Modulation of TSIL-Based Ciprofloxacin Structures with pH for the Selective Extraction of Rare Earth Metals, Uranium, Thorium, Titanium, and Zinc

We report a novel Task-Specific Ionic Liquid (TSIL) derived from ciprofloxacin in combination with CYPHOS·NTf2 that enables tunable selectivity toward the extraction of rare earth metal elements (REEs), thorium, uranium, titanium, and zinc. The highest metal-TSIL affinity was found at pH 6, showing the highest extraction coefficient values for thorium (446), uranium (404), Sc (307), and the remaining REEs, titanium, and zinc (238–71.5; 99; 98). Under highly acidic solutions, however, the TSIL only showed affinity for thorium but not for the remaining species. The metal-cation complexation has been studied by means of NMR spectroscopy and in silico DFT-based optimization of the complexes. The recyclability of the extractive system (up to seven extraction cycles) has also been proved.