Honeycomb-like magnetic cornstalk for Cr(VI) removal and ammonium release

In this work, cornstalk (CS) was irradiated by high energy electron beam to obtain honeycomb-like porous CS (PCS). The PCS was loaded with ammonium sulfite (AS) and then coated by polyvinyl alcohol (PVA)-Fe3O4 to obtain PCS-AS@ PVA-Fe3O4. The PCS-AS@ PVA-Fe3O4 could reduce hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) by SO32-, then the Cr(III) combined with PCS-AS@ PVA-Fe3O4 through hydrogen bonds. The resulting PCS-AS@ PVA-Fe3O4/Cr with a high magnetism could be conveniently separated from water via a magnet. PCS-AS@ PVA-Fe3O4/Cr showed a high performance on controlling Cr(VI) migration in soil and uptake by plant. Meanwhile, ammonium could be released from PCS-AS@ PVA-Fe3O4, favoring plant growth. Therefore, this work not only provides a promising and low-cost approach to remove Cr(VI) and promote plant growth simultaneously, but also provides a new route for CS recycling, which might have a potential application value.