A new nanocomposite (SCZ), microspherical carbon (SC) loaded with nanoscale zerovalent iron (ZVI), was fabricated to efficiently remove hexavalent chromium (Cr(VI)) in water. Therein, SC was derived from waste carton through hydrothermal treatment after pretreatment of removing hemicellulose and lignin, and the optimal hydrothermal conditions (200 degrees C, hydrothermal time of 12 h) for the preparation of SC were obtained. Subsequently, SC could effectively load ZVI nanoparticles which displayed high dispersion on the surface of SC and in the pores among SC particles owing to steric hindrance effect. The obtained SCZ displayed a high removal efficiency of 100% within 5 h on Cr(VI) (20 mg/L), and the resultant SCZ-Cr could be conveniently separated from water because of its magnetism. Importantly, SCZ could be loaded in cardboard, and the obtained system could serve as a stable filter for removal of Cr(VI) in water. This work provides a cheap and effective method for Cr(VI) removal, which also greatly facilitates the recycling of waste carton.