Efficient removal of hexavalent chromium by a novel magnetic zirconium-iron composite oxide (MZIO) from aqueous solution: Kinetic, isotherm, and mechanism

Abstract

In this study, the magnetic zirconium-iron composite oxide (MZIO) was prepared through coprecipitation method, and its adsorption performance on Cr(VI) was investigated. The MZIO was characterized by XRD, XPS, SEM, BET, and VSM. The effects of adsorption reaction conditions on Cr(VI) removal were systematically studied, including initial pH, MZIO dosage, initial Cr(VI) concentration, temperature, and coexisting anions. The addition of zirconium not only enhanced the specific surface area and γ-Fe2O3 exposure but also supplied additional active sites, which boosted the adsorption action dramatically. Interestingly, characterization analysis revealed that MZIO played a key role in Cr(VI) reduction, which may be connected to the conversion of certain Fe3+ to Fe2+ after zirconium addition. MZIO could accommodate a wider pH range and complicated anionic conditions in water. The Cr(VI) adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, with the maximum adsorption capacity of 49.43 mg/g. Thermodynamic parameters reflected a spontaneous and endothermic adsorption process. After five regeneration cycles, MZIO still showed strong removal stability and magnetic recovery ability. These results suggested that MZIO is a promising magnetic adsorbent for removing Cr(VI) from water, with high adsorption capacity and easy recovery and regeneration.