Designing novel magnesium oxysulfate cement for stabilization/solidification of municipal solid waste incineration fly ash

Lei Wang; Yuying Zhang; Liang Chen; Binglin Guo; Yongshan Tan; Keiko Sasaki; Daniel C W Tsang

doi:10.1016/j.jhazmat.2021.127025

Designing novel magnesium oxysulfate cement for stabilization/solidification of municipal solid waste incineration fly ash

J Hazard Mater. 2022 Feb 5;423(Pt A):127025. doi: 10.1016/j.jhazmat.2021.127025. Epub 2021 Aug 25.

Authors

Lei Wang¹, Yuying Zhang², Liang Chen², Binglin Guo³, Yongshan Tan⁴, Keiko Sasaki⁵, Daniel C W Tsang²

Affiliations

¹ Institute of Construction Materials, Technische Universität Dresden, 01062 Dresden, Germany.
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; Kyushu University Institute for Asian and Oceanian Studies, Kyushu University, Fukuoka 819-0395, Japan. Electronic address: guo@mine.kyushu-u.ac.jp.
⁴ College of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, China.
⁵ Department of Earth Resources Engineering, Kyushu University, Fukuoka 819-0395, Japan; Kyushu University Institute for Asian and Oceanian Studies, Kyushu University, Fukuoka 819-0395, Japan. Electronic address: keikos@mine.kyushu-u.ac.jp.

PMID: 34481391
DOI: 10.1016/j.jhazmat.2021.127025

Abstract

Municipal solid waste incineration (MSWI) fly ash is a typical hazardous waste worldwide. In this study, an innovative magnesium oxysulfate cement (MOSC) binder was designed for stabilization/solidification (S/S) of MSWI fly ash, focusing on the interactions between MOSC binder and typical metallic cations (Pb²⁺)/oxyanions (AsO₃^3-). Experimental results showed that Pb and As slightly inhibited the reaction of high-sulfate 5MS system but significantly suppressed the reaction process of low-sulfate 10MS system. The 5MS binder system exhibited excellent immobilization efficiencies (99.8%) for both Pb and As. The extended X-ray absorption fine structure spectra suggested that Pb²⁺ coordinated with SO₄^2-/OH^- in the MOSC system and substituted Mg²⁺ ion sites in the internal structure of 5Mg(OH)₂·MgSO₄.7H₂O (5-1-7) phase. In contrast, the AsO₃^3- substituted SO₄^2- sites with the formation of inner-sphere complexes with Mg²⁺ in the large interlayer space of the 5-1-7 structure. Subsequent MSWI fly ash S/S experiments showed that a small amount of reactive Si in MSWI fly ash interfered with the MOSC reaction and adversely influenced the immobilization efficiencies of Pb, As, and other elements. Through the use of 33 wt% tailored MOSC binder for MSWI fly ash treatment, a satisfying S/S performance could be achieved.

Keywords: Green and sustainable remediation; Hazardous waste management; Low-carbon cement; MSWI fly ash; Potentially toxic elements.