Non-heterocyclic N-donor ligands of nitrilotriacetamide for Am3+/Eu3+ separation

• Published in: Separation and purification technology 2019-02, Vol.210, p.107-116
• Main Authors: Wang, Zhipeng, Wang, Jieru, Ding, Songdong, Liu, Ying, Zhang, Lirong, Song, Lianjun, Chen, Zhili, Yang, Xiuying, Wang, Xueyu
• Format: Article
• Language: English
• Subjects: Am3; Eu3; Extraction; NTAamide
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2018.04.065

[Display omitted] •Chemical structure–extraction property relationships of NTAamides were investigated.•The composition of extracted complexes was measured by slope analysis and HRMS.•The protonation constants of NTAamides were determined by acid-base titration.•The stability constants of complexes were obtained via fluorescence titration. For figuring out the relationships between chemical structure and extraction properties of the soft non-heterocyclic N-donor ligand nitrilotriacetamide (NTAamide), eight representative ligands with different substituent groups based on NTAamide were synthesized on purpose. Their extraction behaviors toward Am3+ and Eu3+ were investigated. In the examined HNO3 concentration ranging from 0.01 to 0.50 mol/L, the distribution ratios (D) of Am3+ and Eu3+ increased with increasing the extractant concentration or decreasing the aqueous phase acidity. The highest separation factor (SFAm/Eu) of 12 with DAm = 5.8 and DEu = 0.49 could be obtained in the case of the extraction by 0.10 mol/L N,N,N',N',N“,N”-hexadecylnitrilotriacetamide (NTAamide(n-Dec)) in MIBK as diluent from 0.10 mol/L HNO3 solution. The extractability of eight ligands decreased in the order of NTAamide(n-Dodec) > NTAamide(n-Dec) > NTAamide(n-Oct) > NTAamide(n-Bu) > NTAamide(i-Bu) > NTAamide(Et-p-MePh) > NTAamide(Et-Ph) > NTAamide(2-EtHex). The aliphatic substituent groups with longer straight chain are advantageous to the extraction, while the aromatic ones with larger steric hindrance and electron-withdrawing property are disadvantageous. The log β values between NTAamides and Eu3+ were obtained by fluorescence titration for the first time. Moreover, HRMS indicated the formation of 1:1 complexes of NTAamides with Eu3+, which was in good accordance with the extraction results obtained from slope analysis.