Engineering NSAIDs imprinted UiO-66s for markedly enhanced adsorption of coexisting diclofenac sodium and Cu(II) and their synergistic adsorption mechanism

Abstract

Competitive adsorption of complex nonsteroidal anti-inflammatory drugs (NSAIDs) from wastewater often reduces the adsorption capacity of object pollutants on most porous materials. To addressthis issue, NSAIDs molecules were proposed for engineering imprinted pores in UiO-66s to boost their adsorption capacity towards diclofenac sodium (DCF)and Cu(II) in a complex solution. Naproxen (NAP) with proper chemical structure was proved to introduce more imprinted pores (at ~19 Å) with enhanced mesoporous volume, abundant unsaturated metal sites, and terminal hydroxyl groups in UiO-66@NAP. These new intriguing properties awarded high adsorption affinity to UiO-66@NAP for DCF and Cu(II), and their adsorption capacities reached up to 385 and 52 mg/g for single DCF and Cu(II) components, respectively. When DCF and Cu(II) simultaneously appeared in an aqueous solution, DCF was proved to preferentially occupy adsorption sites on UiO-66@NAP with higher adsorption kinetics compared to Cu(II). Afterwards, these pre-adsorbed DCF acted as new adsorption sites to bridge more Cu(II) in the solution. Similarly, the adsorbed Cu(II) on UiO-66@NAP had the same reciprocal bridging effect towards DCF, which realized the synergistic adsorption of DCF and Cu(II) over UiO-66@NAP. Notably, DCF was found to greatly boost the synergistic effect of the Cu(II) adsorption. As a result, UiO-66@NAP exhibited 1.5 and 2.6 times higher uptakes for DCF (573 mg/g) and Cu(II) (135 mg/g) in the binary system compared to their single pollutant system, and its equilibrium adsorption capacity was much higher compared to several state-of-the-art adsorbents. The current work set out a new strategy to modify MOFs for enhanced adsorption of complex NSAID contaminants and revealed a deep understanding of the interactions between NSAIDs and heavy metals ions.