THE INFLUENCE OF SODIUM DODECYL-SULFATE ON THE SURFACE FREE-ENERGY OF CASSITERITE

Measurements of contact angles for water, glycerol, formamide, diiodomethane, and bromoform on a cassiterite surface covered with sodium dodecyl sulfate (SDS) him were made. The samples of cassiterite were prepared in different ways for the measurements. Using the contact angle values, the Lifshitz-van der Waals and acid-base components of cassiterite/SDS film surface free energy were determined and compared with those for a ''bare'' cassiterite surface. It was found that the contact angle and the components of the surface free energy depend on the pH and concentration of the SDS solution from which the adsorption layer was formed. Also, the method of preparation of cassiterite plates influences these parameters. It was also found that the hydration of the cassiterite surface in the presence of a SDS film takes place and depends on the concentration of SDS, pH, and method of sample preparation, and strongly influences the surface free energy components of cassiterite. (C) 1995 Academic Press, Inc.