Removal of Antibiotics Vancomycin and Rifampicin from Water by Granular Activated Carbon

In this study, the removal of vancomycin and rifampicin from aqueous media by three types of granular activated carbon was investigated under a wide range of operational conditions. There is growing concern about antimicrobial resistance to vancomycin, a last-line antibiotic for serious Gram-positive infections, and rifampicin, a key component of first-line combination therapy for tuberculosis. However, there has been little research into adsorption of these antibiotics from aquatic environments. Effect of temperature (5–45 °C), pH (3–11), contact time (up to 336 h) and the adsorbate initial concentration (5–100 µg.mL⁻¹) were evaluated on removal efficiency and uptake of the antibiotics by activated carbon from water. The results showed that all adsorption processes in this study were mainly controlled by physisorption, as they exhibited the enthalpy values between 5.97 kJ.mol⁻¹ to 21.19 kJ.mol⁻¹ (i.e., lower than 40 kJ.mol⁻¹). Temperature had a limited impact on the adsorption process. On the other hand, the contact time, initial adsorbate concentration and solution pH had a substantial effect in removing and retaining the studied antibiotics from water. The attributes of the antibiotics and the pore characteristics of the adsorbents determined the effectiveness of adsorption. Intra-particle diffusion assessments identified that the rate of the studied antibiotics’ removal from water is not controlled only by intra-particle diffusion and follows the sequential transport mechanisms, containing three steps for vancomycin (bulk transfer, passage through the boundary layer and diffusion into micropores) and two steps for rifampicin (passing through the boundary layer and diffusion into mesopores).