NaA zeolite(Si/Al=1.00)has been commercially applied for capturing radioactive 90Sr^(2+)because of its high surface charge density,effectively stabilizing the multivalent cation.However,owing to its narrow micropore o...NaA zeolite(Si/Al=1.00)has been commercially applied for capturing radioactive 90Sr^(2+)because of its high surface charge density,effectively stabilizing the multivalent cation.However,owing to its narrow micropore opening(4.0Å),large micron-sized crystallites,and bulkiness of hydrated Sr^(2+),the Sr^(2+)exchange over NaA has been limited by very slow kinetics.In this study,we synthesized nanocrystalline low-silica X by minimizing a water content in a synthesis gel and utilizing a methyl cellulose hydrogel as a crystal growth inhibitor.The resulting zeolite exhibited high crystallinity and Al-rich framework(Si/Al of approximately 1.00)with the sole presence of tetrahedral Al sites,which are capable of high Sr^(2+)uptake and ion selectivity.Meanwhile,the zeolite with a FAU topology has a much larger micropore opening size(7.4Å)and a much smaller crystallite size(~340 nm)than NaA,which enable significantly enhanced ion-exchange kinetics.Compared to conventional NaA,the nanocrystalline low-silica X exhibited remarkably increased Sr^(2+)-exchange kinetics(>18-fold larger rate constant)in batch experiments.Although both the nanocrystalline low-silica X and NaA exhibited comparable Sr^(2+)capacities under equilibrated conditions,the former demonstrated a 5.5-fold larger breakthrough volume than NaA under dynamic conditions,attributed to its significantly faster Sr^(2+)-exchange kinetics.展开更多
基金supported by the institute of Civil Miltary Technology cooperation funded by the Defense Acquisition Program Administration and Ministry of Trade,Industry and Energy of Korea Government under grant No.22-CM-BR-14.
文摘NaA zeolite(Si/Al=1.00)has been commercially applied for capturing radioactive 90Sr^(2+)because of its high surface charge density,effectively stabilizing the multivalent cation.However,owing to its narrow micropore opening(4.0Å),large micron-sized crystallites,and bulkiness of hydrated Sr^(2+),the Sr^(2+)exchange over NaA has been limited by very slow kinetics.In this study,we synthesized nanocrystalline low-silica X by minimizing a water content in a synthesis gel and utilizing a methyl cellulose hydrogel as a crystal growth inhibitor.The resulting zeolite exhibited high crystallinity and Al-rich framework(Si/Al of approximately 1.00)with the sole presence of tetrahedral Al sites,which are capable of high Sr^(2+)uptake and ion selectivity.Meanwhile,the zeolite with a FAU topology has a much larger micropore opening size(7.4Å)and a much smaller crystallite size(~340 nm)than NaA,which enable significantly enhanced ion-exchange kinetics.Compared to conventional NaA,the nanocrystalline low-silica X exhibited remarkably increased Sr^(2+)-exchange kinetics(>18-fold larger rate constant)in batch experiments.Although both the nanocrystalline low-silica X and NaA exhibited comparable Sr^(2+)capacities under equilibrated conditions,the former demonstrated a 5.5-fold larger breakthrough volume than NaA under dynamic conditions,attributed to its significantly faster Sr^(2+)-exchange kinetics.
