HYDROLYSIS REACTIONS IN SODIUM‐MONTMORILLONITE SUSPENSIONS

Abstract

Summary Explanation of the hydrolysis of Na‐montmorillonite in NaCl solutions if based on Donnan equilibria, the order of the hydrolysis reaction, and CO 2 –H 2 O‐NaCl‐NaOH equilibria. Equations describe quantitatively the extent of hydrolysis as a function of per cent clay in suspension, and initial NaCl concentration. Lack of fit between experimental and calculated Na + and H • activities is attributed predominantly to lack of equilibrium with atmospheric CO 2 in the first stages of the reaction, and thereafter to secondary reactions due to chemical instability of protonized clay, when H + activity continuously decreases. The presence of CaCO 3 in natural clay samples leads to pH values 1 to 2 units higher than those due only to hydrolysis.