Prediction of van der Waals interaction in bubble-particle attachment in flotation

van der Waals interaction is one component of the surface force interactions, which control bubble-particle attachment in flotation. In this paper, approximations to Lifshitz theory are developed to estimate the van der Waals interaction energy vs. separation distance between a bubble and a particle. The dielectric spectrum of the mineral particles is approximately represented using a three-parameter model involving the refractive index and the dielectric constant of minerals, The effects on the van der Waals interaction of electromagnetic retardation and electrolyte screening are estimated, The approximations yield simple predictions for the Hamaker constant and the Hamaker function, which are convenient for the modelling of the micro-processes of the bubble-particle attachment. The approximate predictions agree with the results computed from rigorous Lifshitz theory using the complete dielectric spectra. The analysis shows that van der Waals interaction in the bubble-particle attachment is affected by electromagnetic retardation (the dispersion interaction only) and electrolytes (the dipolar interactions only), and can be predicted using the refractive index of mineral particles. (C) 2001 Elsevier Science B.V. All rights reserved.