Extraction and Selective Separation of Zr^IV from Ln^III/An^III Using an Undiluted Phosphonium Ionic Liquid

Area of Science:

• Radiochemistry
• Separation Science
• Materials Chemistry

Background:

• Selective separation of metal ions is crucial in nuclear fuel reprocessing and waste management.
• Ionic liquids offer unique properties for solvent extraction, but their application for specific separations requires detailed investigation.
• Zirconium (IV) separation from lanthanides (Ln(III)) and actinides (An(III)) presents a significant challenge in hydrometallurgy.

Purpose of the Study:

• To investigate the solvent extraction of zirconium (IV) using an undiluted phosphonium-based ionic liquid.
• To achieve selective separation of Zr(IV) from representative Ln(III) (Eu(III)) and An(III) (Am(III)).
• To explore the influence of experimental parameters on Zr(IV) extraction and understand the complexation mechanism.

Main Methods:

• Solvent extraction experiments using tri(hexyl)tetradecylphosphonium nitrate ([P66614][NO3]) as the ionic liquid phase.
• Systematic variation of nitric acid concentration, initial metal feed concentration, and equilibration time.
• Loading experiments to determine metal uptake capacity.
• Investigation of thermodynamics and stripping efficiency.

Main Results:

• Efficient extraction of Zr(IV) was achieved without external ligands, with negligible co-extraction of Eu(III) and Am(III).
• High separation factors for Zr(IV) over Eu(III)/Am(III) were obtained.
• The ionic liquid ([P66614][NO3]) demonstrated a significant loading capacity for Zr(IV).
• Nitrate anion was identified as a superior anion for metal loading compared to others.

Conclusions:

• The studied phosphonium-based ionic liquid is highly effective for the selective separation of Zr(IV) from Ln(III) and An(III).
• The findings support the potential application of this ionic liquid system in advanced nuclear fuel cycle processes.
• Further research into the thermodynamics and stripping behavior provides a basis for process design.