Nitrogen-doped activated carbon derived from biomass waste for effective removal of doxycycline from aqueous solution: characterization and adsorption mechanism

The nitrogen-doped activated carbon (NAC) with high specific area (3140.76 m²·g^− 1) derived from pomelo peel was prepared using hydrothermal carbonization, nitrogen doping and KOH activation method for the effective removal of Doxycycline (DOX) from aqueous solution. NAC showed exceptional adsorption efficacy for DOX than non-doped activated carbon (AC), which was attributed to the rich N-containing functional groups on the NAC surface and well-developed pore structure. The adsorption equilibrium data of DOX on NAC was fitted well to the Sips isotherm model and the adsorption process was spontaneous, endothermic and randomness-increasing. The Elovich kinetic model could better describe the adsorption process of DOX. The adsorption mechanisms of DOX onto NAC could be attributed to the hydrogen bonding, π-π electron donor-acceptor (EDA) interaction, hydrophobic effect and electrostatic interaction. Besides, the N-doping enhanced the adsorption performance of NAC. The maximum saturated adsorption capacity of NAC was 1559.35 mg·g^− 1 at 298 K, indicating that the NAC could be a promising adsorbent for removing Doxycycline from wastewater.