Influence of different precursors on the characteristic of nitrogen-enriched biochar and SO2 adsorption properties

Abstract Biochars with different physicochemical properties will lead to different characteristics of nitrogen-enriched biochars obtained via modification, thereby affecting their SO2 capture characteristics. In this study, different feedstock types (peanut shells, corn stalks and corncobs), different activation condition were used to obtain the precursors for the preparation of nitrogen-enriched biochar via the methyldiethanolamine-methanol impregnation method to explore the influence of different precursors (raw biochar) on the characteristics of the nitrogen-enriched biochars and their SO2 adsorption properties. In addition, the SO2-adsorption process on nitrogen-enriched biochar in coal-fired power plants was simulated by fixed-bed experiments and the effects of the adsorption temperature, oxygen content, humidity and NO concentration on the SO2-adsorption capacities were investigated. The results show that the nitrogen content shows a stronger linear relationship with the micropore volume than that with the non-micropore volume, with the highest nitrogen content of biochars (CCAN850) reaching 9.50%. In the presence of O2 and a low concentration of NO (500 ppm), the SO2-adsorption capacity of CCAN850 increased to 216.19 mg/g at 120 °C. X-ray photoelectron spectroscopy (XPS) showed that the SO2-adsorption site of the nitrogen-enriched biochar is mainly quaternary nitrogen and the presence of NO promoted the combination of SO2 and NO that facilitated the adsorption of these compounds in the form of nitrogen and sulfur. This increased the SO2-adsorption capacity of the nitrogen-enriched biochar.