Use of calorimetric titration to determine thermochemical data for interaction of cations with mercapto-modified silica gel

Interactions occurring between mercapto-modified silica gel and silver, mer cury, copper and zinc ions in ethanolic solutions have been investigated by using calorimetric titrations with direct determination of the reaction ex tension. A calorimetric technique is described for the simultaneous determi nation of thermal effects acid quantities of cations that interact at each titration point. From this procedure, values of maximum capacity of interac tion (N-s), differential interaction enthalpies at different coverages of t he surface (Delta(int(i))H-m), integral energy of interaction (Q(mon)) and molar integral enthalpy of interaction for a monolayer (Delta(mon)H(m)) hav e been obtained. The maximum capacity of interaction values are compared wi th those previously published for analogous interaction processes in aqueou s solutions. Thermochemical quantities are discussed in terms of evaluation criterion of the acid-base interactions, and generally support the conclus ion that the Pearson's hypothesis of hard and soft acids and bases is appro priated to describe the behavior of the interaction of the above-mentioned cations. (C) 1999 Published by Elsevier Science B.V. All rights reserved.