Fabrication of sulfonic acid-functionalized activated carbon from waste cation exchange resins for chloramphenicol adsorption: Performance and theoretical calculation

To reduce the adverse effect on the environment caused by residual antibiotics, sulfonic acid-functionalized activated carbon (CWCR) was prepared from waste cation exchange resins (WCER) to adsorb chloramphenicol (CAP). Its characterization and adsorption performance were employed to investigate the mechanism of action. CWCR attained a high adsorption capacity of 273.76 mg/g and achieved the removal of 98 % for CAP. The pseudo-second order model and the Freundlich model exhibited higher correlation for the adsorption data, indicating that the adsorption process was a multi-layer adsorption. The negative values of the thermodynamic parameters confirmed a spontaneous and exothermic adsorption process. DFT calculations further confirmed the synergistic role of -SO₃H groups in forming hydrogen bonds, as well as significant π-π interactions and ion exchange. CWCR exhibited strong ionic interference resistance and maintained high adsorption at the pH of 3.0–11.0. CWCR maintained the removal of 72 % in the eighth regeneration. The Thomas model was found to be more applicable than the Yoon-Nelson model in the fixed-bed adsorption. These results indicated that CWCR was a cost-effective and sustainable adsorbent for removing antibiotics from aqueous solutions.