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By U. A. Peuker, A. Grohme

"The cost effective and sustainable production of high purity rare earth elements is still challenging. The most commonly used method, known as solvent extraction, is very complex, needs many steps to separate the rare earth ions in a high purity, and causes a lot of environmental problems. An alternative method is the utilization of a separation column filled with adsorbent material. Within the column the desired target substance can be selectively separated out of a multi component mixture in one step. To find out if an adsorption material is suitable for the separation with a column, a characterization of the adsorbent material is necessary. In this paper are described the usage of modified activated carbon (oxygen and phosphorous modification), Di-(2-ethylhexyl) phosphoric acid (D2EHPA) impregnated Amberlite® XAD 7 HP and Lewatit® VPOC 1026 as adsorption materials. Several adsorption isotherms and process conditions are determined to characterize the selectivity between the adsorption materials and different rare earth ions. With these isotherms the mass specific rare earth ion retention for the adsorbent materials can be calculated. In addition to the isotherms the best working parameters are investigated e.g. pH-value and the time for equilibration. Finally, the separation factors between two rare earth elements are determined. The separation factor shows how successful a two element system can be separated."

Jan 1, 2014

By C. P. Lowes

"The REFLUX™ Classifier (RC™) consists of a fluidized bed housing, with a system of parallel inclined channels above. This system performs a simultaneous gravity separation and desliming of the feed material, utilising the inclined channels in order to retain the relatively fine dense particles. These particles promote the formation of an autogenous dense medium within the fluidized bed. Relatively large, low density particles are displaced from the fluidized bed and conveyed upwards through the inclined channels reporting to the overflow with other finer particles. Given the hydrodynamic role of both the particle size and density in determining the particle transport through a water based suspension, all gravity separators operate over a limited size range. In the case of the REFLUX™ Classifier, efficient separations can be produced across a very broad size range, from nearly 10 mm down to 10 m, however, for a given application the size range is much more limited. This study was concerned with the processing of dense minerals over a broad size range, and the need for multistage processing. Here the overflow from the first stage cascades to the second stage, incorporating coarse gangue rejection. This approach is shown to deliver remarkably high grades and recovery.INTRODUCTION The performance of the REFLUXTM Classifier (RC™) in beneficiating fine coal is well documented (Galvin, 2012). Although the technology can be applied to relatively fine particles below 0.1 mm, or coarser particles below 2.0 mm or even 8.0 mm (Galvin et al., 2010), in each case the technology is applicable to limited particle size ranges. In coal preparation, the most common size range is 0.25 to 2.0 mm, covering an eight-fold range in the particle diameter. Coal has a relatively low density, typically below 1600 kg/m3, with a significant portion below 1400 kg/m3. In water, the buoyant density difference (~ 400 kg/m3) is therefore low compared to that of gangue minerals (1600 kg/m3) by a factor of 4, enhancing the potential for separation. Thus, in coal preparation, the technology can be applied over a commensurately broader size range, typically up to eight-fold."

Jan 1, 2018

By Matt Kilburn, Liming Lu, Steve Suthers, Alexander Edenton, Rodney Smyth, Matt Adam

"Magnetite concentrate is naturally good for pelletising. However, due to the depletion of reserves of traditional high grade hematite iron ore worldwide, the usage of magnetite concentrate in sintering is expected to increase substantially. Magnetite concentrate is typically high in Fe grade and releases extra heat when oxidised to hematite. This will not only improve the quality of agglomerates produced, but also have a potential beneficial impact on the fuel consumption of the agglomeration process. There are an increasing number of magnetite projects currently being considered and developed. However the concentrates from some of these projects are too coarse as pellet feeds and much finer and denser than normal sinter feeds. Accordingly, special strategies are required in order to utilise the coarse magnetite concentrates at high proportions in pelletising and sintering. This paper discusses various raw material preparation technologies and blending optimization methods demonstrated to be effective for improving the sintering and pelletising performance of coarse magnetite concentrates. Pre-granulation and addition of binders, such as hydrated lime, were found to be particularly efficient in recovering the sintering productivity of sinter blends containing magnetite concentrates. In pelletising, HPGR (High Pressure Grinding Rolls) grinding enabled production of good quality pellets from 100% magnetite concentrates and optimized blends containing up to 70% magnetite concentrates also formed good pellets.INTRODUCTION Magnetite concentrates are often used as feed materials for pellet plants or sinter plants depending on their grades and grain sizes. To achieve the required quality of green and fired pellets, the concentrates often need to be ground very fine (80% passing 38- 45 m), which inevitably consumes a great amount of energy. Therefore, efficient grinding processes are required to reduce the amount of energy consumption needed to achieve the sizing and chemical specification of pellet feeds. The use of magnetite concentrates in sintering has the potential to improve sinter chemistry, which is deteriorating over time due to the slowly decreasing grade of direct shipping iron ores around the world (Yang and Mathews, 1997; Yang and Witchard, 1998, Yang and Davis, 1999; Yang 2005). However, methods are required to allow the utilisation of high levels of concentrates in sintering while maintaining productivity and sinter quality (Han and Lu, 2017)."

Jan 1, 2018

By Marina Nicolova, Irena Spasova, Plamen Georgiev, Stoyan Groudev

Different strains of "silicate" bacteria were used to improve the quality of kaolin by different ways of treatment. All strains formed large slimy capsules consisting of exopolysaccharides and were related to different species of the genus Bacillus, mainly to B. circulans and B. mucilaginosus. It was found that even a short contact of some hours of well developed cultures of these bacteria resulted in improvement of the bending strength and the other ceramic properties of the kaolin. The improvement was connected with the action of some secreted microbial metabolites such as soluble heteropolysccharides, monosugars and organic acids. The best results were achieved by continuous cultivation of bacteria in the presence of kaolin with a high relative humidity and subjected to periodic stirring.

Jan 1, 2014

By G. K. Nimal Subasinghe

The establishment of grind size that optimally liberates the valuable mineral for efficient down-stream processing is of great importance for most mineral processing operations. Reasonably accurate comminution models as well as models of downstream separation processes may be found in the literature but their use in optimizing grind size is limited without an associated liberation model. In this work, an attempt has been made to address the above shortcoming by demonstrating how the effective parameters of the downstream flotation process may be predicted from the liberation characteristics based on the ore texture data for a disseminated nickel ore. In this regard, the liberation model based on linear intercept distributions of mineral and gangue proposed by King (1979) and its application to predict the flotation performance of an industrial plant demonstrated by Schaap (1979) may be considered useful contributions. However, while the model proposed by Schaap is simplistic enough, it is based on several assumptions due to the non-availability of intercept length measurements on the parent rock, in particular, on the extent of mineral exposure on the surface of comminuted particles. In this work, the linear mineral and gangue intercepts on polished specimens of a binary ore, comprising darker pentlandite as the valuable mineral and lighter barren host rock were measured using an image analyser. The resulting intercept distributions followed negative exponential distributions. Using the mean sizes of mineral and gangue intercepts, the proportion of liberated, compo-site and mineral occluded particles of a given size, the extent of mineral exposure on the surface of particles and their mean mineral contents were calculated using principles of renewal theory. The rock was then crushed and ground and different size fractions were floated. It has been shown that the parameters of observed recovery data based on 1st order kinetics such as the associated rate constant and ultimate recovery agrees well with those predicted from the quantities calculated above. This work has important practical implications since it can indicate variations in flotation performance arising from changes in mineralization within a large ore body.

Jan 1, 2014

By L. Stamenov, H. Bouzahzah, S. Gaydardzhiev, D. Naumov

"The Chelopech epithermal arsenic bearing high-sulphidation, copper-gold deposit located in Bulgaria is often referred as the richest European gold deposit currently under exploitation. Key points from the flotation circuit of the processing plant have been sampled and selected physicochemical parameters measured. Plant survey has followed with selected samples being submitted to chemical and mineral liberation analysis (MLA). Quantitative analysis has enabled to link the flotation response of the main copper bearing minerals with the physiochemical parameters (Eh, DO, EDTA extractable Cu and Fe) being measured. Data from mineral liberation analysis have highlighted an important process-relevant information explaining the variable floatability in the various granulometric classes.The low chalcopyrite recovery could be linked to the non-sufficient amount of dissolved oxygen measured in the copper selective flotation circuit. Given the finely-disseminated copper bearing minerals, the observed copper losses inside the flotation could be also explained by the insufficient degree of liberation of the mineral grains. Suggestions for improvement in metallurgical recovery are therefore proposed.INTRODUCTIONThe Chelopech deposit is a high sulphidation (HS) volcanic-hosted epithermal gold-copper one (Bonev et al., 2002; Kouzmanov et al, 2009; Strashimirov, et al. 2002). It is considered as one of the largest and economically most important ore deposits in Bulgaria, and often is referred to Europe’s largest currently mined gold resource. It is located in the Srednogorie zone which falls within the central sector of the extensive Tethyan–Eurasian copper belt formed during Mesozoic–Cenozoic time along the southern margin of Eurasia. The Srednogorie zone has the features of a subduction-related, Late Cretaceous island arc, with development of a calk-alkaline to sub-alkaline volcano-plutonic magmatism and associated hydrothermal ore deposits (Bonev et al., 2002).Ore mineralisation occurs as veins, mineralised breccia, and massive sulphide replacements and disseminations. Three mineralisation stages have been identified at Chelopech deposit. An early pyrite–marcasite mineralisation (stage I), characterised by disseminated to massive pyrite followed and partly brecciated by enargite– luzonite and tennantite–chalcopyrite–bornite (stage II) mineralisation. The gold is met in ores belonging to the stage II. Sphalerite and galena veins characterise stage III, best developed below and adjacent to the pyrite–enargite– chalcopyrite ore bodies. Advanced argillic altered volcanoclastic rocks commonly host this mineralisation (Chambefort and R. Moritz, 2014)."

Jan 1, 2018

By H. Lieberwirth, M. Hesse

"Selective comminution (SC) is beneficial for the treatment of primary raw materials, especially if it is utilized in the pre-concentration process. Pre-concentration processes are applied in mineral processing to relieve subsequent processes and to achieve a higher efficiency. SC is also a promising method for the treatment of low-grade ores and waste dumps. With SC, various components can be separated such as valuable minerals from waste, ore from wall rock and different ore varieties within a deposit. SC is a property of a comminution system and leads either to a preferred crack propagation in one component (called preferential breakage) or to a preferred crack propagation along the grain boundaries (called interfacial breakage). SC results from different comminution behavior of various components in the feed material. For mechanical comminution, the preferential breakage seems to be the most important case of SC. Hereby SC generates only the difference in the particle size which can finally be used as a sorting parameter. A sorting process which uses SC depends on three parts: the feed material, the comminution machine and the separation machine. The feed material defines the potential for SC. Differences in properties like strength, toughness and density which are related to comminution are often used. The comminution machine has to exploit this potential. The extent of the exploitation can be influenced by the machine design, material and operational parameters. After SC, the various components are still combined in the product. So ultimately, a separation machine is needed. At preferential breakage, a simple screening machine can be used. The basics about SC will be presented at first. This contains relationships between material properties, the kind of loading in the comminution machine and the SC effect. These basics can be used for example to exploit a potential to SC for a pre-concentration step or to avoid the SC for a higher efficiency of subsequent processes. Based on recent investigations with impact load, the influence of the important parameters compressive strength, density, particle size and impact velocity to the SC will be shown, using examples of lead-zinc ore comminution and fluorspar processing."

Jan 1, 2018

By Danuta Szyszka

This paper presents results of tests performed to determine minimum concentration of a surfactant used at which coalescence of air bubbles during flotation has low probability to occur. The measurements of the critical coalescence concentration, also known as CCC, were carried out in a device consisting of glass cell into which air was pumped by peristaltic pump through capillaries. The flotation foam was recorded with a high resolution digital camera. Basing on the video records, average diameters of the air bubbles were measured and the values obtained were subsequently used to determine the CCC values. The author of paper determined the CCC values of surfactants tested using the linear regression method, and subsequently analyzed the results obtained. To define initially the capability of a tested surfactant to flotation, efficiency of multiparticle model flotation and flotation of individual size fractions were determined in a flotation apparatus for laboratory use in the presence of only foam making agent at CCC value pre-determined during the tests previously carried out. The tests of coalescence phenomenon were carried out with use of selected flotation frothing agents.

Jan 1, 2014

By Hideki Yamamoto, Norihiro Murayama, Junji Shibata

"Hydrothermal syntheses of zeolite from coal fly ash were carried out by using various alkali sources. NaOH, Na2CO3, KOH, K2CO3 and their mixture were applied for an alkali source of zeolite synthesis. The various physical properties of the reaction product, such as the kind of zeolite crystal, cation exchange property, surface texture and so on, was investigated through the zeolitization reaction from fly ash. The mechanism of zeolitization reaction was considered from these results.Zeolite P(NaP), hydroxysodalite(HS) and chabazite(K-CHA) are synthesized as zeolite species, when fly ash hydrothermally reacts in various alkali solutions at 393K. The crystal structure of the products obtained in NaOH solutions for 3h changes from NaP to HS with increasing NaOH concentration. K-CHA formation in KOH solutions needs 10h of reaction time, which is longer than that of NaP or HS.Dissolution, condensation and crystallization steps exist in the zeolitization reaction from fly ash, and the particle surface of products remarkably changes in each step. The fly ash is spherical particles and the surface is smooth(Fig.1(a)). The dissolution of fly ash occurs in the heating process until 393K, and the particle surface changes like unevenness(Fig.1(b)). In case of NaP, the condensation of aluminosilicate ions takes place at 373-393K, and the amorphous aluminosilicate is deposit on the unreacted fly ash(Fig.1(c)). The crystallization of NaP already begins to occur at 393K and the surface is covered with fine zeolite crystals for 24h(Fig.1(d))."

Jan 1, 2003

By H. Pearce, A. E. Lewis, A. Ochieng

Hydrodynamics and mixing are fundamental to the operation of mineral process systems such as flotation cells and metal precipitation reactors. The computational fluid dynamics (CFD) technique has been employed in the present work to study the hydrodynamics in a mixing vessel stirred with either a Rushton turbine or a pitched blade impeller. The multiple frame of reference (MFR) approach has been used to model both impellers. A draft tube was used only in the Rushton turbine stirred vessel. The flow profiles for the pitched blade impeller have been studied in three regions; below the impeller tip, at the middle of the tank, and near the liquid surface. The simulation results were compared with literature data obtained using a laser Doppler velocimetry in the three regions of the vessel, and it was found that the model predictions were better in the impeller region. There was a poor prediction of the experimental results in the region closer to the liquid surface; however, this was improved when the turbulence parameter (C2) in the k-e model was set to a higher value. The value of the impeller clearance at which the Rushton turbine generates an axial impeller type flow has been determined and it has been shown that, at this clearance, a draft tube can be used to enhance axial flow in a Rushton turbine stirred reactor.

Jan 1, 2003

By Ljubisa Obradovic, Baisui Han, Batnasan Altansukh, Zoran Stevanovic, Atsushi Shibayama, Jonovic Radojka, Daizo Ishiyama, Kazutoshi Hag, Radmila Markovic, Ljiljana Avramovic

This paper discussed a combined froth flotation and high pressure leaching (HPL) process to recover copper from mine tailings. At first, froth flotation were carried out using the mine tailings sample under various conditions in the presence of different pH (3.5-10) and sulfurizing reagent value (0-1000 g/t), respectively. As a result, optimum condition (sulfurizing reagent of 1000 g/t, pH of 10, PAX (collector) of 100 g/t and MIBC (frother) of 200 g/t) was found for froth flotation of copper. The effects of sulphuric acid concentration, leaching temperature, total pressure (steam pressure plus oxygen pressure) on high pressure leaching (HPL) of mine tailing were investigated using sulphuric acid solution in the presence of oxygen. The best conditions for HPL were obtained to be sulphuric acid concentration: 0 mol/L (water), leaching temperature: 170 ?, total pressure: 2 MPa, leaching time: 1 hr and pulp density: 100 g/L. The leaching rate of copper reached nearly 99 % and the concentration of copper in pregnant leach solution (PLS) was 0.24 g/L. Finally, copper in the mine tailing was recovered using froth flotation followed by HPL. As a result of a combined froth flotation and HPL, the vast majority of copper (99 %) from the mine tailings was extracted.

Jan 1, 2014

The multiphase reactive flow in process equipments, e.g., fluidized beds, involves complex coupling among flow, heat/mass transfer and reaction kinetics over scales ranging from molecules, sub-particle eddies up to equipments. Conventional two-fluid model (TFM) ignores the effects of meso-scale structures, and hence is not suitable for describing the intrinsically multi-scale heterogeneity within multiphase systems. To be consistent with the meso-scale structures, we proposed a structure-dependent multi-fluid model (SFM), and closed its drag force by invoking the stability condition defined in the energy-minimization multi-scale (EMMS) model. The SFM reduces to the conventional TFM if homogeneous distribution is assumed within each grid, and reverts to the original EMMS model if it is used to describe steady state, global behavior of a fluidized bed. The multi-scale computational fluid dynamics (CFD), which is characterized by coupling of TFM and EMMS drag coefficient, can then be viewed as a simplified solution of the SFM. We demonstrate that the SFM significantly improves the accuracy and at the same time enables higher efficiency by allowing for much coarser grid used than in TFM. Recent application of it in 3D, full-loop, transient simulation of industrial processes, e.g., fluid catalytic cracking, coal combustion, gasification, kaolinite clay calcinations, shows its advantages in helping design and troubleshoot multiphase process equipments. Keywords: meso-scale, SFM, multiscale, CFD, simulation, structure, EMMS, multiphase

Sep 1, 2012

By Juan Pablo Segovia, Alonso Pereira, Fernando Concha, Daniel Sbarbaro, Samuel Vergara

A robust theory of sedimentation-consolidation evolved and was accepted by researchers worldwide in the last two decades of the 20th century. This theory provides a reliable method of thickener design, simulation and control. However, a process model, simple or sophisticated, empirical or phenomenological, is useful only if it is possible to determine, in an objective way, its experimental parameters. Although it is important for a mineral processing plant to perform periodical laboratory test to determine thickening parameters, and in this way adjust the operation, not always these tests represent the behavior of the material in the process. It is important to be able to determine these parameters directly in the thickeners. Research workers at the University of Concepción developed new instrumentation, algorithms and software for the determination of thickening parameters. In this paper, two new instruments for the on-line determination of the settling velocity and the compressibility of the sediment are presented and results of tests in a major mineral processing plant in Chile are described.

Jan 1, 2014

By Kyle P. Flynn, Frank J. Hrach, James D. Bittner

ST Equipment & Technology, LLC (STET) has developed a processing system based on tribo-electrostatic belt separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. In contrast to other electrostatic separation processes that are typically limited to particles greater than 75µm in size, the triboelectric belt separator is ideally suited for separation of very fine (<1µm) to moderately coarse (300µm) particles with very high throughput. The high efficiency multi-stage separation through internal charging/recharging and recycle results in far superior separations that can be achieved with a conventional single-stage free-fall tribo-electrostatic separator. The triboelectric belt separator technology has been used to separate a wide range of materials including mixtures of glassy aluminosilicates/carbon, calcite/quartz, talc/magnesite, and barite/quartz. An economic comparison of using the tribo-electrostatic belt separation versus conventional flotation for barite / quartz separation illustrates the advantages of dry processing for minerals.

Jan 1, 2014

By Tohru Kamo, Shigeyuki Katano, Hideki Nakagome, Maiko Adachi, Shingo Nakamura, Kaneshi Taniguchi, Zar Zar Hlaing, Takaaki Wajima

Tantalum capacitor is a small-sized and has large capacity, and is indispensable for electric equipment. The demand increases year by year, and a quite large number of used tantalum capacitors is generated. Recovery of tantalum from tantalum condenser is recently important since production of tantalum have not been stable for the price and the quality. However, recovery of tantalum from tantalum-condenser is difficult since tantalum parts strongly cover with the flame retardant resin made of halogenated compound (mold resin). This research investigated recovery of tantalum parts from tantalum condenser using steam gasification with mixed molten carbonate. Mixed molten carbonate (Na2CO3:K2CO3:Li2CO3 = 1:1:1) (3 g) put into the reactor, and heated with electric furnace while flowing nitrogen (160 mL/min) and steam (1 mL/min) warmed by heater. After heating to setting temperature (450 - 650 oC), tantalum condenser (3 g) was put into the reactor, heated for 5-10 min, and then cooled to room temperature to recover the reacted capacitor by filtration after treating with distilled water. At relatively low temperature (550 oC) heating for 10 min, mold resin can be decomposed by using steam gasification with mixed molten carbonate, in comparison with using pyrolysis and steam gasification without carbonate, and decomposition reaction occurred over 500 oC by using steam gasification with mixed carbonate. Recovery of tantalum parts from capacitor is successful using steam gasification with mixed molten carbonate at 530 oC for 5 min, due to the effective decomposition and removal of mold resin from capacitor. Furthermore, most halogen gas generated from decomposition of mold resin can be trapped in molten carbonate not to exhaust halogen gas. These results suggested that recovery process of tantalum parts from used condenser using steam gasification with mixed molten carbonate is expected as a feasible way to recycle the rare metal in electric equipment.

Jan 1, 2014

By Andries Van Wyk, Steven Bradshaw, Guven Akdogan, Jacques Eksteen, Cornelius Snyders, Cleophace Mpinga

"In order to exploit lower grade and complex platinum group metal resources, cheaper and more efficient alternatives to the conventional mill-float-smelt-refine route are being sought, particularly for resources’ in areas that are water-scarce and where electrification is costly and problematic. Leaching with cyanide is a promising process option and although recoveries are lower than in the conventional process routes, progress into the understanding of cyanide leaching of PGM containing ore and concentrate has been made. Research regarding the feasibility of upgrading the pregnant PGM leach solution using activated carbon has, however, been lacking and hence forms the focus of this paper. Bottle roll adsorption tests for dilute PGM solutions (0.15ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) onto granular activated carbon showed high rates within the first 60 minutes (giving more than 90% recovery of precious metals). Comparison of the Pt isotherm to Au isotherms from literature indicated a similar loading capacity, while that of Pd was found to be significantly lower. The effects of solution pH, temperature, base metal concentration, free cyanide concentration, thiocyanate concentration, initial PGM concentration and activated carbon concentration were investigated and are discussed. Elution of the Pt and Pd, with the AARL elution process, was found to be effective with recoveries of 95% after 5 bed volumes of eluant at the optimum pre-treatment concentrations and a temperature of 80°C. Temperature, NaCN and NaOH pre-treatment concentration and the ionic strength of the eluant were found to be the most important factors affecting elution while base metals concentration, acid-pre-treatment, carbon loading and thiocyanate concentrations to a lesser extent. Simplified combined flow sheets are suggested and the corresponding mass balances are compared."

Jan 1, 2014

By J. Drzymala

Ores and raw materials are subjected to mineral processing operations to increase the content of their useful components. Upgrading of these materials can proceed with different selectivity and therefore, there is a need to know and monitor the separation results of the process. The separation results can be evaluated using tables and graphs called upgrading curves. The course of lines in the upgrading curves is usually complex and depends on the graph type and process parameters. The Halbich grade vs. recovery plot is frequently used because is practical and it indicates several characteristic features of separation results. Separations by means of flotation of several different shale, dolomite and sandstone copper ores were performed along with determination of their mineral composition, copper content, liberation degree, and the maximum theoretical copper content in the first concentrate. These data, plotted as the Halbich upgrading curves, allowed to find other characteristic points such as practical maximum copper content in the first concentrate, maximum curvature coexisting with the liberation degree, maximum recovery of ore valuable components, and the slope the recovery-grade line at high recoveries as a measure of liberation. Correlations between theoretical and practical maximum copper contents in the first concentrate as well liberation degree and maximum curvature were also presented. They show that the ore type significantly influences the shape of the Halbich curve and its characteristic points.

Sep 1, 2012

By Henrique Kahn, Daniel Uliana, Carina Ulsen, Guilherme Nery

"Gold has been a material in high demand since the dawn of humanity. After hundreds of years of exploitation, the increasingly search for gold occurs in lower grade deposits with greater extraction difficulty. Therefore, for maximum efficiency, deep knowledge of the characteristics of these minerals and their associations is crucial, which is acquired through an accurate and rigorous routine of process mineralogy and batch extraction tests. The industrial gold process extraction occurs by gravity concentration, sulphides flotation and cyanidation. For gravity concentration, it is fundamental to establish the proportion of free or coarse gold grains and its association to heavy minerals; regarding flotation, the most relevant data are the proportion of gold associated to sulphides and their liberation by the surface area; for cyanidation, it is crucial to evaluate gold accessibility and the kinetics of leaching. Thus, the characterization of gold associations and liberation is vital to establish the plant design, to optimize operating plants and to reduce gold losses. Our aim is the characterization of gold occurrence in low-grade Brazilian deposits with complex mineralogical assemblages to support processing flowchart definition and to predict metallurgical recoveries. Gold distribution in light and heavy minerals was evaluated by heavy liquid separation and the occurrence of gold in free or locked particles was carried out on heavy products by SEM-based automated image analysis using the MLA system. All the products of heavy liquid separation were cyanidated in head samples with different milling conditions to evaluate the reaction kinetics and maximum recovery."

Jan 1, 2014

By A. A. Novoselov, U. Kelm

"Large volumes of mine tailings accumulated in surroundings of porphyry copper deposits represent a growing threat to environment. They contain significant concentrations of toxic metal and metalloids which can contaminate river runoff, ground waters or can be transported by wind. Both extreme pH of fluids in tailings impoundments and high surface areas of processed mineral grains provide their increased reactivity. As a result, during only a few decades, As, Cu, and Mo can be mobilized, redistributed through the tailing column and accumulated through post-deposition leaching, evaporation and contamination with natural fluids. Those processes are reflected in the forming of secondary minerals. Gypsum, Fe oxides/hydroxides, efflorescent salts and clay minerals are typical alteration products in tailings. Here we present the results of reactive transport simulations implemented on the base of PHREEQC and SUTRA codes. The one-dimension model emulates the mass balance between rainfall, evaporation and subsurface runoff, the kinetically- and thermodynamically-driven dissolution of tailing minerals, advective and diffusive transport of tailing fluids, and precipitation of secondary phases. A typical tailing column is composed of four unequal layers with predominance of (i) evaporation, (ii) secondary mineralization above, (iii) below water table, and (iv) near the bottom of dump. Those horizons are characterized by contrasting pH, chemical composition and bulk mineralization of pore fluids, distinct accessibility of atmospheric oxygen and, as a consequence, distinct intensity of sulfide oxidation. The modeling and its verification on Chilean tailings impoundments reveal the complexity and high rates of secondary mineralization. The accumulation of toxic alteration products is controlled by fluid transport through the tailing column induced by both rainfall/evaporation and exchange with subsurface runoff. The geochemical modeling is a powerful approach which allows comparing the processes in tailing deposits produced by distinct flotation regimes and providing the long-term predictions of their environmental impact as well as identifying sectors of tailings for possible re-processing."

Jan 1, 2018

By Xiao Jian Li, Dai Xiong Chen, Jian Wen Yang

In one kind of lead and zinc bearing polymetallic ore containing secondary copper, the characteristic of low sulfur, high zinc, and particularly the existing of secondary copper minerals can lead to lead concentrate with high content of zinc because the dissociation of Cu2+ in the grinding process may have an activation influence on sphalerite. Considering its process mineralogy analysis, a new process of seperation of lead and zinc has been put forward. The experiments focused on the analysis of the advantages and disadvantages of the inhibition effect of traditional adjustment reagent + zinc sulfate on activated sphalerite compared with new organic inhibitor, polysaccharide xanthate. According to the numerical calculation and test results, a reagent system of polysaccharide xanthates is developed, which has a good inhibition effect on Cu2+ activated zinc minerals, achieving high-efficiency separation of lead and zinc. A new reagent system and flotation process was developed under optimal conditions. Under the condition of the run-of-mine ore containing 2.37% Pb and 12.48% Zn, lead of 67.69% grade and lead concentrate with the recovery rate of 86.06%, zinc of 60.32% grade and zinc concentrate with the recovery rate of 96.15% were achieved.

Jan 1, 2014