The influence of ionic strength on the dissolution process of silica

A general dissolution model for oxidic solids in water has been suggested. To confirm this model the dissolution kinetics of well-defined silica spher es is determined dependent on pH and ionic strength at 40 degrees C. By ana lyzing dissolution data it is possible to study electrical double layer pro perties. In this approach, the charge state of the oxide is described by ap plication of a diffuse layer model. From a theoretical point of view, some important, general conclusions for the overall rate constant of dissolution , consisting of three partial rate constants, may be drawn. The characteris tic parameters such as the pristine point of zero charge, the,acidity const ants of the surface groups, the saturation concentration, and the partial r ate constants, could be determined precisely. Experimental results for two different types of silica are compared. The model is able to elucidate well the dissolution behavior as a function of time, pH and ionic strength. (C) 1999 Elsevier Science B.V. All rights reserved.