Mechanism of reduction and immobilization of Cr(VI) by application modified nano-zerovalent iron. Issue 8 (17th November 2022)

• Record Type: Journal Article
• Authors: Qin, Xingzi; Mo, Huimin; Rong, Qun; Zhao, Hecheng; Liu, Xutong; Zhang, Chaolan
• Is Part Of: Soil & sediment contamination. Volume 31:Issue 8(2022)
• Page Start: 1011
• Page End: 1025
• Publication Date: 2022-11-17
• Subjects: Nano zero-valent iron -- soil restoration -- reduction rate -- hexavalent chromium -- sodium alginate -- mechanisms; Soil pollution -- Periodicals; Soil protection -- Periodicals; 628.5505
• DOI: 10.1080/15320383.2022.2034736
• Languages: English
• ISSNs: 1532-0383

Abstract

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 Fe 0 peaks and no Fe3 O4 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.