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Sökning: WFRF:(Kota Hanumantha Rao) > (2010-2013) > (2011)

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1.
  • Alexandrova, L., et al. (författare)
  • The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems
  • 2011
  • Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 373:1-3, s. 145-151
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation of thin wetting films on silica surface from aqueous solution of a) tetradecyltrimetilammonium bromide (C14TAB) and (b) surfactant mixture of the cationic C14TAB with the anionic sodium alkyl- (straight chain C12-, C14- and C16-) sulfonates, was studied using the microscopic thin wetting film method developed by Platikanov. Film lifetimes, three-phase contact (TPC) expansion rates, receding contact angles and surface tension were measured. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetimes, as compared to the pure C14TAB. This behavior was explained by the strong initial adsorption of interfacial complexes from the mixed surfactant system at the air/solution interface, followed by adsorption at the silica interface. The formation of the interfacial complexes at the air/solution interface was proved by means of the surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex and causes synergistic lowering in the surface tension. The film rupture mechanism was explained by the heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface, which remained negatively charged.
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3.
  • Ikumapayi, Fatai, et al. (författare)
  • Recycling of process water in sulphide flotation : Effect of calcium and sulphate ions on flotation of galena
  • 2011
  • Ingår i: 5th International Flotation Conference 2011. - Red Hook : Curran Associates, Inc.. - 9781618393951 ; , s. 222-249
  • Konferensbidrag (refereegranskat)abstract
    • The effects of major components of calcium and sulphate species present in recycled process water on galena flotation has been investigated through Hallimond flotation, zeta-potential, diffuse reflectance FTIR spectroscopy and XPS measurements using pure galena mineral as well as bench scale flotation tests using complex sulphide ore. The significance of process water species in flotation has been assessed using deionised water, process water and simulated water containing calcium and sulphate ions in experiments. In addition, the effect of temperature in bench scale flotation tests has also been examined.Hallimond flotation indicated lower recoveries of galena in the presence of calcium and sulphate ions using potassium amyl xanthate as collector. Calcium ions increase zeta-potential of galena while sulphate ions have no effect. FTIR and XPS studies revealed the presence of surface oxidised sulfoxy, hydroxyl and carbonate species on galena at pH 10.5 in deionised and process water, which surface species affected xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that galena recovery is better in process water than tap water at room temperature. Flotation results also indicated decrease of galenarecovery at temperatures lower than 22oC in either tap water or process water.
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4.
  • Kota, Hanumantha Rao, et al. (författare)
  • Challenges in sulphide mineral processing
  • 2011
  • Ingår i: Open Mineral Processing Journal. - 1874-8414 .- 1874-8414. ; 4, s. 7-13
  • Tidskriftsartikel (refereegranskat)
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5.
  • Kota, Hanumantha Rao (författare)
  • Mixed anionic/non-ionic collectors in phosphate gangue flotation from magnetite fines
  • 2011
  • Ingår i: Open Mineral Processing Journal. - 1874-8414 .- 1874-8414. ; 4, s. 14-24
  • Tidskriftsartikel (refereegranskat)abstract
    • Scientists and technologists in world over are making large efforts to streamline the conventional technological schemes of ore processing, in particular froth flotation towards reducing overall costs, limiting the use of dangerous substances, decreasing waste streams and improving waste disposal. Hitherto, search for such innovations has been performed mainly empirically and there is an urgent need to shift these technologies to be more innovative and effective.Understanding of the fundamental concepts of aquatic chemistry of minerals–selective adsorption and selective redox reactions at mineral–solution interfaces would impact innovating conventional flotation process Molecular-level knowledge and coherent understanding of minerals contacted with aqueous solutions is required which underlie great opportunities in controlling mineral–solution interfaces towards the grand challenge of tomorrow’s science and mineral processing technology. Aqueous redox chemistry of sulphides and adsorption mechanisms, the problems of metal sulphides selectivity against pyrite and fine particle flotation have been highlighted and discussed in the light of literature. The requisite knowledge and research needs to address these issues have also been briefly presented.
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7.
  • Vilinska, Annamaria, et al. (författare)
  • Surface characterization of Acidithiobacillus ferrooxidans adapted to high copper and zinc ions concentration
  • 2011
  • Ingår i: Geomicrobiology Journal. - 0149-0451 .- 1521-0529. ; 28:3, s. 221-228
  • Tidskriftsartikel (refereegranskat)abstract
    • Changes in surface chemical properties of Acidithiobacillus ferrooxidans after adaptation to high copper and zinc ion concentration were studied by surface sensitive techniques such as zeta-potential, XPS and FT-IR measurements. The adapted bacteria were also characterized by their surface energies and adhesion capacities on different sulphide minerals. Their surface negative charge was decreased due to changes in the structure of bacterial surface layers. The metal ions adapted cells secreted more extracellular polymeric substances with a modified composition compared to unadapted ferrous ions grown cells. Bacterial cells hydrophilic property increased after adaptation and altered their adhesion behavior to sulphide mineral.
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8.
  • Vilinska, Annamaria (författare)
  • Surface thermodynamics and extended DLVO theory of Leptospirillum ferrooxidans cells' adhesion on sulfide minerals
  • 2011
  • Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 28:3, s. 151-158
  • Tidskriftsartikel (refereegranskat)abstract
    • The adhesion of Leptospirillum ferrooxidans bacterial cells onto the sulfide minerals pyrite and chalcopyrite was evaluated using two different physical-chemical approaches; thermodynamic and extended DLVO theory. For the parameters incorporated into calculations, the zeta potentials and contact angles of powdered solids and bacterial cells were acquired experimentally. The Hamaker constants essential for Lifshitz-van der Waals interaction. calculations were calculated following two different methods: macroscopic and microscopic. Adsorption tests were carried out at physiologic conditions to estimate the amount of cells adsorbed onto a mineral surface and the extent of alteration of that mineral surface in biobeneficiation. The free energy of adhesion was found to be negative for both minerals, indicating that the adhesion is energetically favored and preferred. The interaction energy diagrams of the total interacting force was also negative for the cases where the particles were charged oppositely; in the remaining cases, the total force was attractive after overcoming an energetic barrier caused by the repulsive electrostatic forces. Under the conditions of the adsorption test, the experimental results are in agreement with the theoretical; this suggests that the physical-chemical forces are crucial for bacterial adhesion.
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