Reduction and immobilization of hexavalent chromium in chromite ore processing residue using amorphous FeS2

Yunyi Li; Jialiang Liang; Zihao Yang; Hang Wang; Yangsheng Liu

doi:10.1016/j.scitotenv.2018.12.042

Reduction and immobilization of hexavalent chromium in chromite ore processing residue using amorphous FeS₂

Sci Total Environ. 2019 Mar 25:658:315-323. doi: 10.1016/j.scitotenv.2018.12.042. Epub 2018 Dec 5.

Authors

Yunyi Li¹, Jialiang Liang², Zihao Yang³, Hang Wang³, Yangsheng Liu⁴

Affiliations

¹ Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China; College of Environmental Sciences and Engineering, Peking University, Beijing Key Laboratory for Solid Waste Utilization and Management, Beijing 100871, PR China. Electronic address: liyunyi@cqu.edu.cn.
² Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China.
³ College of Environmental Sciences and Engineering, Peking University, Beijing Key Laboratory for Solid Waste Utilization and Management, Beijing 100871, PR China.
⁴ College of Environmental Sciences and Engineering, Peking University, Beijing Key Laboratory for Solid Waste Utilization and Management, Beijing 100871, PR China; School of Urban Planning and Design, Peking University Shenzhen Graduates School, Shenzhen 518055, PR China. Electronic address: yshliu@pku.edu.cn.

PMID: 30577025
DOI: 10.1016/j.scitotenv.2018.12.042

Abstract

In this work, a series of long-term treatment trials were conducted to evaluate the remediation performance of amorphous iron pyrite (FeS₂₍am₎) toward hexavalent chromium (Cr(VI)) in chromite ore processing residue (COPR). The effectiveness of FeS₂₍am₎ was assessed using alkaline digestion, the synthetic precipitation leaching procedure (SPLP) and the physiologically based extraction test (PBET). Reaction mechanisms were explored by monitoring the changes in the solid pH, redox potential (Eh), the chemical states of relevant elements as well as the crystal forms present in COPR. The results showed that, using a proper dosage, the total content of Cr and Cr(VI) in the leachate from treated COPR met the Chinese standard regulatory limits for the extraction toxicity of hazardous wastes (GB 5085.3-2007). In addition, the in vitro bioaccessibility of Cr(VI) in COPR was also significantly reduced. Moreover, the remediation effect was maintained for the subsequent six months. This long-term effect was attributed to the presence of reductive sulfur (S) species and Fe(II) that remained even after 180 days of treatment, which were identified using high-resolution X-ray photoelectron spectroscopy (HR-XPS) and X-ray diffraction (XRD). To maximize the effect of FeS₂₍am₎, 5% lime was employed as an additive to adjust the pH and thus contributed to Cr(VI) reduction and immobilization. To remediate COPR within 30 days, the use of 5% lime and a specific FeS₂₍am₎ dosage (FeS₂₍am₎:Cr(VI) = 1.25:1) is recommended based on the results. For rapid remediation (< 1 day), the use of 5% lime and a 2.5:1 FeS₂₍am₎:Cr(VI) ratio is recommended. In comparison with widely studied reductants, FeS₂₍am₎ showed excellent efficiency for the remediation of COPR over both short- and long-term treatment trials, demonstrating it is a very promising alternative treatment method.

Keywords: Amorphous FeS(2); Bioaccessibility; COPR; Cr(VI); Leachability.