Unraveling the intrinsic mechanism behind the retention of arsenic in the co-gasification of coal and sewage sludge: Focus on the role of Ca and Fe compounds

Yujia Du; Tingrui Shi; Shugang Guo; Hugang Li; Yuhong Qin; Yuefeng Wang; Chong He; Yuexing Wei

doi:10.1016/j.jhazmat.2024.134211

Unraveling the intrinsic mechanism behind the retention of arsenic in the co-gasification of coal and sewage sludge: Focus on the role of Ca and Fe compounds

J Hazard Mater. 2024 May 15:470:134211. doi: 10.1016/j.jhazmat.2024.134211. Epub 2024 Apr 6.

Authors

Yujia Du¹, Tingrui Shi¹, Shugang Guo², Hugang Li³, Yuhong Qin⁴, Yuefeng Wang¹, Chong He¹, Yuexing Wei¹

Affiliations

¹ College of Environmental Science and Engineering, Taiyuan University of Technology, No. 79 Yingze West Street, Taiyuan 030024, PR China.
² Shanxi Provincial Center for Disease Control and Prevention, 8 Xiaonanguan Street, Taiyuan 030012, PR China.
³ College of Environmental Science and Engineering, Taiyuan University of Technology, No. 79 Yingze West Street, Taiyuan 030024, PR China; Laboratory of Ecology-based Solutions, College of Ecology, Taiyuan University of Technology, No. 79 Yingze West Street, Taiyuan 030024, PR China.
⁴ College of Environmental Science and Engineering, Taiyuan University of Technology, No. 79 Yingze West Street, Taiyuan 030024, PR China. Electronic address: qinyuhong@tyut.edu.cn.

PMID: 38598878
DOI: 10.1016/j.jhazmat.2024.134211

Abstract

Minimizing the emission of arsenic (As) is one of the urgent problems during co-gasification of Shenmu coal (SM) and sewage sludge (SS). The intrinsic mechanism of As retention was obtained by analyzing the effect of different SM addition ratios on the As form transformation during co-gasification at 1000 °C under CO₂ atmosphere. The results showed that the addition of SM effectively promoted the enrichment of As in the co-gasified residues. Especially, the best As retention rate of 65.71% was achieved with the 70 wt% addition ratio of SM. The addition of SM promoted the adsorption and chemical oxidation of As(III) to the less toxic As(V) through the coupling of Ca and Fe compounds in the co-gasified residues. XRD and XPS results indicated that Fe₂O₃ adsorbed As₂O₃(g) after partial conversion to Fe₃O₄ by the Boudouard reaction, while part of As₂O₃ was oxidized to As₂O₅ by lattice oxygen. Finally, the generated As₂O₅ was successively trapped by CaO and Fe₂O₃ to form stable Ca₃(AsO₄)₂ and FeAsO₄. HRTEM and TEM analysis comprehensively proved that As(III) was stabilized by the lattice cage of CaAl₂Si₂O₈. In conclusion, the co-oxidation of Ca and Fe compounds and lattice stabilization simultaneously played a crucial role in the retention of As₂O₃(g) during co-gasification.

Keywords: Arsenic; Ca/Fe compounds; Co-gasification; Sewage sludge; Stabilization mechanism.