Hexavalent Actinide Extraction Using N,N-Dialkyl Amides

Abstract

Recently, efforts towards closing the nuclear fuel cycle have considered oxidizing americium to a hexavalent, linear-dioxo cation for co-recovery with hexavalent U, Np, and Pu from molar nitric acid using solvating extraction ligands such as tri-n-butyl phosphate or diamyl amylphosphonate. This work assesses solvent extraction recovery of sodium bismuthate oxidized americium by N,N-di-(2-ethylhexyl)butyramide (DEHBA), N,N-di-(2-ethylhexyl)isobutyramide (DEHiBA), and N,N-dihexyloctanamide (DHOA). Extraction efficiency between the monoamides was found to increase in the order of DEHiBA < DHOA < DEHBA. For all monoamides, oxidized americium extraction was less than 50% from 4 M HNO 3 and below.Extraction efficiency above 50% was obtained using concentrations of 5 M HNO 3 or higher.The DEHBA extractant provided the highest distribution value of 5.4 at 7 M HNO 3 . Distribution values were found to be stable for up to 45 seconds aqueous/organic phase mixing times and indicated decreased reduction of hexavalent americium relative to separations completed with 2 organophosphorus extractants. The simultaneous co-extraction of U, Np, Pu, and Am was demonstrated using DEHiBA, and was found to decrease with increasing atomic number (D U > D Np > D Pu > D Am ). Interestingly, a break in recovery was observed where ligher actinides, U and Np, were better recovered relative to the heavier actinides, Pu and Am, in this study. This observation seems to be related to differences in the extracted metal complex for light actinides

Kinetics of the Autoreduction of Hexavalent Americium in Aqueous Nitric Acid

“…[9][10][11][12] Recent studies have demonstrated 5f element group co-extraction of U(VI), Pu(VI), Np(VI), and Am(VI) using numerous extractants. [13][14][15] These studies demonstrate a simplified pathway to separate americium from the trivalent lanthanides and curium; widely regarded as one of the most challenging separations in radiochemistry.…”

Facile Synthesis of Phytic Acid Impregnated Polyaniline for Enhanced U(VI) Adsorption

“…The fitting results calculated from the Langmuir, Freundlich, and D-R isotherm models are summarized in Tables 2 and 3 5) obeys the Langmuir isotherm model (R 2 > 0.99) by comparing the R 2 parameters of Langmuir and Freundlich isotherm models, which suggested that the adsorption of U(VI) onto the adsorbents follows the monolayer adsorption manner. 14 The theoretical maximum adsorption capacity are about 35.4, 88.1, 90.3, and 131.9 mg/g for PANI, PA-PANI-1, PA-PANI-3, and PA-PANI-5, respectively.…”

“…Several methods have been demonstrated to remove U­(VI) from aqueous solution, for instance, chemical precipitation, ion exchange, adsorption, and solvent extraction. − Among these methods, the adsorption method has been widely studied owing to its advantages of simple operation, high adsorption capacity, high selectivity, and ease of repetitive use. − Various adsorbents have been reported for the elimination of U­(VI), such as polymers (polyaniline, chitosan bearing α-aminophosphonate and polypyrrole), − carbon material (graphene oxide, carbonaceous nanofibers), , metal oxide (MnO 2 ), and metal–organic frameworks …”

Ultrafiltration separation of nanoscale Am(VI)-polyoxometalate clusters from lanthanides

“…The rejection coefficient of Eu 3+ is low at 1.3%. These results give rise to a Am(VI)/Eu(III) separation factor of 873 that is significantly higher than those of all other americium oxidation associated separation techniques [20][21][22][23][24][25][26][27] (Fig. 4c).…”