Selective Extraction of Am 3+ from Eu 3+ Using 3,3’-Butyloxy-Bis-1,2,4-Triazinyl-2,6-Pyridine in a Hydrocarbon Diluent

Efficient separation of long-lived, trivalent actinides from the chemically similar lanthanide fission products remains a significant challenge in nuclear waste management. In solvent extraction processes, phase modifiers are often employed to enhance the solubility of extractants in process-relevant, aliphatic diluents while suppressing the formation of third phases. This work investigates the use of 2,6-bis(5,6-bis(3-butyoxyphenyl)-1,2,4-triazinyl-3-yl)pyridine (BOB-BTP) for the extraction of 241Am3+ over 154–152Eu3+. The impact of the phase modifier (1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol) (Cs-7SB), routinely employed for 137Cs and 90Sr extractions in an Isopar/HNO3(aq) biphasic system was systematically assessed for potential utility with BOB-BTP. A 10:1 Isopar:Cs-7SB ratio greatly enhanced complexant solubility and extraction efficiency, while simultaneously suppressing the formation of precipitates. Extraction studies conducted up to 2M HNO3(aq) confirmed high chemoselectivity for 241Am3+ and excellent resistance to hydrolytic degradation of the complexant. Evaluation of decomplexation was also studied. BOB-BTP was recycled through two successive extraction sequences, thereby suggesting a high potential for reusability without diminished performance. The findings demonstrate the potential of this complexant-diluent combination for advancing partitioning applications toward closure of the nuclear fuel cycle and mitigation of the long-term radiotoxicity of spent nuclear fuel. Evaluation of acid and complexant concentration variance, in addition to decomplexation and recyclability for multiple extractions are reported herein.