Adsorption removal of PCDD/Fs from flue gas is one of the important technologies for reducing environmental PCDD/Fs emissions. However, due to the lack of systematic research on the adsorption mechanism of PCDD/Fs, commercial activated carbon (AC) with a single pore size distribution and lack of surface functional groups has poor adsorption and removal efficiency for PCDD/Fs. Therefore, this study first used corncob as a raw material and prepared N-doped hierarchical porous biochar (NHPB) using a one-step activation method for efficient removal of PCDD/Fs. The removal efficiency of NHPB for 17 toxic PCDD/Fs and 136 PCDD/Fs in simulated flue gas is as high as 96.21% and 97.21%, respectively. Compared with AC, the adsorption performance of NHPB was significantly less affected by the fluctuation of temperature and concentration than AC because the adsorption performance changed little with the chlorine substitution number of PCDD/Fs, and showed excellent adsorption performance under various adsorption conditions. Subsequently, the adsorption mechanism of PCDD/Fs on NHPB was systematically studied using theoretical calculations. Molecular simulations show that the optimal adsorption pore size for PCDD/Fs is mainly micropores above 1 nm and mesopores between 2 and 5 nm. Therefore, the hierarchical pore structure of NHPB exhibits superior adsorption performance. Density functional theory (DFT) calculations show that all three N-doping forms on the surface of biochar can enhance the adsorption energy of PCDD/Fs on biochar, thereby further enhancing the adsorption performance of NHPB for PCDD/Fs.
Keywords: Hierarchical porous biochar; Mechanism analysis; N-doping; PCDD/Fs adsorption; Theoretical calculation.
Copyright © 2024 Elsevier Ltd. All rights reserved.