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By G. Venkateswara Rao

The jigging of ferrous ore to produce higher-grade products has been practiced for many decades. This is due to easy separation, a beneficial trade- off between operating cost and reduced yield relative to Dense Media Separation (DMS). Jigging becomes prominent for beneficiation of iron ores in the coarser size range. At present drive is towards the use of under bed air pulsed jigs for the beneficiation of ferrous ores. The main advantage is that the under bed air pulsed jigs are capable of generating the large pulse of amplitudes required to fluidize a deep bed of heavy ores particularly lump iron ore up to 40mm size. The major jig parameters effecting the jigging operation are bed height, shape of the pulse, residence time, operating pressure, valve cycle time and water flow rate. With the pulse shape set correctly for optimum stratification rate, even it is still necessary to provide enough residence time, to ensure the difficult material will take time to migrate to the expected layer in the bed. In order to find the Jig Stratification Index (JIS) parameters like bed height, operating pressure, water flow rate, cycle valve time and shape of the pulse were optimized first by conducting various tests. Typical Iron ore samples from Odisha (both lump and fines) were subjected to stratification studies at residence time of 1, 5 and 15 minutes. Jig Stratification Index (JSI) for both lump (0.30) and fines (0.20) were determined by using APIC Jig. The maximum possible JSI was calculated by using heavy liquid separation test (0.42 for lump and 0.24 for fines). It is found that the jig bed JSI is less than the Heavy liquid JSI for both lump and fines. The ratio of Jig bed JSI to the heavy liquid JSI is 0.83 for lump and 0.71 for fines. The JSI and ratio of Jig bed JSI to Heavy liquid JSI are low for fines due to fluid turbulences causing some degree of remixing in the jig bed. The fluid turbulences are more for fines than lump, hence jigging of fines is difficult and challenging. Keywords: sub grade iron ore, gravity separation, jigging, apic jig, stratification, residence time, jig stratification index

Sep 1, 2012

By Diego Mesa, Willy Kracht

Frothers may be classified as weak or strong depending on their ability to produce stable froths, which is related to the amount of water that they transfer from the pulp to the froth. They can also have an effect on the non-selective mechanism of recovery by entrainment, implying that both selectivity and froth stability are, at least to some extent, frother dependent. Solids, on the other hand, also have an effect on froth behaviour. Clays, which are characterized by their small particle size, laminar shape, and high specific surface, tend to report to the froth phase and have an enormous impact on both froth stability and the overall performance of the flotation process. The purpose of this work is to shed light on the effect that different frothers have on the froth behaviour when clays are present. In order to do that, two sets of experiments were conducted using frothers from the families of alcohols and polyglycols. For each test, the equilibrium froth height was measured at different frother concentrations in an agitated machine with an acrylic square-base cell that was 11 cm wide and 25 cm high. The cell was designed in such a way that froth was able to grow without concentrate discharge. In the first set of tests, pure clays such as kaolinite and montmorillonite were used. In the second set, an actual copper sulphide ore with a high content of clays was used as solid phase. The results, expressed as curves of equilibrium froth height against frother dosage, showed a coupled effect of frother-clay on froth behaviour for both sets of experiments. In some cases, the froth grew up until the border of the cell with only a few parts per million of frother. In other cases, the equilibrium froth height varied smoothly with frother dosage. The results suggest that choosing the right frother can be of use for controlling the froth behaviour when dealing with clay-rich froths, using frother dosage as the control variable. The application of these findings at industrial scale are discussed and some recommendations are given.

Jan 1, 2018

By Rolf Lauten, Yongjun Peng, Yufan Mu

"Biopolymers, produced from cellulosic biomass, have promising prospects of application as depressants in mineral processing. In this study, three different types of biopolymers (i.e., DP-1775, DP-1777 and DP-1778) were used to study the effect of polymer structure on flotation of un-activated pyrite, copper activated pyrite and chalcopyrite. It was found that the depressing effect of DP-1775 and DP-1778 was much stronger than that of DP-1777, and pyrite was depressed to a greater content than chalcopyrite with the same biopolymer at the same dosage. The biopolymer concentration played a vital role in determining the degree of depression. For each biopolymer, the higher the concentration, the greater the minerals were depressed. The mechanism underpinning the depressing effect of these biopolymers was explored in this paper. The concentration of biopolymers could determine the properties of the adsorption layer and the confirmation of biopolymer chains on mineral surfaces. The biopolymer molecules may aggregate when polymer concentration was over a critical value. Molecular weight and functional groups of biopolymers were the key factors characterizing the depressing capability of different biopolymers. Differences between the tested biopolymers and features of the adsorbed layer might account for the observed trends in ability to depress pyrite and chalcopyrite flotation. The greater depressing effect of biopolymers on pyrite over chalcopyrite might result from the preferential adsorption of biopolymers on pyrite over chalcopyrite."

Jan 1, 2014

By A. V. Rasskazova

"The oxidized and mixed ores are processed by heap leaching. Primary ores with high gold content are floated. In recent years mining of primary ores with the low gold content (up to 4 ppm) has increased. Extraction of gold from these ores by floatation is technologically ineffective. Gravity concentration is ineffective for fine gold particles because of their floatability. The research objective was assessment of the viability of processing gold-bearing ore with combined gravitational and hydrometallurgical methods and testing of recovery of metals from a gold-copper oxidized ore chloride-hypochlorite leaching solution. The advantage of chloride-hypochlorite lixiviant is the low cost of reagents which is produced by the electrochemical synthesis of NaCl solution with the addition of HCl. The adsorption of chlorine compounds by a mineral matrix and its ability to oxidize the refractory ore components and allows for the application of chloride-hypochlorite systems for gold recovery for both oxidized and primary ores. The complexity and problem in using a gold–chloride system is the strong adsorption of gold–chloride complexes onto mineral surfaces, such as goethite, quartz, and alumina. In preliminary testing, gold recovery from gravity circuit gold bearing concentrates processed by agitation leaching in chloride-hypochlorite solution, gold recovery has reached up 82% after 4 hours of leaching. Chloride-hypochlorite leaching of copper-gold oxidized ore with preliminary processing by sulfuric acid provided for 94 % gold recovery to solution. Understanding of ecological hazard of cyanides is the motive power of researches in the field of search non-cyanic chemistries to provide for technologically and economically effective solvents of gold. Soluble compounds of chlorine with a suitable oxidizer are one of the alternatives to cyanides. Basic researches of gold extraction by chloride-hypochlorite solution have shown high rates of gold recovery.INTRODUCTION Because of the continued and growing environmental concern for the use of cyanide for gold processing, interest for the use of non-cyanide lixiviants, especially with halides has renewed recently (Tran et al., 2001; Ferron et al., 2003; Bhaghalha, 2007). Leaching solutions based on halides (chloride, bromide and iodide) are viable alternative to cyanide (Kwang et al., 2008). The major disadvantage of the chlorine–chloride system is the high reactivity of chlorine in reaction with sulfide and gangue carbonate minerals. It is believed that only high grade materials may be treated by chlorine–chloride systems economically (Baghalha, 2007). Another important problem of the application of gold–chloride complex is that it tends to be rather unstable and may re-precipitate upon contact with a reductant, such as sulfidic minerals of ore. It is well known that Au(III)–chloride hydrolysis species are strongly adsorbed by goethite, quartz, and alumina (Machfsky et al., 1991). To minimize adsorption of gold–chloro complexes, it works best to minimize the adsorption time."

Jan 1, 2018

By R. K. Dwari

The electrostatic beneficiation of coal is based on tribocharging characteristics of ash forming minerals and coal particles. The tribocharging of quartz, pyrite and coal particles contacted with various metals and polymeric materials have been measured and the charge acquisition is assessed through surface energy calculations from liquid contact angle data. The contact angles, before and after tribocharging of solids, are measured using Krüss tensiometer and Washburn?s method where the sample holders in tensiometer are specially constructed with tribocharger materials. The charge polarity and amount of charge acquired by quartz, pyrite and carbon with metal tribochargers were found in good agreement with the reported work functions of the contacting surfaces. The charge results with polymer materials differed from the work function values, presumably caused by surface contamination. The surface energy of quartz calculated by all the theoretical approaches in the literature showed that the tribocharging increases the surface energy. Both polar and non-polar components computed from Fowkes and Owens-Wendt-Rabel-Kaelble approaches dis-play that both these components increased after triboelectrification. However, the polar component divided into acid and base components, as in van Oss approach, manifest decreasing acid part and increasing base part. Since quartz charged negatively during tribocharging with metal surfaces and therefore accepted electrons, the determined acid and base surface energy components are consistent with charge transfer process. The results also elucidate an explicit correlation between the charges generated by powders and the surface acceptor (acid) and donor (base) electronic states and thereby the work functions. A novel fluidized bed tribocharger was designed and developed with internal baffle system for efficient contact electrification of mineral and maceral to produce high differential charging for efficient separation. The results achieved on coal with 45% ash content are presented and discussed.

Jan 1, 2014

By Vladimir Vigdergauz

"Electrochemical studies of metal sulfides in connection with their floatability are discussed. According Frumkin, sorption of electroneutral organic substances has a maximum near the potential of zero charge. This idea initiated attempts of application of electrochemical methods for the controlling of organic collector sorption and mineral flotation. The lecture reviews results of electrochemical studies of the processes taking place during sulfide flotation: redox-state of mineral surfaces and xanthate solutions, xanthate sorption and hydrophobic layer composition, surface wettability and flotation recovery of sulfide minerals. Redox-transitions of minerals, transport of ions and charging of mineral surfaces, electroreduction of dissolved oxygen and accompanying processes of oxidation of minerals and reagents-collectors, - all these matters became the subjects of detailed research. Cyclic voltammetry, rotating disk electrodes, spectro-electrochemical techniques and other modern experimental methods now routinely accompany studies of mineral processing. Relatively new electroanalytical techniques like the voltammetry of mineral particles immobilised on electrodes using polymeric binders have become extremely useful for studying weakly conductive minerals and dispersed flotation products. Full discussion of electrochemical studies of metal sulfides in relation to mineral processing must include bioelectrochemistry and electrocatalysis which open exceptional possibilities for selective leaching of gold and non-ferrous metals. At this time, the paper focuses on the sulfide flotation as a potential-dependent process; the problem of oxygen and its influence on the sulfide flotation; the electrochemical aspects of xanthate oxidation and sorption; theory of suspended electrodes as applied to the mineral slurries and experimental study of the effect of electrochemical pretreatment of flotation pulps."

Jan 1, 2014

By K. C. Corin, M. S. Manono, J. G. Wiese

"It has been suggested that hydroxo species, particularly those of calcium, selectively adsorb onto gangue minerals. Such species enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the positively charged mineral surface and the negatively charged CMC molecule. Thus, the hydrophilicity of gangue minerals is enhanced, preventing the dilution of the concentrate. However, as there is little evidence to support these claims it is important to investigate. Adsorption data and mineral surface charge analyses will allow a fundamental understanding into how electrolytes and their ionic strengths affect gangue-depressant adsorption. It is strongly anticipated that decoupling these effects will allow process operators to tailor their process water quality needs towards best flotation operating regimes and in the long run effect closed water circuits. Thus, using talc and pyrrhotite as proxies, this work investigates the influence of the ionic strength of process water on the adsorption of CMC onto minerals in sulphide flotation.INTRODUCTIONThe phenomenon of gangue depression in mineral flotation is of critical importance as regards the attainment of a required concentrate grade. This thus suggests that the depressant of choice has to have a highly selective affinity for the targeted gangue minerals. This would ensure the necessary prevention of gangue from reporting to the concentrate without inadvertently depressing the value bearing mineral. The chemistry of the environment regulates the manner in which gangue depression occurs. In sulphide flotation, polysaccharides are used as depressants of choice to depress naturally floatable gangue which may in the case of Merensky ores exist as talc. The two widely used polysaccharides in the South African context are carboxymethyl cellulose (CMC) and modified guar gum. It is suggested that polysaccharides depress gangue by rendering the surface of gangue hydrophilic or by preventing the formation of hydrophobic layers on gangue mineral surface, forming large gangue aggregates and thereby increasing their heterocoagulative nature (Shortridge et al., 1999)."

Jan 1, 2018

By M. Holuszko, I. Mikhalev

"Previous studies described by Galvin et al. (2017) have shown that for Australian bituminous coal fines, both in batch and in continuous process, the new improved oil agglomeration procedure based on the use of high-internal-phase (HIP) emulsions, as compared to the conventional “pure oil” agglomeration process, enables a significant reduction in the amount of oil while reaching a high yield of clean coal (approximately 90% of agglomerates greater than 355 µm in size) in a significantly shorter time. The HIP emulsion used in these experiments comprised up to 95% vol. aqueous solution of sodium chloride (3% wt. concentration) and for the rest, a mixture of kerosene (oil) and sorbitan monooleate (SMO emulsifier) in a 1:1 ratio as a binder. This study evaluates the applicability of the new HIP-oil agglomeration process to treat Canadian bituminous ultra-fine coal and Russian sub-bituminous coal fines and compares results from agglomeration to the flotation response of both coals. Oil agglomeration is known to be sensitive to surface properties of coal. Since surface properties of coals depend not only on the rank of coal but also on their origin (depositional environment) and mineralogical composition, both the applicability of this new improved agglomeration process to the non-Australian coals and its efficiency became the motivation for this study. To evaluate the applicability of the new process to both Canadian bituminous and Russian sub-bituminous coals, a series of bench-scale tests were carried out under conditions similar to those described by van Netten et al. (2016) for the Australian coals. Based on the results obtained in this research, new boundary conditions for the application of the HIP emulsion-based oil agglomeration process have been outlined and conclusions on the viability of the new process to treat ultra-fine coal from Western Canada and Russian sub-bituminous coal fines have been reached.INTRODUCTION In most cases, to meet the market requirements, the mined coal has to be processed to reduce the ash content by the removal of mineral matter and thus to increase the quality of the coal products (van Netten et al., 2016). Generally, flotation is used for processing fines from high rank coals; however, there are high losses of very fine coal due to the inefficiency of this process. Furthermore, difficulty in dewatering the fine coal results in excessive moisture levels causing coal handleability issues, which increases costs in the coal-cleaning industry (Capes & Darcovich, 1984). Much of the development that has occurred in fine coal cleaning has taken place with higher-value coal, often metallurgical (Klima et al., 2012). If the fine coal is deemed to be too difficult or expensive to process, it may be discarded as waste (van Netten et al, 2014). Such disposal not only creates an environmental liability but may also result in the loss of a valuable, high quality product that is better liberated than the coarser fractions of coal."

Jan 1, 2018

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By Francisca San Martín, Martin Rudolph, Willy Kracht, Tomás Vargas

It has been shown that bacteria Acidithiobacillus ferrooxidans can be used to depress pyrite in seawater flotation at natural pH, which opens the possibility for its use as an alternative to lime to depress pyrite in copper sulfide flotation. In order to have a better understanding of the mechanisms involved in pyrite depression with A. ferrooxidans, an exploratory experimental campaign was carried out, including attachment density and contact angle measurements, and the effect of adding bacteria before or after collector. Biodepression of pyrite improves when increasing pH from 3 to 8, with a decrease in recovery from 92% to 36%. This increase in depressing capability is accompanied by an increase in attachment density, from 2.58×108 bacteria/g to 1.99×109 bacteria/g at pH 3 and 8, respectively, suggesting that the mechanism of depression is related to the attachment of bacteria to the pyrite surface. It was observed that the conditioning sequence with collector and bacteria influences the biodepression capacity of A. ferrooxidans. Having as a reference a value of pyrite recovery equal to 97%, when using only xanthate in seawater flotation at pH 8, the effect of both conditioning with bacteria-followed-by-xanthate and xanthate-followed-by-bacteria were assessed. When bacteria were added before the collector, the recovery of pyrite decreased to 36%. On the other hand, when bacteria were added after collector, the recovery was 64%, showing that biodepression of pyrite with Acidithiobacillus ferrooxidans is more efficient when the conditioning is carried out first with bacteria. The contact angle values show that there is little effect of the second component added to the system, i.e., if pyrite is first conditioned with bacteria, the contact angle does not change significantly once the xanthate is added (bacteria-followed-by-xanthate). The same was observed when the conditioning sequence was xanthate-followed-by-bacteria.

Jan 1, 2018

By Kal Sastry, Anshuman Prasad

This paper presents a population balance model (PBM) for describing the agglomeration process and select a suitable coalescence kernel that can simultaneously describe nucleation, layering and coalescence mechanisms. The PBM is solved numerically by making use of a size discretization procedure in order to simulate iron ore agglomeration in rotating drums where moist feed is added to preformed seeds. Subsequently, a comparison of computer simulation results with the previously published experimental data is provided. Finally, the paper discusses how the current approach can be further extended to the simulation of industrial iron ore agglomeration circuits operated in closed circuit.

Jan 1, 2003

By A. Norori-McCormac

"Air recovery, the fraction of air entering a flotation cell that overflows the cell lip, is linked to flotation performance, and it has been shown through industrial testwork that operating flotation cells at air rates that yield the Peak Air Recovery (PAR) results in high mineral recovery. For operating parameters over which flotation plants have little control, such as particle size, investigating the effect on the position of PAR, and the subsequent effect on flotation performance, proves more challenging. To this end, we have developed a bench scale flotation system that runs continuously and exhibits froth behavior similar to that found industrially, allowing the study of such parameters as particle size in addition to air rate. The bench scale system comprises a 4 l baffled cylindrical flotation cell, stirred by a Rushton impeller. The concentrate is recycled back into the pulp, allowing for continuous operation. Glass beads are used as solid particles, allowing a wide range of particle sizes to be tested, with TTAB as collector and MIBC as frother. The system allows operation at air rates typical of industrial flotation systems (1 -2 cms-1 superficial gas velocity), in addition to yielding a froth that coalesces and bursts and exhibits a peak in air recovery as cell air rate in increased. Solids and water recovery is also measured. The results show that air recovery is sensitive to changes in particle size. The intermediate size distribution showed a peak in air recovery (PAR) that corresponded with the maximum solids flowrate, as found industrially. It is shown that finer particles do result in more stable froths and higher recoveries, particularly at low air rates. The effect of particle size on the position of PAR is not yet unequivocally determined from these results."

Jan 1, 2014

By S. Castro

Molybdenite flotation is strongly depressed at pH higher than 9.5 in the flotation of Cu-Mo ores in sea water. Chemically sea water contains mainly Na+ and Cl- ions, but also some secondary ions, such as SO42-, Mg2+; Ca2+, HCO3-; etc., which are not necessarily indifferent for the flotation of molybdenite. The natural floatability of molybdenite in sea water and in NaCl solutions containing different secondary ions is investigated by micro-flotation tests. The tests indicate that the floatability of molybdenite in alkaline media in 0.6 M NaCl solutions is not affected by the presence of anions, such as, SO42- and HCO3-, at concentrations similar to those occurring in sea water. However, a strong depression of molybdenite at pH ranging from 9.5-10.0, is produced by the alkaline earth metal cations (Ca2+ and Mg2+ ions), dissolved in distilled water or in 0.6M NaCl solutions. It was found that effect of Mg2+ions is significantly stronger than Ca2+ ions. Effect of both ions is attributed to hydrolysis and adsorption of MOH+ hydroxy-complexes. This is followed by subsequent precipitation of hydrophilic colloidal hydroxides at the molybdenite/solution interface, and in bulk solution.

Sep 1, 2012

By Sergio Castro, Janusz Laskowski

In the flotation in highly concentrated electrolyte solutions not only ionic strength but also chemical composition, flotation pH and mineral properties play an important role. As a result an improvement or depression may be observed. A strong improvement in the floatability of hydrophobic bituminous coals and other inherently hydrophobic minerals is characteristic for the "salt flotation process", which is carried out in concentrated electrolyte solutions at natural pH and without addition of any flotation reagents. However, pH is a key factor when saline and hipersaline waters with hydrolyzing metallic ions are used as process water. In the case of flotation of Cu-Mo sulfide ores in seawater, molybdenite is strongly depressed by the Mg2+ hydrolysis products when pH is raised to depress pyrite. Process water with a high content of Mg2+ and Ca2+ ions, and this also includes seawater, have deleterious effect on the anionic flotation of industrial minerals with fatty acids. The flotation of potash ores is carried out in NaCl-KCl saturated brine (6-7 mole/L of NaCl and KCl) with the use of long-chain amines. Such a high electrolyte concentration changes dramatically the amine Krafft point making the collector insoluble in brine; its mode of action entirely differs from that in conventional flotation processes.

Jan 1, 2014

By G. Mucsi

This paper deals with the laboratory investigation of cathode ray tube (CRT) glass based glass foam, a relatively new product so called ?Geofil bubbles?. The main process engineering material properties of raw materials, such as particle size distribution, moisture content, density and specific surface area are shown. Then the preparation of raw cathode ray tube glass waste is presented including the following steps: crushing in impact crusher, grinding in laboratory scale ball mill, mixing, pelleting and sintering. We found that it was possible to produce foam glass (with proper mechanical stability and particle density) from the investigated waste CRT glass. The material characteristics of the final product strongly depend on the sintering conditions. Optimum conditions were determined particle size fraction was found to be 4-6 mm, temperature 800 0C, residence time 7.5 min. Keywords: waste CRT glass, grinding, pelleting, sintering, glass foam

Sep 1, 2012

By G. Pahomova

"It developed an alternative to traditional flotation enrichment refractory of complex lead-zinc ores to obtain conditional lead and zinc products. The scheme involves the use of the processing method of gravitational enrichment of the primary cycle and the combined gravity-flotation-hydrometallurgical in finishing. The method has a high level of comprehensive utilization of mineral raw materials in relation to the elements that are extracted in the process of enrichment in lead concentrate, and the increase in recoverable value of processed ores. INTRODUCTION The primary source of lead are complex sulphide lead-zinc ore, lead ore actually rarer. The value of lead and zinc ores (except lead and zinc) is determined by the presence in them of a wide range of associated components: silver, contained mainly in galena; gold; bismuth in the form of its own minerals, but is associated with galena; cadmium contained mainly in the sphalerite; indium, thallium and gallium contained in sphalerite and galena; selenium and tellurium are present as impurities in the sulfide, tellurium is also found in the form of its own minerals. Of note harmful impurities antimony, which is often associated with lead sulphosalts and arsenic, having a substantially own minerals. By quality (content of lead, or the total content of lead and zinc) lead-zinc ores are divided into rich, ordinary and poor; by oxidation - to sulfide (with a lead oxides content less than 15% and zinc oxide content less than 10%), mixed and oxidized (50% oxide); the latter have a subordinate importance as a source of zinc and lead. Traditionally, the most contrasting technological properties of sulfide ores of nonferrous metals considered flotation properties, which determines the priority in the selection of flotation technology of their enrichment. Other methods of enrichment - gravity (jigging and enrichment in heavy suspensions), radiometric sorting (separation) are used as preliminary operations whose main purpose is to increase the content of lead and zinc in the ore sent to flotation, as well as the removing of part of empty rock in dumping tails prior to flotation. Effective implementation of these methods is possible at large size emphasizing in the ore of lead and zinc minerals, which is typical of the rich ores and which so far mainly worked. At the same time, non-ferrous metal ores (polymetallic, lead-zinc, copper-zinc, etc.) have a sufficiently high contrast to gravitational properties since ore minerals have a higher density compared with a rock minerals. But the gravity of the practice of non-ferrous ores enrichment is not widely used, despite its high degree of environmental safety and lower cost expensive."

Jan 1, 2018

By I. Silin, H. Wotruba, J. Huben, A. Ognyanova

"With increasing shortage of raw materials, the beneficiation of ultra-fine ores will play a larger role in the near future. Many established process technologies do not yield satisfactory separation results for ultra-fine materials. Without selectivity, high-grade concentrates cannot be produced. The material at hand is a taconite which had to be ground to d(90) = 25 µm to guarantee liberation of the iron oxides. The comminution was done by High Pressure Grinding Roll (HPGR) and resulted in smooth surfaces and clear grain boundaries. This is an indication of selective grinding and mineral liberation. Further processing steps included selective desliming, magnetic separation as well as reverse flotation. INTRODUCTION During the last centuries, the processing of iron ores became increasingly important. The coarse-grained, so-called lump ores that are ready for direct usage in blast furnaces without further processing are becoming gradually less abundant. The processing of ultra-fine-grained ores, which in addition require a complex ore beneficiation due to the composition of the material, will progressively gain relevance with increasing resource shortages in the future (Arvidson, 2013). The term “ultra-fine” does not hold a precise definition in mineral processing. In this paper, “ultra-fine-grained” ores are defined by the required grind size for full liberation smaller than 20 µm. Many established mineral processing technologies do not yield satisfactory separation results for ultra-fine materials. Thus, they are limited in their application to produce high-grade concentrates suitable for sintering and pelletizing for direct reduction processes. The production of a high-grade iron concentrate (over 68% Fe) with low silica content (under 2.5% SiO2) is possible from both magnetite and hematite containing ore. In addition to the mineral processing technologies (magnetic and gravity separation, flotation), technologies for the liberation of fine-grained iron ores need to be developed and improved. In contrast to the conventional wet grinding circuit by means of tumbling mills, several future trends in dry and wet grinding and regrinding are already in use. These include technologies such as vibration mills (Palla®Mill), stirred media mills (Vertimill®), vertical roller mills (Loesche) and high-pressure grinding rolls (HPGR) (Jankovic, 2015). This study preliminary investigated the mineral processing of a low-grade, ultra-fine-grained, complex iron ore in a laboratory scale after dry grinding by HPGR to 90% < 25 µm without consideration of the grinding, milling, energy and classification cost."

Jan 1, 2018

By S. Vimalnath

The bioremediation capability of Pseudomonas aeruginosa cells was investigated for the biosorption of lead ions from aqueous solution. The various parameters such as pH, kinetics, biomass loading and concentration of lead affecting the biosorption process were studied. Complete bio removal of lead could be achieved for an initial concentration of 12.4 mg/L at pH 6.2, corresponding to typical industrial effluents. The biosorption isotherm followed Langmuirian behavior and the Gibbs free energy (?G) was determined to be-30.8 kJ/mole, indicative of chemisorption between the functional groups of the bacterial surface and lead. The biosorption kinetics adhered to a pseudo-second order model. The possible mechanisms of interaction of lead with the bacterial cells are discussed. A carbon paste electrode with a coating of biomass was developed for lead ion detection in aqueous solution using cyclic voltammetric technique. Concentrations of lead up to 5x10-5 M could be successfully detected using cyclic voltammetry, which could be improved to a detection limit of 1x10-8 M adopting differential pulse anodic stripping voltammetry (DPASV). Keywords: Pseudomonas aeruginosa, bioremediation, lead, voltammetry

Sep 1, 2012

By Bruno Michaux, Markus Reuter, Martin Rudolph

"It is relatively well-established in the literature that the flotation of calcium minerals using fatty acids as collector is very sensitive to the process water composition. In particular, hard waters have often been reported to strongly reduce the target mineral recoveries due to the formation of insoluble compounds such as calcium and / or magnesium dioleate, thus reducing the amount of collector available for adsorption onto the mineral surface. In this study, the flotation of a fluorite pre-concentrate was performed with tall oil, an industrial collector essentially containing fatty acids. The tests were performed in a variety of synthetic waters to simulate multiple degrees of water hardness, and to differentiate the role of magnesium and calcium ions on the flotation performance. The flotation tests revealed that, under the studied conditions, a significant difference between flotation in calcium-rich and magnesium-rich waters was observed, suggesting strong ion-specific effects in the system. Specifically, calcium-rich waters slightly improved the fluorite recovery, whereas magnesium-rich waters caused a decrease in recovery by as much as 20%. This paper is focused on the flotation kinetics aspect of the system. This approach highlighted the interesting finding that calcium ions did not simply increase the fluorite recovery, but also significantly increased its flotation kinetics. The magnesium ions, on the other hand, had the exact opposite effect.INTRODUCTIONAs the mining industry is facing an increasing number of issues related to its fresh water consumption, the idea of using alternative water sources for mineral beneficiation is gaining significant momentum. As a result, a proper understanding of the role of water chemistry in flotation is becoming more and more urgent, leading to an increasing number of studies on this topic."

Jan 1, 2018

High flotation of iron sulfide minerals at high pH values in copper ores is mainly due to the activation of these minerals by copper species dissolved from copper sulfide minerals during grinding. Several methods have been tested to reduce this copper activation during grinding and therefore to depress iron sulfide flotation. They include grinding the minerals at high pH values or with a less reactive medium such as high chrome, and addition of a thiol collector or copper complexant during grinding. The efficacy of these methods in the flotation of a copper ore was tested against more common methods of depression of iron sulfide flotation. The mechanism of iron sulfide depression in these methods was also investigated.

Jan 1, 2014