Investigations to the System Ln(III)/An(III)-B(OH)3-Organics

Boric acid (B(OH)3) and (poly)borates are of great interest regarding the mobilization of trivalent actinides in nuclear waste repositories, particularly in salt deposits.
This work describes approaches to determine the stability constant in the Eu(III)-borate system. The stability constant between Eu(III) and borates is in the order of magnitude of 1...2, and with it the borate complexation is very weak.
Furthermore, in presence of polyborates at pH 6 the formation of a solid Eu borate species is observed. The formation rate of the solid Eu borate species depends on the polyborate concentration and salt concentration/type (NaClO4/NaCl). Some structural information of the solid Eu borate were provided from IR spectroscopy, solid-state NMR (11B) and solid-state TRLFS.