Aqueous Biphase Systems for Liquid/Liquid Extraction of f-Elements Utilizing Polyethylene Glycols

Abstract

Aqueous biphasic systems formed by adding a H₂O soluble polymer (polyethylene glycol) to an aqueous salt solution ((NH₄)₂SO₄ or K₂CO₃) have been investigated for use in extracting aqueous Am³⁺, Pu⁴⁺, UO₂ ²⁺, and Th⁴⁺ ions into the polymer-rich phase. Extraction occurs only in the presence of complexing dyes which preferentially partition to the polymer-rich phase. Three such dyes, arsenazo III, alizarin complexone, and xylenol orange were investigated. Arsenazo III extracts all four metal ions from SO₄ ^2- media but not from CO₃ ^2- solutions. Alizarin complexone quantitatively extracts Th⁴⁺ and Pu⁴⁺ from SO₄ ^2- media, while Am³⁺ is the best extracted ion in CO₃ ^2- solution. Xylenol orange extracts only Am³⁺ from CO₃ ^2- media. In SO₄ ^2- solutions low concentrations of xylenol orange extract Th⁴⁺ and Pu⁴⁺, while Am³⁺ and UO₂ ²⁺ are extracted at higher concentrations of xylenol orange. H₂SO₄ can be used to strip the metal ions, while NH₄OH often but not always enhances the extraction.