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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 L. Y. Wang

In order to produce the iron and steel products with high quality and decrease the output of steel tailings, the quality of molten iron is a critical factor for iron and steel companies, especially the content of sulfidic in molten iron. Hot metal pre-treatment, an important and effective method to desulphur, is widely used in steel production. Millions of tons of slag from desulphurization and slag skimming are produced each year in China, and many more times this amount is stored in slag dams because of the lack of effective means to deal with it. In order to achieve the goal of sustain-able development, recycling these slag becomes necessary. The main objective of this paper is to study the composition characteristics of slag that from desulphurization and slag skimming. The sample was obtained from Anshan Iron and Steel Group Corporation, processed by hot metal pre-treatment. In this study, the chemical components and the mineral compositions of sample were tested. The results of chemical components and iron chemistry phase analysis showed that the iron and sulphide content in this sample were high, and the iron products existed mainly in the form of magnetite, metallic iron, ferrosilite. X-ray diffraction (XRD) and scanning electron microscope (SEM) results indicated that the sample included metallic iron, ferrate, wustite, metasilicate, aluminate, aluminosilicate, white lime and soon. Grading magnetic separation test work showed that magnetic separation was an effective method to recovery iron products and decrease the sulphide content in concentrate, and the tailing could be used as the raw material or padding in cement production.

Jan 1, 2014

By M. Kargar Razi

According to the unique properties and many applications of nano silver powder, it was prepared from acid leaching tail solution. The low value residual gold and silver ions were occurred with fellow heavy metals as pollutants (Fe2+, Cu 2+and Zn2+) in acid leaching tail solution in Mouteh gold mine in Iran. Preparation of nano silver particles was achieved in two steps: first, by addition of ammonia as separation step and second by using different reagents as precipitation and extraction steps. Different controlled parameters were including pH, residence time and temperature, mixing time, and reducing reagents to metals molar ratio. Acid leaching process was carried out with sulphuric and nitric acid via suitable reductants. In order to remove copper, zinc, and silver ions from solution, all of the conditions were controlled. The optimum conditions for preparation of nano silver powder with less than 90 nm were pH 10.5, hydrazine/methanol to silver molar ratio of 3 to 4, and reduction time of 5 min in 45 °C. The results were evaluated via SEM, A.A and UV- Vis spectroscopy analytical methods.

Jan 1, 2014

By Bruce Mathema, Steven Huynh, Terry Cheng, Gerry Gomez

"The use of PM40N, a specialty precious metals promoter in conjunction with a standard Xanthate based collector was extensively investigated in the flotation of a complex, silver-bearing, lead-zinc ore containing naturally occurring graphitic gangue. The ore, considered difficult to treat with conventional reagents, was tested at plant scale to determine the impact of the promoter on silver recovery, lead grade and also on the amount of zinc misplaced to the final lead concentrate.Initial laboratory-scale rougher flotation testing implied significant improvements in the recovery of silver and lead with a marginal amount of zinc displaced. Subsequent mini pilot flotation tests further revealed that a gain in selectivity and recovery could be achieved by adjusting PM40N promoter dosage and incorporating a cleaner flotation step, further improving rejection of sphalerite. Plant trials resulted in an improvement of 3% in Silver recovery coupled with a 2% increase in recovered lead whilst maintaining lead grade in the lead circuit.To date, the use of PM40N as a promoter has enabled the processing operation to significantly increase its plant economics. The partial replacement of the standard Xanthate based collector has also reduced the overall quantity of Xanthate required in the standard circuit by approximately 10% - which is a positive impact on the environment. It is envisaged that further optimization of plant parameters will favor stable operation and continue to boost revenues generated by subsequent improvements in silver metallurgy."

Jan 1, 2014

By C. Abbruzzese, F. Vegliò, S. Ubaldini, R. Massidda

"Gold solubilised during cyanidation can be recovered by precipitation (Merrill-Crow process) or by adsorption onto activated carbon, these being the techniques applied in industrial plants.Precious metals (Au, Ag) adsorbed onto activated carbon are extracted during a subsequent stage in aqueous phase, by various technologies, such as hot elution (70-80°C) or under pression desorption (100-130°), with hydro-alcoholic solutions.This stage is of great interest from an economic point of view, due to the high energy costs. Temperature represents the critical kinetic factor.The aim of this paper was to study the influence of different water/organic solvent mixtures (isopropyl alcohol, ethanol and ethylene glycol) on the desorption process.The experimental work was carried out on laboratory scale, using activated coconut carbon with different temperatures and extraction times, without adding cyanide.Best results have been obtained in this order: isopropyl alcohol > ethylene glycol > ethanol. Starting from gold concentration of about 5 g Au per kg of carbon, best kinetics resulted in 97-100% of gold extraction, after 8 hours of desorption, at a temperature of 80ºC."

Jan 1, 2003

By L. A. Cisternas, R. I. Jeldres, C. Cruz, P. A. Robles

"Previous studies have shown that the floatability of chalcopyrite in seawater at highly alkaline conditions is significantly affected by the presence of clays. The reason is that the species of calcium and magnesium present in seawater under those conditions may act as a bridge between the surfaces of clay and chalcopyrite, generating massive aggregates that then depress. In this context, the objective of this work is to analyze the impact of pretreated seawater with low amount of calcium and magnesium ions on the recovery of a sulphide copper mineral with high kaolinite content as clay. The seawater pre-treatment is done by the addition of sodium hydroxide in a high carbon dioxide environment. The chemical reactions realized under these conditions lead to the formation and precipitation of calcium and magnesium species that are subsequently removed by vacuum filtration. The pre-treated seawater is then used in flotation tests at pH 11 for copper sulphide, where the mineral is synthetically prepared by mixtures of chalcopyrite, kaolinite, and quartz. When comparing the flotation results for different types of water, including seawater and pre-treated seawater, a significant effect is observed: as the seawater hardness decreases, which comprises the calcium and magnesium ions, the recovery of chalcopyrite is increased. However, the effect is markedly enhanced in the presence of kaolinite. Therefore, the results indicate that sodium hydroxide and carbon dioxide are able to remove different species of calcium and magnesium from seawater and could improve the chalcopyrite recovery with high kaolinite content. INTRODUCTIONIn many cases, mineral deposits are found in arid areas with little access to water resources. Water is a fundamental element to carry out the unit operations that achieved the separation of valuable minerals (especially in concentration operations). Seawater has acquired an interesting role in recent years (Cisternas and Moreno, 2014); in fact, it seems to be one of the few viable options to ensure the sustainability of the mining industry in arid zones. At present, there are numerous experiences of industries that use or have used this resource, either by submitting the seawater to a desalination treatment by reverse osmosis or by applying it directly, without desalting. The latter case may involve significant economic benefits (for example, by avoiding the investment of building a desalination plant) and in some cases some operational benefits. A positive aspect is that in general terms the foaming in the saline medium is much more efficient compared to fresh water (Quinn et al., 2014; Castro et al., 2010). Some reports show that the foaming doses required to achieve a certain quality of bubbles are remarkably reduced, reaching exceptional cases such as Xstrata's Raglan concentrator, where it did not even include foaming to carry out the operation. This fact is quite promising, considering that some researchers have stated that controlling the quality of bubbles and foam could float minerals through coarse particles. This would lead to multiple benefits, such as energy savings by avoiding excessive grinding and a lower presence of fine ore that causes major problems in water recovery operations by gravitation (such as thickening) and in tailings management. However, seawater also causes significant challenges in multiple operations (Jeldres et al., 2017, 2016; Castro et al., 2010), as for example in minerals with high clay content (Uribe et al., 2017). In fresh water, the presence of clays minerals in ores is already a major problem in the flotation stages since the operation becomes difficult to be controlled, and operators are commonly forced to increase the consumption of reagents because the collectors are deposited on the clays' surfaces reducing froth stability (Farrokhpay and Bradshaw, 2012). Sometimes the use of rheology-modifying reagents should also be incorporated since the pulps become more visc"

Jan 1, 2018

By Yuemin Zhao

Pre-combustion cleaning of coal plays a key role in the process of efficient and clean utilization of coal resources. Recently, wet beneficiation of coal is predominant around the world. Nevertheless, wet beneficiation processes are limited by the increasingly serious problem of worldwide shortage of water, especially in China. Thus, it is imperative to develop efficient dry coal beneficiation techniques. Currently, several technologies such as air dense medium fluidized bed, compound dry cleaning and air jigging have successfully achieved high-efficiency separation of 50~6 mm coal. However, in recent years, a large amount of fine coal is generated as the mechanized mining technology has been progressively deployed in coal sector. Thus, it is necessary to develop efficient dry beneficiation techniques for fine coal. In recent years, many countries including China, India, Canada, Germen, and Australia have carried out many research works on fine coal dry beneficiation techniques. China University of Mining and Technology has carried out systematic researches on the introduction the vibrated energy to traditional air dense medium fluidized bed for fine coal beneficiation. This paper studied air dense medium vibrated fluidized beds (ADMVFB) for fine coal dry beneficiation. The experimental results show that the coal of <6 mm size can be beneficiated in an ADMVFB efficiently with the E value of 0.065~0.085, the separating density can be adjusted in the range of 1.45~2.2 g/cm3, and the lower limit of beneficiation can reach to 0.5 mm. Keywords: fine coal, air dense medium vibrated fluidized bed, coal separation, dry separation

Sep 1, 2012

By Junwei Han, Wenhua Li, Wenqing Qin, Fen Jiao, Wei Liu, Jiaqi Xu

"A novel technology was developed to study the process of recycling copper from waste printed circuit boards (WPCBs), which are the main source of metal production in the next decades. The chemical compositions of the WPCBs were investigated. The results indicated that the PCB powder was mainly composed of copper (38.5 wt.%), iron, aluminum, and non-metallic materials. Copper is mainly in the form of Cu and is the most valuable metal for the recycle of WPCBs. The concentrated WPCBs powder, obtained by the mechanical process, were pressed as the anode, which was directly electrolyzed to produce copper. The effects of H2SO4 concentration, Cu2+ concentration, current density, pole pitch, and liquid-to-solid ratio on the voltage, current efficiency, and copper extraction were investigated. The results indicated that the optimum conditions were liquid-to-solid ratio of 30 mL/g, current density of 571 A/m2, sulfuric acid concentration of 180 g/L, 50 g/L of copper ion, polar distance of 3 cm. Under the conditions, a desired current efficiency could be achieved. Meanwhile, about 95.62% Cu was recovered from the WPCBs. The experimental studies also revealed that the purity of copper obtained at the highest current efficiency was higher to 99.98%. Produced copper sheet were characterized by X-ray diffraction (XRD). XRD analysis indicated that the copper was the main phase. INTRODUCTION With the rapid development of electronic industry, more and more waste electronic and electrical equipments (WEEE) are generated every year (Fogarasi et al., 2012; Liang et al., 2013). The production of printed circuit boards (PCBs) is the base of electronic industry, because it is the essential part of all electrical and electronic equipments (Schlummer et al., 2007). As a result, a considerable amount of waste PCBs containing plenty of heavy metals have to be treated. In general, PCBs contain about 28% metals that are abundant non-ferrous metals such as Cu, Pb, and Sn. Printed circuit boards can be considered as a secondary resource for recycling rather than wasting. The contents of gold and silver respectively reach 80 g/t and 3300 g/t, which are much higher than that of primary ores. Copper is the main metal of PCB and its content is as high as 26.8% ( Zhang et al., 2009)."

Jan 1, 2018

By Axel Pankewitz, Andrew Smith, Mathias Stender, Christian Behrens

"Particle size measurement is one of the most important factors in obtaining peak performance of the mineral processing plant in order to ensure efficient milling and flotation circuit operation. Off-line particle distribution analysis technologies only allow an infrequent check of the ore slurry size and hence do not allow for timely process monitoring or intervention. Most existing on-line particle size analysers suffer from a variety of disabilities such as poor statistics, non-representative sampling or mechanically complex setup. This paper will describe an Ultrasonic Extinction based method which overcomes many limitations of existing online analysers and has proven its performance for mineral applications over many years. Installation examples will be given. Since new technologies usually raise e questions about comparability and agreement to common particle size analytical methods e.g. sieving or laser diffraction analysis, extensive studies were performed comparing these different technologies to quantify the quality of results as well as its mathematical robustness."

Jan 1, 2014

By Q. Zhang

The flotation behavior of jamesonite was investigated with ethyl xanthate as a collector. It has been shown that jamesonite has good floatability from pH 2 to pH 12, and relatively poor floata-bility at pH>12. The flotation of jamesonite was also dependent on pulp potential at certain pH val-ues. The potential-pH range for jamesonite flotation was established. The FTIR spectroscopy analy-sis and XPS measurement showed that the major adsorption product of ethyl xanthate on jamesonite was lead ethyl xanthate and antimony ethyl xanthate. The intensity of the FTIR signals of metal ethyl xanthate adsorbed on jamesonite and the flotation response of jamesonite were correlated with pulp potentials.

Jan 1, 2014

By Y. S. Sun, P. Gao, Y. F. Li, J. W. Yu

"Oolitic hematite ore is one of the most refractory iron ores in the world. It is not feasible to separate iron minerals from raw ore by conventional mineral processing methods. In recent years, a new technology called coal-based reduction followed by magnetic separation has been employed to produce metallic iron powder from oolitic hematite ore effectively. In order to find the nucleation mechanism, a thermodynamic analysis of the carbothermic reduction of oolitic hematite ore was conducted by the HSC 6.0 thermochemical software. The phase transition and microstructure changes during the coal-based reduction were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the iron oxides in the oolitic ore were reduced to metallic iron following the route of Fe2O3–Fe3O4–FeO–Fe in reduction process. The reduction reactions preferentially occur in the high activity regions to form a higher concentration of Fe elements, and then more supersaturated Fe separated out to form new phase nuclei. Under the action of homo-aggregation and principle of minimum free energy, the iron cores continuously absorbed migratory Fe around and grew into quasi-spherical iron particles embedded in slag phase. INTRODUCTION With the rapid increase of steel industry, premium grade iron ore in China has been gradually exhausted, and its supply has become bottleneck for the development of iron and steel industry (Guo et al., 2015). Therefore, it is urgent to exploit the refractory iron ores, such as oolitic hematite ore. Oolitic hematite ore is widely distributes in France, Germany, America, Canada, Pakistan, China, and among other countries (Maynard and Van Houten, 2004; Li et al., 2011). In China, the explored reserve of oolitic hematite ore is 3.72 billion tons, which accounts for approximately 1/9 of total iron ore resources of China (Gao et al, 2016). Oolitic hematite ore possesses complex composition,"

Jan 1, 2018

By Sarra Scherbakova, Alexander Kurkov, Andrey Egorov

"Deep concentration of iron ores involves extraction, in addition to magnetite concentrate, of hematite and martite concentrates and recovery of other valuable components. A flotation technology was designed specifically for finely disseminated hematite ore, allowing producing saleable hematite concentrate containing 64-66% Fe. The main process challenge is caused by the presence of other ferruginous minerals such as carbonates, silicates, and phosphates, and fine hematite and martite mostly concentrated in the -0.044 mm fraction. Main operations of the processing circuit are removal of slime, flotation to remove impurities (carbonates, phosphates etc.) with an anionic phosphorous collector in an alkaline environment, hematite and martite flotation using same collector in a slightly acidic environment to produce commercial iron concentrate. Tailings of wet magnetic separation of magnetite containing 24.5% Fe and finely disseminated hematite ore containing 51% Fe were processed to produce iron concentrates with a yield of 15% and 50%, respectively, containing approximately 65% Fe and 5% of silica. Hematite flotation tailings had the highest content of gold (up to 0.09 - 0.11 g/t), while in other products it never exceeded 0.02 g/t. Using a Knelson concentrator was able to recover 40 to 45% of the gold into 3.31 g/t Au gravity concentrate. The success of gravity concentration is due to high gravitational contrast of gold to mostly quartz and aluminosilicates in the hematite flotation tailings. In general, the proposed process can be used as a solution to the challenge of selective concentration of finely disseminated iron minerals."

Jan 1, 2014

By A. A. Lavrinenko

There are discussed the possibilities of using of flotation tailings of platinum-copper-nickel sulfide ores of the Norilsk region for the preparation of backfill mixture instead of a specially produced rock and binder materials to reduce the cost of stowing operations and impact on the environment. It is shown that due to the presence in the tailings of flotation up to 10% of sulfide sulphur, which reduces the strength of the fill materials, and more than 1 g/t PGM it is necessary the preliminary extraction of the sulfides in the product for further processing that give an opportunity to reduce the losses of valuable components. It is shown that by the flotation of the current tailings it is possible to extract 91% of sulfide sulphur, 60% of palladium and 30% platinum in 17% sulfide concentrate containing 2.1 g/t palladium, and to reduce the sulphur content in the tailings up to 0.7%. Due to the easy oxidation of pyrrhotite, there is recommended fractional delivery of the collector with a total consumption 200 g/t. There are discussed results of the flotation study with an additional collector of PGM (sodium diizobutyditiophosfinate), which one show the possibility to increase extraction of platinum on 45%, as well as extraction of sulphur and palladium. For the flotation of sulfides and PGM from the current tailings there is recommended a combination of collectors for primary flotation and only butyl xanthate using in control operations. The possibility of using sludge fraction of the current tailings as a component for the preparation of the combined cementing materials after exposure of sulfides is analyzed. It is shown that the efficiency of the flotation of sulfides from this fraction can be enhanced using selective flocculants. There are discussed the advantages of implementation of completely hydrophobic butadiene-styrene copolymer in comparison with partially hydrophobic polymers. There is discussed an efficiency of the mechanochemical treatment of old tailings in turbo mill and sulphuric acid to remove oxide films from the surface of pyrrhotite before its flotation. Due to the pretreatment operation there is achieved increasing of sulphur extraction and after the introduction to the flotation circuit three control operations there is produced the fill material with sulphur content 2.5%. Keywords: tailings, copper-nickel ore, pyrrhotite, butyl xanthate, sodium diisobutyl dithiophosphinate, selective flocculation, butadiene-styrene copolymer, mechanochemical treatment

Sep 1, 2012

By Milind Chikhale, Ranjeev Kumar, Keshav Tyagi

Ore characterisation including mineralogy and beneficiation testwork of an ore is very important for determination of possible products and their quality. The results of such study help in ascertaining the beneficiation process route for the ore. The present study deals with ore characterisation study and beneficiation testwork on the samples of hematite iron ore with goethite impurity. The characterisation study reveals that the hematite is under alteration stage to goethite which has become an integral part of hematite. High goethite/limonite content is enhancing the loss of ignition content of the ore and reducing its Fe content. The findings indicate that in case of hematite iron ore associated with goethite and limonite, it is difficult to achieve high grade of concentrate above 65% Fe. It depends on the amount of goethite and limonite minerals and their association with hematite. These minerals contain aluminous impurities and hence, their rejection becomes essential. Separation of limonite and of goethite to limited extent is possible. In case of goethite, effective liberation is not achieved where it occurs as surface alteration product of hematite grains. The gangue mineral reported are clay and gibbsite, and are closely associated with iron minerals. The test work results indicate the grade and recovery of Fe along with alumina and silica content in lumps, sinter fines and pellet feed fines that can be achieved for the different ore types vis-a-vis the percent of available hematite in the ore. The recovery of iron is dependent on the hematite available and the loss of iron values in tailings is more because of rejection of limonite and goethite.

Jan 1, 2014

By A. V. Abshilawa, D. G. Talakhadze, R. I. Sturua

"Processing of the tailings accumulated over the lifetime of Madneuli Copper Concentrator is an opportunity to extract additional salable copper and gold products. This paper presents a pre-concentration process for the valuable components (copper and gold) of the accumulated tailings. The developed process makes it possible to obtain a copper pyrite concentrate with a yield of 14.05%, copper grade of 1.36%, and recovery of 83.22% containing 3.78 g/ton of gold at a recovery of 84.31%. The bulk concentrate is produced by a combined process bringing together selective flotation to produce salable copper concentrate and hydrometallurgical processing of the selective flotation tailings to recover gold. KEYWORDS: FLOTATION, ALBION PROCESS, LEACHING, COPPER CONCENTRATE, SELECTION Madneuli Copper Concentrator, Georgia, was put into operation in 1975. Over its lifetime, 40 mn tons of tailings have been accumulated at the tailings storage facility (TSF). Sampling of the TSF has indicated that the average copper and gold grade is 0.23% and 0.56-0.65 g/ton, respectively. Accordingly, the TSF can be classified as a technogenic reserve. This paper discusses pre-concentration of valuable components using flotation, followed by processing of the bulk concentrate in the Albion process. Mineralogical analysis of the accumulated tailings showed that the main ore mineral is pyrite (11.71%). Copper minerals are mainly represented by chalcopyrite (0.7%). The main nonmetallic mineral is quartz (67.3%); sericite, chlorites, etc. also occur. Pyrite is present both as liberated grains and intergrowth. The absolute majority of copper minerals are found as intergrowth with pyrite, less often with quartz. Ore minerals are slightly oxidized. Chemical analysis results are shown in Table 1. Particle size distribution shows that the size class -0.2 mm - 0.045 mm has the highest grade of 0.85 to 0.97 g/ton of gold. Size class +1.25 mm has the lowest grade. Based on the chemical and mineralogical studies and particle size distribution, an optimized process was developed for pre-concentration of the valuable components prior to hydrometallurgical processing. Several gravitation, direct selective, bulk, and bulk selective flotation processes were trialed. (1,2)"

Jan 1, 2018

By G. Sedelnikova

This paper is aimed to elucidate the problem of copper losses in pyrometallurgical slag. Currently, flotation is used to recover copper from the slag and return the metal into the pyrometallurgical process, but the percentage of recovery frequently remains unacceptable. The process of copper leaching from the slag flotation tailings using biologically regenerated ferric sulfate is considered here as an approach to the issue. A sample of the slag flotation tailings containing 0.67% Cu and 4.99% Zn was supplied by the Urals Mining and Metallurgical Company (UGMK, Russia). The Cu and Zn speciation analysis of the sample demonstrated that Cu occurred as 58.1% oxide, 15.4% native Cu, and 18.1% secondary sulfides whereas chalcopyrite proportion was as low as 8.4%. Prevailing Zn species were refractory (58.9% Zn ferrite), and zinc oxide and silicate species made just 37.2% of the total metal content. The silicate generated silica gel that strongly hampered filtration. As demonstrated, Cu recovery is a possibility, which is apparently not the case with Zn. In this work, the stirred tank bioreactor acid leaching employing bacterial Fe3+ sulfate solutions was studied, with ferric sulfate being a product of Fe2+ biological oxidation and not the chemical reactant adding of Fe3+ sulfate. Acidithiobacillus, Sulfobacillus, and Leptospirillum bacilli were employed in Fe2+ biooxidation. Temperature, pH, Eh, S:L ratio, leaching time, and Fe3+ concentration in the source leachate as the process controls were considered. As demonstrated, the process employing biologically regenerated ferric sulfate proved to be more efficient than conventional chemical leaching. Under the optimum conditions, the proportion of Cu extracted into leachate during 2 hours was 79.1%, and that of Zn 27.2%. Precipitation of high-grade Cu sulfide served to extract the metals from the leachate, and Cu extraction was 99.7%. All in all, 23.2% Cu, 0.03% Zn, and 0.02% Fe was returned into the pyrometallurgical process. Keywords: slag flotation tailings, copper leaching

Sep 1, 2012

By L. Gutierrez, M. Jeldres, R. J. Jeldres

"Clays are present in a large number of mineral deposits and are commonly found as gangue. Its complex chemical structure, characterised by anisotropic surfaces, makes its presence a permanent challenge for flotation operations, increasing the reagent consumption, decreasing the quality of the concentrate, and changing the rheological properties of the system. In this context, the main objective of this research is to improve the floatability of chalcopyrite minerals in the presence of clays by using guar gum, a low molecular weight organic polymer, which acts as a surface coating agent for clays. Clay Minerals Society provided the kaolinite sample and the chalcopyrite sample was purified from mineralized rock specimens obtained from Ward’s Natural Science Establishment. Micro flotation tests were carried out in a 150 cm3 Partridge-Smith cell, using compressed air as the gas phase at a flow rate of 80 cm3/min. Potassium amyl xanthate (PAX) and methyl isobutyl carbinol (MIBC) were used as a collector and a frother, respectively. The results showed that the use of guar gum improves the recovery of chalcopyrite in the presence of kaolinite because it induces the formation of clay aggregates that settle by gravitational effects, preventing the 'coating effect' and decreasing excessive collector consumption. pH played a key role in the guar gum performance, which was most effective at highly alkaline conditions (pH 11), where the copper recovery improved from 73% to 90%. The work has significant implications for the mineral flotation in the presence of clay minerals.INTRODUCTION The mining industry is continuously confronted with challenges that alert the sustainability of the sector. There is little availability of water, the grade of the deposits are getting smaller, and the gangue is becoming more complex. Usually, clays are part of the gangue in numerous systems, including copper ore, porphyry, nickel, platinum, etc. (Senior & Thomas, 2005). The structure is mainly composed of layers of tetrahedral silica (T) and octahedral alumina (O) that join in certain proportions: 1: 1 (T-O) and 2: 1 (T-O-T) (Theng, 2012). Also, they expose two crystallographically different surfaces: the faces, which tend to be negatively charged, and the edges, which carry a charge that changes from positive to negative depending on the pH (Van Olphen, 1977). One of the most common clays in copper deposits is kaolinite, whose structure is composed of an octahedral sheet of gibbsite bound to a tetrahedral silica sheet in the ratio 1:1"

Jan 1, 2018

By G. Mucsi, F. Kristály, Á. Rácz, É. Gregus, K. Bohács

"Stirred media mills are widely used in the industry for fine grinding. Most of the applications work in wet mode, however dry grinding in stirred media mill comes forward more frequently nowadays. The present paper deals with the differences and similarities of the wet and dry grinding in stirred media mill from energetic and mechanochemical point of view as well. Grinding experiments in batch stirred media mill were carried out with different materials. During the experiments zeolite and kaolin were used as feed material. The grinding experiments were carried out at different stress energy and stress number values; the grinding work was measured during milling. After grinding X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), particles size analyzes by laser scattering were carried out on the ground materials. As a result of the systematic grinding and analytical measurements a comprehensive comparison was carried out on the wet and dry grinding and their usefulness for mechanical activation in stirred media mill. INTRODUCTION The natural zeolites are crystalline hydrated aluminosilicates of alkali and alkaline earth characterized by the structure that contains frameworks responsible for the high cation exchange capacity (CEC) and absorption capacity. The frameworks are interconnected by cavities and resided by cations variable in size, coordinated by water molecules. Since zeolite comprises SiO4 and AlO4 tetrahedra interlocked by oxygen atoms that are situated in the structural nodes, their characteristics differ due to the varieties in the structure-directing agents and Si/Al ratio (Colella and Wise, 2014; Malekian et al., 2011; Terzic et al., 2017). The most common natural zeolite occurring in high amount, of industrial importance and involved in milling and MA is the clinoptilolite, in the literature equivalent to “natural zeolite” designated for high clinoptilolite bearing volcanic tuffs. Its amount in the host rock must reach ~ 40 % by weight to obtain the CEC and adsorption desired in its applications. In the highest quality rock might reach 80-90 % by weight (Favvas et al., 2016), but most often is the 40-60 % by weight content, associated with smectites, improving the CEC and adsorption of the tuffaceous rock. The application of such natural zeolites is problematic in many cases due to high silica (quartz, cristobalite and volcanic glass) content and beneficiation (concentration and extraction of pure zeolite) are not feasible. Thus, mechanical activation is a possible way to alter the other than clinoptilolite minerals generating high specific surface area and functionalized particle surfaces to enhance adsorption, reaction or particle adhesion. The zeolites easy availability and the utilization cost-effectiveness have prompted the research on their physicochemical and structural properties (e.g. adsorptive and molecular-sieve activity, heat resistance, and microporous cage structure) and finding new options for their application (Kusuma et al., 2013; Musyoka et al., 2014; Rida et al., 2013; Terzic et al., 2015b). Apart from the presence of exchangeable framework cations which are crucial for the adsorption ability, and a certain degree of pozzolanic reactivity. The thermal stability of dehydrated phases is another important characteristic for use of the zeolite in composite materials that are exposed to high temperature. Thereby, the zeolites found a wide application possibility in the design of the construction composites (Albayrak et al., 2007; Najimi et al., 2012; Vejmelková et al., 2015), as well as for resolving of the environmental protection issues like wastewater refining or heavy metal elimination (Gómez-Hortigüela et al., 2014) even from contaminated groundwater using passive methods like permeable reactive barriers (Gombköto et al, 2016). The grinding treatment of zeolite is a common and frequently applied procedure, both on laboratory (Bohács et al. 2017, Faitli and Czél, 2014)"

Jan 1, 2018

By Dmitriy Makarov

The paper presents the modeling and analysis of oxidation of pyrite copper-zinc ore samples from the Letnee, Yaman-Kasy and Valentorskoye deposits. It is found, that the oxidized samples contain copper and zinc sulfates that are leached under the sample and water contact. It is shown, that sulfide floatability is decreased by the longer-term oxidation.We advise to improve nonferrous metals recovery by joint leaching and ultrasonic treatment of oxidized compounds. Study of the geotechnological processes of non-ferrous metal extraction, on the basis of two copper-zinc ore deposits shows, that heap leaching is of little use for the ores of the Letnee deposit. Leaching results for the Yaman-Kasy ore showed more promise.

Sep 1, 2012

By D. Tao

A novel rotary triboelectrostatic separator has been developed and patented recently at the University of Kentucky with unique features, including a high efficiency rotary charger, charger electrification, laminar air flow, etc. A parametric study has been performed with a coal combustion fly ash sample to investigate the effects of major operating parameters on the process performance. Most significant operating variables and optimum conditions were identified. Separation tests performed with four fly ash samples indicated that the rotary triboelectrostatic separator showed effective fly ash separation.

Jan 1, 2014