| 21. |
- Kota, Hanumantha Rao, et al.
(författare)
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Revisiting Sulphide Mineral (Bio) Processing: A Few Priorities And Directions
- 2013
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Ingår i: Journal of Powder Metallurgy & Mining. - : OMICS Publishing Group. - 2168-9806. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Large efforts are being made to streamline the conventional (chemical and physical) technological schemes of ore processing, remediation and environmental protection towards reducing overall costs, limiting the use of dangerous substances, decreasing waste streams and improving waste disposal and recycling practice. 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. Alternative biotechnological solutions and solutions mimicking natural processes are also being proposed. However, except for bioleaching, practical exploitation of the biotechnological potential in extractive industries and accompanying environmental protection measures remains far from feasibility. Understanding of the fundamental concepts of aquatic chemistry of minerals–selective adsorption and selective redox reactions at mineral– bacteria–solution interfaces, impact innovating conventional and bio-flotation, as well as (bio) remediation/detoxification of mineral and chemical wastes are necessary. Molecular-level knowledge and coherent understanding of minerals contacted with aqueous solutions is required that underlie great opportunities in controlling abiotic and biotic mineral– solution interfaces towards the grand challenge of tomorrow’s science and mineral processing technology
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| 22. |
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| 23. |
- Kota, Hanumantha Rao
(författare)
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Role of non-ionic surfactant in fatty acid phosphate gangue flotation from magnetite fines
- 2010
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Ingår i: Conference in Minerals Engineering. - Luleå : Luleå tekniska universitet. - 9789174390971 ; , s. 169-183
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Vilinska, Annamaria, et al.
(författare)
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Surface characterization of Acidithiobacillus ferrooxidans adapted to high copper and zinc ions concentration
- 2011
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 28:3, s. 221-228
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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, et al.
(författare)
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Surface thermodynamics and extended DLVO theory of Leptospirillum ferrooxidans cells' adhesion on sulfide minerals
- 2011
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Ingår i: Minerals & metallurgical processing. - : Springer Science and Business Media LLC. - 0747-9182. ; 28:3, s. 151-158
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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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