THE INFLUENCE OF PARTICLE-SIZE AND HYDROPHOBICITY ON THE STABILITY OF MINERALIZED FROTHS

The influence of quartz particles (of well defined size fractions with different degrees of hydrophobicity) on the stability of froths was studied by dynamic and static froth experiments using a froth column. For a 26-44-mu-m particle size fraction, it was found that with particles with an intermediate degree of hydrophobicity (corresponding to a contact angle of almost-equal-to 65-degrees for a sessile drop of water on a quartz plate) both the "dynamic" and the "static" froth stability was maximized. Particles in the more hydrophilic range did not appear to influence the froth properties but more hydrophobic particles destabilized the froth. For larger particles (74-106-mu-m) these effects were found to be much less pronounced. From microinterferometric studies made on thin aqueous films (30-100 nm), the increase in stability was explained by the particles streaming along the air/solution interface of the lamellae during drainage of the film. The effect of the particles concentrating along the edges of the Plateau border. appeared lo increase the rigidity of the interface and hence the stability of the structure. Particles of greater hydrophobicity penetrated the interface to a much greater extent and ruptured the film, suppressing foam stability. Particles of lower hydrophobicity remained dispersed in the lamellae and appeared to have little influence on the stability of the froths.