Wetting characteristics of hydrophobic minerals in relation to the surface tension of aqueous methanol solutions
Abstract
Results of contact-angle (θ) measurements that have recently been conducted on a number of hydrophobic mineral surfaces as a function of surface tension of aqueous methanol solutions (γlv) are collectively examined. A linear equation of the general form, γlv cos θ=βγlv+(1 –β)γc represents the experimental data. β, the slope and γc, the critical surface tension of wetting, are two parameters that characterize the wettability of the surfaces. The empirical wetting equation is analysed in the light of fundamentals of wetting. The values of the work of adhesion of water obtained from this analysis are compared with those calculated from the classical work-of-adhesion equation, i.e.Wa°sw2=γw2(1 + cos θw) where γw is surface tension of water and θw is the contact angle of water on the mineral sample . For a wide range of samples it has been found that the two work-of-adhesion values agree to within ± 0.7 mJ m–2.