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Träfflista för sökning "WFRF:(Kota Hanumantha Rao) srt2:(2010-2013)"

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

  • Resultat 21-28 av 28
  • Föregående 12[3]
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21.
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22.
  • Kota, Hanumantha Rao (författare)
  • Role of non-ionic surfactant in fatty acid phosphate gangue flotation from magnetite fines
  • 2010
  • Ingår i: Conference in Minerals Engineering. - Luleå : Luleå tekniska universitet. - 9789174390971 ; , s. 169-183
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Adsorption, contact angle and flotation of anionic Atrac and non-ionic ethaloxylated nonylphenol surfactant, and their mixture on apatite and magnetite were studied. The effect of calcium ions and sodium silicate on Atrac adsorption was investigated. The effect of Atrac adsorption on the contact angle data of apatite and magnetite in the presence and absence of sodium silicate was also examined. Wettability of solids depends on solids surface free energy and the surface energies of apatite and magnetite powders were calculated from polar and non-polar liquid contact angle data.A decrease in particle size increased the polar contribution to surface free energy due to unsaturated broken bonds on the surface. Atrac is seen to adsorb equally on apatite and magnetite, and the adsorption increased in the presence of calcium ions. The presence of water glass decreased the Atrac contact angle data on magnetite and also the flotation response demonstrating its role as magnetite depressant in flotation. The presence of non-ionic surfactant enhanced the Atrac flotation of apatite with no flotation of magnetite. Bench-scale flotation tests showed that 50% of Atrac can be replaced with non-ionic collector without impairing the flotation results. Results also illustrate that the non-ionic adsorbs on apatite in equal amount of Atrac collector signifying 1:1 composition of anionic and non-ionic collector on apatite surface. Non-ionic head group sitting in between anionic head groups screens the electrostatic repulsion and forms compact adsorbed layer on apatite surface thereby increasing the hydrophobicity and flotation.
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25.
  • Nooshabadi, Alireza Javadi, et al. (författare)
  • Formation of hydrogen peroxide by pyrite and its influence on flotation
  • 2013
  • Ingår i: Minerals Engineering. - 0892-6875 .- 1872-9444. ; 49, s. 128-134
  • Tidskriftsartikel (refereegranskat)abstract
    • Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by pyrite (FeS2), the most abundant metal sulphide on Earth, during grinding was investigated. It was found that pyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. Type of grinding medium on formation of hydrogen peroxide revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2. The effect of grinding atmosphere of air and N2 gas showed that nitrogen environment free from oxygen generated more H2O2 than air atmosphere suggesting that the oxygen in hydrogen peroxide is derived from water molecules. In addition, the solids after dry grinding producing more H2O2 than wet grinding indicate the role of pyrite surface or its catalytic activity in producing H2O2 from water. This study highlights the necessity of relooking into the electrochemical and/or galvanic interaction mechanisms between the grinding medium and pyrite in terms of its flotation behaviour.
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27.
  • 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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28.
  • 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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