A Dicationic Ionic Liquid with Trinity Performance: Rapid, High-Capacity and Stable Capture of ⁹⁹ TcO ₄ – / ReO ₄ – under Extreme Conditions

99 Tc, as an extremely hazardous radioisotope, makes the development of green environmental purification materials to capture 99 Tc from water an exceedingly urgent issue; however, achieving deep purification under complex conditions, such as strong acidity/alkalinity, high radiation, and excessive competing anions, is particularly challenging. This study pioneers a dicationic ionic liquid, PPh 3 PrPPh 3 [Br] 2, based on quaternary phosphonium salts, achieving a “trinity” performance breakthrough─rapid (1 min extraction equilibrium), high (562.22 mg·g –1 capacity), and excellent stability─in capturing high-risk nuclides 99 TcO 4 – /ReO 4 – . PPh 3 PrPPh 3 [Br] 2 integrates extreme environmental resilience (tolerance to strong acids/alkalis, intense radiation, and high temperatures), multianion interference resistance (>85% removal rate in simulated Hanford wastewater), and exceptional reusability (negligible efficiency loss after 10 cycles). Using multiple characterization techniques (FTIR, XRD, XPS, SEM, EDS) combined with quantum chemical simulations, the extraction mechanism was identified as synergistically driven by Br – /ReO 4 – exchange and electrostatic interactions between ReO 4 – and the phosphonium cation (P/phenyl sites). PPh 3 PrPPh 3 [Br] 2 maintains its rigid dicationic skeleton intact throughout the ion-exchange process, thereby fundamentally avoiding degradation arising from its own instability and the generation of secondary organic halide pollutants. A preliminary environmental safety assessment confirms that the released Br – concentration is far below discharge limits and poses no secondary pollution risk; it is extremely low water solubility (only 1.62% Br – leaching after 24 h) and the inherently low ecotoxicity of phosphonium-based ionic liquids further ensure environmental compatibility during use. Notably, PPh 3 PrPPh 3 [Br] 2 demonstrates exceptionally low processing costs ($0.23·g –1 ), representing the lowest cost among all reported ReO 4 – treatment materials to date. It not only provides a pioneering and viable solution for radioactive wastewater treatment but also lays a crucial foundation for the practical application of this ionic liquid in the management of radioactive nuclear effluents.