery of 89%."

Jan 1, 2003

By Matti Kongas, Kari Saloheimo, Antti Remes

"The paper studies the control performance of the flotation process as a function of the measurement accuracy and sampling frequency of an on-stream XRF analyzer, using a simple dynamic model. An additional aim is to assess how the economical result of a mineral flotation process depends on the quality of process control based on the on-line elemental assays.An on-stream XRF analyzer measures the concentrations of slurry lines in a continuous cycle from several process points. The control performance depends on the analytical accuracy and sampling frequency of the concentration measurement. With a long cycle time, the state of the process changes before a new measurement becomes available. With short measurement times the statistical variance of the counted Xray pulses increases, increasing the random error in the analysis. In addition, the measurement accuracy depends on the concentration of the component to be measured from the slurry.To quantify the effect of analysis error and frequency to process control, a simple dynamic process model is created in the Matlab environment. Data from a copper flotation circuit is used as a test case. The process model comprises a first order reaction equation and the grade-recovery -relationship estimated from process data. The control was modeled using the control strategies implemented into a rule based advanced control system. The economical performance of the control was studied by calculating the overall net smelter return at various analyzer parameter combinations."

Jan 1, 2003

By Paolo Bevilacqua, Paolo Antonini, Lorenzo De Lorenzi

"Italy is one of the major producers of ceramics in the world. Ceramic production requires large quantities of K-feldspar, which is commonly sourced from granites, alkali-granites, and “granitic” sands. These rocks contain other minerals, such as quartz, plagioclase and mafic minerals, which are undesirable for ceramic production. Due to the coarse mineral grains that constitute these rocks, a reasonable liberation is achieved at a relatively coarse grind size.This paper reports a study conducted on the separation of K-feldspar from quartz, plagioclase and biotite, from a feed of ground granite. The feasibility of the separation using a dynamic dense medium separation system has been investigated, as an alternative to the traditional flotation technique. The use of a two stages cylindrical vessel (Tri-Flo) was preferred to a conical vessel, due to the improved separation efficiency. Tests were conducted on two samples of crushed granite having size distributions of –3 +1 mm and –1 +0.5 mm.Heavy liquid analysis was performed on the two samples. As the rheological properties of the dense medium interact with the separation efficiency, the stability and viscosity of the dense medium were controlled and kept within an appropriate range; which was achieved with the addition of an artificial contaminant (clay) to the dense medium."

Jan 1, 2003

By F Battaglia-Brunet, D. H. Morin, Foucher S. ’

In the mineral-processing field, bioleaching of metal sulphide concentrates is currently operated in very large mechanically agitated tanks. Such bioreactors have considerable requirements in terms of power consumption for mixing, aeration and heat transfer. The use of slurry bubble column, where the particles are suspended by gas motion as well as by liquid upward flow, could be an alternative to achieve bioleaching in more economical conditions. In order to compare these two techniques, a unit of stirred reactors in cascade and a bubble column were comparatively operated at laboratory scale in the bioleaching of a pyrite concentrate. For both pieces of equipment, experiments were performed not only in batch mode but also in continuous conditions.

Jan 1, 2003

By Victor Avdokhin, lvan Kovlekov

"Studies of the process of concentration of gold-containing sands and technogenic resources show that the main reason of gold losses is misbalance between size of gold particles and degree of roughness of mineral bed. This results in free circulation of small gold particles in pores with following washing off the particles from the bed by turbulent flows.We elaborated design of magnetic sluice, intended for improving efficiency of recovering fine gold by optimizing magnetic field of a magnetic system on the base of forming catching coat from magnetic mineralsThe magnetic sluice includes trough-shaped body from magnetic-conducting material. On the bottom of the trough, magnets are placed, and opposite poles of the magnets are oriented outwards. Thickness of the bottom is determined to be sufficient for locking magnetic lines of force of the magnets on each other. The magnets of rectangular plate shape are placed on the rough bottom, covering the whole surface or with spare areas; the magnets are placed across the trough with alteration of rows with the same pole orientation."

Jan 1, 2003

By Jochen Petersen, Harro von Blottnitz

"The landfill disposal of slags is common practice in the metallurgical industry. Chromium may be a minor constituent in many cases. It is present mostly in the form of chromites, which are considered environmentally benign and hence safe for disposal. Wastewaters from metal finishing operations are most commonly treated by reduction and precipitation of dissolved metals, including chromium, by lime addition, and subsequent landfill disposal of the resulting sludge. The metals contained in such sludges are mostly in the form of hydroxides, and as such considered environmentally stable.Thermodynamically, trivalent chromium, which is the predominant form in these waste materials, can be oxidised to the hexavalent form by atmospheric oxygen. Detailed research work on both slags and sludges has shown that a gradual emergence of hexavalent chromium can indeed be observed. The mechanism is governed by close physical contact between chromium oxide (or hydroxide) phases on the one side and calcium oxide (or hydroxide), which is present as flux in slags and residual lime in sludges, on the other. If oxygen can migrate to the points of contact, gradual formation of calcium chromate ensues.Hexavalent chromium is associated with high environmental toxicity, and hence undesirable in landfilled materials. Moisture migrating through landfill deposits can mobilise the highly soluble chromates and thus potentially transport them into natural waterways. Such gradual release from stainless steel and ferrochromium slag deposits has been demonstrated in a column experiment."

Jan 1, 2003

By B. C. Qi

"In water treatment, flocculation or coagulation with aluminium or ferric salts has been widely used for many years to remove natural organic matter (NOM), including humic acids. However, the adsorption of NOM to aluminium hydroxide flocs during conventional coagulation/flocculation processes is very complex, with the flocculation of aluminium hydroxide particles and the adsorption of NOM molecules on flocs occurring simultaneously. Any effect on the surface characteristics and micro-structures of the humic acids and aluminium hydroxides could affect the adsorption efficiency.It has been widely observed that if a reaction system (liquid-liquid or liquid-solid) is exposed to an ultrasound field, under appropriate conditions, a variety of physical (emulsification, aggregation/flocculation) or chemical (the production of radical and exited species; single electrotransfer) actions may be activated. Though the ultrasound effects have been used in biological and chemical decontamination in many conventional environmental protection practices, the idea to explore the ultrasound effects in the removal of humic acids by preformed aluminium hydroxide flocs is relatively new. In this paper, the effect of an in-situ ultrasonication on removal of the humic acids extracted from the acidification fermentation of lignocellulosic residues, by a preformed aluminium hydroxide, was evaluated; the effect of ultrasonication on the surface complexation of the humic acids with the preformed aluminium hydroxides was investigated."

Jan 1, 2003

By Sami Makni, Ahmed Bouajila

"To remain competitive in an open market, mining companies are more and more requested to optimise their complex and highly multivariate processes. The increasing amount of process data, brought about by intensive use of instrumentation and the progress in computer data acquisition, enhances the need for more and more powerful and robust tools for the analysis and modelling of the process data. Now, with the emergence of multivariate data analysis (MDA) techniques, on-line clustering of mineral process behaviour is possible and could help in the extraction of valuable process operation indicators. MDA can be used in different mineral processes such as flotation, grinding, smelting etc. In this paper, the focus will be on grinding process as it is the one of the most costly node in the mineral processing scheme (i.e. power consuming) and it is a highly multivariable process. Particularly for primary grinding mills (SAG/AG), more instrumentation outputs and more powerful and significant process indicators are needed for efficient control and optimisation.MDA is a novel approach suitable for understanding mineral process behaviour compared to the traditionally approaches based on empirical and phenomenological modelling. Multivariate techniques can be used for several purposes. In this paper, the following objectives will be addressed:operation diagnosis: Shift differentiation and operation test differentiation can be showed by using MDA tools such as principle component analysis and factorial discriminant analysis.operation performance monitoring: operation regimes can be evaluated by clustering based on an economic criterion performance such as costs, tonnage, product quality, profit, etcIdentification of operation behaviour (monitoring) and selection of drift correction trajectories (control):MDA can be used to identify periods of unusual or abnormal process behaviour and to diagnose, if it is possible, causes for such behavior."

Jan 1, 2003

By Vladimir P. Nebera, Kostas A. Matis, Piotr M. Solozhenkin, Anastasios I. Zouboulis

"Considered combination of two processes-selective sorptions of metals on biosorbents, inorganic sorbents and their following flotation by dissolved air(DAF). The process of biosorption, using as sorbent suspended non-living biomass (of Streptomyces genus, S. clavulgerus and S. griseus, fungi-Penicillium chrisogenum and Phizopus arrhizus, active slime) in fine particulate dispersion, combined with the application of flotation, for the consequent solid / liquid separation of metal-loaded biomass, has been studied for the removal of toxic and noble metals from dilute aqueous solutions. Biomass of microorganisms possesses great sorptive capacity, exceeding capacity of synthetic and natural sorbents. For instance, Micrococus luteus sorbed gold for 2h Au 253mg/g.The optimal conditions of effective flotation (more than 90%) of actinomyces biomass, loaded with toxic metal-cadmium were found. The adsorpbing flotation technique for copper, arsenic (III, V), chromium removal of metals on pyrite mineral fines (suitable industrial by- product) is an effective process.Dissolved-air flotation was also apllied in the case of dolomite/lead aggregates removal. A fatty acid was used as a flotation surfactant. The presence of dolomite fines aids the efficiency of the process, in comprarison with the flotation of alone lead hydroxide.A laboratory investigation was undertaken on the gold-thiourea system over the whole pH range, aiming at the separation complex of gold [Au(CS(NH2)2]2+ by flotation from dilute solutions. The reagents were found to improve gold recoveries remarkably: the recovery reached over 95%. A separation technique has been investigated, involving gold adsorptionon powdered activated carbon. Foam flotation was employed for the subsequent solid/liquid separation, using sodium oleate as surfactant. The content of Au were 500 mg/L in froth and recovery gold about 100%."

Jan 1, 2003

By Harri J. Lehto, Marja I. Oja

"The purpose of grinding circuits is to produce a particle size distribution that has as much as possible the wanted particle size class. In practise, however, the production of the wanted size class is not at all as simple as it sounds. In the case of industrial minerals for example the end user may give very tight specifications for the particle size distribution and for the chemical composition of the product. This leads in many cases to a very demanding grinding process, if we want to reach and maintain these specifications. In other words, the required size distribution is not necessary the best possible for the chemical composition.Screen models aim to predict the size distribution and flow of the products when a feed size distribution, feed tonnage, and grade efficiency curve are known. The approach used in this study was to select the most suitable empirical model for classification. Suitability of the existing models has been evaluated and accuracy compared. The tests showed that best grade efficiency model was the Rosin-Rammler model.The performance of a screen was evaluated in order to minimize the amount of fine material in the screen overflow. The experiments were carried out using Derrick single-deck screen, first alone with recycling and then in the closed circuit with a rod mill using two different scales. The separate screen tests showed the expected behaviour of the grade efficiency curves. In the pilot tests the Leonard screen efficiencies stayed almost constant. This suggests that the screen works better in a milling circuit. However the loading of the screen turned the product of the mill coarser that helped screening. The grade efficiencies obtained from the pilot tests had the same general shape. The regression analysis of the pilot test runs did not give an acceptable correlation for the parameters. This suggests that pilot tests cannot be directly used to scale or to optimise industrial milling circuits. However they can be used to predict the trends of behaviour of an industrial circuit."

Jan 1, 2003

By M. Wright, A. H. Mwale

Opportunities to promote enhanced eco-efficiency (i.e. the simultaneous improvement in economic and environmental performance) for the minerals industry exist across the whole value chain. However, given the current operational models of major companies within the industry, and their focus on refining of primary ore bodies, it is important to understand where such opportunities might lie within minerals beneficiation, as it is here that major environmental pressures are felt. This paper examines the combination of unit technologies in a minerals beneficiation train, and explores the inter-relationship between energy input and water consumption for a given mineralogy and product recovery, as these are two critical environmental issues which affect the overall viability of many minerals plants. In particular, we review constitutive relationships for each of the sub-processes of comminution, flotation, and tailings dewatering, and suggest how these might be integrated into a unified hybrid model, with particle size distribution as the key design variable. Such a model can then be used to explore the trade-offs between different performance objectives (be these technical, economic or environmental) as part of a multiple-objectives optimisation exercise. In this way, it may become practical to envision situations in which concentrate grade and recovery are sacrificed, marginally, in order to reduce energy demand in comminution, and improve overall water recovery. In addition, this work provides a useful baseline against which to analyse the potential for dry processing. This becomes more relevant as the industry commits to advancing the sustainable development agenda in the face of the increasing life -cycle costs and impacts of minerals processing operations, coupled to declining ore body grades, and the desire to maximise recovery of minor and trace elements. Some specific observations for copper are offered, supported by operational data from Zambian copper mines.

Jan 1, 2003

By Yongfu Yu, Xiaotie Wang, Fuguang Zhang, Liping Che

"Rare Earth water dregs is the drained waste dregs, which contains over 0.2 percent thorium dioxide and about 6-10 percent di-Rare Earth trioxide, which is beyond the standard of draining off that China governments set, so that the Rare Earth water leach dregs must be sacked and laid down in storehouse, which costs lots of money. It is a pity that the RE and thorium compounds very useful elements in industry are discarded. A lot of work must be carried out so that this resource was fully developed.In this paper, four separation techniques of recovery Rare Earth minerals and enrichment thorium element and reduction thorium content of drained dreg for the different test samples of Rare Earth water leach dregs which is radioactive waste dregs got from diverse locus are studied, respectively, and the separation characteristic and the separation process are described, using several combination processes of classification and gravity and flotation separation which were prepared according to the characteristic of test samples and technology. The test results show that the combination processes are the more remarkable separation techniques and the flotation reagents used in test can be applied to utilizing synthetically radioactive waste dregs. Through the combined technique process, three parts of products were obtained, namely, Rare Earth concentrate collected, the thorium product enriched and a large amount of the waste dregs product that can be directly drained and the total quantity is 50%-60%. In order to determine optimum technical condition, the effect factors of separation process were investigated in the test."

Jan 1, 2003

By Jan J. Cilliers, Nicolas Barbian, Esther Ventura-Medina

"Froth structure and stability are known to play an important role in determining flotation recovery and selectivity. An industrial sampling campaign was performed to develop a clearer understanding of the effect of flotation variables on froth stability and the role played by the resulting stability on flotation performance.Froth stability was estimated as the fraction of bubbles bursting on the surface of the froth through image analysis and the solids loading on the bubbles at the top surface. The image processing was performed using the Smartfroth software on the top surface of the froth. The system gives measurements of bubble size distribution, average bubble size and froth velocity. The froth velocity was used to estimate the volume of bubbles overflowing the weir yielding to the fraction of air overflowing the cell. This measurement is the complement of the rate of bubble bursting on the top surface. Also samples of the lamellae were taken by touching the top surface of the bubbles with a glass slide. Then, the amount of solids and liquid per unit area in the bubble lamellae was estimated gravimetrically. Both measurements were used to establish stability criteria.It was generally found that high air flowrates resulted in a drop of froth stability showed by a drop in the fraction of air overflowing and a decrease in the solids loading and simultaneously produced low copper recoveries and low concentrate grades. Deep froths only allowed a small fraction of air to overflow and consequently produced low recoveries. An increase to high frother dosage did not result in an improved fraction of air overflowing, hence producing low recoveries. Likewise, low frother addition only allows low recoveries because the resulting unstable froth cannot support itself. Low aeration was found to be preferential as it allowed high particle loading, therefore high bubble stabilisation, and low gangue entrainment, resulting in the highest flotation performance."

Jan 1, 2003

By S. Fiore, M. C. Zanetti, C. Clerici

The processes and fluxes of a cast iron foundry plant located in the North of Italy were analyzed in order to determine the amount and kind of wastes produced from the different activities. The main fractions are the molding sands, furnace muds and powders coming from the dust abatement plant, the exhaust lime, the furnace refractory, the metallic shotting and the sludges and powders coming from the dust abatement plant of molding lines for a total production equal to 800 t/d. All wastes were sampled and particle-size and chemically characterized to evaluate the best recycling or reuse solutions. Wastes were sieved and divided in three categories according to the particle-size dimensions: below 0.1 mm, between 0.1 and 0.6 mm and above 0.6 mm. The fraction above 0.6 mm dimension underwent magnetic separation to recover and quantify the potentially available iron fraction. The fraction between 0.1 mm and 0.6 mm was chemically characterized in order to understand if it could be fed to the sand regeneration plant. The below 0.1 mm fraction was characterized to evaluate the following recycling and reuse solutions: additive for molding sands and/or raw material for the concrete industry.

Jan 1, 2003

By Stoyan N. Groudev, Ioannis Paspaliaris, Plamen S. Georgiev, Irena I. Spasova, Kostas Komnitsas

"The uranium deposit Curilo located in Western Bulgaria for a long period of time was a site of intensive mining activities including both the open-pit and underground mining techniques as well as in situ leaching of uranium. The ore was rich in pyrite and, apart from uranium, contained some non-ferrous metals. The mining operations in the deposit were ended in 1990 but since that time the deposit is a permanent source of acid drainage waters. The generation of these waters is connected mainly with the oxidation of pyrite and other sulphide minerals by the indigenous acidophilic chemolithotrophic bacteria.Laboratory and pilot-scale studies revealed that an efficient clean-up of the above-mentioned waters was achieved by means of passive systems of the wetland type. In 2001 a wetland was constructed in the deposit to treat a portion of the acid drainage waters which were discharged to a small ravine. This ravine reaches into the Teina, a small river that is a tributary of the upper reaches of the Iskar river.The wetland was constructed in the ravine and its bottom was located on intrusive rocks with a very low permeability. The rocks were covered by a 30 – 50 cm layer consisting of a mixture of soil, plant compost and crushed limestone. The wetland was characterized by an abundant water and emergent vegetation and a diverse microflora. Typha latifolia, Typha angustifolia and Phragmites australis were the prevalent plant species in the wetland but species of the genera Juncus, Eleocharis, Carex and Poa as well as different algae were also well present.The acid drainage waters treated by the wetland had a pH in the range of about 2.5 – 4.1 and contained uranium, radium, some heavy metals (iron, manganese, copper, zinc, cadmium, lead), arsenic and sulphates in concentrations much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The watercourse through the wetland covered a distance of about 0.2 – 1.0 l/s."

Jan 1, 2003

By P. Huang, D. W. Fuerstenau

Various factors that control the natural flotability of talc, including differences due to crystal face and edge effects, were delineated. For study of talc depression phenomena, dextrin was used as a model depressant. For the enhancement of talc flotation, dodecylammonium acetate (DDAA) was used as the collector. The interaction of DDAA with talc was assessed by flotation experiments and electrokinetic (zeta potential) measurements, from which the role of hydrophobic bonding can be demonstrated. The results presented in this paper provide useful information on how the crystal chemistry and surface chemistry control the electrical double layer, adsorption phenomena, wettability, and flotation behavior of talc in aqueous media.

Jan 1, 2003

By A. V. Nozhkina

"Transformation of diamond into graphite was investigated in the region of diamond metastability under the action of media chemically active relative to carbon in the temperature range from 770 K up to 2200 K and pressure range from 10-3 Pa up to 3 GPa/IV VIII group metals of periodic system and oxygen were used as media chemically active relative to diamond.Methods of electron diffraction, chemical analyses, emission spectroscopy and X-ray phase analyses were used for determination of the reaction products.It was found that in the region of diamond metastability the stage of catalytic phase transformation of diamond into graphite took place during the interaction between diamond and metal. Metal reduce activation energy for transition of diamond into graphite from 109,4 kcal/mole to 77,4 kcal/mole.Kinetic of phase transformation of diamond into graphite was investigated.Pressure does not considerably influence on the rate of phase transformation of diamond into graphite in the presence of transition metals."

Jan 1, 2003