Electrical Aspects of Adsorbing Colloid Flotation. VII. Cooperative Phenomena

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Abstract
Flotation is assumed to occur when a condensed film of surfactant forms on the particles to be floated, making their surfaces hydrophobic and permitting bubble attachment. This hemi-micelle formation is a cooperative phenomenon resulting from van der Waals forces between the hydrocarbon tails of the surfactant ions. The effects of temperature, ionic strength, and particle surface potential are examined by means of a statistical mechanical approach described by Fowler and Guggenheim. The effect of hemi-micelle formation at the air-water interface on the efficiency of flotation by a coulombic mechanism is also examined. Increasing temperature increases the surfactant concentration necessary for flotation; increasing ionic strength decreases this critical surfactant concentration, but also decreases the magnitude of the air-water surface potential, which decreases flotation efficiency.