Nitrogen-doped porous hydrochar for enhanced chromium(VI) and bisphenol A scavenging: Synergistic effect of chemical activation and hydrothermal doping

Abstract

Nitrogen-doped porous hydrochar (NPHC) was successfully synthesized by hydrothermal carbonization and activation with KHCO₃, which was employed for scavenging hexavalent chromium (Cr(VI)) and bisphenol A (BPA) in contaminated water. N doping increased the unique active sites such as amino and molecular N in NPHC for adsorbing contaminants, and enhanced the activation effect. Compared to original (HC) and N-doped hydrochar (NHC), the S_BET of material improved from 3.99 m²/g and 4.71 m²/g to 1176.77 m²/g. Meanwhile, NPHC exhibited more superior adsorption capacity for Cr(VI) (323.25 mg/g) and BPA (545.34 mg/g) than that of porous hydrochar (213.17 and 343.67 mg/g). Moreover, NPHC possessed pH-dependence and presented more excellent tolerance for interfering ions and regeneration performance. Notably, the Cr(VI) capture by NPHC was dominated via pore filling, electrostatic interaction, reduction, and complexation, while π-π stacking, H-bond interaction, and hydrophobic action were relevant to the binding mechanism of BPA. Overall, the proposed functionalization strategy for biochar was conducive to enhance the remediation of water bodies.