| 1. |
- Arkhipov, Victor, et al.
(författare)
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Micelle structure and molecular self-diffusion in isononylphenol ethoxylate–water systems
- 2013
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 51:7, s. 424-430
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Tidskriftsartikel (refereegranskat)abstract
- The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated
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| 2. |
- Arkhipov, Victor P., et al.
(författare)
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Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point
- 2014
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:20, s. 5480-5487
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Tidskriftsartikel (refereegranskat)abstract
- We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols - C9H19C6H 4O(C2H4O)nH, where n = 6, 8, 9, 10, or 12 - in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols
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| 3. |
- Dobryden, Illia, et al.
(författare)
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Application of AFM to probe micro- and nano-sized magnetite particle interaction in Ca2+ solution
- 2014
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Ingår i: Proceedings of the International Summer School on Application of Scanning Probe Microscopy in Life Sciences, Soft Matter and Nanofabrication". - Aalborg : River Publishers. - 9788793102330
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Natural magnetite is used for producing iron ore pellets, one of the raw materials in steel production. The quality of produced pellets depends on many factors, including the properties of the magnetite concentrate fed to pelletization. To be able to minimize the effect of the variations in feed properties on pellets quality, investigation of magnetite particle interaction with a focus on the surface properties is required. Atomic force microscopy (AFM), using the colloidal probe technique, is a suitable tool for measuring such particle-particle interaction in-situ. Natural particles are usually of micro-sizes (m-s) and have different sizes and shapes, which complicates an accurate investigation of particle interaction with AFM. To overcome such difficulties, synthetic nanoparticles are used instead. Process water chemistry is one of the factors affecting magnetite surface properties. Partial dissolution of calcite and apatite minerals, present in iron ore, results in high Ca2+ concentrations in the process water, which has been shown to have a major effect on the charge of the magnetite particles [1, 2]. The aim of this study was therefore to investigate forces and aggregation between magnetite particles, of micro- and nano-size (n-s), in Ca2+ solutions at various pH values. The spherical monodispersed magnetite nano-sized particles, with a diameter of approx. 10 nm, were synthesized by the precipitation technique [3]. Measurements were performed for m-s probe/m-s layer and m-s probe/n-s layer systems. Natural magnetite particles of 10-30 µm size were glued to NP-S cantilevers (Digital Instruments/Bruker, Santa Barbara, CA) with a measured spring constant of 0.12 N/m. Nano-sized particles were deposited on the glass slides by dip-coating. Roughness (Ra) of the n-s layers was measured with AFM and was about 10 nm for areas 1×1µm2, a representative high-resolution image is shown in Figure 1. Particle interaction was similar for m-s and n-s magnetite particles at pH 4 and 6. At pH 10, the interaction behavior was different due to probable surface modification of natural magnetite particles by ions from process water. The adhesion force for both interacting systems was measured, see ref. [4] for a detailed description of the results. To verify that ϛ-potential measurements could be used to predict the interaction between charged particles (in this case silica and magnetite) in solutions containing inorganic ions, force measurements between n-s magnetite layer and a SiO2 spherical probe (3.5 µm in diameter) were performed and correlated with the ϛ-potential results for these particles in the same solutions. Also, a DLVO simulation was performed to theoretically confirm the experimental interaction based on surface charge trends. An example of the simulated force curves is shown in Figure 2. The interaction between the probe and the magnetite surface was attractive at pH 4 and 6 but became repulsive at pH 8 and 10, which is in agreement with what could be expected from the ϛ-potential results for these particles.
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| 4. |
- Dobryden, Illia, et al.
(författare)
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Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy
- 2015
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Ingår i: Physics and chemistry of minerals. - : Springer Science and Business Media LLC. - 0342-1791 .- 1432-2021. ; 42:4, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle–particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite–magnetite, bentonite–magnetite, silica–bentonite, and silica–magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite–magnetite and bentonite–silica systems and slightly increased for the magnetite–bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite–silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.
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| 5. |
- Farzaneh, Amirfarrokh, et al.
(författare)
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Adsorption of Water and Butanol in Silicalite-1 Film Studied with in-situ ATR-FTIR Spectroscopy
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:17, s. 4887-4894
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Tidskriftsartikel (refereegranskat)abstract
- Biobutanol produced by, e.g., acetone–butanol–ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35–120 °C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 °C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.
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| 6. |
- Farzaneh, Amirfarrokh, et al.
(författare)
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Adsorption of Water and Butanol in Silicalite-1 Film Studied with in Situ Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:17, s. 4887-4894
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Tidskriftsartikel (refereegranskat)abstract
- Biobutanol produced by, e.g., acetone-butanol-ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35-120 degrees C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 degrees C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.
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| 7. |
- Potapova, Elisaveta
(författare)
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Adsorption of surfactants and polymers on iron oxides : implications for flotation and agglomeration of iron ore
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Iron ore pellets are an important refined product used as a raw material in the production of steel. In order to meet the requirements of the processes for iron production, the iron ore is upgraded in a number of steps including, among others, reverse flotation. Under certain circumstances the flotation collector may inadvertently adsorb on the iron ore particles increasing the hydrophobicity of the iron ore concentrate, which in turn has been shown to have an adverse effect on pellet strength. To minimize the influence of the collector on pellet properties, it is important to understand the mechanism of collector adsorption on iron oxides and how different factors may affect the extent of adsorption. In Papers I-III, the adsorption of a commercial anionic carboxylate collector Atrac 1563 and a number of model compounds on synthetic iron oxides was studied in-situ using attenuated total reflectance Fourier transforms infrared (ATR-FTIR) spectroscopy. The effect of surfactant concentration, pH, ionic strength, calcium ions and sodium silicate on surfactant adsorption was investigated. The adsorption mechanism of anionic surfactants on iron oxides at pH 8.5 in the absence and presence of other ions was elucidated. Whereas silicate species were shown to reduce surfactant adsorption, calcium ions were found to facilitate the adsorption and precipitation of the surfactant on magnetite even in the presence of sodium silicate. This implies that a high concentration of calcium in the process water could possibly enhance the contamination of the iron ore with the flotation collector. In Paper III, the effect of calcium, silicate and a carboxylate surfactant on the zeta-potential and wetting properties of magnetite was investigated. It was concluded that a high content of calcium ions in the process water could reduce the dispersing effect of silicate in flotation of apatite from magnetite. Whereas treatment with calcium chloride and sodium silicate made magnetite more hydrophilic, subsequent adsorption of the anionic surfactant increased the water contact angle of magnetite. The hydrophobic areas on the magnetite surface could result in incorporation of air bubbles inside the iron ore pellets produced by wet agglomeration, lowering pellet strength.Based on the adsorption studies, it was concluded that calcium ions could be detrimental for both flotation and agglomeration. Since water softening could result in further dissolution of calcium-containing minerals, an alternative method of handling surfactant coatings on magnetite surfaces was proposed in Paper IV. It was shown that the wettability of the magnetite surface after surfactant adsorption could be restored by modifying the surface with polyacrylate or sodium silicate. In Paper V, the results obtained using synthetic magnetite were verified for natural magnetite. It was illustrated that the conclusions made for the model system regarding the detrimental effect of calcium ions were applicable to the natural magnetite particles and commercial flotation reagents. It was confirmed that polyacrylate and soluble silicate could be successfully used to improve the wettability of the flotated magnetite concentrate. The fact that polyacrylate improved the wettability of magnetite more efficiently at the increased concentration of calcium ions indicates that this polymer is a good candidate for applications in hard water.Finally, it was concluded that in-situ ATR-FTIR spectroscopy in combination with zeta-potential and contact angle measurements could be successfully applied for studying surface phenomena related to mineral processing.
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| 8. |
- Potapova, Elisaveta, et al.
(författare)
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In-situ spectroscopic study of surfactants adsorption onto hematite from binary mixtures and the effect of inorganic ions
- 2014
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Ingår i: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 46:10-11, s. 1110-1114
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Tidskriftsartikel (refereegranskat)abstract
- Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has proven to be a powerful tool for surfactant adsorption studies. In many practical applications, surfactant mixtures and waters with different chemistry are employed, which significantly complicates adsorption studies. In this work, we investigate the effect of calcium and carbonate ions, frequently found in natural waters, on the co-adsorption of sodium dodecylbenzenesulfonate (SDBS) and a non-ionic primary alcohol ethoxylate (NEODOL 25–7) onto hematite at pH 8 and 10.5 using ATR-FTIR spectroscopy. Adsorption of SDBS was affected by pH and the presence of inorganic ions to a greater extent than the adsorption of NEODOL 25–7. A larger amount of SDBS was adsorbed at pH 8 than at pH 10.5 in all the experiments. The effect of co-adsorbing ions on the amount of SDBS adsorbed was significant only at pH 10.5 and not at pH 8. Calcium ions promoted adsorption of SBDS onto hematite, whereas addition of carbonate decreased the amount of SDBS adsorbed. In the presence of both calcium and carbonate ions, calcium carbonate precipitate was formed on the hematite surface, promoting accumulation of NEODOL 25–7 at the surface. NEODOL 25–7 was found to have a strong effect on the hydrophilicity of the hematite film when adsorbed in combination with SDBS. A more hydrophilic surface was obtained upon adsorption of the surfactants in the presence of sodium chloride, film dispersion occurred in the presence of calcium chloride, and a less hydrophilic surface was obtained in the presence of both calcium chloride and sodium carbonate
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| 9. |
- Potapova, Elisaveta, et al.
(författare)
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Interfacial properties of natural magnetite particles compared with their synthetic analogue
- 2011
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Ingår i: 5th International Flotation Conference 2011. - Red Hook : Curran Associates, Inc.. - 9781618393951
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Konferensbidrag (refereegranskat)abstract
- Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in-situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such assilicate or polyacrylate.
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| 10. |
- Potapova, Elisaveta, et al.
(författare)
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Interfacial properties of natural magnetite particles compared with their synthetic analogue
- 2012
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 36-38:S1, s. 187-194
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Tidskriftsartikel (refereegranskat)abstract
- Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such as silicate or polyacrylate.
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