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By C. Çelik

Nowadays the optical sorting of industrial minerals is one of the most important processing methods which has cost efficient production possibilities. This method is used for industrial and raw materials that have different colour and brightness features. Initially this technology is used for sorting of foodstuffs and recovered glass, but for a long time also as physical mineral processing method for both industrial minerals like: limestone, marble, talc, basalt, flint, quartz and secondary raw materials like: building rubble, refractory materials, glass, plastic and household waste. In this study via optical sorting the separation of quartz out of a flint mix, which consists of the particles with different colors and brightness, is aimed. Experiments are performed on an optical sorting machine named CombiSense® 1200 at the institute of ?Aufbereitung mineralischer Rohs-toffe? RWTH Aachen. This automatic picking device was developed by the company ?Separation Systems Engineering (SSE), Wedel?. Hand picking method is used for product analysis and the efficiency tables are prepared on every step accordingly. This process enables to reach quartz products with purity up to 100%.

Jan 1, 2014

By G. K. Nimal Subasinghe

The performance of Knelson Concentrators (KC) used in gravity gold circuits often rely on manufacturers recommendations for selecting operating parameters such as, fluidising water flow rate and cycle time. These parameters are not only dependent on the machine parameters but also on the feed characteristics such as, size distribution of the gold and gangue particles and the composition of its constituent minerals. Particles entering a KC experience a centrifugal acceleration due to the high bowl rotational speeds. The required centripetal force to maintain a circular orbit is provided by the fluid drag force created by inwardly moving fluidising water and the Bagnold?s force arising from the particle/particle collisions. When the fluidising water flow rate is low particles move towards the outer rim of the bowl forming a packed bed within the grooves. On the other hand, if the fluidizing water flowrate is high the bed expands and some particles would move towards the centre of the bowl and gets carried to the tailings stream, thereby reducing the amount of material retained within the grooves of the bowl. Based on a force balance on a particle captured within the KC, a criterion which can be used to predict the amount of material recovered in the bowl has been derived and validated by experimental data. It has been shown that this criterion may be used to demarcate the transition of the bed from a packed-bed state to a fluidised state depending on the fluidizing water flowrate. By identifying the conditions for the optimal expansion of the bed comprising different constituent mineral particles, it is possible to estimate the optimal fluidising water flow rate that would maximise gold recovery while minimising gangue recovery. It was also observed that the accumulation of valuable mineral in the bowl takes place by the displacement of the gangue particles in the bed by the incoming heavy mineral particles. The kinetics of this segregation process was also studied using synthetic mineral mixtures. The experimental data suggests that this process follows first order kinetics and that the build up of heavy mineral reaches a maximum which could be used to identify the optimal cycle time. In this work, the suitability of the above model in optimizing the performance of a KC have been reviewed. Also the necessity and merits of testing an unaltered

Jan 1, 2014

By F. Burat

At the present time, methods of mining and coal preparation produce tones of coal fines. The removal of water from these fines is necessary for economical and technological reasons. Supplementary processes that utilize different physical and chemical methods have been developed to in-crease the productivity of mechanical dewatering processes. Researches have shown that chemical reagents used along with conventional systems diminish moisture and increase the capacity and the yields of the dewatering method. In this study, the parameters of the vibrating screen (incline, frequency, feeding rate and screen size), the effects of the application of additional vertical mechanical vibration and surface active reagents (CTAB, SDS, Umectante B-70 and Kerosene) were investigated. At the end of the optimization experiments, 61.0% moisture was decreased to 42.3%. By keeping optimum conditions con-stant, the experiments have been conducted to determine most effective reagent. 41.2% moisture has been obtained with 5 g/t CTAB at the normal pH of the pulp, which were 7.25. By using vibrating screen with combination of the vertical vibrating mechanism, CTAB gave the best result of 40.7% moisture. Finally, the effect of increased surface area of the screen has been investigated and de-creased the moisture level to 38.7%.

Jan 1, 2014

By Rodolfo Silva, Antonio Peres, Afonso Martins, Gilberto Ramalho, Mario Cabello

The consumption of aggregates in civil construction has increased considerably in Brazil for the last years. The extraction of sand and gravel generates significant environmental impacts. As the quarries and sand deposits are getting exhausted near the big cities, the price of aggregates is increasing. Meanwhile, the extraction of quartzite (dimensional stone) in the state of Minas Gerais has been done mostly in small quarries, with very low recovery, generating approximately six million tons of wastes a year, which causes pollution, increases final prices of products, decreases the life time of quarries and ends up in the closure of enterprises. The government agencies and the quarries’ owners understand that only by finding applications to wastes there will be development to the sector. The aim of this investigation was to study the application to the quartzite wastes as aggregate in the civil construction. Samples of quartzite wastes collected in a quarry were characterized by petrographic analyses. Laboratory tests of crushing and grinding were done to analyze the viability of reducing the size of coarse material to a finer one to be used as raw material in industrialized mortars and concrete pre-molded components.

Jan 1, 2014

By Rodney J. Hundermark, Sharif Jahanshahi, Shouyi Sun

"The major platinum producers in South Africa make use of electric furnaces for the melting of platinum group metal (PGM) bearing nickel – copper concentrates. To gain better understanding of the furnace operation, research was conducted at CSIRO Minerals in Melbourne, Australia. One aspect of the research project was the investigation of the factors affecting the electrical conductivity of melter type slags.Electrical conduction in slags can occur through two mechanisms: ionic and electronic. There is good understanding of the ionic mechanism. In slags containing high levels of iron, the dominant mechanism is electronic as a result of charge hopping (electrons or holes) between ferric and ferrous ions. There is limited understanding of the electronic mechanism and one of the aims of the research was to investigate this mechanism further.Experimental work was carried out at 1450 °C on Al2O3–CaO–FeOx–MgO–SiO2 slags similar in composition to the melter slags (typical composition range (wt%): Al2O3: 5, CaO: 5-15, FeOx: 10-30, MgO: 15-25, SiO2: 40-60). The approach was to vary the oxidation state of three different basicity slags and measure the conductivity response. The slags had molar (CaO+MgO)/(Al2O3+SiO2) ratios of 0.43, 0.64 and 0.94 and FeOx contents of up to 40wt%. A twoelectrode technique was employed with a shallow layer of slag contained in a magnesia crucible. The small amount of slag facilitated relatively quick equilibration (up to one hour) with the gas atmosphere. Experiments were typically started in air and sequentially reduced using different ratios of CO and CO2 gases.Conductivity increased with increasing basicity and increased significantly with iron oxide content. Above 20wt% FeOx, electronic conduction was significant and the conductivity varied with the oxidation state of the slag. The typical response of the conductivity to the change in oxidation state was the following: starting in air, as the slags became more reduced, the electrical conductivity increased to a maximum at around pO2 = 10-7 to 10-4 atm and then decreased with further reduction. The value of the pO2 at which the maximum occurred was dependent on the total iron oxide content and basicity of the slag. The magnitude of the conductivity of the slags increased with increasing FeOx content in a range of 20 to 170 S/m for 20 to 40wt% FeOx. For a given FeOx content in the slags, the oxidation state dependence of the conductivity varied with slag basicity. The trend observed was that the maximum in the conductivity occurred at higher oxygen partial pressures for the lower basicity slags."

Jan 1, 2003

By R. ?. Sherembayeva, ?. ?. ?uktybayeva, ?. B. Rakhimbekova, N. ?. ?m?rova

"Studying the interaction of the phosphorus-containing flotation reagent with the components of the flotation system ""liquid-gas-solid"" during flotation of non-ferrous metal ores allows regulating the enrichment process. The phosphorus-containing reagent-collector anabasinium-O,O-dimethyl-thiophosphate has beensynthesized under laboratory conditions and the concentrated aqueous solution of anabasin hydrochloride and the 40% solution of sodium hydroxide have been used as the raw material. The phosphorus-containing reagent has been obtained by interaction of the anabasine base, sulfur and dimethyl phosphite, due to sulfur and nitrogen atoms it can form complex compounds with heavy metal ions.Studying flotation of copper-sulfide ore of the Sayak field with the use of the phosphorus-containing reagent-collector anabasinium has been performed in the open and closed cycles. The degree of ore grinding was 60- 62% of the class -0.074 mm. There has been established the dependence of the ore flotation parameters on: a) pH of the pulp; b) the consumption of the reagent-collector anabasinium.The effect of the pulp pH on the technological parameters of copper ore flotation has been carried out with a reagent regulator that increases the difference in the surface properties of the minerals to be separated.There has been used lime as the regulator of the medium, the consumption of which varied from 750 to 1500 g/t; the consumption of the reagent-collector anabasinium was 10, 15, 20 and 25 g/t.It has been found that when flotation of copper ore without the use of lime at pH equal to 7.8 and at the reagent consumption, g/t: anabasinium - 25, T-92 - 55, copper recovery in the concentrate is 92.72%, the quality of concentrate is 7, 1%.In flotation according to the factory mode (the consumption of xanthate is 44 g/t, T-92 is 55 g/t, pH = 7.8 (without lime)) of copper ore, copper recovery in the concentrate is 87.38%, the concentrate quality is 7, 97%, with reducing the xanthate consumption to 25 g/t copper recovery is reduced to 83.39%, the quality of the concentrate is up to 6.69%.In the experiments using the factory reagent mode in the closed cycle, with the xanthate mass consumption of 44 g/t, T-92 blowing agent of 55 g/t, the third recleaning concentrate contained 19.13% copper with recovery of 86.89%.Using a phosphorus-containing reagent instead of xanthate with the same flow rate, the third recleaning concentrate with the mass fraction of copper of 19.82% has beenobtained with recovery of 87.77%."

Jan 1, 2018

By M. Kalicinski, M. Lyssyy

"Access to information is a key component for making improvements to any process. This is particularly true for all aspects of the iron mining and steelmaking process. The ability to make rapid control decisions can significantly influence process outcomes, including ensuring product specification, mining quality, transportation limits, upgrade factors, waste bypass and direct shipping, among many others. While traditional laboratory methods provide feedback for such processes, having access to analysis results in real-time can lead to positive reactive and predictive control decisions to be made rapidly, leading to significant improvements throughout the process. Scantech has been designing, manufacturing and supplying technological products to the minerals industry since 2002 to enable the availability of such real-time information to a mine or plant, with the benefits being enjoyed by a wide range of operators. This paper provides a summary of the available technologies used in the iron ore and steel industries, as well as providing case studies of their use in African and Australian iron ore and European steel, as well as a description of the potential benefits of a range of analysis equipment.INTRODUCTION Access to information is critical for any process, and is a fundamental component for making process control decisions. In order to yield effective processing outcomes, it is important for that information to be readily available, preferably as quickly as possible, and to be as accurate as possible. While speed and accuracy are often traded off against each other, there are numerous technologies available in a processing environment that allow for both rapid flow of information and a high level of accuracy. The use of on-belt analysis equipment has a long trusted history of use in a number of mining and processing environments and industries, providing information such as elemental composition and grade of conveyed materials, moisture content, waste proportion and energy information. Australian company Scantech has been a provider of such equipment since 1981, and has become an industry leader in both the supply and development of on-belt analysers across a range of industries."

Jan 1, 2018

By Vladimir Vigdergauz, Sergey Kondratiev

The paper reviews the existing criteria of the formation of particle-bubble aggregates during flotation. It is shown that predictions obtained by these criteria do not completely fit to the interaction between mineral particles and air bubbles. Experimental results of the studies into the influence exerted by molecular forms of collectors on the particle-bubble interaction are reported. Rate of dry spot expansion on the surface of pyrite with various combinations of chemically and physically adsorbed xanthate are examined. It is shown that molecular forms of collectors accelerate the rate of dry spot expansion on the mineral surface after the local rupture of the water film between particle and air bubble. The authors come to a conclusion that the molecular forms of collectors remove water from the interlayer between mineral particle and air bubble during their contact. Similarities of the proposed mechanism with the action of ion-molecular associates of fatty acids and amines are discussed. Reagents with high surface pressure and rate of spreading at the water-bubble interface are required for the effective interfacial dewatering. It is concluded that the value of surface pressure can serve as the criterion for efficiency of physically adsorbed reagents. The low surface pressure indicates weak collecting ability but high selectivity of the collector. Therefore, the presence of the molecular forms of collectors in the sorption layer is the necessary condition for formation of particle-bubble aggregates, and comparison of the surface tensions of collectors could be recommended as the estimation criterion of their flotation activity and selectivity.

Jan 1, 2014

By R. Paturi

Mill liners play an important role in the operation of a mineral concentrator influencing the throughput, availability, power drawn and the efficiency of the mill in the plant. Liners protect the shell and transfer energy to the grinding charge. Metso Technology Development has conceptualized, developed and successfully implemented physics based 3D DEM simulation techniques to predict charge motion, power drawn, energy spectra and wear over the life of the liner. This paper will present a case study of shell liner optimization for a 34? SAG mill including the input data requirements, and shell liner optimization methodology using the 3D simulations that eliminates the need for the traditional expensive and lengthy proto-type testing. These simulations will cover ball and particle movement, liner wear and mill power draw, and do not cover particle breakage and slurry flow. Even the liner manufacturers lack the ability to provide this type of qualitative and quantitative information on their products. The data from these simulations provides the plant engineers a scientific basis for their decision making and thus eliminates guess work. Keywords: liner, optimization, multi-physics, 3D-DEM

Sep 1, 2012

By N. Naudé

The theory on particles displacement subjected to upwards and settling movements in water, using a water pulse, is described in literature, but very little experimental data is available to verify these theoretical ideas. The aim of this research work was to visualize the displacement of solid particles in a mixture of water and solid particles created with the aid of water pulses in the Mineral Density Separator. From the literature it is known that lighter particles are subjected to higher levels of displacement than heavier particles, and when the particles then settled down, layers of material are formed ac-cording to the densities of the material. By removing the individual material layers, the materials can then be separated according to their densities. During this study the individual material layers were investigated regarding the density and size distribution in that specific density layer. It is important for this project to have a statistical prediction of the ?real? flow of the particles with different density and size distribution, inside the Mineral Density Separator. The information gathered during this study will be used to show the correlation between a two dimensional model of the particle flow and that of the real three dimensional flow inside the Mineral Density Separator.

Jan 1, 2014

By P. Saha, D. M. Chakrabarti, National Metallurgical Laboratory, P. Bhattacharyya, B. R. Sarkhel

The estimated reserve of the phosphatic soils at the Sukulu hills region of Uganda upto a depth of 60 meters is of the order of 200 million tonnes and analyses 10-12% P2O5. A 5-tonne sample of the phosphatic soil was received at the National Metallurgical Laboratory (NML), India for beneficiation studies. The ore occurred as a naturally degraded soil deposit and the slime contained earthy lateritic minerals which made it extremely sticky. Microscopic examination revealed the presence of limonite, magnetite (martitised), hematite and goethite as major minerals along with apatite and quartz. Presence of clay was indicated by earthy smell on moistening the sample. It was observed that getting rid of the slime was as important for adequate beneficiation of the ore, as it was difficult. Earlier studies on samples of the same ore at the NML and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of rigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the sticky slimy coating which stubbornly adhered to mineral grains. Studies were carried out at the NML in two phases to develop a flowsheet for beneficiation of the phosphatic soil. In the first phase, reproducibility of the results obtained by employing a flowsheet developed abroad was confirmed along with suggesting some modifications of the flowsheet. Then 200 kg. of concentrate was produced following the recommended flowsheet for evaluation of its suitability for production of fertilisers. To remove the limonitic slimy coating, which stubbornly adheres to the other mineral grains, it was necessary to subject the ROM ore, after screening out the +840 micron size fraction which contained only 1.75% P2O5 , to three stages of hydrocycloning each preceded by attrition scrubbing. Then only conventional beneficiation techniques could be effectively employed to upgrade the ore.

Jan 1, 2003

By M. L. Torem, R. H. Rojas, A. G. Merma

"Fine particle recovery by conventional flotation processes is very low mainly due to the low probability of bubble/particle collision and adhesion. In order to solve the problem of low particle recovery, several flotation technologies have been developed to increase bubble/particle collision efficiency. Among these technologies, the electroflotation process stands out. This process has advantages in the generation of microbubbles (<100 µm) and in the production of different amounts of hydrogen and oxygen microbubbles. These advantages favorably influence the fine particle floatability, due to the greater probability of particle/bubble collision and adhesion. The electroflotation tests were conducted for a hematite/sodium oleate system in a Partridge-Smith modified electroflotation binary cell of 0.38 L usable volume. The sodium oleate concentration, particle size, pH and current density were evaluated. Satisfactory results in the recovery of hematite were found at pH values of 7, reaching hematite floatability of 99% and 90% with hydrogen and oxygen bubbles, respectively.INTRODUCTIONThe flotation recovery of fine and ultrafine particles is normally very low and is caused by several factors, among them, the low probability of collision and adhesion bubble-particle, the difficulty to overcome the energy barrier (entrainment and entrapment), low selectivity, surface oxidation and mineralogical changes (Schulze et al., 1989; Waters et al., 2008; Shahbazi et al., 2010). This problem can be overcome by decreasing the bubble size or by increasing the apparent particle size. However, it is worth noting that the use of small bubbles or micro bubbles also involves some disadvantages such as their low momentum resulting in a slower process comparing with conventional flotation. Electroflotation is an attractive alternative for treating fine particles with small bubbles less than 100 µm, generated by the electrolysis of water. Electroflotation is one of the variants of the flotation process, where the gaseous phase is produced by electrolysis of an aqueous solution, generating oxygen and hydrogen bubbles (Sarkar, 2010; Gupta and Ali, 2012). These smaller size bubbles allow the recovery of fine particles by increasing the collision efficiency. This process is versatile and competitive in relation to other techniques such as dissolved air flotation and dispersed air flotation because the electroflotation units are smaller, more compact and require less maintenance and less operating cost than other flotation units (Zouboulis and Matis, 1995,). In addition, the electroflotation process is a clean technique and provides results in a short time, requiring only the investment in the electroflotation cell construction stage and the choice of the electrodes (Ketkar et al., 1991; Sarkar et al., 2010; Sun et al., 2011). In this sense, this study assesses the effect of pH, particle size and sodium oleate concentration on electroflotation of hematite fines."

Jan 1, 2018

By Victor V. Karmazin

"The appearance of the precise equipment for analysis of results of the laboratory tests with using of the computer processing allows raising accuracy of the estimation of the expected indexes of the mineral processing. Certainly, laboratory tests will not be able to substitute completely industrial ones, but allow reducing the amounts of the industrial tests, that vastly reduces the cost of technological forecast and preparation of data for projection.Calculation of the potential indexes of mineral technology (mass yields and the metal content in products) is fulfilled on the base of results of measurements of the mineralogical liberation parameters using special formulas.The quality of the concentrate ßc = a + ?l • ?s • ?i (ßt - a) can be achieved on a level of the theoretical metal content of a mineral - ßt only if coefficients of mineral processing, of liberation ?l and selectivity ?s of grinding, effectiveness of separation, will reach 1 (a - metal content of the row ore).Increase ?l by overgrinding automatically decrease ?s, and only by destroying of particles of ore along surfaces of accreting of minerals (?i = 1) and when values of all three coefficients will aim to 1, then ßc ? ßt.The degree of liberation of the useful mineral is the ratio of mass of free grains of the useful mineral in the product to general mass of the same mineral in this product. The factor of the liberation, which is defined by curves of dressability by angle of slop of the curve of the elementary faction - ?, is Kr=1 – tga. Kr changes from 0 to 1 when a changes from 45o to 0o. The liberation is reached by grinding of the material, although degree of the liberation, as a rule, is lower than the degree of the grinding."

Jan 1, 2003

By Chuansheng Luo, Qiuyang Hong, Lili Zhang, Dongyun Liang

"The metallogenic rock of a sandstone-type Cu ore is arkose-quartzite as well as siltstone and the cement is composed of argillaceous minerals including sericite, chlorite, etc. and carbonate minerals including calcite, dolomite, etc. A detailed process mineralogy study on this complex copper ore was carried out using MLA combined with traditional research methods. According to the results, there are many types of Cu minerals including copper sulfideminerals, secondary copper sulfideminerals, copper oxideminerals, copper carbonate hydroxide minerals and copper silicate minerals in the ore. Based on the occurrence of Cu, the copper existing as copper sulfide minerals (bornite, chalcopyrite and chalcocite) and copper oxide mineral (malachite) which have a good floatability accounts for 49.28% while the copper (chrysocolla) hard to be recovered by flotation and the copper existing in the cement (sericite, chlorite, psilomelane and limonite) accounts for 48.65%, and the copper existing in the carbonate minerals (calcite and dolomite) accounts for 1.72%. The process mineralogy study indicates that the process "beneficiation combined with hydrometallurgy" should be applied due to the various occurrence of Cu. The abundance of calcite and dolomite is about 12%, so removing these acid-consuming minerals by floatation is an effective way to reduce the acid consumption in the hydrometallurgical process and the lowest Cu loss is 1.72%. So the process "floating copper minerals-floating calcium minerals (calcite and dolomite)-leaching copper from the tailings" is used in the pilot tests. The recovery of floating copper and leaching copper from tailings is 46% and 30% respectively, so the total recovery of copper is 76%. Compared with the original process "leaching copper from crude ore-floating copper from the residue", the total recovery reduces by 1% but the acid consumption of producing per ton of copper decreases from 37t to 12t. The new technology process has a great advantage."

Jan 1, 2014

By S. M. Saghaeian

The studies on the product finer than 12 mm due to crushing and sizing plant of Gol-e-Gohar Iron Ore mine showed which this material contains significant amount of valuable iron minerals. Based on the carried out experimental studies on representative samples of fine hematite iron ore, a processing flow sheet was designed to upgrade iron content. This plant is known as first hematite iron ore enrichment plant in Iran which the dry medium intensity magnetic separators (with magnetic field intensity 4500 gauss and high gradient) has been used. The main objective of the plant is production of high iron product with iron content more than 61% and weight recovery more than 55% from the feed with iron content of 54%. In this plant, at first material are screened by a single deck screen (6mm), then oversize particles is separated at one stage by magnetic separator, while undersize ones at two stages. Based on the results of experimental tests, a final high iron product with iron content of 62.4% and weight recovery 63.9% can be achieved. It should mention which the iron content can be enhanced through increasing the speed of magnetic separators especially at the part of separation of finer iron ore.

Jan 1, 2014

By C. Gomez, J. Finch, R. Dalhke, J. Torrealba-Vargas

"The dispersion of gas into bubbles is an essential feature of flotation machines. Three measurements have typically been used to describe the dispersion: superficial gas velocity (Jg), gas holdup and bubble size along with the derived quantity, bubble surface area flux. Measurement devices continue to be developed. The McGill Jg sensor based on accumulating bubbles by natural buoyancy comprises a tube with a valve and pressure transducer (Figure 1). The tube is immersed at a desired location and depth (H1) in a flotation cell. On closing the valve pressure increases to a maximum (P1) when the tube is full of air. The Jg is estimated from the slope of pressure-time curve (dP/dt).The relationship between Jg and dP/dt is derived from first principles. Testing the relationship is difficult in a flotation machine as the spatial variation in Jg is generally not known. This problem is overcome using a specially designed experimental setup and the estimated Jg is shown to equal the known Jg.The derivation reveals the importance of bulk density (?b). The sensor was modified to provide an estimate of ?b (Figure 2). A second tube was added immersed to a different depth (H2) and kept full of accumulated air giving a pressure P2. The estimate of ?b is given by (P1-P2)/(H1-H2) (i.e., at the end of collecting the pressure-time data). This two-tube sensor also helps dampen process noise as illustrated by a sudden change in level when collecting the pressure-time curve. Both the original and modified versions have been widely used in plant test work."

Jan 1, 2003

By Lei Zhang, Xianjun Lu1, Minjie Lian, Liyang Zheng

In order to investigate rheological behaviour of fine tailings backfill pastes, the fine iron ore tailings (size fraction of -0.074mm accounts for 70%) from Fuquan Mining Co., Ltd. of Sinosteel Corporation (Shandong, China) was investigated. The rheological parameters such as slump, viscosity and yield stress of the tailings pastes under different densities were measured in detail, and the effect of paste density on the rheological property and the relationships of different rheological parameters of the pastes were also discussed. According to the results, the rheological behaviour is in accordance with the pseudoplastic fluid in a wide range of paste densities (solid content, w/w) of 65% to 80% and the pastes turn to be Bingham fluids at higher shearing rates. Along with the increase of paste density, the slump drops gradually and the viscosity and shear stress increase gradually. However, the variation extent of the rheological parameters varies at different density ranges. According to the variation pattern of the rheological parameters at different paste densities, the flow ability of the pastes can be classified into three zones. The high fluidity zone was observed at the density range of 65%-69% where the rheological parameters vary slightly along with the paste density, the moderate fluidity zone was observed at the density range of 70%-76% where the rheological parameters vary significantly along with the paste density, and the low fluidity zone was observed at the density range of more than 76% where the rheological parameters vary sharply along with the paste density and the critical density for this sudden variation is about 76%. Furthermore, linear correlations of slump/viscosity and slump/yield stress were observed. It is possible to predict the viscosity and yield stress of the pastes based on the slump measurements.

Jan 1, 2014

By A. Buchanan, M. Mirnezami, A. L. Restrepo, J. A. Finch, M. S. Hashemi

Settling rate studies on slurries from Cu/Zn flotation plants occasionally revealed two aggregation maxima at pH 8-10 and 10-12. From measurements on sphalerite and silica suspensions the double maxima were replicated by Zn ions (pH 8-10) and Mg ions (pH 10-12) corresponding to the presence of zinc hydroxide and magnesium hydroxide, respectively. A combination of chemical and electrostatic bridging by the hydroxides is considered to be the aggregation mechanism.

Jan 1, 2003

By T. S. Qiu

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

Jan 1, 2014

By A. D. Bas

Copper minerals present difficulties during the cyanide leaching of gold ores leading to excessively high consumption of cyanide (and oxygen) coupled with low extraction of gold. Copper cyanide species, if present at high levels, adversely affects the downstream processes such as the activated carbon adsorption and the effluent treatment. In this study, the extraction of gold from a copper-bearing gold ore by ammoniacal cyanide leaching was studied. Furthermore, ammonia leaching as a pretreatment process ahead of cyanide leaching was also examined. Only ~12% of gold was extracted by direct cyanide leaching of the ore. The addition of lead nitrate did not affect the leaching of gold. When ammoniacal cyanide leaching system was used, the extraction of gold was significantly improved to >90%. Similarly, the pretreatment of the ore by ammonia leaching was shown to lead to high gold extractions (98%), in subsequent cyanide leaching with significant reductions in the consumption of cyanide. This appeared to be linked with the ready dissolution/removal of copper during ammonia leaching.

Sep 1, 2012