Derjaguin and Dukhin (1961) developed a theory of flotation by considering the surface forces in the thin liquid films (TLF) of water formed between bubbles and particles. If the forces are net attractive, the pressure of the film becomes negative and hence the film ruptures to form a contact angle. According to the theory, strong electrical double-layer (EDL) forces create force (or energy) barriers that can slowdown the kinetics of flotation. In this presentation, the roles of different surface forces in flotation, including those due to the van der Waals and hydrophobic interactions will be discussed.
