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

• A honeycomb-like magnetic composite named as OPCS-AS@PVA-Fe 3 O 4 was fabricated. • OPCS-AS@PVA-Fe 3 O 4 consisted of cornstalk, (NH 4) 2 SO 3 , polyvinyl alcohol and Fe 3 O 4. • OPCS-AS@PVA-Fe 3 O 4 could reduce Cr(VI) to Cr(III) and adsorb Cr(III). • OPCS-AS@PVA-Fe 3 O 4 could release ammonium to favor plant growth. • OPCS-AS@PVA-Fe 3 O 4 was stable against coexisting ions. 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)-Fe 3 O 4 to obtain PCS-AS@PVA-Fe 3 O 4. The PCS-AS@PVA-Fe 3 O 4 could reduce hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) by SO 3 2−, then the Cr(III) combined with PCS-AS@PVA-Fe 3 O 4 through hydrogen bonds. The resulting PCS-AS@PVA-Fe 3 O 4 /Cr with a high magnetism could be conveniently separated from water via a magnet. PCS-AS@PVA-Fe 3 O 4 /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-Fe 3 O 4 , 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. [ABSTRACT FROM AUTHOR]