Distribution and identification of Plutonium(IV) species in tri-n-butyl phosphate/HNO3 extraction system containing acetohydroxamic acid

Complexation Chemistry of Zirconium(IV), Uranium(VI), and Iron(III) with Acetohydroxamic Acid

“…Both plutonium and zirconium-AHA complexes are much stronger than uranyl-AHA complexes, as evident by the significant differences in their stability constants. With the formation of particularly strong hydrophilic complexes of PuðAHAÞ 4Àn n , acetohydroxamic acid significantly decreases the distribution of plutonium between the aqueous and TBP phases (32,(45)(46)(47). The same is also true for zirconium, as AHA decreases the distribution of Zr 4þ by TBP (48) by forming strong ZrðAHAÞ 4Àn n complexes.…”

Modeling of Pu(IV) Extraction by Tri-n-butyl Phosphate from Acidic Nitrate Media Containing Acetohydroxamic Acid

“…Because of the complex chemistry of plutonium and neptunium at lower nitric acid concentrations, such as disproportionation of Pu(IV), hydrolysis of Pu(IV) and Np(IV), and possible formation of colloids, these extraction models are mainly applicable at higher nitric acid concentrations. Hydrolysis and disproportionation can significantly affect the distribution ratios by TBP as has been demonstrated recently for extraction of Pu(IV) . On the other hand, at high aqueous HNO 3 concentrations, when TBP·HNO 3 adducts become dominant, the formation of M (NO 3 ) 4 (TBP)(TBP·HNO 3 ) species was also proposed for tetravalent Pu and Np. ,, …”

“…Several salt-free reagents to separate Pu and Np from U have been proposed and tested, including carboxylic derivates of hydroxylamine such as acetohydroxamic acid (HAHA) or formohydroxamic acid (FHA) . In the past decade a number of papers relevant to the extraction of Pu(IV) by tri- n -butyl phosphate (TBP) from HNO 3 in the absence and presence of HAHA have been published. − Recently, a model of the extraction of Pu(IV) and Np(IV) by TBP from various aqueous nitrate concentrations in the absence of HAHA has been developed. Because of the complex chemistry of plutonium and neptunium at lower nitric acid concentrations, such as disproportionation of Pu(IV), hydrolysis of Pu(IV) and Np(IV), and possible formation of colloids, these extraction models are mainly applicable at higher nitric acid concentrations.…”

“…Hydrolysis and disproportionation can significantly affect the distribution ratios by TBP as has been demonstrated recently for extraction of Pu(IV). 10 On the other hand, at high aqueous HNO 3 concentrations, when TBP • HNO 3 adducts become dominant, the forma-tion of M(NO 3 ) 4 (TBP)(TBP • HNO 3 ) species was also proposed for tetravalent Pu and Np. 11,13,14 In the presence of hydroxamic acids the distribution ratios for tetravalent Pu and Np by TBP drops significantly due to the formation of strong metal(IV)-hydroxamate complexes.…”

“…11,13,14 In the presence of hydroxamic acids the distribution ratios for tetravalent Pu and Np by TBP drops significantly due to the formation of strong metal(IV)-hydroxamate complexes. 3,6,8,10,15 Although the metal complexes with FHA and HAHA are rather hydrophilic in character compared to benzohydroxamate complexes, it has been previously reported that, in the presence of HAHA, coextraction of acetohydroxamate complexes of U(VI), 16,17 Mo(VI), 18 Pu(IV), 8 and Np(IV) 19 by TBP is possible. Therefore, to successfully predict distribution ratios of Pu(IV) in the presence of HAHA, a more thorough design of an extraction model is very important.…”