Title: Complexation of Plutonium(IV) with trans-1,2-Diaminocyclohexane-N,N,N',N'-tetraacetic Acid (CDTA) in Acidic Solution

Abstract

Understanding the interaction of Pu(IV) with complexing agents present in the nuclear fuel cycle is important for predicting the performance of used nuclear fuel separations. The complexation of Pu(IV) with trans-1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid (CDTA) was studied in acidic solutions of 0.10 0.50 mol∙L^-1 HClO₄ with 1.00 mol∙L^-1 (Na,H)ClO₄ total ionic strength by a liquid–liquid extraction method using tracer quantities of ₂₃₈Pu. The acid dissociation constants of CDTA and the autoprotolysis constant of water were determined via potentiometric titrations in 0.10–2.00 mol∙L^-1 NaClO₄ and 25.0 ± 0.1 °C. The variation of the dissociation constants with ionic strength was modeled with the Specific ion Interaction Theory (SIT) and the associated SIT parameters were obtained. The thermodynamic dissociation 23 constants at zero ionic strength for water and CDTA were determined from this analysis as PK$$^o_w$$ = 14.00 ± 0.03, PK$$^o_{a2}$$ = 1.52 ± 0.04, PK$$^o_{a3}$$ = 2.78 ± 0.05, PK$$^o_{a4}$$ = 4.17 ± 0.04, PK$$^o_{a5}$$ = 6.75 ± 0.02, and PK$$^o_{a6}$$ = 10.64 ± 0.04 at 25.0 ± 0.1 °C. The results of the liquid–liquid extraction experiments indicated the formation of a 1:0:1 complex, PuCDTA^o, and the presence of additional protonated species, Pu(HCDTA)⁺ and Pu(H₂CDTA⁾²⁺, at these acidities. The corresponding stability constants in 1.00 mol·L^-1 (Na,H)ClO₄ and 23 ± 1 °C were determined to be log₁₀ β₁₀₁=24.2 ± 0.3, log₁₀ β₁₁₁ =25.4 ± 0.2, and log₁₀ β₁₂₁ = 25.8 ± 0.1.

Authors:

Friend, Mitchell T. ^[1]; Zhao, Pihong ^[2]; Zavarin, Mavrik ^[2]; Wall, Nathalie A.  ^[1]

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+ Show Author Affiliations

1. Washington State Univ., Pullman, WA (United States). Dept. of Chemistry
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Inst., Physical and Life Sciences

Publication Date:

Mon Feb 18 00:00:00 EST 2019

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Washington State Univ., Pullman, WA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Office of Nuclear Energy (NE)

OSTI Identifier:

1548379

Alternate Identifier(s):

OSTI ID: 1529249

Report Number(s):

LLNL-JRNL-776832
Journal ID: ISSN 0095-9782; 969848

Grant/Contract Number:  

AC52-07NA27344; NA0002916

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Solution Chemistry

Additional Journal Information:

Journal Volume: 48; Journal Issue: 2; Journal ID: ISSN 0095-9782

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Plutonium(IV); CDTA; Complexation; Stability Constant; Liquid Liquid Extraction; Specific ion Interaction Theory