Solvent Extraction of Technetium(VII) and Rhenium(VII) Using a Hexaoctylnitrilotriacetamide Extractant.

Area of Science:

• Radiochemistry
• Separation Science
• Materials Chemistry

Background:

• Pertechnetate (99TcO4-) and perrhenate (ReO4-) are challenging anions to remove from aqueous solutions.
• Existing extraction methods often lack efficiency or reusability.

Purpose of the Study:

• To evaluate the efficacy of a new tripodal extractant, N,N,N',N',N″,N″-hexa-n-octylnitrilotriacetamide (HONTA), for removing 99TcO4- and ReO4-.
• To compare HONTA's performance against other amine-type extractants.

Main Methods:

• Liquid-liquid extraction using HONTA, alkyldiamideamines (ADAAM(Oct), ADAAM(EH)), and trioctylamine (TOA).
• Extraction efficiency was studied across a range of pH conditions.
• Stripping and reusability of the extractant were assessed.

Main Results:

• HONTA quantitatively extracted both 99TcO4- and ReO4- within a pH range of 1.0 to 2.5 via co-extraction of protons.
• Extraction performance order was determined as HONTA > ADAAM(Oct) > ADAAM(EH) > TOA.
• Successful stripping was achieved using neutral aqueous solutions, and HONTA maintained its extraction ability after five cycles.

Conclusions:

• HONTA demonstrates superior performance for the liquid-liquid extraction of 99TcO4- and ReO4- compared to other tested extractants.
• The extractant is effective, reusable, and facilitates efficient separation of these critical anions.