Preparation of highly dispersive and antioxidative nano zero-valent iron for the removal of hexavalent chromium

In this study, carboxymethyl cellulose (CMC) was employed to stabilize zero-valent iron nanoparticles (CMC-nFe(0)) to improve their dispersity and antioxidation for enhanced hexavalent chromium (Cr(VI)) removal. Scanning electron microscope (SEM) observation revealed that the nFe(0) agglomerated in clusters, while the CMC-nFe(0) connected as chains and presented higher dispersity. Therefore, compared with 54% of the nFe(0), the Cr(VI) removal rate of the CMC-nFe(0) increased by 0.8 time, reaching 97%. Besides, the nFe(0) precipitated in 1 d and was obviously oxidized within 7 d under anoxic condition, leading to a rapid decease of Cr(VI) removal efficiency from 54% to 3% in 56 d. In contrast, the CMC-nFe(0) showed no obvious subsidence and oxidized phenomenon within 14 d, which retained a relatively high Cr(VI) removal efficiency of 63% in 56 d, contributing to effective blockage of dissolved oxygen infiltrating from solution to nFe(0) particles in presence of CMC. After reaction, the valence state distribution of Cr between solution and material surface indicated that Cr(VI) reduction was dominant comparing to physical adsorption to particles in the remediation process conducted by CMC-nFe(0) . In addition, lower initial pH and higher iron dosage facilitated Cr(VI) removal. Those results indicated that the dispersive and antioxidative characteristics of CMC-nFe(0) were significantly superior to those of nFe(0), and CMC stabilization thereafter can be a promising method to promote Cr(VI) elimination by nFe(0). (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Using carboxymethyl cellulose (CMC) to stabilize zero-valent iron nanoparticles (CMC-nFe(0)) was found to enhance hexavalent chromium (Cr(VI)) removal efficiency by improving dispersion and antioxidation, preventing agglomeration and oxidation of particles, and effectively blocking oxygen infiltration, showcasing superior performance compared to untreated iron nanoparticles. Lower initial pH and higher iron dosage were found to further facilitate Cr(VI) removal. These findings suggest that CMC stabilization of iron nanoparticles holds promise for enhancing Cr(VI) elimination processes.