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By B. Hosseini

Considering the subtractive trend of the sulfide and high-grade zinc ores in worldwide and also in Iran, Nowadays special attentions have been drawn to the extraction of zinc from its other resources such as low-grade oxide ores and secondary resources. Oxide ore of the eastern part of Mehdi-abad lead and zinc mine is silicate and has an average grade of 7% (with cut off grade of 4%). Main mineral of the Mehdi-abad ore is Hemimorphite and this mineral is associated with Goethite, Hematite, Ferrous Dolomite, and Manganese oxide mineral so that oxides of Iron, manganese and silica include almost 50% of the total ore. In this paper, the results obtained from the leaching kinetic study of the low-grade zinc oxide ore using Sulfuric acid are presented. The effects of particle size, reaction temperature, acid concentration, and solid percent on the dissolution rate have been investigated. The results obtained from the Taghochi approach showed that the zinc recovery is about 78% under the following optimized conditions: particle size: 106µm, leaching time: one hour, temperature: 45°C, acid concentration: 15% and solid percent: 15%. Kinetics study was revealed that zinc minerals leaching controlled by diffusion rate through the product layer during leaching time with the activation energy of 5 KJ/mol and compliance with the 1- (2/3. x) ? (1- x) 2/3 = k. t model. Keywords: leaching kinetics, kinetics models, sulfuric acid leaching, taguchi methods, low grade zinc ore, mehdi-abad mine

Sep 1, 2012

By P. Matias

The study involved two projects that will produce copper concentrate and may have their operations integrated. Transport by trucks, conveyor belt, and the equipment called RopeCon were evaluated as options for the ore transport between the sites. A rainforest stretch, that Vale S.A. demands to preserve, is situated between the projects. It was suggested to further review RopeCon because it presents minimal interactions with the environment. To design the preliminary system layout, a research was done on the rainforest cover height data, but the information found was scarce and imprecise. For preserving the local forest, the use of this data would conduct to the oversizing of RopeCon towers and, consequently, overestimation of its costs. For the acquisition of reliable information, a method was developed using local data acquired through airborne laser survey. The volume between the digital surface and terrain models was calculated to generate a surface representing the forest cover height. It was revealed, by plotting the points obtained from this surface, that 85% of the vegetation is below 25 m. This height is suggested to review the preliminary project with a more accurate design of the equipment towers, thus reducing its costs estimates. The method permits the precise location of the large trees, making easier to find a pathway, for linear-shaped facilities, that would minimize the creation of vegetation-free zones as a measure to protect equipments against falling trees and forest fires. Keywords: forest cover, mining projects facilities, digital models, airborne laser survey

Sep 1, 2012

By Y. S. Li

The life cycle assessment method is applied to investigate the environmental impacts of cop-per-slag and copper-ore concentration process. Some environmental load data of copper production are obtained. The result indicates that damage level of human health, ecosystem quality and re-sources respectively is 0.174, 0.0203, 0.246 in the copper-slag concentration and 0.112, 0.0136, 0.299 in the copper-ore concentration. Environmental impact of copper-slag production (0.44) is more than that of copper-ore production (0.42), but can meet the environmental protect demand. With domestic copper concentrate supply gap enlarging, recovering copper from slag will lead to a significant improving of resource utilization and development of circulation economics.

Jan 1, 2014

By Kevin Davey, Liza Forbes, Leanne Smith

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

Jan 1, 2014

By L. C. Zhou

The floatability of andalusite and associated minerals are studied and their action mechanisms of andalusite and associated minerals with collector alkyl benzene sulphonate are also studied. Through the mensuration of electrical potential and the infrared spectroscopy, as well as desorption tests, it is confirmed that the interaction of andalusite with sodium dodecyl benzene sulphonate (SDBS), is in addition to physical adsorption, but also is chemical adsorption. The study results of the pure minerals are used for the flotation of actual andalusite mineral. By flotation from contain-ing 45.68% andalusite ore, the fine andalusite concentrate is gained which Andalusite grade is 85.88%, containing Al2O355.29% and Fe2O3 less than 1.5%.

Jan 1, 2014

By L. Q. Luo

SHP-F3200 wet high-intensity magnetic separator (HIMS) was successfully used to separate the complex and weakly magnetic iron ores being composed of specularite, limonite and siderite in Ji-uquan Iron and Steel (Group) Co Ltd (JISCO). It is more and more difficult to separate iron ores from gangues, such as quartz, jasperite and phyllite, as the properties of iron ores gradually become more complicated and refractory. Some technologies have been used to improve SHP-F3200 HIMS, including modifying angle of magnetic polar from 90°to 83°, cooling exciting coils by oil instead of air, adding reverse-washing device to wash off magnetic particles, adjusting the tooth-space of matrix from 5.0 mm to 3.5 mm or 2.5 mm, so as to enhance the recovery of fine iron ore particles. It is still difficult to meet the requirement for recovering more difficultly-separated iron and the demands for high-grade concentrate of iron. In this paper, after analyzing magnetic force exerting on iron ore particles within different separating sections of SHP HIMS, it is proposed to apply the flowing-film technique into the HIMS. Thus a new-type LY matrix is designed to form magnetic gradient vertically, combined with a special flowing-film feeder to improve the existing SHP HIMS. The moving pattern of magnetic particles in pulp in HIMS separation district also has been analyzed in this paper. And the test on the SHP-F700 HIMS shows, under the condition of iron ore containing 30.52% Fe, with particle size of ?0.074 mm accounting for around 75%, if applied with flow-film technique, the iron recovery will be up from 69.45% to 76.07%, by 6.62 percent, with the same grade of concentrates of iron. The calculation of iron yield of every size fraction and the tests showed that film magnetic separation (Film-MS) could promote the iron yield of each size fraction, denoting an excellent result of application of the film technique to SHP HIMS. The mechanism of the film magnetic separation technique is to convert the turbulent flow and disordered movement of dynamic mass particles in the pulp into a directional and ordered laminar flow along the surface of tooth plate so as to strengthen the separation effects.

Jan 1, 2014

By Q. Cui, Z. G. Song, S. S. Lin, S. Q. Li, S. S. Lu, G. B. Zheng, A. J. Ren

"Mine tailings is one of the most important bulk industrial solid wastes, but its rate of comprehensive utilization is relatively low. Efficient separation, recovery and utilization of the valuable components is one focus of the comprehensive utilization of tailings. Beneficiation recovery of the valuable minerals is the most direct comprehensive utilization method for tailings. There are generally different kinds of nonmetallic minerals contained in the nonferrous metal mine tailings, which are secondary mineral resources waiting for further developing and recovery. Comprehensive utilization test studies on fluorite in tungsten beneficiation tailings and feldspar in molybdenum beneficiation tailings have been carried out by author and good test results are achieved. Some of the technologies developed in the test study have been applied in industrial productions, which have been working well. The economic, social and environmental benefits are remarkable. Our test studies and some production practices will be summarized and current situation and existing problems of comprehensive utilization for nonferrous metal mine tailings will also be discussed. Assumption and prospect for the future study on comprehensive utilization of nonferrous metal mine tailings will be brought at last.INTRODUCTION Mine tailings is one of the most important bulk industrial solid wastes, but its rate of comprehensive utilization is relatively low. Efficient separation, recovery and utilization of the valuable components is one focus of the comprehensive utilization of tailings. Beneficiation recovery of the valuable minerals is the most direct comprehensive utilization method for tailings. There are generally different kinds of nonmetallic minerals contained in the nonferrous metal mine tailings, which are secondary mineral resources waiting for further developing and recovery. Comprehensive utilization of nonmetallic minerals of nonferrous metal mine tailings not only can improve the value of the ore but also reduce the stock of tailings, being the key to reduce emissions at source for exploitation of nonferrous mineral resources (Cai, Yang, 2000)."

Jan 1, 2018

By Y. Y. Li, T. T. Yang, R. X. Zhou, Z. H. Shen

"Wetting theory is one of the basic theories of flotation. The effects of concentrations, carbon chain length and pH values of saturated fatty acid collectors (lauric acid, myristic acid, palmitic acid and stearic acid) on the surface wettability of collophanite and dolomite were investigated by measuring the contact angle with dynamic captive-bubble technique and calculating adhesion work of bubble-mineral. The results show that the contact angles both of collophanite and dolomite are higher with enhancement of hydrophobicity when pH value of 5~9. The contact angles both of collophanite and dolomite are reduced with improvement of surface hydrophilicity. When strong acid pH value of 2~4 or strong alkaline pH value of 10~13. The reasons for this are that the fatty acids mainly exist with insoluble RCOOH molecules in strong acid condition, and competitive adsorption of OH- and RCOO- in the mineral surface is formed in strong alkaline condition. With the increase of the collector concentration, the contact angles of the collophanite and the dolomite all first increase then decrease. The formation of hydrophilic micelles results in the decreasing of contact angles and enhancement of surface hydrophilicity opposite when the collector concentration exceeds CMC. The contact angles of the collophanite and dolomite and the WSG of the bubble adhesion increase, the hydrophobicity enhance with the increasing of carbon chains of saturated fatty acid from 12 to 18. The variation tendency for the adsorption quantity of collectors and floatability of collophanite and dolomite are in line with the change trend of contact angle basically. It shows that the wettability of solid-liquid-gas interface can be well characterized by the dynamic captive-bubble technique.INTRODUCTIONPhosphorite resources are the main raw material for producing phosphate fertilizer and producing phosphoric acid (Cao et al.,2005), which is an important strategic mineral resource. The useful minerals in calcareous-magnesium phosphate ore are collophanite, and the main gangue minerals are dolomite (SISH et al.,2003). The lattice ions of the phosphorite and dolomite are both Ca2+, their similar surface properties and similar floatability are the main reason for the flotation of calcareous-magnesium phosphate ore difficultly (Fang et al.,2011). Usually, fatty acid collectors are used for the flotation of calcareous-magnesium phosphate ore under acidic conditions by reversing flotation method to remove dolomite (ABOUZEID et al.,2009), or direct flotation is used to gather collophanite in the alkaline conditions (Gong et al.,2017). The flotation behavior of collophanite and dolomite affects the indexes of concentrate and flotation efficiency directly. Therefore, it is necessary to study the action mechanism and the flotation method of the collector with the phosphate rock and dolomite respectively (Moudgil et al.,1988; Hanna, et al.,1990)."

Jan 1, 2018

By X. Q. Ma

The beneficiation test on low grade phosphate ore from a state of Russia is carried out. The rougher-cleaner ? re-cleaner system is used in the flotation process, The fineness of grind is 39.07% minus 200 mesh. The result indicates that concentrate containing 31.25% P2O5 can be obtained from the flotation feed assaying 6.18% P2O5, with 93.54% P2O5 recovery. The test result is also a guideline for further development of some currently operated phosphate beneficiation plants.

Jan 1, 2014

By A. V. Nguye, P. A. Harvey

Previous studies have reported that inorganic electrolytes can enhance floatability of coal. The research has shown that the enhancement, if any, is highly dependent on changes in solution pH, type of electrolyte, and electrolyte concentration. The reasons for this are still not clear. In this study the floatability of coal particles in mono and divalent salt solutions was investigated. The zeta potential and hydrophobicity of the coal was measured experimentally, and a modified Hallimond tube was used to determine the floatability of coal particles by single bubbles, where the collision efficiency was equal to unity. The experimental information was used in conjunction with the Hogg-Healy-Fuerstenau equation to quantify the electrical double layer interaction. It was found that for low electrolyte concentration (less than 0.1 M) solutions the flotation recovery of coal particles was less than that for distilled water, and decreased with increase in concentration. Conversely, at electrolyte concentrations above 0.1 M, flotation recovery increased with increasing concentration. Both of these results are consistent with previous observations, but are inconsistent with expectations when considering the possible influence of electrical double layer interaction. A possible mechanism, based on the existence of the pre-existing submicron-sized gas bubbles, known as bubstons (i.e. bubbles stabilized by ions), present in water in close proximity to the hydrophobic coal surfaces is discussed in line with the early observation of flotation improvements by microbubbles “nucleating” on hydrophobic surfaces. In particular, the dependence of the bubble-particle attachment efficiency on electrolyte concentrations supports hypothesis on the salt-dependent and ion-specific existence of bubstons. However, a theoretical explanation of the transition salt concentration (at about 0.1M) is deficient at present. The existence of these submicrobubbles in close proximity to hydrophobic surfaces is not trivial. They can (as can individual gas molecules or other solutes) mediate and extend the range and magnitude of the attraction between hydrophobic macroscopic surfaces. These bubbstons may explain the curious phenomena of the socalled long-ranged hydrophobic attraction measured with the Surface Force Apparatus and Atomic Force Microscopy, and the slippage at hydrophobic surfaces. Finally, the coalescence of bubbstons affects the rupture of liquid films at a very large thickness (over 100 nm), observed, but unexpected, by flotation chemists.

Jan 1, 2003

By Q. Zhang

Phosphate tailings through Flotation contains large amount of dolomite which is difficult to be separated from apatite. In this present research, phosphate tailings is recycled by Flotation i.e. re-processing. High-purity dolomite with purity as high as 91.17% is seperated, which contains 19.82% of MgO. The results of orthogonal test show that the effect of various levels of different factors on the high-purity dolomite floatated. Future utilization of purified dolomite is also discussed: magnesium fertiliser especially magnesium phosphate is expected to be an ideal product from high-purity dolomite.

Jan 1, 2014

By F. J. Sotiuo

Variability of the quality of phosphate ore feed to the flotation plant has been of great concern for the industry. This variability sometimes resulted in 10% to 50% decrease of P2O5 recovery, a reduction of P2O5 concentrate grade and/or both due to depression of the system. For this investigation, samples of refractory ore and easy-to-float ore were obtained from the same mining area in Central Florida; and then submitted to bench flotation tests using fatty acids (FA). To understand the cause of difference in flotation behavior of these apparently similar ores (grade, mineralogy, and physical appearance), bulk and surface characterization studies were conducted. Based on the results of characterization studies and bench flotation tests on both refractory and easy-to-float samples, it was possible to determine FA surface coverage. It was found that the surface coverage for the refractory ore was between 6.9% and 9.8%, corresponding to 0% and 80% recovery, respectively; whereas the easy-to-float ore showed surface coverage of 17.2% (89% recovery) to 24.6% (98% recovery). Since size analysis, surface area and pore size measurements showed small differences, it was thought that the surface coverage differences could be caused by the ad-sorption of natural compounds onto the phosphate ore surfaces, depressing the system. SEM, EDS, and Leaching and Solvent Extraction (LSX) studies were performed on the phosphate ores to demonstrate the proposed mechanism. This paper summarized our characterization studies, flotation results, and findings. The study showed that the new identified compounds were responsible for the flotation behaviors of the Florida refractory phosphate ores.

Jan 1, 2014

By S. Sarioglan

The bleaching of edible oils, industrial oils, and some chemicals may be achieved using natural and acid-activated clays. These materials remove impurities and pigments from the oils. In this work, a bentonite clay from Turkey (Somas bentonite) was activated with different concentration of H2SO4 and HCl at 70~90°C and 5~8 hours. Under these conditions several cations were removed from natural bentonite (Al, Mg, and Fe) and DTA-TGA, FT-IR curves of the solids obtained after acid treatment were examined. Treatment time and acid concentration increased the degree of destruction of the bentonite structure which was determined by ICP. Activated samples were tested in order to verify their capacity to bleach soybean oil and compared to standard commercial bleaching clays. The experimental results indicate that treated samples with H2SO4 have the same efficient in bleaching crude soybean oil with the standards and treated sample with HCl is more efficient in bleaching than the commercial products.

Jan 1, 2014

By Sanjay Agarwal

Polymetallic sea nodule is a good source of manganese having 22.3% Mn, 5.4% Fe, 6.14% Si, 1.1% Cu, 1.15% Ni, 0.076% Co & others. These nodules are available in plenty on the sea beds, generated over thousands of years. Nodules mainly consist of manganese dioxide and iron oxide phases and other metals are entrapped in the complex cage of these Mn-Fe oxides phases.World-wide research is going on sea nodules as an alternative future source of many metals, which has led to intensified efforts to develop practical and economical processes for recovery of these metals. Very little attempt has been made world over on manganese extraction from sea nodules. We at CSIR-NML, India have developed a direct reduction smelting process of nodules to recover manganese as Fe-Si-Mn alloy. This alloy is extensively used in the steel industry as deoxidizer and as an alloying element to make different grades of steel. Lab scale experiments were conducted to study the manganese distribution between Fe-Si-Mn alloy and FeO-SiO2-MnO-CaO-Al2O3-MgO slag at different temperatures by varying the basicity of the slag. The direct reduction smelting of nodules is carried out on 1 kg scale in 50 kVA electric arc furnaces to have Cu, Ni and Co alloy and Mn rich slag. This manganese rich slag is further treated in 50 kVA arc furnace to produce Fe-Si-Mn alloy. The composition of Fe-Si-Mn alloy obtained is in the range of Mn: 60-65%, Si: 14-17%, C: 1- 2%, S: 0.03% and the balance iron which is acceptable grade for industrial use. The equilibrium amount of MnO in the final slag is controlled by the temperature of the final melt and the silica, lime, alumina content of the final slag. Increasing the basicity of the slag plays a major role in minimizing the loss of MnO to slag, increasing the amount of SiO2 of the slag, increases the manganese loss in the slag. Increasing the CaO/ Al2O3 ratio of the slag decreases the manganese loss in the slag. Increasing the MgO/CaO ratio of the slag increases the manganese loss in the slag. Thus by adjusting

Sep 1, 2012

By Christopher Robben, Alexander Mosser

"X-ray transmission (XRT) sorting has been introduced into the minerals industry in 2006 and has found various applications in diamonds, industrial minerals and metal ore processing since. The technology offers planar projections of the atomic density of single particles similar to the principle known from airport scanners, but being capable of treating up to 150tph per metre working width. In 2010, a pilot operation using a belt-type sensor-based sorter went into production at the Mittersill mine to treat the fraction 16-28mm. After an optimisation phase, the results were superseding expectations and therefore in 2012 a bigger production plant was set up. Two XRT-based sorters are parallel in operation since. One is treating the fine fraction 16-30mm while the other one is treating the coarser fraction 30-60mm after the secondary crushing stage. The XRT sorters are operated with the objective to reject barren waste before it enters the mill and flotation plant. 105,000tpa of waste material are rejected per year and can be sold as aggregate for road construction. This means that about 22% of the run-of-mine ore are rejected at an early stage with a waste reject grade lower than 0.03wt%WO3. The installation has not only led to lower specific operating costs but also led to reduced tailings disposal in an environmentally sensitive area. This allows the mine to reduce its headgrade which allows for a longer mine life. Alternatively it is possible to produce more tungsten concentrate, which is delivered to the smelter. This article will introduce the technological principle of XRT-based sorting and will discuss the flow-sheet of the Mittersill mine. Experiences that have led to the current plant design are described as well as the impact it has on the operation."

Jan 1, 2014

By Josefin Lannefors, Anders Klingberg, Natalija Gorochovceva

"Development of new anionic collectors becomes more and more important. This can be explained, on the one hand, by the fact that over the years phosphate ores have become more fine grained and complex (example weathered). On the other hand, a development with a focus on sustainability (sustainable development) of new anionic surfactants is required by authorities and society. Within the sustainable development several characteristics of a collector have to be taken into an account: efficiency, selectivity, froth characteristics, environmental profile, raw materials used for the synthesis, manufacturing complexity, stability upon storage, etc.Several anionic surfactants based on ester and amide chemistry were synthesized, characterized and used as flotation agents for calcium phosphate containing ore. The surfactants were used in a formulation together with other anionics, since in a pure form, during the flotation, they did not provide right froth characteristics.A new anionic collector/formulation was developed, that fulfills all above listed requirements."

Jan 1, 2014

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, A. Abazarpoor

"The morphology of pellet feed is known to influence several properties of iron ore pellets, including drop number, compression strength and reduction properties. The effect of grinding method on the particle size, specific surface area and particle shape of an iron ore concentrate has been studied. Grinding methods considered were ball mill and high pressure grinding rolls (HPGR). 5 different samples (Blaine= 1800, 1900, 2000, 2100 and 2200 cm2g-1) were used to compare the size, shape and specific surface of particles for each grinding methods. Particle size was meticulously examined by sieve analysis, laser sizing and image analysis. In samples ground by ball mill, it has been observed that the fraction of particles <10µm increases from 39% to 46% as the Blaine number increases from 1800 to 2200 cm2g-1. For HPGR samples, corresponding figures are 41% and 49% respectively. It is evident that for samples ground by HPGR, the fraction of fine particles is higher than that of those ground in the ball mill. To measure the specific surface area of particles, Blaine and BET were used. A higher real surface area was observed from HPGR treatment in comparison to ball mill grinding, provided by a higher porosity, cracks, roughness and new surfaces. Shape factor of particles was determined using three descriptors: circularity, roughness, and aspect ratio. It was also observed that particles produced by HPGR were more elongated, less circular, and rougher than those processed by the ball mill. 1. INTRODUCTION Particle size and shape are important parameters that can significantly affect mineral processing plants and pelletizing plant performances (Brozek and Surowiak, 2007). It has also been proposed that green pellet quality is directly related to the amount of fine particles in a pelletizing plant (Dwarapudi et al., 2008; Umadevi et al., 2008; Gul et al, 2014; Van der Meer, 2015). Particle size distribution and specific surface area (SSA) are also key factors that can control the quality of green and fired pellets. Processing circuits generally reduce the fines fraction to lower than the required specific surface area (SSA). It is therefore necessary to regrind concentrates to produce suitable pellet feed for further treatment in the balling and firing steps [1, 2]. Two main methods are used for re-grinding of concentrate; high pressure grinding rolls (HPGR) and ball mill. Given the different forces used to reduce size in these methods, it is expected the shape of particles will be different (Pourghahramani and Forssberg, 2005)."

Jan 1, 2018

The ultimate goal of a mineral processing plant is to recover as much of the target mineral(s) as possible from the ore being treated to achieve the best economics. Selection of the mineral processing techniques is the most important step in achieving this goal. However, due to the complexity of the ore, the recoveries of valuable minerals may be not satisfactory even when the mineral processing technique(s) are well chosen. In other words, minerals of interest can be lost to the tailings for mineralogical reasons. For example, gold is mainly extracted from the ore by gravity, flotation, cyanidation, or a combination of these processes, and high recovery (>90%) can be achieved when gold occurs as coarse grains. However, when a refractory ore is being processed, gold extraction will be challenged by mineralogical factors, which often cause gold losses to various tailings. Mineralogical factors affecting gold recovery mainly include grain size, shape, surface coatings and rimmings, presence of cyanicides, oxygen consumers and preg-robbers, presence of slow-dissolving gold minerals and the refractory nature of submicroscopic gold. Among these factors, locking in sulphide, silicate and other minerals as fine-grained gold inclusions and/or as invisible submicroscopic gold is by far the most common factor leading to poor gold recovery encountered in gold ore processing. Processing of PGE ores faces the same challenges as gold. Small grain size and locking of PGM in sulphide and non-sulphide minerals often cause PGM losses. When silver ore contains significant amounts of pyrargyrite, proustite and stephanite, silver recovery by cyanidation can be very low because of the slow dissolving kinetics of these minerals. In the processing of base metal ores, high content of pyrite, intergrowth of chalcopyrite with sphalerite and presence of clay miner-als may cause problems in recovering Cu-, Pb- and Zn- bearing minerals. Process mineralogy helps address all issues and problems related to mineral processing with predicting and trouble-shooting being two major objectives. It provides useful information on process selection, flowsheet development, recovery improvement and reagent consumption optimization. The information acquired from a process mineralogical study can be used as a guide for a metallurgical testwork program for process design or optimization.

Jan 1, 2014

Ca-containing gangue minerals such as Fluorite, Calcite have same surface activity point--calcium ions and approximate floatability with scheelite, it is difficult to achieve good dressing index of rough concentrate of scheelite. Mono-mineral experiments and ore tests indicate that, according to mineral composition, gangue minerals can be inhibited selectively by adopting suitable regulators, then the separation of scheelite from gangue minerals can be realized effectively. Mechanism analysis was taken by zeta potentials measurements and FTIR tests. Good dressing indexes are also obtained in practical ore tests and industrial tests. Keywords: scheelite, fluorite, calcite, regulator, flotation separation

Sep 1, 2012

By M. C. Harris

"In the flotation process the contact angle is an important indicator of the hydrophobicity of a mineral particle. There is considerable literature showing that the contact angle increases when the chain length of the alkyl group associated with the collector molecule used to render the valuable mineral particle hydrophobic increases. The extent to which an alkyl group interacts with surrounding water molecules is quantified thermodynamically by the excess Gibbs energy. In the present paper it is shown that there exists generally a strong linear relationship between the excess Gibbs energy of the alkyl group associated with the collector and the contact angle. The structure-activity of such alkyl groups is in turn related to the total surface area, molecular volume, the molar volume, molecular weight of the functional groups in the molecule and interaction energies. It is proposed that the demonstrated relationship is indicative of the role which the alkyl group component of the collector, which is attached to the mineral particle, plays in increasing the extent to which water molecules at the surface of the mineral are rejected from the surface thus increasing the contact angle. The relationship between excess Gibbs energy and surface tension is further explored with a view to relating the observations quantitatively to the parameters in the Young equation.INTRODUCTIONThe issue of wettability of materials is of great importance to many industrial applications. Wettability studies usually involve the measurement of contact angles which indicate the degree of wetting when a solid and liquid interact. As is well known the contact angle (O) is the angle between planes tangent to the surfaces of the solid and the liquid at the wetting perimeter which is the zone where the air, water and solid phase merge. When the air bubble attaches to the solid surface there is an increase in the air/solid interface area and a decrease in the solid/water interface area. For attachment to occur the cosine of the contact angle should be less than 1 and this will be promoted if the interfacial surface tension between the air and the solid (? SV) is low. Classically the relationship between these parameters has been expressed through the Young equation (1) for a perfectly flat surface:"

Jan 1, 2018