Nitrogen-doped biochar derived from corn straw for CO2 adsorption: a new vision on nitrogen sources comparison.

Biochar as a highly promising CO₂ adsorbent is of great significance in addressing global warming and promoting human health. Research has shown that nitrogen doping improves the CO₂ adsorption performance of biochar, but selecting chemical nitrogen sources such as urea and melamine to prepare nitrogen-doped biochar is not conducive to green production and environmental protection. Therefore, it is necessary to identify a new nitrogen source to enhance the emission reduction characteristics of this process. This study selected corn straw as the raw material and cow manure as a representative protein-based nitrogen source to explore its potential as a urea substitute and reveal the hydrothermal carbonization doping mechanism of different nitrogen sources. The results indicated that in raw materials with the same C/N ratio, biochar prepared from cow manure as the nitrogen source had a better doping effect and CO₂ adsorption performance. Moreover, a moderate amount of cow manure was beneficial for efficient nitrogen doping and the adsorption of CO₂ by biochar, with a maximum CO₂ adsorption performance improvement of 32.7%. Due to the different carbon-nitrogen bonds of the different nitrogen sources, urea was more likely to retain amino groups, while macromolecular protein nitrogen sources tended to retain structural nitrogen. The results of this study provide new ideas and theoretical support for preparing other nitrogen-doped carbon materials derived from biomass. Highlights: • Doping effect of cow manure is stronger than urea under the same C/N value of raw materials. • Moderate addition of cow manure is beneficial for nitrogen doping of biochar. • Small-molecule nitrogen sources help retain amino groups and protein nitrogen sources help retain structural nitrogen. [ABSTRACT FROM AUTHOR]