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Title: Green remediation of As and Pb contaminated soil using cement-free clay-based stabilization/solidification
Authors: Wang, L 
Cho, DW 
Tsang, DCW 
Cao, XD
Hou, DY
Shen, ZT
Alessi, DS
Ok, YS
Poon, CS 
Keywords: Green/sustainable remediation
Low-carbon contaminant immobilization
Calcined clay
Alkali-activated materials
Waste valorization/recycling
Arsenic/lead leachability
Issue Date: 2019
Publisher: Pergamon Press
Source: Environment international, May 2019, v. 126, p. 336-345 How to cite?
Journal: Environment international 
Abstract: Stabilization/solidification (S/S) is a low-cost and high-efficiency remediation method for contaminated soils, however, conventional cement-based S/S method has environmental constraints and sustainability concerns. This study proposes a low-carbon, cement-free, clay-based approach for simultaneous S/S of As and Pb in the contaminated soil, and accordingly elucidates the chemical interactions between alkali-activated clay binders and potentially toxic elements. Quantitative X-ray diffraction and Al-27 nuclear magnetic resonance analyses indicated that the addition of lime effectively activated the hydration of kaolinite clay, and the presence of limestone further enhanced the polymerization of hydrates. X-ray photoelectron spectroscopy showed that approximately 19% of As-[III] was oxidized to As-[V] in the alkali-activated clay system, which reduced toxicity and facilitated immobilization of As. During the cement-free S/S process, As and Pb consumed Ca(OH)(2) and precipitated as Ca-3(AsO4)(2)center dot 4H(2)O and Pb-3(NO3)(OH)(5), respectively, accounting for the low leachability of As (7.0%) and Pb (5.4%). However, the reduced amount of Ca(OH)(2) decreased the degree of hydration of clay minerals, and the pH buffering capacity of the contaminated soil hindered the pH increase. Sufficient dosage of lime was required for ensuring satisfactory solidification and contaminant immobilization of the clay-based S/S products. The leachability of As and Pb in high-Ca S/S treated soil samples was reduced by 96.2% and 98.8%, respectively. This is the first study developing a green and cement-free S/S of As- and Pb-contaminated soil using clay minerals as an environmentally compatible binding material.
ISSN: 0160-4120
DOI: 10.1016/j.envint.2019.02.057
Rights: © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (
The following publication Wang, L., Cho, D. W., Tsang, D. C., Cao, X., Hou, D., Shen, Z., ... & Poon, C. S. (2019). Green remediation of As and Pb contaminated soil using cement-free clay-based stabilization/solidification. Environment international, 126, 336-345 is available at
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