The Physical Chemistry of Flotation. I. The Significance of Contact Angle in Flotation.

Wark, Ian William

doi:10.1021/j150347a008

Cited by 66 publications

(14 citation statements)

References 2 publications

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“…On the basis of the work of Bashforth ( 3 ) and Wark (28), Fritz (12) obtained a semiempirical relationship for the diameter of a bubble breaking off the heating surface which showed good agieement with the experimental results of Jakob (17) and Kabanow and Frumukin (18). From a photographic study Jakob (16) discovered that the product of bubble diameter and the frequency of bubble formation seemed to be constant at small heat fluxes.…”

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confidence: 86%

The effects of superheat and surface roughness on boiling coefficients

1960

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The effects of liquid superheat and surface roughness on boiling coefficients were investigated in a series of experiments in which water, acetone, n-hexane, carbon tetrachloride, and carbon disulfide were boiled on a flat plate. In addition to the usual thermal measurements, the number of active boiling centers was determined, whenever possible, by visual means, and a quantitative measure of surface roughness was made. It was found that the number of active boiling centers on the plate increased with increasing surface roughness and that the calculated boiling coefficients were proportional to the one-third power of the number of bubble columns rising from the heated surface.An equation has been derived relating boiling coefficients to fluid properties and the number of active boiling centers on a surface. A second equation, based on the theory of thermal fluctuations, has been proposed to relate the number of active boiling centers to the independent variables of surface-roughness and temperature-difference driving force. The limited data available have been found to follow this proposed relation. The results of this work suggest a quantitative method of relating the boiling coefficient to the character of the surface which may explain the discrepancies observed in the slopes of boiling curves reported in the literature and in the actual values reported for the boiling coefficients measured on different surfaces. H. M. Kurihara is with

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confidence: 86%

The effects of superheat and surface roughness on boiling coefficients

1960

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“…Coarse particles, whether they are of one type or composite, can be detached from the bubble surface (Crawford and Ralston, 1988). After attachment, two conditions are necessary for flotation: aggregate stability and buoyancy (Wark, 1933).…”

Section: Introductionmentioning

confidence: 99%

The Limits of Fine and Coarse Particle Flotation

2007

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the aqueous phase and the air bubble (Gaudin, 1957). It is accepted that the higher the contact angle of a mineral surface, the more readily it is wetted by air, and is thus more hydrophobic (Lucassen-Reynders and Lucassen, 1984;Gaudin, 1957). Particle hydrophobicity or contact angle is dependent on the type and distribution of species present on the mineral surface (Crawford et al., 1987). Generally, the mineral particle surface may be covered with hydrophobic (e.g. collector, polysulphide) and hydrophilic species (oxide, hydroxide, and sulphate) as well as with different mineral phases, as found in composite particles (Prestidge and Ralston, 1995). Recovery decreases with increasing particle size because of detachment and decreases at small particle sizes due to inefficient collision (Dai et al., 2000).The flotation behaviour of quartz particles was studied over the particle size range from 0.5 µm to 1000 µm and for advancing water contact angles between 0º and 83º. Flotation was performed in a column and in a Rushton turbine cell. Particle contact angle threshold values, below which the particles could not be floated, were identified for the particle size range 0.5-1000 µm, under different hydrodynamic conditions. The flotation response of the particles, either in a column or in a mechanically agitated cell with a similar bubble size, was comparable. Turbulence plays a role, as does bubble-particle aggregate velocity and bubble size. The stability of the bubble-particle aggregate controls the maximum floatable particle size of coarse particles. For fine particles, the flotation limit is dictated by the energy required to rupture the intervening liquid film between the particle and bubble. Flotation of very fine and large particles is facilitated with small bubbles and high contact angles. These results greatly extend our earlier observations and theoretical predictions.On a étudié le comportement de flottation de particules de quartz pour des tailles de particules comprises entre 0,5 µm et 1000 µm et des angles de contact de l'eau de 0º et 83º. La flottation a été réalisée dans une colonne et dans une cellule munie d'une turbine Rushton. Les valeurs de seuils des angles de contact, en dessous desquels les particules ne pouvaient pas flotter, ont été identifiées pour une gamme de particules de 0,5-1000 µm, dans différentes conditions hydrodynamiques. La réponse de flottation, dans une colonne ou dans une cellule agitée mécaniquement avec une taille de bulles similaire, est comparable. La turbulence exerce une influence, tout comme la vitesse des agrégats de bulles et de particules et la taille des bulles. La flottation des particules très fines et des particules larges est facilitée avec des bulles petites et des angles de contact élevés. Ces résultats élargissent de façon importante nos observations et prédictions théoriques antérieures.

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“…In this case the diameter of the drop is only a function of its volume and the contact angle [14][15][16][17]:…”

Section: Introductionmentioning

confidence: 99%

Surface Energy and Adhesion in Composite–Composite Adhesive Bonds

Dillingham

Oakley

2006

The Journal of Adhesion

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In the absence of weak boundary layers, surface energy can be an excellent indicator of the suitability of a fiber-reinforced composite surface for adhesive bonding. Mechanical surface treatments such as grit blasting are effective and commonly used to prepare composite surfaces, but the roughness introduced by these treatments makes quantification of the surface energy by contact angle methods difficult. This paper shows that the diameter of a small drop of a low-viscosity fluid chosen to have surface tension characteristics very similar to the adhesive can be used as an effective predictor of adhesive bond fracture energy. This technique could form the basis of a sensitive quality assurance tool for manufacturing.

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The Physical Chemistry of Flotation. I. The Significance of Contact Angle in Flotation.

Cited by 66 publications

References 2 publications

The effects of superheat and surface roughness on boiling coefficients

The effects of superheat and surface roughness on boiling coefficients

The Limits of Fine and Coarse Particle Flotation

Surface Energy and Adhesion in Composite–Composite Adhesive Bonds

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