Search Documents

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 Yu. Gurevich, M. Teremova, I. Prokopev, A. Razvjaznaya, N. Algebraistova

"The objective of this work is the scientific justification and development of efficient and environmentally-friendly method of bulk concentrate preparation for selection with application of microbiological practices. This research suggests to apply Pseudomonas Japonica bacterial culture to the bulk concentrate before the selection circuit in order to clear the surface of sulphides from the xanthate skin. It is also suggested to apply bacterial consortium Ochrobactrum ?nthropi and Pseudomonas aeruginosa JCM 5962 for desorption of diesel residual concentrations. High-efficient and environmentally friendly method of copper-molybdene and lead-zinc bulk concentrate selection was developed based on theoretical and experimental research work with application of microbiological practices. In comparison with conventional methods (steaming, sodium sulphide washing) the above suggested bio-technological method of bulk concentrate preparation before selection cycle will allow to reduce material and power expenditures, and it is also environmentally friendly. INTRODUCTION High-efficient selection of sulphide bulk concentrate is gained exclusively after collecting agent is removed from mineral surface. Therefore, the problem of bulk concentrate preparing before the selection cycle is acute, since the further technological parameters of the subsequent separation depends on the effectiveness of pulp preparation. Existing traditional ways of bulk concentrate preparation. such as washing or steaming, are characterized by high energy and material costs in industrial conditions [1,2]. The microbiological treatment before separation of the bulk concentrate into different kind of concentrates appear one of perspective processes for treatment of bulk concentrates [3,4]. At the present time, the world practice of processing mineral raw materials demonstrates the wide application of technologies using microorganisms: bacterial leaching and oxidation, purification of industrial wastewater. This is due to the fact that biotechnological methods are environmentally safe, low-cost, and suitable for refining complex ores and raw materials of industrial origin."

Jan 1, 2018

By Tasuma Suzuki

Electrokinetic/permeable reactive barrier system is a promising in situ soil and ground water remediation technique to reduce toxic NO3- into less toxic NH4+. Using granular zero-valent iron (Fe0) as a reductant, the first objective of this study was to investigate the influence of the solid-liquid ratio and aqueouspHon NO3- reduction. The results obtained from a series of batch experiments showed that NO3- reduction was enhanced by either increasing solid-liquid ratio or decreasing aqueous pH. Based on insights obtained from batch experiments, the second objective of this study was set to design the remediation conditions of the electrokinetic/Fe0permeable reactive barrier system to maximize the NO3- reduction efficiency. Experimental results showed that the effectiveness of the system strongly depended on the Fe0 percentage in the reactive barrier, the pH in the anode reservoir, and the applied voltage, which were consistent with the results obtained from batch experiments. Under optimized treatment conditions, nearly 100 % NO3-was reduced into NH4+ in the permeable reactive barrier and collected in the cathode reservoir. Insights obtained from this study provided fundamental information on roles each of remediation design parameters plays, and will be useful to optimize the remediation conditions. Keywords: electrokinetic remediation, permeable reactive barrier, zero-valent iron, nitrate

Sep 1, 2012

By Reza M. Rahman, Seher Ata, Graeme J. Jameson

"This paper presents the results of a through investigation into the froth recovery measurements in a controlled plant environment using a device that allows direct collection of dropback particles from the froth phase. Test work was performed at the Northparkes concentrator (NSW, Australia), using a feed taken from the head of the cleaner scavenger bank. The feed slurry had a relatively higher copper grade varying from 5.2% to 6.8%. Experiments were performed to investigate the effect of important flotation parameters such as air flowrate on the froth recovery. The size of the particles in the relevant streams was also analysed to acquire in-depth knowledge about the froth dropback mechanism. The results suggested that the froth recovery could be as low as 70%, although it was relatively easy to achieve the values in the range 75% to 85% by the correct choice of operating variables. It was found that the air flowrate has a positive impact on both collection (pulp) and froth zone recoveries. However, the effect was more prominent in the froth zone. It appeared that the froth recovery is a strong function of particle size."

Jan 1, 2014

By J. Gebhardt, D. McBride, M. Cross, S. Gilbert

Heap leaching of ores containing chalcopyrite offers a low cost option to treat low grade complex copper sulfide ore bodies. However, the slow leach kinetics of chalcopyrite at ambient conditions typically results in unacceptably low recoveries. As the mineralogy of new ore deposits becomes more complex and the effects of gangue chemistry exert a greater influence on copper sulfide leach behavior, the control of leach reaction chemistry becomes more critical. Computational fluid dynamics (CFD) technology has been useful in the capture of multi-phase interactions and provides a path to simulate complex fluid flow, gas and liquid phases, through the heap, along with species transport. Coupling the flow models with the reactive mineral dissolution, and the sometimes competing aqueous chemical and solid-liquid reactions, yields a comprehensive model of the heap leach process. The leach kinetics of chalcopyrite dissolution in heap conditions is examined, and the incorporation of chalcopyrite leach kinetics in the CFD model is described. The application of the model to investigate optimization of the heap is discussed.

Jan 1, 2014

By Roberto Galery, Priscila Esteves, Braz Cardoso, Marcelo Stopa

"It was developed in this work a computational tool to aid in anomaly detection present in the operation of ball mills. The tool uses a torque estimator that is based on measurements taken exclusively in the drive motor. The ball mill equipment widely used in the mining industry has, inherent to its principle of operation, high energy consumption and low efficiency. These characteristics are accentuated when the mill operates outside the ideal conditions of velocity and loading. Direct measurement of these variables is extremely difficult because it requires the installation of sensors in moving parts of the mill. Thus, systems that can help monitoring the operating conditions and predict anomalies are useful because they contribute to improving the performance of the process, help to reduce the energetic consumption, wear on the mill surface and frequency of maintenance shutdowns. The detection strategy implemented in this work is based on the fact that operational anomalies such as an inadequate percentage of balls and incorrect angular velocity manifest itself as a change in spectral components of the torque signal in the mill driven by an electric motor. The mill torque was estimated by processing motor variables measured by sensors commonly used for control purpose and installed exclusively in the motor. The mill was operated at various fault operating conditions and signals from electric motor and vibration on the mill shaft were measured. The spectral components present in the estimated torque signal were then compared with signals from a vibration sensor in order to establishing a correlation with anomalous operation condition of the mill. The experimental results showed that the signals obtained has an excellent correlation with other variables obtained by direct measurement and have potential to be used to construct a system for automatic fault detection in the operation of ball mills."

Jan 1, 2014

By V. Dementiev

Pyrite cinders is a complex raw material, in which the valuable metals are: Au(2.04 g/t), Ag(35.0 g/t), Cu(0.38%), Zn(1.1%) and Fe(56.0%). In this case high costs for mining and ore processing are not required. The hydrometallurgical treatment of pyrite cinders using thiourea, sulfite and cyanide solutions are examined in this paper. It was found that thiourea leaching is ineffective due to high consumption of thiourea and sulfuric acid. The cyanidation on pyrite cinders was conducted. Various options of the preparation of the products for the subsequent cyanidation have been examined. The tests on cyanidation process optimization were conducted. The effectiveness of these cementation methods by metallic iron or extraction for copper recovery from water phase has been shown. Zinc precipitation can be found in the form of carbonate. In order to recover noble metals from cyanide solutions, the cementation onto zinc dust was tested. The developed technology provides for recovery at 49-56%Au, 20-25%Ag, 22.5%Cu and 50%Zn during NaCN (1.4 kg/t) and CaO (6 kg/t) consumption. The results of pilot plant testing are the basis for technical regulations in order to design a pyrite cinders treatment plant. The technology has been examined in pilot-plant conditions. In this case the recovery of 54.5%Au, 45.3%Ag, 30%Cu and 49.9%Zn was achieved to provide saleable products. Keywords: pyrite cinders, thiourea leaching

Sep 1, 2012

By Gabriel C. Aguilera, Juan Arismendy

"The effect of rheological factors inside of a hydrocyclone is very relevant for the fluid mechanics and for the classification of materials on suspension, since parameters such viscosity and thixotropy are intrinsic variables that depend of the particulate system and the continuous phase; they determine the efficiency of classification. Nevertheless, the exact knowledge of the main characteristics and magnitudes of them inside the hydrocyclone is very difficult because of the geometry of the hydrocyclone, even more if the hydrocyclone is of small diameter. Hence is not possible to make a hydrodynamic study with effects over classification regarding these variables. This work studies the rheological variables inside a small diameter hydrocyclone that works at high pressures, using the information given by a model of Computational Fluid Dynamics (CFD). The model used includes the Reynolds Stress Model (RSM) for the evaluation of turbulence, and the Volume of Fluid (VOF) to study the interaction between water and air, which is very important to obtain regarding the effect of the air core over the performance of the equipment. The validation of the CFD model was done with a kaolin suspension at several conditions of solids contents below the critical volume fraction, without chemical additive aid. These conditions are representative of current work parameters on plant. As result it could be established the ranges of evaluation of rheological variables on specific regions inside the hydrocyclone, and through a rheometric study, based on the mechanic characteristics previously obtained, the main rheological characteristics of the mineral suspensions were determined."

Jan 1, 2014

By Julian Dimitrov, Kremena Dedelyanova

"The paper presents research on hydrodynamic processes occurring at the elementary act of flotation. Discussed existing models to determine the effectiveness of conflict of bubbles with particles in vibration column flotation machine. The paper presents a disperser for a column flotation machine, in which the dispersion of the gas phase is carried out using vertical vibration with defined frequency and amplitude. The paper presents research of mechanism for the creation of air bubbles in vibratory column flotation machine. The factors influencing the increase in the duration of the bubble in the area of contact with the mineral particles are discussed. Research was carried out on the effect of frequency and amplitude of vibrations on speed of precipitation of mineral grains of different density. Formulas are derived for the parameter effect of vibrations, applicable to the design of flotation machine. The collision efficiency of the bubbles in vibratory column flotation machine is determined. The vibrations of the hydrated layer allow for cost-effective implementation of the elementary act of flotation by providing larger relative velocities at the contact point between the bubble and the solid phase. It is proposed to complement the model more accurate representation the mechanism of attachment of the particles to the bubble."

Jan 1, 2014

By X. H. Zhou

Column flotation is being widely adopted for fine particle treatment by the mineral processing industry due to its simplicity of structure, high efficiency and good separation performance. Cyclonic static micro-bubble column flotation (FCSMC) is an innovative column separation technology that has been successfully applied in the coal preparation industry in China. Recently, the application of this equipment has been further expanded to the separation of several minerals such as fluorite, copper, iron, etc. The bottom of the FCSMC is a cone in which cyclonic field is generated when circulating pump is injected tangentially into the column. The unique cyclonic structure is believed to help enhance the column separation performance. Since the FCSMC is a new flotation device, little work has been done to understand the fundamentals of this technology. In this research, a computational fluid dynamics software, ANSYS/ FLOTRAN, was employed to simulate the flow field of a lab FCSMC system (F0.2 m, F3.0 m by length.) The distribution patterns for velocity field and flow field were investigated under single phase condition. It has been found that axial velocity of the slurry decreases and becomes stable along the height of the column from bottom to top, and the slurry performs as a descending flow pattern. Another observation is the velocity fluctuates vigorously near the wall due to wall effect. Compared to axial velocity, the radial velocity distribution is smaller and more complicated. The basic pattern is that on a given cross section of the column radial velocity increases from the wall to the center and it the velocity changes greatly around the center. Under the condition of column height less than 0.8 m, the axial velocity is negative and it directs from the wall to the column axis. When column height is higher than 0.8 m a reverse pattern is obtained, i.e., axial velocity is positive while directing from column axis to the wall. Special efforts were directed to investigate the tangential velocity pattern. Results indicate that the tangential velocity patterns of different cross sections are similar and showed a symmetrical distribution. Tangential velocity distribution concluded two zones: outer whirlpool and inner whirl-pool. And, interestingly, it has been found that on different cross sections the highest tangential velocity always occurs at the same position of the cross sections.

Jan 1, 2014

By Ernesto de la Torre, Karla Velín, Alicia Guevara

"The following study shows the improvement and simulation of a gold recovery plant of 24 t/day of capacity by gravity concentration, flotation and leaching. The ore processed had grades of 6 g/t Au, 15 g/t Ag, and 0.69 %Cu with the mineralogy consisting of 2 %chalcopyrite, 12 %pyrrhotite, 7 %plagioclase and 50 %quartz. The recovery process starts with crushing the ore followed by grinding it further in a ball mill. The ground ore is then concentrated in a Falcon centrifugal concentrator with concentrate being processed by amalgamation process. Gravity tails are sent to a flotation circuit where the copper minerals and some gold are concentrated. Lastly, the flotation tailings undergo cyanidation for gold recovery. Currently, the overall recoveries are 82.8 %Au, 49.6 %Ag and 99.1 % Cu. The optimization was developed in the laboratory using a Wilfley table by gravity concentration. Flotation tests in the laboratory were performed using potassium amyl xanthate and pine oil. Lastly, cyanidation was then performed on the flotation tailings. The results showed the optimum concentration of sodium cyanide in cyanidation is 2 g/L, which produced an increase in gold recovery from 30% to 44%. The reduction of diameter particle from 132 to 80 µm also produces an incremental recovery of gold and silver from 11% to 21% Au and 0.4 to 3% Ag in gravity concentration. Likewise in the cyanidation the recovery of gold and silver has shown a rise from 44 to 62% and 8 to 32% for Au and Ag respectively. However, the flotation method the gold recovery is reduced from 68 to 30% Au by reducing the particle size. Computer simulations using the programs, Moly-Cop and ModSim were performed to determine optimum parameters for the recovery of precious metals at the gold recovery plant."

Jan 1, 2014

By Chao Li, Kym Runge, Saeed Farrokhpay, Dee Bradshaw

"It is well known that froth phase has a controlling influence on the overall flotation performance. Froth recovery is expected to be affected by froth transportation behaviour. The latter has been represented by different volume balance and energy balance based models. In froth transportation models based on a volume balance, the froth phase is divided into different zones. The total froth residence time is the sum of the time spent in each zone and is dependent on the cell geometry, bubble burst rate and the position that bubbles enter into the froth phase. Alternatively, the froth transportation model based on an energy balance treats the froth phase as a block. In this model, froth height above the concentrate lip is being predicted by minimising the energy of the system which is dependent on the froth geometry, froth stability and froth rheology. The froth height can be used to calculate the froth efficiency of delivering mineralized bubbles from the pulp to the concentrate lip. This paper critically analyses the current models of froth transportation in flotation, and examines the limitations of these models. The importance of froth rheology, which is the resistance to the froth flow towards the discharging weir, in determining froth transportation, is also highlighted."

Jan 1, 2014

By M. E. Taranenko, V. A. Krivonosov, S. A. Nemykin

"In concentrating production energy-consuming power installations are wide used, the most powerful of them are the wet autogenous grinding mill operating in closed circuit with a spiral classifier. The analysis of the current state of the automation of the grinding process shows that the reserves for maximizing productivity and minimizing electricity consumption have not yet been exhausted on the existing process equipment. Usage of the achievements of the modern management theory reveals an opportunity for further optimizing of the grinding process. The purpose of the research is to develop an automated control system of complex ""the mill-classifier"" to conduct the grinding process in the most operating efficiency, ensuring the maximization of productivity and minimization of specific electricity consumption. The main idea of this work is to study the specific features of the ore grinding process and creation on this basis of automated control system complex ""mill-classifier"" which allows to find and to maintain the optimal mode of grinding based on identification of the current object parameters, observance and regulating of the object state coordinates. Research methods. We used the methods of system analysis, mathematical statistics, modern automated control theory, theory of systems identification, optimal control, modelling of dynamic processes. Developed scientific provisions: - identification algorithm of the loading sub-system management object of complex ""mill - classifier"" allowing to obtain the unbiased estimators of its parameters according to the data of normal object exploitation; - observing device, which differs from the classic version of the observer Luenberger with possibility of estimating not only the state coordinates of the control object, but also the low-frequency perturbation component; - automated system stabilizing the active power of the grinding mode on the basis of a states controller with Luenberger observer; - structure of the software and hardware that implements the developed models, algorithms, methods of control, management and optimization in the framework of the automation of grinding."

Jan 1, 2018

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:-, Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive forces (electrostatic, van der Waals). -, Nucleation inside the film.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. In the case of hydrophobic surfaces the nucleation mechanism is preferred; in the case of opposite charged silica surface the capillary waves mechanism due to an attractive electrostatic double layer force between silica and air bubble takes place.Hereby the existence of a long range hydrophobic force. on a hydrophobic surface can be excluded. The apparent interaction can be explained by the presence of gas nuclei formed on heterogeneous surface sites. The results provide deeper insight into the mechanisms of wetting film stability, adhesion process in flotation and droplet coalescence."

Jan 1, 2003

By Tsvetan Damyanov, Nikolay Hristov, Evgeni Kostadinov, Lubomir Kuzev

"The process of grinding in drum mills is directly dependent on the dynamic forces occuring in the free movement of the grinding bodies in the volume. The subject of discussion are the potential impacts between grinding bodies having different shape and equal weight in a drum mill that has a diameter of 1200 mm. The study utilised ball grinding bodies having a diameter of 120 mm and tetraballpebs having a conditional diameter of 120 mm. The study was carried out using the Solid Works Simulation software. The following cases were examined: • Impact between two identical grinding bodies; • Impact between a grinding body and the shell surface. The study provided numerical values for impact force, kinetic energy of impact, linear speed of impact, linear displacment of the center of gravity and duration of impact deformation. The impact force of the balls is approximately 179000 N. The impact force of the tetraballpebs with typical vertices, edges and spherical surfaces depending on the area of impact is 177000 to 185000 N. Upon impact between two spherical surfaces of tetraballpebs, the contact area is 263.55 mm2, which is more than twice the contact area upon impact between two balls, which is 114.39 mm2. This determines better conditions for the transmission of kinetic energy by reducing opportunities for overgrinding."

Jan 1, 2014

By Joseph Kelly, Christopher Kelsey

This revolutionary super-fine crusher has the unique capacity to generate fine and ultra-fine products from single stage reductions of coarse or fine mineral feeds. The crusher consists of a rotating compression chamber and an internal gyrating mandrel. The axis of rotation of the shell is displaced relative to the axis of the vertically mounted mandrel. The inner surface of the compression chamber is machined as double cone frustums at an angle equal to the displacement angle. Crusher feed is accelerated into a compacted particle bed, which lines the inside of the compression chamber. The depth of the compacted bed progressively increases until the mandrel is engaged. The mandrel is then free to rotate with the compression chamber. Continued feeding increases power draw and triggers the counter rotating mandrel gyration drive. The gyrating mandrel delivers multiple compressions at high pressure to the rotating particle bed. High concentrations of energy are harnessed within a small active volume over short retention times. The combination of extraordinarily high power intensity and extreme compressive force results in primary compressive fracture and induced secondary tensile failure. The axially displaced rotation of the compression chamber effectively distributes the breakage forces throughout the particle bed. This paper covers open circuit, pilot trials on magnetite, perlite, garnet, marble and a copper/pyrite concentrate. Particular emphasis is placed on the extraordinary results achieved with trials on zircon and highly refractory fly ash. The extreme duties were deliberately chosen to demonstrate the crusher’s application scope and potential to impact capital operating and maintenance costs as the technology matures. Super-fine crushing, once considered impracticable has the potential to offer compelling options for the generation of ultra-fine products.

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 Michel Brissette, Shaheer Sanuri, Veroljub Mihajlovic

"The main purpose of geometallurgy is to improve the mine planning by mapping hardness and throughput into the mine block model using geostatistics to eliminate the large production fluctuations caused by the ore hardness variability coming from different parts of the pit. However, not all grinding testwork available commercially can be applied to geometallurgy because of large amount of sample required and the associated cost per test. Geometallurgy is now being used in designing grinding mill but as the mining project progress, the accuracy of engineering must improve from 30-35% during the scoping study to 10-15% at the bankable feasibility stage and less than 5% for Engineering Procurement and Construction Management. For SAG milling, the SAG Variability Test (SVT) is an abbreviated version of the standard SAGDesign test developed for this geometallurgical need. The same amount of ore than the original test is ground for three cycles into an open batch SAG test and then the SAG pinion energy is predicted to the standard end point of 80% passing 1.7 mm. For ball milling, a Bond Variability Test (BVT) was also developed using the SAG ground ore from the SVT. The Bond ball mill grindability (Gpb), corresponding to the average of the net grams per revolution from the last three cycles of the Bond test, is also predicted from the third cycle. The relative error for both the predicted SAG ore hardness (WSVT) and Bond Work Index on SAG Variability ground ore (Sv-BVI), in kWh/t, averaged 5.5% and 3.8% respectively compared to the SAGDesign testwork values and are within 7% and 10% respectively from plant benchmark and within 7% from the samples sent to all partner laboratories. Both tests can be continued to measure the true hardness necessary for mill sizing. This article discusses the development of these two new tests, SVT and BVT, their potential use and accuracies in any geometallurgical program."

Jan 1, 2014

By P. Huang

Chitosan was tested as a depressant in the differential flotation separation of chalcopyrite and galena. The micro-flotation results showed that chitosan selectively depressed chalcopyrite while galena was floated by potassium ethyl xanthate in acidic solutions. With the addition of 0.67 mg/L chitosan (CT) in the slurry of chalcopyrite-galena mixtures at pH 4, the recovery of galena was 95% while that of chalcopyrite was 30%, indicating that chitosan could potentially be used in differential Cu-Pb sulfide separation. Furthermore, the study of chitosan with either low (LCT) or high molecular weight (HCT) in the differential flotation indicated that better separation was achieved by the chitosan with lower molecular weight (LCT). ToF-SIMS was employed to study the distribution of CT on the surface of chalcopyrite-galena mixtures by ion mass spectra analysis and surface imaging, which showed that CT adsorbed heavily on chalcopyrite but barely adsorbed on galena. The positive ion ToF-SIMS spectra provided information on the surface composition of chalcopyrite-galena mixtures after CT treatment. It appears that the selective adsorption of CT on chalcopyrite was originated from the strong interaction between NH3+ and Cu. Keywords: differential flotation, micro-flotation

Sep 1, 2012

By Ramon V. V de Araújo, Roberto B. E Trindade, Pablo R. Fica-Piras

"Lead has been reported to affect blood vessels and kidneys. It also produces adverse effects in the mental and physical development of children and nervous system of adults. It is also considered as a possible cause of cancer. Because of all these threats to the human life, the reduction of its environmental occurrence, by means of recycling, is an important additional advantage to the usual ones derived of the procedures of the secondary metallurgy: lead can be recycled several times maintaining its characteristics equivalent to the primary one.Furthermore, this way of producing the metal avoids the environmental impacts of primary lead melting. Also, as an additional advantage, it triggers the metallurgical process with a raw material in what we observe higher lead content than in the natural ores. Some of the potential sources for these purposes are: ashes, slags, electrode residues, anodic muds, spent electrolytes, solid and liquid wastes, industrial or automotive catalysts, worn-out or obsolete equipment components and/or final consumption products.About 40% of world’s lead production comes from automotive batteries, mainly composed of four parts: plastic box, electrolyte (diluted sulphuric acid), contacts and connectors of Pd-Sb and plates (PbSO4, PbO2 and PbO). The plates represent 75% of the total mass. Metallic parts can be melted at moderate temperatures and then refined. The remaining fraction, constituted by the non-metallic portions, can be recovered by hydro and electro-metallurgical routes. These routes are preferred instead of pyrometallurgical ones due to the ultimate emissions of lead particulates and sulphur dioxide.The principal constituent of the residual paste of batteries is the lead sulphate. In this process, the paste is treated in two stages: in the first, lixiviating with Na2CO3 (desulphurization of the paste), obtaining PbCO3 and Na2SO4; in the second, the lead carbonate is lixiviated with HNO3, producing Pb(NO3)2, soluble, that can be converted to metallic lead by electrolysis. The reaction of PbSO4 with Na2CO3 in aqueous solutions is fast: the global rate is limited by the diffusion of the carbonate ions inside the reaction medium."

Jan 1, 2003