Development of Heavy Element Chemistry at Interfaces: Observing Actinide Complexes at the Oil/Water Interface in...

Area of Science:

• Chemistry
• Spectroscopy
• Chemical Engineering

Background:

• Understanding heavy element chemistry, particularly actinides, is crucial but challenging.
• Interface-selective spectroscopy offers a promising avenue for studying actinide species.
• Previous studies on actinide interfacial behavior are limited.

Purpose of the Study:

• To investigate the phase transfer mechanism of uranyl ions during solvent extraction.
• To probe the oil/water liquid-liquid interface using vibrational sum frequency generation (VSFG) spectroscopy.
• To elucidate the role of uranyl-HDEHP complexes in interfacial transfer.

Main Methods:

• Utilized vibrational sum frequency generation (VSFG) spectroscopy to analyze the oil/water interface.
• Employed di(2-ethylhexyl)phosphoric acid (HDEHP) as an extractant in a dodecane organic phase.
• Performed density functional theory (DFT) calculations to model interfacial complex structures.

Main Results:

• VSFG signals confirmed the formation of interfacial uranyl-HDEHP complexes at the oil/water interface.
• Uranyl ions from both aqueous and oil phases contributed to interfacial complex formation.
• The interfacial complex is proposed as a key intermediate for uranyl ion phase transfer.

Conclusions:

• Uranyl ions form interfacial complexes with HDEHP during solvent extraction.
• These interfacial complexes facilitate the transfer of uranyl ions across the oil/water interface.
• The study provides molecular insights into heavy element phase transfer mechanisms.