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Sökning: WFRF:(Kota Hanumantha Rao)

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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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2.
  • Karlkvist, T., et al. (författare)
  • Flotation selectivity of novel alkyl dicarboxylate reagents for calcite-fluorite separation
  • 2016
  • Ingår i: Tenside, Surfactants, Detergents. - 0932-3414 .- 2195-8564. ; 53:6, s. 516-523
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of amino acid-based surfactants with a fixed alkyl chain length and with two carboxyl groups separated by a spacer of one, two or three carbon atoms have been synthesized and evaluated as potential collectors for flotation of calcite and fluorite. A monocarboxylate amino acid-based surfactant having the same length of the hydrocarbon tail was also included for comparison in the study. Experiments using a Hallimond flotation tube showed that although the flotation reagents solely differ in terms of spacer, their efficacy in terms of flotation recovery varied very much. Whereas on calcite at pH 10.5 only the monocarboxylate collector gave a high yield, on fluorite at the same pH both the monocarboxylate and the dicarboxylate collectors with one carbon between the carboxyl groups gave good results. On calcite at the natural pH the monocarboxylate collector was most efficient but the dicarboxylate collectors with a two and a three-carbon spacer also gave a reasonable recovery. On fluorite at the natural pH the dicarboxylate collectors with a two- and a three-carbon spacer were most efficient. The zeta-potential and the flotation recovery of the mineral particles as a function of added collector were assessed and the adsorption was also monitored by diffuse reflectance infra-red spectroscopy. Taken together, the results showed that small changes in the head group region of the collector can radically affect flotation recovery. This type of knowledge is important to understand flotation selectivity in a mixture of similar minerals.
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3.
  • Karlkvist, T., et al. (författare)
  • Flotation selectivity of novel alkyl dicarboxylate reagents for apatite-calcite separation
  • 2015
  • Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 445, s. 40-47
  • Tidskriftsartikel (refereegranskat)abstract
    • The investigation aims to demonstrate the conceptual thoughts behind developing mineral specific reagents for use in flotation of calcium containing ores. For this purpose, a series of dicarboxylate-based surfactants with varying distance between the carboxylate groups (one, two or three methylene groups) was synthesized. A surfactant with the same alkyl chain length but with only one carboxylate group was also synthesized and evaluated. The adsorption behavior of these new reagents on pure apatite and pure calcite surfaces was studied using Hallimond tube flotation, FTIR and zeta potential measurements. The relation between the adsorption behavior of a given surfactant at a specific mineral surface and its molecular structure over a range of concentrations and pH values, as well as the region of maximum recovery, was 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. For example, out of the four compounds synthesized, only the one where the carboxylate groups were separated by a single methylene group floated apatite but not calcite, whereas calcite was efficiently floated with the monocarboxylic reagent, but not with the other reagents synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in the flotation studies was substantiated by zeta potential and infra-red spectroscopy data.
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4.
  • Abdel-Khalek, N.A., et al. (författare)
  • Effect of starch type on selectivity of cationic flotation of iron ore
  • 2012
  • Ingår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 121:2, s. 98-102
  • 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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10.
  • Ikumapayi, Fatai, et al. (författare)
  • Recycling of process water : effect of calcium and sulphate ions in sulphides flotation
  • 2010
  • Ingår i: Conference in Minerals Engineering. - Luleå : Luleå tekniska universitet. - 9789174390971 ; , s. 51-61
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • The effects of major components of calcium and sulphate ions in process water on sulphide mineral flotation has been investigated through Hallimond flotation of pure sulphide minerals using tapwater and water containing sulphate and calcium ions as well as through bench scale flotation of complex sulphide ores using tapwater and process water and with tapwater in the presence of calcium and sulphate ions. Hallimond flotation indicated activation of pyrite and slight depression of galena and chalcopyrite in the presence of high concentration of major species of calcium and sulphate ions using potassium amyl xanthate as collector. Bench scale flotation indicated activation of zinc when processwater was used and flotation in tapwater containing calcium and sulphate ions presented similar but not identical results.
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