Complexation of NpO2+ with (2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) in aqueous solutions: thermodynamic studies and structural analysis

作者：Li Xingliang; Zhang Zhicheng^*; Martin Leigh R; Luo Shunzhong^*; Rao Linfeng

来源：RSC Advances, 2016, 6(115): 114916-114926.

DOI：10.1039/c6ra17818a

Complexation of Np(V) with N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) was studied in aqueous solution (I = 1.0 mol L-1 NaClO4, t = 25 degrees C) by spectrophotometry, microcalorimetry and Extended X-ray absorption fine structure (EXAFS) spectroscopy. Equilibrium constants for the formation of three complexes, NpO2L2-, NpO2(HL)(-), and (NpO2)2(OH)(2)L-2(6-), were determined to be (6.91 +/- 0.06), (4.28 +/- 0.03) and -(4.93 +/- 0.03), respectively. The enthalpies of complexation were determined to be -(8.0 +/- 2.0) kJ mol(-1) for NpO2L2- and -(2.2 +/- 2.0) kJ mol(-1) for NpO2(HL)(-). Thermodynamic data of the complexation of Np(V) with HEDTA were compared to those of Np(V) with other aminopolycarboxylic acids, gaining insight into the possible coordination modes of the complexes. The EXAFS studies provided further structural information on those modes. In both NpO2L2- and NpO2(HL)(-) complexes, HEDTA coordinates to Np(V) in a tridentate mode through two oxygens of two carboxylic groups and one nitrogen of the amine group. In the (NpO2)(2)(OH)(2)L-2(6-) complex, two Np(V) atoms are bridged by two hydroxides and each HEDTA maintains the tridentate coordination mode.

• 出版日期2016
• 单位中国工程物理研究院核物理与化学研究所; 中国工程物理研究院