Zeolites have been studied and used consistently as ion-exchanger for application in radioactive liquid waste treatment due to its high exchange capacity, possible selectivity and specificity, and good resistant to radiation. Therefore, in view of the potential application of zeolite for the removal of Cs radionuclide from radioactive wastewater, an understanding of the Cs selectivity of zeolite is more important than anything else. This study was performed to study the site selectivity and the cation-sieve effect of Cs+ and Na+ ions within the zeolite A and to investigate the tendency of Cs+-exchange by the change of concentration of Cs+ and Na+ in ion exchange solution. Three single-crystals of fully dehydrated Cs+ and Na+ exchanged zeolite A were prepared by the static ion-exchange method using a mixed ion-exchange solution whose CsNO3:NaNO3 mole ratios were 1:11 (crystal 1), 1:2 (crystal 2) and 2:1 (crystal 3), respectively, with a total concentration of 0.1 M, followed by vacuum dehydration at 623 K and 1.33 × 10-4 Pa. Their structures were refined to the final error indices R1/wR2 = 0.0577/0.1555, 0.0575/0.1822 and 0.0496/0.1465 for crystals 1, 2, and 3, respectively. In the structure of |Cs2Na10|[Si12Al12O48]-LTA (crystal 1), 2 Cs+ ions per unit cell occupy large cavity, whereas, the remaining 10 Na+ ions occupy sodalite unit. In the structure of |Cs3.5Na8.5|[Si12Al12O48]-LTA (crystal 2), 3.5 Cs+ ions per unit cell are located in the large cavity. 8.5 Na+ ions are located in the sodalite unit and large cavity. In the structure of |Cs4.5Na8.5|[Si12Al12O48]-LTA(crystal 3), 4.5 Cs+ ions per unit cell occupy located in the large cavity and sodalite unit. 7.5 Na+ ions per unit cell occupy are located in the sodalite unit. This result shows that the large Cs+ ion is energetically preferred and first to be filed at large cavity.

Selective adsorption of cesium from high salt concentration of waste water

251st National Meeting (2016)

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