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By Brian Hart, Rong Fan, Roger Smart, Andrea Gerson, Ning Xu

A complete strategy has been developed for identification of the reasons for losses in recovery and/or grade, due to changes or complications in mineralogy and in mineral surface conditioning, and their subsequent correction. The sequence of methods starts with comparison of mineral phases between QEMSCAN/MLA (compositional) and Rietveld XRD (crystalline diffraction) with bulk assay reconciliation. This methodology has recently led to identification of unrecognised amorphous content (12-40 wt.%), previously attributed to crystalline phases, in the fine fraction (<35 µm) of some problematic flotation feeds. Attached amorphous silica, talc- and chlorite-like fines have direct influence on the hydrophobic/ hydrophilic ratio on value mineral surfaces adversely affecting flotation. SEM/EDS is used in the backscattered imaging mode to determine possible problems with liberation (e.g. remnant local locking), not detected in standard liberation analysis, resulting in gangue flotation. EDTA extraction is used to assess bulk feed pre-oxidation and sequential oxidation product loading through the circuit. Changes in circuit solutions are assayed with speciation modelling of precipitates and potentially adsorbing species. ToF-SIMS with principal component analysis is then used to correlate surface species with specific minerals and can be used to assess the effectiveness of specific reagents particularly collectors. This approach identifies unwanted activating species and interference with value surfaces by adsorbed hydrophilic ions, precipitates and fine particles. When the interference or ineffective reagents are specifically identified, remedial action can be targeted. This method has identified residual talc-like layers (<10 nm thick) inducing gangue flotation of pyroxene and chromite in PGM flotation. Recent case studies of application of the full methodology to losses of molybdenite at KUCC and to sphalerite activation in the Cu/Pb circuit at Brunswick Mines with remedial action are discussed.

Jan 1, 2014

By Hillary Williams, Ronghao Li, Christopher Marion, Kristian E. Waters, Devin Hundt

"Zircon is an important mineral for ceramic, foundry, casting, and refractory applications; and it is the worlds primary source for zirconium. Zircon can also contain large and valuable proportions of other valuable metals, such as rare earth elements and hafnium. The Nechalcho deposit (Northwest Territories, Canad), is a hard rock REE deposit, which looks to recover zircon for its Zr and REE content. In this deposit, zircon is finely disseminated and associated with predominately silicate gangue minerals. Most of the work to date has focused on the beneficiation of mineral sand deposit, which typically remove silicate gangue minerals through physical separation steps. Therefore, the separation of zircon from silicate gangue, such as quartz, by flotation, has received little attention. This work used zeta potential measurements and microflotation experiments to understand the interaction between zircon and six different collectors (sodium oleate, sodium dodecyl sulphate, dodecylamine, SM 15, K-octyl hydroxamate and Florrea 7510). The results were compared with those of quartz. This study indicated that selective separation of zircon from quartz without the use of selective depressants or activators is likely challenging. The findings suggested sodium oleate and SM 15 only offered selective flotation of zircon in highly acidic conditions. Separation by the flotation of quartz is possible using sodium dodecyl sulphate, dodecylamine and K-octylhydroxamate. However, selective separation is highly dependant on collector dosage, for dodecylamine, and the selective activation of quartz, for sodium dodecyl sulphate and K-octyl hydroximate. Florrea 7510 offered poor recoveries for both zircon and quartz.INTRODUCTIONZircon (ZrSiO2) is a nesosilicate mineral which has a wide variety of applications, due to its hardness, opaqueness and resistance to heat and corrosion. Its major end uses are in ceramic, foundry, casting, and refractory applications (Bedinger, 2017). Zircon is also the most abundant zirconium (Zr) bearing mineral in the earths crust and is the principal economic source of Zr (primarily used in alloys for heat and corrosion resistance) and zirconia (ZrO2) (primarily used in ceramics) (Bedinger, 2017; Milnes and Fitzpatrick, 1989). Zircon forms in silicate melts and can often contain large proportions of other valuable metals such as rare earth elements (REE), and hafnium (zircon is the primary source of hafnium) (Bedinger, 2017; Belousova et al., 2002; Orlova, 2007). A common chemical formula showing the range of substitution in zircon is (Zr,Hf,Th,U,REE,Ca,Fe,Nb,Ta)(Si,P)O4 (Orlova, 2007)."

Jan 1, 2018

By V. Dementiev

Pyrite cinders is a complex raw material, in which the valuable metals are: Au(2.04 g/t), Ag(35.0 g/t), Cu(0.38%), Zn(1.1%) and Fe(56.0%). In this case high costs for mining and ore processing are not required. The hydrometallurgical treatment of pyrite cinders using thiourea, sulfite and cyanide solutions are examined in this paper. It was found that thiourea leaching is ineffective due to high consumption of thiourea and sulfuric acid. The cyanidation on pyrite cinders was conducted. Various options of the preparation of the products for the subsequent cyanidation have been examined. The tests on cyanidation process optimization were conducted. The effectiveness of these cementation methods by metallic iron or extraction for copper recovery from water phase has been shown. Zinc precipitation can be found in the form of carbonate. In order to recover noble metals from cyanide solutions, the cementation onto zinc dust was tested. The developed technology provides for recovery at 49-56%Au, 20-25%Ag, 22.5%Cu and 50%Zn during NaCN (1.4 kg/t) and CaO (6 kg/t) consumption. The results of pilot plant testing are the basis for technical regulations in order to design a pyrite cinders treatment plant. The technology has been examined in pilot-plant conditions. In this case the recovery of 54.5%Au, 45.3%Ag, 30%Cu and 49.9%Zn was achieved to provide saleable products. Keywords: pyrite cinders, thiourea leaching

Sep 1, 2012

By Ghislain Bournival, Seher Ata, Graeme J. Jameson

A common method to prevent bubbles from coalescing in a flotation cell is by the addition of surfactants, called frothers. The gas dispersion properties in a column were tested for solutions of 1-pentanol, tri(propylene glycol) methyl ether, and poly(propylene glycol) in the presence of sodium chloride. The dependency of surfactant on the gas holdup can be divided into regions. It seemed that for a sufficiently low concentration of surfactant, even a stronger surfactant could show a transition in gas holdup from constant/decreasing to increasing with concentration. This region, however, was not marked by a decrease in the average bubble size. In addition, PPG gave higher gas holdup values while averaging larger bubbles. On the other hand, sodium chloride mostly affected the gas holdup when the concentration was high enough to prevent bubble coalescence. Another parameter affecting the gas holdup was the superficial gas velocity. A linear dependency was found between the two under a bubbly flow regime. The current study showed that both surfactants and salt could slightly affect the influence of the superficial gas velocity on the gas holdup.

Jan 1, 2014

By S. Q. Zhu

Coal Water Mixtures (CWMs) are densed suspensions of coal particles in water. Viscosity is one of the most important rheological properties of CWMs and it is desired to be as low as possible. The slurry viscosity was influenced significantly by additive formation, the particle size distribution and the ash content of the coal. However, the influence of dispersants is most obvious. At present, there are several kinds of dispersants such as polymeric styrene sulfuric sodium, lignin sulfonate, humate, polycarboxy salt, ethylene epoxide surfactant. In this paper, a newly synthesized CWM dispersant has been reported, which is an efficient anionic surfactants of polycarboxylic acid type. The synthesis process includes three steps. At the beginning, the polyglycol acetate ester has been performed by acetic acid and polyethylene glycol (PEO) on the condition of acetic-acid/PEO ratio 1:1.1, at 368~373K for 30 minutes. Then the macro-monomer is prepared through the esterification of 85.71% acrylic and 14.29% polyglycol acetate ester, at 368~373K for 10 minutes. After that, the polycarboxylic acid CWM dispersant is polymerized using proper proportion macro-monomer, acrylic (AA) and sulfonic styrol sodium, at 368~373K for 1 hour. This new dispersants are used in the coal water mixtures formulation. Four kinds of coal used in the experiment are Shuang Yashan, Tunliu, Luning, Changcun samples. ? The highest concentration for shuanyashan coal is 70% when the dosage of dispersant is 0.4%, and the content of -200 meshes particles is 75.53%. As the dosage of dispersant de-creases to 0.25%, the Shangyashan CWM concentration is 67%. ? For Tunliu coal CWM concentrations are in the range of 76% to 75% when dosage of the dispersant changes from 0.4% to 0.25% at the same particle size distribution of 83.5% minus 200 meshes. ? The highest concentration for Luning coal is 69% when dosage of the dispersant is 0.4%, and the content of -200 meshes particles is 88.86%. ? For Changcun sample, the coal concentration of CWM is 73%~75% when dosage range of the dispersant is 0.35%~0.5%. The experiments show that the synthesied dispersant is quite promising for some coals CWM preparation, but a little bit coal-dependent. The Proximate and Ultimate analysis, surface characteristic measurement have been made to investigate the interactions between coal and additives.

Jan 1, 2014

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 µm to 150 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2014

By Lucy van de Ruit, Megan Becker, Aubrey Mainza, Jenny Wiese

"UG2 chromitite ore is a complex, highly disseminated platinum ore from the Bushveld Complex in South Africa, with typical platinum group mineral (PGM) grain sizes below 15µm. The introduction of stirred mills to the platinum industry has enabled grinding to finer product sizes, which has improved liberation and recovery of the finely grained PGMs. However, reduction in particle size leads to an increase in chromite entrainment in the flotation concentrate, which has a negative impact on the subsequent smelting process. Factors such as particle size, froth structure, solids concentration and water recovery have all been identified as impacting entrainment, but whether particle shape also has a significant effect is unclear. The purpose of this study was to determine whether the recovery of chromite particles by entrainment during the flotation of UG2 ore is affected by particle morphology. A laboratory vertical stirred mill with inert ceramic media was used for grinding UG2 ore which was then floated in a batch flotation cell. Flotation feed and concentrate samples were analyzed using QEMSCAN to quantify the angularity and aspect ratio distributions of the particles. The stirred mill product was found to have relatively broad aspect ratio and angularity distributions, with the major mineral components (chromite and silicates) having very similar shape characteristics. Analysis of flotation feed and concentrate samples suggested that particle shape does not have a significant effect on chromite entrainment."

Jan 1, 2014

By S. A. Kondratyev

"The present research work aims at disclosing the dependence of flotation concentrate recovery and its grade on the physically adsorbed collecting reagent properties, viz., surface pressure in the reagent film at gas-liquid interface, velocity of reagent species spreading over the said interface, relation between interaction energies of collector molecules within a film and with water dipoles.When using a single collecting reagent it is possible to improve the flotation concentrate grade in two ways, namely, by reducing collector consumption rate or using a weaker reagent. According to the proposed mechanism, a decrease in the physically sorbed species of the collector leads to a decrease in the rate of removal of the kinetic restriction of a flotation contact formation. As a result, the recovery of the useful component is reduced and the content of valuable components in the flotation concentrate is increased. The relationship between the spreading velocity of physically sorbed species at the gas-liquid interface and the recovery and quality of the flotation concentrate has been experimentally proved. Reduction in collector consumption lowered the valuable component recovery at a higher grade of the concentrate.The reasons were established for a rise of valuable content in the flotation concentrate if a weaker collector was used. It is justified that the use of a weaker collecting reagent with a shorter hydrocarbon fragment declines physically sorbed species of collector. The spreading velocity of collector derivatives at gas-liquid interface tends to lower along with less participation physically sorbed species of collector in formation of a flotation aggregate. The spreading velocity is determined for products of interaction between butyl-and ethyl-xanthates and lead nitrate at gas-liquid interface. It is found that the spreading velocity of butyl-xanthate derivatives is higher than that of ethylxanthate derivatives.The research work gets insight into the nature of relation between useful component content in the flotation concentrate and the useful component recovery. It is pointed out that adjusting the collecting activity of a collector makes it possible to influence a useful component content in the froth product thus gaining a compromise between wanted grade and recovery parameters."

Jan 1, 2018

By Lev Malytin, Alexander Dyachenko, Roman Kraydenko

"A new method of processing beryllium raw materials based on interaction of beryllium mineral with ammonium fluoride was developed. Possibility of extracting ammonium tetrafluoroberyllate from bertrandite and phenakite minerals is proved. The developed technology allows replacing the outdated sulfate technology developed by Materion Corporation. INTRODUCTION Beryllium is a strategic metal, which is produced only in three countries: the USA, China and Kazakhstan. The world production of beryllium amounts to only 300 tons per year. More than 75% of the world beryllium production is manufactured from oxide beryllium ores in the USA by Materion Corporation. In Russia there is a large-scale beryllium ore deposit «Ermakovskoye» containig over 1 million ton of ore. Concentration of beryllium in ore amounts to 1,2%. Since the mineral base of ore is calcium fluoride, the sulfate technology of Materion Corporation cannot be used. After alloying and sulphuric acid leaching the fluorine-ion found in fluorite and beryllium together evolve into the aqueous phase. At the stage of Be(OH) precipitation fluoride-ion prevents complete isolation of beryllium into the phase of hydroxide, which increases the loss of beryllium. A new ammonium-fluoride method for processing high-fluoride beryllium ores has been developed at Tomsk Polytechnic University. The ammonium-fluoride method involves fusion of ammonium fluoride (NH4HF2) with a beryllium concentrate. The concentrate containing 10% of beryllium oxide and 25% of calcium fluoride is produced by flotation from the ore of Ermakovskoe deposit. The main component of the ore concentrate is fluorite CaF2, which does not react with NH4HF2. Beryllium in this concentrate is represented by two minerals: phenakite Be2(SiO4)2 and bertrandite Be4[Si2O7](OH)2. Ammonium fluoride, unlike sulfuric acid, does not react with calcium fluoride and is not consumed for decomposing the mineral base of the concentrate. Ammonium fluoride is an accessible and environmentally safe reagent, worth up to $ 1,200 per ton. The total amount of ammonium fluoride is recycled and is used for decomposing a new batch of beryllium concentrate."

Jan 1, 2018

By Lev Malytin, Alexander Dyachenko, Roman Kraydenko

"A new method of processing beryllium raw materials based on interaction of beryllium mineral with ammonium fluoride was developed. Possibility of extracting ammonium tetrafluoroberyllate from bertrandite and phenakite minerals is proved. The developed technology allows replacing the outdated sulfate technology developed by Materion Corporation. INTRODUCTION Beryllium is a strategic metal, which is produced only in three countries: the USA, China and Kazakhstan. The world production of beryllium amounts to only 300 tons per year. More than 75% of the world beryllium production is manufactured from oxide beryllium ores in the USA by Materion Corporation. In Russia there is a large-scale beryllium ore deposit «Ermakovskoye» containig over 1 million ton of ore. Concentration of beryllium in ore amounts to 1,2%. Since the mineral base of ore is calcium fluoride, the sulfate technology of Materion Corporation cannot be used. After alloying and sulphuric acid leaching the fluorine-ion found in fluorite and beryllium together evolve into the aqueous phase. At the stage of Be(OH) precipitation fluoride-ion prevents complete isolation of beryllium into the phase of hydroxide, which increases the loss of beryllium. A new ammonium-fluoride method for processing high-fluoride beryllium ores has been developed at Tomsk Polytechnic University. The ammonium-fluoride method involves fusion of ammonium fluoride (NH4HF2) with a beryllium concentrate. The concentrate containing 10% of beryllium oxide and 25% of calcium fluoride is produced by flotation from the ore of Ermakovskoe deposit. The main component of the ore concentrate is fluorite CaF2, which does not react with NH4HF2. Beryllium in this concentrate is represented by two minerals: phenakite Be2(SiO4)2 and bertrandite Be4[Si2O7](OH)2. Ammonium fluoride, unlike sulfuric acid, does not react with calcium fluoride and is not consumed for decomposing the mineral base of the concentrate. Ammonium fluoride is an accessible and environmentally safe reagent, worth up to $ 1,200 per ton. The total amount of ammonium fluoride is recycled and is used for decomposing a new batch of beryllium concentrate."

Jan 1, 2018

By Andrew T. McBride, Malcolm S. Powell, Indresan Govender

"Current empirical Semi Autogneous Grinding (SAG) mill models contain assumptions concerning the amount of energy available for particle breakage, how this energy is distributed in the mill media and the rate at which the energy is transferred. Despite these assumptions the JK SAG model is highly functional with a proven track record. DEM provides a numerical framework to greatly improve on these assumptions that were necessary due to a lack of available input data.This paper identifies key outputs of the Discrete Element Method (DEM), such as energy spectra and impact probability distribution. It describes how they can be incorporated into current mill models utilising practical rock breakage data. The rate at which energy is transferred is shown to be dependent on particle position and mill rotational speed and not once per cycle as previously assumed. Based upon this an improved energy transfer methodology is presented. The fundamental outputs of the DEM are validated against experimental three-dimensional particle tracking data, so as to establish whether the DEM produces correct energy transfer predictions on the inter-particle level, which is crucial to this work."

Jan 1, 2003

By J. K. Qu

As one of the key inorganic chemical industries, the chromate chemical industry has spawned extensively public concerns due to the resulted environmental pollution. The cleaner production technology for chromium compounds bases on sub-molten salt medium developed by the Institute of Process Engineering, Chinese Academy of Sciences has greatly decreased the reaction temperature and energy consumption, significantly in-creased the utilization ratio of the chromium element, and successfully achieved the comprehensive utilization of chromite resources and zero emission of chromium-containing residue. The separation process of production is the most important components in the cleaner technology. In this work, we studied two parts: the first is the removal of SiO2, Al3+ from the system and the recycling utilization of alkali metal medium through adding Ca(OH)2 and CaO; the second is to get more pure K2CrO4 crystalloid and remove K2CO3 from KOH solution through evaporation to prepare raw material for manufacturing Cr2O3 and get 50%(wt) KOH. The results obtained show that Ca(OH)2 can remove Al3+ more than CaO and has lower caustic ratio than CaO when they were added 110% of theoretic quantity. The optimal pure K2CrO4(96%) can be gained at 45 Celsius degree in 30% KOH solution and K2CO3 in 50% KOH solution could be decreased to 3.5%(wt) at 40 Celsius degree. And then K2CO3 can be causticized with adding Ca(OH)2 to recycle potassium alkali. The impure material can be re-moved and suitable raw material for manufacturing Cr2O3 can be gotten and reaction medium can be also recycled in this process technology, realizing cleaner production effectively.

Jan 1, 2014

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

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

Jan 1, 2014

By 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 Grant C. Lukey, Jannie S. J. van Deventer

"The environmental effects of the mining and mineral industry include destruction of natural habitats, changes in river regimes and water tables, and other serious ecological impacts. In this century, it is likely that water will become a critical resource, and in most countries the mining industry competes for a share of this resource. The Kyoto Protocol may at first seem only relevant to the coal mining and power industry, however, it should not be forgotten that the mining and mineral industry is a significant consumer of power. Therefore the ratification of the Kyoto Protocol by most developed countries and the introduction of a carbon credit trading scheme will impact on the industry by potentially increased costs in utilities and waste discharges. It is clear therefore that the mining industry faces many challenges in the coming years. The mining industry?s commitment to sustainable development needs to continue to evolve, in order to meet these challenges effectively. With the advent of globalisation of the industry, it is now an opportune time for the industry to gain international agreement on how they want the industry to achieve sustainability in future years; such a progressive approach is necessary, otherwise government will force the industry to change, which may not necessarily be the best outcome for the industry.INTRODUCTIONThe Earth Summit in Rio de Janeiro in 1992 was an opportunity for world leaders to assemble and discuss strategies and initiatives that provide for further industrial growth without adverse effects on the environment. The World Summit on Sustainable Development held last year in Johannesburg, South Africa, was an opportunity to evaluate those initiatives implemented over the past 10 years, and to set a new and sustainable direction for the future. It is clear that industrial and technology development will continue at a rapid pace in order to serve the needs of a growing world population, but it is essential that the course of this development is well planned, well executed, and that it is sustainable. In reality, while government officials and politicians continue to debate policy and international protocols, the environment continues to suffer and the effects of climate change and global-warming become more real each day."

Jan 1, 2003

By Sergey Ulianov, Arkady Senchenko, Alexey Shvets, Arkady Bakotin

"This paper is devoted to ultrafine grinding of processing products. This process allows one to include into operation complex ores which earlier were considered as inefficient and economically inadvisable to treat. Fine dissemination of valuable component often does not allow its liberation via standard grinding in ball mills, and therefore requires modern methods of ultrafine grinding (UFG). An example of successful ultrafine grinding usage is its application for crude flotation concentrates regrinding before cleaner flotation stages. A problem often arises with a commercial copper concentrate production in the course of copper ore flotation. Crude flotation concentrate regrinding in a ball mill does not provide for good liberation of the material before cleaner stages. UFG application allows one to get commercial copper concentrate with copper grade of 20% and higher. Another example of ultrafine grinding application is its usage for highly refractory pyrite product received after gold-lead scavenger flotation of polymetallic ore. Earlier this product treatment was economically inefficient. At current application of ultrafine grinding down to 85% minus 20 µm and subsequent gravity processing it is possible to pass major part of gold (73.4%) into concentrate. The constraining factor for UFG application in processing may be the chemical activation of minerals. In the result of this, flotation selectivity may decrease. Therefore ultrafine grinding application extends the areas of efficient usage of metallurgical processes. New technologies allow increasing the level of valuable metals recovery."

Jan 1, 2014

By Vladimir Vigdergauz

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

Jan 1, 2014

By Masanori Mori, Hajime Miki, Osamu Ichikawa, Tsuyoshi Hirajima, Mitsuru Sawada, Keiko Sasaki

For pretreatment of selective flotation, surface oxidation of chalcopyrite and molybdenite was applied by oxygen plasma then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc.

Jan 1, 2014

By P. Fawell, C. Castillo, C. Ihle

"The need to reduce fresh water consumption has pushed many Chilean mining companies to utilize seawater obtained from distant locations. At the same time, increasing amounts of fine particles in copper tailings raise new operational challenges, in particular, the thickening and transport of tailings featuring significant fine fractions, which are predominantly clays. In the present paper, we study the role of salinity – using seawater and NaCl – on the flocculation efficiency of copper sulphide tailings to which kaolinite was added. To mimic the water recovery stage in thickeners, flocculation has been induced in jar tests and the corresponding aggregate size distribution has been estimated from chord length distribution data obtained using a focused beam reflectance measurement (FBRM) probe, at various mean turbulence intensities. Results show that for constant flocculant dosing, a measurable influence of the salt on the resulting aggregation exists. For each case, resulting optimal turbulence levels are also reported, a particularly interesting feature when comparing flocculation efficiency of the coarse and fine fraction. INTRODUCTION The concentration of copper minerals through comminution and flotation is intensive in the use of fresh water. The need to reduce the consumption of fresh water and the environmental standards associated with increasingly demanding mining operations have driven improvements in the techniques of recovering water from tailings. The challenges are even greater when required to treat minerals with high clay contents. In Chile, kaolinite is one of the most important clays to consider due to its abundance in the tailings from many operations. The most common and highest throughput unit operation in the mining industry for the recovery of water from tailings is gravity thickening, with sedimentation of fine particles assisted by flocculation. Flocculation is the process of forming aggregates by contacting the suspended particles with a flocculant. The flocculant is typically a water-soluble synthetic long-chain polymer, where copolymers of acrylamide and sodium acrylate are the most common types used in the Chilean mining industry. The aggregation mechanism includes the following key steps: (1) flocculant distribution through the suspended particles, (2) flocculant adsorption onto particle surfaces, and (3) collisions between particles leading to polymer bridging to form aggregates, but concurrently (4) breakage of aggregates becomes a factor under prolonged shear (Gregory, 1988)."

Jan 1, 2018

By Lawrence Bbosa, Aubrey Mainza, Indresan Govender

"Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to develop a probability based model for the power draw of a tumbling mill. Experiments are conducted using dry spherical glass bead charge in a laboratory scale tumbling mill, which is mounted with a torque transducer and tachometer to measure mill power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behavior, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For both sets of data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all tests. The information from both techniques is then used to develop a model for the power draw as a function of particle size, mill speed and volumetric filling. Predictions of the model match well with measured and calculated values. The model is found to predict mill power within close agreement with measurement and follows trends consistent with existing work on tumbling mill modelling."

Jan 1, 2014