Time of gas-solid-liquid three-phase contact expansion in flotation

The elementary step of gas-solid-liquid three-phase contact (TPC) expansion in bubble-particle attachment is theoretically and experimentally investig ated. The TPC expansion is theoretically described using the extended molec ular-kinetic theory [Nguyen, A.V., Stechemesser, ii., Zobel, G., Schulze, H .J., 1997a. Order of three-phase (solid-liquid-gas) contact Line as probed by simulation of three-phase contact line expansion on small hydrophobic sp heres. J. Colloid Interface Sci., 187: 547-550.], which involves the effect of three-phase contact Line tension on the TPC expansion with a small wett ing radius. A theoretical model for the time of the TPC expansion is propos ed and compared with the experimental data. Our data shows that the TPC exp ansion kinetics in flotation is strongly controlled by line tension, along with particle hydrophobicity. This is consistent with the results of the ea rlier investigation of the line tension effect on flotation by Scheludko et al. [Scheludko, A., Toshev, B., Bogadiev, B., 1976. Attachment of particle s to a liquid surface (Capillary theory of flotation). J. Chem. Sec., Farad ay Trans. 1, 72: 2815-2828.]. The line tension obtained in this paper is cl ose to the reported data for similar systems [Li, D., Neumann, A.W., 1990. Determination of line tension from the drop size dependence of contact angl es. Colloids Surfaces, 43: 195-206; Duncan, D., Li, D., Gaydos, J., Neumann , A.W., 1995. Correlation of line tension and solid-liquid interfacial tens ion from the measurements of the drop size dependence of contact angles. J. Colloid Interface Sci., 169: 256-261.] and depends on the interfacial ener gies of the solid-liquid and gas-liquid interfaces. TPC expansion is an imp ortant elementary step in particle-bubble attachment and has to be taken in to consideration in modelling and predicting the probability of particle-bu bble attachment in flotation. (C) 1999 Elsevier Science B.V. All rights res erved.