AbstractThe aqueous speciation and hydrolysis of actinides in both the presence and absence of organic ligands has been investigated in the pH range 1 - 13. The speciation and hydrolysis of Th4+, U4+ and UO22+ with H3thme, H3tea, H3bic, H3heidi, H3NTA, H2ADA and H3cit have been investigated using various analytical techniques (1H NMR, 13C NMR, IR, UV-Vis(-nIR) spectroscopy and potentiometric titrations). The PHREEQC interactive software suite was used to predict speciation with the formation constants for various complexes calculated in the Hyperquad software suite.Formation constants of Th4+, U4+ and UO22+ hydroxide species have been calculated showing the formation of polymeric complexes. Experiments showed no complexation of actinides by H3thme and H3tea in aqueous solutions. However, 1:3 (M:L) complexation of Th4+ and U4+ was observed with H3bic along with 1:2 (M:L) complexation of UO22+. A variety of 1:1 and 1:2 (M:L) complexes were observed with H3heidi, H3NTA, H2ADA and H3cit for the actinides. Formation constants for complexes of H3NTA with Th4+ and UO22+, H2ADA with Th4+ and H3cit with UO22+ were calculated in Hyperquad. Studies of Pu3+ with H3heidi showed little complexation but 5Me-HXTAH4 showed 1:3 (M:L) speciation. Complexation of PuO22+ by saldien(Et2N)2H2 and salterpyH2 was shown and a secondary band was observed at ~944 nm after multiple days. The functionalities of organic ligands have been shown to have a profound effect on the (partial) hydrolysis of the actinides.
|Date of Award||31 Dec 2014|
|Supervisor||Scott Heath (Supervisor)|
- formation constant