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 sp2 species promoted the adsorption performance more than sp3 edge defects, and the adsorption performance increased with increasing ring defect of sp2 species. Based on the above analysis, we proposed that intrinsic carbon defects activate the π electrons of sp2 carbon and facilitate π-π interaction between carbon-based adsorbents and tetracyclines, particularly the ring defects of sp2 species. This study provides a decisive contribution to better understanding of the role of intrinsic defects in carbon-based adsorbents for removal of tetracyclines.