Mutual separation of Am and Cm using ADAAM (alkyl DiAmide AMine) and Reduction of Volumes for Liquid Waste generated via batch wise multistage extractions

Abstract

ABSTRACTThe mutual separation of Am and Cm is conducted using an alkyl-diamide amine (ADAAM(EH)) extractant. ADAAM(EH) exhibits extremely high separation factor (SF) with respect to Am and Cm separation (SF = 5.9) in a HNO3-n-dodecane system. The batch-wise multistage extractions are performed using a system containing 0.2 M ADAAM(EH) and 1.5 M HNO3, with their distribution ratios (D) of the system for Am and Cm equal to 2.55 and 0.434, respectively. In this multistage extraction, 3 stages of feed, 9 stages involving scrubbing, and 11 stages involving the use of an organic solvent give 96.5% and 1.06% yields of Am and Cm, respectively. After the mutual separation, the aqueous and the organic phases that includes actinides increases four times in volume compared to the feed solution. Additional extraction steps are to reduce the volume of the solutions including actinides. We use tetraethyl diglycolamide (TEDGA)/water for Am concentration, tetraoctyl diglycolamide/n-dodecane for the intermediate extraction, and TEDGA/water for stripping in the Cm concentration step. Taking the additional steps, Am and Cm can be recovered in just two or three stages in the aqueous phases.KEYWORDS: Solvent extractionAmCmseparationADAAMDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. AcknowledgmentsThe authors gratefully acknowledge Dr. Y. Kitatsuji at JAEA for safety management with respect to actinides and Dr. M. Arisaka at JAEA for ICP-measurements.Declaration of Interest StatementNo potential conflict of interest was reported by the authors.Figure 1 Extractant, masking agents, and other reagents used in this studyDisplay full sizeFigure 2 The conditions of batch-wise multistage extraction. (a) Am and Cm separation, (b) Am concentration, (c) Cm concentrationDisplay full sizeFigure 3 Extraction behavior of metals using alkyl-diamide amine (ADAAM). (a) D(Ln, An) against HNO3 concentration, (b) D(An) against ADAAM concentration, (c) D(Ln) against ADAAM concentration, (d) D(Ln) against their atomic number, (e) D(FP) against HNO3 concentration, and (f) D(FP) against ADAAM concentrationDisplay full sizeFigure 4 Ball-and-stick description of [M(ADAAM)]3+, wherein the black, red, blue, and brown spheres show metal, oxygen, nitrogen, and carbon atoms, respectively, and hydrogen atoms are not shown to avoid confusion, with the M3+–Namine and M3+–Oamide bond lengths in the Å unit shown as Am3+/Cm3+Display full sizeFigure 5 Representatives of 5f-type α-MOs in the valence region for [M(ADAAM)]3+Display full size Figure 6 pH and masking agent dependence on D(An, Ln) in alkyl-diamide amine (ADAAM) extractant. Condition: (a) 0.5 M ADAAM − 2.5 M HNO3 + 1.3 M en + 1 M MAc + 0.1 M DTBA (b) 0.5 M ADAAM − 1.5 M HNO3 + 0.05 M DGAc + 0.5 M en + 1 M Mac (c) 0.5 M ADAAM − 1.5 M HNO3 + TMDGA or NTAamide(C2)Display full sizeFigure 7 Results of multistage extraction. (a) recovery ratio (%) of An at each stage of the aqueous phase (b) recovery ratio (%) of An at each stage of the organic phase Extraction condition: 0.2 M ADAAM/n-dodecane, 1.5 M HNO3 Condition of multi-stage extraction: Stage numbers of organic phase, aqueous phase of feed and scrub: 11, 3, 9.Display full sizeTable 2 (b) pH in aqueous phase with malonic acid after ADAAM extraction*Download CSVDisplay Table