Distribution coefficients of137Cs and85Sr by mixtures of clay and humic material

Distribution coefficients K_d for the sorption of Cs and Sr on mixtures of a clay mineral (Ca-saturated bentonite) and humic material (Ca-humate) have been measured and were compared with calculated values obtained from the K_d-values observed for the pure components. The concentration of Sr and Cs in the solution was varied between 1·10^–6 and 0.01N and the distribution of the elements determined by using radioactive tracers. All experiments were carried out in pure water as well as in the presence of a supporting electrolyte (0.01N CaCl₂). It was found that the differences between the observed and calculated K_d-values were, if present, always negative if Cs was sorbed, and positive if Sr was sorbed.