Defect-rich N doped porous carbon derived from Camellia shells for chlorobenzene adsorption

Abstract

The preparation of efficient and cheap adsorbents is important for the removal of chlorinated volatile organic compounds, which are carcinogenic, teratogenic, and mutagenic to human health. In this study, ethylenediamine and ZnCl₂ were introduced simultaneously into Camellia oleifera shell-based biochar by the impregnation method. A series of nitrogen doped porous carbons (ANOC-x) were prepared by adjusting the ethylenediamine impregnation ratio combined with NaOH activation. Among them, the chlorobenzene adsorption capacity of ANOC-1.5 reached 1187 mg g⁻¹, which was 1.4 times that of undoped porous carbon. This was attributed to that ANOC-1.5 had the maximum specific surface area (2685 m² g⁻¹) and a hierarchical porous structure, which provided abundant adsorption sites and mass transfer channels for chlorobenzene adsorption. In addition, the chlorobenzene adsorption performance of porous carbon was highly correlated with surface defects, which was attributed to the fact that the surface of ANOC-1.5 (0.615 at%) contains more pyrrole heterocycles than AOC (0.258 at%), forming more π-electron rich defect sites. These defect sites had strong π–π interactions with chlorobenzene molecules, which could easily bind with the aromatic rings of chlorobenzene, thus improving the adsorption capacity of chlorobenzene. Moreover, ANOC-1.5 had high thermal stability and excellent regeneration performance, and its adsorption capacity for chlorobenzene remained above 90% after five regeneration tests, which exhibited potential for industrial applications.