Bimetallic-doped carbon microspheres functionalized with 2-methylimidazole for enhanced adsorption of tetracyclines in wastewater

Chitosan-derived carbon microspheres (CMs) are potential adsorbents for antibiotics wastewater treatment due to their plentiful amino and hydroxyl groups. However, a pressing challenge for their practical application is how to enrich the adsorption site to further improve the adsorption capacity. Here, a novel adsorbent via 2-methylimidazole (2MIm) functionalization of bimetallic Cu/Al doped CMs (denoted as 2MIm-Cu/Al@CMs x ) was constructed through a facile hydrothermal method and a subsequent immersion step. The optimized material of 2MIm-Cu/Al@CMs 50 achieved maximum adsorption capacity of 1616.49   mg   g -1 for tetracycline (TC) with the initial concetration of 500   mg   L -1 and the adsorbent dosage of 5   mg (25 °C), showing 64.62% growth compared to the non-functionalized Cu/Al@CMs counterpart. The improved adsorption performance was attributed to the additional Cu-N sites and π-π interactions via 2MIm modification, working synergistically with hydrogen bonding, electrostatic attraction, and metal complexation. Systematic adsorption kinetics, isotherms and thermodynamics analysis revealed that the adsorption of TC on 2MIm-Cu/Al@CMs 50 was spontaneous and endothermic, and obeyed the pseudo-second-order kinetic and Langmuir isotherm models. Besides, 2MIm-Cu/Al@CMs 50 exhibited excellent reusability, and practical potential in real wastewater. This work provides a strategic design of functionalized CMs for the efficient removal of antibiotic pollutants.