Sequestration of Cesium and Strontium by Tobermorite Synthesized from Fly Ashes

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Abstract
Tobermorites were synthesized from oxides and from fly ashes under mild hydrothermal conditions. The bulk compositions of the ash‐based formulations were adjusted to give the same [Ca]/[Si + Al] ratio as for the oxides. Selective Cs and Sr exchange with these tobermorites was measured. Compared to those prepared from the oxides and from class C fly ash, the tobermorites obtained from class F fly ash exhibited superior Cs and Sr selective properties. This is apparently a result of more extensive Al incorporation with class F fly ash. For example, tobermorite synthesized from class F fly ash exhibited a cesium Kd (mL/g) of 3826 while those prepared from oxides and from class C fly ash showed Kd values of 1112 and 796, respectively, under the same conditions. These results suggest that fly ash waste materials can be converted into tobermorite, which can serve as a resource in the separation, immobilization, and disposal of radioactive species such as Cs and Sr.