Extraction and coordination behavior of diphenyl hydrogen phosphine oxide towards actinides

Abstract

Extraction behavior of some selected actinides like U(VI), Th(IV), and Am(III) was investigated with three different H-phosphine oxides, viz. diphenyl hydrogen phosphine oxide (DPhPO), dihexyl hydrogen phosphine oxide (DHePO) and diphenyl phosphite (DPP). The H-phosphine oxides exhibited a dual nature towards the extraction of actinides where the ligand not only extracts the metals by cation exchange but also by coordination with the phosphoryl group at lower and higher acidic concentrations, respectively. Among all ligands employed, DPhPO showed highest extraction with actinides with a substituent dependent trend as follows: DPhPO > DHePO > DPP. This trend emphasizes the importance of substituents around the phosphine oxide towards their extraction of actinides. The coordination behavior of DPhPO was studied by investigating its corresponding complexes with Th(NO₃)₄ and UO₂(NO₃)₂. The metal complexes of these actinides were characterized using FT-IR, ¹H and ³¹P NMR spectroscopic techniques. Density Functional Theory (DFT) calculations were also performed to understand the electronic and geometric structure of the ligand and the corresponding metal complexes.

Keywords:

• Diphenyl hydrogen phosphine oxide
• coordination behavior
• solvent extraction
• uranium
• actinides

Acknowledgements

Kari thanks UGC-DAE, IGCAR-Kalpakkam, [CSR-KN/CRS-53/2013-14/652] for the financial support. Authors also thank DST-VIT-FIST for NMR, VIT-SIF for FT-IR and other instrumentation facilities. Authors gratefully acknowledge computing time on NEHA, the High-Performance Computing Facility at IGCAR, India.