Tetraphenylpyridinium pertechnetate: a promising salt for the immobilization of technetium

Abstract

Abstract In the context of the immobilization of technetium, as pertechnetate, from spent nuclear fuel from reprocessing activies, or potentially a scavenger for pertechnetate in repository conditions, the compound tetraphenylpyridinium pertechnetate (TPPy-TcO 4 ) has been synthesized, structurally characterized and its solubility investigated. The compound TPPy-TcO 4 has been prepared by metathesis from ammonium pertechnetate and 1,2,4,6-tetraphenylpyridinium tetrafluoroborate from a water/acetone media. Diffraction measurements show that the compound crystallizes in the orthorhombic space group (Pbca) with a = 16.1242(10)Å, b = 16.7923(10)Å, and c = 17.6229(11)Å. The solubility of the salt has been investigated at room temperature in aqueous media at pH 2.22, 6.91, and 9.81 where solubility products were determined as 6.16 × 10 −12 , 4.13 × 10 −12 , and 1.16 × 10 −11 , respectively. The compound TPPy-TcO 4 is not the most insoluble pertechnetate salt reported so far, but comparatively has a lower solubility than that of most other pertechnetate salts.