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By Barun Gorain, Aparup Chattopadhyay

"Many double refractory gold deposits are characterized by the dominance of ""invisible gold"" (sub-microscopic gold) as solid solution or as colloidal-sized particles in different sulfides and other phases. These deposits are mainly composed of silicates and carbonates with moderate clay and mica content and with minor amount of sulfides and organic carbonaceous matters. The presence of highly preg-robbing and finely disseminated carbonaceous matter adversely affects gold recovery in leach circuits. Characterization of carbonaceous matters, commonly known as TCM and quantification of gold associated within these carbonaceous matters along with different sulfide and oxide phases is highly complex and challenging. Studies were initiated on various complex ore deposits and also on samples representing various process streams. This paper presents the development of a systematic approach to gold deportment studies using state-of-the-art mineralogy characterization techniques for quantification of invisible and visible metal contents in various species. The relevance of this mineralogy characterization to metallurgy will also be discussed in this paper."

Jan 1, 2014

By S. P. Nagaeva, A. V. Kuptcova, O. Yu. Poperechnikova

"The present paper contains study results of gold morphology and grain size distribution in flotation concentrates produced from original ore samples from deposits of different genesis. Pre-concentration methods were used with selective dissolution of rock minerals and mineral heavy medium separation to obtain statistically valid data on gold grain size and morphology in concentration products. Special attention is given to study of flash flotation concentrates that is mainly used for coarse gold, underextracted in gravity circuit. Analysis of geometrical optics has allowed to establish that during flash flotation gold grains more than 150 µm can be extracted from 10 to 35%, and in some cases single gold grains above 300 µm. INTRODUCTION Distinctive features of gold that have a significant impact, and in some cases, decisive influence on its recovery into saleable products are mineral shape, grain size and morphology of metal particles, paragenetic associations of gold. Peculiar feature of coarse gold is its easy extraction during grinding from associated mineral components like quartz, sulphide and other and almost complete recovery into gravity concentrates (Lodeischikov V.V., 1997). Morphology of native gold is so diverse that different gold grains are better extracted using different methods of concentration. Compacted and rounded particles are easily processed using gravity concentration but low cyanidable and hard to process using flotation. On the contrary, lamellar, flake, dendrite and capillary aggregates of high specific surface are easily cyanidable and under definite conditions it has strong floatability (Lodeischikov V.V., 1997). Flotation of gold-containing sulphide minerals and free gold takes place simultaneously during flotation concentration. In case of low-sulphide ores, native gold takes the basic load, having the high density (15.6 to 18.3 g/cm3, for pure gold – 19.3 g/cm3) it has limited size and morphology for successful flotation. It is known that flake gold and fine-grained gold up to 0.1 mm are easily extracted (Lodeischikov V.V., 1997). Authors of the present paper performed a study of gold granulometry and morphology in flotation concentrates produced from gold-containing ores from two deposits of different types: gold-copper oxidized hematite ores and low-sulphide gold-quartz ores. Ores are different by both host rock composition, mineralogical and petrographic features, gold grade in mineral assemblage and morphology and size of precious metal. Common for both ore types is low-sulphide content and presence of free gold."

Jan 1, 2018

By Diego Mesa, Willy Kracht

Frothers may be classified as weak or strong depending on their ability to produce stable froths, which is related to the amount of water that they transfer from the pulp to the froth. They can also have an effect on the non-selective mechanism of recovery by entrainment, implying that both selectivity and froth stability are, at least to some extent, frother dependent. Solids, on the other hand, also have an effect on froth behaviour. Clays, which are characterized by their small particle size, laminar shape, and high specific surface, tend to report to the froth phase and have an enormous impact on both froth stability and the overall performance of the flotation process. The purpose of this work is to shed light on the effect that different frothers have on the froth behaviour when clays are present. In order to do that, two sets of experiments were conducted using frothers from the families of alcohols and polyglycols. For each test, the equilibrium froth height was measured at different frother concentrations in an agitated machine with an acrylic square-base cell that was 11 cm wide and 25 cm high. The cell was designed in such a way that froth was able to grow without concentrate discharge. In the first set of tests, pure clays such as kaolinite and montmorillonite were used. In the second set, an actual copper sulphide ore with a high content of clays was used as solid phase. The results, expressed as curves of equilibrium froth height against frother dosage, showed a coupled effect of frother-clay on froth behaviour for both sets of experiments. In some cases, the froth grew up until the border of the cell with only a few parts per million of frother. In other cases, the equilibrium froth height varied smoothly with frother dosage. The results suggest that choosing the right frother can be of use for controlling the froth behaviour when dealing with clay-rich froths, using frother dosage as the control variable. The application of these findings at industrial scale are discussed and some recommendations are given.

Jan 1, 2018

By M. Ghiani, R. Peretti, S. di Giovanni, G. Zonnedda, A. Serci, A. Zucca

"Beneficiation of the epithermal gold mineralizations associated with an extensive alteration zone in the Serrenti-Furtei region on the island of Sardinia, is proving a complex issue. Experimental investigations have in fact demonstrated that while the ores contained in the upper parts of the deposit are amenable to conventional cyanidation, the gold contained in the refractory ores in the lower portions needs to be recovered by means of flotation, combined with leaching where necessary.The results of commercial heap leaching, carbon-in-leach (CIL) processing and flotation, designed on the basis of the experimental findings and applied to the oxidized portions and transition zones of the deep sulphide mineralizations, confirmed the expectations emerging from the laboratory tests."

Jan 1, 2003

By Y. Posedko Eugene, S. S. Gudkov, Yu. E. Emelyanov, A. V. Bogorodsky, A. V. Boldyrev, S. V. Balikov

"The article presents the results of precious metals leaching using halogen solvents and their precipitation on a sorbent in the process of pressure oxidation. A technology of pressure oxidation – carbon-in-leach treatment (POX-CIL) of refractory sulphide gold-bearing flotation concentrates with the addition of a halogen solvent and a sorbent was developed based on the laboratory studies and pilot plant tests. The technology involves the following steps: oxidation of a flotation concentrate; precious metals dissolution and recovery on a sorbent; precious metals elution; electrolysis of eluates; smelting of cathode precipitates with producing Dore beads. This approach ensures oxidation at least 98% of sulphides and gold of more than 95%. The POX-CIL process have the following patents: a patent of the Eurasian Patent Organization No.017438 “A method of processing materials containing precious metals and sulphides” and a patent of the Russian Federation No.2625146 “A method of precious metals recovery from refractory sulphide gold-bearing materials”.INTRODUCTION Gold-bearing ores are classified as readily amenable to cyanidation, or non-refractory, and not readily amenable to cyanidation, or refractory [1]. Special attention should be given to the three most common technological types of gold-bearing ore materials, according to the Irgiredmet’s classification: pyrite-arsenopyrite ores with finely disseminated gold locked in sulphides (physical depression of gold in cyanidation process); cupriferous gold-bearing ores, when cyanidation comes along with chemical depression of gold by mineral compounds (cyanisides); carbonaceous ores showing higher sorption activity to precious metals dissolved in cyanide. Direct cyanidation of refractory sulphide gold-bearing materials does not provide high recovery of precious metals. There are the following methods of refractory gold-bearing ores and concentrates preparation to subsequent gold recovery: roasting, fine grinding, bacterial and pressure oxidation (POX) [2]. Existing POX-cyanidation flowsheets involve high costs due to a large amount of process operations and using expensive and environmentally hazardous sodium cyanide."

Jan 1, 2018

By I. Ngoma, Marijke Fagan, Susan Harrison, Rebecca Chiume

"Heap bioleaching is an unsaturated hydrometallurgical extraction process which is commonly applied to the recovery of copper from low grade sulfide ores as well as for preparatory treatment of gold ores. The leaching reactions occur in the liquid phase, catalysed by iron and/or sulfur oxidising micro-organisms. Contact of the mineral grains with the leaching solution is consequently essential for metal recovery. Additionally, the liquid is responsible for the transport of the liberated metal out of the heap under gravitation-driven flow. However, the highly inhomogeneous structure of the heaps coupled with low irrigation rates cause the flow to vary between being gravitationally and capillary dominated, resulting in non-uniform wetting of the ore. In this study a 132 kg agglomerated ore ‘slice’ is used to examine the effect of liquid distribution on microbial colonisation and mineral recovery in a long term bioleach (> 500 days) when irrigation from a single drip emitter source is employed. The novel setup enabled sample collection from ports positioned along the length and height of the ore bed, so that 2D maps of the degree of wetting and microbial colonisation could be generated at different times in the leach. Lateral movement of the liquid increased with bed depth; the majority of flow was below the irrigation point while the top corner of the bed that was not irrigated remained the driest region of the heap throughout the experiment duration. The lowest cell numbers were also recorded in the driest regions. Specifically, cell numbers in the top corner of the bed, 400mm from the irrigation point, remained at undetectable levels until the 283rd day measurement, in line with typical heap operation durations. This indicates that slow colonisation of the heap in the regions between irrigation points may be a significant issue in heap optimisation."

Jan 1, 2014

By Raquel Franco de Souza Lima, Isao Matsuoka

"Microflotation studies and abstraction experiments were conducted with synthetic oxide spinels relating to chromite (MgCr2O4, FeCr2O4, FeFe2O4 and FeAl2O4), using sodium oleate as collector. An attempt was done to correlate this data with the speciation of oleate in the bulk solution and at the interface solid-water, to explain the floatability curves. The microflotation tests were conducted using a microflotation cell. The abstraction of sodium oleate was measured at 25°C, with one gram of synthetic spinel and the abstraction time was 30 minutes. After centrifuging, the residual oleate concentration in the supernatant was measured by using the spectrophotometric method described by Mizuniwa et al. (1977), that covers the range from 1.5 to 9 ppm. To cover the range from 0.2 to 1.5 ppm, the residual oleate concentration was measured using the spectrophotometric method described by Gregory (1966). The amount of oleate abstracted was calculated from the difference between initial and residual (equilibrium) concentrations.Figure 1 shows the floatability of FeCr2O4, FeAl2O4, FeFe2O4, MgCr2O4 as a function of pH and sodium oleate concentration of 1 x 10-5 M. The IEP of each sample is indicated in the figure by a vertical line in the horizontal axis. The chromium-bearing spinels FeCr2O4 and MgCr2O4 show the lowest isoelectric points (IEP), around pH 6, while in the case of FeFe2O4 and FeAl2O4, the isoelectric points lie at pH 6.5 and 7.3, respectively. It is seen that the flotation-pH curve for FeFe2O4 has a peak at the pH of the IEP, while flotation peak for FeCr2O4 appears at pH below the IEP and that of MgCr2O4 does at pH above the PZC. On the other hand, FeAl2O4 is floated at pH range between about 4 and 7,3 (IEP). This suggests that the pH value at which the maximum flotation occurs is dependent on the sort of spinel to be floated, though it appears in the vicinity of the respective IEP."

Jan 1, 2003

By K. C. Corin, M. S. Manono, J. G. Wiese

"It has been suggested that hydroxo species, particularly those of calcium, selectively adsorb onto gangue minerals. Such species enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the positively charged mineral surface and the negatively charged CMC molecule. Thus, the hydrophilicity of gangue minerals is enhanced, preventing the dilution of the concentrate. However, as there is little evidence to support these claims it is important to investigate. Adsorption data and mineral surface charge analyses will allow a fundamental understanding into how electrolytes and their ionic strengths affect gangue-depressant adsorption. It is strongly anticipated that decoupling these effects will allow process operators to tailor their process water quality needs towards best flotation operating regimes and in the long run effect closed water circuits. Thus, using talc and pyrrhotite as proxies, this work investigates the influence of the ionic strength of process water on the adsorption of CMC onto minerals in sulphide flotation.INTRODUCTIONThe phenomenon of gangue depression in mineral flotation is of critical importance as regards the attainment of a required concentrate grade. This thus suggests that the depressant of choice has to have a highly selective affinity for the targeted gangue minerals. This would ensure the necessary prevention of gangue from reporting to the concentrate without inadvertently depressing the value bearing mineral. The chemistry of the environment regulates the manner in which gangue depression occurs. In sulphide flotation, polysaccharides are used as depressants of choice to depress naturally floatable gangue which may in the case of Merensky ores exist as talc. The two widely used polysaccharides in the South African context are carboxymethyl cellulose (CMC) and modified guar gum. It is suggested that polysaccharides depress gangue by rendering the surface of gangue hydrophilic or by preventing the formation of hydrophobic layers on gangue mineral surface, forming large gangue aggregates and thereby increasing their heterocoagulative nature (Shortridge et al., 1999)."

Jan 1, 2018

By T. Inoue, K. Okaya

"Movement of mill charge in the centrifugal mill is essentially different from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. As proved e.g. in [11], this results in substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Back in 1983, Bradley et al. presented a model of the centrifugal mill based on the kinetics of the mill charge by regarding it as a lumped mass. On the other hand, numerical modeling by ‘discrete element method (DEM)’ enabled us to observe the movement of each ball in the centrifugal mill with an extremely minute time intervals (Inoue et al., XX IMPC in 1997). The former approach rendered simple, even though approximate, expression of the mill behavior, while the latter method was advantageous in describing the behavior of the mill in terms of individual events taking place in the mill body, even though the result did not reduce to a simple expression. The characteristics of the centrifugal mill described by both these approaches proved to be in a degree of agreement. Thus, the kinetic approach was capable of presenting the overall view of the mill, while the DEM model was informative of the details that could not be depicted well enough by the simple math expressions."

Jan 1, 2003

By F. v. d. Meer, G. Kretschmar, T. Mütze, T. Leißner

"Dynamic air classifiers separate particles in a gas flow due to different particle trajectories utilizing differences in the settling velocity of particles as characteristic property for separation. The present contribution takes a close look at the separation of heterogeneous mixtures, in which valuables and gangue minerals show significant differences in density. The focus was on a moist iron ore sample, which was characterized in terms of mineralogy, grain size distribution, and particle size distribution. The material was classified at a cut size of 45 µm and at feed moistures between 0 and 6 wt.-%. Additionally to standard characterization techniques, the moisture of both products was measured as well as the yield of fines as product fraction in a corresponding processing plant. In addition, an automated mineral liberation analysis (MLA) provided information of the enrichment and segregation of individual mineral phases in the products. The MLA of the classification products reveals a selective comminution of the mineral phases and especially on overmilling of the valuables. For the first time, the separation of individual mineral phases has been assessed and compared to the classic assessment of classification processes by means of particle size analyses. KEYWORDS Dynamic classifier, segregation, MLA, selective comminution INTRODUCTION Dynamic air classifiers separate particles in a gas flow due to the different trajectories of the particles. The result of such a separation process depends on the gas throughput of the classifier, the dimensions, design and rotational speed of the deflector wheel, as well as the state of dispersion and thus the geometry of as well as the turbulence and interparticle interactions in the separation zone. Air classification of moist feed materials can be divided into several sub-process (Leschonski, 1977; Mütze et al., 2016): - dosage of the feed material, - dispersing the solid feed material into a gas stream, - feeding the dispersed material into the classification zone by pneumatic conveying, - drying of moist particles during pneumatic conveying, - separation of coarse and fine particles, and - separation of fine particles from gas."

Jan 1, 2018

By M. Z. He

Attractive particle interactions which underpin the sliming of gangue mineral particles onto valuable mineral phases are encountered in a number of flotation circuits. Sliming leads to poor flotation recovery of the valuable minerals and high recovery of the gangue particles in the concentrate. To mitigate sliming, low molecular weight poly-electrolytes are commonly used as dispersants during pulp conditioning prior to flotation separation of the valuable and gangue mineral phases. In the present work, the sliming mechanism of sericite onto chalcocite and the influence of interfacial chemistry and two anionic copolymer dispersants (carboxylate substituted polyacrylamide, polymer Cyquest 3223 and sulfonate substituted polymaleic acid, polymer P80) on the sliming interactions were probed in the pH range 5~9. It was shown that the sliming occurred under solution conditions where both chalcocite and sericite particles were negatively charged, as evidenced by their apparent particle zeta potentials. The suspension pH had a profound effect on sliming process as the extent was markedly greater at lower than higher pH. The sliming was found to be due to the chalcocite dissolution, Cu (I) release and oxidation to Cu (II), followed by hydrolysis and specific adsorption, leading to sericite particle surface charge reversal and the formation of electropositive sites on chalcocite surface in the pH range 5~9. Addition of polymer Cyquest 3223 or P80 not only increased the magnitude of zeta potentials of both sericite and chalcocite particles but also reduced the formation of Cu (II) ions and complexes, which mitigated the sliming behaviour. The adsorption of polymer Cyquest 3223 or P80 at 3 g polymer / kg solid or more had a significant impact on the zeta potentials of both sericite and chalcocite particles. Sericite-chalcocite particulate adsorption studies showed that sliming was completely suppressed via an electro-steric repulsion mechanism resulting from anionic polymeric dispersant adsorption at dosages > 3 g polymer / kg solid.

Jan 1, 2014

By D. Steele, B. Ndlovu

"Adequate characterisation of clays is becoming increasingly important as operating mines move into areas of more complex ores. The processing therefore needs better mineralogical characterisation to identify problematic ores for better planning before issues arise. While a number of instrumental mineral characterisation methods are available, X-ray Diffraction (XRD) is widely recognised as perhaps the best technique for the identification and quantification of minerals, particularly clays. When an appropriate sequential and systematic sample preparation and treatment protocol is employed with instrumental XRD analysis individual clays can be uniquely identified, and the proportions of interstratified clays can also be quantified. The effect of sample preparation on the XRD analysis and identification of clays was investigated in this study. The results showed that sample preparation protocol is indeed critical to accurately analysis and characterisation of clays. For example, both dry grinding and micronizing affected the degree of crystallinity of kaolinite leading to the formation of reactive surfaces or changes in the physicochemical behavior. It was also found that the apparent degree of preferred orientation in platy minerals correlates directly with the amount of force/pressure applied during the preparation of backfilled powder samples. This work showed that manual preparation can produce highly variable peak intensities especially with minerals that show any preferred orientation. KEYWORDS Clay; XRD; kaolinite INTRODUCTION Clays are important in our life and they have numerous applications in modern world from cosmetics to environmental remediation. Therefore, clays have been extensively investigated for many years. Adequate characterisation of clays is becoming increasingly important as the mineral processing industry faces more complex mineralogy with the need for better mineralogical characterisation to identify problematic ores and plan accordingly. In most studies, X-ray diffraction (XRD) method has shown the unique capability to characterise mineralogy, especially for the fine grained size materials. The XRD technique is particularly diagnostic for clays. It is known that under ideal conditions, the peak intensities of an XRD diffractogram are proportional to the concentrations of individual minerals present in the sample. Hence, the qualitative mineralogical data obtained from XRD can be quantified, using either the internal or external standard methods. However, it is also known that clays are particularly sensitive to the influences of sample preparation method due to their physical characteristics (e.g. fine grain size, morphology, relative physical softness, crystallinity, thermal sensitivity) that could be destroyed by inappropriate preparation prior to the analysis. Thermal and mechanical treatment and grinding of clays can change their crystalline structure, and consequently, their characterisation results by XRD analysis. The behaviour of clays in grinding has been widely studied, especially for kaolinite (Miller and Oulton, 1970, Milocevic et al., 1992, Tomasevic-Canovic et al., 1992). With prolonged grinding time, the crystallinity of the clays can decrease (Filipovic-Petrovic et al., 2002). It has been shown that grinding may gradually cause the loss of hydroxyl ions of kaolinite (Gonzalez Garcia et al., 1991)."

Jan 1, 2018

By D. Tang

The froth zone in a flotation cell is recognised as a region which contributes to the overall flotation performance. Froth recovery is a measure of the efficiency with which the froth phase delivers particles arriving at the pulp-froth interface to the concentrate. Poor froth recovery in scavenger stages is generally attributed to poor froth stability. The key indicators of froth performance: froth recovery, entrainment and water recovery were measured in an OK3 pilot cell installed at a zinc concentrator in Australia and supplied with scavenger feed. Cell hydrodynamic and pulp chemical conditions during the operation of the cell were also measured as well as bubble growth across the froth phase. The objective of the work was to assess the impact of a number of commercial frothers on the froth performance in the OK3 cell and assess the suitability of using bubble growth as an indicator of froth stability.

Jan 1, 2014

By Chanki Jeong, Heechan Cho

In this study, batch flotation experiments were conducted to recover rare earth elements (REE) from an REE ore deposit in the Mushgai Khudag area, Mongolia. Apatite was found to be the major REE mineral while monazite and xenomite were observed as minor minerals. The main purpose was to float apatite to increase the REE content. Oleic acid was used as collector and MIBC was used as frother. Sodium silicate was used as a depressant for iron compounds. NaOH was used to adjust the pH of the flotation to about 9.5~10.0. The particle size was 90% less than 152 ?m (- 100 mesh). The content of REE elements was analysed by ICP - OES to determine the contents of REE such as Ce, La, Nd, Pr and Y. When sodium silicate was used, the best result was obtained using 0.2 mL of sodium silicate, 2 mL of oleic acid and 2 mL of MIBC. Under these conditions, the recovery of REE was about 78% and the grade of the first froth product was 42,995 ppm Ce, 24,088 ppm La, 14,236 ppm Nd, 4,388 ppm Pr and 1,570 ppm Y. When conducting flotation after iron minerals were removed by magnetic separation, a better result was obtained; with 2 mL of oleic acid, 2 mL of MIBC and no sodium silicate, the recovery was increased to 90% and the grade was also increased to 58,600 ppm Ce, 28,624 ppm La, 17,160 ppm Nd, 5,348 ppm Pr and 1,971 ppm Y.

Jan 1, 2014

By E. V. Zelinskaya, A. E. Burdonov

"In the raw aluminum production processon electrolyzers with self-baking anodes, during technological operations, flow-regulated treatment and adjustment of the electrolyte chemical composition produced by diesel and floor-rail technology, alumina and fluoride salts are spilled through the ventilation grilles of the electrolysis body aeration channels, leakage in the equipment, machinery and motorized machinery construction elements. As a result of this, a part of the bus station and the level of ± 0 (the basement room with supporting curbstones and columns, on which electrolyzers are installed) are covered with technological raw material. This leads to an increase in the conductor (bus) resistance, contact connections deterioration, cell insulation failure and raw materials loss. For example, at the enterprise ""Rusal-Bratsk"", as a result of the activity, up to 420 tons per month of alumina-containing wastes that are unfit for use in the electrolysis process are formed due to the alumina substantial contamination with salts of iron and silicon, which significantly reduces the technical and economic parameters of the electrolysis process. The main scientific problem is the processing (cleaning) of alumina-containing waste having a complex mineralogical composition of the material, its contrast and structure, from oxides of iron and silicon, using ""dry"" separation methods. In the performing the work process, qualitative indicators of the influence of external factors (air humidity, precipitation, sunlight, temperature difference) on the physicochemical processes components interaction during the raw materials storage are established. On the basis of laboratory tests, it is established that alumina-containing raw materials can be separated and photometric and gravitational separation methods used. A mathematical model of the motion of particles of primary and prepared alumina-containing raw materials in a cascade-gravity classifier was developed. The criteria and factors characterizing the alumina-containing material, as well as influencing and determining the maximum material enrichment, are established."

Jan 1, 2018

By Arkady Senchenko, Andrey Vasiliev, Alexander Aksenov, Metodi Zlatev

"This paper considers the issue of treating argillaceous oxidized ores with low gold grade (around 1.0 g/t). These ores according to their gold recovery level can be treated by heap leaching and agitation cyanide leaching, but low gold grade makes this treatment uneconomic. Heap leaching of argillaceous ores requires high consumption of binding agent for pelletizing to create suitable hydro-physical properties of material, which leads to increasing process cost and makes the material treatment unprofitable. Agitation cyanide leaching of this ore requires grinding processes; these expenses would not be paid back by the amount of gold recovered. Considering the above, poor argillaceous oxidized ores are recommended to be treated according to a combined technology including fractionation of ore, heap leaching of coarse fraction and agitation leaching of argillaceous fraction. Complex approach application allows one to avoid expenses incurred for material grinding and high consumption of binding agent for pelletizing. The success of this technology implementation will firstly depend on the quality of material fractionation, therefore the section of disintegration and division of ore into different components will be the most important part of flowsheet development for gold production. When disintegrating minerals at positive temperatures both standard (mechanical disintegration - scrubbers) and innovative (hydraulic method of disintegration - HydroClean units) equipment is applicable. HydroClean units are characterized by lower energy and water consumption. In a number of cases it is required to treat frozen ores. When treating frozen material standard approaches to disintegration are not reasonable due to their low efficiency. In order to treat frozen material a two stage disintegration flowsheet with screening after each stage is recommended. The first stage is recommended to be performed in a scrubber, the second - in a HydroClean unit. This technological flowsheet will provide high and steady values for ore separation into fractions at low energy consumption for disintegration."

Jan 1, 2014

By Hristo Stanchev, Veselin Mehandzhiyski, Sashka Kozhuharova, Stefan Stamenov, Alexandar Penchev, Nikolay Nestorov, Velika Stamatova, Ekaterina Todorova

"This article presents the results of comprehensive research on the quantitative distribution of gold content in the raw ore and tailings from the flotation enrichment process at the Ellatzite Med plant. The study is a quantitative and qualitative determination of the presence of gold in the ore processed by Ellatzite Med AD, as well as its behavior and distribution in the various metallurgical products of the flotation process. The representativeness of the samples taken is ensured by the frequency of sampling: four work shifts of sampling on different days within a period of four consecutive weeks. The form of gold present is determined both in the analyzed samples and in separate fractions - granulometric, magnetic, electromagnetic, heavy and light. A summarized diagram presents the phase distribution of gold in the final products of the dressing process. The results obtained are used for further analysis and evaluation of the actual technological parameters of the gold. It was established that an increase in the initial gold content, respectively in the content of native gold in the raw ore, with the current process, leads to an increase in gold losses, mostly in the native gold phase. The conducted analysis of the results from the comprehensive tests on determining the form of gold present in the various enrichment products gave rise to further research with the use of a Knelson centrifugal concentrator."

Jan 1, 2014

By Gülay Bulut, Ferihan Göktepe

Pyrite is the most abundant and widespread sulphide mineral and its flotation has been investigated by many researchers. It is well known that, pyrite is floatable under acidic conditions and recovery drops with increase in alkalinity due to changes in solubility of iron hydroxides on the pyrite surface. Most of the works also revealed out that pyrite displays variable behaviour in flotation circuits. This behaviour mainly related with origin and mineralogical composition of ore, liberation size, electrochemical behavior of minerals constituting ore, the trace and minor element content of the mineral, texture, application variables belonging to flotation circuits. In this study, copper activation effect was examined on different origin of pyrites. The experiments were performed with five high grade samples of pyrite from the different mining districts of Turkey. The pyrite samples were different from each other with respect to either their physical or chemical properties; they were different physical appearances and contained different associated minerals. In the micro-flotation tests, 1x10-4 mole/L copper sulphate and 1x10-4 potassium ethyl xanthate were used as flotation reagents. First of all pyrite samples were floated using only xanthate at different pH. Results showed that best floatation results obtained at acidic pH range for all pyrite samples. When copper ions were used to activate, all pyrite samples floated at neutral and basic pH values, too but depending on the samples, recovery and pH ranges were slightly changed.

Jan 1, 2014

By Kevin Davey, Liza Forbes, Leanne Smith

Given the global scarcity and value of potable water, interest in the use of water of lower quality in mineral processing has grown significantly in recent years. Previous laboratory batch flotation tests conducted at CSIRO have shown that chalcopyrite floats strongly without collector in distilled water and that the collectorless flotability of chalcopyrite is unaffected by the use of brackish water, sea water or hypersaline water. In contrast, bornite is moderately flotable without collector in distilled water but all three lower-quality waters have a detrimental effect on the recovery of bornite. The depressant effect is so strong that the little recovery achieved in these waters was only slightly above what might have been expected from entrainment alone. This work has now been extended to another important copper sulfide mineral, chalcocite. In contrast to chalcopyrite and bornite, chalcocite does not exhibit collectorless flotability so the chalcocite tests in this study were performed in the presence of a standard collector (potassium ethyl xanthate). The results reveal that chalcocite is flotable with xanthate in distilled water but the lower-quality waters have a detrimental effect on the recovery of chalcocite. This effect is partly reversed by increase collector additions. Further tests were completed in order to investigate the effect of the different ions present in the saline waters on chalcocite flotation. Possible reasons for the observed differences are discussed in terms of the pulp chemistry of the system.

Jan 1, 2014

By C. H. Zhou

Cryogenic grinding of Printed Circuit Board will bring less pollution, reduce energy costs, smaller particles, regular particle size, efficient process, separation various materials due to different fracture toughness. Systemic studies of recycling discarded Printed Circuit Board (PCB) by low-temperature modification and cryogenic grinding have been made in this paper. Firstly test mechanical property of PCB at different low-temperature, including impact strength, flexural strength, and shear strength. Do experiment on the power consumption of different cooling temperature, The results show that the average power consumption is lower between -30? to -60? and the average power is decrease in evidence at -30?. Use ZKB type double roll shear crusher to crush PCB to 20mm×20mm particle size, in a temperature range of -10 ~ -30? Used R type mill to grind sample to minus 3mm under different working condition, the average power consumption is decrease in evidence from -10 ? to -30 ?, power consumption is the lest at rotational speed is 1180rpm.

Jan 1, 2014