Characterization of the wettability of solid particles by film flotation 2. Theoretical analysis

Diao, J.; Fuerstenau, D.W.

doi:10.1016/0166-6622(91)80274-r

Cited by 32 publications

(16 citation statements)

References 10 publications

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“…It was shown using film flotation and zeta potential measurements that the maximum flotation response for coal occurs close to its isoelectric point (Fuerstenau et al, 1983;Diao and Fuerstenau, 1991). The work of Harvey et al (2002), where the effect of electrolyte (NaCl and MgCl 2 ) concentrations on coal flotation was investigated using a modified Hallimond tube, supported this observation.…”

Section: Effect Of Water Chemistry On Coal Flotationsupporting

confidence: 57%

Physical and chemical interactions in coal flotation

Polat

Chander

2003

International Journal of Mineral Processing

191

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Coal flotation is a complex process involving several phases (particles, oil droplets and air bubbles). These phases simultaneously interact with each other and with other species such as the molecules of a promoting reagent and dissolved ions in water. The physical and chemical interactions determine the outcome of the flotation process. Physical and chemical interactions between fine coal particles could lead to aggregation, especially for high rank coals. Non-selective particle aggregation could be said to be the main reason for the selectivity problems in coal flotation. It should be addressed by physical (conditioning) or chemical (promoters) pretreatment before or during flotation. Although the interactions between the oil droplets and coal particles are actually favored, stabilization of the oil droplets by small amounts of fine hydrophobic particles may lead to a decrease in selectivity and an increase in oil consumption. These problems could be remedied by use of promoters that modify the coal surface for suitable particle -particle, droplet -particle and particle -bubble contact while emulsifying the oil droplets. The role of promoters may be different for different types of coals, however. They could be employed as modifiers to increase the hydrophobicity of low rank coals whereas their main role might be emulsification and aggregation control for high rank coals. In this paper, a detailed description of the various phases in coal flotation, their physical and chemical interactions with each other in the flotation pulp, the major parameters that affect these interactions and how these interactions, in turn, influence the flotation process are discussed. D

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Section: Effect Of Water Chemistry On Coal Flotationsupporting

confidence: 57%

Physical and chemical interactions in coal flotation

Polat

Chander

2003

International Journal of Mineral Processing

191

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“…dry. The interfacial free energy gained for single a spherical particle transferred from the air to the liquid surface is given by 38,39 DF ¼ g l pr p 2 (1 + cos q) 2 (7) Fig. 4 Dependence of (a) the height of the particle coating, h p , normalised with the droplet height, h d , and (b) droplet penetration time, s, on the particle wettability, q, for drops placed on packed beds of hydrophobic glass spheres: 98 mm (circular points) and 42 mm (triangular points).…”

Section: Discussionmentioning

confidence: 99%

Spontaneous liquid marble formation on packed porous beds

2012

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The encapsulation of aqueous and organic solvents with particles used to form liquid marbles implies there are attractive interactions between the particles and those different liquids. This is often masked, however, by the impact of the droplet kinetic energy on marble formation. We investigated droplet wetting and evaporation when drops were gently placed (without rolling or shaking) on beds of silanised glass beads. Particle coating of the drop surface occurred within seconds of liquid contact with the particle bed. This ruled out evaporation from causing the particles to appear to rise up the surface of the drop as it was reduced in volume. Particles attach to the fresh liquid surface created during the droplet oscillations immediately after contact. The further ordered advance of the particles over the drop surface and the close-packed arrangement of the particles revealed the role of capillary forces in the coating process. By minimising the kinetic energy of the droplet contact with the particles, we found that maximum particle coating occurs at liquid surface tensions just above the critical wetting tension of the beads.

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“…The film flotation method Diao and Fuerstenau, 1991) was used to measure the water contact angle of the particles, based on their critical surface tension, γ cr (Zisman, 1964). γ cr is equal to the surface tension of the liquid, γ LV , when the particles are just wetted by the liquid.…”

Section: Film Flotation Technique For Contact Angle Determinationmentioning

confidence: 99%

“…The portion of particles that sink is defined as the hydrophilic fraction and those which are retained at the surface (i.e. float) is the hydrophobic fraction (Williams and Fuerstenau, 1987;Fuerstenau et al, 1991;Diao and Fuerstenau, 1991;Mather and Taylor, 1999). In a mixture of particles displaying different wettabilities, there is potential for selective particle separation by exploiting differences in wettability.…”

Section: Introductionmentioning

confidence: 99%