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Calcium sulfate whiskers are considered to be a prosperous reinforced material in application due to their high mechanical properties. But the hydration occurs easily at moist atmosphere or in aqueous solution. The surface topographies of the calcium sulfate hemihydrate whiskers and the hydrates were analyzed by on-line observation and using XRD. The results indicated the transformation of the crystal type and shape of calcium sulfate hemihydrate whiskers and the reduction of whiskers? aspect ratio. The hydration process of the calcium sulfate hemihydrate whiskers and the effective parameters were further discussed based on FT-IR measurements. The conclusions were obtained that the hydration of calcium sulfate hemihydrate whiskers can be divided into the three phases, namely, initial hemihydration phase, dehydration phase, and coarsening, dissolving and the re-formation of calcium sulfate dehydrate crystal phase. In addition, it was found that in the hydration process of calcium sulfate hemihydrate whiskers the calcium sulfate dihydrate whiskers are formed at first and then converted into the calcium sulfate dihydrate with different crystal shapes, but in the hydration of gypsum hemihydrate the gypsum dihydrate is formed without transition products. The surface active site-calcium ion which has strong trend to react with H2O, the surface ?OH and the inner channels are considered to play important roles in the hydration process of calcium sulfate hemihydrate whiskers.

Jan 1, 2014

By Olgac Kangal, Ali Guney, Gulay Bulut, Guven Onal, Ayhan A. Sirkeci

"This paper presents the results of pilot scale column flotation applications in the two different copper concentrators in Turkey. The Kure Copper Plant is located in the Black Sea Region of Turkey. There are four types of copper ore formations in the Küre region. The so called disseminated ore contains 60-70% siliceous minerals of which Cu content is around 0.5%. The remaining three ore types in the region are generally named “massive ores”. The massive ores may assay up to 15% Cu and the major gangue mineral is pyrite associated with relatively little amount of silica. The main copper mineral in all formations is chalcopyrite that is generally finely disseminated in pyrite therefore satisfactory liberation requires ultrafine grinding especially in the case of the massive ores.A blend of these ores, containing 1.7% Cu on average, is fed to the Küre Copper Concentrator whose capacity is 1.2 million tons of ore annually. Unfortunately, today the plant operates below its designed capacity treating around 550,000 tons of ore per year. The design of Küre Copper Plant was undertaken by the Outokumpu Company of Finland. The operation of the plant is almost automatically controlled and the feed, the concentrate and the tailings are assayed for copper by on-line XRF analysers. The particle size analysers are also connected to the grinding circuit. The feed material is ground almost below 50 µm and the flotation is conducted around pH 11.2 using Hostaflot X-231 (a trade mark of Hoechst) as the collector. Apart from the rougher cells, there are four cleaning stages after which the final concentrate is produced. A very fine grinding requirement for an adequate level of liberation makes successful flotation difficult and consequently the final concentrate can hardly assay above 16% Cu leading to copper losses around 20% in the tailings that contains 0.3% copper."

Jan 1, 2003

By Alim Gül, Güven Önal

"Recently, there have been some attemps on the treatment of low grade ores and old plant tailings due to the decrease in high grade ores and the increase in the metal consumption with increasing world population. Cost of mining and beneficiation of low grade ores become prohibitive since the costs of grinding before flotation make the process unfeasable. Therefore, preconcentration of these ores prior to flotation becomes more important. The concentration of ores preconcentrated in coarse sizes provides a decrease in investment costs as well as grinding and flotation costs. Additionally, the requirements of less space for tailing disposal and less reagent consumption are also important from the viewpoint of environmental considerations.In this study, ore sample containing 0.6 % Cu and taken from Küre-Asiköy ore body was used. Ores contained chalcopyrite and pyrite as main minerals and diabaz, quartz, chlorite and sericite as gang minerals.Samples were all crushed under 9 mm by considering the preliminary studies and float and sink experiments were carried out with the sample in the size range of –9+1 mm using different densities of heavy liquids. As a result of these tests, it was shown that 60 % of the material should be discarded as tailings with 0.1 % Cu content. By considering float and sink test results, the following experiments were performed by using heavy medium cyclone and jigs.As a result of heavy medium cyclone tests, which are conducted on the sample in size range of –9+1 mm, 57 % of the feed material was discarded as tailing with 0.08 % Cu content and 7 % Cu loss, while a concentrate containing 1.43 % Cu was produced with 93 % efficiency (Table 1). Jig tests were done with the samples in the size range. As a result of jig tests with –9+1 mm size group sample, approximately 46 % of feed material was discarded as tailings with 0.13 % Cu content and 10.6 % Cu loss, while a concentrate with 0.94 % Cu content was obtained (Table 2)."

Jan 1, 2003

By S. M. Bradshaw, C. Dorfling, F. Ngandu

"Selenium removal and platinum group metal (PGM) recovery from copper sulfate leach solutions form an integral part of platinum producers’ base metal refinery operations. Recent studies found that substantially higher PGM recoveries can be achieved if excess thiourea instead of sulfurous acid is used as precipitation reagent; however, the impact of the proposed process on downstream processes was unknown. The objective of the current study was therefore to investigate the effects that excess thiourea and residual selenium present in the rich copper sulfate electrolyte have on copper electrowinning. This was achieved by performing cyclic voltammetry tests using a platinum rotating disk as working electrode, a graphite auxiliary electrode and a saturated calomel reference electrode. A synthetic copper sulfate electrolyte containing 0.01 M Cu2+, 1 M H2SO4 and varying amounts of selenium (20 – 150 mg/L) and thiourea (10 mg/L and 100 – 300 % excess) was used. The results obtained have shown that both thiourea and selenium interact with the cupric ion cathodic reduction reaction. Thiourea polarized the working electrode and lowered the efficiency of the cupric reduction reaction. Tests on the solutions with high selenium concentration showed simultaneous reduction of copper and selenium, which led to copper selenide formation. Nodule formation on the deposit surface also became significant at higher selenium concentrations. Based on these results, it was concluded that precipitation of PGMs from the copper sulfate solution with excess thiourea is not feasible due to the detrimental effect on downstream electrowinning operations.INTRODUCTION During the high pressure oxidative leaching stage in a typical base metal refinery (BMR) circuit, selenium, tellurium and some platinum group metals (PGMs) are dissolved along with the desired copper ions. The impurities (selenium and tellurium) may pass to the copper electrowinning circuit where it can result in the formation of nodular copper electrodeposits or reduced current efficiency. The presence of PGMs in solution, on the other hand, increases the precious metal inventory and potential losses of the operation. Currently, sulfurous acid is widely used for selenium and tellurium precipitation from copper sulfate leach solutions. Sulfurous acid is capable of reducing cupric ions to cuprous ions; the generated cuprous ions then react with Se4+ and Se6+ to precipitate selenium as a copper selenide (Bello, Dorfling, 2014). Recent studies have, however, proposed the use of excess thiourea as a precipitating agent for the removal of selenium and tellurium; it has the advantage of improved PGM recovery in the Se/Te precipitation step (Lottering, Eksteen et al., 2012; Mulwanda, Dorfling, 2015)."

Jan 1, 2018

By H. Q. Peng

The study of synergistic reagents combination of mineral floatation is more and more important with the decreasing of bonanzas now. In order to determine the chemical reaction mechanism, here we present the synergistic reagents combination: amyl-xanthate, butyl-dithiophosphate and N,N-diethyldithiocarbamate ester, which dissolved by different organic solvents. The reagents were applied by an Anhui mine to float low-grade covellite as a substitute for ethyl-xanthate. One reaction products Na2HPSO3?5H2O (disodium hydrogen-thiophosphate pentahydrate) which was re-crystalized and measured by X-ray diffraction analysis. In its crystal structure, the two crystallo-graphically different Na ions are six-coordinated and are bridged by two covalent bonds with the O atoms of water molecules to give a basket unit. However, we can?t get Na2HPSO3?5 H2O by combining butyl-dithiophosphate and N,N-diethyldithiocarbamate ester under the same condition. This discovery may provides a intuitionistic evidence that in the process of reaction, the three com-pounds would cooperate with each other, but the decisive reaction may be the hydrolyzation of amyl-xanthate.

Jan 1, 2014

By Y. H. Wang

Micro-flotation tests of spodumene, beryl, quartz and feldspar have been carried out by using CaCl2 and FeCl3 as modifiers and a blending collector of oleic acid and hydroximic acid. CaCl2 shows efficient activation for spodumene when pH is above 11.5, and FeCl3 exhibits a markedly activation and good selectivity for spodumene in the range of pH 4 to 10. The main species of CaCl2 are CaOH+ and Ca(OH)2 when pH is above 11.5, and the main species of FeCl3?6H2O are Fe(OH)+2 and Fe(OH)3 during the pH range of 4 to 10. A selective flotation of spodumene and beryl from pegmatic ore had also been completed while using FeCl3?6H2O as activator and the blending collector. A bulk concentrate containing 1.087% BeO and 4.70% Li2O has also been obtained in the flotation of spodumene and beryl from pegmatic ore assaying 0.097% BeO and 0.45% Li2O, and the recoveries of BeO and Li2O in concentrate are 74.38% and 69.50% respectively.

Jan 1, 2014

By C. Kleine

Coal sorting with an x-ray-transmission (XRT) sensor has experienced a lot of development since first described by Jekinson et.al. in 1974. Powerful computers and increasingly sensitive X-ray scintillation counters enabled the development of high-performance sensor-based sorting machines. The first industrial installation of a belt-type XRT-sorting for coal is in operation since 2004. It is upgrading high quality coal from 1% ash to 0.7% ash for cathode production. In comparison to the high quality coal which is treated with a belt-type sorter, the chute type sorter has been successfully optimized for high volume coal treatment of lower quality coals. This project was funded by the German Environmental Fund (Project Nr.244444). In cooperation with the RWTH Aachen University and Isambane Processing, CommodasUltrasort(now Tomra Sorting Solutions) conducted extensive pilot test work under production conditions in 2010 for the destoning of power station coal at Arnot Power Station in South Africa. The experience gained during this pilot test phase led to an optimized, redesigned PRO Secondary XRT Chute sorter which is now in operation at a South African coal mine. This flexible semi-mobile modular destoning plant is treating a size range of -120 mm +30 mm at a throughput of 150 tph. The implementation of this plant not only reduces the ash content, abrasiveness index and sulfur content significantly, but also reduces royalties, water treatment and transport costs.

Sep 1, 2012

By Z. F. Dai

The Thompson Nickel Belt, located in Northern Manitoba, Canada, contains more than 400 million tonnes of ultramafic low-grade nickel mineralization in 9 deposits. One of these, the Pipe deposit, was mined between 1971 and 1983 producing a Ni concentrate of 9% to 11% grade at 73% recovery. The operation was terminated because the poor recovery, low Ni grade and high MgO con-tent of the concentrate made processing this ore uneconomical at the metal prices prevailing at that time. Vale Inco is now re-evaluating these deposits with the intent of providing a new source of concentrate for its Thompson integrated processing facility. It is known that serpentine slimes coating on the sulphide surfaces are responsible for the poor metallurgy. Various desliming methods were tested including settling, elutriating, tabling and hydrocycloning. Hydrocycloning has proven to be the most effective means of desliming. With a feed assaying 0.70% Ni and 33% MgO, a rougher flotation concentrate assaying 22.7% Ni and 4.8% MgO was produced at a Ni recovery of 62.5% (relative to the feed to grinding), with no utilization of slimes dispersants. Another 16.6% Ni recovery was achieved in scavenger flotation resulting in a total Ni recovery of 79.1%. Batch flotation tests using various flowsheet configurations to optimize the grinding, desliming, reagentizing and flotation conditions are in progress.

Jan 1, 2014

Geopolymers are novel engineering materials with the potential to play a highly significant role in the transformation of the construction materials and building products industry in the push to-wards sustainable development. These materials are formed by activation of industrial aluminosilicate waste materials such as coal ash or blast furnace slag with alkaline solutions. Some mineral waste can also be used, either as fillers or as reactive components. The use of waste-based geopolymers results in significant (up to 90%) reduction in carbon dioxide emissions when used in cement replacement applications. In addition to the formation of conventional pre-cast products, these high performance mineral binders are ideally suited to use in the conversion or encapsulation of toxic waste, including radioactive waste, due to their chemical stability and resistance to acid attack. It is the aim of this paper to review recent developments on the science underpinning this ?green? technology, and to discuss the technical and commercial drivers governing the large-scale adoption of the technology. Some of the recent fundamental breakthroughs in the study of geopolymer technology at the University of Melbourne will be presented. Despite the complexity of this reactive sol-id-gel system, progress has been made in the development of a thermochemical reaction kinetic model that has been validated using both calorimetric data and synchrotron kinetic data. Geopolymerization is potentially a disruptive technology, so that it is normal to expect strong resistance from established companies in the construction materials industry. It is increasingly necessary that waste generating industries such as mining collaborate with industries such as construction that could utilize this waste. The world?s first full scale geopolymer plant utilizing waste and re-cycled material has been commissioned recently in Melbourne, Australia, so progress on commercialization will also be presented. The authors frequently present keynote lectures on geopolymer science and technology at materials science, ceramics and construction materials conferences. However, this interdisciplinary technology that is still in its infancy, deserves more attention in the mineral processing and mining industry in view of its potential use in the mining industry, and also in view of the importance of mineral processing techniques in recent advances in geopolymers.

Jan 1, 2014

By Johannes Käppeler, Alexander Weh, Harald Giese, Klaas van der Wielen

"High voltage breakage is a novel comminution technology that shows considerable potential for various applications in mineral processing and recycling. It relies on highly energetic electrical pulses to induce electrical explosions in rocks, causing the formation of plasma channels and powerful shockwaves that result in fracturing and fragmentation of particles. There has been considerable interest in this technology for its ability to weaken rocks and preferentially liberate target minerals, as previously demonstrated by other authors. Weakening has the potential to significantly reduce energy consumption during comminution, or alternatively, increase throughput of a circuit. Better liberation may yield an improved concentrate grade and/or recovery, reduce fines losses to tailings or increase the grind size required for liberation, thereby also reducing energy requirements. This review aims to increase general awareness of this technology, and promote further research into it by providing a general summary of the theory underlying high voltage breakage, as well as the envisaged applications of this novel technology. A brief history of the technology is presented before progressing onto the physics underlying the electrical and geomechanical aspects of high voltage breakage. Key results regarding weakening and liberation are discussed, and some mention is made of current challenges and planned developments to increase the throughput of high voltage breakage units to the level where it can be integrated into new and existing processing circuits."

Jan 1, 2014

By S. Banisi, E. Arghavani, Gh. Parsapour, S. Mousavi

Maximization of water recovery in thickeners is an essential step in the mineral processing industries. The Gol-E-Gohar iorn ore processing plant uses a center pier thickener with a diameter of 38 m and depth of 4 m. The feed rate is 50 t/h solids with a concentration of 5% (w/w), and it has been designed to provide an underflow containing 50% solids. The performance of the thickener was not as expected judged by the overflow stream containing 0.6% solids and water loss of 52 m3/h in the underflow. A criterion called the index of flocculation incorporating the perimeter-based fractal dimension of flocs, floc size, and settling velocities was proposed and used to determine the optimum flocculant dosage which was found to be 20 g/t. The fractal dimension of flocs in a pulp containing 5% solids was found to be between 1.16 (no flocculant) and 1.56 (40 g/t flocculant) which indicated highly branched and loosely bound structures for the flocs as flocculant dosage increased. At these conditions, the size of the flocs which was recorded by a digital microscope increased from 93 µm to 403 µm. A new feedwell with a special design with the aim of preventing flocs breakage and maximizing energy dissipation of pulp was constructed and installed. These modifications led to an increase in the thickener drivehead torque from 5% to 18% of the rated torque, indicating a higher bed depth. Finally, installation of a PID controller reduced the drivehead torque relative oscillation from 52.0% to 12.7%. These changes increased the solids concentration of the underflow from 49.0% to 56.9%, decreased the overflow solids concentration from 0.6 % to values smaller than 0.01% and resulted in a reduction of 27% in water loss in the thickener underflow.

Jan 1, 2014

By D. J. Zhao

The reduction and nitridation of preoxidized ilmenite pellets were investigated with the prospect of creating grain refiners containing titanium oxides and titanium nitride dispersoids. All the reduction and nitridation reactions were conducted in a furnace with a thermogravimetric analysis system under a H2-N2 gas mixture of 5 L/min. The ilmenite pellets were reduced at 1100°C for 4 hours under 80%H2-20%N2 gas mixture, and then respectively nitrided at 700°C, 800°C, 900°C and 1000°C for 12 hours under 10%H2-90%N2 gas mixture. The products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), and analyzed by Energy Dispersive Spectrometers (EDS) and Electron Probe Mapping Analysis (EPMA). Iron oxides were reduced into metallic iron, and oxides of titanium were found, but titanium nitride particles were not identified in the products under the prevailing conditions.

Jan 1, 2014

By Fedotov Pavel

One of the efficient means of ore disintegration during the processing is its volume breakage in such machines as roller-presses. Up to date neither the ore disintegration mechanism in roller-presses nor the reasons of their high efficiency are thoroughly investigated. In this work, the mathematical model of Finite Element Method of bad material disintegration in roller-press is discussed. The mechanism of the interparticle ore disintegration is traced.

Sep 1, 2012

By S. Gomez, P. A. Bebswa, A. N. Mwale

"The research aimed at improving the way screen performance analysis is conducted using a model that accounts for most feed and design parameters in its formulation. Thus, the aim was to validate the fine screen model that was developed at the Centre for Minerals Research (CMR) unit at the University of Cape Town. Fine wet screening is increasingly becoming an important application in fine grinding operations. Minera Saucito, a lead-zinc Mexican mine has replaced hydrocyclones with eight stacks of five decker derrick screens to close the ball mill in their concentrator plant. The five decker stacks have improved the overall plant throughput by 20% and have had the ball mill circulating load reduced considerably. As a continuous plant optimization process, a number of surveys were carried out to assess the performance of the 75 µm panel aperture installed screens. The surveys were conducted at seven different feed rates to the entire nest of screens to collect performance data. Using the fine screen model to analyze the results, it is found that as the feed rate increase, the sharpness of separation reduces. The CMR fine screen model was fitted to these results. The model fits the plant data with good accuracy. Simulated results based on this model are also presented.INTRODUCTION The potential of high frequency vibrating screens has long been identified as an alternative to hydrocyclones in grinding applications (Rogers and Brame, 1985). However, high frequency vibrating screens have had two main disadvantages, low capacity and high wear rates (Kelley and Mckeon, 2005; Teknikk, 2009). Current vibrating screen technology overcomes these challenges by multiple deck screen design and use of wear resistant urethane materials for panel construction (Kelley, 2007; Valine and Wennen, 2002). For a example, the Derrick screen’s material of construction is a tensionable urethane that provide high open area ranging between 35 to 45% with considerably reduced blinding (Valine and Wennen, 2002). Thus, there has been an increased uptake by the mining industry in the use of wet fine vibrating screens closing the ball mill as the final classification stage in the comminution circuit (Barkhuysen et al., 2010; Frausto, Ballantyne et al. 2017; Pelevin and Lazebnaya, 2009; Teknikk, 2009). Even though there is a number of models in existence, none of these models adequately predict the performance of high frequency vibrating screens (Karra, 1979; Rogers, 1982; Subasinghe et al., 1990; Trumic and Magdalinovic, 2011). Recently Mwale et al., (2016) developed a model for predicting the performance of high frequency vibrating screens using the partition curve properties. The input parameters of the model include screen open area (??) in m2, tonnage feed rate (????) (tph) and the weight fraction of solids (??) in the feed for a given panel aperture size. The model was developed based on data collected from a single deck industrial size derrick screen, in a pilot setup. The work presented in this paper is an attempt to test this model using data collected from Minera Saucito concentrator, an industrial plant whose comminution circuit is shown in Figure."

Jan 1, 2018

By Vasily V. Lodeischikov, Adolf F. Panchenko, Olga D. Khmelnitskaya, Vladimir E. Dementyev

Pilot plant tests of underground gold leaching from Maminskoye deposit oxide ores at a grade of 0,7 g/t Au were carried out. The underground leaching flow sheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution on active carbon, carbon concentrate ashing and calcine melting to produce high grade gold concentrate. The underground leaching system throughput was 15 m3 of solution per hour. Gold concentration in pregnant solutions was 0.12-0.13 mg/l. Gold recovery from solutions into carbon was in the range of 63-84%. It was demonstrated that the low Au recovery in the adsorption cycle was due to the presence in pregnant solutions of "active" chlorine, which destroys active carbon and causes a sharp decrease of the carbon loading capacity for gold. To improve the adsorption indices, previously dechlorinated pregnant solutions using bituminous coal or Na2S2O3, is recommended. Ion exchange process was tested as an alternative for gold extraction from dechlorinated solutions. In the testwork period, 4.4 kg of gold were produced with a chlorine consumption of 3.5 kg per 1 g of gold. During the tests a program of environmental protection measures was completed to provide the necessary safety precautions of the underground leaching works.

Jan 1, 2003

By D. W. Fuerstenau

Understanding how cationic surfactants affect the interfacial behavior of quartz is important in mineral processing and environmental engineering. This paper presents the results of a study of the effect of the molecular structure of cationic surfactants on the interfacial behavior of finely ground natural quartz. Most of the experimental work involved the determination of zeta potentials and the stability of quartz suspensions. Some measurements of induction times and the flotation response of coarser particles are also included. How these surfactants affect interfacial behavior is discussed in terms of adsorption mechanisms. The molecular structure (number of hydrocarbon chains, type of ionic head group, number of ionic head groups on the molecule) of these reagents was found to significantly affect their surface activity.

Jan 1, 2014

By Mingxia Liu, Qi Liu, Tao Jiang

"In addition to physical parameters such as small mass and high specific surface area of fine and ultrafine minerals, chemical parameters such as the adsorption affinity of collectors on the minerals also plays an important role in fine particle flotation. In this study, we have examined collectors with two different ionized groups, carboxylate and hydroxamate, on the flotation of fine niobium oxide (pyrochlore). To facilitate comparison, two hydrocarbon radicals were tested: octyl and oleoyl, which led to four collectors that were studied: octyl hydroxamic acid (OHA), sodium octanoate (C8OONa), oleoyl hydroxamic acid (C18HA), and sodium oleate (NaOl). Small-scale flotation and isothermal microcalorimetric titration measurements were performed to determine the flotation recoveries of different sized pyrochlore and the enthalpic behavior after adsorption of the collectors on pyrochlore. It was found that the flotation performance of the carboxylate-based collectors was generally inferior to hydroxamate-based collectors. Sodium octanoate could not float pyrochlore irrespective of the particle size of the pyrochlore tested. With a longer hydrocarbon chain, sodium oleate was effective to float the relatively coarse pyrochlore (>20 µm) but its collection efficiency dropped sharply for particles smaller than 20 µm. On the other hand, the two hydroxamate-based collectors, octyl hydroxamic acid and oleoyl hydroxamic acid, showed good collecting ability to both the coarse and fine pyrochlore. The isothermal microcalorimetric titration studies indicated a consistent correlation of chain length with floatability of collectors for relatively coarse pyrochlore, as well as a positive relationship between the adsorption affinity and fine pyrochlore flotation recoveries. The key finding of this study was that efficient fine particle flotation could be achieved when strongly chemisorbing collectors were used.INTRODUCTION The first detailed study of the effect of particle size on flotation was made by Gaudin (1931) with sulphide ores. In 1942, Gaudin again demonstrated that (Gaudin et al., 1942) fine particles possess different flotation properties from larger particles. Since then the effect of particle size on froth flotation has been an important research topic by many researchers, e.g., Gaudin (1957), Miettinen et al. (2010), Warren (1976) Jameson (2010), summarizing the behavior of fine particles in terms of their low particle momentum, leading to low rate of collision with bubbles which reduces the chance of adhesion. The suggested remediation methods are mainly based on two approaches: increasing particle size or decreasing bubble size (Warren, 1976). Sand-fine splitting followed by separate flotation treatment of the sand and fines, using deep flotation cells, using starvation quantities of collectors, and using long flotation times, are also strategies to address the problems of fine particle flotation."

Jan 1, 2018

"The thiosulfate leaching process developed by Barrick to treat sulfidic high preg-robbing gold ores uses calcium thiosulfate as the leaching reagent for ores pre-treated by pressure oxidation, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a means of reagent recovery. A large portion of the research that led to the development of the technology was based on previous studies completed by different groups over the years, mainly focused on the ammonium thiosulfate system. Operational limitations in the use of the ammonia-containing recycled water in the pressure oxidation circuit were some of the main drivers for the change from ammonium to calcium thiosulfate for the development of the industrial scale process. One of the main aspects for successful gold extraction and recovery in the thiosulfate system is the pseudo-equilibrium reactions that drive distribution of the different gold species (in solids, solution and on resin) in the system. Previous studies have been focused on the thiosulfate reactions and equilibrium constants for the oxysulfur ions (thiosulfate, trithionate, tetrathionate). However, the literature around the effects of the different metal-oxysulfur complexes (Cu and Hg complexes) that form when the ore is in contact with the leaching reagents, and the related effects on stability of the gold complex is limited. The main changes in the gold complex chemistry and stability in the calcium thiosulfate system as compared to the ammonium and sodium equivalents, as well as related effects on gold recoveries, were investigated in the presence of different types of double refractory ores. INTRODUCTION Barrick has developed a thiosulfate leaching process to treat double refractory gold ores, by combining the use of acidic and alkaline autoclave pre-treatment with thiosulfate resin-in-leach (RIL). The process currently in operation at the Goldstrike mine (the TCM process), uses calcium thiosulfate as the leaching reagent, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a mean of reagent recycle. The main feed to the process plant is highly preg-robbing sulfidic ore from Goldstrike’s open pit. Prior to feeding the pressure oxidation circuit, the ore is processed through the crushing and grinding circuits and treated in preparation for acid or alkaline autoclave processing (POX)."

Jan 1, 2018

By Tuan V. Nguyen, Kosta Simic, Louis Mittoni, Murray Rudman, Jean D. Swift, John B. Farrow, Phillip D. Fawell

"Research projects towards developing a sound understanding of the factors controlling the performance of gravity thickeners have been conducted by the AJ Parker Cooperative Research Centre for Hydrometallurgy since 1988 through AMIRA International. The current phase of this work, the three year P266D .Improving Thickener Technology. project, has 27 sponsors comprising mineral processing companies, reagent suppliers and thickener manufacturers.These projects have resulted in the development of a range of tools and techniques to address flocculation, thickening and associated dewatering issues. A number of Computational Fluid Dynamics (CFD) models have been developed to predict likely full-scale thickener performance under various process conditions, based upon a knowledge of thickener design, plant flows and assessment of the flocculation behaviour of the feed slurry. At the same time, various laboratory and plant studies have been used to quantify important thickener processes, and to provide validation of the CFD models. These numerical and experimental capabilities have been applied to various thickener issues across a broad range of mineral processing operations, leading to significant process improvements and substantial financial benefits.This paper presents an overview of the work conducted during these projects, focussing on the research tools, the nature of the information that has been gained and the implications for thickener performance."

Jan 1, 2003

By Elves Matiolo

This paper describes, in detail, results obtained from a research study of a complex iron ore aiming to produce a pellet feed concentrate with at least 65% of Fe and less than 3.5% of SiO2 in the final concentrate. The work includes an ore desliming followed by column flotation at laboratory scale. The ore sample was from Carajás province - Brazil and represents a complex low grade compact itabirite ore, analyzing 35.9% Fe, 45.1% SiO2 and 0.57% of Al2O3. Yet, the feed was treated previously by magnetic separation and grounded to 97% < 20 µm; this sample was named MAG 2. The chemical and mineralogical characterization of the MAG 2 sample showed that Fe and SiO2 grades were 50.7% and 24.3% respectively and was composed mainly by hematite, goethite and quartz. The particle size distribution, using a laser diffraction technique, showed that 90% of the particles were < 18 µm; 50% less than 8 µm and 10% minor than 1 µm. When the cationic reverse flotation without desliming was tested the selectivity of the process was very low and did not meet the concentrate metallurgical goals of the pellet feed product. However, when desliming was applied prior to flotation, a concentrate product with chemical characteristics of the pellet feed was obtained. The best results after desliming and column flotation achieved global iron metallurgical recovery of 72% with Fe grade in the concentrate of 66.5% and 2.1% SiO2 using starch as depressant for the iron oxides minerals at 1200 g/t ? 1500 g/t and an amine as the quartz collector at 100 g/t concentration (pH constant, at 10.5). It is believed that the desliming stage was key in the separation of the iron bearing particles and has a high potential for the flotation process of this type of ores.

Sep 1, 2012