Thermodynamics on the complexation of uranium (VI) with N-methylethylenediamine-N,N′,N'-triacetic acid in aqueous Solution: Potentiometry and microcalorimetry

Nuclear Analysis Pub Date : 2022-12-01 DOI:10.1016/j.nucana.2023.100049

Zhuoxi Li , Yuyu Liang , Baihua Chen , Wanjun Mu , Jun Tu , Yuchuan Yang , Yanqiu Yang , Hongyuan Wei , Xingliang Li

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引用次数: 1

Abstract

Stability constants and enthalpies of N-methylethylenediamine-N,N′,N'-triacetic acid (MEDTA, denoted as H₃L) complexes with uranyl were measured using potentiometry and microcalorimetry, I = 1.0 mol L⁻¹ NaClO₄ solution at 25 °C. Thermodynamic analyses revealed three U(VI)/MEDTA complexes: UO₂(HL), UO₂L⁻, and UO₂(OH)L²⁻. The results showed that the complex formation of UO₂L⁻ (UO₂²⁺ + L³⁻ = UO₂L⁻) is endothermic and driven solely by entropy. MEDTA in the UO₂L⁻ complex is a tetradentate and coordinates with U(VI) along the ethylenediamine backbone. Stability constant of mononuclear uranyl complex with MEDTA (UO₂L⁻) is lower than UO₂²⁺/EDDA complex but higher than UO₂²⁺/HEDTA complex, indicating that dangling acetate arm of MEDTA or hydroxyethyl group of HEDTA would lower the stability.

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铀(VI)在水溶液中与N-甲基乙二胺-N,N '，N'-三乙酸络合的热力学:电位法和微量热法

采用电位法和微量热法测定了N-甲基乙二胺-N,N '，N'-三乙酸(MEDTA，记为H3L)与铀酰配合物的稳定常数和焓。溶液I = 1.0 mol L−1 NaClO4，温度25℃。热力学分析发现了三种U(VI)/MEDTA配合物:UO2(HL)、UO2L−和UO2(OH)L2−。结果表明，UO2L−(UO22+ + L3−= UO2L−)的络合物是吸热生成的，完全由熵驱动。UO2L−配合物中的MEDTA是一个四齿化合物，沿乙二胺主链与U(VI)配位。单核铀酰与MEDTA配合物(UO2L−)的稳定性常数低于UO22+/EDDA配合物，但高于UO22+/HEDTA配合物，说明MEDTA的乙酸臂悬垂或HEDTA的羟乙基会降低其稳定性。

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来源期刊

Nuclear Analysis

CiteScore

1.70

自引率

0.00%

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