Characterization of coal particle surfaces by film flotation

Because of the heterogeneity of coal, particles may vary in composition and, consequently, each particle may have its own unique set of surface properties. The distribution of surface properties of coal particles was determined through film flotation with a series of aqueous methanol solutions. This paper shows how such measurements of the critical wetting surface tension can be used to determine the contact angle of particles and the distribution of lyophobic sites on the surface of the particles. The mean contact angles calculated from film flotation results for sulfur, graphite and a number of different coals are in reasonable agreement with the values reported in the literature.