| 1. |
- Sharma, P.K., et al.
(författare)
-
Surface chemical characterisation of Paenibacillus polymyxa before and after adaptation to sulfide minerals
- 2001
-
Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 62:1-4, s. 3-25
-
Tidskriftsartikel (refereegranskat)abstract
- A heterotroph Paenibacillus polymyxa bacteria is adapted to pyrite, chalcopyrite, galena and sphalerite minerals by repeated subculturing the bacteria in the presence of the mineral until their growth characteristics became similar to the growth in the absence of mineral. The unadapted and adapted bacterial surface have been chemically characterised by zeta-potential, contact angle, adherence to hydrocarbons and FT-IR spectroscopic studies. The surface free energies of bacteria have been calculated by following the equation of state and surface tension component approaches. The aim of the present paper is to understand the changes in surface chemical properties of bacteria during adaptation to sulfide minerals and the projected consequences in bioflotation and bioflocculation processes.The mineral-adapted cells became more hydrophilic as compared to unadapted cells. There are no significant changes in the surface charge of bacteria before and after adaptation, and all the bacteria exhibit an iso-electric point below pH 2.5. The contact angles are observed to be more reliable for hydrophobicity assessment than the adherence to hydrocarbons. The Lifschitz--van der Waals/acid--base approach to calculate surface free energy is found to be relevant for mineral--bacteria interactions. The diffuse reflectance FT-IR absorbance bands for all the bacteria are the same illustrating similar surface chemical composition. However, the intensity of the bands for unadapted and adapted cells is significantly varied and this is due to different amounts of bacterial secretions underlying different growth conditions.
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| 2. |
- Das, A., et al.
(författare)
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Surface chemical and adsorption studies using Thiobacillus ferrooxidans with reference to bacterial adhesion to sulfide minerals
- 1999
-
Ingår i: Biohydrometallurgy and the Environment toward the Mining of the 21st century. - : Elsevier. - 0444501932 ; , s. 697-707
-
Konferensbidrag (refereegranskat)abstract
- Adhesion of Thiobacillus ferrooxidans to pyrite and chalcopyrite in relation to its importance in bioleaching and bioflotation has been studied. Electrokinetic studies as well as FT-IR spectra suggest that the surface chemistry of Thiobacillus ferrooxidans depends on bacterial growth conditions. Sulfur-,Pyrite- and chalcopyrite-grown Thiobacillus ferrooxidans were found to be relatively more hydrophobic. The altered surface chemistry of Thiobacillus ferrooxidans was due to secretion of newer and specific proteinaceous compounds. The adsorption density corresponds to a monolayer coverage in a horizontal orientation of the cells. The xanthate flotation of pyrite in presence of Thiobacillus ferrooxidans is strongly depressed where as the cells have insignificant effect on chalcopyrite flotation. This study demonstrate that:(a)Thiobacillus ferrooxidans cells can be used for selective flotation of chalcopyrite from pyrite and importantly at natural pH values.(b)Sulfur-grown cells exhibits higher leaching kinetics than ferrous ion-grown cells.
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| 3. |
- Karlkvist, Tommy, et al.
(författare)
-
Molecular recognition in mineral flotation : Selectivity in apatite-calcite system
- 2014
-
Ingår i: 27th International Mineral Processing Congress, IMPC 2014, Santiago, Chile, 20-24 October 2014.
-
Konferensbidrag (refereegranskat)abstract
- The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ζ potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ζ potential and infra-red spectroscopy data.
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| 4. |
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| 5. |
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| 6. |
- Abdel-Khalek, N.A., et al.
(författare)
-
Effect of starch type on selectivity of cationic flotation of iron ore
- 2012
-
Ingår i: Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 121:2, s. 98-102
-
Tidskriftsartikel (refereegranskat)abstract
- Cationic flotation is one of the most widely accepted technologies for upgrading siliceous iron ore using polysaccharides (mainly starches) as depressing agents for iron bearing minerals while floating silica with amines. In this paper, a group of starches are investigated as depressants for haematite. These starches are wheat, corn, rice, potato and dextrin. The role of starch type on the selectivity of the separation process has been studied through zeta potential, adsorption measurements as well as flotation tests. The effects of type of starch and pH of the medium have been studied. The results indicate that the selectivity of the separation process is strongly affected by the type of starch used, where better results are obtained with corn starch or wheat starch in comparison to the other types. Fourier transform infrared spectroscopy measurements indicated that the interaction between starches and haematite surface is intermolecular interaction.
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| 7. |
- Deo, N., et al.
(författare)
-
Biodegradation of some organic reagents from mineral process effluents
- 1999
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Ingår i: Biohydrometallurgy and the Environment toward the Mining of the 21st century. - : Elsevier. - 0444501932 ; , s. 687-696
-
Konferensbidrag (refereegranskat)abstract
- The utility of a soil microbe, namely Bacillus polymyxa, in the removal of organic reagents such as dodecylamine, ether diamine, isopropyl xanthate and sodium oleate from aqueous solutions is demonstrated. Time-bound removal of the above organic reagents from an alkaline solution was investigated under different experimental conditions during bacterial growth and in the presence of metabolites by frequent monitoring of residual concentrations as a function of time, reagent concentration and cell density. The stages and mechanisms in the biodegradation process were monitored through UV-visible and FTIR spectroscopy. Surface chemistry of the bacterial cells as well as the biosorption tendency for various organics were also established through electrokinetic and adsorption density measurements. Both the cationic amines were found to be biosorbed followed by their degradation through bacterial metabolism. The presence of the organic reagents promoted bacterial growth through effective bacterial utilization of nitrogen and carbon from the organics. Under optimal conditions, complete degradation and bioremoval of all the organics could be achieved
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| 8. |
- Kundu, T.K., et al.
(författare)
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Atomistic simulation of the surface structure of wollastonite and adsorption phenomena relevant to flotation
- 2003
-
Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 72:1, s. 111-127
-
Tidskriftsartikel (refereegranskat)abstract
- Atomistic simulation techniques have been used to calculate the surface structure and stability of wollastonite crystal and its adsorption behaviour in the presence of molecular and dissociated water, and two widely used collector head group molecules of methanoic acid and methylamine. Seven predominant surfaces have been modelled and their calculated surface energies correspond well with their preferred morphological domination. Surfaces are identified having fourfold and threefold coordination of surface silicon. Threefold surface silicon are stabilized by addition of hydroxyl ion on them and proton on surface oxygen. Stable surfaces thus obtained are subjected to surface Ca2+ replacement by 2H+ by transforming 2O2− to 2OH−. Surface energy and reaction energy values indicate wollastonite surface stabilized to a great extent by adsorbing water in dissociated form. The Ca2+ replacement from the first few layers of the surface is energetically more favourable in acidic condition. Three Miller indexed surfaces terminating with fully coordinated silicon were reconstructed to make the surface free of lone oxygen, and these surface cuts were chosen to carry out simulation work for adsorption of molecules. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules but the presence of methylamine decreases surface energy to lowest values. Adsorption of dissociated water is preferred by {100} and {102} surfaces, while {001} surface adsorbs methylamine strongly as the results show highly negative adsorption energies. In terms of pure molecule adsorption, the preferred adsorption sequence for all the surfaces is methylamine>methanoic acid>water. For {100} and {102} predominant surfaces, the difference in adsorption energy values is not much and we conclude that the collectors having long-chain hydrophobic alkyl chain, the two head group molecules considered, cannot render enough hydrophobicity due to inadequate adsorption on wollastonite. Thus the presence of activators/modifiers in actual wollastonite flotation practice is substantiated.
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| 9. |
- Manouchehri, Hamid-Reza, et al.
(författare)
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Review of electrical separation methods : Part 1: Fundamental aspects
- 2000
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Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 17:1, s. 23-36
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Tidskriftsartikel (refereegranskat)abstract
- The fundamentals of electrical separation, the electrical properties of minerals, the principal methods used for charging minerals and their mechanisms, the effective factors controlling the acquisition of charges by minerals, the general configuration of commercial electric separators and the forces operating during electrical separation of minerals are reviewed and presented.
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| 10. |
- Manouchehri, Hamid-Reza, et al.
(författare)
-
Review of electrical separation methods : Part 2: Practical considerations
- 2000
-
Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 17:3, s. 139-166
-
Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the practical considerations of the various electrical separation methods used in mineral processing. The effective factors related to mineral characteristics and equipment attributes are described and analyzed with reference to conventional industrial applications of the electrical methods. Some new aspects of electrical methods application and their potential for mineral beneficiation, apart from the mineral systems that have been successfully beneficiated, are also presented. In addition, wet dielectric separation, which now appears to be promising, is briefly cited.
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| 11. |
- P.K., Sharma, et al.
(författare)
-
Surface characterization of Acidithiobacillus ferrooxidans cells grown under different conditions
- 2003
-
Ingår i: Hydrometallurgy. - 0304-386X .- 1879-1158. ; 71:1-2, s. 285-292
-
Tidskriftsartikel (refereegranskat)abstract
- The growth characteristics of a strain of Acidithiobacillus ferrooxidans isolated from mine water with ferrous ion, sulfur, or pyrite mineral as sole source of energy have been established. The electrokinetic behaviour of the bacterial cells was investigated and the cell surface groups were characterized by diffuse reflectance FT-IR and FT-Raman spectroscopies. The surface charge on the iron-grown cells (i.e.p., pH 2.0) is different from that on the solid-substrate-grown cells (i.e.p., pH 3.0-3.5) and the surface charge depends on the growth history of the bacteria. The FT-IR and FT-Raman spectra revealed a higher amount of protein content on the surface of the sulfur- and pyrite-grown cells compared to the iron-grown cells. These results suggest that the altered surface charge on the cells is due to differences in the protein content synthesized by bacteria exposed to different growth conditions.
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| 12. |
- Rao, K. Hanumantha, et al.
(författare)
-
Environmental aspects of iron ore processing
- 2003
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Ingår i: International Seminar on Mineral Processing Technology. - New Dehli : Allied Publishers Ltd. - 817764405X ; , s. 32-34
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Konferensbidrag (refereegranskat)
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| 13. |
- Rao, K. Hanumantha, et al.
(författare)
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Flotation of mica minerals and selectivity between muscovite and biotite while using mixed anionic/cationic collectors
- 1990
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Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 7:3, s. 127-132
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Tidskriftsartikel (refereegranskat)abstract
- Selective flotation of muscovite from a material containing muscovite (15.4%), biotite (13%), and siliceous gangue (quartz and feldspar), using a mixed collector system of sodium oleate and dodecylamine acetate has been described. Muscovite is found to float in preference to biotite, when the pulp is initially conditioned with oleate followed by amine at basic pH values. The results indicate that a product containing 63% muscovite with a recovery of 93% can be obtained, while using 75-150 g/t of oleate and 96 g/t of amine. The biotite grade and recovery are found to be around 30% and 20%, respectively. A good selectivity between muscovite and siliceous gangue is obtained. A final product containing 95% muscovite with an overall recovery of 75% is obtained when the flotation concentrate is subjected to magnetic separation. These studies indicate the possibility of separating muscovite from biotite by using a mixture of collectors.
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| 14. |
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| 15. |
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| 16. |
- Rao, K. Hanumantha, et al.
(författare)
-
Selective flocculation for the recovery of iron in Kudremukh tailings
- 1985
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Ingår i: Mining engineering. - 0026-5187. ; 37:11, s. 1312-1315
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Tidskriftsartikel (refereegranskat)abstract
- A concentrate containing 63% iron can be obtained from tailings containing 34% iron with around 60% recovery. Caustic degraded tapioca starch is an effective agent for selective flocculation. While potato starch after caustic degradation can also be used, neither the parent starch nor the amylopectin compound is as effective.
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| 17. |
- Santhiya, D., et al.
(författare)
-
Bio-modulation of galena and sphalerite surfaces using Thiobacillus thiooxidans
- 2001
-
Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 62:1-4, s. 121-141
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of Thiobacillus thiooxidans (T. thiooxidans) with sphalerite and galena has been investigated through adsorption, electrokinetic, and flotation studies. The amount of T. thiooxidans cells adsorbed onto galena and sphalerite is found to be almost independent of pH. However, a greater amount of cells is adsorbed onto galena compared to sphalerite. The adsorption isotherms of T. thiooxidans onto both galena and sphalerite exhibit Langmuirian behaviour. Electrokinetic measurements reveal that the isoelectric points (iep) of galena and sphalerite are located around pH 2, while that of T. thiooxidans is around pH 3. The isoelectric points of the minerals are shifted to higher pH values after interaction, consequent to bacterial cell attachment, indicating specific adsorption. Additionally, the electrophoretic mobilities are found to become less negative as a function of time after bacterial interaction. Such a trend is also followed in the case of the cells after interaction with the minerals for different time intervals. On a comparative basis, the cells after interaction with sphalerite are less negative vis-à-vis those after interaction with galena. The flotation recovery of sphalerite, beyond 1 h of interaction with T. thiooxidans cells is not affected but galena is totally depressed in the presence of T. thiooxidans cells, in the pH range 5-11. The differential flotation tests on a synthetic mixture of galena and sphalerite reveal that sphalerite can be selectively floated from galena in the presence of T. thiooxidans.
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| 18. |
- Sharma, P.K., et al.
(författare)
-
Adhesion of Paenibacillus polymyxa on chalcopyrite and pyrite : Surface thermodynamics and extended DLVO theory
- 2003
-
Ingår i: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 29:1, s. 21-38
-
Tidskriftsartikel (refereegranskat)abstract
- The adhesion behaviour of Paenibacillus polymyxa bacteria on pyrite and chalcopyrite is examined by the surface thermodynamics and the extended DLVO theory approaches. In addition, the bacteria are adapted to pyrite and chalcopyrite minerals, and the adhesion behaviour of these bacteria is also investigated. The significance of acid-base interactions in adhesion is assessed. The essential parameters needed for the calculations of interaction energy between bacteria and mineral are experimentally determined. The results illustrate that the bacterial surfaces are more energetic than the mineral surfaces and the bacteria acquired acid-base surface energy component during their adaptation to mineral. The extended DLVO approach is found to be more effective in predicting the adhesion behaviour than the expectations from thermodynamic approach. The thermodynamic approach yields no bacterial adhesion on minerals and this discrepancy is the result of inadequate description of electrostatic interactions. The adhesion predictions by the DLVO approach are able to partially explain the bioflotation results of pyrite and chalcopyrite. Extended DLVO shows that on account of high bacterial surface energy, their aggregation is not feasible. But due to the hydrophobicity of pyrite and chalcopyrite, their aggregation is possible.
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| 19. |
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| 20. |
- Sharma, P.K., et al.
(författare)
-
Analysis of different approaches for evaluation of surface energy of microbial cells by contact angle goniometry
- 2002
-
Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 98:3, s. 341-463
-
Tidskriftsartikel (refereegranskat)abstract
- Microbial adhesion on solid substrate is important in various fields of science. Mineral–microbe interactions alter the surface chemistry of the minerals and the adhesion of the bacterial cells to mineral surface is a prerequisite in several biobeneficiation processes. Apart from the surface charge and hydrophobic or hydrophilic character of the bacterial cells, the surface energy is a very important parameter influencing their adhesion on solid surfaces. There were many thermodynamic approaches in the literature to evaluate the cells surface energy. Although contact angle measurements with different liquids with known surface tension forms the basis in the calculation of the value of surface energy of solids, the results are different depending on the approach followed. In the present study, the surface energy of 140 bacterial and seven yeast cell surfaces has been studied following Fowkes, Equation of state, Geometric mean and Lifshitz–van der Waals acid–base (LW–AB) approaches. Two independent issues were addressed separately in our analysis. At first, the surface energy and the different components of the surface energy for microbial cells surface are examined. Secondly, the different approaches are evaluated for their internal consistency, similarities and dissimilarities. The Lifshitz–van der Waals component of surface energy for most of the microbial cells is realised to be approximately 40 mJ/m2±10%. Equation of state and Geometric mean approaches do not possess any internal consistency and yield different results. The internal consistency of the LW–AB approach could be checked only by varying the apolar liquid and it evaluates coherent surface energy parameters by doing so. The electron-donor surface energy component remains exactly the same with the change of apolar liquid. This parameter could differentiate between the Gram-positive and Gram-negative bacterial cells. Gram-negative bacterial cells having higher electron-donor parameter had lower nitrogen, oxygen and phosphorous content on their cell surfaces. Among the four approaches, LW–AB was found to give the most consistent results. This approach provides more detailed information about the microbial cell surface and the electron–donor parameter differentiates different type of cell surfaces.
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| 21. |
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| 22. |
- Sharma, P.K., et al.
(författare)
-
Role of a heterotrophic Paenibacillus polymyxa bacteria in the bioflotation of some sulfide minerals
- 1999
-
Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 16:4, s. 35-41
-
Tidskriftsartikel (refereegranskat)abstract
- A pure strain of Paenibacillus polymyxa and mineral-adapted strains are used to bring about surface chemical changes on pyrite and chalcopyrite and, thus, their flotation. Paenibacillus polymyxa was adapted by repeated subculturing in the presence of pyrite and chalcopyrite. The surface chemical changes of bacteria due to adaptation and of minerals after their interaction with bacterial cultures are evaluated by electrokinetic and infrared spectroscopy and are discussed with reference to their flotation responses. Interaction of bacterial cells, bacterial metabolites and whole bacterial cultures affected the Hallimond flotation behavior of the sulfide minerals. The Xanthate flotation results show that pyrite, but not chalcopyrite, is depressed when the tests are carried out after interaction with chalcopyrite-adapted Paenibacillus polymyxa. This investigation demonstrated that the surface chemical properties of bacteria can be manipulated successfully to achieve the desired effects in the flotation process.
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| 23. |
- Sharma, P. K., et al.
(författare)
-
Surface characterization of bacterial cells relevant to the mineral industry
- 2005
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Ingår i: Mining, Metallurgy & Exploration. - 2524-3462 .- 2524-3470. ; 22:1, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria belonging to the Acidithiobacilli group are widely used in the mineral processing industry in bioleaching and biobeneficiation operations. Paenibacillus polymyxa has also found application in biobeneficiation studies. Microbial adhesion to mineral surface is an essential step for both biobeneficiation and bioleaching. Microbial adhesion depends on the physico-chemical characteristics of both the mineral and microbe. In the present study, physico-chemical characterization of the surface of iron-oxidizing bacteria grown with Fe ions and elemental S, Acidithiobacillus thiooxidans and Paenibacillus polymyxa were carried out. Surface hydrophobicity was evaluated using microbial adhesion-to-solvents test, contact angle measurement and surface energy evaluation. The surface composition of the bacterial cell surfaces was determined using X-ray photoelectron spectroscopy (XPS) and diffused reflectance infrared Fourier transform (DRIFT) spectroscopy.
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| 24. |
- Sharma, P.K., et al.
(författare)
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Thiobacillus ferrooxidans interaction with sulfide minerals and selective chalcopyrite flotation from pyrite
- 1999
-
Ingår i: Advances in flotation technology. - : Society for Mining, Metalurgy and Exploration. - 0873351843 ; , s. 147-165
-
Konferensbidrag (refereegranskat)abstract
- The acidophilic and chemolithotrophic Thiobacillus ferrooxidans bacteria grown in the presence of soluble ferrous ions and solid substrates (sulfur, pyrite and chalcopyrite) as their energy source have been used in the investigations. The cell surfaces are characterized by zeta-potential, contact angle, FT-IR and FT-Raman studies. The adsorption isotherms of the cells on pyrite and chalcopyrite indicate that the adsorption begins on pyrite at a much lower equilibrium cell population than on chalcopyrite. The isotherms tend to level off at a cell adsorption density corresponding to a horizontal monolayer coverage when the geometrical dimensions of the cells are considered. In the presence of cells, the xanthate flotation of pyrite completely depressed, whereas chalcopyrite flotation is unaffected. The results suggest that chalcopyrite can be selectively floated from pyrite, also at a neutral pH region, in the presence of T. ferrooxidans cells
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| 25. |
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| 26. |
- Su, Fenwei, et al.
(författare)
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Dephosphorization of magnetite fines - Part 1: Evaluation of flotation kinetic models
- 1998
-
Ingår i: Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 107:SEPT/DEC, s. C95-C102
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Forskningsöversikt (refereegranskat)abstract
- Dephosphorization of magnetite fines by flotation in such a way as to minimize the fatty acid coating left on the magnetite surfaces is the principal technical challenge facing the mineral processing division of LKAB, Sweden. Modelling of flotation kinetics enables the influence of chemical and operational variables on apatite flotation from magnetite fines to be predicted. Five typical first-order flotation kinetic models are evaluated by statistical techniques, after an estimation of model parameters by a nonlinear least-squares fitting program, with use of the authors' own results and results taken from the literature. Evaluation of the models is based on two aspects: goodness of fit to the experimental results and suitability to describe the flotation behaviour. The first-order models with a rectangular distribution of floatabilities and with fast and slow floating components (F-S model) gave an excellent fit to the experimental results of apatite flotation when compared with the other models, the latter being superior not only in the goodness of fit to apatite flotation and other mineral flotation results but also in its description of flotation behaviour. The kinetic parameters (percentage recoveries and rate constants of fast and slow floating particles) in the F-S model have a physical significance and can thus be used for qualitative as well as quantitative interpretation of flotation performance. The influence of collector dose can be effectively included in the F-S model by making realistic simplifications and relating the collector dose to the fraction of slow floating particles. The ratio of fast and slow rate constants can be used to describe the selectivity of apatite flotation from magnetite.
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| 27. |
- Su, Fenwei, et al.
(författare)
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The influence of temperature on the kinetics of apatite flotation from magnetite fines
- 1998
-
Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 54:3, s. 131-145
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of pulp temperature on the kinetics of apatite flotation from magnetite fines was studied using Atrac (fatty acid type) as collector and sodium silicate as dispersant at pH 8.5–9.0. The batch flotation tests were conducted in a specially designed temperature controlled flotation cell. A modified first-order model, incorporating two rate terms describing fast and slow-floating components, was applied to evaluate the flotation kinetics. The estimation of the model parameters was made by a non-linear least squares fitter program which is based on the Levenberg–Marquardt algorithm. Results indicate that increasing temperature from 10°C to 40°C decreases the phosphorous content in magnetite concentrate but with a simultaneous loss of magnetite recovery. At temperatures below 30°C, an increase in pulp temperature results increasing flotation rate of fast-floating particles and has a marginal effect on slow-floating particles. Above 30°C, the flotation rate of fast-floating particles decreases with increasing pulp temperature. Sodium silicate has a positive effect for increasing the phosphorous recovery and decreasing the phosphorous content in the magnetite concentrate at 20°C for all the levels of collector dosages. In the absence of sodium silicate, collector is active for both apatite and magnetite flotation. The higher selectivity between apatite and magnetite with an acceptable content of phosphorous in the magnetite concentrate is obtained at a moderate dosage of about 400 g/t sodium silicate. The optimum flotation conditions are: 50 g/t collector dosage, 350–400 g/t dispersant dosage, pH 8.5–9 and pulp temperature 25–30°C.
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| 28. |
- T.C., Rao, et al.
(författare)
-
Characteristic curve for the coal-oil agglomeration process
- 1982
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 9:3, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were carried out on coal fines of two different washeries, at different periods of agglomeration, to determine the size distribution of agglomerates with changes in feed size, pulp density and furnace oil dosage. It is found that the size distribution of the agglomerates follows a self-preserving growth. This behaviour has been generalised using a reduced dimensionless size axis to obtain a characteristic curve. It is shown that this curve is affected only by the nature of the feed and not by the process variables. An equation has been suggested to quantify this characteristic curve of the oil agglomeration process.
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| 29. |
- T.C., Rao, et al.
(författare)
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Studies on the treatment of coal fines by oil-agglomeration process
- 1982
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Ingår i: Transactions Society of Mining Engineers of AIME. - 0895204150 ; , s. 1966-1970
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The effects of important variables such as pulp density, feed size, furnace oil dosage, degree of agitation, and time of agglomeration on the yield and ash content of the agglomerates obtained from the oil agglomeration of coal fines have been studied in a laboratory batch agglomeration cell. Optimum conditions for maximum yield and throughput have been discussed. The furnace oil dosage and pulp density were found to have more influence on the yield and grade of the agglomerates than the degree of agitation and feed size in the ranges studied.
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| 30. |
- Alexandrova, L., et al.
(författare)
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Thin film studies in mixed cationic-anionic surfactant system
- 2003
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Ingår i: Proceedings of the XXII International Mineral Processing Congress. - Marshalltown, South Africa : South African Institute of Mining and Metallurgy. - 0958460922 ; , s. 838-846
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Konferensbidrag (refereegranskat)
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| 31. |
- Alexandrova, L, et al.
(författare)
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Three-phase contact parameters measurements for silica-mixed cationic-anionic surfactant systems
- 2009
-
Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 348:1-3, s. 228-233
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Tidskriftsartikel (refereegranskat)abstract
- The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [D. Platikanov, J. Phys. Chem. 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants heterocoagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces.
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| 32. |
- Chernyschova, Irina V., et al.
(författare)
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Mechanism of adsorption of long-chain alkylamines on silicates : a spectroscopic study. 2. Albite
- 2001
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:3, s. 775-785
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Tidskriftsartikel (refereegranskat)abstract
- Using FTIR (DRIFTS and IRRAS) and XPS spectroscopy, ζ potential measurements, and Hallimond flotation tests, we confirmed that long-chain primary amines are adsorbed on silicates at pH 6-7 through the 2D-3D precipitation mechanism. The orientation and packing of dodecyl- and hexadecylammonium acetate and chloride adsorbed on albite in the different regions of the adsorption isotherm were determined. It was shown that these characteristics depend strongly on the substrate. Coadsorption of the counterion was not revealed, but the counterion was found to affect indirectly the adsorption at concentrations above the concentration of the bulk amine precipitation
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| 33. |
- Chernyshova, Irina V., et al.
(författare)
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A new approach to the IR spectroscopic study of molecular orientation and packing in adsorbed monolayers : orientation and packing of long-chain primary amines and alcohols on quartz
- 2001
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 105:4, s. 810-820
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Tidskriftsartikel (refereegranskat)abstract
- A new method is suggested for determining the molecular orientation in adsorbed films with uniaxial and biaxial anisotropy from two (s- and p-polarized) IRRAS spectra of the same sample, measured at the optimal angle of incidence. The method is simple, does not use the film thickness, and is internally stable with respect to the uncertainty in the input optical parameters of the anisotropic film. The advantages and limitations of the method are discussed. To validate the method, we determined the orientation of hexadecylamine and hexadecyl alcohol adsorbed on a quartz surface. It is shown that at a concentration above the concentration of 2D precipitation but below the concentration of 3D precipitation, hydrocarbon chains in the adsorbed amine monolayer are well-packed in a monoclinic (biaxial) subcell with a tilt angle of about 30°. Chaotically arranged crystallites of the amine molecules appear at the surface at a concentration higher than the concentration of 3D precipitation. Adsorbed monolayers of the alcohol turn out to have a hexagonal structure, in which the hydrocarbon tails are "flip-flop" positioned and tilted by 25-30° from the surface normal.
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| 34. |
- Chernyshova, Irina V., et al.
(författare)
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Mechanism of coadsorption of long-chain alkylamines and alcohols on silicates. Fourier transform spectroscopy and X-ray photoelectron spectroscopy studies
- 2001
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:9, s. 2711-2719
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Tidskriftsartikel (refereegranskat)abstract
- Coadsorption of long-chain primary amines and alcohols on silicates (quartz and albite) at pH 6-7 was studied using Fourier transform (DRIFTS and IRRAS) and X-ray photoelectron spectroscopy. The ionization state of the amino headgroups, the molecular orientation, and packing in the adsorbed mixed monolayers were determined. The results were interpreted in terms of the modified model of 2D-3D precipitation, where the elementary adsorbing species from the solution is the amine-alcohol-water association.
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| 35. |
- Chernysova, Irina V., et al.
(författare)
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Mechanism of adsorption of long-chain alkylamines on silicates. A spectroscopic study. 1. Quartz
- 2000
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:21, s. 8071-8084
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with ζ potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, ζ potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.
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| 36. |
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| 37. |
- de Leeuw, N.H., et al.
(författare)
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Modeling the competitive adsorption of water and methanoic acid on calcite and fluorite surfaces
- 1998
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 14:20, s. 5900-5906
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Tidskriftsartikel (refereegranskat)abstract
- Atomistic simulation techniques were used to investigate the interaction between the minerals calcite and fluorite with water and methanoic acid. The relative adsorption energies suggest that methanoic acid preferentially adsorbs onto fluorite surfaces, while adsorption of water is energetically preferred over methanoic acid on the calcite cleavage plane in agreement with experiment. The coverage and configuration of adsorbed methanoic acid on the surfaces depends largely on lattice spacing between the cations, and bridging between surface calcium atoms is highly favored. These findings have given an insight into interactions at the atomic level which indicate that modeling techniques should be capable of predicting adsorption behavior and designing collector molecules, which is of central importance to the mineral processing technique of flotation
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| 38. |
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| 39. |
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| 40. |
- Dwari, Ranjan, et al.
(författare)
-
Characterisation of particle tribo-charging and electron transfer with reference to electrostatic dry coal cleaning
- 2009
-
Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 91:3-4, s. 100-110
-
Tidskriftsartikel (refereegranskat)abstract
- The electrostatic beneficiation of coal is based on different tribo-charging characteristics of ash forming minerals and coal particles. In this work the tribo-charging of quartz and coal particles contacted with various metals and polymer materials have been measured and the charge acquisition was examined through surface energy calculations from liquid contact angle data. The contacts angles, before and after tribo-charging of solids, were measured with Krüss tensiometer using Washburn's equation where the sample holders in tensiometer are specially constructed with tribo-charger materials. The polarity and amount of charge acquired by quartz and carbon powders with metal tribo-chargers were found to be in good agreement with the reported work functions of the contacting surfaces. The results for the charge with polymer materials differed from the work function values, presumably due to surface contamination. The surface energy of quartz particles calculated from the measured contact angle data showed that the tribo-charging increases the surface energy. Both polar and non-polar components computed using Fowkes and Owens-Wendt approaches showed that these components increase after tribo-electrification. However, the polar component divided into acid and base parts, as in van Oss approach, manifest decreasing acid part and increasing base part. Since quartz charged negatively during tribo-charging with metal surfaces and therefore suggests acceptance of electrons, the determined acid-base surface energy components are consistent with the charge transfer process. The results also elucidate an explicit correlation between the charge generated by powders and the surface acceptor (acid) and donor (base) electronic state and thereby the work functions. Thus a method for characterising the changes in surface energetic structure of solids during tribo-electrification in terms of acid-base parameters of electron transfer between the contacting surfaces has been described for the first time.
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| 41. |
- Dwari, Ranjan, et al.
(författare)
-
Characterising electron transfer mechanism in tribo-electrification of pyrite through contact angle measurements
- 2008
-
Ingår i: Open Mineral Processing Journal. - : Bentham Science Publishers Ltd.. - 1874-8414. ; 1, s. 6-17
-
Tidskriftsartikel (refereegranskat)abstract
- Coal beneficiation by tribo-electrostatic method depends on tribo-charging attributes of coal and ash forming minerals. The tribo-electrification behaviour of pyrite mineral contacted with different materials has been investigated through charge measurements and the charge acquisition is probed through surface energy calculations from liquid contact angle data. Liquid contact angle on pyrite powder after tribo-electrification is determined by Kruss tensiometer using Washburn's equation. The sample holder in tensiometer is specially fabricated with different materials serving the purpose of tribo-electrification and contact angle measurement. The acid and base parameters of pyrite surface determined with van Oss acid-base approach using liquid contact angle data after tribo-electrification with different materials revealed the charging phenomena and electron transfer mechanism. The results showed an explicit correlation between the charge generated by pyrite powder and surface acceptor (acid)-donor (base) electronic state underlying the work functions of contacting surfaces. Thus a method for characterising the changes in surface energetic structure of solids during contact electrification in terms of surface acid-base parameters has been illustrated for the first time.
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| 42. |
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| 43. |
- Dwari, Ranjan, et al.
(författare)
-
Dry beneficiation of coal : a review
- 2007
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Ingår i: Mineral Processing and Extractive Metallurgy Review. - : Informa UK Limited. - 0882-7508 .- 1547-7401. ; 28:3, s. 177-234
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Coal continues to play a major role in the economic development of a country, especially in metallurgical industries and conventional power generation plants. For effective utilization of high ash coals, it is necessary to beneficiate them. The wet beneficiation process for coal cleaning is currently the predominant method of purification of coal in the world. However, dry beneficiation of coal has obvious advantages over wet processes. The dry processes for coal are based on the physical properties of coal and its associated mineral matters. Different types of equipment for dry beneficiation have been developed, based on the exploitation of physical properties such as density, size, shape, magnetic susceptibility, and electrical conductivity. This article presents a summary assessment of different technologies and their performance in the beneficiation process of high ash coals with particular reference to Indian thermal coals. The literature on sorting, air jigs, magnetic separation, air-dense medium fluidized bed separation, and electrostatic separation is summarized and discussed
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| 44. |
- Dwari, Ranjan, et al.
(författare)
-
Fine coal preparation using novel tribo-electrostatic separator
- 2009
-
Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 22:2, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of tribo-electric coal/ash cleaning is carried out with a newly built cylindrical fluidised bed tribo-charger with internal baffles, made up of copper metal. The charge transfer in coal maceral and mineral particles after repeated contact with copper plate tribo-charger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge generated during tribo-electrification is discussed with respect to gas flow rate and residence time in fluidised bed tribo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with -300 μm size fraction of coal containing 43% ash showed that the ash content can be reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.
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| 45. |
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| 46. |
- Dwari, Ranjan, et al.
(författare)
-
Non-coking coal preparation by novel tribo-electrostatic method
- 2008
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 87:17-18, s. 3562-3571
-
Tidskriftsartikel (refereegranskat)abstract
- A new laboratory fluidised bed tribo-electrostatic separator has been assembled and the beneficiation potential of thermal non-coking coal from Hingula block of Talcher coal field, India, is examined on this separator. The uniqueness of the separator originates from the efficient tribo-electrification of coal material in the cylindrical fluidised bed with internal baffle system. The collecting bins of the material underneath the copper plate electrodes are designed to function as Faraday cups such that the charge polarity and magnitude of particles in each bin can be measured directly. The liberation attributes of coal material is assessed by sink and float analysis of various size fractions. The mineral and maceral composition is determined by XRD and petrographic analysis. The separation tests were conducted at different tribo-charging and applied voltage conditions. The material collected in bins close to positive and negative electrodes show an ash content of 61% and 8% respectively, illustrating differential charge acquisition of mineral rich and coal rich particles during tribo-electrification. The charge results are in good agreement with the ash content of the coal material collected in the bins. The results showed that a clean coal of about 15% ash can be obtained from a coal containing 30% ash with about 70% yield. A better separation results can be achieved by recycling the material. The ash content in the clean coal is however limited by the liberation characteristics of the coal, which is evidenced by the SEM analysis of the particles in different bins. Thus, the tribo-electrostatic method observed to be a promising dry coal preparation technique.
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| 47. |
- Dwari, Ranjan, et al.
(författare)
-
Novel fluidised-bed tribo-electrostatic separator for dry coal preparation
- 2008
-
Ingår i: Conference in Minerals Engineering 2008. - Luleå : Luleå tekniska universitet. ; , s. 15-29
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of triboelectric coal/ash cleaning is carried out with a newly built cylindrical fluidised-bed tribocharger with internal baffles, all made up of copper metal. The charge transfer of coal maceral and mineral particles upon contacts with copper plate of tribocharger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge is discussed with respect to gas flow rate and residence time in fluidised-bed trobo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with minus 300 μm size fraction of coal containing 43% ash showed that the ash content is reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.
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| 48. |
- Dwari, Ranjan, et al.
(författare)
-
Tribo-electrostatic behaviour of high ash non-coking Indian thermal coal
- 2006
-
Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 81:2, s. 93-104
-
Tidskriftsartikel (refereegranskat)abstract
- The tribo-electrostatic method was applied to beneficiate non-coking Indian thermal coal from Ramagundam coal mines containing nearly 45% ash content. The microscopic studies revealed that quartz and kaolinite are the dominant minerals whereas illite, goethite, siderite and pyrite are the minor inclusions in the coal. Contact electrification of ash-forming minerals and coal matter was carried out using different tribo-charger materials of Al, Cu, brass, perspex and teflon. The Cu tribo-charger was found to be optimum to acquire differential charge between ash-forming inorganics and coal matter. The temperature effect on the magnitude of contact charge acquisition was found to be significant. Tests on a laboratory in-house built tribo-electrostatic free-fall separator with minus 300 μm coal showed that the ash content was reduced from 45% to about 18%, and a clean coal product as judged by the washability studies can be obtained. The results illustrate that the non-coking coals can be beneficiated using the scientific knowledge on the response and behaviour of coal and non-coal matters to electric charges.
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| 49. |
- F., Su, et al.
(författare)
-
Computer estimation of flotation kinetic model parameters
- 1998
-
Ingår i: 2Papers presented at the APCOM '98 conference, organized by the Institution of Mining and Metallurgy and held in London, United Kingdom from 19 to 23 April, 1998. - London : The Institution of Mining and Metallurgy. - 1870706366 ; , s. 513-524
-
Konferensbidrag (refereegranskat)abstract
- The effect of chemical variables on the kinetic parameters of apatite flotation from magnetite has been investigated. The two common first-order kinetic models reported in the literature, i.e., the model with rectangular distribution of floatabilities and the model with fast and slow-floating components (F-S model) have been applied in the evaluation of flotation results. The models are evaluated by fitting the flotation results from batch flotation tests. The results although indicate that both models describe the apatite flotation kinetics well in a wide range of kinetic parameters, the F-S model is found to be better in the goodness of fit to the results from every flotation test and also to describe the flotation performance adequately. The kinetic parameters of the F-S model are varied with a change in chemical variables. In particular, the rate constants ratio Kf/Ks is found to be an important parameter for achieving selectivity between apatite and magnetite, and the effect of reagents dosages on the ratio is discussed. The effect of particle size on the apatite flotation kinetics is also illustrated by analysing the froth products at each flotation time in different size classes.
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| 50. |
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