Mechanism of reduction and immobilization of Cr(VI) by application modified nano-zerovalent iron

ABSTRACT

Hexavalent chromium [Cr(VI)] is a highly toxic agent that seriously threatens the environment and human health. In-situ reduction and immobilization are potential strategies to treat Cr(VI)-contaminated soil. In this study, sodium alginate (SA) and carboxymethylcellulose (CMC) were used to modify nano-zero-valent iron (NZVI) to prepare SA-NZVI and CMC-NZVI to study its effect on the reduction efficiency of Cr(VI) in the soil. Scanning electron microscope (SEM) images found that compared with the agglomeration of NZVI and CMC-NZVI, SA-NZVI particles have a significant improvement, better dispersion, chain-like distribution, and a particle size of 50–100 nm. And the X-ray diffraction (XRD) pattern further showed that SA-NZVI has only Fe⁰ peaks and no Fe₃O₄ peaks, which further proved that it is pure nano-zero-valent iron. The batch tests showed that SA-NZVI could quickly and effectively reduce the Cr(VI) in the soil, and SA-NZVI could reduce the Cr(VI) by 96.68%. For Cr(VI)-contaminated soil, the Cr(VI) reduction rate of SA-NZVI was higher than NZVI and CMC-NZVI. After 28 d remediation, the fractions of Cr forms in soil, such as exchangeable (EX), carbonate-bound (CB), Fe-Mn oxides-bound (OX), and organic matter-bound (OM), were mainly transformed to residual fraction (RS) species because of the production of ferrochrome precipitates. X-ray photoelectron spectroscopy (XPS) showed that after SA-NZVI treatment, Cr(VI) was reduced to trivalent chromium [Cr(III)] and the formation of Cr(OH)₃ precipitation. The research results provide a theoretical basis for applying SA-NZVI in Cr(VI) contaminated soil remediation.

KEYWORDS:

• Nano zero-valent iron
• soil restoration
• reduction rate
• hexavalent chromium
• sodium alginate
• mechanisms

Acknowledgments

This study was supported by Natural Science Foundation of Guangxi, China (2020GXNSFAA297035).

Availability of Data and Materials

All data generated or analyzed during this study are included in this published article [and its supplementary information files].

Authors’ contributions

H.M.Mo designed the study; X.Z.Qin and H.M.Mo performed the experiments; and X.Z.Qin analyzed the data and wrote the manuscript. C.L.Zhang improved conceptualization, project management, acquisition funds, and supervision. Q.Rong, H.C.Zhao, and X.T.Liu supervised, improved investigation, and methodology

Consent to Participate

I consent to and permit the researchers and their project partners to use the content of this article in publications, news articles and websites for non-profit purposes.

Consent to Publish

The participant has consented to the submission of the case report to the journal.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Guangxi Natural Science Foundation Project [2020GXNSFEA297035].