Removal of heavy metals from contaminated paddy soils using chemical reductants coupled with dissolved organic carbon solutions

Shui-Wen Chang Chien; Hsiou-Hsuan Wang; Yueh-Min Chen; Ming-Kuang Wang; Cheng-Chung Liu

doi:10.1016/j.jhazmat.2020.123549

Removal of heavy metals from contaminated paddy soils using chemical reductants coupled with dissolved organic carbon solutions

J Hazard Mater. 2021 Feb 5:403:123549. doi: 10.1016/j.jhazmat.2020.123549. Epub 2020 Aug 6.

Authors

Shui-Wen Chang Chien¹, Hsiou-Hsuan Wang², Yueh-Min Chen³, Ming-Kuang Wang⁴, Cheng-Chung Liu⁵

Affiliations

¹ Department of Environmental Engineering and Management, Chaoyang University of Technology, Taichung, 41349, Taiwan. Electronic address: swcc@cyut.edu.tw.
² Department of Chemical and Materials Engineering, National Ilan University, Ilan, 26047, Taiwan. Electronic address: sswang@niu.edu.tw.
³ College of Geographical Science, Fujian Normal University, Fuzhou, 350007, China. Electronic address: ymchen@finu.edu.cn.
⁴ Department of Agricultural Chemistry, National Taiwan University, Taipei, 10617, Taiwan. Electronic address: mkwang@ntu.edu.tw.
⁵ Department of Environmental Engineering, National Ilan University, Ilan, 26047, Taiwan. Electronic address: ccliu@niu.edu.tw.

PMID: 32827858
DOI: 10.1016/j.jhazmat.2020.123549

Abstract

General acid washing is commonly used to treat heavy metal-contaminated soils, but it is sometimes difficult to achieve remediation aims in severely polluted soils. If we expose the surfaces of Fe oxide minerals to reductive dissolution during washing treatment, more of the metals initially adsorbed to these surfaces will be liberated, which may encourage the removal of heavy metals. Initially, the metal extraction capabilities of nine chemical reductants were compared in ten soil samples polluted by Cr, Cu, Zn, and Ni. Sodium dithionite (Na₂S₂O₄) and ferrous sulfate (FeSO₄) were screened for subsequent intensive research. In summary, the Na₂S₂O₄ solutions had higher Cr, Cu, and Zn removal rates than either the FeSO₄ or acid solution. Application of dissolved organic carbon (DOC) further increased the removal of heavy metals by complexation. About 15%, 86%, 32%, and 52% of the Cr, Cu, Zn, and Ni, respectively, were removed from the representative soil (M-2) by two-stage washing using 0.2 M Na₂S₂O₄ coupled with 1,500 mg L^-1 DOC solution at pH 2.0. Meanwhile, most soil fertility was preserved: ammonium nitrogen was increased 3.9 times; the increase in exchangeable potassium was 33%; and the reduction in available P was only 10%.

Keywords: DOC; Fe oxide minerals; Ferrous sulfate; Reductive dissolution; Sodium dithionite; Soil washing.

Publication types

Research Support, Non-U.S. Gov't