Green remediation of Cd and Hg contaminated soil using humic acid modified montmorillonite: immobilization performance under accelerated ageing conditions

Wang, L., Li, X., Tsang, D. C.W., Jin, F. and Hou, D. (2020) Green remediation of Cd and Hg contaminated soil using humic acid modified montmorillonite: immobilization performance under accelerated ageing conditions. Journal of Hazardous Materials, 387, 122005. (doi: 10.1016/j.jhazmat.2019.122005)

Abstract

Solidification/Stabilization (S/S) is an effective way to immobilize toxic metals in contaminated soil. However, utilization of ordinary Portland cement (PC) in this process has raised environmental concerns owing to the high carbon footprint from PC manufacturing and the risk of toxic element leaching in the long term. Hence there is an urgent need to seek for “green” immobilization approaches with long-term stability. In this study, a clay-based material, humic acid modified montmorillonite (HA-Mont) was applied to a Cd and Hg contaminated soil. Field emission scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (FESEM/EDS), N2 adsorption-desorption, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses were performed to investigate the characteristics of this material. Compared to the soil without any treatment, dosage of 5% HA-Mont could effectively reduce Cd and Hg concentrations by 94.1% and 93.0%, respectively and to below the regulatory limits in the TCLP (Toxicity Characteristic Leaching Procedure) leachates. Compared to the soil treated with virgin montmorillonite, HA modification resulted in the reduction of leachate concentrations of Cd and Hg by 69.5% and 65.9%, respectively. Long-term immobilization performance of the HA-Mont treatment was examined using a quantitative accelerated ageing method. In order to examine the ageing features, a novel method based on conditional probability was developed, and the reliability of HA-Mont immobilization was found to fit the Weibull model well, as the ageing rate of immobilization effect increased with time. After 120 years of ageing, reliability of both metals could still remain above 0.95. Cd concentration in TCLP leachates at 120th year could still remain below the regulatory limit (294 μg/L vs 1000 μg/L), while Hg concentration reached the regulatory limit of 200 μg/L in 96th year. This is the first attempt developing a green S/S method of Cd and Hg contaminated soil using HA-Mont and examining the long-term ageing characteristics of the stabilized soil using a probability-based approach.

• Item Type: Articles
• Additional Information: This work was supported by the National Key Research and Development Program of China (Grant No. 2018YFC1801300).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Jin, Dr Fei

Creator Roles

Jin, F.: Writing – review and editing

• Authors: Wang, L., Li, X., Tsang, D. C.W., Jin, F., and Hou, D.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment
• Journal Name: Journal of Hazardous Materials
• Publisher: Elsevier
• ISSN: 0304-3894
• ISSN (Online): 1873-3336
• Published Online: 02 January 2020
• Copyright Holders: Copyright © 2020 Elsevier B.V.
• First Published: First published in Journal of Hazardous Materials 387: 122005
• Publisher Policy: Reproduced in accordance with the publisher copyright policy