Decisive role of adsorption affinity in antibiotic adsorption on a positively charged MnFeO@CAC hybrid.

The discharge and consequent occurrence of antibiotics in the environment has led to increasing concerns because their presence can promote the development of resistance genes, which in turn pose a significant health risk. A key process to control the transport and risk of antibiotics is adsorption. Thus, we investigated the adsorption mechanisms of six typical antibiotics onto a MnFeO@cellulose activated carbon (CAC) hybrid combining batch adsorption experiments and quantum chemical calculations. In the single-adsorbate adsorption systems, the solid-phase concentrations of the adsorbates varied from 152.8 to 395.7 mg/g, which were dependent on the adsorption affinity and molecular structures or sizes of the antibiotics. Chemisorption was the main adsorption mechanism, and it was driven by p-d electronic conjugation and cation-π interactions. In the competitive adsorption systems, the solid-phase concentrations of both primary (sulfamethazine, SMT) and secondary (the other five antibiotics) adsorbates decreased significantly. The decrease ratio of SMT varied from 15.42% to 67.28% while that of the secondary adsorbates varied from 14.13% to 52.74%. The "competition" strength was depended on the adsorption energy and the overlapping of adsorption sites. We believe that these findings will provide a better understanding of the adsorption characteristics of typical antibiotics and facilitate the strategy developing for the removal of antibiotics from the aqueous phase.