The Effects of Nitrogen Flow during Carbonization on Enrofloxacin, Methylene Blue, and Phospholipids Adsorption by Silk Sericin-Derived Carbon

The effect of nitrogen flow during carbonization on bioderived carbon's adsorption performance has not been thoroughly investigated. To fill the gap, the adsorption behavior of silk sericin-based carbon prepared under three different nitrogen flow conditions: (i) without nitrogen flow, (ii) with continuous nitrogen flow, and (iii) with nitrogen flow ceased after heating to 150 °C, were evaluated. In aqueous environments, the CS prepared without nitrogen flow during carbonization exhibited the largest specific surface area and the highest adsorption capacities for methylene blue and enrofloxacin. In contrast, in oil-phase environments, the CS-N₂─prepared by ceasing nitrogen flow after heating to 150 °C during carbonization and containing abundant C═C functional groups─demonstrated superior adsorption performance for phospholipids and polyphenols in idesia polycarpa oil. These findings confirm that the secondary interactions between volatile byproducts and the carbon framework during carbonization play a crucial role in regulating pore development and surface chemistry of silk sericin-based carbon. Besides, the results reveal that the tailored design of silk sericin-based carbon for specific adsorbates is possible by controlling the nitrogen flow during carbonization. This work not only offers new insights into the efficient utilization of waste silk resources but also provides a theoretical foundation for the controlled synthesis of bioderived carbon. Our work represents the first systematic study of how nitrogen flow impacts the adsorption performance of silk sericin-derived carbon.