A novel PEI-grafted N-doping magnetic hydrochar for enhanced scavenging of BPA and Cr(VI) from aqueous phase.

Herein, polyethyleneimine (PEI)-grafted nitrogen-doping magnetic hydrochar (PEI@MNHC) was synthesized for hexavalent chromium (Cr(VI)) and bisphenol A (BPA) elimination from water. Characterizations exhibited that abundant amino functional groups, intramolecular heterocyclic N, azo and Fe-N structures were successfully introduced into the inherent structure of hydrochar. The obtained PEI@MNHC presented maximum uptake of 205.37 and 180.79 mg/g for Cr(VI) and BPA, respectively, and was highly tolerant to various co-existing ions. Mechanism investigation revealed that the protonated amino, intramolecular heterocyclic N and Fe(II) participated in Cr(VI) reduction, and the N/O-containing groups and Fe(III) fixed Cr(III) onto PEI@MNHC by the formation of complexes and precipitates. On the other hand, azo, Fe-N and graphitic N structures contributed to the removal of BPA via pore filling, hydrogen bonding and π-π interactions. Additionally, PEI@MNHC maintained over 85.0% removal efficiency for Cr(VI) and BPA after four cycles, manifesting that PEI@MNHC was an ideal adsorbent with outstanding practical application potential.