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By Manisha Singh, Manikanchan Sarkar

"Presently the global steel production is mainly based on iron ore sourced from high grade hematite deposits. India has large deposits of good quality hematite ore but with the prevailing practice, such deposits are depleting fast and getting exhausted. However, apart from such high grade iron ores, India is also endowed with large reserves of low grade iron ore, such as BHQ (Banded Hematite Quartzite), BHJ (Banded Hematite Jasper), BMQ (Banded Magnetite Quartzite) and Magnetite. In the present situation, it has become necessary to focus attention on upgradation of these low grade ores to produce useable concentrate. It augurs well that already substantial investigation work has been carried out in this respect and a few plants have been set up in India and abroad. One important aspect in this regard is the process route options with optimum yield and grade. Some of these low grade ores, particularly magnetite, are found to contain high phosphorous level, removal of which poses a major challenge. Since the grade is low, substantial upgradation necessitates fine grinding for appropriate liberation. Fine grinding is energy intensive and needs attention to achieve economy in this regard. Large quantity of tailings is generated in the process, wet disposal of which gives rise to a lot of hassles and hence, possibility of dry disposal of the same needs to be explored. The experience of the authors, with regard to aforesaid aspects which has been gained in course of carrying out relevant assignments is presented in this paper."

Jan 1, 2014

By M. Niinae

Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble sub-stances. At a higher pH, the soil particles sorb more heavy metals, such as cadmium, than at a lower pH and the precipitation reactions of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering clean up more difficult and electrokinetic extraction inefficient. There-fore, the acidification of soils is very important to increase the clean up efficiencies of heavy metals, such as cadmium by electrokinetic method from contaminated soils. In the present study, acidification of soils and cadmium transport are predicted with a numerical method in which electrical flow is coupled with hydraulic flow, and the sorption process in the soils is induced in the model. The effects of some factors such as electrode configuration, electric field strength and electrode spacing for saturated soils are investigated using this numerical model. The results obtained this study are summarized as follows: The two-dimensional electrode configurations containing cathode surrounded by three or more anodes rapidly acidify the soils and remove cadmium from soils compared with one-dimensional electrode configuration. However, two-dimensional electrode configurations develop spots of inactive electric field between cathodes. A larger electrode spacing increases the processing time required, and it was also found that a larger electric field strength reduced the processing time required.

Jan 1, 2014

By M. X. Jia

This paper discusses two mineralogy characteristics that may affect the flotation of sulfide ore. The first one, process mineralogy study on a Cu-Ni sulfide ore shows that valleriite and tochilinite are incline to form on chalcopyrite, pyrrhotite and serpentine surface, and the further guess is that the formation of valleriite and tochilinite may also causes the serpentine transform to talc, so the serpentine surface is a phase of talc or a transition phase from serpentine to talc and this enhances the flotability of the gangue minerals. The second discussion on the flotation behavior of the sulfide minerals from the point of view of the mineral semiconductor character.

Jan 1, 2014

By J. K. Afidenyo

Microbial pretreatment of a double refractory gold ore was investigated using a white rot fungus, Coriolus versicolor (ATTC 20869) to improve gold extraction. A series of preliminary tests were conducted to determine the amenability of the ore to fungus degradation. Pulp density, temperature, pH and retention times were the process variables considered. Both a single. Stage and two-step processes were studied to establish process conditions. During the single stage process, the ore was contacted with the fungus culture (biotic) for 3weeks at 30°C and pH 10.0. For the two-step process, the first step involves ore contact with the culture medium (abiotic) at 45°C and pH 10.0 followed by fungal contact (biotic) at 30°C. Results indicated that carbonaceous matter is not degraded but passivated by the fungus; as preg-robbing activities dropped significantly from 18.1% to below 1.0%. The single stage process resulted in higher gold recovery than the two-step process Gold ex-traction by cyanidation of the pretreated ore was 78.9% for the single stage compared with 15.0% for the untreated ore. In the two-step process, only 73.3% gold extraction was achieved. Application of the two step process conditions to a high grade flotation concentrate, resulted in 93.3% gold ex-traction as against untreated concentrate of 30.5%. The results show that the microbial pretreatment process degraded sulfide sulfur, passivated carbonaceous matter and enhanced gold extraction from double refractory gold ore and concentrate.

Jan 1, 2014

By Nani Pajunen, Kari Heiskanen

"Products filling our societal needs, like communication and transportation needs, are becoming more sophisticated and efficient. The cost has been an increased complexity of material combinations. The same trend is also seen in investment goods. As an example, different crusher types have almost doubled the power to weight ratio in a relatively short time while producing even higher crushing rations. This has been possible by high performance materials and advanced designs. Another example is new hybrid materials in prefabricated high-strength steel structures in construction with the aim to lighten the products and obtain energy savings in the use phase e.g. in transportation. This development in general has made the end of life phase obscure. Recycling is often understood as the first phase of the material cycle. This has been supported by the material centric point of view. When, say indium, has been collected and mechanically treated to a concentrated fraction, it is assumed as recycled. This is not the case. The same applies to special steel alloys where one tends to lose some of the alloying elements to slag or even into the gas phase in the melting and refining stage, not in the earlier steps of recycling. At present there is no clear understanding of recycling of hybrid materials and no clear willingness to create new functional recycling systems. As the EU directives and most of legislation worldwide are based on the material centric thinking and implemented even on total mass recovery basis there is neither legislative incentive nor very strong economic incentives to work out the problem. In our research, we focus on industrial design towards sustainability from a product centric point of view from product collection to final metallurgical steps. It is vital, in the design phase of product, to understand the effects of decisions on recyclability to a saleable raw material. Main goal of our work is to create the fortunate circumstances in supply chain - to pass the barriers and find the effective and fruitful drivers - for reasonable use of raw materials and recycling co-operation with industry. The boundary conditions in the work are extractive metallurgical performance and the economic viability of all the steps. It can be shown from our work that small design alterations may have a large impact on the recyclability. The earlier the decisions are made in the product life chain the more positive impact they will have. It can also be shown, that a strong processing and metallurgical industry is vital to any meaningful recycling of the modern EoL products. Finally, it is also question of the individuals and values: supply and demand. Are you ready to take up the gauntlet: demand recyclable products."

Jan 1, 2014

By Long Han, Jianyuan Liu, Ping Ying

"Particle-bed compressive stressing is the main work mechanism of comminution by high pressure grinding rolls(HPGR). An experimental study on comminution and mineral liberation of two copper sulfide ores was carried out using a piston-die compressive stressing rig to simulate the situation of comminution with HPGR as the final-grinding device. The tests carried out include compressive comminution tests on particle-bed with narrow-size feed, and the locked-cycle comminution test on particle-bed with broad-size feed, which was then compared to a corresponding locked-cycle test of ball-mill grinding. The narrow-size feed is made up of particles in the size range 2.36~3.35 mm, whereas the broad-size feed of particles in the size range 0~3.35 mm. The liberation analysis for copper-mineral in the comminution products was accomplished using BPMA system – an automatic mineral liberation analyzer developed by BGRIMM. The influences of the stressing intensity and the method of comminution on the copper mineral liberation are discussed in terms of product size distribution, copper-metal deportation among size fractions, distribution of copper mineral among particle-size and particle-grade classes, degree of mineral liberation in size class as well as degree of mineral liberation overall.INTRODUCTION Traditionally, comminution process commonly applied in mineral processing is a flowsheet consisting of crushing of crude ore with conventional crushers, followed by grinding of the crushed ore in tumbling mills. In last decades, the energy-efficient HPGR (high-pressure grinding rolls) has found its application in mineral processing, mostly as tertiary or quaternary crusher to generate a fine-crushed product either as feed to subsequent grinding or as feed to a pre-beneficiation process before further grinding. Compared with the process of conventional crushing followed by grinding in ball mill, this mode of HPGR-application can achieve energy saving to some extent by reducing particle size of the feed to ball milling, and by reducing amount of the feed to ball milling if a significant portion of tailings in relatively coarse particle-size range can be discarded at the pre-beneficiation stage. In recent years, the approaches of letting HPGR take more comminution work from ball mill by applying it in semi-finish grinding mode or even finish grinding mode have been discussed (Burchardt, 2014). Although HPGR finish-grinding has been successfully applied in the cement industry for grinding of cement clinker and raw materials, this mode of HPGR application has yet rarely been implemented in mineral processing, despite the advantage of more energy-saving and other potential benefits such as preferential breakage, internal damage of particles and enhanced mineral liberation which may lead to a better downstream processing performance. The reasons for the retardation of the progress of this kind of HPGR-application in the mineral industry lies not only in that a finish-grinding with HPGR has to be operated in dry condition whereas most of ore-beneficiation processes like flotation are operated in wet condition, but also in that there are large variety of ore materials with various complexity of processing technology, which need to be addressed on a case-by-case basis with a lot of test work, in order to evaluate the potential advantages or disadvantages of this application."

Jan 1, 2018

By Jyotirmoy Sarma

The surface-active agent, like sodium humate, in the present systems produces a very stable suspension. Saline water up to 15% is used as a flocculating agent for recovery of water from the dispersed phase containing 1% solid. The recovered water in the presence of humate at different concentrations (0.05-0.2%) and at pH 8 also produces a stable dispersed phase of iron ore fines and tailings. The beneficiation techniques adopted in the present systems can increase ~ 2-3% iron value in the concentrate of iron ore fine, however, for tailings the increase in iron value is not observed. Keywords: beneficiation, flocculation, iron ore fines, tailings, saline water, surface-active agent

Sep 1, 2012

By K. A. Natarajan

"Interaction with microorganisms results in significant surface chemical changes on minerals. For example, chemolithotrophs such as Thiobacillus ferrooxidans and Thiobacillus thiooxidans significantly alter the surface chemistry of several sulfide minerals such as pyrite, chalcopyrite, sphalerite and galena. Heterotrophic bacteria such as Bacillus sp. could alter the electrokinetic properties of oxide minerals such as hematite, alumina, silica, kaolinite and calcite. Microbe-mineral interactions could thus be beneficially utilised in mineral beneficiation as different from bioleaching. Microbially induced mineral beneficiation unlike bioleaching deals with interfacial phenomena at mineral-solution-bacteria interfaces and surface chemical changes are brought about at very rapid rates amounting to a few minutes resulting in mineral separations in an aqueous medium.In this paper, the role of acidophilic chemolithotrophs such as Thiobacillus thiooxidans and neutrophilic heterotrophs such as Bacillus polymyxa in the beneficiation of sulfide and oxide minerals is illustrated. Mechanisms of bacterial attachment on various sulfide and oxide minerals are outlined with respect to the influence of bacterial interaction in bringing about mineral surface hydrophobicity or hydrophilicity. The role of bacterial cells as well as metabolic products such as bioproteins and exopolysaccharides in significantly altering the surface chemistry of sulfide minerals such as sphalerite and galena and oxides such as hematite, alumina, silica and calcite is discussed with probable mechanisms. Possibilities of generating mineralspecific bioreagents are outlined with respect to bacterial adaptation to mineral substrates."

Jan 1, 2003

By Bo Feng

The development of surface charge of serpentine mineral and implications for sulphide ?otation have been studied through flotation tests, sedimentation tests, zeta potential measurements and optical microscope photos. The results show that the serpentine mineral was positively charged at an extensive pH range, with an isoelectric point (IEP) of 11.9. The magnitude and sign of the pyrite particles were pH dependent and were negative for pH values above 2. At pH value 9, where ?otation of nickel sul?de ores is routinely performed, serpentine and pyrite particles attract through an electrostatic mechanism. Slime coatings of serpentine adhere to the surface of pyrite, reducing pyrite flotation recovery. The removal of magnesium ions from the serpentine surface by acid leaching results in a decrease of serpentine IEP and eliminates the adverse effect of serpentine on pyrite flotation. Therefore, it has been clearly established that the surface charge value developed in the serpentine/aqueous electrical interface is a function of the serpentine surface incongruently dissolution. As a result of hydroxyl dissolution, the magnesium ions are left in serpentine surface, which is responsible for serpentine surface charge. The methods, which can remove magnesium ions from serpentine surface, can be used to eliminate the adverse effect of serpentine on pyrite flotation.

Sep 1, 2012

By K. V. Fedotov, E. V. Zelinskaya, O. V. Ulanova

"Mining enterprises, in particular, those on the territory of the Siberian platform, produce large amounts of pumped water, which cannot be recycled because of its high mineralization and, thus, is discharged as liquid waste either back into the ground or onto the surface. However, groundwater is often a valuable raw material and a source of useful chemical substances. Brines are unique groundwaters. In the current environmental and economic situation, the huge loss of natural raw materials and their deliberate conversion into wastes is unaffordable. The exploration of non-traditional sources of minerals such as the hydromineral resources (including pit water) is a matter of rational nature management. The industrial value of brines of the Siberian platform is due to the high contents of rare alkali and earth alkaline elements (lithium, rubidium, cesium, strontium, bromine, etc.). The absolute concentrations of these elements in brines are tens of times higher than the lower limits of the mining cut-off. The long-term data analysis was performed to estimate the environmental impact of liquid waste from two mining enterprises, namely, Korshunovskii (Irkutsk region) and Udachnaya (Southern Yakutia). The study was focused on the prospects of hydromineral resources as non-traditional sources of valuable elements and the exploration of technological processes for the selective extraction of rare alkali and earth alkaline metals from natural multi-component brines aimed at decreasing their negative environmental impact. The environmental and economic efficiency was proved for the processing of complex brines and the integrated selective extraction of rare earth metals from sodium chloride brines of the Korshunovskii plant and calcium chloride brines of the Udachnaya plant based on the ion exchange sorption, eluent chromatography, flotation, crystallization, and freezing techniques. The basic technological schemes were developed for the metal extraction from pit water and brines.INTRODUCTION In the Irkutsk region (the Angara–Lena artesian basin) and in Yakutia (the Olenek and Tunguska artesian basins), several mineral deposits are developed and, incidentally, aquifers bearing brines of different types are opened, which are eventually converted into liquid production waste (Rusetskaya et al., 1994) This raises the issue of the burial or utilization of brines since their use within the water circulation is impracticable under the existing technological conditions while their discharge into the surface watercourse is unacceptable because of the harmful environmental impact."

Jan 1, 2018

By D. Pirouzan

It is customary to use more than one stage of flotation to obtain an acceptable level of separation of valuables. Flotation circuit design is usually accomplished by applying empirical rules which usually results in operations not working at their optimum conditions. Given the capabilities of genetic algorithms (GA) in finding an optimum solution in a very disturbed search spaces, they can be used to obtain the desired flotation circuit configuration. In flotation circuit configuration and optimization problem, a combination of metallurgical parameters such as yield and concentrate ash content could be used as the fitness function for the genetic algorithm. The multi-objective nature of the problem justified to use Pareto method to arrive at a set of solutions. The appropriate configuration based on technical or economical considerations could then be chosen. To obtain the fitness function for any given configuration, it is necessary to model every flotation stage. The proposed method was used to find the optimum circuit configuration for a coal washing plant. The objective was to arrive at the highest yield while producing a concentrate with a certain ash content (< 11%). The feed to the flotation circuit was characterized based on the size fractions and their flotation rate constants. Results showed that with a 95% confidence, the absolute difference between the modeled and measured values were 2.9-5.5% for yield and 0.4-1.1% for concentrate ash content. When the proposed GA-based circuit configuration was implemented in the plant, the yield increased from the original value of 57.6% to 65.7% while producing concentrate ash content (10.9%) within acceptable limits. By adding one stage to the current three-stage circuit, it was predicted that the yield could further increase by 3.8% while keeping the quality of the concentrate within the appropriate level. Keywords: modeling, optimizing, flotation circuit configuration, genetic algorithms

Sep 1, 2012

By O. N. Mohanty, S. Mohan Rao, N. D. Rao, T. Mukherjee, P. V. T. Rao

"Chromite ore is an indispensable raw material in the manufacture of ferro-chrome and charge-chrome, which are used for the production of stainless and other alloy steels. The demand for chromite ore is ever increasing because of increasing consumption of these steels. Keeping this in view, Tata Steel is keen to recover values from fines and wastes, and also to produce value added products from their captive chromite mines and its processing plants.Tata Steel has its captive chromite resources at Sukinda, Orissa. They contain two ore types, i.e. (i) Ferruginous and (ii) Siliceous. The generation of off-grade ores is an increasing trend and simultaneously customer quality requirements are becoming ever more stringent. The ferruginous type ore also contains a considerable quantity of in-situ fines (~20% particles below 0.5 mm) that compound the beneficiation problem.In many places, in India and abroad, mined non-marketable off-grade and low grade chromite ores are upgraded by using either simple classification techniques like screw classification, hydrosizing, hydrocycloning or conventional gravity concentration processes such as Heavy media separation, Jigging, Spiraling, Tabling etc.At Tata Steel, the ferruginous type ores are treated in Chrome Ore Beneficiation (COB) Plant that comprises: a crushing and grinding circuit; a classification circuit using hydrocyclones; and a beneficiation circuit using 4 stage spirals in the coarse circuit (-0.5+0.1 mm) and 3 stage spirals & tables in the fine circuit (-0.1+0.038 mm). In this process, 3 types of tailings are being generated and together analyses about 17 % Cr2O3, which is high. From the present operation the chromite recovery is around 70% and could not produce coarse concentrates (+0.5 mm size). Whereas the siliceous type ore is treated in the Lumpy Ore Processing (LOP) plant, consisting of crushing-washing & classification-hand sorting operations, to produce marketable grade lumpy ore and –10 mm de-slimed fines. These fines are intermittently treated in the COB plant. The higher silica content (greater than 1%) and low Cr/Fe ratio (less than 2.8) are the problems with these concentrates."

Jan 1, 2003

By Jim Pae Lem

This study investigates the mode of occurrence of uranium in a copper concentrate from the Prominent Hill mine. Mineralogical and liberation studies of a high grade Cu concentrate (monthly composite) containing uranium (U) were undertaken using QEM-Scan in combination with QXRD and ICP-MS. The study aimed at determining in what form U was recovered, and by which mechanisms. The deportment of U was studied in 3 size fractions; +20µm, -20+8µm and -8µm. QEM-Scan analysis showed that uranium was present as U(Cu)-silicates, U-silicates, UPbOx/FeOx or traces of UThOx and UTiOx, with the U-silicates present across the size fractions. The association of uranium bearing minerals with copper sulphides varied across the size ranges. Interestingly, most of the U (46% by weight) was distributed in the finest fraction (-8µm), in which the deportment of Cu was low (6%). Over 40% of the U mineralisation in the -8µm was liberated. In terms of the floatation response, while recovery of the uranium minerals as a result of their association with copper sulphides (as composite particles) was evident, recovery of UPbOx locked in hydrophilic haematite in the +20µm size fraction suggests, that other mechanisms (e.g. Inadvertent activation by Pb from radioactive U decay) are possible. Furthermore, the high amount of fine liberated U bearing particles in the concentrate points at entrainment as another major mechanism for uranium recovery, and therefore, a target for process optimisation.

Sep 1, 2012

By Raquel Franco de Souza Lima, Isao Matsuoka

"Microflotation studies and abstraction experiments were conducted with synthetic oxide spinels relating to chromite (MgCr2O4, FeCr2O4, FeFe2O4 and FeAl2O4), using sodium oleate as collector. An attempt was done to correlate this data with the speciation of oleate in the bulk solution and at the interface solid-water, to explain the floatability curves. The microflotation tests were conducted using a microflotation cell. The abstraction of sodium oleate was measured at 25°C, with one gram of synthetic spinel and the abstraction time was 30 minutes. After centrifuging, the residual oleate concentration in the supernatant was measured by using the spectrophotometric method described by Mizuniwa et al. (1977), that covers the range from 1.5 to 9 ppm. To cover the range from 0.2 to 1.5 ppm, the residual oleate concentration was measured using the spectrophotometric method described by Gregory (1966). The amount of oleate abstracted was calculated from the difference between initial and residual (equilibrium) concentrations.Figure 1 shows the floatability of FeCr2O4, FeAl2O4, FeFe2O4, MgCr2O4 as a function of pH and sodium oleate concentration of 1 x 10-5 M. The IEP of each sample is indicated in the figure by a vertical line in the horizontal axis. The chromium-bearing spinels FeCr2O4 and MgCr2O4 show the lowest isoelectric points (IEP), around pH 6, while in the case of FeFe2O4 and FeAl2O4, the isoelectric points lie at pH 6.5 and 7.3, respectively. It is seen that the flotation-pH curve for FeFe2O4 has a peak at the pH of the IEP, while flotation peak for FeCr2O4 appears at pH below the IEP and that of MgCr2O4 does at pH above the PZC. On the other hand, FeAl2O4 is floated at pH range between about 4 and 7,3 (IEP). This suggests that the pH value at which the maximum flotation occurs is dependent on the sort of spinel to be floated, though it appears in the vicinity of the respective IEP."

Jan 1, 2003

By Masanori Mori, Hajime Miki, Osamu Ichikawa, Tsuyoshi Hirajima, Mitsuru Sawada, Keiko Sasaki

For pretreatment of selective flotation, surface oxidation of chalcopyrite and molybdenite was applied by oxygen plasma then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc.

Jan 1, 2014

By Qingming Feng, Dongbo An, Jinhong Zhang

The application of the geopolymerization of mine tailings as construction materials is hindered by the fact that conventional geopolymerization of mine tailings usually involves a large consumption of alkali, i.e., sodium hydroxide (NaOH), and a long curing time, because of the relatively low reactivity and the high Si/Al ratio of mine tailings when compared to other active resources such as fly ash and clay minerals. The present study is focused on efficiently activating mine tailings, reducing alkali consumption, decreasing curing time and improving compressive strength. We firstly investigate the temperature effect on the alkali activation of mine tailings during geopolymerization. Secondly, the impact of additives, i.e., calcium hydroxide and aluminium oxide, on the compressive strength of samples is studied. Thirdly, different forming pressures have been applied to remove excessive alkali and its impact on samples&apos; strength has been investigated. The results show that a 40 MPa unconfined compressive strength (UCS) can be achieved with the geopolymerization samples after mine tailings are activated by sodium hydroxide at 170°C for 1 hour with the addition of calcium hydroxide and alkali dissolved aluminium oxide, further compressed with a 10 MPa forming pressure and finally cured at 90°C for 3 days. The findings of the present work provide a novel method for the geopolymerization of mine tailings as construction materials.

Jan 1, 2014

By W. G. Liu

Phenyl malonic acid (PMA), a new chelating collector, which contains a phenyl structure and a malonic acid chelating group, has been synthesized and its collecting capabilities to calamine, hematite, quartz and hemimorphite are also studied in laboratory. From the experimental results, it can be seen that the PMA has somewhat flotation ability to calamine, hematite and quartz, while it nearly has no collecting ability to hemimorphite. With the increase of PMA concentration, the flotation recovery of calamine increases. When the dosage of PMA was 560g/t and at pH=7~9, the flotation recovery of calamine gets its maximum of 45.94%. The test results about the influence of pH on the flotation recovery of quartz show that the flotation recovery increases with the increase of pH, and the maximal flotation recovery can be gained in alkaline media. On the other hand, PMA has stronger flotation capability to hematite than to other minerals. The flotation recovery of minerals increases with increase of PMA concentration. When the dosage of PMA is 560g/t and at pH=5~7, the flotation recovery of hematite is 82.96%. Mean-while, the influence of pH on the flotation recovery of hematite was studied and test results showed that, as pH increases, the flotation recovery sharply rises until pH=4, then the increasing rate de-creases outstandingly, at pH=6 the flotation recovery reaches its maximum of 82.96% and it de-creases speedily in alkaline media. Finally, through the measurement of infrared spectroscopy and in terms of solution chemistry of collector, the flotation mechanism has been discussed. It was concluded that the adsorption of PMA on minerals surface is chemical adsorption in nature through two oxygen atoms in the polar group of phenyl malonic acid chelating with the metal ions of minerals surface to form a hexagon-cycle chelate complex: C(=O)-O-M-O-(O=)C.

Jan 1, 2014

By S. S. Indi, D. Santhiya, S. Subramanian, K. A. Natarajan

The interaction of sphalerite- and galena-adapted Bacillus polymyxa (B. polymyxa) cells with sphalerite and galena has been investigated through adsorption, electrokinetic and flotation studies. The amount of sphalerite-adapted cells adsorbed onto sphalerite and galena is found to decrease with increase in pH. On the other hand, the adsorption density of galena-adapted cells onto galena shows a feeble maximum around pH 8, and the amount adsorbed is marginally higher in the pH range of 8 . 11.5. In the case of sphalerite the amount adsorbed is higher in the pH range of 5 to 7. The adsorption density of both the adapted cells is higher for galena vis-à-vis sphalerite. Electrokinetic studies indicate significant surface chemical changes on the chosen sulphide minerals and the bacterial cells, consequent to microbe-mineral interactions. Selective flotation tests on a synthetic mixture of galena and sphalerite confirm that sphalerite could be preferentially floated from galena, using galena-adapted cells, but not with the sphalerite-adapted cells. The cells adapted to galena assay a higher polysaccharide content and are more hydrophilic, while the sphalerite-adapted cells have a higher protein content and possess greater hydrophobicity. Transmission electron microscopic studies have provided evidence in support of the differences between the cell surface characteristics of sphaleriteand galena-adapted cells. Possible mechanisms of interaction between the minerals and the bacterial cells are discussed.

Jan 1, 2003

By G. J. Mei

Separation of hematite and iron-containing silicate gangue - aegirine by Flotation using fatty acid collector and (NH4)2SiF6 depressant was investigated in this paper. The flotation tests with single minerals show Ammonium hexafluorosilicate (AHFS) is a selective depressant for aegirine in hematite flotation in weakly acidic medium, which can strongly reduce the flotation recovery of aegirine in the pH range of 4~5 while has no evident effect on the flotation of hematite. The results of flotation tests with actual ores show the separation of hematite from aegirine gangue by forth flotation was possible, and good selectivity was achieved. Chemisorptions were observed on aegirine mineral surface treated by AHFS solution by using SEM and IR spectrum measurements. On the basis of coordination chemistry, a comprehensive mechanism, which reasonably explains the selective depression of AHFS for iron-containing silicate, is also proposed.

Jan 1, 2014

By J. S. S. Allwin Ebinesar

The bioremediation of zinc was carried out using Pseudomonas alcaligenes, a Gram negative heterotroph. The parameters such as pH, bacterial cell number, initial metal concentration, and interaction time on the biosorption of zinc were studied. The maximum zinc uptake was found to be about 95% at pH 5 and biomass loading of 2.7x1010cells/mL. The biosorption isotherm for zinc exhibited Langmuirian behavior and the Gibbs free energy of biosorption was determined to be -31.2 kJ/mol, indicative of coordination of zinc with the functional groups on the bacterial surface. The adsorption kinetics followed a pseudo-second order equation. FTIR and EDAX studies confirmed the interaction of zinc with the biomass. The mechanisms of metal-microbe interactions are discussed.

Sep 1, 2012