Enhanced adsorption of organic pollutants using N-doped porous carbon derived from hemp stems: Insights into the mechanism

Nitrogen (N) doping is commonly used to modify biochar and enhance its adsorption performance. However, the significance of pyrrolic-N in pollutant adsorption is frequently overlooked. In this study, N-doped porous carbon materials (NBC) have been synthesized using hemp stems as the carbon source through pyrolysis in one step for the efficient removal of organic pollutants. The incorporation of the pyrrolic-N functional group in NBC leads to an increase in surface defects, electronegativity, and electron conductivity. As a result, the Q max of tetracycline (TC) reaches 577.60 mg/g, which is twice as much as activated carbon with a similar specific surface area. The characterization and theoretical calculation demonstrate that the NBC adsorbent adsorbs TC primarily through cation-π and π-π interactions facilitated by pyrrolic-N, as well as weak electrostatic interactions induced by –COOH. In actual landfill leachate adsorption experiments, the NBC effectively reduced chemical oxygen demand and ammonia–nitrogen levels in wastewater. Additionally, the growth of sprouts planted on contaminated soil treated with NBC (sulfamethoxazole, 50 mg/kg) is restored to levels observed on uncontaminated soil, thus demonstrating its practicality.