Remediation of Cr(VI)-contaminated soil by ball milling modified zero-valent iron biochar composites: Insights into long-term stability and microbial community

• Published in: Journal of environmental chemical engineering 2023-12, Vol.11 (6), p.111279, Article 111279
• Main Authors: Guo, Pengfei, Zhang, Jinlan, Zhou, Yi, Tang, Chenliu, Wang, Xiaohui, Gao, Xiaoping, Duan, Guilan, Lin, Aijun, Zhang, Tingting, Li, Shangyi
• Format: Article
• Language: English
• Subjects: Anti-adverse environment; Bacterial community; Ball milling; Cr(VI)-contaminated soil; Zero-valent iron biochar composites
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2023.111279

Hexavalent chromium (Cr(VI)) in soil has received extensive attention because of its harmful effects on the environment. In this study, ball-milled zero-valent iron biochar composites (BM-ZVI/BC) were prepared and used for the remediation of artificial Cr(VI)-contaminated soil. The Cr(VI) in the soil could be reduced from 170.4 mg kg−1 to less than 3.0 mg kg−1 after 5 days and remained stable in the next 105 days. The immobilization efficiency for Cr(VI) and Cr was close to 100%. In addition, the bioavailability of Cr(VI) and Cr was reduced to 27.9% and 4.6%, respectively. BM-ZVI/BC not only played a role in the transformation of Cr into a more stable chemical form to reduce its toxicity and mobility in the soil, but also affected the soil physicochemical properties. Compared to zero-valent iron biochar composites (ZVI/BC), BM-ZVI/BC had a positive effect on recovering microbial diversity and richness, along with the enhanced growth of low-abundance phyla. The relative abundance of Arthrobacter, Bacillus and Exiguobacterium related to Cr-reduction was also increased in the BM-ZVI/BC remediated soil. BM-ZVI/BC has shown excellent resistance and stability under extreme environmental conditions of acid rain leaching, dry-wet and freeze-thaw cycles. This study demonstrates the potential of ball milling modification in preparing zero-valent iron biochar composites for the remediation of Cr(VI)-contaminated soil. [Display omitted] •BM-ZVI/BC reduced Cr(VI) in the soil to less than 3.0 mg kg−1 within 5 days.•BM-ZVI/BC reduced the mobility and bioavailability of Cr.•BM-ZVI/BC reshaped the community structure of microorganisms in the soil.•BM-ZVI/BC maintained Cr below 50 μg L−1 in long-term acid rain leaching.•BM-ZVI/BC could resist extreme conditions of dry-wet and freeze-thaw cycles.