Entrapping of Cs and Sr in heat-treated zeolite matrices

A solidification–stabilization procedure aiming at immobilizing Cs+ and Sr2+, two of the radioactive species more frequently present in nuclear power plant wastewaters, was successfully tested. Both cations were simultaneously exchanged by a blend of two zeolites, a phillipsite-rich tuff, selective for Cs+, and a synthetic zeolite Linde-type A, selective for Sr2+. The contaminated material was then heat treated up to 1200 °C with the result of safely immobilizing both cations, as demonstrated by leaching estimation with three different procedures. X-ray studies of the single cation-loaded zeolites or mixture of them helped to interpret the immobilization mechanism, involving cation trapping in chemically stable crystalline/amorphous matrices formed as a result of firing.