Change search
Refine search result
1234 1 - 50 of 170
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abdel-Khalek, N.A.
    et al.
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Yassin, K.E.
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kandel, A-H
    Chemistry Department, Faculty of Science, Helwan University.
    Effect of starch type on selectivity of cationic flotation of iron ore2012In: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 121, no 2, p. 98-102Article in journal (Refereed)
    Abstract [en]

    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

  • 2.
    Alexandrova, L.
    et al.
    Institute of Physical Chemistry, Bulgarian Academy of Sciences.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Grigorov, L.
    Department of Inorganic Chemistry, University of Sofia.
    Pugh, R.J.
    Institute for Surface Chemistry, Box 5607, SE-11486 Stockholm.
    The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 373, no 1-3, p. 145-151Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Alexandrova, L.
    et al.
    Institute of Physical Chemistry, Bulgarian Academy of Sciences.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Grigorov, L.
    Department of Inorganic Chemistry, University of Sofia.
    Pugh, R.J.
    Three-phase-contact parameters measurements for silica-mixed cationic-anionic surfactant systems2009In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 348, no 1-3, p. 228-233Article in journal (Refereed)
    Abstract [en]

    The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [Platikanov D., J. Phys. Chem., 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants hetero-coagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces.

  • 4.
    Alexandrova, L.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Pugh, R.J.
    Grigorov, L.
    University of Sofia.
    Thin film studies in mixed cationic-anionic surfactant system2003In: Proceedings of the XXII International Mineral Processing Congress / [ed] Leon Lorenzen, Marshalltown, South Africa: South African Institute of Mining and Metallurgy, 2003, p. 838-846Conference paper (Refereed)
  • 5.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2011Conference paper (Other academic)
  • 6.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2010Conference paper (Other academic)
  • 7.
    Chernyschova, Irina V.
    et al.
    St. Petersburg State Technical University.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vidyadhar, A.
    St. Petersburg State Technical University.
    Shchukarev, A.V.
    Avdelningen för oorganisk kemi, Umeå universitet.
    Mechanism of adsorption of long-chain alkylamines on silicates: a spectroscopic study. 2. Albite2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 3, p. 775-785Article in journal (Refereed)
    Abstract [en]

    Using FTIR (DRIFTS and IRRAS) and XPS spectroscopy, ζ potential measurements, and Hallimond flotation tests, we confirmed that long-chain primary amines are adsorbed on silicates at pH 6-7 through the 2D-3D precipitation mechanism. The orientation and packing of dodecyl- and hexadecylammonium acetate and chloride adsorbed on albite in the different regions of the adsorption isotherm were determined. It was shown that these characteristics depend strongly on the substrate. Coadsorption of the counterion was not revealed, but the counterion was found to affect indirectly the adsorption at concentrations above the concentration of the bulk amine precipitation

  • 8.
    Chernyshova, Irina V.
    et al.
    St. Petersburg State Technical University.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A new approach to the IR spectroscopic study of molecular orientation and packing in adsorbed monolayers: orientation and packing of long-chain primary amines and alcohols on quartz2001In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, no 4, p. 810-820Article in journal (Refereed)
    Abstract [en]

    A new method is suggested for determining the molecular orientation in adsorbed films with uniaxial and biaxial anisotropy from two (s- and p-polarized) IRRAS spectra of the same sample, measured at the optimal angle of incidence. The method is simple, does not use the film thickness, and is internally stable with respect to the uncertainty in the input optical parameters of the anisotropic film. The advantages and limitations of the method are discussed. To validate the method, we determined the orientation of hexadecylamine and hexadecyl alcohol adsorbed on a quartz surface. It is shown that at a concentration above the concentration of 2D precipitation but below the concentration of 3D precipitation, hydrocarbon chains in the adsorbed amine monolayer are well-packed in a monoclinic (biaxial) subcell with a tilt angle of about 30°. Chaotically arranged crystallites of the amine molecules appear at the surface at a concentration higher than the concentration of 3D precipitation. Adsorbed monolayers of the alcohol turn out to have a hexagonal structure, in which the hydrocarbon tails are "flip-flop" positioned and tilted by 25-30° from the surface normal.

  • 9.
    Chernyshova, Irina V.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanism of coadsorption of long-chain alkylamines and alcohols on silicates. Fourier transform spectroscopy and X-ray photoelectron spectroscopy studies2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 9, p. 2711-2719Article in journal (Refereed)
    Abstract [en]

    Coadsorption of long-chain primary amines and alcohols on silicates (quartz and albite) at pH 6-7 was studied using Fourier transform (DRIFTS and IRRAS) and X-ray photoelectron spectroscopy. The ionization state of the amino headgroups, the molecular orientation, and packing in the adsorbed mixed monolayers were determined. The results were interpreted in terms of the modified model of 2D-3D precipitation, where the elementary adsorbing species from the solution is the amine-alcohol-water association.

  • 10.
    Chernysova, Irina V.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vidyadhar, A.
    Luleå University of Technology.
    Shchukarev, A. V.
    Avdelningen för oorganisk kemi, Umeå universitet.
    Mechanism of adsorption of long-chain alkylamines on silicates: a spectroscopic study. 1. Quartz2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 21, p. 8071-8084Article in journal (Refereed)
    Abstract [en]

    The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with ζ potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, ζ potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.

  • 11.
    Das, A.
    et al.
    Indian Institute of Science.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sharma, P.K.
    Luleå University of Technology.
    Natarajan, K.A.
    Indian Institute of Science.
    Forssberg, Eric
    Surface chemical and adsorption studies using Thiobacillus ferrooxidans with reference to bacterial adhesion to sulfide minerals1999In: Biohydrometallurgy and the Environment toward the Mining of the 21st century: Proceedings of the International Biohydrometallurgy Symposium IBS 1999, Madrid, Spain / [ed] R. Amils; A. Ballester, Elsevier, 1999, Vol. Part A: Bioleaching, Microbiology, p. 697-707Conference paper (Refereed)
  • 12.
    Deo, N.
    et al.
    Indian Institute of Science.
    Natarajan, K.A.
    Indian Institute of Science.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Biodegradation of some organic reagents from mineral process effluents1999In: Biohydrometallurgy and the Environment toward the Mining of the 21st century: Proceedings of the International Biohydrometallurgy Symposium IBS 1999, Madrid, Spain / [ed] R. Amils; A. Ballester, Elsevier, 1999, Vol. Part B: Molucular biology, biosorption, bioremediation, p. 687-696Conference paper (Refereed)
    Abstract [en]

    The utility of a soil microbe, namely Bacillus polymyxa, in the removal of organic reagents such as dodecylamine, ether diamine, isopropyl xanthate and sodium oleate from aqueous solutions is demonstrated. Time-bound removal of the above organic reagents from an alkaline solution was investigated under different experimental conditions during bacterial growth and in the presence of metabolites by frequent monitoring of residual concentrations as a function of time, reagent concentration and cell density. The stages and mechanisms in the biodegradation process were monitored through UV-visible and FTIR spectroscopy. Surface chemistry of the bacterial cells as well as the biosorption tendency for various organics were also established through electrokinetic and adsorption density measurements. Both the cationic amines were found to be biosorbed followed by their degradation through bacterial metabolism. The presence of the organic reagents promoted bacterial growth through effective bacterial utilization of nitrogen and carbon from the organics. Under optimal conditions, complete degradation and bioremoval of all the organics could be achieved

  • 13.
    Dwari, Ranjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Fine coal preparation using novel tribo-electrostatic separator2007Conference paper (Refereed)
  • 14. Dwari, Ranjan
    et al.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Fine coal preparation using novel tribo-electrostatic separator2009In: Proceedings of the International Conference on Beneficiation of Fines and its Technology / [ed] Asim Kumar Mukherjee; Debashish Bhattacharjee, Tata McGraw Hill , 2009, p. 81-100Conference paper (Refereed)
  • 15.
    Dwari, Ranjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Somasundaran, P.
    Henry Krumb School of Mines, Columbia University, New York.
    Characterisation of particle tribo-charging and electron transfer with reference to eloectrostatic dry coal cleaning2008Conference paper (Refereed)
  • 16. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An exploration on tribo-charging and electron transfer of ash forming minerals in coal by contact angle goniometry2007In: Conference in Mineral Processing, Luleå, Sweden, February 6-7, 2007, 2007, p. 41-54Conference paper (Other academic)
  • 17. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Characterising electron transfer mechanism in tribo-electrification of pyrite through contact angle measurements2008In: Open Mineral Processing Journal, ISSN 1874-8414, E-ISSN 1874-8414, Vol. 1, p. 6-17Article in journal (Refereed)
    Abstract [en]

    Coal beneficiation by tribo-electrostatic method depends on tribo-charging attributes of coal and ash forming minerals. The tribo-electrification behaviour of pyrite mineral contacted with different materials has been investigated through charge measurements and the charge acquisition is probed through surface energy calculations from liquid contact angle data. Liquid contact angle on pyrite powder after tribo-electrification is determined by Kruss tensiometer using Washburn's equation. The sample holder in tensiometer is specially fabricated with different materials serving the purpose of tribo-electrification and contact angle measurement. The acid and base parameters of pyrite surface determined with van Oss acid-base approach using liquid contact angle data after tribo-electrification with different materials revealed the charging phenomena and electron transfer mechanism. The results showed an explicit correlation between the charge generated by pyrite powder and surface acceptor (acid)-donor (base) electronic state underlying the work functions of contacting surfaces. Thus a method for characterising the changes in surface energetic structure of solids during contact electrification in terms of surface acid-base parameters has been illustrated for the first time.

  • 18. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Contact electrification and electrostatic separation of ash-forming minerals from high ash non-coking coal using novel fluidised bed tribo-charging system2008In: Proceedings of XXIV International Mineral Processing Congress: Beijing, China 24-28 September 2008 / [ed] Wang Dian Zuo; Sun Chuan Yao; Wang Fu Liang; Zhang Li Cheng; Han Long, Beijing: American Science Press Inc., 2008, p. 3540-3550Conference paper (Refereed)
  • 19. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Dry beneficiation of coal: a review2007In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 28, no 3, p. 177-234Article, review/survey (Other academic)
    Abstract [en]

    Coal continues to play a major role in the economic development of a country, especially in metallurgical industries and conventional power generation plants. For effective utilization of high ash coals, it is necessary to beneficiate them. The wet beneficiation process for coal cleaning is currently the predominant method of purification of coal in the world. However, dry beneficiation of coal has obvious advantages over wet processes. The dry processes for coal are based on the physical properties of coal and its associated mineral matters. Different types of equipment for dry beneficiation have been developed, based on the exploitation of physical properties such as density, size, shape, magnetic susceptibility, and electrical conductivity. This article presents a summary assessment of different technologies and their performance in the beneficiation process of high ash coals with particular reference to Indian thermal coals. The literature on sorting, air jigs, magnetic separation, air-dense medium fluidized bed separation, and electrostatic separation is summarized and discussed

  • 20. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Fine coal preparation using novel tribo-electrostatic separator2009In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 22, no 2, p. 119-127Article in journal (Refereed)
    Abstract [en]

    Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of tribo-electric coal/ash cleaning is carried out with a newly built cylindrical fluidised bed tribo-charger with internal baffles, made up of copper metal. The charge transfer in coal maceral and mineral particles after repeated contact with copper plate tribo-charger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge generated during tribo-electrification is discussed with respect to gas flow rate and residence time in fluidised bed tribo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with -300 μm size fraction of coal containing 43% ash showed that the ash content can be reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.

  • 21. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    High ash non-coking coal preparation by tribo-electrostatic technique2006In: Proceedings, International Seminar on Mineral Processing Technology / [ed] Bhaskar Raju, New Dehli: Allied Publishers Ltd , 2006, p. 30-41Conference paper (Refereed)
  • 22. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Non-coking coal preparation by novel tribo-electrostatic method2008In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, no 17-18, p. 3562-3571Article in journal (Refereed)
    Abstract [en]

    A new laboratory fluidised bed tribo-electrostatic separator has been assembled and the beneficiation potential of thermal non-coking coal from Hingula block of Talcher coal field, India, is examined on this separator. The uniqueness of the separator originates from the efficient tribo-electrification of coal material in the cylindrical fluidised bed with internal baffle system. The collecting bins of the material underneath the copper plate electrodes are designed to function as Faraday cups such that the charge polarity and magnitude of particles in each bin can be measured directly. The liberation attributes of coal material is assessed by sink and float analysis of various size fractions. The mineral and maceral composition is determined by XRD and petrographic analysis. The separation tests were conducted at different tribo-charging and applied voltage conditions. The material collected in bins close to positive and negative electrodes show an ash content of 61% and 8% respectively, illustrating differential charge acquisition of mineral rich and coal rich particles during tribo-electrification. The charge results are in good agreement with the ash content of the coal material collected in the bins. The results showed that a clean coal of about 15% ash can be obtained from a coal containing 30% ash with about 70% yield. A better separation results can be achieved by recycling the material. The ash content in the clean coal is however limited by the liberation characteristics of the coal, which is evidenced by the SEM analysis of the particles in different bins. Thus, the tribo-electrostatic method observed to be a promising dry coal preparation technique.

  • 23. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Novel fluidised-bed tribo-electrostatic separator for dry coal preparation2008In: Conference in Minerals Engineering 2008, Luleå: Luleå tekniska universitet, 2008, p. 15-29Conference paper (Other academic)
    Abstract [en]

    Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of triboelectric coal/ash cleaning is carried out with a newly built cylindrical fluidised-bed tribocharger with internal baffles, all made up of copper metal. The charge transfer of coal maceral and mineral particles upon contacts with copper plate of tribocharger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge is discussed with respect to gas flow rate and residence time in fluidised-bed trobo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with minus 300 μm size fraction of coal containing 43% ash showed that the ash content is reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.

  • 24. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tribo-electrostatic behaviour of high ash non-coking Indian thermal coal2006In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 81, no 2, p. 93-104Article in journal (Refereed)
    Abstract [en]

    The tribo-electrostatic method was applied to beneficiate non-coking Indian thermal coal from Ramagundam coal mines containing nearly 45% ash content. The microscopic studies revealed that quartz and kaolinite are the dominant minerals whereas illite, goethite, siderite and pyrite are the minor inclusions in the coal. Contact electrification of ash-forming minerals and coal matter was carried out using different tribo-charger materials of Al, Cu, brass, perspex and teflon. The Cu tribo-charger was found to be optimum to acquire differential charge between ash-forming inorganics and coal matter. The temperature effect on the magnitude of contact charge acquisition was found to be significant. Tests on a laboratory in-house built tribo-electrostatic free-fall separator with minus 300 μm coal showed that the ash content was reduced from 45% to about 18%, and a clean coal product as judged by the washability studies can be obtained. The results illustrate that the non-coking coals can be beneficiated using the scientific knowledge on the response and behaviour of coal and non-coal matters to electric charges.

  • 25. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Somasundaran, P.
    Langmuir Center fo Colloids and Interfaces, Columbia University, New York.
    A method for determining the electron transfer and charge characteristics between two contacting surfaces in tribo-electrostatic coal beneficiation2007In: Proceedings of the International Seminar on Mineral Processing Technology: With focus on Industrial Minerals and their processing for value addition / [ed] N.K. Khosla; G.N. Jadhav, New Dehli: Allied Publishers Ltd , 2007, p. 55-59Conference paper (Refereed)
  • 26. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Somasundaran, P.
    Henry Krumb School of Mines, Columbia University, New York.
    Characterisation of particle tribo-charging and electron transfer with reference to electrostatic dry coal cleaning2009In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 91, no 3-4, p. 100-110Article in journal (Refereed)
    Abstract [en]

    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.

  • 27.
    F., Su
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samskog, Per-Olof
    Computer estimation of flotation kinetic model parameters1998In: 2Papers presented at the APCOM '98 conference, organized by the Institution of Mining and Metallurgy and held in London, United Kingdom from 19 to 23 April, 1998, London: The Institution of Mining and Metallurgy , 1998, p. 513-524Conference paper (Refereed)
    Abstract [en]

    The effect of chemical variables on the kinetic parameters of apatite flotation from magnetite has been investigated. The two common first-order kinetic models reported in the literature, i.e., the model with rectangular distribution of floatabilities and the model with fast and slow-floating components (F-S model) have been applied in the evaluation of flotation results. The models are evaluated by fitting the flotation results from batch flotation tests. The results although indicate that both models describe the apatite flotation kinetics well in a wide range of kinetic parameters, the F-S model is found to be better in the goodness of fit to the results from every flotation test and also to describe the flotation performance adequately. The kinetic parameters of the F-S model are varied with a change in chemical variables. In particular, the rate constants ratio Kf/Ks is found to be an important parameter for achieving selectivity between apatite and magnetite, and the effect of reagents dosages on the ratio is discussed. The effect of particle size on the apatite flotation kinetics is also illustrated by analysing the froth products at each flotation time in different size classes.

  • 28. Ikumapayi, F
    et al.
    Johansson, B
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of process water in sulfides processing and flotation selectivity2010In: XXV International Mineral Processing Congress: IMPC 2010, "Smarter processing for the future" : Brisbane, Australia 6-10 September 2010 : congress proceedings., Carlton, Vic: The Australian Institute of Mining and Metallurgy , 2010, p. 4079-4088Conference paper (Refereed)
  • 29. Ikumapayi, Fatai
    et al.
    Johansson, Björn
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of process water: effect of calcium and sulphate ions in sulphides flotation2010In: Conference in Minerals Engineering: Luleå, 2 -3 februari 2010 / [ed] Johanna Alatalo, Luleå: Luleå tekniska universitet, 2010, p. 51-61Conference paper (Other academic)
    Abstract [en]

    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.

  • 30. Ikumapayi, Fatai
    et al.
    Johansson, Björn
    Boliden Mineral AB.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of process water in sulphides processing and flotation selectivity2009In: International Seminar on Mineral Processing Technology (MPT-2009): Institute of Minerals and Materials Technology, CSIR, Bhubaneswar, India and Indian Institute of Mineral Engineers, New Dehli: Allied Publishers Ltd , 2009Conference paper (Refereed)
  • 31.
    Ikumapayi, Fatai
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Recycling process water in complex sulfide ore flotation: Effect of calcium and sulfate on sulfide minerals recovery2015In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 36, no 1, p. 45-64Article in journal (Refereed)
    Abstract [en]

    The influence of major components of calcium and sulfate ions in process water on xanthate collector adsorption and flotation response of pure chalcopyrite, galena, and sphalerite minerals was investigated by Hallimond tube flotation, zeta-potential, FTIR, and XPS spectroscopy studies, while bench scale flotation tests were also carried out using complex sulfide ores. Marginally lower recoveries of chalcopyrite and galena in process water and in the presence of calcium and sulfate ions in both deionized and process waters using potassium amyl xanthate as collector were observed in Hallimond tube flotation, whereas sphalerite floatability is a little increased in process water using isobutyl xanthate as collector. Zeta-potential results show the adsorption of calcium ions on the minerals. FTIR and XPS studies revealed the presence of surface oxidized sulfoxy species and surface calcium carbonates and/or calcium sulfate on chalcopyrite and galena in the presence of process water and water-containing calcium ions at flotation pH 10.5, and these surface species influenced xanthate adsorption. Surface-oxidized sulfoxy and carbonate species were seen on sphalerite surface in the presence of deionized water, process water, and water-containing calcium and sulfate ions at pH 11.5, but the surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulfide ores showed that chalcopyrite, galena, and sphalerite recoveries are higher in process water than tap water and general decrease of the minerals floatability at temperatures lower than 22°C in either tap water or process water

  • 32.
    Ikumapayi, Fatai
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Johansson, B.
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling process water in complex sulphide ore flotation2012In: XXVI International Mineral Processing Congress (IMPC) 2012: proceedings, New Dehli, India 24-28 september 2012, New Dehli: The Indian Institute of Metals , 2012, p. 4411-4425Conference paper (Refereed)
    Abstract [en]

    An approach to environmental sustainability and improved process economy, in sulphide minerals production is recycling of process water in flotation of complex sulphide ores, although the chemistry of process water may be a critical issue to flotation efficiency. The influence of major components of calcium and sulphate ions in process water on xanthate collector adsorption and flotation response using pure chalcopyrite, galena and sphalerite minerals were investigated by Hallimond flotation, zeta-potential measurement, FTIR and XPS spectroscopy studies, while bench scale flotation tests were also carried out using complex sulphide ores. The impact of the species in flotation was comprehended using deionised water, tap water, process water and simulated water containing equivalent amount of calcium and sulphate species in process water. Hallimond flotation results showed a decrease of chalcopyrite and galena recovery in process water and also in the presence of calcium and sulphate ions in both deionised and process waters, whereas sphalerite does not respond to flotation. The adsorption of calcium and metal ions but not sulphate ions on the minerals is evidenced by zeta-potential data. FTIR and XPS studies revealed the presence of surface oxidized sulfoxy species and surface calcium carbonates on chalcopyrite in the presence of process water and water containing calcium ions, surface oxidized sulfoxy and carbonate species on galena in the presence of deionised water, process water and water containing calcium and sulphate ions, all at flotation pH 10.5, and these surface species influenced xanthate adsorption. The presence of surface oxidized sulfoxy and carbonate species at the sphalerite flotation pH 11.5 were seen in the presence of deionised water, process water and water containing calcium and sulphate ions, but the surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that chalcopyrite, galena and sphalerite recoveries are better in process water than tap water. The studies showed that the process water can be recycled in flotation with no detrimental effect on grade and recovery of sulphide minerals.

  • 33.
    Ikumapayi, Fatai
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Johansson, Björn
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of process water in sulphide flotation: Effect of calcium and sulphate ions on flotation of galena2011In: 5th International Flotation Conference 2011: (Flotation '11) ; Cape Town, South Africa, 14 - 17 November 2011, Red Hook: Curran Associates, Inc., 2011, Vol. 1, p. 222-249Conference paper (Refereed)
    Abstract [en]

    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.

  • 34.
    Ikumapayi, Fatai
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Johansson, Björn
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling of process water in sulphide flotation: effect of calcium and sulphate ions on flotation of galena2012In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 39, p. 77-88Article in journal (Refereed)
    Abstract [en]

    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. The significance of process water species in flotation has been understood using deionised water, process water and simulated tap water containing equivalent calcium and sulphate ions concentration as in process water.Hallimond flotation indicated marginally lower recoveries of galena in the presence of calcium and sulphate ions using potassium amyl xanthate as collector. Zeta-potential shows the adsorption of calcium ions whereby the potential are seen to increase while sulphate ions have no significant effect. FTIR and XPS studies revealed surface calcium carbonate and/or calcium sulphate species in process water which affected xanthate adsorption. Presence of surface oxidised species such as sulfoxy, hydroxyl species on galena at pH 10.5 in deionised and process water was also revealed.

  • 35. Ikumapayi, Fatai
    et al.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Johansson, Björn
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling process water in sulfide flotation: Part A: Effect of calcium and sulfate on sphalerite recovery2012In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 29, no 4, p. 183-191Article in journal (Refereed)
  • 36.
    Ikumapayi, Fatai
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mäkitalo, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Johansson, Björn
    Boliden Mineral AB, New Boliden AB.
    Rao, Hanumantha
    Flotation response to recycled process water in sulphide flotation2011In: Proceedings of the XII International Seminar on Mineral Processing Technology (MPT-2011), Oct 20-22, 2011, Udaipur, India, 2011Conference paper (Refereed)
  • 37. Ikumapayi, Fatai
    et al.
    Sis, Hikmet
    Inonu University.
    Johansson, Björn
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Recycling process water in sulfide flotation: Part B: Effect of H2O2 and process water components on sphalerite flotation from complex sulfide2012In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 29, no 4, p. 192-198Article in journal (Refereed)
    Abstract [en]

    Hydrogen peroxide production was measured during the grinding of a complex sulfide ore, and its oxidizing effect on solid surfaces was investigated using Fourier transform infrared spectroscopy (FTIR) with diffuse reflectance attachment measurement. In turn, an attempt was made to correlate the formation of hydrogen peroxide, surface oxidation and sphalerite flotation. Additionally, in order to predict and minimize detrimental production problems due to the recycling of process water in sulfide ore processing, the effects of major components of calcium and sulfate species present in recycled process water and the effect of temperature on sphalerite flotation were investigated through bench-scale flotation tests using complex sulfide ores. The significance of process water species in flotation was studied using tap water, process water and simulated water containing calcium and sulfate ions. Formation of hydrogen peroxide was revealed during the grinding of the complex sulfide ore, and its formation was counteracted by diethylenetriamine (DETA). The FTIR spectrum of the pulp solid fraction showed varying degrees of oxidized surface species, which are related to the concentration of H2O2 analyzed in pulp liquid. Bench-scale flotation using two different complex sulfide ores showed that sphalerite recovery is better in process water than in tap water. Flotation results also indicated a varied recovery of sphalerite at different temperatures in either tap water or process water

  • 38.
    I.V., Chernyschova
    et al.
    St. Petersburg State Technical University.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanism of co-adsorption oflong-chain alkylamines and alcohols on silicates: FTIR and XPS spectroscopy studies2002In: International Seminar on Mineral Processing Technology: MPT-2002 / [ed] S. Subramanian; K.A. Natarajan; B.S. Rao; T.R.R. Rao, Bangalore: Indian Institute of Science, Department of Mechanical Engineering , 2002, p. 58-65Conference paper (Refereed)
  • 39.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    A New Insight Into Oxidation Mechanisms of Sulphide Minerals2014Conference paper (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was examined. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite ((Zn, Fe) S), and galena (PbS) generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids are placed in water immediately after dry grinding. Pyrite produced more H2O2 than other minerals and the order of H2O2 production by the minerals was found to be pyrite > chalcopyrite > sphalerite > galena. The pH of the water influenced the extent of hydrogen peroxide formation with greater amounts of H2O2 produced at highly acidic pH. Furthermore, the effect of mixed sulphide minerals, i.e., pyrite–chalcopyrite, pyrite–galena, chalcopyrite–galena and sphalerite–pyrite, sphalerite–chalcopyrite and sphalerite-galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction. There is clear correlation of the amount of H2O2 production with the rest potential of the sulphide minerals; the greater the rest potential of a mineral the greater the formation of H2O2. This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behaviour in the context of inevitable H2O2 existence in the pulp liquid

  • 40.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effect of grinding environment on galena flotation2014Conference paper (Refereed)
    Abstract [en]

    The participation of H2O2 in oxidation of the galena mineral and as a result in decreasing of the concentrate recovery of galena mineral has not yet been shown. In this study the effect of two types of grinding media in wet and dry grinding on the formation of hydrogen peroxide and galena flotation was investigated. Laboratory stainless steel ball mill (Model 2VS, CAPCO Test Equipment, Suffolk, UK) was used for grinding galena with mild steel and stainless steel media. Galena ground with mild steel generated more hydrogen peroxide than galena ground with stainless steel media. Galena ground with mild steel has a lower galena recovery than galena ground with stainless steel media. Solutions of 2, 9-dimethyl-1, 10-phenanthroline (DMP) were used for estimating H2O2 amount in pulp liquid with DU® Series 700 UV/Vis Scanning Spectrophotometer. This study highlights the necessity of relooking into galvanic interaction mechanisms between the grinding medium and galena in terms of its flotation behavior.

  • 41.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Formation of hydrogen peroxide by chalcopyrite and its influence on flotation2013In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 30, no 4, p. 212-219Article in journal (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by chalcopyrite (CuFeS2), which is a copper iron sulfide mineral, during grinding, was investigated. It was observed that chalcopyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. The generation of H2O2 in either wet or dry grinding was thought to be due to a reaction between chalcopyrite and water where the mineral surface is catalytically active in producing •OH free radicals by breaking down the water molecule. Effect of pH in grinding medium or water pH in which solids are added immediately after dry grinding showed lower the pH value more was the H2O2 generation. When chalcopyrite and pyrite are mixed in different proportions, the formation of H2O2 was seen to increase with increasing pyrite fraction in the mixed composition. The results of H2O2 formation in pulp liquid of chalcopyrite and together with pyrite at different experimental conditions have been explained by Eh-pH diagrams of these minerals. This study highlights the necessity of revisiting the electrochemical and/or galvanic interaction mechanisms between the chalcopyrite and pyrite in terms of their flotation behaviour.

  • 42.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Formation of hydrogen peroxide by chalcopyrite and pyrite2014Conference paper (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by chalcopyrite (CuFeS2), which is a copper iron sulfide mineral, during grinding, was investigated. It was observed that chalcopyrite and pyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. The generation of H2O2 in either wet or dry grinding was thought to be due to a reaction between chalcopyrite and water where the mineral surface is catalytically active in producing •OH free radicals by breaking down the water molecule. When chalcopyrite and pyrite are mixed in different proportions, the formation of H2O2 was seen to increase with increasing pyrite fraction in the mixed composition. The results of H2O2 formation in pulp liquid of chalcopyrite and together with pyrite at different experimental conditions have been explained by Eh-pH diagrams of these minerals. This study highlights the necessity of revisiting the electrochemical and/or galvanic interaction mechanisms between the chalcopyrite and pyrite.

  • 43.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Formation of hydrogen peroxide by galena and its influence on flotation2014In: Advanced Powder Technology, ISSN 0921-8831, E-ISSN 1568-5527, Vol. 25, no 2, p. 832-839Article in journal (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, during the grinding of galena (PbS) was examined. It was observed that galena generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids were placed in water immediately after dry grinding. The generation of H2O2 during either wet or dry grinding was thought to be due to a reaction between galena and water, when the mineral surface is catalytically active, to produce OH• free radicals by breaking down the water molecule. It was also shown that galena could generate H2O2 in the presence or absence of dissolved oxygen in water. The concentration of H2O2 formed increased with decreasing pH. The effects of using mixtures of pyrite or chalcopyrite with galena were also investigated. In pyrite-galena mixture, the formation of H2O2 increased with an increase in the proportion of pyrite. This was also the case with an increase in the fraction of chalcopyrite in chalcopyrite-galena mixtures. The oxidation or dissolution of one specific mineral rather than the other in a mixture can be explained better by considering the extent of H2O2 formation rather than galvanic interactions. It appears that H2O2 plays a greater role in the oxidation of sulphides or in aiding the extensively reported galvanic interactions. This study highlights the necessity of further study of electrochemical and/or galvanic interaction mechanisms between pyrite and galena or chalcopyrite and galena in terms of their flotation behaviour.

  • 44.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Formation of hydrogen peroxide by sphalerite2013In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 125, p. 78-85Article in journal (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sphalerite ((Zn, Fe) S) was examined during its grinding process. It was observed that sphalerite generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids placed in water immediately after dry grinding. The generation of H2O2 in either wet or dry grinding was thought to be due to a reaction between sphalerite and water where the mineral surface is catalytically active to produce OH• free radicals by breaking down the water molecule. Effect of pH on the formation of H2O2 by sphalerite was shown that the acidic pH generated more H2O2. Mixtures of pyrite, chalcopyrite and galena with sphalerite on the formation of H2O2 were also probed. It was shown that the concentration of H2O2 increases with increasing pyrite or chalcopyrite fraction in pyrite–sphalerite, chalcopyrite–sphalerite mixtures but with an increase in galena proportion, the concentration of H2O2 decreased in galena–sphalerite mixture. The oxidation or dissolution of one mineral than the other in a mixture can be explained better with the extent of H2O2 formation in the pulp liquid than galvanic interactions. It is clear of the greater role of H2O2 in the oxidation of sulphides or aiding the extensively reported galvanic interactions since the amount of H2O2 generated with a specific mineral followed the rest potential series. This study highlights the necessity of further investigations into the role of H2O2 in electrochemical and/or galvanic interaction mechanisms between pyrite, chalcopyrite and galena with sphalerite.

  • 45.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Formation of hydrogen peroxide by sulphide minerals2014In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 141, p. 82-88Article in journal (Refereed)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was investigated. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite ((Zn,Fe)S), and galena (PbS), which are the most abundant sulphide minerals on Earth, generated H2O2 in pulp liquid during wet grinding in the presence of dissolved oxygen in water and also when the solids are placed in water immediately after dry grinding. Pyrite generated more H2O2 than other minerals and the order of H2O2 production by the minerals found to be pyrite > chalcopyrite > sphalerite > galena. The pH of water influenced the extent of hydrogen peroxide formation where higher amounts of H2O2 are produced at highly acidic pH. Furthermore, the effect of mixed sulphide minerals, i.e., pyrite–chalcopyrite, pyrite–galena, chalcopyrite–galena and sphalerite–pyrite, sphalerite–chalcopyrite and sphalerite–galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction in chalcopyrite–pyrite, galena–pyrite and sphalerite–pyrite compositions. The results also corroborate the amount of H2O2 production with the rest potential of the sulphide minerals; higher the rest potential of a sulphide mineral, formation of H2O2 is more. Most likely H2O2 is responsible for the oxidation of sulphide minerals and dissolution of non-ferrous metal sulphides in the presence of ferrous sulphide in addition to galvanic interactions. This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between pyrite and other sulphide minerals in terms of their flotation and leaching behaviour in the context of inevitable H2O2 existence in the pulp liquid.

  • 46.
    Javadi, Alireza
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sulphide mineral flotation: a new insight into oxidation mechanisms2013In: XIII International Seminar on Mineral Processing Technology: CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha 751013, India / [ed] Alok Tripathy, Madras: Indian Institute of Technology Madras, 2013, p. 169-182Conference paper (Refereed)
    Abstract [en]

    The formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was investigated. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS), and galena (PbS), which are the most abundant sulphide minerals on Earth, generated H2O2 in pulp liquid during wet grinding in the presence and absence of dissolved oxygen in water and also when the freshly ground solids were placed in water immediately after dry grinding. Pyrite generated more H2O2 than the other sulphide minerals and the order of H2O2 production by the minerals was found to be pyrite > chalcopyrite >sphalerite> galena. The pH of water influenced the extent of hydrogen peroxide formation where higher amounts of H2O2 were produced at highly acidic pH. The amount of H2O2 formed also increased with increasing sulphide mineral loading and grinding time due to increased surface area and its interaction with water.The sulphide surfaces are highly catalytically active due to surface defect sites and unsaturation because of broken bonds and capable of breaking down the water molecule leading to hydroxyl free radicals. The type of grinding medium on formation of hydrogen peroxide by pyrite 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.Furthermore, the effect of mixed sulphide minerals, i.e., pyrite–chalcopyrite, pyrite–galena, chalcopyrite–galena and sphalerite–pyrite, sphalerite–chalcopyrite and sphalerite–galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction in chalcopyrite–pyrite composition. In pyrite–sphalerite, chalcopyrite–sphalerite or galena– sphalerite mixed compositions, with the increase in pyrite or chalcopyrite proportion, the concentration of H2O2 increased but with increase in galena proportion, the concentration of H2O2 decreased. By increasing the pyrite proportion in pyrite–galena mixture, the concentration of H2O2 increased. Similarly, in the mixture of chalcopyrite–galena, the concentration of H2O2 increased with increasing chalcopyrite fraction. The results of H2O2formation in pulp liquid of individual sulphide minerals and in combination at different experimental conditions have been explained by Eh–pH diagrams of these minerals and the existence of free metal ions that are equally responsible for H2O2 formation besides the catalytic activity of surfaces. The results of the amount of H2O2 production also corroborate with the rest potential of the sulphide minerals; higher the rest potential more is the formation of H2O2. Most likely H2O2 is responsible for the oxidation of sulphide minerals and dissolution of non-ferrous metal sulphides in the presence of ferrous sulphide besides the galvanic interactions.This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between the grinding medium and sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behaviour in the context of the inevitable existence of H2O2 in the pulp liquid.

  • 47. Johansson, Karin
    et al.
    Larsson, C.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Ronin, Vladimir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Reply to the discussion by Knut O. Kjellsen of the paper "Kinetics of the hydration reactions in the cement paste with mechanochemically modified cement: 29Si magic-angle-spinning NMR study"2000In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 30, no 8, p. 1325-1328Article in journal (Refereed)
  • 48.
    Johansson, Karin
    et al.
    Luleå tekniska universitet.
    Larsson, Cecilia
    Luleå tekniska universitet.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ronin, Vladimir
    Kinetics of the hydration reactions in the cement paste with mechanochemically modified cement 29Si magic-angle-spinning NMR study1999In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 29, no 10, p. 1575-1581Article in journal (Refereed)
    Abstract [en]

    A comparative 29Si solid state NMR study of kinetics of the hydration reactions in cement pastes based on rapid-hardening ordinary Portland cement (SH) and on the mechanochemically modified cement (MSH) is presented. The mechanical activation of a cement/silica fume blend in a vibrating mill accelerates the hydration reactions by 15-20%, especially during the initial period of hardening. Variations in relative intensities of 29Si resonances assigned to the hydration products in SH/MSH blends suggest different structures of hydrated SH nets. This can be correlated with a pronounced increase of the MSH-cement binding capacity reported earlier.

  • 49.
    Karlkvist, Tommy
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Patra, Anuttam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bordes, Romain
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Holmberg, Krister
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Rao, Hanumantha
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Flotation selectivity of novel alkyl dicarboxylate reagents for calcite-fluorite separation2016In: Tenside Surfactants Detergents, ISSN 0932-3414, E-ISSN 2195-8564, Vol. 53, no 6, p. 516-523Article in journal (Refereed)
    Abstract [en]

    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 in the study. Experiments using a Hallimond flotation tube showed that although the flotation reagents solely differs 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 potential and the flotation recovery of the mineral particles as afunction of added collector was 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.

  • 50.
    Karlkvist, Tommy
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Patra, Anuttam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Bordes, Romain
    Chalmers University of Technology, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Holmberg, Krister
    Chalmers University of Technology, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Flotation selectivity of novel alkyl dicarboxylate reagents for apatite-calcite separation2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 445, p. 40-47Article in journal (Refereed)
    Abstract [en]

    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 ζ 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 ζ potential and infra-red spectroscopy data

1234 1 - 50 of 170
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf