Highly Efficient Pertraction of Tetravalent Neptunium Ions Across a Flat Sheet Supported Liquid Membrane Containing Two Different Aza-Crown Ether-Based Multiple Diglycolamide Ligands

ABSTRACT

Pertraction of Np(IV) across a PTFE membrane containing two different aza-crown ether-based multiple diglycolamide (DGA) ligands termed as L_I (3 DGA arms) or L_II (4 DGA arms) was investigated using nitric acid as feed solution. A few of the studies were also carried out with Pu(IV) for comparison purposes. The kinetics of the extraction of Np(IV) and Pu(IV) was fast at 3 M HNO₃ and within 10 min reaches the equilibrium distribution (D) ratio with both ligands. However, the stripping kinetics was slower especially with ligand L_II. The extraction and transport studies were carried out using 1.0 × 10⁻³ M ligand solution in 95% n-dodecane + 5% isodecanol. The transport rates were slower with ligand L_II than with L_I at higher nitric acid concentrations (>1 M HNO₃) and the transport rates decreased with nitric acid concentration with both ligands. The effective diffusion coefficients (D_eff) of Np(IV) were estimated using the lag-time method as 6.2 × 10⁻⁸ cm² s⁻¹ (L_I) and 4.6 × 10⁻⁸ cm² s⁻¹ (L_II). The stability data suggest that the L_I containing supported liquid membrane (SLM) is comparatively more stable than that of L_II and the transport flux remains the same up to nine days of operation in case of ligand L_I.

KEYWORDS:

• Actinide
• nitric acid
• transport
• ligand
• lag-time

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07366299.2022.2156798