Improvement of metakaolin on radioactive Sr and Cs immobilization of alkali-activated slag matrix

摘要

Effects of metakaolin on simulated radioactive Sr or Cs immobilizing behavior of alkali-activated slag (AAS) matrix were evaluated by cation exchange capacity (CEC), distribution ratio of selective adsorption, leaching test and porosity analyses. The results revealed that the additions of metakaolin into the AAS matrixes largely enhanced their distribution ratios K_d of selective adsorption on Sr and Cs ions. Meanwhile, this new immobilizing matrix M-AAS showed the lowest leaching rate. Hydra-tion product analyzes by XRD, DTA, FTIR and SEM demonstrated that (Na + Al)-substituted calcium silicate hydrate (CSH) and self-generated zeolite were major hydration products in the M-AAS matrix. These products have better Sr and Cs selective adsorption as compared to C-S-H without any substitution and natural zeolite minerals.