U(Ⅵ)与乙酰氧肟酸的配位化学  

Coordination Chemistry of U(Ⅵ)With Acetohydroxamic Acid

作　　者：姚鼎新 陈少康 杨琪 柳倩 杨雅婷 杨素亮[1] 田国新[1,2] YAO Ding-xin;CHEN Shao-kang;YANG Qi;LIU Qian;YANG Ya-ting;YANG Su-liang;TIAN Guo-xin(Department of Radiochemistry,China Institute of Atomic Energy,Beijing 102413,China;Institute of Nuclear and New Energy Technology,Tsinghua University,Beijing 100084,China)

机构地区：[1]中国原子能科学研究院放射化学研究所,北京102413 [2]清华大学核能与新能源技术研究院,北京100084

出　　处：《核化学与放射化学》2024年第3期213-220,I0002,共9页Journal of Nuclear and Radiochemistry

摘　　要：乙酰氧肟酸(又名乙异羟肟酸,AHA)是最有希望应用于水法后处理PUREX流程铀纯化循环的配位剂。本工作用pH电位滴定方法和拉曼光谱滴定方法研究了AHA的电离过程及其与U(Ⅵ)在1.0 mol/L NaClO_(4)介质中的配位化学。酸碱滴定过程中AHA表现为一元酸,其质子化常数为109.24±0.11(误差由HyperQuad软件拟合计算给出),研究pH范围内未观察到AHA的二级电离。但AHA与U(Ⅵ)形成配合物时可脱去第二个质子,在中性和碱性pH范围内与U(Ⅵ)进一步形成五种以前报道未发现的配合物。配合物中AHA既可以是脱一个质子的离子,也可以脱两个质子的形式存在。拟合得到了七种主要配合物的稳定常数,并发现该类配体在中性以及碱性区与U(Ⅵ)的配位反应能够与水解作用竞争并抑制水解。拉曼光谱滴定实验结果表明,随着配合物中配体数量的增加,配合物中U(Ⅵ)的特征拉曼光谱峰向低波数移动。根据配合物稳定常数计算拉曼光谱滴定过程中配合物物种的分布,结果显示:不同于通常的认知,配比相同的AHA与U(Ⅵ)配合物,其配体是否去质子化对U(Ⅵ)拉曼散射光谱的影响难以分辨,但对其强度产生显著影响。The deprotonation of acetohydroxamic acid(AHA)and its coordination chemistry with uranyl ion()in 1.0 mol/L NaClO_(4) has been investigated with potentiometric titration and Raman spectroscopy at 25℃.For the first time,the deprotonations of AHA in aqueous solutions are quantitatively investigated with potentiometric titration method.It is found that in aqueous solution AHA acts as a monobasic acid and the protonation constants calculated to be pKa1=9.24±0.11(errors are given by the HyperQuad software fitting calculations).The determined pKa1 is in good agreement with the previously reported one-step protonation.In a wide pH range from acidic to basic aqueous solutions,the two step-wise protonation of AHA has been found,at the same time,the complexation of U(Ⅵ)with AHA has been revisited.For AHA at different degrees of deprotonation,various complexes of U(Ⅵ)with AHA at ratios of U(Ⅵ)and AHA from 1∶1 to 1∶3 are recognized by potentiometric titration method.Amongst,the 1∶1 set of complexes consists of UO_(2)A^(+)and UO_(2)(OH)A,the 1∶2 includes UO_(2)A_(2) and UO_(2)(OH),and the 1∶3 is composed of three complexes UO_(2),UO_(2)(OH)and UO_(2)(OH)2.There are maybe more complex species formed during the titrations,especially in very basic solutions,but those cannot be well quantitatively characterized due to their very low solubilities.The stability constants of the mentioned seven species have been determined by HyperQuad software,with the values of UO_(2)A^(+)and UO_(2)A_(2) in good consistence with those reported previously.All other five new-detected complexes are detected in solutions of relatively higher pH values.In the potentiometric titrations at relatively low AHA concentration,both protons of AHA can be deprotonated to form higher proportioned UO_(2)(OH)A in comparison with UO_(2)A_(2),which is an equal species to UO_(2)A^(+)in term of releasing/consuming H+during the titration process.At greatly excessive concentrations of AHA,three complexes,UO_(2)A^(+),UO_(2)A_(2),and UO_(2) are successiv

关 键 词：乙酰氧肟酸 U(Ⅵ) 配位 稳定常数 拉曼光谱 

分 类 号：TL211[核科学技术—核燃料循环与材料] TL24[理学—物理化学] O641.4[理学—化学]