Extraction of pertechnetates from HNO₃ solutions into ionic liquids

Area of Science:

• Radiochemistry
• Separation Science
• Materials Chemistry

Background:

• Pertechnetate ions (Tc) pose challenges in nuclear waste management and require efficient separation methods.
• Ionic liquids (ILs) offer tunable properties for solvent extraction applications.
• Understanding the influence of nitric acid concentration and temperature on Tc extraction is crucial for process optimization.

Purpose of the Study:

• To evaluate the extraction efficiency of pertechnetate ions from aqueous nitric acid solutions into various hydrophobic ionic liquids.
• To investigate the effect of temperature and nitric acid concentration on the distribution ratio of technetium (D_Tc).
• To identify promising ionic liquids for effective pertechnetate separation.

Main Methods:

• Liquid-liquid extraction experiments were conducted using a series of hydrophobic ionic liquids.
• Varying concentrations of nitric acid and temperatures (25, 50, and 70 °C) were employed.
• Distribution ratios (D_Tc) were determined by measuring technetium concentrations in both aqueous and organic phases.

Main Results:

• The distribution ratio (D_Tc) exhibited weak dependence on temperature and nitric acid concentration for ILs with short aliphatic chains.
• Most ILs showed D_Tc values below 1.5, indicating limited extraction efficiency.
• Methyltrioctylammonium bis(trifluoromethylsulfonyl)imide demonstrated enhanced pertechnetate extraction, particularly at lower aqueous Tc concentrations.

Conclusions:

• Hydrophobic ionic liquids show potential for pertechnetate extraction, with performance varying based on IL structure and operating conditions.
• Methyltrioctylammonium bis(trifluoromethylsulfonyl)imide is a promising candidate for pertechnetate separation, especially under dilute conditions.
• Further research into IL functionalization and process optimization is warranted for efficient technetium management.