SOMS: Sandia Octahedral Molecular Sieves. A new class of ion exchangers selective for the removal of Sr~(2+) from waste streams.

摘要

A new class of molecular sieve materials named Sandia Octahedral MolecularSieves (SOMS) has been synthesized. These sieves have a Na/M~(IV)/Nb (M = Ti, Zr) oxideand exchangeable sodium cations and water molecules in open channels. The SOMSphases are isostructural with variable M~(IV):Nb (1:50-1:4) ratios. The structure(Na_(16)Ti_(3.2)Nb_(12.8)O_(44.8)(OH)_(3.2)?8H_2O; SOMS-1) was determined from a combination ofmethods including synchrotron X-ray, MAS NMR, thermal and elemental analyses. TheSOMS are extremely selective for sorption of divalent cations, particularly Sr~(2+). The ionexchangedSOMS undergo direct thermal conversion to perovskite-type phases, indicatingthis is a promising new method for removal and immobilization of radioactive Sr-90 frommixed nuclear waste.