Chitosan-modified magnetic carbon nanomaterials with high efficiency, controlled motility, and reusability—for removal of chromium ions from real wastewater

Hexavalent chromium Cr(VI) is one of the most hazardous oxygen-containing anions to human health and the environment. Adsorption is considered to be an effective method for the removal of Cr(VI) from aqueous solutions. Based on an environmental perspective, we used renewable biomass cellulose as carbon source and chitosan as functional material to synthesize chitosan-coated magnetic carbon (MC@CS) material. The synthesized chitosan magnetic carbons were uniform in diameter (~ 20 nm) and contain a large number of abundant hydroxyl and amino functional groups on the surface, meanwhile owning excellent magnetic separation properties. The MC@CS exhibited high adsorption capacity (83.40 mg/g) at pH 3 and excellent cycling regeneration ability when applied to Cr(VI) removal in water, removal rate of Cr(VI) (10 mg/L) was still over 70% after 10 cycles. FT-IR and XPS spectra showed that electrostatic interaction and reduction with Cr(VI) are the main mechanisms of Cr(VI) removal by MC@CS nanomaterial. This work provides an environment-friendly adsorption material that could be reused for the removal of Cr(VI) in multiple cycles. Graphical Abstract