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By Z. M. Dai

Microorganisms in AMD (Acid Mine Drainage) were enriched in 9K culture medium. The enrichment was applied to leach copper pyrite after the microbial community structure and metabolism was stable. Before and after bioleaching, the microbial DNA was extracted and applied to RFLP (restricted fragment length polymorphism) analysis to demonstrate the relationship between the leaching efficiency and the change of microbial community. Atomic absorption spectrometry results showed that when concentration of the pulp was 10% and pH were 1.5, 2.0 and 2.5, the leaching rate were 56%, 57% and 34% on the 18th day respectively. These results indicated that the rise of pH resulted in the decrease of leaching rate. In lower pH condition, the growth of microbe was faster: when pH was 1.5, the microbial cell number reached to 1.4×107cells/mL on the 9th day; while pH was 2.5, the microbial cell number decreased to 4×106cells/mL. The analysis of microbial community structure showed that Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans were dominant species before bioleaching (account for 43% and 32% respectively). And after bioleaching, these two species were still dominant when the initial bioleaching pH were1.5 and 2.0. While the initial bioleaching pH was 2.5, the proportion of these two species decreased. These results demonstrated that the initial bioleaching pH would affect the microbial community structure in bioleaching system at room temperature, and this affect could lead to different copper pyrites bioleaching efficiency.

Jan 1, 2014

By John C. Gathje, Rick Moritz, Wilhelm de Beer

"Froth flotation has a long history of success for the recovery and concentration of a wide variety of minerals of commercial interest. Both the art and science of flotation have progressed greatly, and as our knowledge has increased so has our ability to improve mineral separations and recoveries.One area of interest in recent years has been the flotation of refractory gold ores to recover the gold-bearing sulfides. In many instances, the use of conventional air flotation to concentrate these values has achieved only limited success. However, as a result of intensive research, Newmont Mining has expanded the boundaries of flotation, and it can now be used to successfully treat many gold-bearing sulfide ores as well as platinum and palladium ores. This has been achieved through the use of the N2TEC technology, which utilizes nitrogen as an inert gas in the flotation process.Laboratory and pilot plant investigations and a commercial plant have proven its worth. Compared to air, the patented N2TEC process has increased the gold recoveries of many ores by 5 to 15 percentage points, and improvements of an even greater magnitude have been observed. This paper describes the process development for the flotation plant now being operated at Newmont’s Lone Tree Mine located in Nevada, as well as development work that was done on ores from their Twin Creeks Mine also located in Nevada."

Jan 1, 2003

By J. E. Gebhardt

Progress is reported on capturing the effects of gangue chemistry in the context of a comprehensive stockpile heap leach model for leaching copper sulfide ores, employing leading edge computational fluid dynamics (CFD) technology. The stockpile is a complex multi-phase process, comprising of a solid porous media, with complex fluid flow, gas and liquid phases, competing solid-liquid reactions, dissolution of minerals and transport through the heap. The model accounts for many of the challenging physical and chemical features of the heap, including transport and reactions kinetics for the important copper and iron sulfide minerals, ferrous oxidation, bacterial effects, thermal energy, acid and sulfate balances. In this contribution, the model has been extended to incorporate dissolution of various species from gangue reactions and precipitation of hydronium and potassium jarosite, ferric hydroxide, alunite, and gypsum. The effect of aeration on the simulation of a copper sulfide heap leach is provided as an example.

Sep 1, 2012

By B. Rai

Aluminum is produced by the Hall-Héroult process, which involves passing a current through a molten mixture of alumina dissolved in cryolite (Na3AlF6) to reduce the alumina to aluminum. This process occurs in an electrolytic cell comprising a steel shell lined with a carbon cathode and refractory bricks. After a certain period of operation, the carbon cathode deteriorates and is removed from the cell along with the refractory bricks. These removed materials are referred to as spent pot lining or ?SPL?. Typically, 30 Kg of SPL waste is generated for every ton of Aluminum produced. Globally aluminum smelters produce more than 500,000 tons of SPL each year. Even though SPL has a high fuel value (8000 to 9000 BTU/lb) and contains valuable metals, it is classified as a hazardous material due to its cyanide content and leachable fluorides. Various disposal/recycle techniques have been developed over the years for SPL but none of them is satisfactory. Thus, large quantities of SPL are still being dumped in landfills. In some countries, even the land filling of SPL is not permitted. The safe disposal of SPL thus remains a challenging problem to the aluminum industry and the search continues to find methods of converting SPL into a non-hazardous waste and/or recovering the valuable materials contained in the SPL. We have developed a process to produce hydraulic setting cements (eco-cement) containing a novel fluoride rich cementitious phase, from SPL by an energy efficient, low temperature clinkering route. A raw mix blend of SPL, lime/limestone, calcium sulfate and tailings sands based on a set of design criteria developed by us, is clinkered in a two stage process; 2 hours soak at 800 °C followed by clinkering at 1000 °C for another 2 hours, to produce a soft clinker. The SPL eco-cement is made by grinding the clinker to a fineness of 5000 cm2/g Blaine with 1% by weight borax as a set retarder. A good quality cement having as high as 20 % by weight of SPL in the raw mix (28 % by weight in the cement clinker) is thus produced. The physical properties of the SPL cements are found to be comparable to the Indian standard (IS) specifications for Ordinary Portland Cements (OPC). We have produced the cement in a few Kg batches and tested the reproducibility of results from batch to batch for further scale up. Once commercialized, this process has a potential of converting SPL into value-added cement products. Keywords: cement, spent pot lining, clinkering, fluoride, aluminum, ordinary portland cements

Sep 1, 2012

By T. S. Qiu

In view of the bad effect that Na-bentonite direct adsorb Pb2+-containing wastewater, this article has carried out two kinds modification treatment on Na-bentonite: the direct microwave radiation modification and microwave radiation organic modification by adding quaternary ammonium salt?cetyltrimethylammonium bromide,and analysis the main influencing factors of the modification effect. In static conditions, preparing Pb2+-containing wastewater as the research object, it has respectively studied the effects of Na-bentonite, microwave soil of direct microwave modification and microwave soil of organic modification on the process of adsorption Pb2+, and discusses the effects of pH value, temperature, adsorbent dosage, stirring time on the adsorption Pb2+ in wastewater by modified bentonite, at the same time it does a verification test to the practical Pb2+-containing wastewater. Comparison the effects of adsorption Pb2+ in wastewater, the results show that organic modified microwave bentonite is obviously better than direct microwave modified bentonite and Na-bentonite, and can make 6 mg/L Pb2+-containing wastewater meet the national discharge standards. Through scanning electron microscope, the result of test is that organic modified microwave bentonite is the cause of improving adsorption Pb2+ in wastewater. Preparing modified bentonite by microwave heating will not only shorten the response time, reduce energy consumption and work-load, but also modified effect is good.

Jan 1, 2014

By Alexsandro Berger

Many thickener operations continue to be constrained by their ability to process consolidated underflows with high yield stress and associated rheological characteristics. To maximise separation efficiencies within a thickener operation the use of both engineering and reagents are always considered. BASF is developing a Novel Flocculant Technology (NFT), which combines both of these aspects to enhance the performance of the thickener operation, improving the areas of pumping efficiency, underflow density and throughput. The development progression through stages of laboratory scale batch test work to pilot scale dynamic testing has demonstrated the ability of BASF NFT to maintain effective flocculation performance whilst increasing the rate of underflow consolidation, and significantly reducing the associated underflow yield stress of the treated material. This paper will present application data through full scale dynamic testing conducted on a granite washing circuit to demonstrate the performance benefits that NFT offers to a thickener operation. Compared to the conventional flocculant treatment, within the operation parameters and conditions employed during the full scale trials, the NFT produced a reduction in underflow rheology (yield stress) of around 45 % relative to a given solids and improved the underflow consolidation by providing at least 20% relative higher underflow solids loading than the upper limit of the given typical thickener operation. Keywords: flocculation, thickener operation, rheology, yield stress, underflow density, throughput, slump test

Sep 1, 2012

By M. Ito

Cobalt-rich ferromanganese crust and nodule ores from seamount areas contain volcanic and sedimentary rocks as substrate or nuclei and these ores require mineral processing to remove the substrate/nuclei rock before smelting. This paper reviews the results of jig separation and air table treatment for the coarse fraction and flotation and hybrid jigging for the fine fraction. Using these techniques substrate/nuclei rock was removed from the cobalt-rich ferromanganese oxide components. The mineralogical properties and metallurgical treatment methods including hydrometallurgical treatment of low grade ore is also reviewed.

Sep 1, 2012

By Irena Grigorova, Tashka Ignatova, Ivan Nishkov, Andrian Valchev

"Feldspars used by ceramic and glass industries as fluxing agents are mainly obtained from high quality feldspar deposits. The demand for feldspar as raw material for industrial applications especially in ceramic manufactures is continuously increasing. However, due to the depletion of those deposits, the research activities related to the recovery of feldspar from the lower grade feldspar deposits and feldspar bearing rocks such as pegmatite, granite, arkosic sandstone and syenite have been intensified in the last two decade. In Bulgaria, the main deposit of arkosic sandstone is located in the area of Shumen town, NE Bulgaria. In Srednya deposit arkosic sandstones are found in Upper Cretaceous sediments (Santonian). In this formation, there are two major industrial minerals - feldspar and quartz. They may be of economic value and possibly suitable for commercial uses. The main purpose of the present study was to investigate the beneficiation and upgrading processes of Srednya deposit arkosic sandstones. In a laboratory scale it was studied the possibility to obtain the feldspar concentrate and quartz sand from arkosic sandstones. Particle size distribution, chemical and mineralogical compositions of quartz-feldspar sands were determined. The bench-scale tests using the KOALIN AD laboratory experimental facilities were conducted. Many processing techniques were tested: disintegration, washing, sizing, carbonate flotation and feldspar flotation. The experimental results show that there are possibilities to obtain the silica sand with low content of Fe2O3 - below 0.02 % and potassium feldspar with content of K2O > 14 %. A new technology for recovery of feldspar and silica sand from arkosic sandstone was developed."

Jan 1, 2014

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

"Froth structure and stability are known to play an important role in determining flotation recovery and selectivity. An industrial sampling campaign was performed to develop a clearer understanding of the effect of flotation variables on froth stability and the role played by the resulting stability on flotation performance.Froth stability was estimated as the fraction of bubbles bursting on the surface of the froth through image analysis and the solids loading on the bubbles at the top surface. It was generally found that high air flowrates resulted in a drop of froth stability showed by a drop in the fraction of air overflowing and a decrease in the solids loading and simultaneously produced low copper recoveries and low concentrate grades. Deep froths only allowed a small fraction of air to overflow and consequently produced low recoveries. An increase from a standard to high frother dosage did not result in a larger fraction of air overflowing, hence producing low recoveries. Likewise, low frother addition only allows low recoveries because the resulting unstable froth cannot support itself. Low aeration was found to be preferential as it allowed high particle loading, therefore high bubble stabilisation, and low gangue entrainment, resulting in the highest flotation performance.Additional laboratory tests were performed to introduce a new stability parameter and to give a clearer understanding of the effect of flotation variables on froth stability. The results confirmed some of the observations made on the plant."

Jan 1, 2003

By Morin D. H., Battaglia-Brunet F., D'Hugues P.

"In the mineral-processing field, bioleaching of metal sulphide concentrates is currently operated in very large mechanically agitated tanks. Such bioreactors have considerable requirements in terms of power consumption for mixing, aeration and heat transfer. The use of slurry bubble column, where the particles are suspended by gas motion as well as by liquid upward flow, could be an alternative to achieve bioleaching in more economical conditions. In order to compare these two techniques, a unit of stirred reactors in cascade and a bubble column were comparatively operated at laboratory scale in the bioleaching of a pyrite concentrate. For both pieces of equipment, experiments were performed not only in batch mode but also in continuous conditions.Bubble column performances were significantly affected by unpredictable technical difficulties met to maintain continuous feeding in the bubble column and by a significant settling of the heavy solid particles. Nonetheless, theoretical kinetic data, extrapolated from results in batch conditions, could be compared to those obtained in continuous tests, in bubble column and in mechanically agitated reactors. These kinetic data were used to evaluate the influence of reactor design and configuration choice on bioleaching performances."

Jan 1, 2003

By Magnus Evertsson, Rebecka Stomvall, Josefine Berntsson

"Understanding the effect of particle shape on dry rheology is considered to be an important aspect in order to replace natural sand used in concrete with manufactured sand. Crushed particles from solid rock are normally less rounded and have less equally shaped dimensions compared to natural sand. Thus, the flowability and workability of the concrete will be different. In previous research, it has been demonstrated how different crushing techniques affects the shape of the particles. In many cases it is believed that Vertical Shaft Impact (VSI) technology is a way forward to replace natural sand. To be able to study the effect of VSI at the smaller fractions (63-2000 µm) sufficient measurements methods to determine particle shape are required. Optical tools to analyze the aggregates would make it possible to study a large amount of particles at small fractions. The determination of particle shape of aggregates is challenging since the shape is highly irregular and the size span of particles are very large. This study aim to evaluate one of the available optical tools, the Camsizer, for digital imaging determination of shape and size distribution. The available default shape parameters of the Camsizer are studied to understand the meaning of the parameters and their suitability for determining the quality of manufactured sand. To evaluate the capacity to determine particle shape, tests are made with 35 different materials. The results are compared with the dry rheology measured with the standardized "flow cone" test. Dependence has been previously proven between particle shape and the mass flow rate in the cone. Three different shape parameters, aspect ratio, sphericity and symmetry, are studied with the Camsizer and the results are compared with the mass flow rates in the cone. The results indicate a strong linear relationship between the optical parameters and the flow cone test."

Jan 1, 2014

By T. J. Chen

Stone coal containing vanadium is an important vanadium resource in China. Roasting and oxidation of vanadium is the foundation for extracting vanadium from stone coal. This article takes stone coal vanadium ore in Tongshan of Hubei Province as research target to conduct oxidation roasting test on it by using a self-developed low-sodium compound additive and a new optimized technology. Firstly, use potentiometric titration, X diffraction, energy spectrum and electron probe to study valence change, occurrence and phase transition of vanadium during oxidation roasting process. On this basis, primary work is done on oxidation kinetics of vanadium by exploring the steps that control reaction rate during vanadium oxidation process and determining the related dynamic parameter ? apparent activation energy. The study shows that occurrence of vanadium in stone coal of Tongshan is mainly in illite, and that the result of phase transition in roasting process is disappearance of illite containing vanadium, formation of soluble vanadate and potassium feldspar, albite. It further demonstrates that oxidation process of vanadium is step by step (V(?)? V(?)? V(?)), and its oxidation reaction is controlled by diffusion kinetics whose dynamic apparent activation energy is E1=81.19kJ.mol-1.

Jan 1, 2014

By Kevin Galvin, Simon Iveson

Fine particles are the most valuable because they are the most liberated. However, they are also the most expensive and difficult to recover and concentrate. The Reflux Classifier is a novel invention that combines many of the virtues of existing fine particle separation technologies in a way that provides profound synergies. Multiple parallel narrow channels create a laminar-shear separation zone. The laminar flow provides a well-defined velocity gradient that exposes particles on the wall to a conveying velocity that is approximately proportional to their size, thus reducing the dependence of elutriation velocity on particle size. The high shear rate in these channels generates a hydrodynamic lift force that selectively lifts low-density particles off the channel wall and thus causes them to be preferentially conveyed out in the overflow. Particles that are not elutriated slide back down into the mixing reflux zone beneath the inclined channels which gives them multiple opportunities to re-enter the channels. The resultant suspension of both coarse and fine high-density particles in the fluidized bed zone at the base of the unit generates a strong autogenous dense medium that helps to direct large low-density particles back up to the overflow. The fluidization water also simultaneously de-slimes the high density underflow product. When placed in a centrifuge, the benefits of these features multiply with the improvements in capacity and selectivity that arise from high G-forces. When inverted, these features can be used to perform flotation well beyond the conventional flooding limit. Hence this invention platform has the potential to dramatically improve both gravity and flotation separation performance across the minerals processing industry.

Jan 1, 2014

By David I. Verrelli, Peter T. L. Koh

"Recent experimental measurements of induction time made by direct observation with the ‘Milli-Timer’ indicated that angular particles were able to attach much more rapidly than spherical particles. There was around a tenfold difference in the respective induction periods for particle-bubble attachment. For industrial application, a more holistic comparison is needed, with the induction period for attachment being just one input. Over the years, CSIRO has developed a CFD-flotation model that incorporates both rigorous hydrodynamics, to simulate real industrial cell geometries, and a detailed model of the embedded flotation process, in which the induction period is an important parameter. We conducted transient modelling of batch flotation. First, spherical particles were modelled, as a ‘baseline’, for different particle sizes and levels of hydrophobicity. In the second set of results, the induction period was decreased by a factor of up to ten, simulating flotation of angular particles. Flotation recovery was found to depend upon induction period in a complex manner. For highly hydrophobic or fine particles, the induction period for spheres was already so low that recovery was limited by other factors (e.g. bubble-particle collision frequency). Further decreases in induction period, as for angular particles, did not have a significant effect on recovery in these cases. By contrast, when weakly hydrophobic or coarse particles were modelled, the recovery was predicted to be greatly enhanced for angular particles, in comparison to spheres. For these particles the induction period was limiting recovery, so that the flotation rate constant could be improved directly by reducing the induction period. This is consistent with batch flotation experiments using Ballotini reported earlier. Therefore, when dealing with weakly hydrophobic particles or relatively large particles that are to be floated, an enhancement can be expected for more angular particle shapes. In such cases, judicious specification of the grinding circuit may improve the overall efficiency."

Jan 1, 2014

By Duong Huu Hoang, Nathalie Kupka, Urs A. Peuker, Martin Rudolph

"The froth ability, froth stability and the froth structure are strong influences in flotation process i.e. on water recovery, bubble size, entrainment of gangue particle, flotation rate constants, grade and recovery. The labscale flotation of rich apatite ore with a high mass pull leads to significant changes in pulp and froth properties over time. The froth stability decreases with increasing the flotation time. These changes can be related to different solid contents, reagent concentration, froth heights and bubble size distributions. This study presents the results from froth studies and discussions on the particle size of fully liberated silicates and degree of entrainment based on automated mineralogy size-by-size analysis. The change of entrainment in a rich apatite ore batch flotation with time will describe more precisely by measuring froth properties using a Dynamic Foam Analyzer. It is concluded that the degree of entrainment is not only dependent on particle size but also the pulp density due to its effect on particle settling and also froth properties in varying resistance to particle drainage. Furthermore, entrainment models are applied to predict the effect of size, flotation time on entrainmentINTRODUCTIONFroth flotation belongs to the group of heterocoagulation separation techniques. Froth flotation is classically divided into two active zones, the pulp zone (where particle collection occurs) and the froth zone. A schematics drawing of the interaction between both zones is plotted in Figure 18 (Yianatos and Contreras, 2010). In froth flotation, the collision probability in the collection zone is governed by the physics of the process or hydrodynamics (Wills and Finch, 2016). The true flotation event in the pulp occurs when the hydrophobic valuable mineral particles collide with bubbles and formation of a stable particle-bubble aggregates moving upwards against gravity to the froth phase (Yianatos et al., 2009)."

Jan 1, 2018

By V. I. Ryaboy, V. P. Kretov, S. E. Levkovets, I. V. Ryaboy

"Using the flotation of a gold-containing ore from a deposit in Kazakhstan as an example, we have conducted a study designing dialkyldithiophosphate collectors, in addition to xanthates, for the flotation of hard-toenrich gold-containing ores to increase gold recovery.The increased flotational ability of the dialkyldithiophosphates was determined by their surface activity at the liquid-gas interface and their hydrophobic ability, the changing of which allowed us to control the collecting power and selective ability of the dialkyldithiophosphates. The studying of the surface activity of aqueous solutions was done using the stalagmometric method and the evaluation of the hydrophobic ability was done in percentage of the relative value of the zinc ion binding in the solution in standard conditions.Studying the influence of surface activity in our designed dialkyldithiophosphate collectors, with their close hydrophobic ability, showed that even with a small increase in surface activity in their aqueous solutions, gold recovery increased by 2-3% in laboratory conditions. Using this enabled us first to apply the dialkyldithiophosphate collector BTF-161 at a plant in Kazakhstan, and then to introduce the specially designed dialkyldithiophosphate collector BTF-163, which has been in use since. Further study of dialkyldithiophosphate activity based on this concept showed us that for the range of short-chain dialkyldithiophosphate collectors with a chain length of up to ?5, the effectiveness of ore processing became lower the higher their surface activity got, with relatively small differences in their hydrophobic ability. For long-chain dialkyldithiophosphates with a chain length of over ?5, ore processing effectiveness increased with the increase of their hydrophobic ability.Based on these studies, a new effective dialkyldithiophosphate collector, BTF-1517, was designed. Using this reagent in continuous gold recovery tests allowed us to reach an 84.21% recovery with a concentrate quality of 15.66 g/t, while using the applied collector BTF-163 in similar conditions led to the recovery of 82.87% with a concentrate quality of 15.65%. As a result, the Kazakhstan processing plant decided to conduct industrial tests with the BTF-1517 collector."

Jan 1, 2018

By Z. Cheng, Y. Han

"For non-sulphide minerals such as oxidized minerals, fluoride minerals, and oxysalt minerals, there are generality in the molecular structure of their floating collectors, and similarity in crystal structure of the minerals. In the paper, adsorbing mechanism of these collectors on the surface of these mineral particles in different pH pulp was investigated by means of Pauling's rules & valence bond theory, Valence-shell electron pair repulsion theory (VSEPR) theory, Crystal and ligand field theory, and quantum chemistry simulation by DMol3 and CASTEP modules of Material Studio software. Besides, the role and status of hydrogen bond in the floating adsorption mechanism were studied emphatically, and the confirmation and characterization of hydrogen bond were explored also based on the test results. What is more, the conclusion “the effect of hydrogen bond can not be overlooked in adsorbing mechanism of flotation collectors on the minerals” and a new viewpoint of multi-polarity collaboration and hydrogen bond coupling were summarized eventually based on analysis of the measurements. Finally, a novel collector 2-Amino-3-Methyl Heptyloxy-Propylamine (AMHP) was developed based on the new viewpoint of molecular structure design, and its collecting performance was exhibited.INTRODUCTIONWhen it comes to the recovery of flotation, it is necessary for researchers to investigate the flotation mechanism of collectors. In traditional theory, when collectors were used to collect minerals, the attractions between collectors and minerals were divided into chemical, electrostatic and physical attractions (Wills, B.A., 2006). Especially, because of the reaction between sulphide minerals and sulphydryl collectors is complex and various mechanism has been proposed (Yoon and Basilio, 1993), when collectors were used to collect non-sulfide minerals, it can be classified into oxyhydryl anionic collectors and cationic collectors. In traditional theory, the adsorption of oxyhydryl anionic collectors were due to water-repulsion, and the adsorption of cationic collectors were due to electrostatic attraction between the polar head of the collector and the charged electrical double layer on the mineral surface (Wills, B.A., 2006)."

Jan 1, 2018

By S. K. Pan

The process flow-sheet adopted in treating hematite iron ore in India through wet circuit generates not only 15-25% slime of Run-of-Mine (ROM), but also results in loss of very high quality fine iron ore particles along with it. As the reserves of hematite iron ore is depleting, it is necessary to explore the possibility of upgrading other types of low grade iron ore and slime for recovery of iron minerals; extensive research in this field is being carried out. While beneficiation of low grade ore is yet to be established, slime beneficiation has been quite successful and many installations of slime treatment plant are underway. In SAIL mines, the slime is mainly the discarded particles from Classifiers, which are less than 0.2 mm sizes. R& D initiative has been focussed on the beneficiation of the slimes (49-60% Fe, 3-10% Al2O3 & 4-10% SiO2) of Dalli mines to generate concentrates assaying 62-64% Fe, 2-3% Al2O3, 3-4% SiO2 and a few innovative facilities for the same has been introduced at this mines of Bhilai Steel Plant (BSP). At Dalli mines, the slime is of very poor quality. A typical slime analysis assays 48.54% Fe, 15.1% SiO2, 8.5% Al2O3 and consists nearly 60% (by wt.) particles less than 38 micron. Slime analysis revealed substantial quantity of very high density mineral particles, those causes jamming of Thickener due to faster settling. A novel technique has been implemented to classify the concentrate ore particles from the gangue mineral particles by processing through Fluidized Bed Classifier (FBC) system, which is a gravity concentrator, to treat 50% of the slime generated and the rest is treated through de-sliming hydro-cyclone followed by Medium Intensity Magnetic Separator (MIMS). A special self-vibrating launder has been designed and introduced into the system to recover tiny iron ore particles, which could not get captured by the permanent Neodymium rare earth magnet in MIMS. The classified iron mineral particles from FBC are further treated in a battery of hydro-cyclones followed by modified Slow Speed Spiral Classifier (SSSC) unit. Multiple feed entry system to the SSSC unit is unique and use of particular feed entry point depends on the desired quality of the product and thus converted to a beneficiation equipment rather than mere de-watering unit. By processing slime in FBC system, the valuable iron ore particles with 62.5% Fe, 5.2% SiO2, 2.23% Al2O3 has been recovered from the slime at a material yield of 30%. And very high valued concentrate particles with more than 65% Fe has been sorted out through the magnetic separation route. The overall extra production of beneficiated slime concentrate is 40-45 tph with 63-64% Fe from a slime feed of 120-130 tph solid. This paper outlines few new approaches in iron ore slime beneficiation at Dalli mines for maximum recovery of valuable minerals. Keywords: fluidized bed classifier (fbc), iron ore slime of dalli mines, medium intensity magnetic separator, slow speed spiral classifier (sssc)

Sep 1, 2012

By M. Niinae

Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble sub-stances. At a higher pH, the soil particles sorb more heavy metals, such as cadmium, than at a lower pH and the precipitation reactions of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering clean up more difficult and electrokinetic extraction inefficient. There-fore, the acidification of soils is very important to increase the clean up efficiencies of heavy metals, such as cadmium by electrokinetic method from contaminated soils. In the present study, acidification of soils and cadmium transport are predicted with a numerical method in which electrical flow is coupled with hydraulic flow, and the sorption process in the soils is induced in the model. The effects of some factors such as electrode configuration, electric field strength and electrode spacing for saturated soils are investigated using this numerical model. The results obtained this study are summarized as follows: The two-dimensional electrode configurations containing cathode surrounded by three or more anodes rapidly acidify the soils and remove cadmium from soils compared with one-dimensional electrode configuration. However, two-dimensional electrode configurations develop spots of inactive electric field between cathodes. A larger electrode spacing increases the processing time required, and it was also found that a larger electric field strength reduced the processing time required.

Jan 1, 2014

By Ataollah Nosrati

Agglomeration of fine mineral particles is an important step in heap leaching processes employed for a cost-effective hydrometallurgical extraction of value metals from low-grade ores. In this study, the effect of acidic binder composition and feed ore particle size on binder dosage requirement and isothermal, batch agglomeration behavior of siliceous goethite nickel laterite has been investigated. Agglomeration tests performed with tap water and 30, 44 and 98% w/w H2SO4 solutions as binders revealed the key role of binder formulation in controlling ore particle wettability, nucleation and granule growth behavior. Both lower binder acid content and higher dosage led to greater wetting, nucleation and granule growth rates. Variation of feed ore fine/coarse particles? mass ratio dramatically impacted on binder dosage requirement for effective particle wetting, nucleation, and growth agglomeration behavior. Increasing fine (-150 µm) fraction mass content in a -2 mm feed ore, led to higher binder dosage requirement and enhanced nucleation, however the overall agglomeration rate/granule size growth decreased. In contrast, the presence of coarse (5 ? 15 mm) particles in feed ore led to (i) lower binder dosage requirement, (ii) enhanced initial agglomerate size growth rate, and (iii) reduced coalescence. For dry agglomerates of similar sizes, competent coarser feed particles led to remarkably higher compressive strength than did finer feed particles. Microstructure analyses indicated that the granules containing coarser particles exhibited a distinctive, competent core/shell (fines) structure which led to their structural reinforcement. The appropriation of the findings for optimizing agglomeration behavior for enhanced heap leaching of complex, low grade laterite ores are discussed in this context.

Sep 1, 2012