Chitosan-stabilized FeS magnetic composites for chromium removal: Characterization, performance, mechanism, and stability.

Chitosan-stabilized FeS magnetic (MC-FeS) composites were successfully prepared to address the easily oxidization of FeS and enhance Cr(VI) removal from water. Results showed that the MC-FeS composites enhanced the Cr(VI) removal capacity as compared to bare FeS. Further investigation using X-ray photoelectron spectroscopy showed that FeOOH, S8, Cr2O3, Cr2S3, and a Fe(III)-Cr(III) complex were apparently introduced by Cr(VI), Fe(II), and S(-II), respectively. The sorption kinetics could be interpreted using a pseudo-second-order kinetic model, whereas the isotherms were simulated using the Redlich‒Peterson isotherm model indicating Cr(VI) removal by MC-FeS composites was a hybrid chemical reaction‒sorption process. In addition, the MC-FeS composite presented high stability against aging and performed well in a long-term reaction system and typical natural water environment. The effective performance of MC-FeS composites shows their great potential in wastewater remediation contaminated by heavy metals.