| 1. |
- Sharma, P.K., et al.
(författare)
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Surface chemical characterisation of Paenibacillus polymyxa before and after adaptation to sulfide minerals
- 2001
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 62:1-4, s. 3-25
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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
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Ingår i: Biohydrometallurgy and the Environment toward the Mining of the 21st century. - : Elsevier. - 0444501932 ; , s. 697-707
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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)
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Molecular recognition in mineral flotation : Selectivity in apatite-calcite system
- 2014
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Ingår i: 27th International Mineral Processing Congress, IMPC 2014, Santiago, Chile, 20-24 October 2014.
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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)
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Effect of starch type on selectivity of cationic flotation of iron ore
- 2012
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Ingår i: Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 121:2, s. 98-102
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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)
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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
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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
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 72:1, s. 111-127
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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)
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Review of electrical separation methods : Part 2: Practical considerations
- 2000
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Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 17:3, s. 139-166
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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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