[HCG27-P08] Adsorption and co-precipitation behavior of Cs in calcium and potassium silicate hydrateand Cs leaching behavior during their alteration process
Keywords:Geopolymer, Cesium, Adsorption, Co-precipitation, Leaching behavior
In this study, C-S-H and K-S-H were synthesized prior to the experiments. Synthetic method for K-S-H is not clarify. Therefore, metakaolin, calcined kaolinite and water glass are reacted and use it as K-A-S-H because it includes aluminum from metakaolin. From adsorption and co-precipitation experiments, it is obtained that both of C-S-H and K-A-S-H have Cs sorption capacity. About C-S-H, sorption ratio is increased by the decreasing of Ca/Si ratio, and adsorption and co-precipitation ratio are almost same in each Ca/Si ratio. These results are consistent with the previous study. Comparing C-S-H and K-A-S-H, K-A-S-H can sorb high amounts of Cs than C-S-H. The reason of this is considered that the ionic radius of Cs is similar to K than Ca.
From alteration experiment, we can’t see the alteration of C-S-H and K-A-S-H during the reaction period of this study from analysis of solid samples. However, from leaching experiment in deionized water and sea water, a part of adsorbed Cs leach within 1 months. This would be caused by ion exchanging. Comparing C-S-H and K-A-S-H, the leaching ratio of K-A-S-H is lower than it of C-S-H. However, the both of them are considered to not be able to keep Cs for long term because Cs are exchange with cation in solvent. However, C-S-H and K-A-S-H are metastable and they have possibility to incorporate Cs into the structure of stable mineral during alteration. It is therefore important to clarify behavior of Cs during the alteration.