Ionic liquid-functionalized transition-metal oxides as highly recyclable and efficient nano-adsorbent for fluoride removal

Abstract

The modification of functionalized ionic liquids into sewage adsorbents addresses key limitations of traditional adsorption methods, offering enhanced selectivity, good adsorption, and renewability. In this work, imidazole-amino ionic liquid was successfully modified into transition-metal oxide CuOX through coordination interactions between the imidazole ring and Cu+. Most importantly, specific and thermal-responsive hydrogen bonds between amino and fluoride exhibited excellent selectivity for capturing fluorine while providing effective renewability through thermal activation. As expected, the adsorbents exhibited a rapid adsorption rate in fluorine solution (adsorption saturation time tS = 38 h, fluoride concentration 2 mg·L−1) and significant adsorption capacity (maximum adsorption capacity qm = 337.8 mg·g−1, 293 K). Moreover, a recovery rate was exceeded 95 % after incubation with the boiling water. As for industrial application, the adsorbent demonstrated an impressive fluoride removal efficiency exceeding 80 % and a remarkable recovery rate exceeding 70 % when treating wastewater from the photovoltaic cell and semiconductor industry. This not only significantly reduced expenses associated with wastewater treatment but also alleviated the incidence of secondary pollution. By offering a recyclable and effective solution for sewage adsorbents, this strategy holds promise for addressing water pollution challenges in industrial settings.