Oxygen-containing groups in cellulose- and lignin-biochar: their roles in U(VI) adsorption

Abstract The adsorption behaviors of cellulose- and lignin-biochar depend on their oxygen-containing groups to some extent. In this study, a series of cellulose- and lignin-rich biochar was prepared from pakchoi and corncob, respectively named PBC and CBC, to evaluate their adsorption properties for U(VI). The maximal adsorption capacity of PBC 300 (obtained at 300 oC) was 46.62 mg g− 1 for U(VI), which was ⁓ 1.3 times higher than that of CBC 300 (35.60 mg g− 1). U(VI) adsorption on PBC and CBC were ascribed to the coordination interaction between oxygen-containing groups and U(VI). Interestingly, the main complexation groups were different in the both biochar due to the inherent evolution of cellulose and lignin. Volatile d-glucose chains in cellulose were apt to degrade rapidly, and the formed carboxyls acted as the main adsorption sites in PBC. However, the stable aromatic network in lignin led to a slow degradation, and more hydroxyls thus remained in CBC, which controlled U(VI) adsorption. This study obtained effective adsorbents of U(VI) and provided some essential insights into understanding this evolution and structure-function relationship of biochar.