Determination of Cation Exchange Capacity of Earth Materials Using a Radiotracer Technique

摘要

Two radiochemical methods were investigated for determining the cation exchange capacity of earth materials having a wide range in physicochemical properties. The first method attempted was unsuccessful but involved determination of the radioactivity of a 22Na-NaOAc solution in isotopic equilibrium with a Na(+)-saturated mineral phase. The logic of this method is presented in order to illustrate principles of isotopic exchange in mineral systems. The method finally adopted is based upon determination of the radioactivity of a salt-free, Na(+)-saturated mineral sample prepared using a radioactive NaOAc solution with a known 22Na-NaOAc composition. This method is less time-consuming and more accurate than the conventional ammonium acetate method for cation exchange capacity determinations. (Author)