A METHOD FOR THE DETERMINATION OF THE ACID-BASE INTERACTIONS AND THE WORK OF ADHESION AT A SOLID LIQUID INTERFACE

A new method for determination of the work of adhesion at a solid-liquid interface is described in this paper. The method is based on the ideas of Fowkes, who showed that the total work of adhesion W(SL) could be reduced to two kinds of interactions, namely, W(SL)D due to the dispersion or London forces, and W(SL)AB due to the non-dispersion or acid-base interactions: W(SL) = W(SL)D + W(SL)AB. The method makes use of the classical contact angle technique (sessile drop or Wilhelmy method). The novel feature of our approach is the determination of the work of adhesion W(SL) using aqueous acidic and basic solutions as test liquids in the pH range from 1 to 14. By this procedure, well-defined acid-base complexes between the functional groups at the surface of the solid and the aqueous solutions of varying pH value can be formed. As a consequence, different values for the work of adhesion W(SL)AB are obtained, which can be derived from the enthalpy of the specific acid-base complexes and their surface concentration: W(SL)AB = -SIGMA-f(i)n(i)(AB)DELTA-H(i)AB.