Multiple active sites driven synergistic removal of typical antibiotics and heavy metals from wastewater by calcium alginate immobilized Fe-based MOF

The combined pollution of antibiotics and heavy metals exacerbates dissemination of antibiotic resistance genes (ARGs). However, simultaneously and efficiently removing both pollutants with traditional adsorbents is highly challenging because of their limited number of active sites. Based on a multi-site synergy strategy, powdered NH 2 -MIL-101(Fe) was encapsulated into porous calcium alginate (CA) aerogel to produce a novel NH 2 -MIL-101(Fe)@CA composite that overcomes the above shortcomings. NH 2 -MIL-101(Fe) and CA act synergistically to enhance the adsorption of ciprofloxacin (CIP) and Cu 2+ by providing multiple sorption sites (e.g., -COOH, -OH, -NH 2 , and aromatic ring). Both pollutants exhibit the same optimal pH in their individual systems, enabling simultaneous and efficient removal from their mixed solution. At 25 °C, the maximum CIP adsorption capacity reaches up to 1072.06 mg/g, surpassing that of most recently reported adsorbents. Electrostatic attraction, complexation, hydrogen bond, and π-π EDA interactions are all shown to contribute to CIP and Cu 2+ removal. Intriguingly, in CIP/Cu 2+ binary system, Cu 2+ inhibits CIP adsorption because of competitive effects and formation of Cu(CIP ± ) 2+ complexes in aqueous solution. Conversely, Cu 2+ adsorption increases by 62.4 % in the presence of CIP, because the pre-adsorbed CIP supplies additional coordination sites (-COOH, -OH, and C O) for Cu 2+ to form adsorbent-CIP-Cu 2+ ternary complex. In-situ characterization and sequential adsorption experiments verify these interaction patterns. Moreover, the resultant composite achieves simultaneous removal rate of approximately 90 % for CIP and Cu 2+ in simulated wastewater, demonstrating its great potential for treating complex water matrices. This work provides theoretical guidance for designing versatile adsorbents that target antibiotics and heavy metals and offers new insights into interactions between multiple co-existing pollutants.