Preferential elimination of negatively charged micropollutants in water over cerium-based metal–organic frameworks

Abstract

In this study, three groups of harmful chemicals at trace amounts (μg/L) in water with extremely high environmental risk were preferentially removed over cerium-based UiO-66 and MOF-808, including nonsteroidal anti-inflammatory drugs (NSAIDs), quinone antibiotics, and perfluoroalkyl carboxylic acids (PFCAs). Results found that cerium-oxygen clusters with oxygen vacancies and larger pore sizes effectively adsorbed targets by both chemical and physical mechanisms. Remarkably, log Kow of five PFCAs (PFPeA, PFHxA, PFOA, PFNA, PFDA) with increasing lengths of alkyl chains strongly correlated (R2 = ∼0.99) with ln (v0) and Qe. In contrast, Ce-MOFs rapidly adsorbed NSAIDs and quinone antibiotics, ranking the excellent adsorbents reported so far (e.g., Qe, OFC = 419.8 mg/g on MOF-808). Hydrophobic, diffusion, and electrostatic interaction mechanism were systematically studied using mathematic models, including pseudo first/second-order, Elovich, and Weber-Morris intraparticle diffusion ones. Thanks to the generation of reactive species (e.g., •OH, 1O2, •O2– and oxygen vacancies) over cerium-oxygen clusters under the irradiation of solar light, aromatic NSAIDs were completely decomposed (>99 %) within 60 min. This study offers helpful guidance for the preferential removal of ECs in water.