Novel water-soluble aromatic bisdiglycolamide masking agents for the separation of trivalent americium over lanthanides by NTAamide(n-Oct) extractant

Two novel water-soluble aromatic bisdiglycolamides (BisDGAs) of SO3-TEX(m)-BisDGA (sodium bis((2-(2- (diethylamino)-2-oxoethoxy)acetamido)methyl)benzenesulfonate) and SO3-TEX(p)-BisDGA (sodium 2,5-bis((2- (2-(diethylamino)-2-oxoethoxy)acetamido)methyl)benzenesulfonate) were synthesized and used as masking agents for the selective extraction and separation of Am3+ over Eu3+ in HNO3 solutions by N,N,N ',N ',N '',N ''- hexaoctylnitrilotriacetamide (NTAamide(n-Oct)) in n-dodecane. Their influences on the separation effect of Am3+ over Eu3+ were investigated and compared with that of a water-soluble aliphatic bisdiglycolamide of N,N, N ''',N '''-tetraethyl-N ',N ''-ethidene bisdiglycolamide (TEE-BisDGA) reported by our previous work. SO3-TEX(m)-BisDGA and SO3-TEX(p)-BisDGA exhibit significantly better masking effects than TEE-BisDGA. The masking selectivity for Eu3+ over Am3+ follows the order of SO3-TEX(m)-BisDGA > SO3-TEX(p)-BisDGA > TEE-BisDGA. During the extraction process, the three BisDGA masking agents form the 1:2 complexes, while the NTAamide (n- Oct) extractant forms the 1:1 complexes with Am3+ and Eu3+. Meanwhile, the conditional stability constants (log beta) for the three masking agents with Eu3+ were calculated using the least squares method, which are also in line with those obtained from fluorescence spectrometry (FS). By means of FS, time-resolved laser-induced fluores-cence spectrometry (TRLFS), Fourier Transform infrared spectrometry (FT-IR), conductivity, and electrospray ionization mass spectrometry (ESI-MS) analyses, the composition of the complex of Eu3+ with water-soluble BisDGAs (L) was determined to be [Eu(NO3)2(H2O)center dot 2L](NO3). Furthermore, a batch simulation of multistage countercurrent extraction with 12-stage extraction, 4-stage scrubbing and 8-stage stripping was carried out and demonstrates a highly efficient separation of Am3+ over Lns3+ with the recovery rates above 99.9 % for all metal ions in the simulated feed solution, and with the decontamination factors more than 500 between Am3+ and most of the lanthanide ions.