Moderation of Uncertainty in a Database of Sorption Coefficients (II) Analysis of Data Scatter by Adopting Ion Exchange Model

Abstract

Data scatter found in a database of Cs sorption coe‹cients (K d ) was investigated to demonstrate the usage of the mechanistic sorption model. A large diŠerence found between the data given by the batch sorption and diŠusion experiments was of great interest and the analyses of the pH dependence of the K d by adopting either PHREEQC or the revised version of MINEQL had been carried out to determine the reason for the disagreement among the sorption data. Both of them were able to treat the ion exchange reaction and the surface complexation simultaneously. In particular, the latter was a largely modiˆed form of the original version suitable for the compacted form. The same parameter set was used in the analyses even under extremely diŠerent experimental conditions. The results indicated that the K d for both cases could be reproduced by the model calculation and the perturbation of environmental condition such as the Na concentration, and the pH has a strong in‰uence on the data stability. The results also suggested that the scatter of the K d of Cs could be understandable and minimized through the analysis by adopting the mechanistic sorption models.