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By E. V. Leont'eva, V. R. Vafin, A. G. Kladova, N. L. Medyanik, A. P. Ponomarev

"The thermochemical technology for recovery gold, silver from mature flotation tailings of pyrite ores by two-stage sintering with chlorine-ammonium reagents and leaching of bakes with water is developed. The economic effect of the technology implementation is calculated. KEYWORDS Gold and silver recovery, mature flotation tailings, pyrite ores, chlorine-ammonium reagents, leaching INTRODUCTION The relevance of processing the technogenic reserves of ore mining and concentration wastes accumulated over the long operation periods of mineral deposits is beyond doubt. Hundreds of tons of precious and non-ferrous metals that were not recovered during the primary processing are concentrated in the accumulated wastes. For example, tailing storage facilities (TSF) at the mineral processing plants in the Southern Urals region of Russia hold more than one hundred tons of gold and thousands of tons of silver in the mature flotation tailings (MFT) of copper pyrite ores. Secondary processing of technogenic materials is facilitated by the fact that they are preprocessed — ground and compactly deposited on the surface, but complicated by the low (compared to ores) grade, uneven distribution of the valuable minerals, altered and unstable material composition of the mineral feed. This leads to low recovery rates of valuable metals by conventional physicochemical processing methods. It is necessary to develop innovative methods of deep integrated processing of industrial wastes, based on the study of the material composition of specific technogenic mineral resources and based on ensuring the environmental safety of the resulting secondary waste. MATERIALS AND METHODS The object of this study are the MFT of Uchaly Concentrator in the Republic of Bashkortostan, Russia, which processes copper pyrite and copper-zinc ores. According to the data of particle size, chemical, X-ray phase, and optical microscopic analyzes, samples of the MFT are characterized by considerable particle fineness (the fraction of the size class -41 µm is 89-90%), low grade of gold (1.7-2.0 g/t) and silver (18.0-19.5 g/t), comparable grades of iron (23.0-26.8%) and sulfur (28.1-28.7), but different grades of copper (0.12 - 0.73%) and zinc (0.34-1.26%). The most common mineral in the samples is pyrite (50 - 56%), found in intergrowth with grains of other sulfides (0.1-4%) - sphalerite, tennantite, chalcopyrite, covellite. Quartz and aluminosilicates are the dominant rock minerals (21-36%). Based on the results of the phase analysis, it was established that approximately 70% of the gold in the samples is found in a form that is resistant to cyanidation — it is locked in sulfides (52-56%) and quartz and coated by films. Along with sulfides and rock minerals, common gold and silver minerals (chalcogenides, intermetallides, native gold) in the form of submicro- and nano-sized precipitates are also associated with intergrowth of a complex structure. These features of the material composition allow classifying the MFT of the pyrite ores as a mature feed material and emphasize the need for chemical non-cyanide methods to recover gold and silver from the mature minerals and associations they are found in."

Jan 1, 2018

By Saveliy F. Kaplan, Valeriy N. Tsyplakov, Vasily N. Kovalev, Igor A. Agapov, Nikolai V. Vorob’ev-Desyatovskii

"Based on the experiments, a possibility of successful processing of double-refractory gold sulphide concentrates with a high content of natural organic carbon, which has a high sorption capacity toward gold chloride complexes, has been demonstrated. The proposed approach involves deep burnout of sorption-active organic carbon in an autoclave at a higher temperature and a longer retention time. INTRODUCTION It is known that one of the reasons why gold-bearing ores and concentrates are refractory is the occurrence of fine gold in sulphides (usually in pyrite and arsenopyrite) in ores and concentrates. In addition, refractory gold-bearing ores and concentrates also contain an organic carbonaceous material, which has a sorption capacity towards gold chloride complex, making the ore or concentrate even more refractory. In pressure oxidation, metallic gold is oxidized by Fe (III) aqua-ions and complex Au(Cl)4- ions are formed at temperatures over 180°C, in the presence of chlorides contained in ores. Complex gold anion is adsorbed on the organic carbon surface and then reduced to Au0; the chloride ion is regenerated and gold, adsorbed on organic carbon microparticles, is ultimately transferred to tailings (preg-robbing). Currently, there are several suggestions how to suppress preg-robbing (Simmons, 1998, Pyke, 1999, Rees, van Deventer, 2000, Zhao Jun-wei, 2008). It can be done by reducing the organic carbon content by processing (flotation, etc.),reducing chloride ion concentration by preliminary washing of concentrates in thickeners, reducing the adsorption capacity of organic carbonaceous material by introducing some organic substances that are strongly adsorbed on its surface (blanking agents), and reducing the redox potential of the slurry liquids by introducing neutralizing agents (limestone)."

Jan 1, 2018

By Shenxu Bao, Ying Bian, Xiang Liu, Liuyi Ren, Yimin Zhang, Chun Liu

Efficient enrichment of high-carbon low-grade mica stone coal containing vanadium is a key problem in the mineral processing field, and the mature beneficiation process is yet to be developed and applied. In this paper, a special mineral mica type of stone coal containing vanadium from Tongshan, Hubei Province, China was selected as the research object. Chemical analysis results show that this mineral contains V2O5 0.71%, SiO2 49.28%, C 13.44%, and CaO 6.26%. Scanning electron microscope (SEM) shows that vanadium generally exists in all kinds of mica minerals in 20 µm to 50 µm fractions. Mica stone coal containing vanadium must be ground to a particular fineness (approximately 45 µm). To reduce acid consumption during vanadium extraction from stone coal through acid leaching, a pretreatment process was proposed to enrich micas by using shaking table and flotation methods. A new combined technology process was implemented, resulting in a 0.96% improvement in the vanadium grade of raw materials in the succeeding process. Vanadium losses were controlled to 4.57% through the pre-concentration process, which reduced the burden of the subsequent procedure. The content of high acid consuming minerals was also diminished, such that approximately 6612 CNY was saved from producing 1 t V2O5. Therefore, stone coal containing vanadium should be pre-concentrated by using an appropriate combined process to reduce costs.

Jan 1, 2014

By Vladimir Vigdergauz

"Electrochemical studies of metal sulfides in connection with their floatability are discussed. According Frumkin, sorption of electroneutral organic substances has a maximum near the potential of zero charge. This idea initiated attempts of application of electrochemical methods for the controlling of organic collector sorption and mineral flotation. The lecture reviews results of electrochemical studies of the processes taking place during sulfide flotation: redox-state of mineral surfaces and xanthate solutions, xanthate sorption and hydrophobic layer composition, surface wettability and flotation recovery of sulfide minerals. Redox-transitions of minerals, transport of ions and charging of mineral surfaces, electroreduction of dissolved oxygen and accompanying processes of oxidation of minerals and reagents-collectors, - all these matters became the subjects of detailed research. Cyclic voltammetry, rotating disk electrodes, spectro-electrochemical techniques and other modern experimental methods now routinely accompany studies of mineral processing. Relatively new electroanalytical techniques like the voltammetry of mineral particles immobilised on electrodes using polymeric binders have become extremely useful for studying weakly conductive minerals and dispersed flotation products. Full discussion of electrochemical studies of metal sulfides in relation to mineral processing must include bioelectrochemistry and electrocatalysis which open exceptional possibilities for selective leaching of gold and non-ferrous metals. At this time, the paper focuses on the sulfide flotation as a potential-dependent process; the problem of oxygen and its influence on the sulfide flotation; the electrochemical aspects of xanthate oxidation and sorption; theory of suspended electrodes as applied to the mineral slurries and experimental study of the effect of electrochemical pretreatment of flotation pulps."

Jan 1, 2014

By I. Gombköto

In the EU-region, the automatically operated approximately 200 (rotating hammer) shredder plants processing large technical equipment (end-of-life vehicles, large household appliances) annually produces 8-9 million tons of non-metallic grinded by-product, which ends in landfills, without recovery. Although this by-product is organic material, still contains large amount of metal components worth recycling. These operations, such as shredding and processing end of life vehicles or mixed metal components are a growing market and it is become more potential if EU directive 2002/96/EC will become obligatory for new member and candidate countries and they have to apply EU regulations. Eddy current separators (ECS) are one of the most important units of separation of non-ferrous metals from insulators in waste recycling. The product of ECS processing of shredded ELV?s is usually a mixture of Al, Cu, Brass and stainless steel. This mixture has relatively low price on the market, while purified metal products are required by smelters for which shredder operators are able to get even higher price. Our aim at University of Miskolc was to find solution producing pure metal products using dry separation processes. Authors are presenting a possible solution, using ECS. Institute of Raw Material Preparation and Environmental Processing possesses an ECS, equipped with 305 mm wide belt, and a concentric magnetic rotor. The subject of our work was to investigate the behaviour of model particles with different shape, conductivity (aluminium and brass), orientation and size in order to separate Al and Brass. We used model particles with similar shapes of shredder plant originated ones. The magnetic flux and magnetic frequency was constant and derived by the design of the rotor. During our research work, belt speed and rotor speed of ECS were varied. The particle distance and trajectory caused by throwing was determined and the results are reported in this paper.

Sep 1, 2012

By E. A. Bekchurina, Yu. P. Morozov

"This paper presents the results of a study of the concentration of flotation froths in tapered chutes. The tests were conducted on lab and full-scale plants, and the results obtained were mathematically processed. The kinetics of monophase recovery from a stationary flotation froth, hydrodynamics of froth flows traveling in a tapered chute were investigated. The effect was studied of the mass fraction of the valuable component in the chute feed, yield of the chute’s overflow, and chute design on the concentration performance. Processing of the collected data revealed the general laws of the process and allowed to develop a technique for modeling concentration of the flotation froths of sulphide copper ore in a tapered chute to predict the performance without testing. It was found that concentration in tapered chutes allows to obtain products that are comparable in quality with froths after one or several cleaner flotation stages.INTRODUCTIONThe present production expansion rates require continuous improvement in the grade of flotation concentrates, while the grade of the mineral feed is constantly deteriorating. This leads to a significant complication of flotation flowcharts. Flowcharts become multi-staged with multiple cleaner flotations, negatively affecting the production costs.In recent years, researchers are paying close attention to the processes occurring in the froth layer in the flotation cells. Improving the concentrate grade is facilitated by secondary concentration of minerals in the froth layer, which consists in fixing the hydrophobic particles released as a result of the coalescence of the bubbles of the upper layer when moving downward at the liquid-gas interface of the froth layer. In this case, the released hydrophilic particles, trapped in the froth layer as a result of mechanical removal, migrate from the froth together with the liquid phase."

Jan 1, 2018

By Rob Morrison, Andrew Scott

"Long before a modern mine commences operations it has already become a wealth of information. After start up, it can generate enormous quantities of data - especially with semi-automated data acquisition by instrumented mine equipment.However, much of this data is of limited use for evaluation of (potential) performance unless it links in some way to the site business model.An underlying reason for this waste of data is that the different cultures, financial, technical, community, environmental, etc, not only have many areas of interest but also have very different conceptual models by which they evaluate performance.It is too ambitious to attempt to bring all of these cultures together - in a single step.However, the success of the Mine to Mill - project has demonstrated that substantial operational value can be added by using a more integrated approach to comminution. The next logical step is to integrate measurement and then to track performance from ore body model to saleable product and waste disposal. From resource to product also represents a path from very sparse, highly variable data to much more detailed measurement and more representative sampling.However, in both cases the data collected is strongly focused on the technical requirements - not on the business model.This paper considers how to define at least some of the key decision points in terms of some case studies.Performance data from many areas might be used to derive simple models which can then be used for forecasting and optimisation of planning."

Jan 1, 2003

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By József Faitli, Barnabás Csoke, Károly Solymár, Zoltán Hatvani, Dimitri Papanastassiou

"Grinding has a significant economic impact on ore dressing/processing, therefore the sizing of mills has an outstanding role.In most cases, the sizing of dry or wet mills for ore processing is primarily based on the determination of the Bond grindability index, using the Bond-Kjos-Rowland relations. In several cases, grinding takes place under conditions different from these and the grinding conditions have a great influence on the post-grinding process. This is particularly true for the grinding of bauxites where grinding takes place in alkali, often in higher temperature (up to 100 ºC) in alkali Liquor. So it is necessary to develop a testing method providing a reliable grindability index even under these special circumstances (grinding in alkalis medium at different temperatures) and allowing a more precise mill sizing. The new heated mill is suitable to determine the grindability index under temperature-controlled circumstances, in liquids with different temperatures (water, alkali). This paper presents in detail the equipment, the conditions (parameters) of the testing process for wet and alkaline grinding, the measuring results and the conclusions."

Jan 1, 2003

By S. J. Neethling

"Liberation is a key driver in all mineral separation processes as it limits the maximum possible grade for a given recovery. In flotation, this is further complicated by the fact that it is surface exposure of the floatable minerals that determines the ultimate performance. Liberation, grade and surface exposure are commonly quantified using Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM/EDX) analysis of polished sections. The intrinsically 2D nature of this technique can result in significant sampling errors and stereological effects that can affect the quantification of the ore’s textural characteristics. X-ray micro-Tomography (XMT) is an imaging method that can non-invasively and non-destructively delineate ore fragments in 3D, thus providing an alternative method that eliminates the need for stereological corrections and readily provides surface exposure. A methodology and automated algorithm were designed for extracting this information from images of closely packed particles, thus allowing samples containing a large number of particles to be assessed.The main drawback of XMT is that, unlike SEM/EDX, it cannot directly measure the mineralogy of the sample, instead producing a 3D X-ray attenuation map. We therefore also present an algorithm for calibrating the thresholding of the XMT images based on SEM/EDX images of sections through the same sample, thus allowing the liberation analysis to be carried out on a 3D mineral map in which the uncertainty in the mineral assignment is small and statistically quantified.The methodology was tested on low grade porphyry copper ore as this is both an industrially relevant and traditionally difficult system to quantify using XMT due to the similarity in the X-ray attenuation of the sulphide species, especially the pyrite and chalcopyrite. As each 3D volume imaged contain 100-1000s of grains, large data sets can be readily produced. By dividing these particles into classes based on both their surface exposure and grade, the extent to which there is preferential breakage of the particles can be assessed—an important consideration if sufficient surface liberation for good flotation performance is to be achieved at coarser particle sizes. It is also shown that erroneous conclusions can be drawn when basing the analysis on 2D sections through the particles."

Jan 1, 2018

By Osvaldo A. Bascur, J. Pat Kennedy

"The profitability of mining and metallurgical operations continues to lag behind that of other industries despite the technical advances that have occurred in recent years. A primary reason for poor performing in this economic sector is the lack of integration of mining and metallurgical information. The mine cut-off grade can be optimized if mining and metallurgical engineers have the data to optimize milling for the type of ore in hand.Integration of mine transactions, stockpile inventories, process flows and assays is the key to determining the economics for each blast strategy in a mining site. Real-time information from manufacturing assets greatly affects the profitability and flexibility of a company, but gross errors from faulty sensors, inaccurate instrument calibration, or incorrect process models may corrupt actionable information. New software tools can model the process, sift through available data to identify and eliminate gross errors, and use statistical data reconciliation to create materially balanced and consistent readings. The reconciled data is unified for use by both monitoring and decision making processes.Creating a real-time information environment where upgrade and change are allowed is becoming an accepted methodology to accelerate and simplify the integration of applications such as production monitoring, equipment performance management and yield and inventory management.This paper describes the data integration requirements in a mine, concentrator and port for unification of the redundant data. The capture of the mining events, stock pile management and the metallurgical information is the base requirements for a dynamic environment to reduce the overwhelming amount of information to unified set of information. Part of any decision support program should entail these results to continuously improve the measurement system to address the costs in mine and milling the ore."

Jan 1, 2003

By P. K. Fedotov

At projecting mining-concentrating complex at the deposit ?Zapadnoye? (Russia) it was considered to enable an opportunity of refusal from conventional SAG-mills. First time a scheme of gold bearing ore destruction using Roller Press RP 5-100/90 had been developed and integrated. The plant was launched in summer 2003 and presently it has achieved designed technological parameters, processing throughput comes to 1 million tons of the ore per year.

Jan 1, 2014

By V. A. Zhilina, I. V. Shadrunova, O. E. Gorlova

"The aim of the study is to develop and scientifically justify a new adaptive approach to the separating processes of deep and complex processing technogenic mineral raw materials. Technogenic mineral resources as a waste of mining and processing industry are mostly complex objects that have specific features of material composition and technological properties and make it processing ineffective with traditional schemes of mineral raw materials enrichment. Mineral wastes are regarded in this study as a complex object with a large number of signs in conditions of uncertain environment and object. However, adaptation is regarded as the process management system’ adaptation to the specific the properties of the object and the environment that has several hierarchical levels corresponding to different stages in the management of complex object. An adaptive approach is considered as a methodological basis of multivariate schemes for opening the mineral resources and creating mechanisms that could transfer these potential technogenic resources to the actual that significantly expand the mineral resource base of the country's black, coloured, rare, noble metals and construction materials. In this case, potentially the solution to the most pressing social and environmental problems associated with the adverse effects of past economic activity simultaneously with the commercial objectives. This approach to the wastes mining and related processing manufacturers meets the core idea of sustainable development as the balance of interests of State, society, business, private enterprise and each person in the areas of rational use of resources, economic efficiency and environmental safety. On the example of metal-containing raw materials in the form of slags of ferrous and nonferrous metallurgy, ferrous metallurgy sludge, mature fine tailings, the application of adaptive approach illustrates to the development of technologies of its deep and complex processing as phased, thoughtful movement from a comprehensive study of technogenic raw materials to build optimal topologies of technological schemes for processing the mineral wastes. INTRODUCTION Involving the Russian economy in the system of global economic relations significantly changes the nature of the country's competitiveness in the development of the world market and urgently requires competent management of its own natural and mineral resources. The latter at the present time in real economic processes cease to be a passive material foundation and become the producing basis in the production processes in the status of so-called natural capital. Introduced in the field of economic theory at the end of the 20th century, this term means both the flow of natural services and real natural resources. Consequently, natural objects, which act as natural resources of a certain production, today must necessarily be evaluated in a strategic sense. Modern standards of sustainable development presuppose that the economy should equally be oriented to balance the interests of the state, society, business, individual enterprise and each person in the spheres of rational use of resources, preservation of healthy ecosystems, ensuring well-being, high quality of life and environmental safety of not only the current generation, but also respect for the rights of future generations, that is, intergenerational equality. Most types of minerals are classified as non-renewable resources, therefore resource-saving in the sphere of mineral and raw materials complexes is one of the most important factors-indicators characterizing the degree of approximation to the model of rational subsoil use, and, consequently, sustainable development (State Report, 2017)."

Jan 1, 2018

By Markus A. Reuter, Jacques J. Eksteen

The modelling of bath type furnaces tends to be either fundamental in nature or total empirical "black box models". While models of the first kind are robust, they tend to lack accuracy, in cases where they are to be used for process control, and may take an overly long in development time. On the other hand, black box models tend to lack robustness of prediction for all circumstances and tend to be limited to interpolate based on historical data. While this may very often provide short-term accuracy, the models may have problems with stability in the long term. Moreover, the model structure may not reflect any of the fundamental properties of the system and remains opaque to fundamental analysis. The aim of the model development is in obtaining a model that have robustness, high accuracy, a short development time and which is adaptive to a changing environment. The models are specifically developed for on-line decision support or control of furnaces. The modelling approach is evaluated for a chromite bath smelting furnace. The role of systems analysis, mass balance smoothing, thermodynamic analysis are integrated into one generic algorithm for bath type furnaces. Therefore, this paper argues that to understand complex metallurgical furnaces a hybrid approach is the only method to fully grasp the intricacies of metallurgy, to improve operations, economics as well as environmental performance.

Jan 1, 2003

By F. Henríquez

Traditionally, the implementation of an automated control for a ball mill has been a challenging one. First, it must be capable of processing a variable SAG mill feed while at the same time avoiding to become a process bottle neck. Second thing is, it must deliver an adequate quality product (P80) to the process downstream. Then the ball mill itself and its associated classification equipment has problems of its own: it must maintain adequate control of cyclone?s pressure, density and pump-box level with often, less manipulated variables than needed, namely, variable pump speed and the opening/closing of cyclones. Thus, it becomes a non-linear multi-variable type of process with often too multiple and contradictory control objectives to satisfy simultaneously. On top of that, to extend cyclones availability and yet, maintaining their performance, is must both for process and maintenance purposes. Trying to solve the puzzle, Minera Los Pelambres implemented a novel and successful combination of MPC (Multivariable Predictive Control) and advanced control in two of its newest ball mills, reducing considerably process variability while maintaining high throughput and keeping the process well within constraints limits. Because of their differences in processing capacity, size and topology, two different stabilizing-control strategies were developed, tested and tuned. Hence, for both control approaches their implementation process, main results, areas of applicability, limitations and their key performance indicators are discussed further. This paper also discusses the need of such advance control technologies in the mining industry, including the impact of these technologies on best practices for their implementation, operation and long term sustainability

Sep 1, 2012

By Felipe Sepulveda, Edelmira Gálvez, Luis Cisternas

"In mineral processing, the recovery and/or concentration of the value components cannot occur in one operational stage, therefore requiring the use of separation circuits based on several flotation stages. The components to be separated are typically distributed at different concentrations and different particle sizes, resulting in different levels of recovery. Typically, more than one value component must be selectively removed by exploiting the differences in the components’ floatability at different pH values, pulp potential and particle size. Several methods for the design of these circuits are available in the literature, but comparatively few studies present circuit analysis tools or address the design of a multiple-product flotation circuit. In this study, global sensitivity analysis was used to analyze a flotation circuit with several products, such as copper, lead and zinc. This analysis was based on the Eureka mine concentrator plant. The analysis was performed for each of the sections of the circuit as an overall evaluation of the circuit. The Sobol’ method and the correlation method were used to evaluate the Eureka mine concentrator plant using the SimLab 2.2 software."

Jan 1, 2014

By B. Vasanthakumar, H. Ravishankar, S. Subramanian, J. Braun

The flotation of sphalerite and galena in the presence of intra- and extra-cellular components isolated from Bacillus circulans before and after adaptation to the chosen minerals has been studied. Based on various biochemical treatments, the key biomolecule primarily responsible for the flotation of sphalerite has been identified as DNA, which functions as a bio-collector. A noteworthy finding is the considerably higher flotation recovery of sphalerite obtained in the presence of single stranded DNA (79.8%) vis-à-vis double stranded DNA (50.2%). Selective flotation tests using the soluble fraction obtained after thermolysis treatment highlight that sphalerite-adapted cells yield a higher selectivity index (S. I.) of 31.2 compared to galena-adapted (S.I. 4.3) or unadapted (S.I. 12.2) cells. During bacterial adaptation to the above chosen minerals, the quantitative and qualitative changes in the surface potential, surface morphology and cell wall components have been monitored. The prior adaptation of the bacteria to sphalerite results in the secretion of a higher amount of proteins, eDNA and phosphate, whereas adaptation to galena leads to a higher amount of polysaccharide, uronic acid and acetylated sugar, vis-à-vis the unadapted bacteria. A significant observation is that the bacteria undergo a change in morphology from rod to sphere as a strategy to resist metal toxicity during adaptation to galena. Interestingly, this phenomenon is not observed during bacterial adaptation to sphalerite. This morphological transition has been shown to involve changes in crucial cell wall components as well as changes in the levels of expression of bacterial cytoskeleton element mreB gene involved in the maintenance of the rod shape. The sequence of B.circulans mreB gene has been identified using Polymerase Chain Reaction (PCR) followed by DNA sequencing.

Jan 1, 2014

By Robert van Hille, Alison Lewis

The precipitation of a selection of metals from both a synthetic and an actual metal-rich effluent was investigated. The experimental aspects of this study were carried out in a two-stage process consisting of a pre-treatment clarifier and a fluidised bed (pellet) reactor. Each unit operation in the two-stage process was investigated separately. The pre-treatment clarification stage at pH ˜ 5 resulted in a 99.9% removal of iron and 97.3% removal of aluminium. The pellet reactor was used to precipitate nickel as nickel carbonate from a pure stream and a removal efficiency of 99.6% was achieved. The high local supersaturation at the reagent inlet points caused the formation of a large amount of fines, but these agglomerated onto the pellets up the length of the bed. For copper precipitated as copper sulphide from a pure stream, a maximum removal efficiency of 92% was achieved. The high local supersaturation at the reagent inlets also caused the formation of a large amount of fines, but the extremely sparingly soluble nature of copper sulphide meant that the fines were not agglomerated up the length of the bed. For removal of cobalt as cobalt carbonate from an actual stream, a stable cobalt removal of only 60% was achieved. This was found to be due to the presence of magnesium, which reduced the cobalt precipitation efficiency through the formation of the magnesium bicarbonate ion.

Jan 1, 2003

By Lj. D. Andric

Development of modern devices for mechanical and mechanochemical materials activation has been dated since the beginning of last century. Rapid development of high-energy mills that are different in type, size, design and performances, has been occurred during the last four decades. Because of complete understanding of mechanical processing, entire knowledge of theoretical principles of high-energy mills is necessary. These principles are main causales of process that are happened in materials during the mechanical activation. This paper is occupied by theoretical principles of operation of high-energy mills. Conventional high energy mills with balls, high-energy planetary mills and high-energy vibrational mills are particularly considered in the paper.

Jan 1, 2014

By Kang N. Zhong, Hui H. Luo, Yi H. Wei, Yu L. Wang

"More than 85% of phosphorous reserves in China occur as middle-low grade phosphate of sedimentary origin. The main gangues are dolomite, quartz, silicates, and clays. The characteristics of minerals are finely disseminated. Flotation results have shown that the floatability of apatite of this kind of ore is much worse than that of igneous and metasedimentary origin because of its high specific surface area. Although some effective depressants, such as naphthalene sulfonate and phenanthrene sulfonate, are used to decrease the MgO content in the P2O5 concentrate, its presence is still high (about 2%) in the Chinese concentrates. Meanwhile, the wastewater may cause some environmental problems. Batch flotation results and measurements of specific surface area and CO3 2- have revealed that there is a relationship between the floatability of apatite and the surface area.A two-stage flotation flowsheet, which includes a combination of direct and reverse flotation, was developed for beneficiating sedimentary phosphate ores. The direct flotation was conducted in an alkaline medium and most of the apatite and carbonate minerals floated leaving quartz and siliceous gangue in the sink. In the reverse flotation circuit, the floated product was further beneficiated in an acidic medium to eliminate the carbonate as a float product. Apart from the high quality of concentrate, the two-stage flotation also facilitated the treatment and the recycling of wastewater. A wastewater recycling procedure was developed and tested in a continuous flotation process. The key factor was the careful selection of effective and non-toxic reagents."

Jan 1, 2003