The adsorption of low molecular weight poly-(acrylic acid) (PAA) from
aqueous solutions on TiO2 (anatase) has been studied and at pH 10 as a
function of the electrolyte type and concentration. At low pH an exot
hermic heat of adsorption is found but at high pH in CaCl2 and NaCl so
lutions heat is consumed during adsorption. This endothermic effect is
related to specific interactions between the cations and the TiO2 sur
face. If a Ca-salt is used the endothermic effect also originates from
Ca2+ PAA interactions. The most likely driving force for PAA adsorpti
on on TiO2 at high pH is the entropy gain by the release of hydration
water of specifically interacting ions. (C) 1994 Academic Press, Inc.