A New Customizable Surfactant LLPS Strategy for Sustainable and Highly Efficient Radioactive Metal Ion Separation

The traditional aqueous-organic biphasic extraction for separating radioactive metal ions faces major challenges due to heavy reliance on volatile organic solvents and the resulting refractory radioactive waste. Herein, we propose a customizable, sustainable, and efficient separation strategy for radioactive ions by using liquid-liquid phase separation (LLPS) phenomenon in two coexisting aqueous phases. Unlike conventional organic extraction systems, the LLPS platform operates without forming a bulk organic extraction phase. The LLPS is formed by sodium dodecyl sulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), and hexafluoroisopropyl alcohol (HFIP) (termed as SCH-extraction system) and enables customized encapsulation of commercial extractants. The selectivity of SCH-extraction system can be precisely tuned by adjusting parameters like the type of extractant and solution acidity, making it highly versatile for various separation scenarios. In simulated high-level liquid waste (HLLW), the strategy achieved the separation factors of ${\mathrm{UO}}_2^{2+}$ /Nd³⁺ reaching 2.33 × 10⁴, outperforming existing methods. This superior efficiency is driven by a dual mechanism: hydrophobic entrapment of metal-extractant complexes and electrostatic attraction to the negatively charged condensate interface. Based on this, a thermodynamic model is proposed, providing rational design principles for optimizing the system for diverse separation applications. This strategy holds significant promise for separating valuable radioactive metal ions.