N,N-二烷基二甘酰胺酸类配体萃取Pr(Ⅲ)及在水溶液中的配位化学  

Extraction and Coordination Chemistry in Aqueous Solution of Pr(Ⅲ)with N,N-dialkyl Diglycolamic Acid

作　　者：马思齐[1] 张燕[1] 杨志红[1] 朱礼洋[1] 杨素亮[1] 田国新[1,2] MA Siqi;ZHANG Yan;YANG Zhihong;ZHU Liyang;YANG Suliang;TIAN Guoxin(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：《原子能科学技术》2021年第5期778-785,共8页Atomic Energy Science and Technology

摘　　要：N,N-二(2-乙基己基)二甘酰胺酸(HL)作为一种三齿单羧酸类萃取剂,在pH=1^4区域至强酸性条件下对三价镧系离子均具有一定的萃取能力,但不同酸度下的萃取机理不同。为更好地确定其配位机理,本文对HL从硝酸盐体系中萃取Pr(Ⅲ)及N,N-二甲基二甘酰胺酸(HL′)在水溶液中与Pr(Ⅲ)的配位化学进行了研究。在测定Pr(Ⅲ)与萃取剂HL在pH=1^4条件下生成萃合物的光谱和组成的基础上,结合水溶性同系物HL′与Pr(Ⅲ)在水溶液中生成的配合物及其光谱和结构,确定了HL与Pr(Ⅲ)在硝酸体系下pH=1^4区域内生成的萃合物有两种:一种是已报道过的具有PrL_3核心的萃合物;另一种是PrL_(2)NO_(3)。在水溶液中通过电位滴定法和光谱滴定法研究了HL′与Pr(Ⅲ)生成配合物的稳定常数及在紫外-可见区的吸收光谱。在1 mol/L NaClO_(4)介质中,去质子化的HL′可与Pr(Ⅲ)形成PrL′^(2+)、PrL′^+_(2)、PrL′_33种形式配合物,随着配体结合数的增加,Pr(Ⅲ)在400^600 nm的几个特征吸收峰持续红移,吸收强度稍有减弱。在水溶液中通过缓慢挥发获得了PrL′_3单晶化合物,晶体结构测定结果表明,配合物中3个配体均以三齿配体形式与Pr(Ⅲ)配位。通过比较水溶液中PrL′_3配合物、有机相中PrL_3萃合物的吸收光谱以及PrL′_3单晶化合物的固体漫反射光谱,确定在水溶液中PrL′_3配合物及萃取体系中具有PrL_3核心的萃合物中,都有3个三齿配体与Pr(Ⅲ)配位;通过比较水溶液中以1∶2配位的配合物PrL′^+_(2)的吸收光谱与组成为PrL_(2)NO_(3)的萃合物的吸收光谱,发现590 nm处峰形明显不同,表明萃合物中硝酸根很可能与Pr(Ⅲ)也直接配位。在萃取剂与金属离子浓度比不同时,生成的萃合物种类不同,当萃取剂浓度与金属离子浓度比小于等于2时,推测硝酸根在内层参与配位。As a tridentate monocarboxylic acid extractant, N, N-bis(2-ethylhexyl) diglycolamic acid(HL) has a considerable extraction capability for trivalent lanthanides from neutral to very acidic solutions, while the extraction mechanism is different under conditions of varying acid concentrations. In order to determine the extraction behavior of HL with metal ions, the extraction of Pr(Ⅲ) with HL from nitrate media at pH=1-4 region and the coordination chemistry of Pr(Ⅲ) with N, N-dimethyl diglycolamic acid(HL′) in aqueous solutions were studied in this paper. Based on the information abstracted from the spectra and composition of the extracted complexes of Pr(Ⅲ) with HL formed at pH=1-4 region under different conditions, it is found that there are two extracted complexes for HL and Pr(Ⅲ). By comparing the spectra of the extracted complexes and the spectra of the complexes of the water-soluble homologues HL′, one of the two extracted complexes is the previously reported complex which is with a PrL3 core, and the other one is PrL2NO3 which is identified for the first time. Potential titration and spectrometric titration in aqueous solution were used to study the stability constants and obtain the UV-Vis standard absorption spectra of the complexes formed between HL′ and Pr(Ⅲ). In 1 mol/L NaClO4 solution, deprotonated HL′ can forms PrL′2+, PrL′+2 , PrL′3 complexes with Pr(Ⅲ). With more ligands binding in the complexes, the characteristic absorption peaks of Pr(Ⅲ) in 400-600 nm region continue red-shift, and the absorption intensities just reduce slightly. Single crystals of the PrL′3 compound are obtained by slow volatilization from aqueous solution containing Pr(Ⅲ) and L′-. The crystal structure analysis results show that in the complex the three ligands all are tridentate coordinate to Pr(Ⅲ). There are some clear difference between the absorption spectrum of PrL′+2 complex in aqueous solution and the absorption spectrum of the extracted PrL2NO3 complex the in organic phase, the peak

关 键 词：Pr(Ⅲ) 萃取 吸收光谱 晶体结构 N N-二(2-乙基己基)二甘酰胺酸 N N-二甲基二甘酰胺酸 

分 类 号：O641.4[理学—物理化学]