Nano iron oxide impregnated in chitosan bead as a highly efficient sorbent for Cr(VI) removal from water

Abstract Using Fe(III) salts and chitosan, nano iron oxide impregnated in chitosan bead (NIOC) was successfully synthesized for aqueous Cr(VI) detoxification via sol-gel technique without any additional crosslinking agent. NIOC characterization demonstrated that the iron in NIOC mainly existed as nano akaganeite (β-FeOOH) and complex with chitosan. Intraparticle diffusion was the major rate-limiting step. The maximal adsorption capacity was 69.8 mg/g (pH 5.0, 20 °C). Normal concentration of coexisting anions (SO 4 2− , CO 3 2− , SiO 3 2 −) showed insignificant competition, whereas PO 4 3− suppressed the Cr(VI) sorption. Cr(VI)-loaded NIOC could be effectively regenerated by alkaline solutions. Column adsorption runs using granular NIOC could effectively treat about 1600 bed volumes of Cr(VI) solution (from 3.7 mg Cr/L in influent to