Zeta potential of air bubbles in presence of frothers

Elmahdy, Ahmed M.; Mirnezami, M.; Finch, J.A.

doi:10.1016/j.minpro.2008.09.003

Cited by 91 publications

(37 citation statements)

References 24 publications

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“…Normally, 0 z is a reference point in the charge-free vapor region, ( 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 If we chose a 0 z value of 2.5 nm for pure water system at 300 K, as shown in Figure 2, we obtain a surface potential difference value, φ ∆ , of -600 ± 10 mV which is close to the simulation values reported by other groups 32,43,45 but is significantly larger than the surface potential values reported from air-bubble experiments in the range from -40mV to -65mV 27,46,47 . However, there is another electrical field zero point at z = 3.2 nm as the consequence of the reversal of electrical field in which corresponds to the minimum value of the potentials.…”

Section: Calculation Of Interfacial Potentialmentioning

confidence: 53%

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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Interfacial gas enrichment (IGE) covering the entire area of hydrophobic solid-water interface has recently been detected by atomic force microscopy (AFM) and hypothesized to be responsible for the unexpected stability and anomalous contact angle of gaseous nanobubbles, and the significant change from DLVO to non-DLVO forces. In this paper, we provide further proof of the existence of IGE in the form of a dense gas layer (DGL) by molecular dynamic simulation.Nitrogen gas adsorption at the water-graphite interface is investigated using molecular dynamic simulation at 300 K and 1 atm normal pressure. The results show that a DGL with a density equivalent to a gas at pressure of 500 atm is formed and equilibrated with a normal pressure of 1 atm. By varying the number of gas molecules in the system, we observe several types of dense gas domains: aggregates, cylindrical cap gas domains and DGLs. Spherical cap gas domains form during the simulation but are unstable and always revert to another type of the gas domains.Furthermore, the calculated surface potential of the DGL-water interface, -17.5 mV, is significantly closer to 0 than the surface potential, -65 mV, of normal gas bubble-water interface. This result supports our previously stated hypothesis that the change in surface potential causes the switch from repulsion to attraction for an AFM tip when the graphite surface is covered by an IGE layer. The change in surface potential comes from the structure change of water molecules at the DGL-water interface as compared with the normal gas-water interface. In addition, the contact angle of the cylindrical cap high density nitrogen gas domains is 141degrees. This contact angle is far greater 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 than 85 degrees observed for water on graphite at ambient conditions and much closer to the 150 degrees contact angle observed for nanobubbles in experiments.

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Section: Calculation Of Interfacial Potentialmentioning

confidence: 53%

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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“…The zeta potential of bubbles is known to be negative in circumneutral environments. 33,34) Hence, for consistency with the oatability trend, the zeta potential of the mineral must negatively increase with increasing H 2 O 2 molar ratio. In the present study, however, the H 2 O 2 treatment positively accelerated the zeta potentials of both PbS and CuFeS 2 at both initial pH levels.…”

Section: Causes Of Reduced Oatability In the Presence Of H 2 Omentioning

confidence: 95%

Relationship between Surface Characteristics and Floatability in Representative Sulfide Minerals: Role of Surface Oxidation

et al. 2017

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This study investigates how changes in the surface properties of three representative sul de minerals (galena, sphalerite and chalcopyrite) affect their oatability in the presence of an oxidizing agent (H 2 O 2 ). Tests were conducted at four molar ratios of H 2 O 2 :mineral (0, 0.5, 1.0, and 2.0). To better capture the effect of surface oxidation, the tests were conducted at both acid and basic conditions (i.e., pH = 3 and 10). In all surface property and oatability evaluations, the pH and Eh were equilibrated. The surface properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential measurements and contact angle analyses. The oatability was evaluated by a micro otation method. At the acidic initial pH, galena most sensitively reacted with H 2 O 2 , followed by chalcopyrite and sphalerite, whereas at pH 10, the reactivity differences were insigni cant. H 2 O 2 addition changed the sul de species (initially present on the mineral surface) to sulfate or hydroxyl species, and decreased the mineral oatability. To investigate the surface property that mainly reduced the mineral oatability in the presence of H 2 O 2 , we measured the zeta potentials and contact angles, which are closely associated with the electrostatic and hydrophobic forces, respectively. The oatability depended on the contact angle after the H 2 O 2 addition, implying that the oatability was mainly reduced through oxidation reactions, which increased the hydrophilicity of the mineral surface.

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“…Using Derjaguin approximation, the total double-layer energy, E T e , between the hemisphericalasperity-coated silica sphere and air bubble surface becomes [26]: [29][30][31][32][33]. It should be noted that Equation (4) works best when the closest distance (i.e., h − r) is greater than several Debye lengths due to the linear approximation treatment [26].…”

Section: Theoretical Modelmentioning

confidence: 99%

Role of Collectors and Depressants in Mineral Flotation: A Theoretical Analysis Based on Extended DLVO Theory

et al. 2017

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A theoretical analysis was conducted to study the role of collectors and depressants in flotation, based on the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, where the hydrophobic force is considered. The collector-coated hydrophilic particle and the depressant-coated hydrophobic particle are simplified to a sphere uniformly covered with respectively hydrophobic and hydrophilic nanometer-sized hemispherical asperities of identical radius. Results show that the role of a collector in bubble-particle attachment is to create an attractive hydrophobic force and thus overcome the repulsive van der Waals and electrostatic forces. Moreover, increasing the length of the hydrophobic part of the collector molecule is a more effective way to enhance flotation recovery, compared to increasing the collector concentration. For a depressant, however, its function mechanism is to create a strong electrostatic double-layer force, while the suppression of the hydrophobic force plays a secondary role in decreasing the bubble-particle attachment barrier. The depressant molecule length is also a dominant parameter in designing a powerful depressant.

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Zeta potential of air bubbles in presence of frothers

Cited by 91 publications

References 24 publications

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

Relationship between Surface Characteristics and Floatability in Representative Sulfide Minerals: Role of Surface Oxidation

Role of Collectors and Depressants in Mineral Flotation: A Theoretical Analysis Based on Extended DLVO Theory

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