Reversible Hydrophobic Deep Eutectic Solvent-Based Uranyl-Sensing Optode Film in Aqueous Streams: Color Transformation and Reusability

A hydrophobic deep eutectic solvent (HDES)-based optode was designed for the preconcentration and determination of the UO22+ ion in aqueous media using spectroscopic techniques [energy-dispersive X-ray fluorescence (EDXRF) and solid-state absorption]. The optode was developed by incorporation of HDES (tri-n-octyl phosphine oxide and decanoic acid in an equimolar ratio), tri-(2-ethylhexyl) phosphate, and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol into a cellulose triacetate matrix. Characterization studies were carried out using different techniques to understand the roles of HDES as a plasticizer, UO22+ extractant, and Br-PADAP immobilizer. Uptake studies revealed that the optimal pH was 3 and sorption followed the type II adsorption isotherm. Uranium in the U-sorbed optode can be directly analyzed over a large concentration range of 0.021 × 10-3-2.1 × 10-3 Mol L-1 using EDXRF. The optode film exhibited a linear dynamic range of 0.84 × 10-6-84 × 10-6 Mol L-1 for uranium, with a lowest limit of detection of 0.084 × 10-6 Mol L-1 by colorimetric analysis. This optode-based method was employed for seawater analysis for its UO22+ concentration without any matrix separation, and the concentration was found to be 1.30 ± 0.06 × 10-8 Mol L-1. The optode exhibited better selectivity for UO22+ in the presence of various cations including Sr2+ and Cs+ in an aqueous medium. Compared to other prevailing optical sensors, this optode performed better in terms of key factors like pH, equilibration time, reusability, and detection limit.

Selective Extraction of Thorium(IV) from Uranium and Rare Earth Elements Using Tetraphenylethane-1,2-diylbis(phosphoramidate)

Tetraphenylethane-1,2-diylbis(phosphoramidate) in conjugation with a room temperature ionic liquid in chloroform medium is reported for the first time in the liquid-liquid extraction of thorium (Th). The extracted Th(IV) is collected as a white solid in the organic medium, thereby facilitating its easy separation. A high distribution ratio (D) of (12.4 ± 0.1) × 10³ in 2-8 mol L^-1 acidity range and high decontamination factors (α) of Th(IV) from uranium, lanthanides, and a number of transition elements makes this extraction process versatile and selective. A number of experimental investigations in synergism with extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) studies are interpreted to confirm the structure of the chelated complex. A 1:2 metal/ligand complex in which the two oxygen and two nitrogen atoms of each bis(phosphoramidate) molecule satisfying the eight coordination sites of Th(IV) is found to be formed. The extracted white solid thorium complex is easily converted to ThO₂ after washing and heating at 1300 °C under O₂ atmosphere. This work is expected to find direct application in the thorium fuel cycle, especially in the mining process of thorium from its ores and in the separation of fissile ²³³U from fertile ²³²Th in irradiated fuel.

A review of the alpha radiolysis of extractants for actinide lanthanide separation in spent nuclear fuel reprocessing

Radiation stability is one of the key properties to enable the efficient use of extractants in spent nuclear fuel with high radioactivity. The last several decades have witnessed a rapid progress in the radiation chemistry of extractants. A variety of studies and reviews pertinent to the radiation stability of extractants have been published. However, a thorough summary for the alpha radiolysis results of extractants is not available. In this review, we survey the development of alpha radiolysis of extractants for actinide lanthanide separation and compare their radiolysis behaviors induced by alpha particles and gamma rays. The discussion of alpha radiolysis of extractants is divided into three parts according to the functional groups of extractants (i.e., phosphine oxide, amide and bis-triazinyl bipyridines). Given the importance of radiation source to carry out alpha irradiation experiment, we first give a brief introduction to three practicable alpha radiation sources including alpha emitting isotopes, helium ion beam and reactor. We hope this review will provide useful information and unleash a broad palette of opportunities for researchers interested in radiation chemistry.

Opening up the Toolbox: Synthesis and Mechanisms of Phosphoramidates

This review covers the main synthetic routes to and the corresponding mechanisms of phosphoramidate formation. The synthetic routes can be separated into six categories: salt elimination, oxidative cross-coupling, azide, reduction, hydrophosphinylation, and phosphoramidate-aldehyde-dienophile (PAD). Examples of some important compounds synthesized through these routes are provided. As an important class of organophosphorus compounds, the applications of phosphoramidate compounds, are also briefly introduced.