Red mud-enhanced magnesium phosphate cement for remediation of Pb and As contaminated soil

Lei Wang; Liang Chen; Binglin Guo; Daniel C W Tsang; Longbin Huang; Yong Sik Ok; Viktor Mechtcherine

doi:10.1016/j.jhazmat.2020.123317

Red mud-enhanced magnesium phosphate cement for remediation of Pb and As contaminated soil

J Hazard Mater. 2020 Dec 5:400:123317. doi: 10.1016/j.jhazmat.2020.123317. Epub 2020 Jun 26.

Authors

Lei Wang¹, Liang Chen², Binglin Guo³, Daniel C W Tsang⁴, Longbin Huang⁵, Yong Sik Ok⁶, Viktor Mechtcherine⁷

Affiliations

¹ Institute of Construction Materials, Technische Universität Dresden, 01062, Dresden, Germany; Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
² Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
³ Department of Earth Resources Engineering, Kyushu University, Fukuoka, 819-0395, Japan.
⁴ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, QLD, 4072, Australia. Electronic address: dan.tsang@polyu.edu.hk.
⁵ Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, QLD, 4072, Australia.
⁶ Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, QLD, 4072, Australia; Korea Biochar Research Center, APRU Sustainable Waste Management & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.
⁷ Institute of Construction Materials, Technische Universität Dresden, 01062, Dresden, Germany.

PMID: 32947716
DOI: 10.1016/j.jhazmat.2020.123317

Abstract

Lead (Pb) and arsenic (As) contaminated soil poses severe threats to human health. This study proposes a novel approach for synchronous stabilisation/solidification (S/S) of Pb and As contaminated soil and explains the immobilisation mechanisms in red mud-modified magnesium phosphate cement (MPC). Experimental results show that incorporation of red mud in MPC binder retarded over-rapid reaction and enhanced compressive strength via the formation of (Al,Fe,K)PO₄·nH₂O compounds as indicated by X-ray diffractometer (XRD) and elemental mapping. The presence of Pb had a marginal effect on the MPC reaction; however, the presence of As suppressed the generation of MgKPO₄·6H₂O, leading to a significant delay of setting time and a reduction of compressive strength. Extended X-ray absorption fine structure (EXAFS) analysis proved that Pb²⁺ strongly coordinated with the PO₄^3-, whereas AsO₂- gently coordinated with K⁺. The MPC binder displayed an excellent immobilisation efficiency for Pb (99.9%), but was less effective for As. The use of red mud enhanced the As immobilisation efficacy to 80.5% due to strong complexation between AsO₂- and Fe³⁺. The treated soils fulfilled requirements of metal(loid) leachability and mechanical strength for on-site reuse. Therefore, red mud-modified MPC can be an effective binder for sustainable remediation of Pb and As contaminated soil.

Keywords: Arsenic/lead leachability; Contaminated soil remediation; Potentially toxic elements; Stabilization/solidification; Sustainable waste management; Synchrotron analysis.

Publication types

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