Green remediation of As and Pb contaminated soil using cement-free clay-based stabilization/solidification

Lei Wang, Dong Wan Cho, Daniel C.W. Tsang, Xinde Cao, Deyi Hou, Zhengtao Shen, Daniel S. Alessi, Yong Sik Ok, Chi Sun Poon

Research output: Contribution to journalArticle

28 Citations (Scopus)

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 27 Al 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 (AsO 4 ) 2 ·4H 2 O and Pb 3 (NO 3 )(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.

Original languageEnglish
Pages (from-to)336-345
Number of pages10
JournalEnvironment International
Volume126
DOIs
Publication statusPublished - 2019 May 1

Fingerprint

solidification
stabilization
cement
remediation
Soil
clay
Alkalies
Immobilization
Minerals
hydration
immobilization
lime
clay mineral
Kaolin
Photoelectron Spectroscopy
Calcium Carbonate
Poisons
environmental constraint
contaminated soil
X-Ray Diffraction

Keywords

  • Alkali-activated materials
  • Arsenic/lead leachability
  • Calcined clay
  • Green/sustainable remediation
  • Low-carbon contaminant immobilization
  • Waste valorization/recycling

ASJC Scopus subject areas

  • Environmental Science(all)

Cite this

Green remediation of As and Pb contaminated soil using cement-free clay-based stabilization/solidification. / Wang, Lei; Cho, Dong Wan; Tsang, Daniel C.W.; Cao, Xinde; Hou, Deyi; Shen, Zhengtao; Alessi, Daniel S.; Ok, Yong Sik; Poon, Chi Sun.

In: Environment International, Vol. 126, 01.05.2019, p. 336-345.

Research output: Contribution to journalArticle

Wang, Lei ; Cho, Dong Wan ; Tsang, Daniel C.W. ; Cao, Xinde ; Hou, Deyi ; Shen, Zhengtao ; Alessi, Daniel S. ; Ok, Yong Sik ; Poon, Chi Sun. / Green remediation of As and Pb contaminated soil using cement-free clay-based stabilization/solidification. In: Environment International. 2019 ; Vol. 126. pp. 336-345.
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AU - Hou, Deyi

AU - Shen, Zhengtao

AU - Alessi, Daniel S.

AU - Ok, Yong Sik

AU - Poon, Chi Sun

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