Weixing Wang

University of Alberta, Edmonton, Alberta, Canada

Are you Weixing Wang?

Claim your profile

Publications (4)8.48 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A phenomenological model is developed to describe the induction time of an air bubble in contact with a hydrophobic sphere, based on an analytical solution of Reynolds approximation under the specific boundary conditions. A modified version of induction time apparatus is used to measure the induction time of an air bubble with a methylated silica bead, an untreated silica bead in dodecylamine solutions and a bitumen droplet in alkaline solutions. It was found that the induction time between an air bubble and a silica bead (or a bitumen droplet) increased with increasing bubble size. The bubble size dependence is stronger for the large silica beads (or bitumen droplets) tested. The induction time, obtained from two different methylated silica beads diameters, is used to estimate the average net driving force (F̄o) for the intervening liquid film drainage and rupture and the critical film thickness (hc) in the established model. Through curve fitting, the values for F̄o and hc are found to be 3.5×10−8 N and 150 nm, respectively, for a methylated silica–bubble system. The predicted values of critical film thickness and the net driving force for the systems used in this study are in excellent agreement with those reported in the literature, confirming the present theoretical analysis and model development. The suitability of using the liquid drainage time to represent the induction time, or the attachment time, is experimentally justified.
    International Journal of Mineral Processing - INT J MINER PROCESS. 01/2005; 75(1):69-82.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A change of oil/water interfacial tension in the presence of cationic or anionic surfactants in an organic phase was observed due to the addition of charged fine solids in the aqueous phase. The charged fine solids in the aqueous phase adsorb surfactants diffused from the oil phase, thereby causing an increase in the bulk equilibrium surfactant concentration in the aqueous phase, governed by the Stern-Grahame equation. Consequently, surfactant adsorption at the oil-water interface increases, which was demonstrated from the measured reduction of the oil-water interfacial tension. The increased surfactant partition in the aqueous phase in the presence of the charged particles was confirmed by the measured decrease in the surface tension for the collected aqueous solution after solids removal, as compared with the cases without solids addition.
    Journal of Colloid and Interface Science 07/2004; 274(2):625-30. · 3.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The sliding velocity of glass beads on a spherical surface, made either of an air bubble or of a glass sphere held stationary, is measured to investigate the effect of surface mobility on the particle sliding velocity. The sliding process is recorded with a digital camera and analyzed frame by frame. The sliding glass bead was found to accelerate with increasing angular position on the collector's surface. It reaches a maximum velocity at an angular position of about 100 degrees and then, under certain conditions, the glass bead leaves the surface of the collector. The sliding velocity of the glass bead depends strongly on the surface mobility of a bubble, decreasing with decreasing surface mobility. By a mobile surface we mean one which cannot set up resistive forces to an applied stress on the surface. The sliding velocity on a rigid surface, such as a glass sphere, is much lower than that on a mobile bubble surface. The sliding velocity can be described through a modified Stokes equation. A numerical factor in the modified Stokes equation is determined by fitting the experimental data and is found to increase with decreasing surface mobility. Hydrophobic glass beads sliding on a hydrophobic glass sphere were found to stick at the point of impact without sliding if the initial angular position of the impact is less than some specific angle, which is defined as the critical sticking angle. The sticking of the glass beads can be attributed to the capillary contracting force created by the formation of a cavity due to spontaneous receding of the nonwetting liquid from the contact zone. The relationship between the critical sticking angle and the particle size is established based on the Yushchenko [J. Colloid Interface Sci. 96 (1983) 307] analysis.
    Journal of Colloid and Interface Science 04/2003; 259(1):81-8. · 3.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A particle–bubble attachment apparatus, similar to that used by Whelan and Brown [Bull. Inst. Min. Met. Trans. 65 (1956) 181] is developed to study free falling glass beads (dp=131 μm) with different surface treatment attaching to a stationary air bubble (db=3 mm). The entire process of the particle–bubble attachment is photographically recorded using a high framing-rate camera and analyzed frame by frame. It is found that the hydrophilic particle slides on the top half of the bubble, and then the particle leaves the bubble, as anticipated. The particle sliding velocity increases with increasing angular position on the bubble surface. For the hydrophobic particle, it was found that the particle slides over the entire bubble surface without detaching from the bubble. The sliding velocity, however, reaches a maximum at an angular position of 90–100°, and then slows down to zero. A smaller sliding velocity is obtained for the hydrophobic particle than that of the hydrophilic particle at a given angular position. The attachment efficiency for the hydrophobic particle reduces with increasing initial angular positions, suggesting that the hydrophobicity alone does not directly guarantee the attachment to a bubble. Adding surfactant (sodium dodecyl sulfate [SDS]) to the test solution makes the hydrophobic particle become less hydrophobic or even hydrophilic, thereby decreasing the attachment efficiency. A much longer induction time is obtained in our present work than that reported in the literature. A simplified particle sliding velocity and attachment model is developed, and a good agreement between the theoretical prediction and experimental measurement is obtained.
    International Journal of Mineral Processing 01/2003; · 1.38 Impact Factor