Insight into the significant contribution of intrinsic defects of carbon-based materials for the efficient removal of tetracycline antibiotics

Due to their high adsorption capacity and low cost, carbon-based materials have experienced great progress in the removal of tetracyclines. Unfortunately, the nature of the adsorption site is far from clarified. Especially, it is still a great challenge to systematically explore the impact of intrinsic defects of carbon-based adsorbents on the adsorption of tetracyclines. Herein, carbon-based adsorbents with different defects were designed and prepared, and their adsorption properties of tetracyclines were systematically studied. From microscopic characterization of carbon-based adsorbents and batch adsorption experiments, the intrinsic defects of carbon-based adsorbents facilitated the adsorption performance of tetracyclines. The best adsorbent (SSG-C) had a very high adsorption capacity (526.9 mg/g for tetracycline (TTC); 360.9 mg/g for oxytetracycline (OTC)). Additionally, density functional theory simulation results show that the ring defects of sp 2 species promoted the adsorption performance more than sp 3 edge defects, and the adsorption performance increased with increasing ring defect of sp 2 species. Based on the above analysis, we proposed that intrinsic carbon defects activate the π electrons of sp 2 carbon and facilitate π-π interaction between carbon-based adsorbents and tetracyclines, particularly the ring defects of sp 2 species. This study provides a decisive contribution to better understanding of the role of intrinsic defects in carbon-based adsorbents for removal of tetracyclines.