Effects of acid pickling and nitrogen doping on the biochar–NO reaction performance of different biochars under high O2 conditions

Abstract

Chinese fir (G type), elm (G-S type), and bamboo (G-S-H type) with different lignin types were used to prepare unmodified and modified biochars (modified by acid pickling, nitrogen doping, or both). Pore structures and functional group distributions of different biochars were characterized by Brunauer–Emmett–Teller analysis and Fourier transform infrared spectroscopy, and the key elements in biochar ash were semi-quantitatively determined by X-ray fluorescence spectroscopy and principal component analysis. Results showed that the different modification methods produce different NO removal performances. Both acid pickling and nitrogen doping improve the NO removal performance of elm-biochar—with its few defects—but not that of bamboo-biochar—with its high silicon content. In the case of Chinese-fir-biochar—with its high defect content, the improvement in NO removal performance is limited. The affinity of elements in biochar ash for oxygen atoms affects the nitrogen-doping as well as NO removal performance of biochar.