Spectroscopic studies of the uranium(VI) interaction with nitrogen and sulfur containing model ligands

The migration and interaction behavior of actinides can be effectively influenced by humic substances, biopolymers ubiquitous in natural environments, due to their ability for complex and colloid formation and their redox properties. In addition to oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.
The aim of this work is to determine the influence of various nitrogen and sulfur containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used. In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic acid and 4-hydroxybenzenesulfonic acid as well as anthranilic and nicotinic acid. The complex formation constants for the uranium(VI) complexation were determined applying time-resolved laser-induced fluorescence spectroscopy (TRLFS).