Multifunctional schwertmannite-loaded nano zero-valent iron for highly efficient removal of hexavalent chrome from aqueous solution

Adsorption and reduction are important ways to remediate hexavalent chrome [Cr(VI)] which is extremely hazardous to human health. Previous studies have shown that schwertmannite (Sch) and nano zero-valent iron (nZVI) are potential materials with high adsorption and strong reduction for Cr(VI), respectively. However, it has been well known that bare nZVI has limitations in remediating Cr(VI) due to its susceptibility to self-aggregation and oxidation in practical applications. Hence to address the above limitations, nZVI was added into the internal pore structure of Sch (nZVI@Sch) in this study and Cr(VI) removal capacity by nZVI@Sch in aqueous solution were systematically investigated. Results showed that under the conditions that the concentration ratio of Fe2+ and Sch is 0.25 mol/L, Cr(VI) initial concentration of 10 mmol/L, initial pH of 3, Cr(VI) remediation ability of nZVI@Sch reached up to 114.03 mg/g (with freeze-drying) and 165.69 mg/g (without freeze-drying) in 4 hours, respectively. Based on the characterization analysis of SEM-EDS, XPS and Zeta potential, the multifunctional synergistic effects of capture-reduction-adsorption-coprecipitation as a mechanism for the removal of Cr(VI) by nZVI@Sch were proposed in this study. This study provided a new remediation material and suggestions for chromium pollution remediation.