In 1961, Derjaguin and Dukhin developed a kinetic model for the bubble-particle interactions in flotation using the classical DLVO theory. Their study was the first to derive a bubble-particle interaction model from first principles by considering the surface forces present in the thin liquid films of water (or wetting films) formed between the two macroscopic surfaces. According to the model they developed, the energy barrier (E1) to the bubble-particle interaction (or flotation) should increase with the square of particle ζ-potentials, which creates repulsive electrical double-layer (EDL) forces that stabilize the wetting films. An implication of their work was that one can improve flotation recovery by the reducing the ζ-potentials of mineral particles to minimize the energy barriers. In 1972, Professor Fuerstenau’s group at Berkeley validated the model prediction by showing that the flotation recovery of molybdenite (MoS2) reached a maximum when the particle ζ-potential was reduced to zero.
In the flotation industry, the energy barriers to bubble-particle interactions are reduced by using hydrophobizing agents (known as collectors) to create attractive hydrophobic forces that can counterbalance the repulsive EDL forces. Professor Roe-Hoan Yoon and Kaiwu Huang (Research Associate) developed a new method of reducing energy barriers, in which appropriate surfactants are used to reverse the ζ-potentials of air bubbles and create attractive EDL forces in wetting films. The two scientists conducted a series of surface force measurements to demonstrate that the kinetics of film thinning accelerates when the EDL forces become attractive and that the induction time for bubble-particle interaction is shortened by more than an order of magnitude. The force measurements were conducted using the force apparatus for deformable surfaces (FADS) developed previously in their research group at Virginia Tech.
In summary, the fundamental study resulted in the development of a new way to increase the kinetics of flotation and greatly improve minerals recovery. In a statement to Advances in Engineering, Professor Roe-Hoan Yoon highlighted that their findings laid a foundation to develop novel flotation reagents and to design more efficient flotation machines in the future.
Kaiwu Huang, Roe-Hoan Yoon. Control of bubble ζ-potentials to improve the kinetics of bubble-particle interactions. Minerals Engineering, volume 151 (2020) 106295.