Zero valent iron or Fe3O4-loaded biochar for remediation of Pb contaminated sandy soil: Sequential extraction, magnetic separation, XAFS and ryegrass growth. (1st September 2022)

• Record Type: Journal Article
• Authors: Duan, Lunchao; Wang, Qianhui; Li, Jining; Wang, Fenghe; Yang, Hao; Guo, Binglin; Hashimoto, Yohey
• Is Part Of: Environmental pollution. Volume 308(2022)
• Publication Date: 2022-09-01
• Subjects: Pb soil -- Fe-based amendment -- Immobilization -- Phytoavailability -- XAFS; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.119702
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: In this study, the feasibility of using zero-valent iron (ZVI) and Fe3 O4 -loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L. ) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH −, PO4 3−, and SO4 2− ) released from magnetic biochar. ZVI increased ryegrass production while Fe3 O4 -loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application. Graphical abstract: Image 1 Highlights: Both ZVI and biochar decreased available Pb in soil and reduced Pb uptake by ryegrass. EXAFS demonstrated the major contribution of ferrihydrite and/or birnessite for Pb immobilization. Dry magnetic separation presents opportunity for the permanent removal of Pb from soils.