Liquid–Liquid Extraction and Supported Liquid Membrane Transport of Neptunium(IV) Across a Flat-Sheet Supported Liquid Membrane Containing a TREN-DGA Derivative

Figures & data

Figure 1. Structures of TREN-DGA, i-Pr₃-TREN-DGA, TRPN-DGA, T-DGA, TAETEB, TODGA, and TREN-G1-DenDGA.

Figure 2. Schematic diagram of the glass transport cell used in the present study.

Figure 3. Extraction and stripping kinetics of (a) Np(IV), (b) Pu(IV) and (c) Th(IV) ions. Extraction: [TREN-G1-DenDGA]: 5.75 × 10⁻⁴ M in 5% isodecanol-95% n-dodecane; Aqueous phase: 3 M HNO₃ containing the metal ions. Stripping: Organic phase: Above extracted complex; Aqueous phase: 1 M α-HIBA.

Table 1. Stripping of Np(IV) extract in 5.75 × 10 ⁻⁴ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane with different stripping agents.

Stripping agent	DNp(IV)	% Stripping
0.5 M Oxalic acid + 0.5 M HNO3	2.50	28.6
0.1 M HEDTA + 0.5 M HNO3	0.50	66.7
0.1 M HEDTA + 0.05 M HNO3	0.10	90.9
1 M α-HIBA	0.03	97.1

Figure 4. D_Np(IV) at varying concentrations of (a) nitric acid with [TREN-G1-DenDGA]: 5.75 × 10⁻⁴ M in 5% isodecanol-95% n-dodecane and (b) TREN-G1-DenDGA at 3 M HNO₃; Temperature: 25ºC.

Table 2. D_Np(IV) values with different ligands in 5% isodecanol-95% n-dodecane at 3.0 M HNO₃.

Extractant	DNp(IV)	Ref.
1.0 × 10^−3 M TREN-DGA	3.8	[37]
1.0 × 10^−3 M T-DGA	15.5	[37]
1.0 × 10^−3 M TAETEB	42.8	[37]
5.75 × 10^−4 M TREN-G1-DenDGA	6.1 (10.6)^a	This work
1.0 × 10^−3 M TRPN-DGA	17.9	[29]
1.0 × 10^−3 M i-Pr3-TREN-DGA	147.1	[29]
5.0 × 10^−2 M TODGA	78.5	[29]

^aExtrapolated to 1.0 × 10⁻³ M with the assumption of a ML-extracted species.

Figure 5. Transport profile of Np(IV) across flat sheet SLMs from 1 M, 3 M and 6 M HNO₃ feed solutions using 5.75 × 10⁻⁴ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane. Stripping solution in receiver is 1 M α-HIBA.

Table 3. Slopes of log–log plot of D_Np(IV) versus TREN-G1-DenDGA concentration; extraction carried out at 3 M HNO₃.

Ligand	Slope	[Ligand]	Reference
TREN-DGA	1.49 ± 0.05	2 × 10^−4 − 1× 10^−3 M	[37]
TREN-G1-DenDGA	0.93 ± 0.06	1 × 10^−4 − 6 × 10^−4 M	This work
TRPN-DGA	1.15 ± 0.08	1 × 10^−4 − 1× 10^−3 M	[29]
i-Pr3-TREN-DGA	1.07 ± 0.07	1 × 10^−4 − 1× 10^−3 M	[29]

Table 4. Transport of Np(IV) from different feed nitric acid concentrations after 5 h. Receiver phase: 1 M α-HIBA, [Ligand]: 5.75 × 10⁻⁴ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane.

[HNO3], M	% Feed	% Transport	P × 10^3 (cm/s)
1	84.0 ± 4.2	14.8 ± 0.7	0.058 ± 0.003
3	72.0 ± 3.6^a,b	26.0 ± 1.3^a,b	0.121 ± 0.004
6	57.1 ± 2.8	41.2 ± 2.1	0.185 ± 0.007

^a1.0 × 10⁻³ M TRPN-DGA in 5% isodecanol-95% n-dodecane; Feed: 15.3%; Transport: 85.0%.

^b1.0 × 10⁻³ M i-Pr3-TREN-DGA in 5% isodecanol-95% n-dodecane; Feed: 9.4%: Transport: 88.7%. In both cases 5 h data. Strippant: 0.5 M oxalic acid + 0.5 M HNO₃.

Figure 6. Transport profile of Np(IV) across flat sheet SLMs from 3 M HNO₃ feed solutions using different concentrations of TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane. Stripping solution in receiver is 1 M α-HIBA.

Table 5. Transport of Np(IV) with different ligand concentrations in the membrane. Feed: 3 M nitric acid; Receiver phase: 1 M α-HIBA; [Ligand]: TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane; Data after 5 h.

[L], mM	% Feed	% Transport	P × 10^3 (cm/s)
0.575	72.0 ± 3.6	26.0 ± 1.3	0.121 ± 0.004
2.21	32.9 ± 1.6	64.6 ± 3.2	0.398 ± 0.006
4.42	15.4 ± 0.8	85.2 ± 4.3	0.643 ± 0.015

Figure 7. Transport profile of different actinide ions across a flat sheet supported liquid membrane from 3 M HNO₃ as feed phase and 1 M α-HIBA as stripping phase. [Ligand]: 4.42 x 10⁻³ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane.

Figure 8. Lag-Time of Np(IV) transport across a flat sheet SLM from 3 M HNO₃ as feed phase and 1 M α-HIBA as stripping phase. [Ligand]: 4.42 x 10⁻³ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane.

Table 6. Transport of different actinides from 3 M HNO₃ as feed acidity after 5 h. Receiver phase: 1 M α-HIBA; [Ligand]: 4.42 × 10⁻³ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane.

Metal ions	% Feed	% Transport	P × 10^3 (cm/s)	Reference^a
Th(IV)	27.8 ± 1.1	72.4 ± 2.9	0.446 ± 0.010	P.W.
Np(IV)	15.4 ± 0.6	85.2 ± 3.4	0.643 ± 0.015	P.W.
Pu(IV)	40.2 ± 1.6	60.5 ± 2.4	0.316 ± 0.030	P.W.
Am(III)	56.7	43.0	0.191 ± 0.007	[38]

^aP.W. = Present work.

Scheme 1. Pictorial depiction of the transport mechanism.

Table 7. Diffusion coefficients of Np(IV) determined by the lag-time and Wilke-Chang equations. Feed: 3 M HNO₃; Receiver: 1 M α-HIBA; [L]: 4.42 × 10 ⁻³ M TREN-G1-DenDGA in 5% isodecanol-95% n-dodecane.

Extractant	Lag-time (s)	Deff (cm^2/s) × 10^8	Do (cm^2/s) × 10^6	Ref.
TREN-G1-DenDGA	336 ± 7	1.56 ± 0.08	5.09	This work
TRPN-DGA	96.1 ± 5.0	7.13 ± 0.52	6.49	[29]
i-Pr3-TREN-DGA	78.6 ± 3.9	8.71 ± 0.61	6.51	[29]

Figure 9. Stability of the SLMs for Np(IV) transport studies. Feed: 3 M HNO₃; Strip: 1 M α -HIBA; [Ligand]: 4.42 x 10⁻³ M TREN-G1-DGA in 5% isodecanol-95% n-dodecane.

Table 8. Stability of the SLMs for Np(IV) transport studies. Feed nitric acid concentration: 3 M; Receiver phase: 1 M α-HIBA; [Ligand]: 4.42 × 10⁻³ M TREN-G1-DGA in 5% isodecanol-95% n-dodecane. Data after 5 h.

Day	% Feed	% Transport	P × 10^3 (cm/s)
1	15.4 ± 0.8	85.2 ± 4.3	0.643 ± 0.015
2	20.7 ± 1.0	79.0 ± 3.9	0.554 ± 0.003
5	50.8 ± 2.5	48.9 ± 2.4	0.241 ± 0.016

Gujar, R. B.; Mohapatra, P. K.; Verboom, W. Extraction of Np4+ and Pu4+ from Nitric Acid Feeds Using Three Types of Tripodal Diglycolamide Ligands. Sep. Purif. Technol. 2020, 247, 116986. DOI: 10.1016/j.seppur.2020.116986.

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Mahanty, B.; Verma, P. K.; Mohapatra, P. K.; Leoncini, A.; Huskens, J.; Verboom, W. Pertraction of Np(iv) and Pu(iv) Across a Flat Sheet Supported Liquid Membrane Containing Two N-Pivoted Tripodal Diglycolamides. Sep. Purif. Technol. 2020, 238, 116418. DOI: 10.1016/j.seppur.2019.116418.

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Mahanty, B.; Verma, P. K.; Mohapatra, P. K.; Leoncini, A.; Huskens, J.; Verboom, W. Pertraction of Americium(iii)/europium(iii) Ions Across a Flat Sheet Supported Liquid Membrane Containing a TREN Based Generation 1 Diglycolamide Dendrimer Ligand, Submitted for publication.

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