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By P. M. Solozhenkin

"Galvanochemical process (GChP)) cleaning of sewages is realized in the field of shortcirquited galvanic elements from the mixture current the materials place in purification’s solution and form multitude galvanopairs without external electric field in presence oxygen of the air. The galvanochemical process is electrochemical process utilizing galvanic pairs: coke - iron, iron - copper and others and process does not require chemical reagents.The effect of basic parameters of the cleaning effectiveness have been studied depending on oxidizing of galvanopairs. Adjusting nature, type of galvanic pairs and forming three component system possible to enlarge emf circuits to 2.378 V.The role of ?2, as basic agent, for generation of hydrogen peroxide and hydroxyl ions.It was stated, that removing of metal ions from solutions occur mainly on account of sorption and hydrolytic sedimentation of iron oxihydrates.Determined separate stages of the process: coagulation, sorptions of admixtures on freshly formed ferric oxides and oxidizing destruction of organic components of effluents in presence of ?2 ? ?2?2. Shown efficiency of the method for removing of Cu, Cr, Ni, Zn, As ions, as well as fluoride, phosphate and cyanide anions and oil products, surface-active and flotation reagents. Cleaned water can be recycled for some processes non-critical toward residual concentration of admixtures, as total salt contents is lowered on 60-75 % and reaching limits of concentration for toxic components.The concept of high power unit creation was developed, and galvanochemical pulsator is presented. The pulsator is not expensive, and exploitation expences are low, as well as servise is simple with high effectiveness, and capacity. The galvanoflotation process is developing, combining galvanochemistry and flotation of hydrofobic admixtures (oil, surface-active agents).The galvanochemical flotators are presented."

Jan 1, 2003

By Hamid-Reza Manouchehri, Hassna Aitahmed-Ali, Stellan Sundberg

"In flotation practices as the particle size becomes fine, e.g., p<20µm, the process efficiency declines markedly. When flotation of fine particles is necessary, one method to improve the recovery is selective agglomeration of fines. Different agglomerating methods have been introduced and tested; however, one method which has recently received great attention is to aggregate fine particles by magnetic force. A selective aggregation of the fine paramagnetic particles, e.g., sulfide minerals, can be achieved by applying a high intensity magnetic field during flotation conditioning. The method is simple, selective and effective for fines, and has a low operation cost. However, a minimum magnetic susceptibility of fine grains is required for this process. This method has been demonstrated in different sulfide minerals flotation plants. The implementation of the magnetic conditioning device, ProFlote, in both the Cu-Pb and the Zn circuit of Boliden’s Garpenberg plant in Sweden, where a complex massive sulfide ore is treated, is discussed herein. The preliminary results have shown an increase in the recovery of value minerals, in particular Zn and Ag and considerable reduction in Zn deportment to the final tail. Increases in Cu grade and decreases in Pb grade in Cu-con have been achieved as well."

Jan 1, 2014

By Cristian Melipichun, Leopoldo Gutierrez

The effect of the presence of fine particles of kaolinite and montmorillonite on the induction time for attachment of bubbles to particles of a copper concentrate rich in chalcopyrite was evaluated in this study. The results obtained from induction time measurements were correlated with data of concentrate recovery achieved from micro-flotation experiments. The effect of the presence of fine clays on the stability of air-water foams was also studied through measurements of the foam volume generated in a glass column under different conditions of air flowrate and MIBC concentrations. The experimental results showed that induction time values increased under the presence of fine clays. These data agreed with results obtained from micro-flotation experiments that showed that copper concentrate recovery decreased when clay particles were added. Although a complete explanation for these results is not available, the fact that experimental observations indicated that fine clay particles tend to adsorb on gas bubbles, suggests that the interactions between fine phyllosilicate particles and air bubbles have to be taken into account when studying the effect of clays on froth flotation. Foamability tests showed that the presence of fine clay particles increased the foam volumes only at high additions of clays and low dosages of MIBC. The results obtained at higher dosages of MIBC showed that the foam volumes decreased with the addition of clays under all the experimental conditions tested.

Jan 1, 2014

By Verónica Fernández, Jaime Solari

"The Chilean Environmental Impact Assessment System (EIAS) of investment projects was created in 1994, date in which the General Environmental Law was enacted. The compulsory environmental approval of projects began in 1997 when the Regulation (S.D. 30/97) was officially issued. By beginning late to regulate the environmental effect of investment projects, Chile could take advantage of the international experience in the matter and therefore, the EIAS has many of the attributes of successful environmental assessment systems elsewhere. Thus, the main characteristics of the Chilean EIAS are: preventive, single-window, specific to certain projects, multi-agency assessment at the regional scale, 3 kind of applications, deadlines, citizen and native communities participation, link to relevant permits, definite conditions of approval/rejection, review of applications by an ad hoc institution. The Chilean EIAS has allowed during the period 1997-2013, the review of 21,110 projects for a total investment value of US$ 408 billion, of which a 76% have been approved. In the case of the mining projects, the corresponding figures for the similar period are 1,257 projects for a total investment value of US$ 119 billion, of which 78% projects were approved. The experience derived from the environmental impact assessment of mining projects indicates that Chile has been successful in linking together mining development with environmental protection. There is still little prejudice against mining and this is a still a largely welcome economic activity at all levels in the relevant regions of the country. The challenge that mining companies face today in Chile is to improve the sustainability of projects and operations, by learning to share scarce and valuable resources (water, glaciers, renewable energy) with the local and native communities, through a process of dialogue whereby mining development also generates benefits for these communities."

Jan 1, 2014

By Stuart Simpson

The biggest environmental challenge in mining is the management of mine tailings. Deep----sea tailings placement (DTSP) is practiced where the environmental impacts are predicted to be less than the impacts of tailings storage facilities on land. However, DSTP is often highly controversial owing to the challenges in assessing the impacts in deep water environments and potential long----term impacts beyond the proposed tailings footprint. It is well recognized that total contaminant concentrations are often poor predictors of the risk posed by contaminants in sediments. Metals within tailings are mostly present in highly mineralised forms that are typically much less bioavailable to organisms when compared to other common anthropogenic metals. Thus while metal concentrations in tailings can often appear alarmingly high, when compared to sediment quality guidelines (SQGs) used for assessing common urban and industrial impacts, the bioavailability is typically low. Although now well----embedded within risk----based sediment quality assessment frameworks, contaminant bioavailability is still often overlooked in the management of contaminated sediments. In this presentation, we assess and demonstrate the low bioavailability and chronic ecotoxicology of mineral----rich tailings to two benthic invertebrates, recognized for their sensitivity to metals: impairment of reproduction of the amphipod, Melita plumulosa, and the harpacticoid copepod, Nitocra spinipes. We demonstrate that the metal exposure from mine tailings is low when total concentrations are considered, and that the dose to the organism and toxic response observed is highly dependent on contaminant bioavailability. We discuss a range of approaches for the effective incorporation of metal bioavailability when applying SQGs or setting site-specific management limits for mine tailings in marine environments. While proposed DSTP operations require a high level of environmental scrutiny and monitoring during operation and post-closure, environmentally sustainable operations may be achieved when the bioavailable forms of metals within tailings remain below suitable management limits.

Jan 1, 2014

By Willis Forsling, Prabhakar Swarna, Hanumantha Rao Kota

"The solubility of wollastonite and its Hallimond flotation behavior as a function of dodecylamine concentration and pH are examined. The flotation response is characterized by adsorption and surface energy in the presence of amine. The methods of UV-Visible and FT-IR spectroscopy for adsorption and sessile-drop contact angle for surface energy estimation are employed.The results of wollastonite dissolution clearly showed its non uniform dissolution. The surfaces are depleted with calcium ions and became rich in silicon within 10 min of flotation time. Maximum flotation of wollastonite corresponds to a half monolayer coverage of amine, which is substantiated by the surface energy parameters as shown in figure 1."

Jan 1, 2003

By Frank van der Meer, Lea Quincke

"High Pressure Grinding is applied to achieve size reduction of the particles by inter-particle breakage and to generate micro-cracks in the product particles as a contributing factor in e.g. leaching or mineral liberation. As alternative to classification, a closed circuit operation for HPGR can be established by product recycling, where a proportion of the coarser edge material and parts of the center material are split-off to be recirculated to achieve a finer final (center) discharge product for subsequent processing steps as ball mill grinding or beneficiation. As a result of the product recycling, the content of fines in the feed material increases and may affect the grinding efficiency in terms of production of fines and the generation of micro-cracks in the particles. In the scope of this paper, the effects of the proportion of fines in HPGR feed on grinding efficiency and micro-crack generation were evaluated. Grinding tests were executed with different feed size distributions, from a fines-void situation (truncated feed) to a fines-abundant situation (high product recycle). The evaluation of grinding efficiency and generation of micro-cracks was done by particle size analysis, Bond Work Index tests, impact tests on HPGR feed and products, and X-ray computed tomography of single product particles. This publication summarizes the main aspects of the outcome of these investigations."

Jan 1, 2014

By Nóra Schreithofer, Zoltán Jávor, Kari Heiskanen

"One of the challenges the mineral processing industry is facing is caused by the fact that water resources in mining areas are becoming very limited and the cost of water is increasing. The water sources in arid regions often have high salt content. Environmental regulations are forcing plant operations towards completely closing the water cycles within plants. This means that impurities (salts, reagents, ions dissolved from minerals, etc.) accumulate within the circuit that will affect the flotation performance. Water purification can significantly increase the operating costs therefore it should be carefully considered weather the impurities need to be completely removed or is there a tolerable level of impurities that can still be left in the process water without significant deterioration of the flotation performance? Several additional questions arise: what are the tools that help identify what is a tolerable level of impurities? How do the different impurities interact and what is their effect on the process? The effect of frothers on the dynamic properties of air/liquid interface in different size-scales has been extensively studied by the authors in the past. Based on these studies a frother characterization framework was developed that systematically examines the dynamic surface properties of the air/liquid interface in relation to the bubble size. This work can be considered as tool that could be used for the above mentioned purpose. The present study investigates weather the same frother characterization framework can be applied for systems where both frother and different types of salts are present. Nasfroth 240 was used as a frother, in combination with structure-breaker KCl or structure-maker NaCl and CaCl2. Bubble size measurements in laboratory scale mechanical flotation cell and laboratory flotation column and dynamic surface property measurements (dynamic surface tension and dilatational elasticity) were performed. The results highlighted the addition of salt to the frother solutions significantly decrease the bubble size and increase the froth high. The coalescence behavior of bubbles showed correlation between the D32 and ionic strength of salts. The results highlighted that the studied structure maker and structure breaker salts effect the dynamic surface properties in different way."

Jan 1, 2014

By M. Pelser, Lorenzen L.

"The presence of calcium and magnesium in the hydrometallurgical processing of base metals, results in a number of process difficulties. These problems range from the contamination of the final product (where the final product is a precipitate) to high energy consumptions and large bleed streams during electrowinning. Calcium poses an additional problem in sulphate solutions owing to the low solubility of its sulphate salts. This can easily lead to a process stream that is supersaturated with calcium sulphate, resulting in unwanted solids formation within the process equipment.A review of literature has proven that there is no conventional method for the control of calcium and or magnesium, although a number of potential processes have been identified. The technologies investigated included precipitation, ion exchange and solvent extraction, for which at least one method was found under each. To make the reader aware of these processes a short description was provided of each within the text.Of these processes, fluoride precipitation was selected for experimental investigation based on the low solubility of calcium and magnesium compared to the base metals. This process involves the addition of a soluble fluoride to precipitate CaF2 and MgF2. The experiments were designed to investigate the equilibrium of the system at varying parameters of which the level of fluoride addition, the ratio of calcium to magnesium, and the identity of the soluble fluoride was reported. In all of the instances the process showed high selectivity towards calcium and magnesium over the base metals. The experiments proofed the process to have a higher affinity towards the removal of magnesium at compositions where the molar ratio of calcium to magnesium was higher than 1:3. It is often the case that the calcium to magnesium ratio is in the region of 1: 10. From this it follows that the fluoride addition has to be stoichiometric or greater for calcium and magnesium combined, if the calcium is to be precipitated. This was demonstrated as well. On the identity of the soluble fluoride hydrogen fluoride was compared to ammonium fluoride, of which the latter was found to be preferred."

Jan 1, 2003

By Andrew T. McBride, Malcolm S. Powell, Indresan Govender

"Current empirical Semi Autogneous Grinding (SAG) mill models contain assumptions concerning the amount of energy available for particle breakage, how this energy is distributed in the mill media and the rate at which the energy is transferred. Despite these assumptions the JK SAG model is highly functional with a proven track record. DEM provides a numerical framework to greatly improve on these assumptions that were necessary due to a lack of available input data.This paper identifies key outputs of the Discrete Element Method (DEM), such as energy spectra and impact probability distribution. It describes how they can be incorporated into current mill models utilising practical rock breakage data. The rate at which energy is transferred is shown to be dependent on particle position and mill rotational speed and not once per cycle as previously assumed. Based upon this an improved energy transfer methodology is presented. The fundamental outputs of the DEM are validated against experimental three-dimensional particle tracking data, so as to establish whether the DEM produces correct energy transfer predictions on the inter-particle level, which is crucial to this work. • Effective Experimental ValidationAn automated 3D tracking technique is employed to study the motion of plastic particles deep within the charge of a 142mm diameter experimental mill. A Biplanar Angioscope is used to film the mill with X-rays in two planes simultaneously at 50 frames/s, with a shutter speed of 1/3000s. A marked ball within the charge is tracked for over 2 minutes and the resulting digital images processed by a fully automated imaging technique, which locates the 3D coordinates of the particles to within 0.2mm. With over 250 circulations, this provides statistically rigorous and accurate data for verification in the numerical modelling of mills.A series of validation techniques have been developed to compare the experimental trajectory data with the outputs of both 2D and 3D DEM simulations. The techniques describe the shape of the charge and the particle motion within mill, allowing objective comparisons to be made of key features of the charge, such as the equilibrium surface and the centre-of-circulation."

Jan 1, 2003

By Katsunori Okaya, Toshio Inoue

"Movement of mill charge in the centrifugal mill is essentially dissimilar from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. This dissimilarity is the reason for the substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Bradley et al. (1983) developed a math model regarding the mill charge as a lump. This model is presented in a simple equation with which motion of the mill charge can be predicted in terms of the parameters describing the specification and the operation of the centrifugal mill. This equation can be used to explain the power draft of the mill as well as the stability of mill operation. More recently, on the other hand, a numerical simulation technology called discrete element method (DEM) has become a vital vehicle for estimating the motion of the grinding media in the mill. The authors developed a mill simulator called ‘Mill Solver’. Mill Solver is designed to simulate various types of mills including centrifugal and vibration mills. The principle of this simulator is to calculate individual kinetic events of interaction of balls in the mill in a minute time interval, hence the mill performance can be constructed for estimation."

Jan 1, 2003

By G. S. Hansford, G. E. Searby

"Ferrous iron oxidation kinetics was measured in continuous culture at temperatures between 65 and 75ºC, using thermophilic microbes suitable for high temperature bioleaching. The resulting specific oxidation rates were modelled as a function of the ferric/ferrous iron ratio. The results were compared to those obtained by conventional mesophilic microbes.Microbially mediated ferrous iron oxidation is a vital sub-process in the mesophilic bioleaching of sulfide minerals and is expected to be of similar importance at elevated temperatures using thermophilicmicrobes.A thermophilic archaeal culture used in chalcopyrite bioleaching was successfully grown in continuous culture on ferrous sulfate, indicating the capability of the microbes to sustain growth for long periods on the energy provided by the conversion of ferrous iron to ferric iron, the primary leaching agent in sulfide mineral bioleaching.Steady state data was obtained at residence times of between 70 and 10 hours, with washout occurring at residence times between 11 and 9 hours, corresponding to a maximum growth rate (µmax) of between 0.09 and 0.11 hr-1. The reactions were followed by measurements of the solution redox potential, soluble iron concentrations, and offgas analysis of the oxygen and carbon dioxide utilisation rates."

Jan 1, 2003

By K. W. Stöckelhuber, A. Wenger, H. J. Schulze

"An important elementary step of the flotation process is the forming, drainage and rupture of a thin intervening liquid film between bubble and mineral particle.After the encounter of the bubble with the solid surface a wetting film is formed. The initial thinning of this film is driven by the capillary pressure inside the bubble. When the film has reached a certain thickness rupture can take place. There are two possible mechanisms describing this process:(a) Gas nucleation, caused by nano bubbles inside the film.(b) Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive forces (electrostatic, van der Waals).Metastable wetting films on negatively charged, hydrophobic glass surfaces (gaseous phase methylated), or on hydrophilic, positively charged glass surfaces (with Al3+ ions), have been analysed by means of the kinetics of film thinning according to the Reynolds law. These experiments demonstrate that both mechanisms can be responsible for the rupture of a thin wetting film."

Jan 1, 2003

By Rod Hocking, Nenad Djordjevic, Randolph A. Pax

"Semi Autogenous (SAG) mills exhibit complex interactions between the competing processes occurring inside them. Traditional practice is to measure the operation of the SAG mill at an operating point in terms of its load, power draw, steel load, ore throughput rate, water addition rate and more recently the feed size distribution. However significant departures from standard operating conditions can occur due to changes, for example, in ore hardness, the quest for higher throughputs and mill internal geometry.Fundamental to SAG mill operation are the internal processes that ensure that a given ore throughput and discharge grind size are obtained and maintained. These processes can be measured using non-contact acoustic emissions from the SAG mills which utilise the information rich noise that is generated by the grinding, flow and charge movement inside a mill. Non-contact acoustic in-mill measurements can be used for the validation of discrete element modelling (DEM). The approach being reported in this paper is to model the individual physical processes and then to simulate the assemblage of a physical mill.By modelling the assemblage of steel balls in a 1 m pilot mill and duplicating the experimental arrangement exactly with the PFC3D model, it was possible to replicate the pattern of falling balls in the experimental mill. Furthermore, the key features of the acoustic emission spectrum that was calculated compared favourably to the measured spectrum at low frequencies. The experimental spectrum is shown in Figure 1."

Jan 1, 2003

By Markus A. Reuter, Bernardete Castro, Antoinette van Schaik, Han Remmerswaal

"INTRODUCTIONThis paper describes the inseparable relation between product design, liberation, and metallurgical recovery in the optimisation of the recycling of passenger vehicles. This is illustrated by the use of an optimisation model that uses among others a material combination matrix based on metallurgical process data, which depicts the consequences of the quality of intermediate recycling products on the metallurgical material recovery and final alloy metal quality. Various simulations will illustrate the effect of changes in product design and hence liberation on the recycling of end-of-life vehicles. Although this paper focuses on cars, the discussion is equally valid for any end-of-life product. Calibration of the model will be discussed with reference to experiments carried out in order to study the optimal recovery of aluminium applications used in passenger vehicles.OPTIMISATION MODEL FOR LINKING DESIGN TO RECYCLINGImproving the efficiency of the material cycle of the car is essential to ensure a sustainable development of our society as well as e.g. to comply with the recycling targets imposed by EU legislation. In the design of the car various materials are combined and connected in many different ways, making up the complex 'mineralogy' of the car and its components, which is changing rapidly and continuously over time. The liberation of materials during shredding plays an important role in the composition (and quality) of the intermediate recycling streams. In order to include the influence of product design (mineralogy), liberation, and particle composition (quality of the intermediate recycling streams) in the optimisation of the recycling of end-of-life vehicles, a systems engineering tool for optimisation of the recycling of end-of-life vehicles was developed, including a liberation model. The optimisation model predicts the recovery rate as a function of product design (in this case a car), liberation, efficiency of the different process steps, economy and legislation based on a developed recycling flow sheet for end-of-life vehicles. Optimisation can only be achieved through the combination of the knowledge areas of product design, shredding, mechanical separation technology linked to pyro- and hydrometallurgy, composing a complex interconnected network of unit operations."

Jan 1, 2003

By Tatyana A. Ivanova, Tamara N. Matveyeva, Anatoliy A. Fedorov, Tatyana V. Nedosekina, Valentin A. Chanturiya

"As native gold resources are depleted, gold-sulfide ores consisting essentially of pyrite, arsenopyrite, chalcopyrite and pyrrhotite become one of the major precious metal sources, being presently estimated to account for more than 40 % of total world gold reserves.The prime objective of flotation of gold-bearing sulfide minerals is to increase precious metal recovery and to reduce the product cost through achieving maximum selectivity of the separation process. Separation of Fe and As sulfides in selective flotation of gold-bearing ore products helps reduce the amount of ore mass being sent to hydrometallurgical processing, and permits of recovering gold from As-free gold-containing pyrite concentrate by using a lower-cost pyrometallurgical procedure.An ingenious methodology purposively developed by the authors for comprehensive assessment of flotation properties, electrophysical characteristics and crystal chemistry features of natural gold-bearing sulfide minerals of different origin has been used in this study.Comparison of the elemental composition, non-stoichiometry and flotation activity of different monomineralic pyrite varieties revealed that samples with negligible impurity content are nearly stoichiometric, and show similar flotation properties. Samples with high Cu, As and Au contents are highly non-stoichiometric and readily floatable, even in a highly alkaline environment. Samples with high surface sulfur content and the most defective crystal lattices, with iron atoms substituting for sulfide vacancies, are most sensitive to depressive action of the alkali.A correlation between the type of conductivity, impurity content and amount of xanthate compounds on the surface and in the liquid phase of monomineralic pyrite and arsenopyrite suspensions detected by the extractive spectrophotometric analysis has been identified and analyzed. Experiments showed that the proportion of cuprous xanthate in sorptive collector layers on sample surfaces increases with increasing Cu content of the samples. In general, pH for pH, overall xanthate sorption on pyrite is greater than on arsenopyrite, with the difference increasing in passing from an acid environment to an alkaline one. A significant decrease in xanthate sorption on arsenopyrite is observed at pH greater than 9, whereas sorption on pyrite markedly decreases at pH greater than 11."

Jan 1, 2003

By Naoki Hiroyoshi, Hajime Miki, Tsuyoshi Hirajima, Masami Tsunekawa

"Acidic solutions for chalcopyrite leaching contain cupric, ferrous and ferric ions, and the oxidizing power of the solutions is indicated by a redox potential, determined by the concentration ratio of ferric to ferrous ions. This paper reviews our previous studies on the redox potential dependence of chalcopyrite leaching in sulfuric acid solutions. Leaching experiments indicated that copper extraction rate was accelerated by cupric and ferrous ions , and was higher at potentials below a critical value (critical potential) in the presence of these ions. This was in good agreement with the results of electrochemical measurements, i.e. in the anodic polarization curves for a chalcopyrite electrode, active-passive behavior was observed when cupric and ferrous ions co-exist, but the activation at low potential did not occur without these ions (Figure 1). The analysis of the AC impedance spectra for chalcopyrite electrode indicated that a high-resistance passive layer grows on the chalcopyrite surface without cupric and/or ferrous ions, and that coexistence of these ions causes a formation of another product layer and inhibits the passive layer growth at low potentials.These results are explained by a reaction model assuming the formation of intermediate Cu2S due to chalcopyrite reduction and the subsequent oxidation of the Cu2S. The critical potential corresponds to the redox potential of the Cu2S formation and the predicted values matched with the experimental results. Catalytic effect of silver ions on chalcopyrite leaching was also discussed based on experimental results and the above model."

Jan 1, 2003

By Peter Rubie, John Russell

"For many years, optimizing the relining of hard rock grinding mills has been complicated by the large number of variables, the low frequency of relines (resulting in a slow relining experience assessment and review cycle), and the potential economic risk associated with some changes to relining equipment or work practices. A technology that has its roots in the automotive manufacturing industry is being utilized to construct a statistically accurate, configurable, and dynamic simulation of the mill relining process. The detailed effects of various mechanization and process changes can be rapidly modeled and compared. Application of this discrete event analysis technology in the mineral processing industry delivers a range of benefits to many industry stakeholders. For example, mill maintenance managers and contract relining companies can embrace the opportunity to benchmark current performance against world’s best practice. Concentrator plant designers and mill manufacturers, informed by this technology’s scientifically defensible data set, can accurately plan for maximum plant efficiency when designing an infrastructure and equipment combination that truly maximizes annual plant availability. Time-motion studies of grinding mill reline data at mills of varying dimensions, liner configurations, mill relining equipment, operator and tool variables, have been integral to the development of this dynamic simulation tool and its associated data set. Access to mill relining simulation technology will enable mineral processing industry professionals to take advantage of an increased capacity to develop mineral concentrator performance optimisation initiatives within the given financial, physical and technological constraints of the individual concentrator plant."

Jan 1, 2014

By Gülay Bulut, Mustafa Özer, Yunus Emre Benkli, Olgaç Kangal, Istanbul Technical University, Mustafa Tarkan

"Zeolites are naturally occurring as hydrated aluminosilicate minerals. They belong to the class of minerals known as “tectosilicates” and are related to the common minerals feldspar and quartz. Seven natural zeolites that occur in large, commercially exploitable deposits, are: clinoptilolite, chabazite, mordenite, phillipsite, erionite, analcite, and ferrierite. Among them, clinoptilolite is the most abundant one and is not the best known, but is one of the more useful natural zeolite. Clinoptilolite [(Na3K3) (Al6Si30O72) 24 H2O] is very closely related to heulandite and is currently being considered for disuse it self as it may just be a variety of heulandite. It differs from heulandite significantly only in its enrichment in potassium and slightly more silica and it is argued that a separate mineral is not needed.There are large zeolite deposits in western part of Turkey. The sample used in this study was taken from the Gördes region of these deposits. Screen, chemical, XRD and mineralogical analyses were used to determine properties of the natural zeolite sample used in this work.According to the size distribution of the sample, it is found that the zeolite sample used in this study is below 1 mm in size and almost 80% of it is below 0.5 mm. X-Ray Diffraction (XRD) and mineralogical analyses show that the natural zeolite is found to be in the forms of clinoptilolite and heulandite. Clinoptilolite forms as a devitrification product of volcanic glass in tuffs. Quartz, clay minerals, orthoclase, plagioclase, biotite, seruzite-muskovite and epidote were observed as impurities. XRD analysis also shows that the sample contains approximately 58-60% clinoptilolite, 5% quartz, 5% feldspar, 10% smectite, 5- 10% illite and mica and remaining volcanic tuffs. Several types of mineral processing methods were performed in order to remove impurities from the natural zeolite sample to produce high purity zeolite. Gravity separation methods such as shaking table and superpanner were carried out for separating heavy minerals, while high intensity dry magnetic separation was used for discarding magnetic minerals."

Jan 1, 2003

By Zoran M. Stevic, Mirjana M. Rajcic-Vujasinovic, Zvonimir D. Stankovic

"Covellite is one of the most important copper sulfide minerals. Its behavior during the anodic polarization, as well as its rest potential in various solutions are of importance for flotation processes and also define the mechanism of electrochemical extraction of copper from sulfide minerals.Measurements of the rest potential have been performed in water solutions in presence of different cations and anions. The existence of the Nernst type dependence of the rest potential on the activity of some of the investigated ions was established. The biggest influence on the rest potential of covellite exhibits the change of activities of the ions forming the crystal lattice of investigated mineral, i.e. Cu(II) and S(II). The dependence of the rest potential of covellite on logarithm of Cu(II) activity has a shape of a strait line with a positive slope of 60 mV, while when concentration of S(II) anions increases ten times, the rest potential of covellite decreases about 120 mV. The first dependence was established in acid medium, while the second was registered in alkali one.Different electrochemical techniques have been used for the investigation of the behavior of covellite during anodic polarization. In the basis of all these measurements is a three electrode system consisted of: 1) working electrode made of the sample of natural covellite from the Bor mine (Eastern Serbia, Yugoslavia); 2) reference electrode (saturated calomel electrode) and 3) counter electrode (flat platinum). Electrolyte solutions used in these investigations are of the same kind as those used in the rest potential measurements. Sulfate and chloride solutions, as well as the mixed sulfate/chloride solutions, are the most perspective from the application point of view.Cyclic voltammetry has been the first used method that confirmed the formation of passive layer on the electrode surface during anodic polarization. Elementary data about the reaction mechanism have been obtained too. More detailed data needed for more precise conclusions about the mechanism and rate of the anodic process on covellite have been obtained by galvanostatic method. It was established that the essential difference exists between the reaction mechanism in sulfate and chloride solutions. Also, the difference is exhibited in the nature of reaction product directly connected with the passivation of the electrode surface. Chronopotentiometric investigations have been performed in sulfate, nitrate, chloride perchlorate and mixed sulfate/chloride solutions applying different current densities. The shape of obtained curves indicate if there was a surface passivation and how intensive it was."

Jan 1, 2003