Ultrasound-Responsive Ionic Liquid for Selective Phase Transition Extraction of Zr(IV) Ions

Metal recovery has become a research hotspot because of the surge and release of heavy metals that are harmful to the environment. It is of great significance to explore green and efficient metal recovery methods. Here, we reported on an ultrasound-responsive ionic liquid N-hexadecyl-N,N-dimethyl-N-(4-sulfobutyl)ammonium nitrate (URIL) for the recovery of zirconium. URIL was provided with controllable reversible phase transition from microspheres to dispersed ions under the action of ultrasound stimulus in an acidic aqueous system. It is believed that the stimuli-responsive phase transition is a desirable property for metal recovery technology. As a practicable example, URIL was applied to metal extraction from acidic solutions, in which the strategy was proved to be efficient and selective. Experimentally, the maximum extraction efficiency to the targeted Zr(IV) species was 97.9%, and the maximum capture quantity was 88.9 mg/g. It also exhibited excellent selectivity to Zr(IV) species, which was 20-70 times that of partial transition metals, lanthanides, and actinides. Our work might be of instructive importance to metal recovery in the field of batteries, desalination, and so forth.