Investigation of Ternary Complexes in Combined Organic Solvent for ALSEP

Transcription

1 Investigation of Ternary Complexes in Combined Organic Solvent for ALSEP Alena Paulenova 1, Brian J. GULLEKSON 1, Artem V. Gelis 2 1 Oregon State University 2 Argonne National Laboratory

2 Acid+Neutral mixtures Reviewed in: V.A.Babain, Extractant Mixtures [Ion Exchange and Solvent Extraction: A Series of Advances, Volume 19, Ed. BA Moyer, 2009]. The Universal Solvent Extraction (UNEX) Process. I. Development VN Romanovskiy, IV Smirnov, VA Babain, TA Todd, RS Herbst, JD Law, KN Brewer, SExIEx (2001) 1 21 BE Galkin et al (1988): "Extraction of cesium, Strontium, Rare Earths and Transplutonium Elements from Liquid Highly radioactive Wastes by Extraction based on Cobalt Dicarbollide, ISEC 1988 Moscow, Russia. Innovative/diamidic UNEX based on using diamides of dipicolinic acid instead of CMPO S.A. El Reefy, N.S. Awwad, H.F. Aly (1996): Liquid Liquid Extraction of Uranium from Phosphoric acid by HDEHP CYANEX 921 Mixture Dhami, P.S., Chitnis, R. R., Gopalakrishnan, V., Wattal, P.K., Ramanujam, A. & Bauri, A.K. (2001) Studies on the Partitioning of Actinides from High Level Waste Using a Mixture of HDEHP and CMPO as Extractant, Sep. Sci. Technol., vol. 36(2), G. Lumetta, A. Gelis, et al : The TRUSPEAK Concept: Combining CMPO and HDEHP for Separating Trivalent Lanthanides from the Transuranic Elements, SExIEx, A. Gelis, G. Lumetta: Actinide Lanthanide Separation Process ALSEP, I&EC, 53, 2014, Hérès, X., Nicol, C., Bisel, I., Baron, P. & Ramain, L.: PALADIN: A One Step Process for Actinides(III)/Fission Products Separation, GLOBAL 99 Proceedings, (1999) Innovative SANEX; DIAMEX SANEX based on HDEHP with TODGA and others (0.5M DMDOHEMA 0.3M HDEHP HTP; BTBP TODGA).

3 Extraction with Mixed Organic Solvents Combine multiple ligands which extract metals from different aqueous conditions to simultaneously perform different separations Neutral extractants require balancing the metal charge, allowing for use with high acidities Cation exchange ligands need higher ph of aqueous phases allowing their deprotonation and exchange proton for metal 3

4 Structures of the Extractants (A) HDEHP (B) CMPO (C) HEH[EHP] (D) T2EHDGA (E) TODGA

5 Selected Combinations In combination with 1 M HDEHP and HEH[EHP] in n-dodecane, two, normal and branched, diglycolamides as neutral extractants were chosen: TODGA and T2EHDGA Both extractants are reported to separate trivalent Ln and An from major fission products large working range of HNO 3 concentration good radiation stability HDEHP T2EHDGA showed sufficient SF of more than 20 in a wide range of ph conditions 5 T2EHDGA tetra 2 ethylhexyldiglycolamide HEH[EHP] 2 ethylhexyl phosphonic acid mono 2 ethylhexyl ester

6 Distribution of Am and Eu Non ideal D and SF have been shown in mixed extractant systems from 1 5M HNO 3 : Am extraction from were drastically improved when T2EHDGA or TODGA were instead of CMPO. D(Am) >10 at acidities >2 M with a mixture with even low, 0.02M T2EHDGA in 1 M HDEHP, whereas 0.1 M CMPO/(1 M HDEHP) mixture shows a decrease in D(Am) with increasing acidity. Minimum for Am and Eu partitioning at about ~0.5 M HNO3 for 0.05M T2EHDGA/0.75 M HEH[EHP] The Am and Ln partitioning from weak HNO 3 can be improved by: -1M HDEHP - 1M HDEHP + 0.1M CMPO - 1M HDEHP + 20mM T2EHDGA M HEH[EHP] + 50mM T2EHDGA M HEH[EHP] + 50mM TODGA - Inset: 152Eu extraction from HNO3 by 50 mm T2EHDGA+0.75M EHE[EHP] Gelis, A. V., Lumetta, G. J.; Actinide Lanthanide Separation Process ALSEP, Ind. Eng. increasing the concentrations of both HEH[EHP] and T2EHDGA (0.075M T2EHDGA/(1 M HEH[EHP])) or using TODGA instead of T2EHDGA as Am is better extracted with 0.05M TODGA /(0.75M HEH[EHP]) 5

7 Expected M 3+ (aq) + 3(HA) 2 (org) + L(org) M(HA 2 ) 3 L(org) + 3H + (aq) Intermolecular interaction, observed in comparable dual extractant systems, affect An/Ln separations. Inter-ligand interactions: dimerization of acidic extractant + formation adducts Non-ideal Ds and SFs in mixed extractant systems - investigations of the inter-ligand interactions must be investigated 2HA HA 1 1 In n-dodecane [J.Braley: β dim (HDEHP) = 4.43 β dim (HEH[EHP]) = 4.03

8 Observed vs Expected (not) TRUSPEAK: ALSEP: HA DGA HA DGA. Hydrogen bonding between phosphoryl group of CMPO and P O H group of HDEHP monomer: logβ ADD = 3.07 ± 0.05 Tkac, P; Vandegrift, GF; Lumetta, GJ; Gelis, AV: Study of the interaction between HDEHP and CMPO and its effect on the extraction of selected lanthanides. Ind. Eng. Chem. Res. 2012, 51,

9 Adducts in ALSEP organic phase.. P31 TRUSPEAK: FTIR (Tkac, 2012) and NMR (Lumetta, 2011) ALSEP: NMR did not work (P, C, H): 0.25M DGA, 0 2M HA FTIR on ATR diamond plate: (0.3M HA, 0 0.5M DGA) FTIR: Peak Assignments Region (cm 1 ) HDEHP/HEH[EHP] TODGA/T2EHDGA C = O P = O C O C P O C

10 IR spectra of Ligand Combinations in n-dodecane Significant HEH[EHP] HDEHP spectral mixed mixed changes with with DGAs upon DGAs also introduction produces lesser of spectral CMPO spectral changes to HDEHP/HEH[EHP] changes CMPO phosphoryl HEH[EHP] HDEHP P O P O group bonds (1650 (1100 and cmp C ) bonds cm 1 (1100 ) 950 cm 1 ) HDEHP/HEH[EHP] Fewer New peaks new P O peaks introduced and with P C bonds less (1300 intensity (1100 introduced cm ) cm 1 ) New peaks (1300 introduced 1100 (1300 cm 1 ) 1100 cm 1 ) 6

11 Observed vs Expected (not) Non-linear least squared regression fitting software used to determine adduct formation constants β : Log(β) of ligand interaction in n-dodecane logβ CMPO T2EHDGA TODGA HDEHP HEH[EHP] Agrees well with published data [3.4] by Tkac (2012), [3.07] by Lumetta, 2011.

12 Complexation of Am and Selected LN Analysis of the observed extraction system (simpler, without nitrate) FIRST step: extraction of metal to organic phase: HCl negligible extraction to the organic solvent containing only a cation exchange ligand in alkane diluent With no inorganic anions in organic phase, which could provide an alternate means of metal DGA complexation, metal charge in the extracted complex is balanced only with anions of the cation exchange extractant: 3, 3 (1) SECOND step: titration of the metal in the organic phase: Neutral extractant E (either TODGA or T2EHDGA) added in small increments, while concentration of HA is held constant. Interaction of an adduct forming ligand with the metal complex preformed during the extraction can be described without other anions: (2) 13

13 Experimental Conditions Metal, Extracted with Titrant added (mm) 1M Conc. (M) Extractant Conc. (mm) Ligand:Ligand range (mm) Nd, 8.64 mm HDEHP 1.00 TODGA mM HDEHP 1.00 T2EHDGA mM HEH[EHP] 1.00 TODGA mM HEH[EHP] 1.00 T2EHDGA mM Ho, 12.9 mm HDEHP 1.00 TODGA mM HDEHP 1.00 T2EHDGA mM HEH[EHP] 1.00 TODGA mM HEH[EHP] 1.00 T2EHDGA mM Am, 0.56 mm HDEHP 1.00 TODGA mM HDEHP 1.00 T2EHDGA mM HEH[EHP] 1.00 TODGA mM HEH[EHP] 1.00 T2EHDGA mM

14 Nd Nd[H(DEHP) 2 ] 3 + TODGA Nd[H(DEHP) 2 ] 3 +T2EHDGA Nd(EH[EHP] 2 ) 3 + TODGA Nd(EH[EHP] 2 ) 3 +T2EHDGA

15 Nd Nd[H(DEHP) 2 ] 3 + TODGA Nd[H(DEHP) 2 ] 3 +T2EHDGA UV Vis Spectra of Nd 4 I 9/2 4 G 5/2, 2 G 7/2 Transition for:

16 Ho Ho[H(DEHP) 2 ] 3 + TODGA Ho[H(DEHP) 2 ] 3 +T2EHDGA Ho(EH[EHP] 2 ) 3 + TODGA Ho(EH[EHP] 2 ) 3 +T2EHDGA

17 Ho Ho[H(DEHP) 2 ] 3 + TODGA Ho[H(DEHP) 2 ] 3 +T2EHDGA

18 Am Am[H(DEHP) 2 ] 3 + TODGA Am[H(DEHP) 2 ] 3 +T2EHDGA Am(EH[EHP] 2 ) 3 + TODGA Am(EH[EHP] 2 ) 3 +T2EHDGA

19 Am Am[H(DEHP) 2 ] 3 + TODGA Am[H(DEHP) 2 ] 3 +T2EHDGA

20 Am -titration Am[H(DEHP) 2 ] 3 + TODGA Am[H(DEHP) 2 ] 3 +T2EHDGA Am(EH[EHP] 2 ) 3 + TODGA Am(EH[EHP] 2 ) 3 +T2EHDGA

21 Ternary Complexes of Metals (III) in mixed organic solvents: I. Solvation of Extracted Complex with DGA Ternary Complexes of Metals (III) in mixed organic solvents: I. Solvation of Extracted Complex with DGA Nd TODGA T2EHDGA HDEHP 2.33 ± ±0.01 HEH[EHP] 1.39 ±0.01, Ho TODGA T2EHDGA HDEHP 2.05 ± ±0.01 HEH[EHP] ± ± Am TODGA T2EHDGA HDEHP: L 2.86 ± HEH[EHP] O N O N O O O N T2EHDGA O N TODGA The equilibrium constants for this metal complexations have been determined using HypSpec

22 From Argonne NL: 1M HDEHP varying TODGA conc. Extraction from 50 mm DTPA/1M NH 4 Citrate ph Eu 60 D (Eu, Am) 10 1 Am slope ~ SF(Eu/Am) 0.1 Separation Factor [TODGA], mm

23 Conclusion Fundamental chemistry of ALSEP Radiatracer method to stability constant of extracted complexes HA DGA adducts (dry/wet) and extraction of acid Adduct formation (FTIR, Ln NMR, TRFLS.) Aggregation of extracted species SAXS XAFS investigation of the extracted complexes Translanthanide effect on complexation/separation behavior Effect of nitric acid and ionic strength of aqueous phase on speciation of complexes formed in organic phase

24 Acknowledgment: This worked was performed Brian J. Gullekson, a PhD candidate, in the Laboratory of Transuranic Elements at Oregon state University. With: Dr. Alena Paulenova, Director of the OSU TRU Lab Dr. Art Gelis, Leader of the Radiochemistry Group at ANL Acknowledgment: M. Alex Brown (PhD, OSU 2012, ANL, Radiochemistry Group) Dr. P. Tkac (post doc at OSU, now in ANL, Radiochemistry Group) Dr. J.L. Lapka (PhD, OSU 2013, postdoc WSU) DOE $$uport: NEUP award DE NE