Phase transformation of Cr(VI) host-mineral driven by citric acid-aided mechanochemical approach for advanced remediation of chromium ore processing residue-contaminated soil

Qi Li; Xiaoming Zhang; Junhao Zheng; Jingxi Qin; Chunyu Ou; Qi Liao; Mengying Si; Zhihui Yang; Weichun Yang

doi:10.1016/j.jhazmat.2023.132530

Phase transformation of Cr(VI) host-mineral driven by citric acid-aided mechanochemical approach for advanced remediation of chromium ore processing residue-contaminated soil

J Hazard Mater. 2024 Jan 5:461:132530. doi: 10.1016/j.jhazmat.2023.132530. Epub 2023 Sep 12.

Authors

Qi Li¹, Xiaoming Zhang¹, Junhao Zheng¹, Jingxi Qin¹, Chunyu Ou¹, Qi Liao², Mengying Si², Zhihui Yang², Weichun Yang³

Affiliations

¹ School of Metallurgy and Environment, Central South University, Changsha 410083, PR China.
² School of Metallurgy and Environment, Central South University, Changsha 410083, PR China; Chinese National Engineering Research Centre for Control & Treatment of Heavy Metal Pollution, Changsha 410083, PR China.
³ School of Metallurgy and Environment, Central South University, Changsha 410083, PR China; Chinese National Engineering Research Centre for Control & Treatment of Heavy Metal Pollution, Changsha 410083, PR China. Electronic address: yang220@csu.edu.cn.

PMID: 37716262
DOI: 10.1016/j.jhazmat.2023.132530

Abstract

The slow release of Cr(VI) from chromium ore processing residue-contaminated soil (COPR-soil) poses a significant environmental and health risk, yet advanced remediation techniques are still insufficient. Here, the slow-release behavior of Cr(VI) in COPR-soil is observed and attributed to the embedded Cr(VI) in the lattice of vaterite due to the isomeric substitution of CrO₄^2- for CO₃^2-. A citric acid-aided mechanochemical approach with FeS₂/ZVI as reductive material was developed and found to be highly effective in remediating COPR-soil. Almost all Cr(VI) in COPR-soil, including Cr(VI) embedded in the minerals, are reduced with a reduction efficiency of 99.94%. Cr(VI) reduction kinetics indicate that the Cr(VI) reduction rate constant in the presence of citric acid was 4.8 times higher compared to its absence. According to the Raman spectroscopy, X-ray diffraction (XRD), and Electron Probe X-ray Micro-Analyzer (EPMA) analysis, the reduction of Cr(VI) embedded in vaterite was mainly attributed to the citric acid-induced protonation effect. That is, under the protonation effect, the embedded Cr(VI) could be released from vaterite through its phase transformation to calcite, whose affinity to Cr(VI) is low. While the reduction of released Cr(VI) could be promoted due to the complexation of citric acid with disulfide groups on FeS₂/ZVI. The results of long-term stability tests demonstrated that the remediated COPR-soil exhibited excellent long-term stability, which may also be associated with improved utilization of available carbon and electron donors by the Cr(VI) reducing bacteria (Proteobacteria)-dominated microbial community in the presence of citric acid, thereby promoting to establish a stable reducing microenvironment. Collectively, these findings will further our understanding of the reduction remediation of COPR-soil, especially in the case of Cr(VI) embedded in minerals.

Keywords: Embedded Cr(VI); Long-term stability; Phase transformation; Protonation effect; Vaterite.