Stabilization of sulfidated nano zerovalent iron with biochar: Enhanced transport and application for hexavalent chromium removal from water

Nano zerovalent iron (nZVI) has been broadly used in the treatment of chromium (Cr) pollution. However, conventional nZVI particles are prone to surface oxidation and particle agglomeration, limiting their effectiveness in contaminant removal. To address these issues, sulfidated nZVI (S-nZVI) was synthesized on the corn stover biochar (BC) surface for rapid removal of Cr(VI) from water. Sedimentation and column transport experiments demonstrated that S-nZVI@BC exhibits excellent dispersion and transport properties, efficiently removing Cr(VI) in the pH range of 2.5-5.0 and showing minimal impact from dissolved oxygen. The Fe0, Fe(II), and S2_ components of the material, along with the leached Fe2+ ions, contributed to the Cr(VI) removal. A portion of the removed Cr(VI) was reduced to Cr(III) in solution, while another portion was adsorbed on the material's surface through precipitation, with 42.0% of Cr being adsorbed within 30 min. Cycling and water matrix interference experiments further demonstrated the material's excellent reusability and resistance to interference. Notably, the continuous Cr(VI) removal capability in column experiments and the reactivation potential of S-nZVI@BC highlight its promise for practical applications. Future studies are suggested to explore the ecotoxicological effects of the S-nZVI@BC and its capacity for the simultaneous removal of multiple contaminants.