Study on the adsorption mechanism of NO/C3H6O on the surface of metallic calcium coupled nitrogen-doped biochar

Abstract

The introduction of nitrogen sources and metal minerals can significantly promote the adsorption of gases on the biochar surface. However, the mechanisms by which different nitrogen-containing functional groups affect the gas adsorption characteristics on the surface of biochar are different. The addition of minerals increases the complexity of the gas adsorption mechanism of nitrogen-containing biochar, and the gas adsorption mechanism of different nitrogen groups coupled minerals on the surface of biochar is not yet clear. This study uses a combination of experiments and theoretical calculations and introduces urea and the typical mineral Ca to investigate the adsorption mechanism of NO/C₃H₆O on the surface of biochar influenced by doping of different nitrogen-containing functional groups and CaO. Experimental results indicate that at a low-concentration urea blending ratio, the N functional group in biochar mainly exists as N-5. Pyrolysis experiments with different activation temperatures and residence times are conducted on pyrrole nitrogen-rich biochar (CN1). The results indicate that activation for 1 h at 700 °C is more conducive to the formation of pyrrole nitrogen, and CN1-700-1 has the best gas adsorption performance. The introduction of Ca changes the interaction between molecules and biochar surface from physical adsorption to chemical adsorption with higher selectivity and stronger adsorption capacity, which significantly improves the adsorption performance of biochar. Both the experimental and theoretical calculation results of this study show that the coupling of the N-5 functional group with Ca improves the adsorption performance of biochar and provides theoretical support for the development of multifunctional and efficient adsorbents.