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"The effect of operational conditions, such as air flow rate, impeller speed and solid concentration, as well as the effect of solids concentration and frother dosage, on the bubble size distribution produced in a lab scale flotation cell, were investigated. The cell was operated under batch conditions. The measurement of bubble size was accomplished using an automated photographic technique. The technique enabled fine and coarse bubble distributions to be measured in two-phase (liquid-gas) and three-phase systems (solid-liquid-gas). In each experiment, around ten thousand bubbles were characterized.This paper discusses the main results obtained using the new photographic technique and compares these with previous findings available in the literature. The results indicate that photographic techniques combined with digital imaging processing might become a standard technique for measuring bubble size distribution in flotation machines.HUT BUBBLE SIZE ANALYSERThe importance of having precise and reliable equipment for measuring bubble size distribution in industrial flotation machines has been widely recognized. The measurement of bubble size, particularly in three-phase systems, is rather complex due to the opaque nature of the pulp. However photographic techniques combined with ingenious sampling techniques are utilized for overcoming this difficulty. The technique named HUT, combines previously developed visualization methods with digital image processing procedures. In this technique bubbles and aggregates are exposed to a monochrome progressive scan camera. The acquired images are directly stored in a computer connected to the camera for post-processing. The sampling apparatus consists essentially of a vertical tube for collecting bubbles, a viewing chamber and a collection chamber, where particles carried by the bubbles are released. The function of the collection chamber is to maintain the viewing chamber clear for imaging purposes. Each image is automatically processed off-line, using digital image tools. In this paper the advantages and limitations of this new technique are described."

Jan 1, 2003

By T. A. Penzov

As a result of recent scientific and experimental studies new technical devices have been developed for monitoring and control the process of grinding. The description of microprocessor module MILLCONT 1 for control of the loading of the mill and microprocessor density control module DENSIMETER is given in the paper. The improved variant of the automatic system for ore grinding control in single-stage ball mill working in close cycle with a classifier with above mentioned technical means is shown in the paper. The loops for measuring and stabilization of the basic technological parameters (density of the ready pulp ? and fineness of grinding of the pulp ß) are described in the paper. The nowadays economic results in ore grinding process automation are given as well.

Jan 1, 2014

By Luís Marcelo Tavares, Juliana Segura

Comminution is one of the most energy consuming stages in a mineral processing plant. This consumption is not only related to the power supplied to equipment, but also to the indirect or embodied energy, mainly associated to materials that are worn during operation, including grinding media and liners. Until recently, preparation of iron ores in Brazil did not use comminution intensively, given that plants mainly produced sinter feed, natural pellet fines, besides lump ore. However, with decreasing ore grades, size reduction now occupies a centre stage in nearly all new plants. Technologies used up to date for processing low-grade iron ores in Brazil, in particular itabirites, have consisted of three or four stages of crushing followed by ball milling. A number of new plants are either being built or are currently being designed that will process the same type of ore, so that engineers are investigating alternative comminution routes. The paper analyses comparatively four comminution routes for processing a particular itabirite ore, many of which using technologies and layouts that have not yet been used in such application. Using data from bench scale and/or pilot-plant tests, the different routes are compared on the basis of sustainability principles in accordance to the Brazilian energy matrix, which is quite particular. It is concluded that if the sustainability criterion is used, then the optimal route would correspond to a circuit that uses HPGR technology with truncated feed followed by ball milling. Given the particular case of itabirite iron ores and specially to the one in the present work and the source of Brazilian energy, it is evident that indirect energy expenditure in comminution plays a significant role in greenhouse gas emissions when compared to direct energy, being the reason for the great attractiveness of HPGR technology. Evidently that these will have to be balanced against CAPEX, OPEX, NPV and other qualitative criteria, which can certainly lead to a different optimal circuit.

Jan 1, 2014

By C. Raghu Kumar

Hydraulic or teetered bed separators (TBS) are finding new avenues for application in the field of mineral processing. Floatex Density Separator (FDS) is a hydraulic/teetered bed separator capable of operating at high tonnage due to its advanced instrumentation. FDS/TBS is being used in Indian mineral sand industry for classification and segregation of different minerals. The purpose of this paper is to provide details on the performance of the plant scale FDS in recovering the chromite from feed (below 1mm size). Historically this feed has been processed using hydrocyclones and spiral classifiers; however, there is a strong trend now to employ teetered bed separators, thus allowing significant changes to be made in the plant for improving process efficiency. In the present work, the performance of the plant scale FDS is described in terms of partition curve (yield, cut size, classification efficiency/Ep) for different combination of process variables and also in terms of metallurgical grade and recovery. It is found that, efficient classification can be achieved at a maximum cut size of 380 µm with and the imperfection is also reported as low as 0.16. The grade of the underflow product is enriched as maximum as 52.2% Cr2O3 from a feed assaying 40.4% Cr2O3.

Sep 1, 2012

By Alan Bax, John D. Lewins

"Platinum Australia Limited (“PLA”) is currently undertaking a Feasibility Study into the development of the Panton Platinum Palladium Project located in the Kimberley region of Western Australia. The Panton Intrusive is a layered, differentiated mafic to ultramafic structurally complex body that has undergone numerous folding and faulting events. This has resulted in a southwesterly plunging synclinal structure some 10 kilometres in length and 3 kilometres wide.High grade PGM mineralisation is hosted within a number of stratiform chromitite reefs within the ultramafic sequence. The focus of the Feasibility Study is on the Top Reef which is situated approximately 150 metres below the mafic/ultramafic interface. The average true width of this reef is approximately 1.2 metres and the reef has a defined resource is 10.1 million tonnes at an average grade of 6.1 g/t PGM + Au.The Palladium to Platinum ratio of the Top Reef is approximately 1.15:1 and the reef also contains an average of 0.4 g/t Au and 0.3 g/t other PGM’s. The Panton ore is considered refractory in nature and standard flotation techniques achieve a PGM + Au recovery of less than 65% with a concentrate grade of less than 100 g/t PGM + Au. As part of the Feasibility Study Platinum Australia in conjunction with their major shareholder Lonmin Plc developed a new metallurgical process which has achieved an overall PGM + Au recovery of approximately 80% into a high grade PGM concentrate which is suitable for feeding direct to a PGM refinery.THE PANTON PROCESSThe Panton Process incorporates a two-stage Milling and Flotation circuit with no cleaning stages to produce a low grade, high recovery flotation concentrate. Typically the concentrate mass constitutes 25% of the feed and has a PGM + Au grade of 25 g/t.This low-grade concentrate is subjected to calcination in a rotary kiln or fluid bed at a temperature of approximately 400 0C for a period of 60 minutes. This step is designed to render the platinum minerals soluble in cyanide and both the temperature and the duration of calcination are critical to the efficiency of the leaching process."

Jan 1, 2003

By F. C. Yi

Discontinuous and consecutive process was applied to probe into the Kinetics and adsorption theory for Cs+ adsorbed by Zeolites under the conditions of temperature, time and fixed-bed dynamic adsorption. It indicated that the sorption kinetics behavior of zeolite?s sorption on Cs+ is ac-cord with pseudo-secondary velocity equation, velocity constant k2=0.0005213 g?mg min-1, and equilibrium adsorptive capacity is 147.0588 mg?g-1; The equation can be expressed as: Y=0.0068X+0.0887; From the analyzing of diffusion coefficients on different temperatures and times, the coefficient of diffusion is not only related with the fabric of mineral and the character of ions but also the temperature and time; When the ambient temperature hoisted, the diffusion velocity augmented rapidly; Cs+ would get over a certain energy barrier when it enters into structure of zeo-lite; This energy is expressed by activation energy, and its value is E=131.668818 kJ?mol-1; There are two dominating adsorption mechanisms in the system of zeolite absorb Cs+: ionic interchange and surface coordinate adsorption.

Jan 1, 2014

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, M. Zare

High Pressure Grinding Roll (HPGR) plays a major role in increasing specific surface area of iron ore concentrate for producing pellet feed. HPGR grinding mechanism implies that material be compressed between the two rolls, therefore layer of material must be able to resist required pressure for achieving suitable grinding conditions. In this study for determining a simple relationship between material pressure resistance ability and HPGR main design parameters, piston press tests were performed on different iron ore concentrate samples along with HPGR Blaine increasing tests. Piston press tests results showed that by decreasing moisture content, material pressure resistance increased and in constant moisture content this parameter will change based on material specifications. HPGR Blaine increasing tests results showed that by decreasing moisture content, HPGR specific throughput and working gap increased and in constant moisture content this parameter will change based on material specifications. For all of the studied samples at worst condition, we got the results including: HPGR delta gap equal to zero, specific throughput lower than 200 ts/hm3.According to the tests results, HPGR Applicability Index (HAI) can be introduced at four different class types from 1 (weak) to 4 (excellent). This index determines achievable specific throughput and possibility of using HPGR according to material specifications, i.e. for HAI 1-4 the pressure resistance is <90, 90 to<125, 125 to <150 and = 150 bar, respectively. Similarly for HAI 1-4 specific throughput is <200, =200, =220 and =250, respectively. So based on design moisture content, if concentrate HAI is 3 or 4, HPGR is a correct choice. For HAI 2, HPGR can also be used. But for a material with HAI equal to 1, HPGR is not a good solution. As a result in order to apply HPGR for HAI 1, material condition such as moisture or slime content should be decreased.

Jan 1, 2018

By S. S. Yu

In this paper, the producing process of using V2O3 as raw material to obtain vanadium nitride was analyzed through the means of thermodynamic. The analysis shows that conversion follows the principle of reduction step by step in the conversion process of V2O3. The temperature of the reaction system has prominent influence on the nitrogen content of products, and the reaction is very sensitive to temperature. As raising temperature, the fine grain structure of the nitrides is more evident, and the grain size of nitrides increases. At 1703K, the nitrogen content of the products tended to be constant after soaking over 3 hours.

Jan 1, 2014

By P. Knüpfer, B. Babel, M. Rudolph, F. Perez Maldonado, U. A. Peuker, L. Ditscherlein

"In heterocoagulation processes for the separation of mineral particles, the most famous being froth flotation, the main characteristic of separation is a differing wettability of the constituents to be separated. This most crucial property in the economically important process of flotation is often only and incompletely, quantitatively described in terms of contact angles against water. A water contact angle larger than 90° is referred to as hydrophobic and hydrophilic vice versa. Looking at Young’s equation shows that it is actually the surface energy of the solid in interaction with the surrounding phases and their surface energies (or surface tensions for liquids) which describes whether there will be hydrophobic/hydrophilic hydration interactions leading to attraction or repulsion. This, we have previously published for various more or less hydrophobic minerals in correlation to their flotation response, i.e. flotability (c.f. Rudolph & Hartmann, Coll.Surf.A 513, 380-388). In the same paper we also discussed the heterogeneity of wettabilities as assessed with the novel method of inverse gas chromatography. Furthermore we have also reported on hydrophobic force distributions as assessed with atomic force microscopy which are as well due to wettability heterogeneities (c.f. Fritzsche et al., Coll.Surf.A 459, 166-171).In this paper we present wettability distributions of different substrates and particles with various surface roughnesses/shapes and degrees of hydrophobization as assessed with iGC, AFM and dynamic sessile drop analyses. We are putting the results in context in unifying models and present methodologies helpful to make use of the fundamental information and their impact on the actual industrial separation process in fundamental process models. Besides froth flotation we also emphasize the impact on selective hydrophobic flocculation process."

Jan 1, 2018

By Ghislain Bournival, Cagri Emer, Seher Ata

"It is well known among flotation practitioners that the contact angle can be correlated with the amount of material recovered from feed by flotation. The contact angle of solids can easily be modified by the addition of a collector. However, some collectors also have frothing properties thus altering the solid and bubble surface properties simultaneously. To avoid this problem, a technique has previously been used in which silanol groups are attached to the surfaces of the particles, but this method has its own problems. In this work, silica particles with various surface hydrophobicities were prepared using an esterification process. By using alcohols with different hydrocarbon chain lengths, from 4 to 12 carbon atoms, surfaces with a wide range of contact angles could be prepared. The technique was used in the modification of silica particles that were tested in a fluidized bed flotation column, and a laboratory mechanical flotation cell. In parallel experiments, dodecylamine (DDA) was used as a collector. It was found that irrespective of the type of flotation machine and surface preparation method, there was a close correspondence between flotation recovery and the contact angle of the particles. The silanation process has known drawbacks relating to the presence of moisture during the reaction, and the stability of the silane coating after it is been prepared. Esterification does not suffer from these disadvantages. This work has shown that the esterification technique is a robust alternative method for preparing hydrophobic quartz surfaces."

Jan 1, 2014

By V. A. Chanturiya

The state-of-the-art of mineral mining and metallurgy industry in Russia is characterized by high demand of nonferrous, rare, rare earth metals, and highgrade coal, on the one hand, and by involvement of natural and technogenic minerals with low content of valuable components, fine (nearly emulsion) dissemination of valuable components and close physicochemical and process properties. This calls for high-productive and ecology-friendly technologies for more efficient mineral beneficiation based on intensification of operating and new methods to extract valuable components from rebellious ore and technogenic minerals, relying on the last achievements of basic sciences, combination of dressing and chemico-metallurgical processes and using advanced pyro- and hydrometallurgical technologies. The transition to a new strategy of processing is only possible based on the new technological–mineralogical appraisal of a mineral raw material. Actually, the process mineralogy has a stock of modern high-resolution physical methods for analyzing composition, structure and properties of geomaterials, inclusive of micro- and nano-levels: - Identification of micro- and nano-size noble metals, and natural and induced formations on mineral surface; - Experimental validation of structural phase and chemical transformation of minerals under different energy input; - Justification of choice and mechanism of interaction between flotation agents and noble metals with complex material constitution; - Analysis of structural, phase and chemical transformations of sulfides and rocks under leaching. Thus, process mineralogy is an informational background for a unified theoretical approach to scientific justification of flowsheets of efficient mineral processing. The article gives a brief review of practices that have found application and proved to be of high economic efficiency. Such practices are: X-ray radiometry and photometry separation (Uchalinsky and Gaisky Mining and Processing Integrated Works of ALROSA); selective disintegration (equipment engineered by Mekhanobr-Tekhnika and IPKON RAS); process selectivity enhancement (IPKON RAS, Central Research Institute for Geological Exploration of Nonferrous and Noble Metals, Chinakal Institute of Mining, Siberian Branch RAS, etc.); bacterial gold leaching (Olimpiada MPIW, technologies developed the Central Research Institute for Geological Exploration of Nonferrous and Noble Metals, Nezhdaninsky deposit projects, etc.); combination processing at a mining and metallurgy plant (Norilsk Mining and Metallurgical Company, Yaregsky deposit projects and others); processing of waste: overburden, mill tailings, slag, etc. (Kovdorsky MPIW, Svyatogor JSC, Ural Mining and Metallurgical Company, plants designed by the Central Research Institute for Geological Exploration of Nonferrous and Noble Metals, Mining Institute of Kola Science Center RAS, Research Institute for Chemical Technologies); water conditioning in mineral dressing circuits (ALROSA, equipment by IPKON, etc.); utilization of process water (ALROSA, Ural Mining and Metallurgical Company, Severalmaz JSC and others). Thus, Russia this time has the academic and engineering background for development of efficient energy-saving technologies for comprehensive advanced processing in accordance with the world’s standards, or even higher in terms of a number of the technologies, which has continually been highlighted by participants of recent international congresses on mineral processing.

Jan 1, 2018

By Arkady Senchenko

The application of centrifugal separation methods with the use of gravity concentrators has been assigned high priority while gold-containing minerals processing. The separation proceeds under centrifugal force resulted from the rotor spinning and wash water flow in the concentrators. The high specific gravity particles are retained at the trapping surface of the cone, and the low specific gravity particles are brought in the tailings. The centrifugal field in such concentrators (Knelson, Falcon) is generated by the rotating cone provoking the swirling of the free fed slurry flow. The author investigated the regularities of the separation process in the centrifugal gravity concentrator where a two-phase flow of the separated mineral media is under the pulsed pressure of the fluidization water and air. As a result of the study the possibility of the deeper penetration of the fine heavy fraction into the cone rings, providing the fluctuation of the fluidization water or air flow, was theoretically argued and experimentally proved. This allows the increase of the separation performance at low pulsation costs. The developed mathematical models are in close conformity with the actual process of interest and they enable the prediction of the heavy phase behavior at the isolated process stages in the concentrator. Keywords: gold, centrifugal gravity concentrator, containing, specific gravity, cone ring, pulsation, cost, fluidization water, Knelson centrifugal separator

Sep 1, 2012

By Seungwoo Park, Gaurav Soni, Roe-Hoan Yoon, Hyunsun Do, Kaiwu Huang

In a flotation froth (and foam), air bubbles become larger due to coalescence, causing bubble size to increase, bubble surface area to decrease, and hence casing less hydrophobic particles to drop off to the pulp phase below. Thus, bubble coarsening provides an important mechanism by which product grades are increased. On the other hand, excessive bubble coarsening results in low recoveries. In the present work, a model describing the process of bubbles becoming coarser in a foam as they rise to the top by deriving a mathematical relation between the Plateau border area, which controls film drainage rate, and the lamella film thickness, which controls bubble-coalescence rate. The model has been derived by assuming that liquid drainage rate increases due to slip at the air/water interface, and that the critical rupture thickness is determined by the capillary waves created by thermal motion. The model developed in the present work can predict the bubble size ratio between the top and bottom of a foam as functions of aeration rate, foam height, and surface tension (frother dosage). The model predictions are in good agreement with the changes in bubble sizes measured using a high-speed camera.

Jan 1, 2014

By C. Abbruzzese, F. Vegliò, S. Ubaldini, R. Massidda

The aim of this paper was to study the influence of different water/organic solvent mixtures (isopropyl alcohol, ethanol and ethylene glycol) on the gold desorption process. The experimental work was carried out on laboratory scale, using activated coconut carbon with different temperatures and extraction times, without adding cyanide. Best results have been obtained in this order: isopropyl alcohol > ethylene glycol > ethanol. Starting from gold concentration of about 5 g Au per kg of carbon, best kinetics resulted in 97-100% of gold extraction, after 8 hours of desorption, at a temperature of 80ºC.

Jan 1, 2003

By V. V. Trusova, Shiyrav Gandandorzh, K. V. Fedotov, V. A. Domracheva

"In Russia, 1.1 million tons of mercury-containing waste are stored. The amount of mercury in soils and heaps of industrial enterprises is estimated at 3000 tons; in dumps, concentration tailings, sludge dumps of the gold mining industry up to 6000 tons have been accumulated. Mining is one of the main sources of mercury emissions in the natural environment that poses a real threat to the natural environment. At present, the process of amalgamation is prohibited and not applied in gold extraction. The application of amalgam technology in gold mining led to the accumulation of highly toxic products in the form of gold-bearing amalgam and metallic mercury, with a mercury content of dozens and even hundreds of times greater than the maximum permissible concentration for soil (1). Therefore, mercury-containing tailings constitute an ecological hazard to the environment. According to published data, at waste storage sites of industrial enterprises, up to 50 tons of mercury enter soil annually, and up to 3.5 tons pollute the air. At the same time, mercury-containing waste due to the reduction of the country's mineral resources is an additional source of mercury. Therefore, it is necessary to recycle mercury-containing waste. INTRODUCTION Paperobjective: demercurization of technogenic raw materials (amalgamation tails, discharge outlets of tailing dumps) to be recycled. Under natural conditions, the mercury usually migrates in the form of three most common compounds: elementary mercury (Hg); mercuric mercury ion (Hg+2); methylmercuryion (Hg (CH3) +. Chemical compounds Hg (II) are found in natural conditions much more often than Hg (I).The authors propose to conduct demercurization of technogenic raw materials (mercurial tailings) in two stages. At the first stage, the mercury in the form of small balls, the finest particles (drip mercury) can be extracted by applying the gravitational method. We propose a method for centrifugal processing of crushed waste in the apparatus of Itomak company, Novosibirsk, as the basis of the technological process for mercury recycling. The extraction of metallic mercury out of mercury-containing waste into commercial products, according to the technological characteristics of the Itomak apparatus, reaches 86.0% (2, 3). At the second stage, the extraction of mercury out of technogenic raw materials is performed applying a sorption method and using carbon sorbents based on fossil coals. Hard coal of the Kuznetsk Basin has been already used for industrial production of active carbons (carbon sorbents) of the KAD-iodine type, which is one of the prerequisites that determine the choice to use it for the aims of this study."

Jan 1, 2018

By Kr. J. Dedelyanova

Selective flocculation of iron minerals could improve the economics of high intensity magnetic separation as concomitant process. When the minerals are finely disseminated is necessary a finer grinding to be applied which generates a lot of slimes. The HIMS is not enough efficient for particles below 20 microns ? territory where the selective flocculation is already well known industrial practice, so the combination of these two methods of beneficiation can bring a higher grade at high recovery to be achieved. The dynamics and selectivity of the precipitation process is studied in batch tests with flocculant starch and dispersants sodium silicate and sodium hexametaphosphate. The influence of preliminary conditioning with nitrogen acid at pH 2 before flocculation is also investigated. Flowsheet including these two methods is tested and the distribution of iron is shown.

Jan 1, 2014

By E. V. Manlapig, M. C. Harris

"The complexity of the flotation process has made the identification of an appropriate model structure for the predictive simulation of flotation circuits far from obvious. Work performed under the auspices of the AMIRA P9 flotation program has indicated that the metallurgical performance achieved from a flotation cell arises from the interaction of two essentially independent property classes, namely the cell operating conditions and the properties of the cell feed stream. These observations have led to the development of a model structure that associates a constant set of flotation parameters to the streams of the circuit, which are transformed into a flotation response depending on the operating conditions within the flotation cell.A variety of alternative model structures exist within the literature which do not make this distinction between cell and stream flotation properties, and many of these models are in widespread use for flotation optimisation and design studies, both in industry and academia.In this paper, circuit survey and laboratory batch flotation data collected from an industrial flotation circuit are analysed. The data demonstrate that streams in an industrial flotation circuit exhibit varying particle floatability – concentrate streams typically float faster than tailing streams (Figure 1(a)). This floatability, however, is generally conserved around the various units within the flotation process (i.e. the effective floatability of the combined feed and product streams of a unit is equivalent (Figure 1(b)))."

Jan 1, 2003

By E. Pourjenaei, P. Ghobadi

High Pressure Grinding Roll (HPGR) is efficient equipment in comminution process. HPGR could be a good option for preparing ball mill feed at the first stage of grinding due to its high efficiency and low energy consumption. Closing with a screen, these mills are utilizing as one of the principle parts in mineral processing industries, especially for iron ores. Recently, HPGRs are working as primary mills at 4 developing lines in Gol-e-Gohar Iron Ore Processing Complex, Iran. Different mechanism of particle crushing in compare to the other tumbling mills makes the HPGR as certain equipment with its own particular controlling parameters. Hydraulic pressure, roller speed and level of material inside feeding hopper are the most important variables influencing grinding efficiency of the HPGR. To figure out how they impress the process and operation situation, different industrial tests were carried out and the best result (d80 about 8 mm for HPGR discharge) was achieved at 180-190 bar pressure (P), 300 rpm speed (S) and 50% of hopper level (L). It is worth noting that this finding has been observed through past pilot test too. We also used design expert method (DX7 software) to develop the best design and analysis the test results, as well. According to the mechanical restriction of HPGR and process limitation in the plant (based on the industrial results), we adjusted value of each parameter in a logical range. Therefore, 20 industrial tests were conducted, as DX7 recommended, and the various impacts of the parameters and their interaction were identified based on statistical analysis. As the authors expected, it was revealed that after presser, roller speed is a critical variable because of its significant role in residence time of the particles between the rollers. The function below has been determined to explain the relation between different parameters and the response.

Jan 1, 2018

By John A. Rumball, Martin R. Houchin

"For gold leaching of oxide ores, the optimum cyanide : oxygen ratio is approximately 106 mg/L NaCN : 10 mg/L O2 (6.9:1 by mole). In sulphide ores, galvanic coupling of the gold with the electrically conductive sulphides significantly increases this ratio such that leaching may occur in a relatively low dissolved oxygen (DO) environment.RESULTS AND DISCUSSIONGold leaching in a carbon in pulp (CIP) and carbon in leach (CIL) circuit is driven by the supply of cyanide and oxygen, as described by Elsner’s equation (1):• 4Au + 8CN- + O2 + 2H2O ? 4Au(CN)2 - + 4OH- (1)Equation 1 suggests that the ideal molar cyanide : oxygen ratio should be 8:1, or 122.5 mg/L NaCN to 10 mg/L of DO. It is generally accepted however, that oxygen is not completely reduced to hydroxide at the gold surface, and that equation (2) better represents the gold leaching reaction (Marsden and House, 1992):• 4Au + 8CN- + 2O2 + H2O ? 4Au(CN)2 - + 2OH- + H2O2 (2)Additionally, since gold leaching is limited by either the diffusion of cyanide or oxygen to the gold surface (Habashi, 1993), then the relative diffusion rates of cyanide and oxygen must also be taken into account. Marsden and House (1992) suggest that the ideal molar cyanide : oxygen ratio is 6:1, while a more recent investigation using laboratory and plant observations (Heath and Rumball, 1998) suggested a molar ratio of 6.9:1.In practice, although a cyanide : oxygen mole ratio of 6.9:1 applies to some circuits, there are many instances when this is not the case.In sulphide ores, galvanic coupling of the gold with the electrically conductive sulphides significantly increases this ratio. Galvanically connected sulphides, and possibly carbon, provide a large surface area for oxygen reduction. As the cathode surface area increases, the oxygen concentration required to sustain the same rate of gold oxidation decreases proportionately.Galvanically connected particles may be composite particles, however they may simply be liberated sulphides in the same suspension as the gold. Particle collisions within a slurry are sufficient to provide momentary galvanic connection (Greet, 1995)."

Jan 1, 2003

By S. S. Lu

In sodium oleate and salicylhydroxamic acid systems, sequence of floatability of three sulfate minerals is: barite>celestite>gypsum, in lauryl amine system is: gypsum>celestite>barite. XPS and infrared spectrum analysis are used to find that it is chemical reaction between sodium oleate and three minerals, physical adsorption on the surface of minerals for lauryl amine, and it is chelating reaction between salicylhydroxamic acid and three minerals possibly. Theoretical calculation on chemical bonds in crystal structures of three minerals is carried out, finding that breaking degree of Mn+?O2- in crystal structures of three sulfate minerals is closed related with floatability.

Jan 1, 2014