Simultaneous stabilization of Pb and improvement of soil strength using nZVI

• Published in: The Science of the total environment Vol. 651; no. Pt 1; pp. 877 - 884
• Main Authors: Zhou, Wan-Huan, Liu, Fuming, Yi, Shuping, Chen, Yong-Zhan, Geng, Xueyu, Zheng, Chunmiao
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.02.2019
• Subjects: Lead, contaminated soil; nZVI; Physicochemical property; Undrained shear strength; Lead, contaminated soil; Undrained shear strength; nZVI; Physicochemical property
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.09.146

This study demonstrates the feasibility of nanoscale Zero-Valent Iron (nZVI) for simultaneous stabilization of Pb and improvement of soil strength via batch experiments. The soil samples were prepared using slurry and pre-consolidation method at nZVI doses of 0.2%, 1%, 5%, and 10% (by dry weight). The physicochemical and geotechnical properties of Pb-contaminated soil treated by nZVI were analyzed. The results indicate that the contamination of Pb(II) resulted in a notable reduction in the undrained shear strength of soil from 16.85 kPa to 7.25 kPa. As expected, the Pb in exchangeable and carbonate-bound fractions decreased significantly with the increasing doses of nZVI. Meanwhile, the undrained shear strength of Pb-contaminated soil enhanced substantially as the increase of nZVI, from 25.83 kPa (0.2% nZVI treatment) to 69.33 kPa (10% nZVI treatment). An abundance of bubbles, generated from the oxidation of nZVI, was recorded. The mechanisms for simultaneous stabilization of Pb and soil improvement primarily include: 1) the precipitation and transformation of Pb-/Fe-hydrated oxides on the soil particles and their induced bounding effects; 2) the increased drainage capability of soil as the occupation of nZVI aggregates and bubbles in the macropores space and 3) the lower soil density derived from the increase in microbubbles retained in the soil. This study is provided to facilitate the application of nZVI in the redevelopment of contaminated soil. Mechanisms for simultaneous stabilization of Pb and improvement of soil strength using NZVI includes: 1) the precipitation and transformation of Pb-/Fe-hydrated oxides on the soil particles and their induced bounding effects; 2) the increased drainage capability of soil as the occupation of NZVI aggregates (volume smelling resulted by oxidation) in the macropores space and 3) lower soil density derived by the increase of microbubbles (hydrogen generated from the redox of NZVI) retained in the soil. [Display omitted] •The feasibility of nZVI for simultaneous stabilization of Pb and soil improvement is demonstrated.•Soil improvement is primarily attributed to the precipitation and transformation of nZVI-derived hydrated oxides.•Microbubbles generated from the oxidation of nZVI also contributed to the soil improvement.•This study can facilitate the application of nZVI in redevelopment of contaminated soil.