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By Volker Vogt, Wolfgang Sand, Eberhard Gock

"It was discovered that the selective activity of bacteria during the extraction of raw material concentrates by means of flotation could also be achieved with extracellular polymeric substances (EPS) excreted by bacteria. EPS, which is extracted by means of centrifuging bacterial cultures, can help to significantly reduce the use of cyanides, approximately 200,000 t/a of which are used for ore dressing today.The bacterium used was Acidithiobacillus ferrooxidans. In order to identify the bandwidth of the oxidation activity, 20 bacterial strains of the strain collection of the University of Hamburg were attracted to iron(II) sulfate and pyrite under defined conditions. All strains oxidized iron(II) sulfate ten times faster than pyrite.EPS has so far been derived from four strains. In general, EPS extracts are divided into a hydrophilic and a hydrophobic fraction. The hydrophilic fraction is composed of e.g. fucose, rhamnose and glucose; fatty acids such as dodecanoic acid, hexadecanoic acid, octadecanoic acid and nonadecanoic acid were found in the hydrophobic fraction.Pure mineral phases and mineral mixtures were used for the flotation tests. As opposed to current knowledge, the results were reproducible with technical flotation machines."

Jan 1, 2003

By Bianca Foggiatto, Marko Hilden, Malcolm Powell

"Since the introduction of the concept of flexible circuits (Powell and Bye, 2009), it has been further developed and refined to the definition of ‚FlexiCircuits leverage ore variability to maximise resource utilisation?. The focus of flexible circuits is to investigate processing options that provide extra capacity through sophistication rather than scale. This requires a combination of smart ore characterisation, economic modelling and innovative processing plant design. Flexible circuit design can reduce energy requirements through gangue rejection or progressive ore upgrade; and increased robustness and controllability by leveraging off ore variation. Each rock type, as characterised through Geometallurgical ore modelling, may be processed more efficiently by individually optimising processing paths. The objective of FlexiCircuits is to transform the processing capability of comminution and concentrator plants - targeting step change in performance through integrating a range of interrelated improvement opportunities. Considerable effort has been applied to developing the modelling and simulations tools required to develop and demonstrate the potential of this concept. This paper presents a practical application as a test case. A realistic application of flexible circuits is provided through a conceptual circuit design of an iron ore processing plant. It is simulated as a multi-component feed with a range of new models in the researcher’s Model Developers’ Kit (MDK) to trial the ability of different circuit designs to respond to variable ore and quantifying the potential of these circuits to transform processing capability of variable ore feed. The outcomes of the simulations are presented and discussed, providing a practical demonstration of the level of modelling and simulation required and the potential of flexible circuit design."

Jan 1, 2014

By M. E. Holuszko

This paper reports the results of induction time measurements carried out on the products of film flotation of galena and sphalerite particles from three different size fractions (38~75µm; 75~150µm; 150~212µm). As expected, the tailings (sinking fraction) from film flotation at any particular surface tension, had always longer induction times than the concentrates (floating fraction), for both minerals. The difference between the induction times of film flotation concentrate and tailings could be as little as 2.5 ms and 5 ms, and as large as 6 ms and 10 ms. These differences can be related to the different hydrophobic characteristics of these fractions, as expressed by (?c) and composition of the particular film flotation product. In addition, the induction times of the larger particle size fraction were shown to be longer than for the corresponding smaller particle size fraction, even though the average ?c(degree of hydro-phobicity) of these fractions appears to be very similar. Desliming, Cu activation and collector addition to the sphalerite samples was shown to decrease the induction time values significantly.

Jan 1, 2014

By S. K. Chaurasiya

o meet the ever increasing demand of iron oxide feed stock for rapidly growing domestic steel industries and to effectively manage the depleting reserve of high grade lumpy iron ore, Pelletization of iron ore fines/slimes are expected to play a dominant role in the near future. Use of pellets will also enable the blast furnace operator to achieve higher levels of productivity with lowering of operating cost. The effective utilization of Iron Ore Slimes is important not only from the point of view of optimum utilization of Iron values in the mined ore but also for preventing environmental pollution. A significant amount of slime is being accumulated at the tailing dam of one of the iron ore mines and with the present scale of operation the tailing dam will be filled in another 10 years. Hence to increase the life of tailing dam and for better utilization of the iron values a study has been carried out for the suitability of pellet manufacturing with slimes and fines at our laboratory. The pelletization studies are aimed for optimization of various parameters for production of Blast furnace/ DR grade pellets from beneficiated slimes and Fines. This paper attempts to describe the production of blast furnace grade pellets from beneficiated slime and fines and its characterizations.

Sep 1, 2012

Datun Concentrator currently processes complex sulfide ores in Gejiu Municipality, Yunnan Province, China. The ore contains much higher arsenic than other ores. The run of mine ore is fed to the concentrator to recover copper and tin by bulk flotation and gravity concentration, and then the other sulphides, such as pyrite, arsenopyrite, etc. didn?t get utilized and are discarded as tailings due to the high arsenic content. In order to utilize the pyrites in the tailings, a series of tests have been conducted for finding the solution of arsenic removal from high arsenic-bearing pyrite concentrates through simple flotation process. By means of orthogonal experimental design, the optimized levels and main factors have been found out for the roughing stage. Through selection of the effective in-organic depressants for the arsenic-bearing minerals, the arsenic in the pyrite concentrate can be removed to meet the requirement of sulfuric acid plant (As%=0.5%) by the open flotation process, i.e., one-time roughing and two-time cleaning.

Jan 1, 2014

By Sergey Dyachenko

"Following the adopted strategy for making the production modern, efficient and environmental friendly the Company completed a stage of the integrated program aimed at reconfiguration of its processing capacity.Upgrade of the Talnakh Concentrator with commissioning of two start-up facilities (SF) allowed an increase of 30% in its ore processing capacity up to 10 mtpa. In addition to a new high-tech equipment installed, a new concentration process was adopted offering the main advantage of 25-30% reduction of sulfides in concentrate. New concentration technology enabled the total amount of produced nickel concentrates (from Norilsk and Talnakh Concentrators) to be processed at upgraded smelting facilities of Nadezhda Metallurgical Plant and allowed decommissioning of smelting capacities of Nickel Plant resulting in emissions reduction by 30%.Nornickel plans to boost the capacity of Talnakh Concentrator to 18 mtpa by 2022, after commissioning of the 3rd SF. This will provide a shorter route for ores transportation from Talnakh mines along with improvement of cost/performance ratio of ore processing through the usage of the modern equipment and optimized concentration flow scheme. Total capacity of Talnakh Concentrator will be sufficient to process ores from Talnakh deposits with planned upstream assets development taken into account. Volume of ore mined from Norilsk deposits to be processed at Norilsk Concentrator will be also increased.Upgrading the crushing section at Kola MMC Concentrator in 2015 provided finer particles of the crushed ore, resulting in 6.6% increase in specific capacity of ore mills as well as 1% higher recovery of non-ferrous metals due to improved liberation of ore minerals.In 2015-2017 the Company was actively engaged in optimization of existing process flow schemes and parameters of Kola MMC, new high-performance reagents were adopted for concentration process, namely, collectors, depressors, flocculants. These measures allowed the Concentrator to reduce its annual operating unit costs and ensure sustainable production of concentrate with the lower grade of the incoming feedstock.Launched in October 2017, Bystrinsky GOK’s Concentrator was 3D designed and received a range of advanced technological solutions.All design process procedures and technologies rolled-out at the Company’s concentrators were developed by Russian R&D institutes, with the key role of Gipronickel Institute, R&D Service of Kola MMC and Polar Division's in-house Engineering Support Centre."

Jan 1, 2018

By V. Panayotov, M. Panayotova

"The combined use of semiconductor properties and specific flotation characteristics of minerals under different conditions with external influences ensures a possibility for process control and management. This work presents the relations between the volumetric and surface characteristics of minerals and the minerals' flotation ability (flotability), as well as the possibility for the flotability purposeful change. Results from proprietary laboratory and industrial research are presented showing how controlled impacts on minerals and flotation pulp improve flotation technology. Such an approach reveals prospects for the creation of new technologies for the minerals' beneficiation.INTRODUCTIONThe decrease of the useful components content in the ores, the increasingly complex nature of the raw materials, the increasing energy consumption per the unit of production, and the need to solve the problems related to the environment pollution require solutions different than the existing classical ones. One of the ways to find such solutions is the detailed consideration of the fundamental properties of minerals and, in particular, of minerals having semiconductor properties. The studies of Plaksin et al. (1968), Chanturia and Shafeev (1977), Chanturia and Vigdergauz (2008), Carta et al. (1973), Hoberg and Shneider (1975), Rao et al. (1992) have given an idea of the energy state of the minerals, their flotation ability, and the ways in which this ability can be changed in one or the other direction. The main line in these works is the study and use of the relationship between bulk and flotation properties of minerals. To improve the efficiency of the process, it is also necessary to consider the relationship between the surface properties of the minerals, especially minerals-semiconductors, and their flotation ability.THEORETICAL BACKGROUND IN BRIEFA quantitative estimation of energy changes in a solid phase in the process of flotation may be made by taking in account the changes in the Fermi level. Its position in the forbidden band is an indicator about the direction and the intensity of electron exchange between solid and liquid phases. The Fermi level energy EF enables the estimation of flotability, intensity of needed external impact before flotation, as well as efficiency of the process going on. Quantitative estimation of these processes can be made by means of the flotability coefficient Kf."

Jan 1, 2018

By J. Qiu

By means of natural sedimentation, two different bentonite samples from Shandong province were purified, this paper studies the Hydro-properties of the two purified montmorillonite samples. Firstly, the layer charge of two purified montmorillonite samples were calculated by crystal structure formula reckon method and general hydro-properties were also measured. The research results showed that the layer charge of montmorillonite correlated well with its hydro-properties: mont-morillonite with lower layer charge had better hydro-properties, such as Mont-1, which had higher swelling volume and gelling value with lower CEC; while, montmorillonite with higher layer charge had worse hydro-properties, such as Mont-2, which had lower swell volume and gelling value with higher CEC; it proves that the hydro-properties of montmorillonite depends on its layer charge characteristics, layer charge characteristic is the inherent factors deciding the hydro-properties of montmorillonite, montmorillonite with lower layer charge has better hydro-properties than the one with higher layer charge. In this paper, the relation between the medium condition and colloid performance of Mont-1 are also studied. The results show that the hydro-properties of Mont-1 could be changed by changing slurry concentration (w/w) and shear rate or adding certain amounts of inorganic cation electrolytes, dispersants and surfactants. The viscosity of montmorillonite slurry could be enhanced by increasing slurry concentration,adding univalentcation electrolytes (less than 4% w/w) or proper amounts of dispersants and surfactants (less than critical micelle concentration); The slurry viscosity could be reduced by decreasing slurry concentration, increasing shear rate, adding proper bivalent (more than 4% w/w) cation electrolytes or proper quantities of dispersants and surfactants (more than critical micelle concentration).

Jan 1, 2014

By Massimiliano Zanin, William Skinner, Keith Quast

With the scarcity of fresh potable water on mining sites, particularly those in arid and remote regions, the use of sea water is being contemplated and actually used at a number of mineral concentrators worldwide. The use of sea water, with its associated high dissolved solids content and ionic strength will affect all aspects of processing (e.g. frothing and froth stability, buffering capacity for pH control, solubility of minerals and corrosion of media and equipment). Selective depression of pyrite is more difficult in sea water due to the increased lime addition to achieve a high pH. This results in a reduction in molybdenite recovery. The use of grinding media with various chromium contents and its effect on subsequent Cu and Mo flotation has been investigated in the current study, with both grinding and flotation testing conducted in artificial sea water. Pulp chemistry (pH, Eh and DO) have been logged during grinding, and flotation testing was conducted on subsequent slurries. The flotation results show that the system is remarkably robust and able to cope with wide ranges of pulp chemistry parameters. The effects of artificial sea water on the surfaces of minerals during grinding have been examined using X-Ray Photoelectron Spectroscopy

Jan 1, 2014

By X. Q. Cui

The surficial collapse pits of the mining areas are continuously spreading in Beiminghe iron mine of Hebei Province as a result of the exploitation, which has done a lot of damage to the circumjacent ecological environment of the mine. It is a new path to handle the mine tailings at the present time that the thickened tailings are used to backfill the collapse pits, in which way the problems of the surficial collapse and the nowhere discharge of the tailings are both solved, and the rational utilization of the mine tailings and the clean production of the mine enterprise are realized. The?200 mesh content of the tailings of Beiminghe iron mine is 76.87%, and?325 mesh content is 63.50%. Semi-industrial dehydration experiments to the tailings have been done using the hydro-cyclone classified thickening process. The results show that when FX125 hydrocyclone is adopted, the concentration of underflow can achieve 73.31%, and the yield ratio is 61.78%; when FX150 hydrocyclone is adopted, the concentration of underflow is 70.57%, and the yield ratio is 54.31%, which indicate that the minor diameter hydrocyclone is propitious to improve the yield ratio of the underflow. The semi-industrial dehydration system of hydrocyclone classified thickening process is com-posed of FX125 hydrocyclone, D3600 high-efficient thickener and D2000 thickening bucket. The capacity to tailings disposal can achieve 3.07t/h and the tailings can be thickened from 28.86% to 62.45%. Compared with the traditional thickening-filtrating process and the total tailings directly filtrating process, the hydrocyclone classified thickening process has the merits of simple flow and high thickening efficiency, so it is easy to be realized in the mine.

Jan 1, 2014

By Paul W. Weiblen, Louis J. Cabri, Rolando Lastra

"Preliminary tests were done to determine whether comminution by electric-pulse disaggregation, or E-PD (cf. Rudashevsky et al; 1995), was more effective than using conventional crushing for Merensky Reef ore. A hand sample of the Merensky Reef was sawn in two: then one sub-sample was comminuted to .2 mm using E-PD at the University of Minnesota, and the other sub-sample was crushed to .2 mm using a conventional jaw crusher at CANMET.The products of the electric-pulse disaggregation and jaw crusher were fractionated by sieving and by a separation using a heavy liquid with a specific gravity of 3.3, because the proportion of platinum-group minerals (PGM) and sulphides to silicate minerals is very low. Thus, four mineral separates were produced: .2000 + 833 µm, -833 +208 µm, -208-µm float and -208-µm sink. All the mineral separates were studied by image analysis (Lastra et al; 1998). The main objective was to determine the liberation of gangue (silicate minerals), chromite, pyrrhotite, chalcopyrite, pentlandite and PGM. In the case of the PGM, a specific image analysis program was written to search and measure these minerals.The results show that the liberation obtained for gangue was similar (~99%) using either method of comminution. However, the liberation obtained for chromite (~89% vs. ~38%), pentlandite (~50% vs. 1%), pyrrhotite (~56% vs. ~38%), and PGM (~56% vs. ~1%) by E-PD was higher than that obtained by conventional jaw crusher, whereas the liberation obtained for chalcopyrite (~20% vs. ~71%) by E-PD was lower. Nevertheless, the image analysis of the products also showed that the PGM are strongly associated with pentlandite. Thus, for the Merensky Reef, liberation of pentlandite from the gangue minerals and chromite is important to recover more of the PGM. This maybe be significant because, in addition to increased recovery of platinum-group minerals (PGM), Merensky Reef pentlandite also contains significant quantities of valuable platinum-group elements like Pd and Rh (Cabri, 1981; Cabri 1988, Kinloch 1982, Peyerl 1983). Hence, the results indicate that for the Merensky Reef, electric-pulse disaggregation would represent a better comminution operation than a conventional jaw crusher would. In addition, the greatly improved liberation for chromite may find application for the PGM-rich UG2 chromitite."

Jan 1, 2003

By G. Venkateswara Rao

The jigging of ferrous ore to produce higher-grade products has been practiced for many decades. This is due to easy separation, a beneficial trade- off between operating cost and reduced yield relative to Dense Media Separation (DMS). Jigging becomes prominent for beneficiation of iron ores in the coarser size range. At present drive is towards the use of under bed air pulsed jigs for the beneficiation of ferrous ores. The main advantage is that the under bed air pulsed jigs are capable of generating the large pulse of amplitudes required to fluidize a deep bed of heavy ores particularly lump iron ore up to 40mm size. The major jig parameters effecting the jigging operation are bed height, shape of the pulse, residence time, operating pressure, valve cycle time and water flow rate. With the pulse shape set correctly for optimum stratification rate, even it is still necessary to provide enough residence time, to ensure the difficult material will take time to migrate to the expected layer in the bed. In order to find the Jig Stratification Index (JIS) parameters like bed height, operating pressure, water flow rate, cycle valve time and shape of the pulse were optimized first by conducting various tests. Typical Iron ore samples from Odisha (both lump and fines) were subjected to stratification studies at residence time of 1, 5 and 15 minutes. Jig Stratification Index (JSI) for both lump (0.30) and fines (0.20) were determined by using APIC Jig. The maximum possible JSI was calculated by using heavy liquid separation test (0.42 for lump and 0.24 for fines). It is found that the jig bed JSI is less than the Heavy liquid JSI for both lump and fines. The ratio of Jig bed JSI to the heavy liquid JSI is 0.83 for lump and 0.71 for fines. The JSI and ratio of Jig bed JSI to Heavy liquid JSI are low for fines due to fluid turbulences causing some degree of remixing in the jig bed. The fluid turbulences are more for fines than lump, hence jigging of fines is difficult and challenging. Keywords: sub grade iron ore, gravity separation, jigging, apic jig, stratification, residence time, jig stratification index

Sep 1, 2012

By I. S. M. K. Ilankoon

In heap leaching the transport of the acid from the drippers to the surface of the ore particles is a major factor in the overall performance of a heap. This flow behavior is complex as the flow is unsaturated and occurs along a tortuous set of inter-particle channels and connections. Previous modeling of this system has used equations from oil and ground water flow to model these systems, but the applicability of these models with the larger particles found in typical heaps is suspect as these systems are not necessarily capillary dominated. In particular, as the characteristic particle size goes from below to above a few centimeters, the flow changes from capillary to gravity dominated. This means that typical heap leaching heaps cover this interesting, but complex, transitional fluid flow regime. In this paper a set of experimental studies of this flow, including PEPT (positron emission particle tracking) based tracer experiments, highly accurate liquid holdup measurements and axial dispersion experiments using salt tracers will be presented. In this study, flow through mono-dispersed particle beds was carried out. In particular, the hysteresis in the liquid holdup as the liquid flow rate into the particle bed is varied is investigated, since this hysteresis means that the relationship between flow rate and holdup is history dependent, an effect not included in models currently used to describe fluid flow in heaps. A theoretical model that describes this hysteresis will also be presented. Keywords: heap leaching, hydrometallurgy, modeling

Sep 1, 2012

By X. J. Lu

Purified Na-montmorillonite samples were used as the starting materials to prepare organically modified montmorillonites (OM), and a series of OM samples were prepared by intercalation of al-kyl quaternary ammoniums with different alkyl chain length. The interlayer spacing (d001) of the OM was determined by small angle X-ray diffraction and its gelating performance was characterized by measuring the viscosity of OM/dimethylbenzene mixture. The effects of alkyl chain length, dosage of alkyl ammonium, intercalation duration and layer charge of the starting material on the OM structure and gelating properties were investigated. According to the results, the adsorption quantity of the alkyl ammonium is dependent on the hydrocarbon chain length, the dosage of the alkyl ammonium and the retention time. The adsorption quantity of the alkyl ammonium increases with the chain length and the dosage, and extra adsorption more than the CEC of the montmorillonite sample was observed under the dosages of more than 1.3 CEC. The interlayer spacing (d001) of the OM shows a dynamic variation with the dosage and the retention time, and super interlayer spacings greater than the length of the alkyl ammonium were observed under larger dosages and shorter retention times. However, the gelating performance of OM does not follow the variations of the adsorption quantity of alkyl ammonium, an optimum viscosity value of OM/ dimethylbenzene gel was observed with the moderate adsorption of the alkyl ammoniums. Furthermore, the layer charge plays an important role on the gelating performance of OM. The OM synthesized by the starting material with lower layer charge shows better gelating performance in the dimethylbenzene solution.

Jan 1, 2014

By Ji Hoe Kwon

Hindered-settling column process has been used for the separation of mineral particles for many years. In this study, a model based on DEM (Discrete Element Method) was used to simulate the movements of particles in a settling column separation process. DEM model is capable of describing the motion of particles and calculating the impact forces between particle and particle, and particle and wall contact under various operating conditions. Drag force, rotation induced Magnus lift force, contact force and the gravitational force acting on individual particles were considered for establishing the mathematic models. The overall motion of the particles in water is satisfactorily simulated by the DEM, and the result shows good agreements with the result of lap-scale experiment.

Jan 1, 2014

By Sanjay Chaudhuri, V. K. Kalyani, Pradeep Kumar Singh, T. Gouri Charan

"Indian coal industry is the world's third largest in terms of production and fourth largest in terms of proven coal resources. Indian coal deposits are generally of high ash content varying from 24 to 50%. The coking coal reserves of India constitute about 12% of the total coal inventory, and the coals are washed in washeries, before being used for metallurgical purposes. The processes used for washing coking coal is Jigs, Heavy medium bath and Cyclones for the sizes upto 0.5mm, while the coal fines are washed in spirals and conventional flotation cells. Extensive studies were carried out for understanding the performance of an operating conventional flotation plant. The performance studies revealed that appreciable quantity of clean coal is being lost in the tailings due to varied reasons and the required quantity and quality was not achieved. In this study, laboratory Flotation experiments were carried out to examine the cleaning characteristics of the said tailing and to determine the effective process parameters for recovery of clean coal at desired ash level ( 16-17%). Response Surface Methodology was applied to investigate the operating conditions of the Froth Flotation for modeling and optimization. Primary study reflects that there is a possibility to recover clean coal at 16-17% ash level with a yield of about 60-70% from that Flotation tailing of feed ash about 28%.INTRODUCTIONMost of the Indian coking coals are difficult in cleaning characteristics and high ash content due to its drift origin and its age of formation for more than 225 million years. Indian coking coal reserve is limited about 12% of total coal reserve. The minerals are homogeneously mixed with the coal macerals. The open cast mining practice and mechanized mining methods are being adopted to meet the increasing demands of coals resulting in generation of more coal fines and subsequently the quality is deteriorated. Indian good quality coking coal reserves of higher seams are fast depleting and hence coking coals of difficult cleaning characteristics of lower seams (LVC) are being now explored. Due to increased mechanization of coal mines to cope up the increased demand and followed by size reduction of lower seam coals in search of better liberation , the coal fines are increasing by leaps and bounds. The processes used for washing coking coal is Jigs, Heavy medium bath and Cyclones for the sizes upto 0.5mm, while the coal fines are washed in spirals and conventional flotation cells."

Jan 1, 2018

By S. Narra, M. Nelles, I. Eickhoff, S. Teitge

"The aim of the research is to develop a holistic process flow for the recycling of glass fibres from glass reinforced plastics (GRP) and carbon fibres from carbon fibre reinforced plastics (CFRP), wherein the dissolution of the fibre epoxy resin matrix, separation of fibre fractions and their renewed material use is intended. In clear distinction to the previous research and development projects, the aim here is to recycle complex composite structures such as dismantled/disused wind turbine rotor blades and end-of-life composite wastes. In the course of the study, mechanical, hydrothermal and thermal processes and their combined procedures will be developed. As the fibre length is a decisive quality criterion in the recycling of composite materials, the further focus of the study will be the development of upstream and downstream material processing, in which the fibres are retained in their original form. The evaluation of the recycled fibres obtained is based on the elemental composition, measurement and morphological evaluation of individual filaments by scanning electron microscope (SEM), micro tensile tests on single fibres and their comparison to virgin fibres. The resulting process water is analysed by gas chromatography and mass spectroscopy (GC-MS) and a potential recirculation is determined. In cooperation with companies from the composite processing industry as well as recycling companies, a return of the recycled fibres to the known manufacturing process will be examined and an energetic and economic evaluation of the overall process will be carried out. Ambitious aim of the study is to achieve an actual recycling instead of the present downcycling or the energetic utilization. INTRODUCTION As global warming increases, so does the awareness of consumption and production of energy. To counteract the effects of global warming, renewable energy has been increasingly used during the last two decades, not only in Germany, but worldwide. Both, hydropower and wind energy, hereby play a fundamental role. After the end of their useful life of 20 to 30 years, the wind turbines (WTs) are being dismantled. Due to their foundations and tower segments, their recycling rate hereby exceeds 90% by mass. So far, the resulting rotor blade waste played a minor role accounting for only 2 - 3 weight-% of the total plant. Rotor blades of modern wind turbines are made of glass and carbon fibers, which are embedded in an epoxy or polyester resin matrix, balsa wood, PU or PET foams as fillers as well as various paints and coatings. These wastes currently end up in waste incineration or are sold to non-European countries."

Jan 1, 2018

By M. Pelser, C Aldrich

"The presence of calcium and magnesium in the hydrometallurgical processing of base metals, results in a number of process difficulties. These problems range from the contamination of the final product (where the final product is a precipitate) to high energy consumptions and large bleed streams during electrowinning. Calcium poses an additional problem in sulphate solutions owing to the low solubility of its sulphate salts. This can easily lead to a process stream that is supersaturated with calcium sulphate, resulting in unwanted solids formation within the process equipment.Several processes are reviewed for the control of calcium and magnesium. Of these, fluoride precipitation was selected for experimental investigation. This method involves the addition of a soluble fluoride to precipitate CaF2 and MgF2. The experiments showed high selectivity for calcium and magnesium over the base metals. The experiments also showed magnesium precipitation to dominate for calcium to magnesium molar ratios greater than 1:3.To avoid the domination of magnesium precipitation, a flow sheet is proposed whereby only a portion of the base metal stream is subjected to fluoride precipitation. For the precipitation, a 10% excess of ammonium fluoride is used to remove the maximum amount of calcium and magnesium. After precipitation and solid-liquid separation the split-stream is returned to reduce the overall calcium and magnesium concentration of the base metal stream."

Jan 1, 2003

By Peter Riccio

Oxiana Sepon?s mineral processing facility in south central Laos produces copper cathode using leach-autoclave-SX/EW flotation technology. Pyrite recovery in the flotation circuit is critical to the operation, as it is used to generate acid for the leach circuit. However, low pyrite recovery has been an ongoing challenge in the flotation circuit. Tailings characterization work done by Ian Wark Research Institute showed that the pyrite losses to the tail are made up of a combination of coarse liberated particles and finer particles that have been coated by clay fines. In December of 2005, a joint Cytec-Oxiana technical program was initiated to address the pyrite recovery issue. A series of diagnostic tests were performed in the Cytec Stamford Research Facility using synthetic plant water showing that the collector was precipitating as a metal salt, and was un-available for mineral attachment. The tests also identified several collector chemistries that would likely be robust in the Sepon low pH, high dissolved metal ion environment, and will not complex with ferric, ferrous, or copper in solution. With the support of the Sepon on-site engineers, an extensive, successful laboratory program was completed, which then was followed by on plant testing that showed a step wise improvement in pyrite recovery.

Jan 1, 2014

By S. Sarioglan

The bleaching of edible oils, industrial oils, and some chemicals may be achieved using natural and acid-activated clays. These materials remove impurities and pigments from the oils. In this work, a bentonite clay from Turkey (Somas bentonite) was activated with different concentration of H2SO4 and HCl at 70~90°C and 5~8 hours. Under these conditions several cations were removed from natural bentonite (Al, Mg, and Fe) and DTA-TGA, FT-IR curves of the solids obtained after acid treatment were examined. Treatment time and acid concentration increased the degree of destruction of the bentonite structure which was determined by ICP. Activated samples were tested in order to verify their capacity to bleach soybean oil and compared to standard commercial bleaching clays. The experimental results indicate that treated samples with H2SO4 have the same efficient in bleaching crude soybean oil with the standards and treated sample with HCl is more efficient in bleaching than the commercial products.

Jan 1, 2014