Search Documents

By Charlene Gokhale

Geopolymerisation has emerged during the last few years as an industrial and ecological approach to construction and waste management. By utilizing waste materials and their reactive properties, it is now possible to create geopolymers systems that not only mechanically durable enough to be used as construction materials but are also potential stable immobilisation systems for toxic waste. Previous studies by Van Jaarsveld et al. (1997) and Van Jaarsveld et al. (1998) have reported on the numerous applications of geopolymers in the immobilisation of toxic metals. Research into the possible utilisation of geopolymers as an encapsulation media for organic waste has however been rare. This paper therefore provides an insight into the possible utilisation of geopolymers as a binder for hazardous organic materials.

Jan 1, 2003

By Çisem Tuba, Ismail Girgin

"Comparative atmospheric H2SO4 and H2SO4 + H2O2 leaching experiments were performed using a Turkish lateritic nickel ore containing 1.52% Ni. In the leaching tests; acid concentration, temperature and leaching time were considered as main variables and the dissolution behaviour of the ore were studied by Ni, Fe, Co and Mg analyses. The dissolution values in the H2SO4 leaching experiments were observed to increase up to 60% (w/w) acid concentration and a temperature of 95°C. Increase of H2SO4 concentration above 60% at 95°C caused decreases in all the dissolution values and this was attributed to the formation of Fe2(SO4)3 and Fe2(SO4)3•HSO4•H2O type compounds. At the considered optimum H2SO4 leaching conditions ([H2SO4]= 45%, T=95°C, t=45 min); dissolution values reached for Mg, Ni, Fe and Co were determined as 99.12%, 95.58%, 92.63% and 78.37%, respectively. An activation energy of 30.57 kJ/mole was determined for nickel dissolution from the evaluation of the kinetic data obtained for H2SO4 leaching showing that the dissolution was controlled by external diffusion and chemical reactions. Caro’s acid solutions were prepared at H2SO4/H2O2 mole ratio of 3 for varying initial H2SO4 concentrations and leaching tests were performed at 25°C. Co behaved very differently and a dissolution value of 83.94% was obtained even at 5% acid concentration in 60 minutes reaction time. Complete dissolution of Co was obtained after 30 minutes of reaction time at 60% initial H2SO4 concentration and the corresponding dissolution values for Mg, Ni, and Fe were reached to 96.16%, 94.27% and 89.46%, respectively. Although the H2SO4 + H2O2 leaching experiments were conducted at 25°C, it was realized that the temperature of the leaching medium was increased to 122°C after four minutes of reaction time due to probable exothermic reaction(s) at 60% initial acid concentration."

Jan 1, 2014

By Gülay Bulut, Ünzile Yenial

"Water composition has a significant effect on flotation. A better understand the role of water composition in flotation is very important for process quality and performance. Based on source of process water, the concentrations of the dissolved ions, hardness, contaminants and residual composition of reagents can varied in the process water. The various water resources employed during lead and zinc flotation caused activation, depression or selectivity effects on minerals due to the presence of different ions in solution. Metal ions in these water resources were adsorbed on the ore, whilst ions associated with gangue minerals were released into the flotation pulp.This paper includes a research for the effect of different water compositions on lead and zinc sulphide flotation. Experiments were carried out five types of water such as tap water, recycling water, tailing dam water, underground mine water and sea water. The ore sample was obtained from Esan Balikesir-Balya mine. The mineralogical study of ore sample shows that it contains mainly galena, sphalerite, pyrite, hematite, quartz, diopside, epidote, calcite, and chlorite. It is found that recycling water and tailing dam water has a positive effect on recovery of lead and zinc minerals and detrimental effect on content of both minerals. This result may explain with remaining reagents in these waters. Underground mine water and tap water gave nearly the same recoveries of zinc. Sea water affects the recovery lead and zinc negatively."

Jan 1, 2014

By Slobodan B. Vujic

"For the requirements of the mining company “Rudnik-Rudnik”, engaged in undergr-ound exploitation of polymetallic ore and lead, zinc and copper concentrates production, the Department of Computer Application of the Faculty of Mining and Geology, University of Belgrade, designed a computer supported and integrated information-management system. This paper presents a concept of this system covering both monitoring and management of production in ""Rudnik-Rudnik"".The ""Rudnik"" Rudnik, Yugoslavia is a mining company, engaged in underground exploitation of polymetallic ore and production of ore, zinc and copper concentrate as well as other metals such as silver, bismuth and cadmium. This mining company runs stable business activities and undergoes a permanent growth of valuable production volume.The basic characteristics of production-technical system of ""Rudnik"" company are: uniform and up-todate technical-technological solutions: linking of production chain from underground exploitation of ore to flotation, namely final product - concentrate of lead, zinc and copper; complete mechanization of production; relatively low level of computer technics implementation; namely, ununiformed implementation of different application of computer-supported information technologies in production and business activities of the Company.These are the assumptions on the basis of which the management of the Company made a decision, in 1999, to upgrade information-management functions through development and application of modern integrated and computer-supported production-business information-management system (hereinafter: IMS, namely IMS Rudnik). For this purpose the Company requested the Department of Computer Application, Faculty of Mining and Geology, University of Belgrade to make the Project on IMS for their needs."

Jan 1, 2003

By Markus A. Reuter, Albert Scholte, Ewoud V. Verhoef, Gerard P. J. Dijkema

A dynamic, interactive map has been developed of the life cycle of a number of metals, from mining through to minerals processing, metal production, product manufacturing, recovery and waste management. Whilst the existing metal process network and waste management infrastructure provide substantial scope for (product) design, these also limit change due to the complex interdependence of metals, both in production and recovery, and the strong path dependency of industry and infrastructure development. Therefore, models for dynamic simulation were constructed that allow the specification and evaluation of the metal process network and waste management infrastructure ‘products’ over a longer time span. The model has been constructed using a bottom-up approach, to enable assessment of the environmental aspects of metallurgy and to simulate changes in the system structure and technology, i.e. from reactor or individual process step up to integrated material cycles. The model comprises hierarchical mass balances and linear models of individual processes and sub-processes. Thus, at lower system aggregate levels an increasing level of technical detail is represented. Data reconciliation has been used literature data on process feed, products and residue composition to calculate representative and reliable split factors around each (sub-)process. World production figures on process capacity and recovery rates are be used to calculate the relative contribution of processes. The dynamic map is illustrated with a case on the introduction of lead-free solder.

Jan 1, 2003

By Marco Le Roux, Martha Van Rensburg, Quentin Campbell

Fluidised bed drying is currently receiving much attention as a dewatering option during the beneficiation of fine (defined here as between 1 mm and 2 mm particles) coal. Apart from concerns about safety and combustion, the operating costs can be high if very high gas or air temperatures are used. The aim of this study was to investigate the removal of moisture from fine coal by using air at a lower temperature (25 - 55°C) within a controlled environment by lowering of the relative humidity of the air. It was firstly proven that fluidization has a major advantage over non-fluidized beds, with regards to drying rate and final moisture content. Hereafter several parameters that influence the dewatering rate and final moisture content were tested, from which it was concluded that the relative humidity of air acts as the largest driving force for dewatering. Parameters tested included relative humidity, temperature and coal composition. Energy balances showed a positive nett energy increase in the dried coal during combustion when related to the energy input during drying. In comparison with thermal drying technologies, fluidized bed drying was proven to be less energy intensive. It was therefore shown that this is a viable technology for the dewatering of fine coal.

Jan 1, 2014

By V. G. Minenko, V. A. Chanturiya, A. L. Samusev

Eudialyte is one of perspective resources of zirconium and other rare earth elements (REEs). Large reserves of eudialyte concentrated in the Murmansk region of the Russian Federation. Usually, technologies of REE treatment include the decomposition of eudialyte concentrate in different acidic, extraction and utilization of all components. The main problems in the leaching of eudialyte include are: the formation of an unfiltered silicon-containing gel; low recovery of REE; difficulty extraction of metals from the productive solution; high aggressiveness of the reagents. One of the promising trends of intensification of the processing of hard-to-degrease rare metal raw materials is the use of energy methods for affecting mineral suspensions. These methods make it possible to increase the efficiency of break up fine-dispersed mineral complexes and extracting micro- and nanoparticles of a valuable component in subsequent deep processing. The purpose of this work is to investigate the effect of energy impacts on the nitric acid leaching of eudialyte concentrate. Experimental studies were carried out in a developed laboratory facility that makes it possible to evaluate the effect of electrochemical, ultrasonic and combined effects on the leaching of zirconium and REE from eudialyte concentrate. The studies carried out on the samples of eudialyte concentrate with the size class of -0.315 + 0.063 mm showed that the use of electrochemical and acoustic effects increases the extraction of ZrO2 in the production solution in 1.6 - 2.5 times, REE in 1.3 - 2.2 times, respectively. An analysis of the microstructure and phase composition of the surface of the eudialyte concentrate showed that the intensification of the leaching process is due to surface cleaning from the silicon-containing gel, as well as the opening of capillary channels and microcracks, which accelerates mass-transfer processes. The results obtained open wide opportunities for creation of modern and effective technology of processing of eudialyte concentrate, producing high-quality zirconium products and REE.

Jan 1, 2018

By L. Muhr, Y. -T. Tang, M. -O. Simonnot, B. Laubie, R. -L. Qui, Z. Chour

"Agromining aims at recovering metals from different secondary resources with hyperaccumulating plants. These natural plants can selectively concentrate metals at very high level and can be transformed to produce commercial compounds. The classical strategy to recover metals from hyperaccumulator plants is based on hydrometallurgy. It consists of: i) burning the plant to obtain ash, which is a very rich bio-ore without organic matter, ii) transferring the target element(s) into aqueous solution by acid leaching and iii) purifying the leach liquor to obtain the target element(s) in the desired form. This method has enabled us to obtain nickel salts, nickel oxide, zinc and cadmium from different plants. However, it is not possible to apply this approach to recover rare earth elements (REEs) from the fern D. dichotoma, growing on mine tailings in South China. Actually, this plant is very rich in silicon: plant burning gives an amorphous ash, very stable despite severe leaching conditions. Therefore, the strategy has been changed and processes are currently developed to extract REEs by direct leaching of the biomass, without burning the plant. Several conditions (i.e. leaching solutions) have been investigated, showing that a good extraction yield was obtained with HNO3 0.5 N (around 84%). This yield was increased to 99% by adding a complexing resin into the leaching solution. After two-steps of elution, results have shown that is possible to recover 75% of the REEs at 81% purity.INTRODUCTION The demand of rare earth elements (REEs) (including 15 lanthanides, yttrium and scandium) has been growing sharply over the past years, because of their industrial applications. REEs are essential elements for emerging technologies, and are used for example in permanent magnets, lamp phosphors or rechargeable batteries. China is the main producer, and the market supply became tense in 2010 when this country decided to limit exports of these elements. Exploitable mineral resources, as well as REE separation capacity are concentrated in a few countries (e.g. USA, Australia, Malaysia, France), which increases the supply risk. Therefore, these elements are considered as critical raw materials (CRM) for many countries and especially for EU (Fortier and Gambogi, 2017)."

Jan 1, 2018

By Ronald Díaz

"Cerro Corona is a porphyry ore with different geometallurgical units and alterations produced by an extensive family of geological failures that have determined a special type of mineralization. With the increasing depth of the mine, it is estimated that the host rock will be less altered. Consequently, the ore will have a higher resistance to breakage accompanied by associated problems such as lower throughput. In light of this reality, various projects have been carried out with the objective to optimize mineral processing of ore with low clay content and high hardness, including reducing the blasting grid, increasing the load factor, using adequate mixtures of hard ore, reducing crusher settings, installing air guns in the transfer chutes, increasing ball charge, and changes in the lifter design, wear control in the hydrocyclones, syntonization of control logics, supervisor control of the SAG mil, characterization of feed ore, etc. However the most important factor was the teamwork between mine and plant personnel, aiming at common objectives for the company. These projects started in 2011, including characterization of mineralogical domains, breakage and blasting characteristics, and also a revision of the actual operating conditions in the crushing and grinding circuit. The development of different designs of the SAG mill lifters and the unloading grates, a 16% ball charge increase, improvements in the blasting process, reduction of the primary crusher setting, weight reduction on the feed lid, and variation of operational parameters, all allowed the company to achieve its objectives of maintaining impact control and steel recharge within the expected operational parameters. The achieved throughput is above design capacity, sustainable, and not without new challenges for maintaining and optimizing this production level."

Jan 1, 2014

By J. Kwon, D. Lee, H. Cho

"The use of the combined grinding and liberation model to predict liberation characteristics of iron ore comminuted by a ball mill was studied. Comminution characteristics were obtained using the one-size fraction method. The iron ore samples were crushed and separated into a number of narrow size fractions by screening. The size fractions were further divided by magnetic separation into three classes: concentrate, middling, and tailings. Subsequently, various size-grade classes were subjected to ball milling, and the results were analyzed in terms of the kinetic grinding model. The mineralogical textures of the grinding products were analyzed using mineral liberation analysis. The distribution of iron content within the size fractions was characterized by the beta distribution combined with the Andrew–Mica diagram. It was found that the grinding characteristics of the iron ore samples varied slightly with the iron content. However, the liberation characteristics were well described by the same set of liberation model parameters, regardless of composition. The variation in grinding kinetics with composition and the liberation model parameters was used in the combined comminution–liberation model to predict the evolution of the size-composition matrix as grinding proceeded. The predicted results agreed well with the experimental results. The developed model can be used to construct the yield–recovery graph and to calculate the liberation efficiency to determine the size reduction threshold for efficient separation. INTRODUCTION In mineral processing, comminution is usually the first step that ores undergo to liberate valuable minerals from gangue minerals. Generally, as the particle size decreases, higher liberation can be achieved. However, excessively small particles are unfavorable to subsequent processes, such as separation. Moreover, comminution is a highly energy-consuming process itself that accounts for approximately 60% of all energy used for processing. Therefore, there is a definite need to increase energy efficiency by applying adequate stress so that a high degree of liberation can be acquired at the coarsest size without overgrinding. To this end, it is essential to develop a model to predict the liberation of minerals as a function of size reduction."

Jan 1, 2018

By Lutz Rolf, Halit Z. Kuyumcu, Salas Cazón. Milton A.

Aim of experimental investigations was the mathematical description of the abrasion process running with a single particle stress. This is on the one hand the basis for the physical interpretation of the process, on the other hand the base for the simulation of abrasion processes carried out in technical scale. With this investigation for the first time the influence of the particle shape changing with increasing abrasion progress was quantitatively described. This influence affects itself particularly strongly on break-fresh particles up to an abrasion degree of approximately 10 to 20%. This is for the description of technical processes the most interesting area.

Jan 1, 2003

By Xin Tan, Changgen Li

"The floatabiliby of chelate CF-collector for zinc and lead oxide minerals was described. It found that CF-collector possesses a strong collection power for zinc and lead oxide minerals as well as excellent selectivity for the gangue minerals. A new technology of zinc and lead oxide flotation with CF reagent as a collector, lead nitrite as a activator and water glass as modifier was presented. The mechanism of interaction between reagents and minerals was discussed by means of adsorption, zeta potential, nephelometric titration, XPS and infrared spectra was investigated.CF-collector, newly developed by Beijing General Research Institute of Mining and Metallurgy (BGRIMM), is a kind of chelate collector for the flotation of oxide minerals. CF-collector mainly consists of N-nitroso-N-phenylhydroxylamine ammonium salt. The CF-collector was used for the selective flotation of scheelite in the Chinese plants.In this paper, the effects of the dosages of activator Pb(NO3)2 and depressants (sodium hexametaphosphate, polyphosphate, water glass and salified water glass) on the floatabilities of several minerals (cerussite, smithsonite, calcite, dolomite, limonite and quartz) as well as their mixtures were investigated in the presence of the CF-collector. The results show that the CF-collector is the excellent collector for selective flotation of cerussite and smithsonite. Pb(NO3)2 can selectively activate the oxides of lead and zinc resulting in a decrease of the CF-collector dosage. The sodium hexametaphosphate plus the salified water glass are the effective depressants for gangue minerals. Based on the above facts, the “CF process”, namely, used CF reagent as a collector, Pb (NO3) 2 as a activator, and sodium hexametaphosphate plus salified water glass as depressant, has been used for the flotation separation of the lead oxide mixtures or zinc oxide mixtures without disliking and heating. For the feed lead assaying 19.07%, the lead concentrate assaying 49.81% Pb at the recovery 80.69% was obtained after one step flotation. For the feed zinc assaying 12.85%, a zinc concentrate of assaying 29.56% Zn at recovery 83.87% was obtained."

Jan 1, 2003

By B. McFadzean, J. Taguta

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a valuable and reliable means of determining solid surface properties such as wettability, it has seldom been applied in mineral processing research. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. The enthalpies of immersion were then related to the first-order flotation rate constant as determined by the microflotation technique. The same measurements were also made on sulphide minerals whose surfaces were modified to different degrees of hydrophobicity using different percentage coverages of amyl xanthate collector. The enthalpy of immersion technique was capable of distinguishing and ranking minerals according to their wettability. All mineral types and collector-treated minerals conformed to the same relationship that was found between the enthalpy of immersion and the flotation rate constant. This conformed, empirically, to a power law equation. As the enthalpy of immersion decreased, there were large increases in flotation response for very small changes in hydrophobicity. In addition, a critical enthalpy of immersion (CEI) was found, above which no flotation could occur. The scatter in the data points could be corrected for by adjusting the rate constant using the density of the minerals to produce a robust relationship between the rate constant and enthalpy of immersion. These results have shown that the enthalpy of immersion is able to indicate both the natural mineral hydrophobicity and the extent to which collectors can render a mineral hydrophobic. This technique has considerable potential to be used as a sensitive and accurate measure of mineral surface wettability in order to predict flotation performance.

Jan 1, 2018

By W. S. Eu

Reduction of weathered mineral ores can initiate phase transformation which can affect either their activation or deactivation, subsequently influencing the extent of extraction of desired metals in a leaching reagent. The reduction of ilmenite ores for one occurs as a series of parallel, solid state reactions which at present has no known mechanisms, although the evidence of their effects is abundant. Understanding these reactions may well be the key to uncovering the mechanism of ilmenite activation, hence enabling precise control of its reaction process to maximize yield of TiO2 extraction. However, documenting the solid state reactions in the reduction of ilmenite is challenging due to the ore complexity, the number of simultaneous reactions and the difficulty of capturing critical intermediate reactions and phase transformations during processing. The phase transformations of ilmenite minerals reduced at temperatures up to 850°C were investigated in this study. Mineral transformations were studied in-situ using synchrotron radiation based X-ray powder diffraction with temperature resolved tests. The effect of the extent of reduction and specific mineral transformations were verified by leaching reduced ore with sulphuric acid. The re-sults suggest that transformation of major mineral phases occurs within of specific window of operation and thermal treatment appears to influence the extent of activation and leachability of ilmenite minerals.

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 Aysan Molaei, Kristian Waters

Solvent extraction is the one of the most common techniques for recovering metal ions from aqueous systems. However, solvent extraction is generally limited to relatively high concentrations and requires a high organic/aqueous ratio. Predispersed solvent extraction (PDSE) is a modified solvent extraction technique in which organic phase pre-comminute into colloidal liquid aphrons (CLAs). In this study, the extraction of copper by the PDSE technique was investigated. The main focus of this study was on the characterization and application of CLAs under different operational conditions, and to investigate the effects of different parameters on the extraction of copper from dilute streams. The effect of phase volume ratio (PVR), initial extractant concentration and initial copper concentration was studied and optimum conditions for copper removal using CLAs generated by LIX 984N as extractant, oil soluble and water soluble surfactants were proposed. Experimental observations indicated that PVR and initial LIX 984N concentrations had a significant effect on copper extraction.

Jan 1, 2014

By Di Liu, Yongjun Peng

"It was identified that clay minerals adversely affect fine coal flotation through slime coatings. In the study, it was interesting to find that an anionic polymer dispersant, lignosulfonate, successfully mitigated the negative effect of clay minerals in coal flotation using fresh water, but in saline water, it exacerbated coal flotation.In order to understand the mechanisms underpinning the different behaviour of lignosulfonate in coal flotation using fresh and saline water, the adsorption isotherm, and dynamic light scattering (DLS) measurements were conducted in this study. While DLS monitored the molecular conformation change (swelling or shrinking) of the polymer in fresh and saline water, adsorption isotherms enabled polymer adsorbed amount on clay and coal mineral surfaces to be determined. It was found that lignosulfonate adsorbed on the coal and clay mineral surfaces providing effective electrostatic repulsions and resulting in a mitigation of clay minerals from coal surfaces in deionised water. In the presence of saline water, however, polymer molecular conformation changed. Polymer molecules were compressed and adsorbed in form of aggregates. The adsorption amount of lignosulfonate on clay minerals increased in saline water. A low dosage of lignosulfonate could not provide sufficient electrosteric repulsion to disperse clay minerals. Moreover, the high adsorption amount of the polymer on coal and clay surfaces led to a more hydrophilic coal surface, and coal flotation was therefore depressed in saline water. This study provides a new insight into understanding the role of anionic polymeric dispersants in mineral flotation using different quality water."

Jan 1, 2014

By Paulo Castillo, Cesar Gomez, Jaime Alvarez

Operations using flotation to produce mineral concentrates require testing of frothers to characterize their ability to preserve bubble formation size and to build a stable froth. Many techniques have been proposed to measure parameters associated with these two roles. These techniques focus, in general, on only one of these roles and are based on special equipment operated at conditions quite different from those existing in industrial cells and columns. Both roles have been simultaneously characterized in a laboratory flotation column, but the requirements associated with the installation and operation of one of these units, are a serious limitation for its use on-site. A technique based on the use of a laboratory mechanical cell, a common piece of equipment in operations, will have wider application. Establishing the ability of a frother to control coalescence by preserving bubble formation size is done through bubble size measurements as a function of frother concentration. Froth build-up and stabilization is associated with the amount of water carried by bubbles into the froth layer, which has been demonstrated to correlate with the gas holdup in the collection zone. Procedures devised for determining the critical coalescence concentration (CCC) from measurements of bubble size as a function of frother concentration, and the gas holdup by collection of water displaced from the cell by the presence of bubbles at different frother concentrations, were tested. Three analytical-grade frothers were utilized: a straight-chain (1-heptanol) and a branched (MIBC) alcohol and a polyglycol (PPG425). The results obtained at a standard set of conditions, demonstrated consistent differences between these frothers, and the ranking from least to most effective for reducing bubble size or decreasing water drainage followed the same sequences found when more complex frother characterization techniques are used.

Jan 1, 2014

By Ljubisa Obradovic, Baisui Han, Batnasan Altansukh, Zoran Stevanovic, Atsushi Shibayama, Jonovic Radojka, Daizo Ishiyama, Kazutoshi Hag, Radmila Markovic, Ljiljana Avramovic

This paper discussed a combined froth flotation and high pressure leaching (HPL) process to recover copper from mine tailings. At first, froth flotation were carried out using the mine tailings sample under various conditions in the presence of different pH (3.5-10) and sulfurizing reagent value (0-1000 g/t), respectively. As a result, optimum condition (sulfurizing reagent of 1000 g/t, pH of 10, PAX (collector) of 100 g/t and MIBC (frother) of 200 g/t) was found for froth flotation of copper. The effects of sulphuric acid concentration, leaching temperature, total pressure (steam pressure plus oxygen pressure) on high pressure leaching (HPL) of mine tailing were investigated using sulphuric acid solution in the presence of oxygen. The best conditions for HPL were obtained to be sulphuric acid concentration: 0 mol/L (water), leaching temperature: 170 ?, total pressure: 2 MPa, leaching time: 1 hr and pulp density: 100 g/L. The leaching rate of copper reached nearly 99 % and the concentration of copper in pregnant leach solution (PLS) was 0.24 g/L. Finally, copper in the mine tailing was recovered using froth flotation followed by HPL. As a result of a combined froth flotation and HPL, the vast majority of copper (99 %) from the mine tailings was extracted.

Jan 1, 2014

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