Darsh T. Wasan1, Alex Nikolov1, and Krishna Vijayaraghavan2. (1) Department of Chemical and Biological Engineering, Illinois Institute of Technology, 10 West 33rd Street, Room 228, Chicago, IL 60616, (2) Conoco-Phillips, Bartlesville, OK 74004
Foaming is of great concern in a number of industrial processes involving three-phase gas-liquid-finely divided solid systems, such as those encountered in the vitrification of highly radioactive nuclear waste slurries and sludges, and food and agrochemicals. Recent work conducted in my laboratory has shown that the surface properties of particles such as hydrophilicity and hydrophobicity are the cause of foamability and foam stability. This paper presents a review of our work including recent experimental results showing that the foaming power of solid particles increases with an increase in the concentration of amphiphilic particles and the degree of foamability correlates well with the particle coverage at the air-liquid surface. However, the foaminess decreases at higher particle concentrations due to the flocculation of amphiphilic particles in the bulk and a maximum in foaminess is observed. A simplified theoretical model based on statistical mechanics is presented which rationalizes the experimental observations.