Documents disponibles écrits par cet auteur

Accumulation of dissolved gases at hydrophobic surfaces in water and sodium chloride solutions / Marc A. Hampton in Minerals engineering, Vol. 22 N° 9/10 (Août/Septembre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 9/10 (Août/Septembre 2009) . - pp. 786–792 Titre : Accumulation of dissolved gases at hydrophobic surfaces in water and sodium chloride solutions : Implications for coal flotation Type de document : texte imprimé Auteurs : Marc A. Hampton, Auteur ; Anh V. Nguyen, Auteur Année de publication : 2009 Article en page(s) : pp. 786–792 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Coal  Froth  flotation  Mineral  processing Résumé : Dissolved gases can preferentially accumulate at the hydrophobic solid–water interface as revealed by neutron reflectivity measurements. In this paper, atomic force microscopy (AFM) was used to examine accumulation of dissolved gases at a hydrophobic surface in water and sodium chloride solutions. The solvent-exchange method was used to artificially form gaseous domains accumulated at the interface suitable for AFM imaging. Smooth graphite surfaces were used as model surfaces to minimize the secondary effect of surface roughness on the imaging. The concentration of NaCl up to 1 M was found to have a negligible influence on the geometry and population of pre-existing nanobubbles, nanopancakes and nanobubble–nanopancake composites. The implications of the findings on coal flotation in saline water are discussed in terms of attraction between hydrophobic surfaces in water, bubble–particle attachment and hydrophobic coagulation between particles. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900048X [article] Accumulation of dissolved gases at hydrophobic surfaces in water and sodium chloride solutions : Implications for coal flotation [texte imprimé] / Marc A. Hampton, Auteur ; Anh V. Nguyen, Auteur . - 2009 . - pp. 786–792. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 9/10 (Août/Septembre 2009) . - pp. 786–792 Mots-clés : Coal  Froth  flotation  Mineral  processing Résumé : Dissolved gases can preferentially accumulate at the hydrophobic solid–water interface as revealed by neutron reflectivity measurements. In this paper, atomic force microscopy (AFM) was used to examine accumulation of dissolved gases at a hydrophobic surface in water and sodium chloride solutions. The solvent-exchange method was used to artificially form gaseous domains accumulated at the interface suitable for AFM imaging. Smooth graphite surfaces were used as model surfaces to minimize the secondary effect of surface roughness on the imaging. The concentration of NaCl up to 1 M was found to have a negligible influence on the geometry and population of pre-existing nanobubbles, nanopancakes and nanobubble–nanopancake composites. The implications of the findings on coal flotation in saline water are discussed in terms of attraction between hydrophobic surfaces in water, bubble–particle attachment and hydrophobic coagulation between particles. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900048X

Adsorption and surface tension analysis of concentrated alkali halide brine solutions / Orhan Ozdemir in Minerals engineering, Vol. 22 N° 3 (Fevrier 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 3 (Fevrier 2009) . - pp. 263–271 Titre : Adsorption and surface tension analysis of concentrated alkali halide brine solutions Type de document : texte imprimé Auteurs : Orhan Ozdemir, Auteur ; Stoyan I. Karakashev, Auteur ; Anh V. Nguyen, Auteur Année de publication : 2009 Article en page(s) : pp. 263–271 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Sodium  chloride  and  potassium  chloride  Surface  tension  Water  structure  maker  and  breaker Index. décimale : 622 Industrie minière Résumé : In this study, the equilibrium and dynamic surface tensions of sodium chloride and potassium chloride solutions have been measured as a function of concentration up to saturation (5.2 M for NaCl and 4.1 M for KCl) using sessile bubble tensiometry. The experimental results show that the surface tension of these and other salts significantly increases with increasing concentration due to negative adsorption of ions at the air/brine interface, regardless of their structure maker and breaker nature. Furthermore, the effect of these salts on the surface tension of aqueous solutions of sodium dodecyl sulfate (SDS) and methyl isobutyl carbinol (MIBC) was also studied. These results show that the salts increased the surface activity of SDS and MIBC. In the case of SDS, KCl increased the surface activity of SDS more significantly than NaCl did. In the case of MIBC, the effect of NaCl on MIBC surface activity was more significant than that of KCl. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750800201X [article] Adsorption and surface tension analysis of concentrated alkali halide brine solutions [texte imprimé] / Orhan Ozdemir, Auteur ; Stoyan I. Karakashev, Auteur ; Anh V. Nguyen, Auteur . - 2009 . - pp. 263–271. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 3 (Fevrier 2009) . - pp. 263–271 Mots-clés : Sodium  chloride  and  potassium  chloride  Surface  tension  Water  structure  maker  and  breaker Index. décimale : 622 Industrie minière Résumé : In this study, the equilibrium and dynamic surface tensions of sodium chloride and potassium chloride solutions have been measured as a function of concentration up to saturation (5.2 M for NaCl and 4.1 M for KCl) using sessile bubble tensiometry. The experimental results show that the surface tension of these and other salts significantly increases with increasing concentration due to negative adsorption of ions at the air/brine interface, regardless of their structure maker and breaker nature. Furthermore, the effect of these salts on the surface tension of aqueous solutions of sodium dodecyl sulfate (SDS) and methyl isobutyl carbinol (MIBC) was also studied. These results show that the salts increased the surface activity of SDS and MIBC. In the case of SDS, KCl increased the surface activity of SDS more significantly than NaCl did. In the case of MIBC, the effect of NaCl on MIBC surface activity was more significant than that of KCl. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750800201X

Effect of mechanical and chemical clay removals by hydrocyclone and dispersants on coal flotation / William J. Oats in Minerals engineering, Vol. 23 N° 5 (Avril 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 5 (Avril 2010) . - pp. 413–419 Titre : Effect of mechanical and chemical clay removals by hydrocyclone and dispersants on coal flotation Type de document : texte imprimé Auteurs : William J. Oats, Auteur ; Orhan Ozdemir, Auteur ; Anh V. Nguyen, Auteur Année de publication : 2011 Article en page(s) : pp. 413–419 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Coal  flotation  Slime  Clay  Dispersants  Hydrocyclone  Colloid  stability  DLVO  forces Résumé : Fine minerals, mostly clays, are known to have a detrimental effect on coal flotation. This paper focuses on the effect of mechanical and chemical removals of fine minerals by hydrocyclone and dispersants on coal flotation. The experimental results showed that the flotation recovery slightly increased from medium acidic to medium alkaline ranges. The flotation experiments carried out with dispersants at different dosages showed that the dispersants did not enhance the flotation recovery significantly. However, the removal of the fine fraction from the feed using a hydrocyclone significantly increased the flotation recovery. The bubble–particle attachment tests also indicated that the attachment time between an air bubble and the coal particles increased in the presence of clay particles. These attachment time results clearly showed that the clay particles adversely affected the flotation of coal particles by covering the coal surfaces which reduced the efficiency of bubble–coal attachment. An analysis based on the colloid stability theory showed that the clay coating was governed by the van der Waals attraction and that the double-layer interaction played a secondary role. It was also concluded that the best way to increase the flotation recovery in the presence of clays was to remove these fine minerals by mechanical means such as hydrocylones. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002994 [article] Effect of mechanical and chemical clay removals by hydrocyclone and dispersants on coal flotation [texte imprimé] / William J. Oats, Auteur ; Orhan Ozdemir, Auteur ; Anh V. Nguyen, Auteur . - 2011 . - pp. 413–419. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 5 (Avril 2010) . - pp. 413–419 Mots-clés : Coal  flotation  Slime  Clay  Dispersants  Hydrocyclone  Colloid  stability  DLVO  forces Résumé : Fine minerals, mostly clays, are known to have a detrimental effect on coal flotation. This paper focuses on the effect of mechanical and chemical removals of fine minerals by hydrocyclone and dispersants on coal flotation. The experimental results showed that the flotation recovery slightly increased from medium acidic to medium alkaline ranges. The flotation experiments carried out with dispersants at different dosages showed that the dispersants did not enhance the flotation recovery significantly. However, the removal of the fine fraction from the feed using a hydrocyclone significantly increased the flotation recovery. The bubble–particle attachment tests also indicated that the attachment time between an air bubble and the coal particles increased in the presence of clay particles. These attachment time results clearly showed that the clay particles adversely affected the flotation of coal particles by covering the coal surfaces which reduced the efficiency of bubble–coal attachment. An analysis based on the colloid stability theory showed that the clay coating was governed by the van der Waals attraction and that the double-layer interaction played a secondary role. It was also concluded that the best way to increase the flotation recovery in the presence of clays was to remove these fine minerals by mechanical means such as hydrocylones. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509002994

Validation of the generalised Sutherland equation for bubble–particle encounter efficiency in flotation / Phong T. Nguyen in Minerals engineering, Vol. 22 N° 2 (Janvier 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 2 (Janvier 2009) . - pp. 176–181 Titre : Validation of the generalised Sutherland equation for bubble–particle encounter efficiency in flotation : Effect of particle density Type de document : texte imprimé Auteurs : Phong T. Nguyen, Auteur ; Anh V. Nguyen, Auteur Année de publication : 2009 Article en page(s) : pp. 176–181 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Flotation  bubble  Flotation  kinetics  Froth  flotation Index. décimale : 622 Industrie minière Résumé : Bubble–particle encounter interaction is the first step of the particle collection by rising air bubbles in flotation and has been predicted based on the potential flow condition by Sutherland and others, leading to the approximate generalised Sutherland equation (GSE). In this paper, the bubble–particle encounter interaction with the potential flow condition has been analysed by solving the full motion equation for the particle employing a numerical computational approach. Together with other inertial forces, the gravitational forces were fully included in the motion equation. The numerical results were compared with the GSE models for the encounter efficiency. The effect of particle density on the encounter interaction was very significant and could counterbalance the “negative” effect of the inertial forces on the particle interaction with air bubbles with a mobile surface under the potential flow condition. For the typical particle size range used in flotation, significant deviation of the Sutherland approximate models from the numerical results due to the particle density effect and gravitational forces was observed. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508001660 [article] Validation of the generalised Sutherland equation for bubble–particle encounter efficiency in flotation : Effect of particle density [texte imprimé] / Phong T. Nguyen, Auteur ; Anh V. Nguyen, Auteur . - 2009 . - pp. 176–181. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 2 (Janvier 2009) . - pp. 176–181 Mots-clés : Flotation  bubble  Flotation  kinetics  Froth  flotation Index. décimale : 622 Industrie minière Résumé : Bubble–particle encounter interaction is the first step of the particle collection by rising air bubbles in flotation and has been predicted based on the potential flow condition by Sutherland and others, leading to the approximate generalised Sutherland equation (GSE). In this paper, the bubble–particle encounter interaction with the potential flow condition has been analysed by solving the full motion equation for the particle employing a numerical computational approach. Together with other inertial forces, the gravitational forces were fully included in the motion equation. The numerical results were compared with the GSE models for the encounter efficiency. The effect of particle density on the encounter interaction was very significant and could counterbalance the “negative” effect of the inertial forces on the particle interaction with air bubbles with a mobile surface under the potential flow condition. For the typical particle size range used in flotation, significant deviation of the Sutherland approximate models from the numerical results due to the particle density effect and gravitational forces was observed. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508001660