| 1. |
|
|
| 2. |
- Dwari, Ranjan, et al.
(author)
-
Characterisation of particle tribo-charging and electron transfer with reference to electrostatic dry coal cleaning
- 2009
-
In: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 91:3-4, s. 100-110
-
Journal article (peer-reviewed)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.
|
|
| 3. |
|
|
| 4. |
- Kota, Hanumantha Rao, et al.
(author)
-
Mixed anionic/non-ionic collectors in phosphate gangue flotation from magnetite fines
- 2011
-
In: Open Mineral Processing Journal. - : Bentham Science Publishers Ltd.. - 1874-8414. ; 4, s. 14-24
-
Journal article (peer-reviewed)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.
|
|
| 5. |
- Rao, K Hanumantha, et al.
(author)
-
Flotation of phosphate gangue from magnetite fines - non-ionic surfactant as atrac collector modifier
- 2010
-
In: XXV International Mineral Processing Congress. - Carlton, Vic : The Australian Institute of Mining and Metallurgy. - 9781921522284 ; , s. 1933-1943
-
Conference paper (peer-reviewed)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 per cent 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.
|
|
